Shipboard Electronic Equipments

DOCUMENT RESUME

ED 070 576 SE 014 123

TITLE Shipboard Electronic Equipments.INSTITUTION Bureau of Naval Personnel, Washington, D. C.; Naval

Personnel Program Support Activity, Washington, D.C.

REP(1°T NO NAVPERS-10794-CPUB DATE 69NOTE 231p. .

EDRS PRICE MF-$0.65 HC-$9.87DESCRIPTORS Digital Computers; *Electronic Equipment;

Instructional Materials; *Military Scimce; *MilitaryTraining; Navigation; Physics; *Post SecondaryEducation; Radar; *Supplementary Textbooks

ABSTRACTFundamentals of major electronic equipments on board

ships are presented in this text prepared for naval officers ingeneral. Basic radio principles are discussed in connection withvarious types of transmitters, receivers, antennas, couplers,transfer panels, remote-control units, frequency standard equipments,teletypewriters, and facsimile installations. Theoretical andpractical analyses are made of radar and sonar equipmentS to showtheir capabilities and limitations. On the subject of electronicnavigation, loran, shoran, omega, tacan, and satellite and ships'inertial navigation systems are presented. Also included aredescriptions of digital computers, gun and missile weapon systems,direction finders, closed-circuit television sets, electroniccountermeasures, communication console equipments, underwatertelephones, intrared and meteorological setups, carrier controlapproach systems, radiac instruments, and target controlinstallations. Illustrations for explanation purposes and a glossaryof general terms are included. (CC)

IIIPBPARD

ELECTRONIC EQUIPMENTS.J/

Prepared by

BUREAU OF NAVAL PERSONNEL

NAYPERS 10794-C

PREFACE

This text has been prepared to furnish naval officers who are notelectronic specialists with an overview (1) of the fundamental concepts ofmajor electronic equipments on board ships of the U.S. Navy, and (2) of thecapabilities and limitations of the more common equipments installed inthe categories of communications, radar, sotil:.r, and navigational aids.

In view of the objectives of the text, technical details of circuitsand of components of equipments have been kept to a minimum. Overalltechnical aspects of the systems have been covered in sufficient detail,however, so that students can acquire familiarity with the purposes,functions, and types of equipment.

This text was prepared by the Training Publications Division,Naval Personnel Program Support Activity, Washington, D.C., for theBureau of Naval Personnel. Technical assistance was provided by theFleet Anti-Air Warfare Training Center, San Diego, California; NavalAir Technical Training Center, Glynco, Georgia; Naval ElectronicSystems Command, and Naval Ship Systems Command, Washington, DC.

UNITED STATESGOVERNMENT PRINTING OFFICE

WASHINGTON: 1969

Stock Ordering No.0500-212-1100

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THE UNITED STATES NAVY

GUARDIAN OF OUR COUNTRYThe United States Navy is responsible for maintaining control of the seaand is a ready force on watch at home and overseas, capable of strongaction to preserve the peace or of instant offensive action to win in war.

It is upon the maintenance of this control that our ccuntry's gloriousfuture depends; the United States Navy exists to make it so.

WE SERVE WITH HONOR

Tradition, valor, and victory are the Navy's heritage from the past. Tothese may be added dedication, discipline, and vigilance as the watchWordsof the present and the future.

At home or on distant stations we serve with pride, confident in the respectof our country, our shipmates, and our families.

Our responsibilities sober us; our adversities strengthen us.

Service to God and Country is our special privilege. We serve with honor.

THE FUTURE OF.THE NAVYThe Navy will always employ new weapons, new techniques, andgreater power to protect and defend the United States on the sea, underthe sea, and in the air.

Now and in the future, control of the sea gives the United States hergreatest advantage for the maintenance of peace and for victory in war.

Mobility, surprise, dispersal, and offensive power are the keynotes ofthe new Navy. The roots of the Navy lie in a strong belief in thefuture, in continued dedication to our tasks, and in reflection on ourheritage from the past.

Never have our opportunities and our responsibilities been greater.

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CONTENTS

CHAPTER Page

1. Nomenclature and Glossary 1

2. Radio 17

3. Radio Equipment 29

4. Teletype and Facsimile 66

5. Radar 87

6. Radar Equipment 105

7. Sonar 125

8. Sonar Equipment 136

9. Electronic Navigational Aids 151

10. Introduction to Digital Computers 173

11. Introduction to a Shipboard Weapons Control System 193

12. Miscellaneous Facilities 207

INDEX 224

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CHAPTER 1

NOMENCLATURE AND GLOSSARY

As in any technical or specialist field,many of the special words, phrases, terms,and symbols used in electronics are unfamil-iar to the average person. To assist you infollowing the material presented in the ensuingchapters, this chapter is devoted to a descrip-tion of equipment indentification systems (no-menclature designations) and to a glossary ofcommon electronic terms and symbols.

JOINT ELECTRONIC TYPEDESIGNATION SYSTEM

Electronic equipments and units are iden-tified in the Joint Electronics Type DesignationSystem (AN System) which is administeredunder the authority of the Armed Forces SupplySupport Center.

The Electronic Type Designator System forelectronic equipment is intended to:

1. Be logical in principle so that the no-menclature type numbers will be understoodreadily, and the operation of the armed serv-ices supply services will be facilitated.

2. Be flexible and sufficiently broad inscope to cover present types of .equipment, aswell as new types and uses of equipment thatwill be developed in the future.

3. Avoid conflict with nomenclature assignedat present to the equipment used by the ArmedServices.

4. Furnish adequate identification on nameplate with or without the name part of thenomenclature.

5. Provide a ready means of identifyingequipment in correspondence and other typesof communications.

The system is so designed that its indi-cators reveal at a glance many details thatpertain to the item. For example, it tells

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whether the item is a SET or a UNIT, andsuch other information as where it is used,what type equipment it is, and what it is usedfor.

AN nomenclature consists of an approvedname followed by the type number. For acomplete set, the type number will consist ofthree indicator letters and an assigned number.

Using this system of identification, the in-stallation type, the type of equipment, and thepurpose of each equipment and unit can bereadily determined. The derivation and mean-ing of the numenclahire for a representativeequipment (Communications Central AN/SRC-16) is delineated in figure 1-1.

In the three letter group (fig. 1-1A and B)the first letter "S," designates the type ofinstallation, i.e., "Water Surface (See table1-1.)" The second letter "R" designates thetype of equipment, in this case "Radio." Thethird letter "C" defines the purpose of theequipment as "Communications."

The number (type number) immediately fol-lowing the three letter group identifies a par-ticular equipment and includes all of its mod-ifications as discussed below. The meaning ofany three letter group can be similarly inter-preted by referring to Table 1-1.

A modification letter is used to identify aset that has been modified, but which stillretains the basic design and is functionallyand electrically (power source is the same)interchangeable with the unmodified set (fig.1-1A). When the AN/SRC-16 is modified,it becomes the AN/SRC-16A; the "A" indi-cates the first modification. The next modifica-tion would be the AN/SRC-16B, and so on.

The parenthesis ( ) as shown in figure 1-1Ais used with the type number assignment toprovide a broader identification than that pro-vided by a type number alone. A series ofsets or units may be identified by the use ofone or more letters and/or numbers in the

SHIPBOARD ELECTRONIC EQUIPMENTS

AN SYSTEM. IDENTIFIESMAJOR ITEMS OF ELECTRONICEQUIPMENT AS SET, CENTRAL,OR SYSTEM.

TYPE OF INSTALLATION.

TYPE OF EQUIPMENT.

PURPOSE OF EQUIPMENT.

MODEL NUMBER. THE NUMBERASSIGNED TO A SPECIFICDESIGN.

AN/SRC-16 COMMUNICATIONS CENTRAL

- 16A A MODIFIED VERSION OFTHE EQUIPMENT.

- 16B THE NEXT MODIFICATION.

- 16() A GENERAL IDENTIFICATION.INCLUDES THE EQUIPMENTAND ALL ITS MODIFICATIONS.

- 16 (X11-1) EXPERIMENTAL VERSION.

-16 (V) VARIABLE GROUPING HAVINGA VARIABLE PARTS LIST.

-16 X CHANGE IN INPUT VOLTAGE ,PHASE OR FREQUENCY.

T -916 /SRC- 16 A COMPONENT OF THEAN/SRC - 16.

WATER SURFACE

RADIO

COMMUNICATIONS

AN/SRC-I6 COMMUNICATIONS CENTRAL

TRANSMITTER

THE NUMBERED CENTRAL TOWHICH AN DESIGNATION ISASSIGNED.

IDENTIFIES THE COMPONENT ASBELONGING TO THIS CENTRAL,

T-916/SRC-16 RADIO TRANSMITTER

120.60Figure 1-1.Joint Electronic Type DesignationSystem for nomenclature AN/SRC-16Communications Central.

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parenthesis after the identifying number. Forexample, the AN/SRC-16 (XN-1) designates anexperimental or special model. If the samebasic design of an equipment is kept, but theinput power is changed from 110 volts to 220volts, the letter "X" .3 added to the nomencla-ture so that it becomes the AN/SRC-16X. Thesecond power input change would be identifiedby the letter "Y". The letter (V) within theparenthesis is used to identify systems withvarying parts lists. It indicates that a setutilizes or can utilize a variable grouping orselection of units thereby making possible op-tional installations.

The letter (T) is used for training sets.It is used in conjunction with the other indica-tors to show that it is a training set for aspecific equipment. Likewise, it may be usedto indicate a trainer for a special family ofequipment. For example, the first training setfor the AN/SRC-16 would be the AN/SRC-16T1.

COMPONENT IDENTIFICATION

So far, consideration has been given onlyto the indicators used in set nomenclature.Now, let's examine the indicators for majorcomponents of a set.

Components are identified by means ofindicating letters, which tell the type of com-ponent it is; a number, which identifies theparticular component; and, finally, the designa-tion of the equipment of which it is a part orwith which it is used.

The transmitter for the AN/SRC-16 forexample, would be identified as shown in (fig.1 -1C).

A modification letter identifies a compo-nent that has been modified but still retainsthe basic design and is interchangeable phys-ically, electrically, and mechanically with themodified item. Thus, the T-916(A)/SRC-16would be a modified version of the T-916/SRC -16.

Components that are part of or used withtwo or more sets are identified in the usualway, except that only those indicators thatare appropriate and without a set model num-ber appear after the slant bar.

RADIO OPERATING POSITIONSAND REMOTES

Table 1-2 shows the alphabet for radio op-erating positions and remotes.

Chapter 1NOMENCLATURE AND GLOSSARY

Table 1-1.Table of Equipment Indicator Letters.

FIRST LETTER(DESIGNED INSTALLATION CLASSES)

SECOND LETTER(TYPE OF EQUIPMENT)

THIRD LETTER(PURPOSE)

A - Piloted aircraft A - Invisible light, heat radiotion A - Auxiliary ossemblies (not complete8 - Pigeon (do not use) operating se's used with or port of two

B - Underwater mobile, submarine C - Carrier or more sets or sets series)D - Radioc B - Bombing

C - Air transportable (inactivated, do E - Nupac C - Communications (receiving andnot use) F - Photographic transmitting)

:' - Pilotless carrierG- Telegraph or teletypeI - Interphone and public address

D - Direction finder, reconnaissance,and/or surveillance

J - Electromechanical or Inertial wire j E - Ejection and /or releaseF - Fixed ground covered G- Fire-control, or searchlight directing

G- General ground useK - TelemeteringL - Countermeasures

H - Recording and/or reproducing (graphic,meteorological and sound)

M - Meteorological K - ComputingK - Amphibious N - Sound in air L - Searchlight control (inactivated, use G)

P - Radar M- Maintenance and/or test assembliesM- Ground, mobile 0 - Sonar and underwater sound (including tools)

P - PortableR - RadioS - Special types, magnetic, etc., or

combinations of types

N - Navigational aids (including altimeters,beacons, compasses, racons, depth,sounding, approach, and landing)

S - Water surface T - Telephone (wire) P - Reproducing (inactivated, use H)V - Visual and visible light 0 - Special, or combination of purposes

T - Ground, transportable

U - General utility

W- Armament (peculiar to armament,not otherwise covered)

X - Facsimile or television

R - Receiving, passive detectingS - Detecting and/or range and bearing,

searchY - Data processing T - Transmitting

V - Ground, vehicular W- Automatic flight or remote controlX - Identification and recognition

W- Water surface and underwatercombination

Table 1-2.Alphabet for Radio Operating Positions and Remotes.

Radio Radio

Alphabet Position & Remotes Alphabet Position & Remotes

ACDEFGHJLM

AudioControlDataEmergencyFacsimileTelegraphRadiophonePanelLocalMonitor

NoPQRSTUVX

ChannelOperatingPositionSecureRemoteStationTeletypeUnitSupervisorExtension

Examples of position designations are:LOP: Local Operating PositionLTP: Local Teletype PositionRHS: Remote Radiophone StationRDP: Remote Data Position

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120.61


GLOSSARY OF COMMONELECTRONIC TERMS

You doubtless are familiar with some of theterms listed in this glossary. It is not ex-pected, however, that you will know all of theterms used with operational electronics. Ac-cordingly, a study of these terms should con-tribute to a better understanding of the infor-mation contained in this text.3-M: Maintenance and Material Management.

A planned maintenance system concept andapplication.

ACCELEROMETEP: An inertial device. Aninstrument for sensing a change in velocitysuch as the increase in the speed of anobject.

ADP: Automatic data processing: (See below)AEW: Airborne early warning. A planned

radar system between surface ship and air-craft for long-range detection and identifi-cation used near the periphery of a defendedarea.

AF: Audiofrequency. (See below)A FTSRATT: Audiofrequency tone shift radio-

teletype. A radioteletype tone-modulatedsystem similar to the familiar AM radiomethod of broadcasting. It replaces the termfrequency shift keying.

ALIGN: To adjust the tuned circuits of atransmitter or receiver for proper signalresponse.

ALPHA PARTICLES: Positively charged par-ticles (helium nucleus) having great ionizingpower but very little penetrating power, andare dangerous to living tissue.

AM: Amplitude modulation: (See below)AMBIENT NOISE: The overall noise energy

from all environmental sources. In sonarit is the background noise inherent in the seaand collectively designated ambient noise.

AM COMPATABLE: Used in conjunction withSSB (single side band) where the amplitudemodulated carrier wave and either the upperside band or the lower side band carriesthe intelligence.

AMMETER: An instrument for measuring theelectron flow in amperes.

AMPERE: The basic unit of current flow; acurrent of 1 ampere will flow through aconductor having a resistance of 1 ohm whena potential of 1 volt is applied.

AMPLIFICATION: The process of increasing thestrength (voltage, current, or power of asignal).

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AMPLIFIC ATION FACTOR (p): The ratio of asmall change in plate voltage to a smallchange in grid voltage, with all other elec-trode voltage constant, required to producethe same small change in plate current.

AMPLIFIER: A device for increasing the signalvoltage, current, or power without ap-preciably altering its quality; gene rally madeup of an electron tube or transistor andan associated circuit called a stage. Theamplifier may contain several stages inorder to obtain a desired gain.

AMPLITUDE DISTORTION: The undesiredchange of a waveshape so that it no longeris proportional to its original form.

AMPLITUDE MODULATION: Changing the am-plitude of a radiofrequency carrier wave inaccordance with the variations of an audio-frequency wave.

ANALOG COMPUTER: A computer which solvesproblems by translating physical conditionssuch as flow, temperature, pressure, orvoltage into electrical equivalent circuits andproducing numbers as outputs.

ANODE: A positive electrode; the plate of avacuum tube.

ANTENNA: Also aerial. A conductor or systemof conductors that radiates or interceptsenergy in the form of electromagnetic waves.

ANTENNA REFLECTOR: That portion of a di-rectional antenna array which changes thedirection of radiant energy behind the arrayand increases it in the forward direction.

ANTIJAMMING: A function of a radar set toreduce or eliminate enemy jamming of elec-tromagnetic waves which are hindering theusefullness of specific segments of the radiospectrum.

ARRAY: Radio:-A combination of antenna ele-ments arranged to reinforce the performanceof the other and used where signal gain bydirection is required. Computer:-A seriesof items arranged in a meaningful pattern.

ASW: Antisubmarine warfare.ATTENUATION: The reduction in strength of a

signal. The amount of attenuation is usuallyexpressed in decibels.

AUDIO COMPONENT: That portion of any waveor signal whose frequencies are within theaudio range.

AUDIOFREQUENCY: A frequency that can bedetected as a sound by the human ear. Therange of audiofrequencies extends from 20to 20,000 hertz.


AUTOMATIC DATA PROCESSING: The pro-cessing of data automatically by means ofa machine in which the internal interactingassemblies of procedures, processes, andmethods perform a complex series of com-puter operations.

AUTOMATIC DIRECTION FINDER: An auto-matic radio compass which automaticallyaims a directional antenna to show thedirection of location of a transmitter.

AUTOMATIC GAIN CONTROL: A method ofautomatically regulating the gain of a re-ceiver so that the output tends to remainconstant though the incoming signal mryvary in strength.

AZIMUTH: An angle measured clockwise fromtrue north. Azimuth and bearing are us-ually used synonymously. (See bearing)

BALANCED CIRCUIT: A divided circuit in whichboth sides are electrically equal.

BAND: The radio frequencies existing betweentwo definite limits and used for a definitepurpose. Example: Standardbroadcast bandextending from 550 to 1600 kHz.

BANDPASS FILTER: A circuit designed topass currents of frequencies within a definitefrequency band with nearly equal response,and to reduce substantially the amplitude ofcurrents of all frequencies outside that band.

BAND SPREAD: Any method of spreading tun-ing over a greater range to facilitate tuningin a crowded band of frequencies.

BANDWIDTH: The total frequency width of achannel or band of frequencies.

BATHYTHERMOGRAPH: A recording ther-mometer for obtaining a permanent graphicalrecord of water temperature in degreesfahrenheit at different water depths in feetas it is lowered or dropped into the ocean.

BEACON: Compared to a lighthouse. A radioor radar signal station which provides navi-gation and interrogation information forships and aircraft.

BEARING: The angular position of an objectwith respect to a reference point or line.If the reference point is true north, thebear-ing is the true bearing; if the reference isNOT true north, the bearing is a relativebearing. (See azimuth)

BEAT FREQUENCY: One of the two additionalfrequencies obtained when signals of twodifferent frequencies are combined. Theirvalues are equal to the sum and dif-ference, respectively, of the original fre-quencies.

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BEAT FREQUENCY OSCILLATOR: An oscil-lator in which an audile beat frequency isobtained by mixing or beating together tworadiofrequencies. The BFO is used forcontinuous wave (CW) reception in super-heterodyne receivers, or as an instrumentfor test purposes.

BEAT NOTE: The audiofrequency produced bybeating together two different frequencies.

BETA PARTICLES: High speed electrons thatwill travel several feet in air and are dan-gerous to living tissue.

BIAS: The DC voltage or current applied to acircuit to establish the deSired electricaloperating point.

BIASING RESISTOR: A resistor used to pro-vide the voltage drop for a required bias.

BILLBOARD or BEDSPRING ARRAY: A broad-side radar antenna array consisting ofstacked dipoles in front of a large flatsheet-metal untuned reflector.

BIT: Binary digit: A single electrical pulse,a character, or unit of information usedas the basic intelligence in a binary system.

BLEEDER: A resistance connected in parallelwith a power-supply output to protect equip-ment from excessive voltages if the loadis removed or substantially reduced; toimprove the voltage regulation, and to drainthe charge remaining in the filter capaci-tors when the unit is turned off.

BOTTOM BOUNCE: That form of sonar soundtransmission in which sound rays strikethe ocean bottom in deep water at steepangles and are reflected back to the surfaceand returned, which allows the obtaining oftarget information at long distances.

BREAKDOWN VOLTAGE: The voltage at whichan insulator or dielectric ruptures; or thevoltage at which ionization and conductionbegin in a gas or vapor tube.

BT: Bathythermograph (see above).BUFFER: Isolated circuitry inserted between

two noncompatible circuits to make themcompatible with each other. Also a storagedevice used to allow for differences in ratesof data flow when transmitting informationfrom one computer device to another.

BYPASS CAPACITOR: A capacitor I sed toprovide an alternating current path of com-paratively low impedance around a circuitelement.

CAPACITOR: Two electrodes or sets of elec-trodes in the form of plates, separated fromeach other by an insulating material called


the dielectric. The capacitor has the propertyof storing electrical energy in an electro-static field between the electrode plates.

CARRIER: The frequency of an unmodulatedRF transmitted wave. The RF componentof a transmitted wave upon which an audiosignal or other form of intelligence can beimpressed.

CATHODE FOLLOWER: A vacuum-tube cir-cuit in which the input signal is appliedbetween the control grid and ground, andthe output is taken from the cathode andground. A cathode follower has a high inputimpedance and a low output impedance.

CCA: Carrier control approach. Providesa radar system for guiding aircraft to safedeck landings during night flying or underconditions approaching zero visibility.

CCM: Counter countermeasures. Measurestaken to reduce the effect of enemy jammingon our own electronic equipment.

CATHODE: The electrode in a vacuum tube thatprovides electron emission.

CAVITATION: The separation between theship's propeller blades and the surroundingwater caused by the propeller turning sorapidly that the water does not have timeto close in behind the blades thus producinga stream of bubbles. The abrupt collapseof the bubbles causes the acoustic signalknown as cavitation. Sonar can often de-termine the class of ships by their cavi-tation.

CHANNEL: A narrow band of frequencies in-cluding the assigned carrier frequency, with-in which a radio or TV station is requiredto keep its signals within.

CHONOMETER: A time piece with a nearlyconstant rate having extremely great ac-curacy.

CLOSED CIRCUIT TELEVISION: The appli-cation of television where reception is con-fined locally and not for broadcasting. Thereceivers are connected to the televisioncamera by coaxial cables. The system isused chiefly aboard ship for pilot's landingaid television (PLAT) system and crewentertainment.

COAXIAL CABLE: A transmission line con-sisting of one conductor, usually a smallcopper tube or wire, within and insulatedfrom another conductor of larger diameter,usually copper tubing braid. The outer con-ductor may or may not be grounded. Radia-tion from this type of line is practically

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zero. Coaxial cable sometimes is calledconcentric line.

CODE: A system of dots and dashes fortransmission of mess2ges.

CONDUCTANCE: The ability of a material toconduct or carry an electric current. It isthe reciprocal (opposite) of the resistanceof the material and is expressed in mhos.

CONTINUOUS WAVES: Radio waves that main-tain a constant amplitude and a constartfrequency.

CONVERGENCE ZONE: That region in the deepocean where sound transmissions directeddownward refract from the depths a.nd arriveat the surface in successive intervals of30 to 35 miles. This sound channel canpermit ships to detect targets at long dis-tances.

CONVERSION: A term applied to the sec-tion(s) of a superheterodyne receiver thatconverts the desired incoming R F signalsto desired IF values to lower the frequency.This may be accomplished in ONE, TWO,or THREE stages known as SINGLE,DOUBLE, or TRIPLE conversion (sometimesreferred to as stages in DETECTION, orHETERODYNING).

COUNTERMEASURES: (see ECM)COUNTERPOISE: A conductor or system of

conductors used as a substitute for groundin an antenna system.

CROSS MODULATION: A type of crosstalk inwhich the modulated carrier frequency be-ing received is interfered with by an ad-jacent modulated carrier, so that the modu-lated signals of both are heard at the sametime.

CROSSTALK: Refers to an unwanted signalwhich may appear on one channel due to therecording on the adjacent channel, or to anundesired coupling with another communi-cation channel.

CRT: Cathode-ray tube, An electron-beam tithein which the beam can be focused to a smallcross section on a phosphorescent screen andvaried in position and intensity to producea visible pattern.

CRYPTOGRAPH: The art of writing in secretcode. Rendering a plain text unintelligibleto those who are not informed of the code.

CRYSTAL: A natural substance as quartz ortourmaline capable of producing a voltagewhen under stress or pressdre, or producingpressure when under an applied voltage.Under stress, it has the property of

Chapter 1NOMENCLATURE AND GLOSSARYaa

responding only to a given frequency whencut to a given thickness. It is thereforevaluable for transmitters or osWlatorswhose frequencies range between 500 kHzand 10 MHz.

CRYSTAL CONTROL: Control of the frequencyof an oscillator by means of a speciallydesigned and cut crystal.

CRYSTAL OSCILLATOR: An oscillator circuitin which a crystal is used to control thefrequency and to reduce frequency instabil-ity to a minimum.

CURIE: The basic unit to describe the intensityof radioactivity in a sample of material.

CURRENT: The flow of free electrons, ex-pressed in amperes.

CURSOR: A clear or amber-colored filterplaced over an electronic marker, availableon a radar or control indicator screen andmanipulated to determine accurately thebearing of a target.

CW: Continuous wave (see above).CYCLE: One complete positive alteration and

one complete negative alteration of an alter-nating current or voltage.

DASH: Drome Antisubmarine helicopter. Anunmanned remote-controlled helicopter usedin dangerous areas for spotting targets withTV camera and other detection devices.The helicopter is capable of carrying twoASW torpedoes.

DB: Decibels. The unit for measuring therelative loudness of sounds. The unit isa value that expresses the comparison ofsounds of two different levels.

DEAD RECKONING ANALYZER: The deadreckoning analyzer receives the ship's speedin knots from the pit log, and the ship'scourse input from the master gyro. Thesetwo inputs are combined to determine andindicate the total distance traveled and alsothe overall distances in a north-south andeast-west direction travelet) by the shipfrom any starting point.

DEMODULATION: The process of extractingthe intelligence from the RF carrier, withwhich the carrier has been modulated.

DETECTOR CIRCUIT: Theportionof a receiverthat recovers the audible siznal from themodulated RF carrier wave.

DEVIATION: A term used in frequency modu-lation to indicate the amount (of frequency)by which the t.arrier or resting frequencyincreases or decreases when modulated. Itusually is expressed in k.: 'hertz.

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DEVIATION RATIO: A term used in frequencymodulation to indicate the ratio of the maxi-mum amount of deviation of a fully modulatedcarrier to the highest audiofrequency beingtransmitted.

DIELECTRIC: An insulator. A term appliedto the insulating material between the platesof a lapacitor.

DIGITAL COMPUTER: A type of calculatingmachine that operates with numbers ex-pressed directly as digits, generally usingbinary or decimal notation to solve extremelycomplex and involved mathematical prob-lems.

DIGITAL DATA TRANSMISSIONS: The RFtransmission of data from a computer inserial or parallel format of binary numbers.The radiofrequency transmission is usuallyby a series of pulse code modulations.

DIODE: A two-electrode vacuum tube con-taining a cathode and a plate.

DIPOLE ANTENNA: A cente r-fed one-half waveantenna.

DISTOIZTION: Distortion is said to exist whenan output waveform is not a true reproduc-tion of the input waveform. Distortion mayconsist of irregularities in amplitude, fre-quency, or phase.

DOPPLER EFFECT: The change in frequencyof sound, radio, or light waves reachinran observer, due to the differe..a. \ lati.motion of the source or observe', or both.It is the change in a received frequency be-cause of relative motion between transmitterand receiver.

DOSIMETER: A device that measures radia-tion dosage.

DRIVER: An amplifier used to excite the finalpower amplifier stage of a transmitter orreceiver.

DUPLEXER: An electronic switching devicewhich makes possible the use of one antennafor both transmitting and receiving.

EAM: Electrical accounting machine. The setof conventional punchcard equipment includ-ing sorters, collators, and tabulators.

ECM: Electronic countermeasures. Active-use of transmitting equipment that may jamthe enemy transmissions. Passive-use ofreceiver equipment to intercept enemy radaror radio transmissions.

EDP: Electronic data processing. Processingperformed largely by equipment using elec-tronic circuitry for storing and manipulatingdata. It is the interacting assembly of


methods, procedures, and electronic equip-ment.

EFFICIENCY: The ratio of output to input power,generally expressed as percentage.

ELECTRIC FIELD: A region in space in whichelectrified bodies are subjected to forcesacting upon them by virtue of their electri-fication.

ELECTRODE: A terminal at which electricitypasses from one medium into another.

ELECTROLYTE: A water solution of a sub-eta.nce which is capable of conducting elec-tricity. An electrolyte may be in the formof either a liquid or a paste.

ELECTROMAGNETIC WAVE: A wave of elec-tromagnetic radiation, characterized byvariations of electric and magnetic fidas.

ELECTRON: The most elementary charge ofelectricity. It is always negative.

ELECTRON EMISSION: The liberation of elec-trons from a body into space under the in-fluence of heat, light, impact, chemical dis-integration, or a potential difference.

ELECTROSTATIC FIELD: The field of influencebetween two charged bodies.

E LECTROSTRIC TION: That property of certainceramic materials which after having a per-manent operating bias established causesthese materials to vary slightly in lengthwhen they are placed in an electric field.

EMF: Electromotive force. An electrical forcethat produces an electrical current in a closedcircuit. Has the same meaning as voltage,potential difference, electrical pressure.

EMO: Electronic material officer.EXCITER: (see transmitter).FACSIMILE: Transmitting photographs, draw-

ings, handwriting, or printed matter over anelectronic communications system.

FADING: Variations in the strength of a radiosignal at the point of reception.

FAIL SAFE: A control so designed that acontrol circuit malfunction cannot cause adangerous condition under any circum-stance.

FARAD: The unit of capacitance.FATHOMETER: An instrument aboard ship

for determining depth of water by meas-uring the time that it takes the generatedsound emissions to reach bottom and returnas an echo.

FEEDBACK: A transfer of energy from theoutput circuit of a device back to its input.

FIDELITY: The degree of accuracy with whicha system, or portion of a system, reproduces

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in its output the signal impressed on itsinput.

FIELD: The space containing electric ormagnetic lines of force.

FILTER: A combination of resistances, in-ductances, and capacitances, or any one ortwo of these, which allows the comparativelyfree flow of certain frequencies or of directcurrent while blocking the passage of otherfrequencies. An example is the filter usedin a power supply, which allows the directcurrent to pass. but filters out the ACcomponent.

FIX: A determination of navigational positionusually the intersection of several lines-of-position or bearing lines.

FLIP FLOP: A bistable multivibrator. Fre-quently used in computer applications ascounters.

FM: Frequency modulated (see below).FREE ELECTRONS: Electrons that are not

bound to a particular atom, but move aboutcontinuously among the many atoms of asubstance.

FREQUENCY: The number of hertz (cyclesper second) of an alternating current.

FREQUENCY DIVERSITY: A method by whichtwo or more transmitters will transmitsimultaneously at two or more distinct fre-quency bands, and the reception is a singlesignal selected from a plurality of signals.This method reduces the effects of fading.It gives a greater effective range and reducesthe susceptibility to jamming.

FREQUENCY DIVISION MULTIPLEXING: Aprocess for the transmission of two or morechannels over a common path by using adifferent frequency band for each channel.(See MULTIPLEXING.)

FREQUENCY DOUBLER: An electronic circuitin which the output is tuned to twice thefrequency of the input.

FREQUENCY DRIFT: Change in a frequencyfrom its basic wavelength caused by tem-perature or component variations in thefrequency-determining elements.

FREQUENCY METER: A meter calibrated tomeasure frequency.

FREQUENCY MODULATION: The process ofvarying the frequency of an RF carrier wavein accordance with the frequency of an audiosignal. The amplitude of the modulatedwave stays essentially constant.


FREQUENCY MULTIPLIER: A frequency deviceused to multiply an original frequency byan integral value.

FREQUENCY STABILITY: The ability of anoscillator to maintain its operation at aconstant frequency.

FREQUENCY STANDARD: A stable low fre-quency oscillator used for frequency cali-brations. It usually generates a fundamentalfrequency of 50 to 100 kilohertz with a highdegree of accuracy and the harmonics ofthis fundamental are used to provide ref-erence points for checking (50 or 100 kilo-hertz apart) throughout the radio spectrum.

FULL-WAVE RECTIFIER CIRCUIT: A circuitwhich utilizes both the positive and the nega-tive alterations of an alternating current toproduce a direct current.

GAIN: The ratio of the output power, voltage,or current to the input power, voltage, orcurrent.

GAMMA RADIATION: High energy short-wavelength electromagnetic radiation with tre-mendous penetrating power, and is dangerousto living tissue.

GCA: Ground control approach. A talk-downmethod for landing an aircraft.

GHz: Giga hertz. Having a value of 1 billionhertz.

GIGA: A prefix indicating the value of onebillion (1,000,000,000).

GRAZING ANGLE: The angle that the soundray path forms with the reflecting surface;usually applies to sound rays reflected fromthe ocean bottom.

GROUND: A metallic connection with the earthto establish a common connecting point. Also,a common return to a point of zero potential.

GROUND PLANE ANTENNA: A vertical radioantenna combined with a turnstile elementto lower the angle of radiation, and havinga concentric base support and center con-ductor that together serve to place the an-tenna at ground potential even though it maybe located several wavelengths above ground.

GROUNDWAVE: That portion of the transmittedradio wave that travels near the surface ofthe earth.

HAND KEY: A switch used in communicationsto provide a mode of operation in whichtransmission is usually coded.

HARMONIC: An integral multiple of a funda-mental frequency. (The second harmonic istwice the frequency of the fundamental orfirst harmonic.)

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HEMISPHERICAL SCAN: Scanning one of twoequal parts of a sphere. Essentially aradio or radar scan of horizon-to-90 degreeoverhead, through 360° azimuth radiationpattern or sonar scan of horizon-to-90°ocean bottom, through 360° azimuth radiationpattern.

HENRY: The basic unit of inductance.HERTZ: A new term used for frequency meas-

urement replacing the old term cycles persecond.

HETERODYNE: To mix two alternating currentsof different frequencies in the same circuit;they are alternately additive and substrac-tive, thus producing two beat frequencies,which are the sum of and difference betweenthe two original frequencies.

HIGH FIDELITY: The ability to reproduce allaudiofrequencies between 50 and 16,000hertz without serious distortion.

HIGH-LEVEL MODULATION: Modulation pro-duced at a point in a system where thepower level approximates that at the outputof the system. Also called plate modulation.

HYDROPHONE: An acoustic device that re-ceives and converts underwater sound energyinto electrical energy.

HYPERBOLA: In a flat plane, is the locus ofa point which moves so that the differencebetween the distances from two fixed points(called the foci) is constant.

HYPERBOLOID OF REVOLUTION: The sur-face traced by a hyperbola rotating aboutone of its axes.

Hz: liertl. Replaces the old abbreviation cps.ICW: Interrupted continuous wave. Used for

morse code transmission.IF: Intermediate frequency. (see below).IFF: Identification friend or foe. A challenge

and an automatic response system developedfor use with radar equipment. A codedchallenging transmission, when received bya friendly craft will automatically transmita coded identification signal.

IMPEDANCE: The total opposition to currentflow in an AC circuit.

IMPULSE: Any force acting over a compara-tively short period of time. An examplewould be a momentary rise in voltage.

INERTIAL NAVIGATION: Dead reckoning per-formed automatically by a device which givesa continuous indication of position by com-bining vectors for speed, direction, andother factors since leaving a startingpoint.


IN PHASE: Applied to the condition that existswhen two waves of the same frequencypass through their maximum and minimumvalues like polarity at the same instant.

INPUT-OUTPUT EQUIPMENT: A device whichprovides the means of communication be-tween the computer and external equipment.The device accepts new data, sends it intothe computer for processing, receives theresults, and transforms the data into usableform.

INSTANTANEOUS VALUE: The magnitude atany particular instant when a value is con-tinually varying with respect to time.

INTELLIGENCE: The message or informationconveyed, as by a modulated radio wave.

INTENSITY: The relative strength of electric,magnetic, or vibrational energy.

INTERFACE: A concept involving the specifi-cation of the interconnection between twoequipments or systems. The specificationsinclude the type, quantity, and function ofsignals to be interchanged via those circuits.

INTERMEDIATE FREQUENCY: The fixed fre-quency to which all RF carrier waves areconverted in a superheterodyne receiver.

INTERNATIONAL MORSE CODE: The uni-versal code used for radio telegraphy. Itdiffers from the American Morse Code usedfor wire telegraphy, in the spacing and lettercodes.

ISB: Independent sidebands (two) (see SIDE-BANDS).

ISOTHERM: Having no temperature changes inwater from surface to varying depths.

ION: An atom that has lost or gained one ormore electrons and is therefore positivelyor negatively charged.

IONIZATION: The breaking up of atoms intoions.

IONOSPHERE: Highly ionized layers of at-mosphere from between 40 and 350 milesabove the surface of the earth.

KHz: Kilohertz. Having a value of one thousand(1,000 or 1a) hertz.

KILO: A prefix meaning one thousand.KLYSTRON TUBES: A velocity-modulated ther-

mionic tube for microwave operation.LEAKAGE: The electrical loss due to poor

insulation.LINEAR: The relationship of two related quan-

tities such that a change in one will resultin the exact proportional change in the other.A system in which the output varies indirectproportion to the input.

10

LOCAL-REMOTE CONTROL: A switch usuallymounted on an instrument control panel ofa unit and permits the operation of the sys-tem locally (near the panel) or remotely(at some distant place).

LOF: Line of fire. A straight line joiningmissile cr gun and point of impact (orburst)of the missile or projectile.

LONG RANGE: A radio distance of over1,500 iniles.

LOOP ANTENNA: One or more complete turnsof wire used with a radio receiver. Alsoused with direction-finding equipment.

LORAN: Long range navigation. An electronicnavigational system with high frequency re-ceive rs and scope indicators in which mathe-matical hyperbolic lines of position are de-termined by measuring the difference in thetime of reception of synchronized pulsesignals.

LOS: Line of sight. The straight-line dis-tance from ship to horizon. Representsradio and radar VHF and UHF transmissionrange limits under normal conditions.

LOUDSPEAKER: A device that converts AFelectrical energy to sound energy.

LOW-LEVEL MODULATION: Modulation pro-duced at a point in a system where the powerlevel is low compared with the power levelat the output of the system.

LSB: Lower sideband. (See SIDEBANDS.)MAGNETIC FIELD: The region in space in

which a magnetic force exists, caused by apermanent magnetic, or as a result ofcurrent flowing in a conductor.

MAGNETIC HEAD: A transducer in a taperecorder which converts the electrical sig-nals into magnetic fields for establishing themagnetic pattern on the tape.

MAGNETOSTRICTION: That property of certainferro type materials which causes them tovary slightly in length when they are in analternating magnetic field.

MAGNETRON: A special microwave oscillatortube which produces an AC output for radioand radar high power transmitters.

MARK AND SPACE: Pertaining to telegraphcommunications in which the marking in-tervals are the intervals which correspondto one condition or position of transmission,usually a closed condition. Spacings arethe intervals which correspond to anothercondition of the transmission. usually an opencondition.

Chapter 1 NOMENCLATURE AND GLOSSARY

MATCHED IMPEDANCE: The condition whichexists when two coupled circuits are soadjusted that their impedances are equal.

MCW: Modulated continuous wave. A formof transmission in which the carrier waveis modulated by a constant AF tone.

MEG OR MEGA: A prefix indicating onemillion.

MHO: The unit of conductance.MHz: Megahertz. Having a value of 1,000,000

or 1158 hertz.MICROPHONE: A device for converting sound

energy into AF electrical energy.MICROSECOND: Abbreviated (p sec). A time

measurement having a value of one mil-lionth (.000001 or 10-6) of a second.

MILLISECOND: Abbreviated (m sec). A timemeasurement having a value of one thou-sandth (.001 or 10-3) of a second.

MTI: Moving target indicator. A radar sys-tem providing improved target discrimina-tion against clutter from sea or shore re-turn. Detects moving targets in the presenceof obscuring echos which otherwise wouldbe obscured.

MK: MARK. A designation followed by aserial number to identify equipment of aparticular military design (usually or-dnance). This MARK number is furtherextended by a MOD number(s) when equip-ment of this design has been modified.

MODULATED CARRIER: An RF carrier whoseamplitude or frequency has been ,aried inaccordance with the intelligence to be con-veyed.

MODULATION: The process of varying theamplitude or the frequency of a carriersignal (RF output of the transmitter) atthe rate of an audio signal. The modulat-ing signal may be an audiofrequency signal,video signal (as in television), or evenelectrical pulses or tones.

MODULATOR: That part of a transmitter thatsupplies the modulating signal to the modu-lated circuit, where it can act upon thecarrier wave.

MODULE: A technique of compact packagingelectronic circuitry and components of anindividual subsystem to be used in com-bination with other packaged subsystemsto form a complete electronic system. Thisis a great aid in diagnostic maintenanceof the equipment.

MULTICOUPLER: An antenna permitting si-multaneous operation of several trans-

11

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mitters and/or receivers from the sameantenna.

MULTIPLEXING: A system to increase themessage-handling capacity of RF channelsby simultaneous transmission of two or moresignals using a common carrier wave.

NAUTICAL MILE: Equals 6,080 feet. Anelectromagnetic signal will travel a nauticalmile in 6.18 microseconds.

NETWORK: Any electrical circuit containingtwo or more interconnected elements.

NIXIE TUBE: A radio tube capable of formingthe ten different numerals (zero throughnine) for digital readouts.

NTDS: Naval tactical data system. An auto-matic data processing system for combatships within a fleet task force. The net-work is basically ship and airborne datalinks in communications and weapons sys-tems.

OFF-LINE EQUIPMENT: Peripheral computerequipment which can operate independentlyof the main computer for such operations astranscribing punchcard information to mag-netic tape, or magnetic tape to printed form.

OHM: The unit of electrical resistance.OHM'S LAW: A fundamental law of electricity.

It expresses the definite relationship exist-ing between the voltage E, the current I,and the resistance R, the common form forwhich is E = IR.

OMNIDIRECTIONAL: Going out in all direc-tions as the radiation pattern of a singledipole antenna.

ON-LINE EQUIPMENT: Main computer equip-ment, due to configuration or design, thatrequires the use of the central processingunit of the computer.

OPEN CIRCUIT: A circuit which does notprovide a complete path for the flow ofcurrent.

OSCILLATOR: A generator of radiofrequencywaves.

OSCILLOSCOPE: An instrument for showingvisually on a cathode ray tube represen-tations of the waveforms encountered inelectrical circuits.

OUTPUT: The energy delivered by a deviceor circuit such as a radio receiver ortransmitter.

OVERLOAD: A load greater than the ratedload of an electrical device.

OVERMODULATION: More than 100 percentmodulation. In amplitude modulation, overmodulation produces positive peaks of more


than twice the carrier's original amplitude,and brings about complete stoppage of thecarrier on negative peaks, thus causingdistortion.

PA: Power amplifier. The last stage of RFamplification in a transmitter or otherappropriate equipment.

PARABOLIC REFLECTOR: A dish reflectorwhose section is a parabola and capableof reflecting waves in parallel when aradiated wave source is placed at its focus.

PASSIVE: Involves the natural radiation orreflection of energy given off by an object.Passive electronic equipments are designedfor detection of objects.

PATCH CORDS: A cord equipped with plugsat each end for receiving jacks and usedto connect transmitter and receiver trans-fer panels to remote control points locatedtin oughout the ship.

PATCH PANEL: A board where circuits areterminated in jacks for temporary connec-tions to electric cords for communications.

PEAK VALUE: The maximum instantaneousvalue of a varying current, voltage, or power.It is equal to 1.414 times the effectivevalue of a sine wave.

PERCENTAGE OF MODULATION: A measureof the degree of change in a carrier wavecaused by the modulating signal, expressedas a percentage.

PERIPHERAL EQUIPMENT: Either on-lineor off-line auxiliary equipment supportingthe operations but is not a part of thecomputer itself. These machines may con-sist of card readers, cardpunches, magnetictape feeds, and high speed printers.

PHASE DIFFERENCE: The time in electricaldegrees by which one wave leads or lagsanother.

PIEZOELECTRIC EFFECT: Effect of produc-ing a voltage by placing a stress, either bycompression, expansion, or twisting, on acrystal and, conversely, producing a stressin a crystal by applying a voltage to it.

PIPS: Popular term for bright spots on aCRT display such as a radar or sonarscreen.

PLATE: The principal electrode in a tubeto which the electron stream is attracted.See Anode.

POTENTIOMETER: A variable voltage divider.A resistor that has a variable contact armso that any portion of the potential appliedbetween its ends may be obtained.

12

POWER: The rate of doing work or the rateof expending energy. The unit of electricalpower is the watt.

POWER TUBE: A vacuum tube designed tohandle a greater amount of power than theordinary voltage-amplifying tube.

PPI: Planned position indicator. A type ofradar or sonar scope display in which asweep rotates radically across the screento indicate position of targets simultaneouslythrough 360 degrees.

PRECESSION: Change in the direction of theaxis-of-rotation of a spinning body as agyroscope, when acted upon by a torque.

PRINTED CIRCUIT BOARD: An insulatingboard method of connecting electrical cir-cuits on a plane surface with conductive andresistive materials.

PROGRAM: A complete plan for the solutionof a problem, including the complete se-quence of machine instructions and routinesnecessary to solve the problem by an elec-tronic computer.

PULSATING CURRENT: A direct current whichperiodically increases and decreases invalue.

PULSE: A momentary sharp surge of electricalvoltage or current.

PULSE-DOPPLER: Combines the best featuresof continuous wave and pulse radar. Thepulse-doppler method is used principallyto obtain information about a target by usinghigh frequency continuous waves in the formof short burst or pulses.

PULSE DURATION: The time interval betweenthe points on the leading and trailing edgesat which the instantaneous values bears aspecific relation to the peak pulse amplitude.

PULSE INTERVAL: The time interval betweenthe leading edges of successive pulses in asequence characterized by uniform spacing.

PULSE LENGTH: Same as Pulse Duration.PULSE MODULATION: The forming of very

short bursts of a carrier wave separatedby relatively long periods during which nocarrier wave is transmitted.

PULSE REPETITION RATE: The rate at whichthe recurring pulses are transmitted, usuallyexpressed in pulses per second.

PULSE SEPARATION: The time interval be-tween the trailing edge of one pulse and theleading edge of the next pulse.

PULSE SPACING: Same as PULSE INTERVAL.PULSE TRAIN: A group of related pulses,

constituting a series.

Chter 1NOMENCLATURE AND GLOSSARY

PULSE WIDTH: Same as PULSE DURATION.RAD: An unit of absorbed dosage of nuclear

radiation.RADAR: Radio detection and ranging. A radio

echo device for detecting and tracking shipsand aircraft and other material targets.

RADIO: The science of communication inwhich radiofrequency waves are used tocarry intelligence through space. A generalterm denoting radio waves transmission andreception, exclusive of specialized systemssuch as facsimile of television, and radarwhich employ radio principles but are com-monly known by other terms.

RADIOACTIVITY: The emission by the un-stable nucleus of particles or by electro-magnetic waves as alpha, beta, or gammaradiation.

RADIO CHANNEL: A band of adjaCent fre-quencies of a width sufficient to permit itsuse for radio communication.

RADIO DIRECTION FINDER: A receiver and arotatable loop antenna used principally tolocate personnel afloat on life rafts and lifeboats equipped with radio transmitters.

RADIOFACSIMILE: The transmission of stillimages (weather maps, photographs,sketches, typewritten pages, etc.) over aradiofrequency channel.

RADIOFREQUENCY: Any frequency of elec-trical energy capable of radiating great dis-tances into space. Basically, these fre-quencies occupy the frequency spectrum be-tween audio sound and infrared light.

RADIOSONDE: An instrument carried aloft byan unmanned balloon and equipped withelements for determining temperature, pres-sure, and relative humidity at regular in-tervals during the ascent by automaticallytransmitting the measurements backto earthby radio for recording. A parachute lowersthe equipment earthward when the balloonbursts.

RADIOTELEPHONY: Two-way voice communi-cations conducted by means of radiofre-quency waves.

RADIOTELETYPE: The transmission of mes-sages from a teletypewriter or coded tapeover a radiofrequency channel by means ofcoded combinations of mark and space im-pulses.

RADIO CHANNEL: A band of adjacent fre-quencies of a width sufficient to permitradio communication. Channel width de-pends on the type of transmission and

the tolerance for the frequency of emis-sion.

RADIO WAVES: The electromagnetic radiationscaused by oscillation of electric chargescapable of traveling through space at thespeed of light.

RCVR: An abbreviation for receiver.RDT: Rotating directional transmission. Equip-

ment used in radar and sonar to concentratethe total power into a directional transmis-sion beam that covers a narrow sector asit rotates 360 degrees in azimuth.

REAL TIME: Computer operation with regardto the time interval between the inquiryfor information and the delivery of infor-mation to and from the computer (virtuallyzero time).

REFLECTION: The turning back of a radiowave from the surface of the earth or theionosphere.

REFRACTION: The bending or change in thedirection of a wave in passing from onemedium into another. This effect will turn

radio wave back to earth if the angle ofattack is not too great, and it will bend asound wave in sonar ranging as the wavepasses from one layer of water to another.

RELATIVE BEARING: A bearing taken whenthe heading of a ship serves as the ref-erence line.

REPEATERS: Radar or sonar indicators.RE PER FORATOR: A machine that automatically

punches or perforates tape to record themessage being sent or received by the radioteletype machine. May be used to perforatetapes for original outgoing messages or fortaping incoming messages for later retrans-mission.

RESONANCE: The condition existing in a cir-cuit when the values of inductance, capaci-tance, and the applied frequency are suchthat the inductive reactance and capacitivereactance cancel each other.

RESTING FREQUENCY: The initial frequencyof the carrier wave of an FM transmitterbefore modulation. Also called the centerfrequency.

REVERBERATION: A succession of echoscaused by reflections of sounds. In theocean it is caused by irregularities in theocean bottom, surface, and suspendedmatter (as fish). Under these con-ditions an emitted pulse may be re-ceived as a muffed echo due to soundinterference.

13

7


RFCSRATT: Radio frequency carrier shiftradioteletype. A radioteletype frequencyshift system similar to the familiar FMradio method of broadcasting. It replacesthe term frequency shift keying.

RHEOSTAT: A variable resistor, usually asso-ciated with power devices.

RHI: Range-height indicators. Indicators usedas radar repeater equipments for height-finding radar systems.

ROENTGEN: A unit of exposure dosage ofnuclear radiation.

ROUTINE: A set of coded instructions ar-ranged in proper sequence to direct thecomputer to perform a desired operation orsequence of operations.

SAM: Surface-to-air missile.SCD: Ship's center display. A sonar CRT

presentation display where the electron beambegins an expanding spiral sweep at the centerof the indicator tube.

SELECTIVITY: The relative ability of a re-ceiver to select a particular frequency andto reject all others.

SENSITIVITY: The relative ability of a re-ceiver to amplify small signal voltages.

SHIELDING: A metallic covering used to pre-vent magnetic or electrostatic coupling be-tween adjacent circuits.

SHORAN: Short range navigation. A veryaccurate short range navigational aid usedto determine position. Ship or aircraftradar signals automatically trigger off twofixed transmitters ashore for range com-parison and determination.

SHORT WAVE: Refers to radio operation onfrequencies higher than those used at thepresent time for commercial broadcasting.The range of frequencies extend from 1500kilohertz to 30,000 kilohertz.

SHUNT: Parallel. A parallel resistor placedin an ammeter to increase its range.

SIDEBAND POWER: The power contained inthe sidebands. It is to this power that areceiver responds, not to the carrier power,when receiving a modulated wave.

SIDEBANDS: Two bands of frequencies, oneabove and one below the carrier frequency,produced as a result of modulation of a car-rier. The upper sideband contains the fre-quencies that are the sums of the carrier andmodulated frequencies. The lower sidebandcontains the difference of these frequencies.

SIF: Selective identification feature. Makesthe system of identifying friendly units

14

much more secure and more positive. Anadded improvement to the MARK X IFFsystem.

SILENT TUNING: A method of switching alow power continuous wave signal into adummy load for tuning and silencing apossible radiating transmitter antennaagainst detection during a period of silence.The system is kept continuously tuned formaximum output at all times.

SINS: Ships inertial navigation system. Anavigational aid first developed for sub-marines. This dead reckoning system is aself-contained guidance system which op-erates on art arrangement of three gyrosand two accelerometers that automaticallyfollow a preset course. Aircraft and missilesalso use an inertial guidance system.

SKIP DISTANCE: The distance on the earth'ssurface between the points where a radioskywave is reflected successively betweenthe earth and the ionosphere.

SKYWAVE: A radio wave which travels upwardinto the sky from a transmitter antenna andis, for the most part, bent back to earthby the ionosphere.

SOFTWARE: Pertains to the programs androutines used with computers. The totalityof programs and routines used to extend thecapabilities of computers. In contrast toHARDWARE which is the construction parts(mechanical, electrical, and electronic ele-ments) of the computer.

SOLENOID: A multiturn coil of wire woundin a uniform layer or layers on a hollowcylindrical form.

SOLID STATE: The electronic components thatconvey or control electrons within solidmaterials.

SONAR: Sound navigation and ranging. Elec-tronic equipment used for underwater de-tection of objects and range of these objects,also to determine the ocean profile anddepths.

SPECTRUM: Arrangement of electromagneticradiation energy wavelengths from the long-est to the shortest radio waves.

STATIC: Any electrical disturbance causedby atmospheric conditions. Also a fixed,nonvarying condition, without motion.

SUBTRACK: The path traced on the earth bya satellite passing directly overhead.

SUPERHETERODYNE: A radio receiver whichconverts the carrier wave into a fixed

if


intermediate lower radio frequency which isthen highly amplified.

SURFACF WAVE: A radio wave which travelsalong the surface of the earth, bending withthe earth's curvature.

SYNCHRONOUS: Happening at the same time;having the same period and phase.

TACAN: Tactical communication air naviga-tion. An electronic polar coordinate sys-tem that enables an aircraft pilot to readcontinuously, the distance and bearing of aradio beacon transmitter onboard ship oron ground.

TCD: Target center display. A spiral sweepdisplay in which the point of origin is moved,usually off the CRT tube, until a given targetecho appears at the exact center of display.

THERMOCLINE: The layer in the sea where thetemperature decreases continuously withdepth. Usually the decrease (gradient) isgreater than 2.7 degrees Fahrenheit per 165feet in depth.

THYRATRON: A hot-cathode, gas-dischargetube in which one or more electrodes areused to control electrostatically the startingof an unidirectional flow of current.

TONE CONTROL: A method of emphasizingeither low or high tones at will in an AFamplifier.

TONE MODULATION: A type of code-signaltransmission obtained by causing the RFcarrier amplitude to vary at a fixed audio-frequency.

TRANSCEIVER: Combination of radio trans-mitting and receiving equipment employingcommon circuit components in a commonhousing for portable or mobile use.

TRANSDUCER: A general term for any devicethat converts energy from one form to an-other, always retaining the characteristicamplitude variations of the energy beingconverted.

TRANSFORMER: A device composed of twoor more coils, linked by magnetic lines offorce, used to transfer energy from onecircuit to another.

TRANSMISSIONS: Passage of radio waves inthe space between transmitter and receivingstation.

TRANSMITTER: A comprehensive term appliedto all of the equipment used for generatingand amplifying an RF carrier signal, modu-lating this carrier with intelligence, ampli-fying and feeding the modulated RF carrierto the antenna for transmission into space.

15

TRANSPONDER: An acoustic device that canbe activated upon receipt of a sound orradio signal.

TRUE BEARING: A bearing given in relationto true geographic north which is a pointon earth about which one end of the earthrevolves on its axis. The axis of earthaligns with the north star. (It is not theearth's magnetic pole.)

TUNED CIRCUIT: A resonant circuit.TUNING: The process of adjusting a radio

circuit to resonance with the desired fre-quency.

UHF: Ultra high frequency. The spectrumrange between 300 million hertz to 3000million hertz.

ULTRASONICS: The field of science devotedto frequencies of sound above the humanaudio range, i.e., above 20 kHz.

UNIDIRECTIONAL: Flowing in one directiononly. (Direct current is unidirectional.)

UT: Universal time. Greenwich mean time.The mean solar time from the meridian ofGreenwich from which geographers and navi-gators count their longitude. It is adoptedas the prime basis for standard time through-out the world.

USB: Upper sideband communications. (seeSIDEBANDS).

VAC: Volts, AC. Abbreviation for alternatingcurrent voltage.

VACUUM-TUBE VOLTMETER (VTVM): Adevice which uses either the amplifier char-acteristic or the rectifier characteristicof a vacuum tube or both to measure eitherDC or AC voltages. Its input impedanceis very high, and the current used to actuatethe meter movement is not taken from thecircuit being measured. It can be used toobtain accurate measurements in sensitivecircuits.

VDS: Variable depth sonar. Equipment de-veloped to minimize the thermal layers inthe ocean by lowering the transducer tooptimum depths when searching for targets.

VELOCITY: A rate of change of distance withrespect to time in a given direction.

VHF: Very high frequency. The spectrumrange from 30 million hertz to 300 millionhertz.

VOLTAGE AMPLIFICATION: The process ofamplifying a signal to produce a gain involtage. The voltage gain of an amplifieris the ratio of its alternating-voltage outputto its alternating-voltage input.

/9


VOLUME: A term used to denote the soundintensity (amount of radio output) of areceiver or audio amplifier.

VOLUME CONTROL: A device for controllingthe output volume.

WATT: The basic unit of electrical power.WAVE: The progressive movement (propaga-

tion) either of sound or electromagneticwaves through a conducting medium, asrhythmical disturbances.

WAVEGUIDE: A hollow rectangular or roundpipe (plumbing) used as a transmission lineto guide electromagnetic waves.

WAVELENGTH: The distance in meters trav-eled by a wave during the time intervalof one complete cycle. It is equal to thevelocity divided by the frequency.

WAVE PROPAGATION: The radiation, as froman antenna, of RF energy into space, or ofsound energy into a conducting medium.

WCS: Weapons control system. A group ofinterconnected and interrelated equipments

16

that are used to control the delivery ofeffective gun and missile firing on selectedtargets.

WORD, COMPUTER: An ordered set of char-acters which occupies one storage locationand is treated by the computer circuits asa unit and transferred as such. Ordinarilya word is treated by the control unit asan instruction, and by the arithmetic unitas a quantity. Word lengths may be fixedor variable depending on the particularcomputer.

XBT: Expendable bathythermograph. A non-reusable thermometer type instrumentdropped into the ocean for measuring watertemperature at different levels, and the asso-ciated shipboard equipment used for launch-ing and recording the data automatically.

XMTR: Abbreviation for transmitter.X RAY: Penetrating electromagnetic radiation.

Non-nuclear in origin.

0.0

CHAPTER 2

RADIO

The word "radio" can be defined brieflyas the transmission of signals through spaceby means of electromagnetic waves. Usually,the term is used in referring to the transmis-sion of intelligence code and sound signals,although television (picture signals) and radar(pulse signals) also depend on electromagneticwaves.

Of the several methods of radio communi-cations available, those utilized most com-monly by the Navy are radiotelegraphy, radio-telephony, radioteletype, radiofacsimile, anddigital data. These modes are defined asfollows:

1. RADIOTELEGRAPHY: The transmissionof intelligence coded radiofrequency waves inthe form of short transmissions (dots) andlong transmissions (dashes).

2. RADIOTELEPHONY: The transmissionof sound intelligence (voice, music, or tones)by means of radiofrequency waves.

3. RADIOTELETYPE: The transmission ofmessages from a teletypewriter or coded tapeover a radiofrequency channel by means ofcoded combinations of mark and space im-pulses.

4. RADIOFACSIMILE: The transmissionof still images (weather maps, photographs,sketches, typewritten pages, and the like) overa radiofrequency channel.

5. DIGITAL DATA: The transmissions ofdata from a computer in serial or parallelformat of binary numbers and zero. Theradiofrequency transmission is usually by aseries of pulse code modulations or sidetonemodulations.

Radio equipment can be divided into two broadcategories: transmitting equipment and receiv-ing equipment. Both transmitting and receivingequipments consist basically of electronic powersupplies, amplifiers, and oscillators.

17

A basic radio communication system mayconsist of only a transmitter and a receiver,which are connected by the medium through whichthe electromagnetic waves travel (fig. 2-1).The transmitter comprises an oscillator (whichgenerates a basic radiofrequency), radiofre-quency (RF) amplifiers, and the stages (if any)required to place the audio intelligence on theRF signal (modulator).

The electromagnetic variations are propa-gated through the medium (space) from thetransmitting antenna to the receiving antenna.

The receiving antenna converts that portionof the transmitted electromagnetic energy re-ceived by the antenna into a flow of alternatingradiofrequency currents. The receiver con-verts these current changes into the intelligencethat is contained in the transmission.

FREQUENCY SPECTRUM

Radio transmitters operate on frequenciesranging from 10,000 hertz to several thousandmegahertz. These frequencies are divided intoeight bands as shown in table 2-1.

TRANSMITTINGANTENNA

RECEIVINGANTENNA

COMMUNICATIONMEDIUM

TRANSMITTER

72.50Figure 2-1.Basic radio communication

system.


Table 2-1.Bands of Frequencies

AbbreviationFrequency

bandFrequency

range

VLF Very lowfrequency

below 30 kHz

LF Lowfrequency

30-300 kHz

MF Mediumfrequency

300-3000 kHz

HF Highfrequency

3000-30,000 kHz

VHF Very highfrequency

30-300 MHz

UHF Ultrahighfrequency

300-3000 MHz

SHF Superhighfrequency

3000-30,000 MHz

EHF Extremely 30-300 GHzMOfrequency

Because the VLF and LF bands requiregreat power and long antennas for efficienttransmission, the Navy normally uses thesebands mostly for shore station transmissions.(The antenna length varies inversely with fre-quency.)

Only the upper and lower ends of the MFband have naval use because of the commercialbroadcast band extending from about 550 kHzto 1700 kHz.

Most shipboard radio communications areconducted in the HF band. Consequently, alarge percentage of shipboard transmitters andreceivers are designed to operate in this band.The HF band lends itself well for long-rangecommunications.

A large portion of the lower end of theVHF band is assigned to the commercial tele-vision industry and is used by the Armed Forcesonly in special instances. The upper portionof the VHF band (225 MHz to 300 MHz) and thelower portion of the UHF band (300 MHz to400 MHz) are used extensively by the Navy fortheir UHF communications. The frequenciesabove 400 MHz in the UHF band through theSHF and EHF bands are normally used forradar and special equipment.

18

ANTENNAS AND PROPAGATION

An antenna is a conductor or system ofconductors that radiates or intercepts energyin the form of electroniagnetic waves. In itselementary form, an antenna may be simply alength of elevated wire. For communicationn.nd radar work, however, other considerationsmake the design of an antenna system a morecomplex problem. For instance, the height ofthe radiator above ground, the conductivity ofthe earth below the radiator, and the shape anddimensions of an antenna all affect the radiatedfield pattern in space.

When RF current flows through a trans-mitting antenna, radio waves are radiated fromthe antenna in much the same way that wavestravel on the surface of a pond into which arock is thrown. Part of each radio wave movesoutward in contact with the ground to form thegroundwave, and the rest of the wave movesupward and outward to form the skywave. Theground and sky portions of the radio wave areresponsible for two different methods of carry-ing signals from transmitter to receiver.

Commonly, the groundwave is considered tobe made up of two parts: a surface wave and adirect wave. The surface wave travels alongthe surface of the earth, whereas the direct wavetravels in the space immediately above thesurface of the earth. The groundwave is usedboth for short-range communications at highfrequencies with low power and for long-rangecommunications at low frequencies with veryhigh power.

That part of the radio wave that movesupward and outward, but is not in contact withthe ground, is called the skywave. An ionizedbelt, found in the rarefied atmosphere approxi-mately 40 to 350 miles above the earth, is knownas the ionosphere. It refracts (bends) some ofthe energy of the skywave back toward the earth.A receiver in the vicinity of the returningskywave receives strong signals even thoughthe receiver is several hundred miles beyondthe range of the groundwave. The skywave isused for long-range, high-frequency, daylightcommunications. It also provides a means forlong-range contacts at somewhat lower fre-quencies at night.

The direct wave is that portion of radiatedenergy which contains no sky .or ground wavecomponents. It attempts to travel in a straightline, however, it is refracted (bent) slightlydownward due to atmospheric density. All

Chapter 2RADIO

VHF and UHF communications are conductedvia the direct wave.

CONTINUOUS-WAVE TRANSMITTER

One of the simplest types of radio trans-mitten. is the continuous-wave (CW) trans-mitter (fig. 2-2). This CW transmitter isdesigned to send short or long pulse of RFenergy to form the dots and dashes of theMorse code characters. Morse code trans-mission is also known as ICW (interrupt con-tinuous wave).

A CW transmitter has four essential com-ponents: (1) a generator of RF oscillations,(2) a means of amplifying, and, if necessary,multiplying the frequencies of these oscilla-tions, (3) a method of turning the RF outputon and off (keying) in accordance with thecode to be transmitted, and (4) a power supplyto provide the operating potential to the variouselectron tubes and transistors. Although notactually a part of the transmitter, an antennais required to radiate the keyed output of thetransmitter.

OSCILLATOR

The oscillator is the basic frequency de-termining element of the transmitter. It ishere that the RF signal is generated. If theoscillator fails to function, no RF signals willbe produced.

Frequently, the oscillator operates on asubmultiple of the transmitter output frequency.When this occurs, a process called frequency

OSCILLATORBUFFER-

FREOUENCY --e.MIAMPLIER

PUVit.FTSUPPLY

t,c0A Tip&CI

ANTENNA

TOAMPLIFIEROTOWER

AMP

20.201Figure 2-2.Continuous-wave transmitter.

19

,P3

multiplication is used to increase the trans-mitter frequency as desired. This action isparticularly desirable when the output frequencyis so high that stable oscillations are difficultto obtain.

Present-day transmitters may contain sev-eral oscillators to perform various functions.In general, only one of these is used to generatethe basic transmitter radiofrequency. Thisoscillator usually is called the masteroscillator(MO) to distinguish it from any other oscillatorcircuit in the transmitter.

Transmitters capable of transmitting over awide frequency range normally have the totalfrequency coverage divided into separate bands.In such instances, the frequency-determiningcomponents in the oscillator (and other stages asnecessary) are selected by means of a bandswitch.

BUFFER FREQUENCY MULTIPLIER

The buffer stage is situated between the os-cillator and subsequent stages to isolate theoscillator from load reflections. When thetransmitter is keyed, the associated changes inthe condition of the transmitter stages maycause undesired voltage or current reflections.If permitted to reach the oscillator, these re-flections would cause the oscillator frequencyto change.

As stated previously, the oscillator may beoperated at a submultiple of the transmitteroutput frequency. With this mode of operation,the buffer stage usually performs the additionalfunction of frequency multiplination in all butsingle sideband equipment.

POWER AMPLIFIER

The power amplifier (PA) is operated insuch a manner that it greatly increases themagnitude of the RF current and voltage. Theoutput from the PA is fed to the antenna viaRF transformers and transmission lines. ThePA is simply another RF amplifier. The laststage of RF amplification in a transmitter isusually referred to as the power amplifier.

POWER SUPPLY

Transmitters (and many other types ofelectronic equipment) require DC voltages rang-ing from a minus hundreds of volts to plusthousands of volts. Additionally, they need AC


voltages at smaller values than those availablefrom the ship's normal power source. It is thefunction of the power supply to furnish thesevoltages at the necessary current ratings.Usually, this is accomplished through trans-former-rectifier-filter action, with the ship'spower as the source of supply.

VOICE MODULATION

Because it is impractical to transmit elec-tromagnetic waves at sound frequencies (15hertz to 20,000 hertz), the intelligence, bymeans of modulation, is impressed upon ahigher frequency for transmission. Modulationis the process of varying the amplitude or thefrequency of a carrier signal (RF output of thetransmitter) at the rate of an audio signal. Thecomposite wave thus contains radiofrequencyand audiofrequency components. The audio por-tions of the modulation are removed beforetransmission leaving the audio effect (envelope)on the RF wave for transmission. A receiverthat is within reception range and tuned to thecarrier frequency accepts the transmitter signaland removes the audio component from the

VOICEINPUT

OSCILLATOR

SPEECHAMPLIFIER

r

carrier. This process is called demodulation ordetection. The audio signal is then fed to aloudspeaker or headset which reproduces theoriginal sound.

AMPLITUDE MODULATION

Amplitude modulation (AM) is the processof combining audiofrequency and radiofrequencysignals in a manner which causes the amplitudeof the radiofrequency waves to vary at anaudiofrequency rate. This process can be ac-complished by removing the key and modifyingthe continuous-wave transmitter (fig. 2-2) sothat the audio output from a microphone (andnecessary amplifiers) is impressed on thecarrier frequency. The required changes areincorporated in the block diagram of a basicAM radiotelephone transmitter, as shown infigure 2-3. The top row of blocks producesand amplifies the RF carrier frequency; thelower row produces and amplifies the audio-frequency. The speech amplifier driver, andmodulator stages provide the voltage and poweramplification required in the modulationprocess.

RACHOFREOUENCYSIGNAL

"Iff JBUFFER

AMPLIFIER

ANTENNA

AMPLITUDE -MODULATEDG NA L

DRIVER

POWERAMPLIFIER

1

2

3f`x

1

1 I

1 :

1

1

,

% 4

5r-,-

MODULATOR

1

141

DC AU0i 0 F REOUENCYVOLTAGE SIGNAL

POWER

SUPPLY

Figure 2-3.An AM radiotelephone transmitter.

20

1

13.53

Chapter 2RADIO

Assume that the modulating audio signalis of constant frequency. The audio voltageis fed into the RF power amplifier stage sothat it alternately adds to and subtracts fromthe DC supply voltage in the amplifier. Anincrease in voltage in the PA increases the RFpower output. Conversely, a decrease involtage decreases the RF power. The presenceof the audio voltage in series with the supplyvoltage causes the overall amplitude of the RFfield at the antenna to increase gradually instrength during the time the audio voltage isincreasing (from 1 to 2 on the waveforms,fig. 2-3). It also results in a decrease instrength during the time the audio output isdecreasing (from 2 to 3). Similar variationsin RF power output occur throughout each audiocycle. The waveform produced at the antennathus contains the sum and difference frequenciescombined with the carrier to produce a com-posite radio signal from which the audio maybeextracted in a receiver.

Actually, the two frequencies introduced inthe PA during the modulation process combineto produce two additional frequencies calledsideband frequencies. The sideband frequenciesare always related to the original two fre-quencies as sum and difference frequencies,respectively. The sum frequency, i.e., thesum of the RF carrier and audio-modulatingfrequencies, is called the upper sideband; thedifference frequency is the lower sideband. At100 percent modulation, one-sixth of the totalpower (RF plus audio power) appears in eachof the sidebands.

The relationship of the carrier, audio, andsideband frequencies is illustrated in figure 2-4.Assume that the carrier frequency is 1000 kHzat 100 watts, and that the audio-modulating fre-quency is a single 1-kHz tone at 50 watts. Then,each of the sidebands is displaced 1000 hertzfrom the carrier frequency. The lower side-band is 1,000,000 hertz -1000 hertz = 999,000hertz (or 999 kHz). The upper sideband is1,000,000 hertz +1000 hertz = 1,001,000 Hz (or1001 kHz). The power in each sideband (25watts) is one-sixth the total transmitter outputpower (150 watts).

Note that the amplitude of each of the threefrequencies is constant when considered alone.But, because these frequencies appear simul-taneously at the output, they add to form onecomposite envelope (signal). This envelope isin the shape of the output waveform shown infigure 2-3.

21

11111MIW

j 1 PI 1 I f

11 ili..

lot./.'. ;,4,

'I t, ' 'Ar fit ti , ,,,,,,s

., r "1 1/1/11 il ' P 5,0*-.41, 0 T i LI e9t

20.184Figure 2-4.Carrier wave and its sideband

frequencies.

During modulation, the peak voltages andcurrents on the RF power amplifier stage aregreater than values that occur when the stageis not modulated. To prevent damage to theequipment, a transmitter, designed to transmitboth CW and radiotelephone signals, is providedwith controls that reduce the transmitter poweroutput for radiotelephone nperation.

FREQUENCY MODULATION

Intelligence can be transmitted by varying thefrequency of a carrier signal of constant ampli-tude. The carrier frequency can be varied asmall amount on either side of its average orassigned frequency by means of the A F modulat-ing signal. The amount the carrier is varieddepends on the magnitude of the modulatingsignal. The rate with which the carrier isshifted depends on the frequency of the modu-lating signal. With or without modulation, theamplitude of the RF carrier remains sub-stantially constant.

A block diagram of a representative FMtransmitter, in which frequency modulation isaccomplished by a phase-shift system, is shownin figure 2-5. The transmitter oscillator ismaintained at a constant frequency by meansof a quartz crystal. This constant-frequencysignal passes through an amplifier that in-creases the amplitude of the RF subcarrier.The audio signal is applied to this carrier in aphase-shift network in such a manner as tocause the frequency of the carrier to shiftaccording to the variations of the audio signal.


CRYSTALCONTROLLEDOSCILLATOR

RFSUBCARRIER

AMPLIFIER

f

PHASE SHIFTNETWORK

RADIOFREOUENCYCARRIER AU010FREOUENC

MICROPHONE

FIRSTFIRSTAF

AMPLIFIER

f+,I 'id 111,;

DOUBLER

FM WAVE OF LOWRADIOFREOUENCY

SECONDAF

AMPLIFIER

SECONDDOUBLER

FM WAVE OF HIGHRADIOFREOUENCY

20.190Figure 2-5.Block diagram of FM transmitter and waveforms.

The FM output of the phase-shift network is fedinto a series of frequency multipliers thatraisethe signal to the desired output frequency.Then the signal is amplified in the power ampli-fier and coupled to the antenna for radiation.

RECEIVERS

The modulated RF carrier wave produced atthe transmitter travels through space as anelectromagnetic wave. When the wave passesacross a receiving antenna, it induces smallRF voltages (and associated currents) in theantenna wire at the frequency of the trans-mitted signal. The signal voltage is coupledto the receiver input via an antenna coil orantenna transformer.

Electromagnetic energy is received fromseveral transmitters simultaneously by the re-ceiving antenna. The receiving circuits mustselect the desired transmitter signal from thosepresent at the antenna and amplify this signal.The RF stages must isolate the internally gen-erated frequencies within the receiver from theantenna which is necessary in observing radiosilence. Further, the receiver must extractthe audio component from the carrier frequencyby a process called demodulation, or detection,and amplify the audio component to theproper magnitude to operate a loudspeaker orearphones.

22

TUNED RADIOFREQUENCY RECEIVER

The tuned radiofrequency (TRF) receiver isthe forerunner of the modern military receiver.It is of the simplest design, and lends itselfwell for the purpose of explaining basic re-ceiver principles. Although not used exten-sively in the Navy, it has advantages and maycome back again due to improvements in solidstate devices.

The TRF receiver (fig. 2-6) consists of oneor more RF amplifier stages, a detector (de-modulator) stage, one or more stages of audioamplification, a power supply, and a reproducer(usually loudspeaker or earphones). Wave-forms that appear at the input and output ofeach stage are shown in the illustration.

Radiofrequency Stages

Radiofrequency stages of the receiver aredesigned to select and amplify the desired sig-nal. The relative ability of a receiver to selecta particular frequency and to reject all othersis called the selectivity of the receiver. Therelative ability of the receiver to amplifysmall signal voltages is called the sensitivityof the receiver. Both of these values can beimproved within limits, by increasing the num-ber of RF stages.

Chapter 2RADIO

flocnito

114,2,

RADIO- AUDIO-FREQUENCY DETECTOR FREQUENCY

AMPLIFIER

POWERSUPPLY

REPRODUCER

4

Figure 2-6.Block diagram of TRF receiver and waveforms.

Detector

In the detector stage, the intelligence com-ponent of the modulated wave is separatedfrom the RF carrier. The separation process,called detection or demodulation, consists ofrectifying the AM envelope and removing (filter-ing out) the RF carrier.

As seen earlier, amplitude modulation ofan RF carrier with audio intelligence causesboth the positive and the negative half cyclesof RF to vary in amplitude. The resultant am-plitude variations are a replica of the modu-lating audio signal. The detector stage ac-cepts the RF amplitude variations at its in-put, and produces audio variations at its out-put.

Audio Amplifier

The function of the audiofrequency sectionof the receiver is to amplify the audio *signalfrom the detector. In most instances, theamount of audio amplification necessary dependson the type of reproducer. If the reproducer

23

.27

13.64

is earphones, only one stage of amplificationmay be required.

Disadvantages of TRF Receiver

The principal disadvantages of the TRFreceiver has been its inability to reject un-wanted frequencies, and its inability to amplifydesired frequencies uniformly. In other words,the selectivity and the sensitivity of the re-ceiver are not uniform over its frequencyrange. As the TRF receiver is being tunedfrom the low-frequency end of its range towardsthe high-frequency end, the selectivity of thereceiver will decrease; conversely, the sensi-tivity will increase. Solid state microminiaturecircuits are helping to minimize these dis-advantages.

SUPERHETERODYNE (AM) RECEIVER

The superheterodyne receiver was developedto overcome the disadvantages of TRF receivers.The essential difference between the two typesof receivers is in the amplifier stage(s) pre-ceding the detector. Whereas the RF amplifier


preceding the detector in the TRF receiveris tunable, the corresponding amplifier in thesuperheterodyne receiver is pretuned to onefixed frequency called the intermediate fre-quency (IF).

The intermediate frequency is obtainedthrough the principle of frequency conversionby heterodyning a signal generated in a localoscillator of the receiver with the incomingsignal in a mixer stage. Thus, an incomingsignal is converted to the fixed intermediatefrequency, and the IF amplifier operates withuniform selectivity and sensitivity over theentire tuning range of the receiver.

A block diagram of a representative super-heterodyne receiver is shown in figure 2-7.Although not illustrated, a superheterodyne re-ceiver may have more than one frequencyconverting stage and as many amplifiers asneeded to obtain the desired power output.

Heterodyning

The intermediate frequency is produced bya process called heterodyning. This actiontakes place in the mixer, so called because itreceives and combines (mixes) two frequencies.

RF

AMPLIFIER

ENVELOPES

MIXER

LOCALOSCILLATOR

These two frequencies are the incoming signalfrom the RF amplifier, and a locally gen-erated, unmodulated RF signal of constantamplitude from the local oscillator.

The heterodyning action in the mixer (alsocalled the first detector) produces four fre-quencies at the mixer output. These frequenciesare (1) the incoming RF signal, (2) the localoscillator signal, (3) the sum of the incomingRF and local oscillator signals, and (4) the dif-ference of these signals. Both the sum anddifference frequencies contain the amplitudemodulation. Usually, the difference-frequencyis used as the intermediate frequency, althoughthe sum-frequency can be used equally as well.A common intermediate frequency for com-munication receivers is 455 kHz.

SINGLE-SIDEBAND COMMUNICATIONS

As explained earlier, the intelligence ofamplitude-modulated signals is contained in thesidebands, and for normal amplitude modula-tion, the intelligence in both sidebands is thesame. Radio intelligence can be conveyed byremoving the carrier and one sideband andtransmitting only the remaining sideband if

IFAMPLIFIER

4INSECOND

DETECTORe AF

AM PL IFI ERSPEAKER

RF CARRIER

OSCILLATOR

AMPLIFI DCARRIER IF CARRIER AMPLIFIED

IF CARRIER

AUDIOCOMPONENT

AMPLIFIEDAUDIO COMPONENT

13.66Figure 2-7.Block diagram of an AM superheterodyne receiver and waveforms.

24

dl

r.

s?

Chapter 2RADIO

some method of carrier reinsertion is used ateach receiving station. This type of communi-cations is called single-sideband (SSB) com-munications---all transmitting power is con-centrated in the one sideband. The RF carrier,which has been either partially or entirelysuppressed at the transmitter, must be rein-serted at the receiver to combine with thereceived single sideband. The result is awaveform identical to the one produced in thetransmitter before suppression of the carrierand one sideband.

Single-sideband communications has severaladvantages over the conventional AM system.One of the major advantages is that all of theradiated power is utilized in conveying theintelligence, and no power is lost in trans-mitting the carrier or duplicate sideband. Asecond advantage is that the bandwidth neces-sary for single-sideband reception is narrowerthan that required to receive both sidebandsfor the same contained intelligence; therefore,more single-sideband channels can be accom-modated in a given band of frequencies. Third,the AM signal is less affected by selectivefading or by manmade interferences.

RFAMPLIFIER

11\1 Al' 1\1,

MIXER

LOCALOSCILLATOR

V/I0E- RANOIF

AMPLIFIER

SUPERHETERODYNE (FM) RECEIVER

The function of a frequency modulated (FM)receiver is the same as an AM superheterodynereceiver. There are certain important differ-ences in component construction and waveformdesign. Compare block diagrams (figs. 2-7and 2-8). In both AM and FM sets the ampli-tude of the incoming signal is increased in theRF stages. The mixer combines the incomingRF with the local oscillator RF signals to pro-duce the intermediate frequency which is thenamplified by one or more IF amplifier stages.Note that the FM receiver has a wide-band IFamplifier. This is necessary, since the band-width requirements for any type of modulationis that it must be wide enough to receive andpass all the side-frequency components of themodulated signal without distortion.

Sidebands created by FM and phase-modu-lated (PM) systems differ from those of theAM system. They occur at integral multiplesof the modulating frequency on either side ofthe carrier wave. Remember that the AMsystem consists of a single set of side fre-quencies for each radiofrequency signal thatis modulated. An FM or phase-modulated

.1OSCILLATOR WAVE

LIMITER DISCRIMINATOR

Figure 2-8.Block diagram of FM receiver and waveforms.

25

.29

AFAMPLIFIER

SPEAKER

13.67


signal inherently occupies a wider band thanAM and the number of these extra sidebandsthat occur during FM transmission is relatedto the amplitudes and frequencies of the audiosignal.

Now we begin to see a marked differencebetween the two receiver diagrams (figs. 2-7and 2-8). While AM demodulation involves thedetection of variations in the amplitude of thesignal, FM demodulation is the process ofdetecting variations in the frequency of thesignal. Thus, in AM superheterodyne receivers,the "detector" is designed to respond to ampli-tude variations of the signal and in FM receivers,a "discriminator" is designed to respond tofrequency shift variations. A discriminator ispreceded by a limiter, which limits all signalsto the same amplitude level to minimize noiseinterference. The audiofrequency component isthen removed by the discriminator. This audiosignal is amplified in the AF amplifier andsent to the speaker.

Electrically, there are only two fundamentalsections of the FM receiver which are dif-ferent from the AM receiver; the discriminator(second detector) and the accompanying limiter.

Some Advantages of FM Receivers

In normal reception FM signals are totallyabsent of static while AM signals are subjectto cracking noises and whistles. FM followedAM in development and had the advantage ofoperating at the higher frequency where spec-trum is more plentiful. FM signals provide amuch more realistic reproduction of soundbecause of an increased number of sidebands.

The major disadvantage of FM is the widebandpass required to transmit the FM signals.Each station must be assigned a wide band inthe frequency spectrum. During FM transmis-sions, the number of significant sidebands whichmust be transmitted in order to obtain thedesired fidelity is equal to the deviation dividedby the highest audiofrequency to be used. Thus,if the deviation is 40 kHz and the highest audio-frequency is 10 kHz, the number of significantsidebands is

40 kHz10 kHz -4

This number of sidebands exists on both sidesof the rest frequency; thus, there are 8 sig-nificant sidebands. Because the audiofrequency

26

is 10 kHz, and there are 8 sidebands, andbandwidth must accommodate an 80 kHz signal.This is considerably wider than the 10- to15-kHz bandpass for AM transmitting stations.

Because of the wide bandwidth requirements,the Navy uses very little FM equipment. Onetype of FM equipment presently being used bythe Navy is a series of walkie-talkie trans-ceivers which provide voice communications foramphibious operations.

Frequency Conversion

Frequency conversion is accomplished byemploying the heterodyne principle of beatingtwo frequencies together to get an intermediatefrequency. We have been studying this principlewhich is sometimes called single conversion.

Some receivers use double or triple con-version, sometimes referred to as double ortriple heterodyning or detection, These re-ceivers are more selective since they suppressimage signals in order to yield sharp signaldiscrimination. (The image frequency is anundesired modulated carrier frequency that dif-fers from the frequency to which a superheter-odyne receiver is tuned by twice the intermediatefrequency.) Double and triple conversion re-ceivers also have better adjacent channel selec-tivity than can be realized in single conversionsets.

3D

MULTIPLEXING

Multiplexing techniques used in naval com-munications is becoming of vital interest toevery naval officer. Today our frequencyspectrum is becoming overcrowded. This situa-tion is being alleviated by the simultaneoustransmission of two or more signals using acommon carrier wave or a single path in atelegraph system called multiplexing.

CLASSIFICATION OF RADIO EMISSIONS

Table 2-2 is a reference table pertainingto radio transmission. The three main clas-sifications of radio emission are shown asamplitude modulation, frequency or phase mod-ulation, and pulse modulation.

To better acquaint ourselves with radio emis-sions, let us consider a few combinations andrepresentative examples in table 2-2. Al refersto telegraphic communications by keying an

Chapter 2RADIO

Table 2-2.Classification of Radio Emissions.

Symbol

AO

AlA2A3A3AA3BA3JA4ASA7MBA7J

A9A9AA9B

FOFlF2

F3F4F5F9

POP1P2DP2EP2F

P3DP3EP3FP9

Type of transmission

Amplitude modulatedContinuous wave (CW) no modulation.Continuous-wave (CW) telegraphy. On-off keying.Telegraphy by keying of a modulated emission.TelephonyDouble sideband, full carrier.TelephonySingle sideband, reduced carrier.TelephonyTwo independent sidebands with reduced carrier.TelephonySingle sideband, suppressed carrier.Facsimile.Television.Telegraphy Multichannel Audiofrequency Tone Shift. (AFTSRATT).Telegraphy Multichannel Audiofrequency Tone Shift. Two Independent Sidebands.Telegraphy Multichannel Audiofrequency Tone Shift. Single Sideband Suppressed

Carrier.Composite transmissions and cases not covered by above classifications of emissions.Composite transmissions, reduced carrier.Composite transmissions, two independent sidebands.

Frequency (or phase) modulatedAbsence of modulationTelegraphy by Radio Frequency Carrier Shift. (RFCSRATT). No modulation.Telegraphy by keying of a modulating audiofrequency. Also by keying of modulated

emission.Telephony.Facsimile.Television.Composite transmissions and cases not covered by above classification of emissions.

Pulse modulatedAbsence of modulation intended to carry information (such as radar).TelegraphyNo modulation of audiofrequency.Telegraphy by keying an audiofrequency which modulates the pulse in its amplitude.Telegraphy by keying an audiofrequency which modulates the pulse in its width.Telegraphy by keying an audiofrequency which modulates the pulse in its phase (or

position).TelephonyAmplitude modulated.TelephonyWidth modulated.TelephonyPhase (or position) modulated.Composite transmissions and cases not covered by above classification of emissions.

Sampling of Transmitter EquipmentDESIGNATOR TYPE OF EMISSION SAMPLE EQUIPMENT

2.04A2 1020 Hz AFT Beacon AN/WRT-1 (MF)36F3 Telephony (FM) AN/PRC-10 (VHF)

For further reference on radiofrequency emission, see JANAP 195.

27

3/


unmodulated carrier wave (CW). A2 is also aform of telegraphy, but in this case, the trans-mitted signal is a keyed modulated carrierwave, generally referred to as MCW. In figure2-9A and B, note that many more signal wavesare involved in forming the DASH than informing the DOT. This results from the timedifference in the keying operation.

VIMICCIONA

DOT DASH

A. CW TRANSMISSION FOR TELEGRAPHY

DOT DASH

B. MCW TRANSMISSION FOR TELEGRAPHY

LETTER "G"

START I 2 3 4 5 STOP

VZ.

TI ME

C. FIVE SIGNAL COMBINATIONS MAKE OFALPHABET FOR TELETYPE.

120.63Figure 2-9.Representative types of

special transmissions.

28

Various combinations of dots and dashes areused to form the alphabet by Morse code. Theterm "continuous wave" (CW) refers to thefact that the amplitude is continuous and doesnot vary. It does not refer to the interruptionrate.

The advantage of CW over MCW is the nar-row frequency band type of transmission in-volved for CW. CW is also advantageous forlong range transmissions under severe noiseconditions. Intelligence is easily encrypted forsecurity using CW (Al) transmissions. Al radioreceivers, however, require a beat frequencyoscillator (BFO) input to the IF stage to heter-odyne with the continuous wave code so thataudible tones can be reproduced at the seconddetector. This is not required for A2 recep-tion since the incoming wave is modulated(MCW). A2 transmission is not often usedfor telegraphy, however, because a wider fre-quency band is required.

In recent years, the Navy has vastly im-proved its radio teletype (RATT) capabilitieswith new equipment that uses two types ofRATT emissions (FM and AM). Both requirethe use of two discrete radiofrequencies toproduce one channel of radioteletype; one fre-quency for the MARK signal and the other forthe SPACE signal (fig. 2-9C). The STARTsignals are always SPACE, and the STOPsignals are always MARK. Combinations of5 marks and/or spaces make up the variousletters of the code.

The AN/WRT-1 (mentioned as a sampleequipment at the bottom of Table 2-2) is amedium frequency range AM transmitter. Inthis example it is being used as a 1020 Hzaudiofrequency tone homing beacon. 2.04A2indicates the Navy's assigned bandwidth and typeof transmission; 2.04 designates the "necessarybandwidth" in kHz and A2 represents telegraphyby ke}ing of amplitude modulated emission.

The AN/PRC-10, another sample equipment,is an FM transmitter operating in the veryhigh frequency range. In the designator 36F3the 36 indicates the Navy's assigned band-width for the transmitter (36 kHz) and F3 de-notes frequency modulated telephony.

CHAPTER 3

RADIO EQUIPMENT

The equipments discussed and illustratedin this chapter are selected as representativeof the many models and types of radio trans-mitters, receivers, and auxiliary equipmentsused in the fleet today. No attempt is made tocover all of the equipments in use.

Modern shipboard radio equipments must berugged construction for long service life. Thisequipment must be capable of transmitting andreceiving over a wide range of frequenciesand distances, while operating in any one ofseveral modes. Because of limited space aboardships and of ship's motion on rough seas, com-pactness and ruggedness are among the factorsconsidered in designing these equipments.

TRANSMITTERS, TRANSMITTER-RECEIVERS, AND TRANSCEIVERS

A transmitter-receiver comprises a sep-arate transmitter and receiver mounted in thesame rack or cabinet. The same antenna maybe used for the transmitter-receiver arrange-ment. When so used, the capability for sim-ultaneous operation of both the transmittingand receiving equipments does not exist. Theequipments may be operated independently, us-ing separate antennas.

A transceiver is a combined transmitterand receiver in one unit which uses switchingarrangements in order to utilize parts of thesame electronic circuitry for both transmittingand receiving. Hence, a transceiver cannottransmit and receive simultaneously.

MF, AND HF TRANSMITTERS

Transmitters operating in the medium- anhigh-frequency bands of the frequency spec-trum are used chiefly for communication atmedium and long ranges. Some transmittersin these bands, however, are designed forshort-range communication. In most instances,short-range transmitters have a lower output

29

33

power than those designed for communicationat medium and long ranges.

In the following descriptions of specificequipment capabilities, the term "short range"(or "distance") means a measurement lessthan 200 miles; "m,:dium range" is between200 and 1500 miles; and "long range" exceeds1500 miles. These values are approximates,because the range of a given equipment variesconsiderably according to terrain, atmosphericconditions, frequencies, and time of day, month,and year.

Some transmission equipment has a capabil-ity of radio teletype emission. The older equip-ment employed RFCSRATT ( radiof requenc y car-rier shift radioteletype). The newer equipmenthas employed AFTSRATT (audiofrequency toneshift radioteletype). The old designation FSK(frequency shift keyer) is to be replaced withthe above designators since it is more descrip-tive (reference JANAP 195H). This is coveredmore in detail in the next chapter on teletypeequipment.

Transmitters AN/SRT-14, -15, and -16Transmitting sets AN/SRT-14, -15, and -16

are a series of shipboard transmitters designedfor medium- and long-range communications.The AN/SRT-14 (fig. 3-1A) is the basic trans-mitter in the series, with a power output of100 watts. By adding a power booster to thebasic transmitter, it becomes the AN/SR T-15(fig. 3-1B). The AN/SRT-15 has an optionaloutput power of either 100 or 500 watts. Trans-mitter set AN/SRT-16 (fig. 3-1C) consists oftwo AN/SRT-14 equipments plus the booster,furnishing two entirely independent transmittingchannels of 100-watt output, with the 500-wattbooster available for use with either channelwhen desired.

All three transmitters cover the frequencyrange 0.3 to 26 MHz, and may be used for CW,radiotelephone, radioteletype, and facsimile


vELECTRICAL EQUIPMENT CABINET

RADIOFREQUENCYa. AMPLIFIER

__4417r:40ic, fir

1.4 e&C;ta

WV

RACIO MODULATOR

RADIOFREQUENCYOSCILLATOR

A TRANSMITTERAN/SRT-14

POWER SUPPLY

POWER SUPPLY

MOUNTING

RADIOMODULATOR

ELECTRICALEQUIPMENTCABINET

COVER

RADIO

MODULATOR

POWER SUPPLY

ELECTRICALEQUIPMENTCABINET

ELECTRICALEQUIPMENT

CABINET

ELECTRICAL EQUIPMENT CAEpNET

RANO F F.EQ UENCYAmpLIFIck

RACIO MODULATOR

RACIOFREO.UENCYOSCILLATOR

B TRANSMITTER AN/SRT-I5

RADIOFREOUENCYAMPLIFIER

RADIO MODULATOR

RADIOFREQUENCYOSCILLATOR

C TRANSMITTER AN/SRT-I6

POWER SUPPLY

POWER SUPPLY

ELECTRICALEQUIPMENT

CABINET

Figure 3-1.Radio Transmitter AN/SR T-14, -15, -16.

30

POWER SUPPLY

POWER SUPPLY

1.144.1-.3

Chapter 3RADIO EQUIPMENTOEM

transmissions. The 500-watt output pcwer,however, is available only when the AN/SRT-15or the AN/SRT-16 is operating in the frequencyrange of 2 to 26 MHz; at frequencies below 2MHz, output is limited to 100 watts.

Transmitter AN/WRT-1AThe AN/WRT (fig. 3-2) is a shipboard

transmitter designed for operation in the fre-quency range 300 to 1500 kHZ. This equipmentcan transmit CW, RFCS, MCW and voice signals,but it has no SSB capability. When used for CWand RFCS transmissions, the transmitter hasa power output of 500 watts. Voice operation,

RF AMPLIFIER

RF OSCILLATOR

FREQUENCYCONTROL GROUP

CONTROL-POWERSUPPLY

POWER SUPPLY

32.278(76)Figure 3-2.Radio Transmitter AN/WRT-1A.

31

however, reduces the available power to ap-proximately 125 watts.

Because of operating in the medium fre-quencies with a substantial power output, theAN/WRT-1A lends itself well for communicatingover long distances during the hours of dark-ness. Its range is reduced to medium distancesduring daylight hours.Transmitter AN/WRT-2

Radio transmitter AN/WRT-2 (not illus-trated) is similar in size and appearance tothe AN/WRT-1A. It covers the frequency spec-trum between 2 and 30 MHz, and has an averagepower output of 500 watts for CW, AFTS, andcompatible AM modes of operation. When op-erating as a single-sideband transmitter, itproduces 1000 watts. An additional feature ofthe AN/WRT-2 is that it provides independentsideband operation. This mode of operationpermits simultaneous transmission of both side-bands, each one carrying separate intelligence.

Actual transmitter output values as gainedfrom feedback from the fleet indicate that thepower output levels are substantially lower thanthose cited above. Personnel must ensure thatthe transmitter is properly maintained and thatoptimum tuning exists for all operating modes.(Refer to Chapter 2, Table 2-2, "Classificationsof Radio Emissions," for more detail on themodes of operation for the following radio sets.)

As indicated by its operating frequenciesand power outputs, the AN/WRT-2 is used formedium- and long-range communications.

Transmitter-Receiver AN/SRC-23(V)The AN/SRC-23(V) (fig. 3-3) is a single

channel HF transmitter-receiver communica-tions system which operates in the 2-30 MHzrange. The transmitter-receiver is automat-ically tuned and capable of local or remotecontrol in either simplex or duplex modes ofoperation for AM, CW, USB, LSB, ISB, AFTS,voice, or data. The equipment has a 1 KWpower output; however, an alternate 5 KW RFpower output may be obtained using a 5 KWlinear power amplifier.

Designed especially for shipboard installa-tions, this transmitter-receiver group may alsobe used for shore-base installations and consistsof eight basic units located within a cabinet.

The front panel of the transmitter controlunit (fig. 3-3) provides the controls for man-ually selecting the modes of operation for thetransmitter and amplifier group.

36-


FREQUENCYSELECTORCONTROL

TRANSMITTERCONTROL

The receiver control unit provides controlsfor operating the receiver.

The frequency selector control unit providesthe selector switches for selecting the desiredoperating frequency for the transmitter andreceiver units.

The radiofrequency amplifier unit receivesRECEIVER the signal from the transmitter and amplifiesCONTROL yak it to 1,000 watts.FREQUENCY The frequency standard unit is optionalSTANDARD equipment, which may be installed in the cab-(OPTIONAL) inet when external frequency standard equip-

ment is not supplied. It provides an un-modulated 100-1-Ez output frequency used forcalibrating the radio transmitter and receiver.In case of power failure, an internal 28 VDCbattery in this unit will automatically supply

RADIO power for two hours.The electrical equipment cabinet provides

mounting space for all of the functional unitsand other equipment, such as a heat exchangerand blower for cooling the system, patch term-inal strips, thermal alarm indicators, a warn-ing panel, primary power circuit breaker, andinterconnection system components.

The equipment is completely transistorizedexcept for the use of two electron tubes. A

ELECTRICALEQUIPMENT frequency-synthesizer provides transmitter-CABINET receiver frequencies separated at 500 hertz

intervals across the band.The AN/SRC-23(V) is a single-channel ver-

120.64 sion of the four-channel service test NTDSFigure 3-3. Radio- Transmitter- receiver (Naval Tactical Data System) AN/SRC-16,

AN/SRC-23(V). covered later in the chapter.

RADIORECEIVER

TRANSMITTER

RADIOFREQUENCYAMPLIFIER

NECEIVoi TRANSMITTER

76.22Figure 3-4.Radio Transmitter-receiver Model TCS-( ).

32

3,'

Chapter 3RADIO EQUIPMENT

Transmitter-Receiver Model TCS-( )The model TCS-( ), (fig. 3-4) is a small

transmitter-receiver that has been in use formany years for short-range communications.It has an output power of 10 watts for radio-telephone and 25 watts for CW. The TCS-( )has a frequency range of 1.5 to 12 MHz. Itsfrequency-determining section may be eithercrystal-controlled or tuned by a continuouslyvariable oscillator, whichever is more desir-able. Transmitter and receiver use the sameantenna, which is switched from receiver totransmitter by a relay when the transmitteris keyed. Although it is being replaced bythe AN/URC-35, the TCS-( ) is still usedaboard ships of many types.

Transmitter-Receiver AN/WRC-1 ( )

Another radio set that covers the frequencyrange 2 to 30 MHz is the AN/WRC-1( ) trans-mitter-receiver (fig. 3-5). It has a maximumpower output of 100 watts, and is capable oftransmission and reception on upper sideband,lower sideband, continuous wave, amplitudemodulation, radioteletype, and independent side-band modes of operation.

An outstanding feature of the AN/WRC-1( )is that it has an automatic antenna tuning sys-tem. This system automatically tunes theantenna to the transmitter's output frequency,thereby assuring maximum transfer of power

RF AMPLIFIER----

RADIO .

TRANSMITTER

RADIORECEIVER --R-1051/URR

SHOCK MOUNT

76.61Figure 3-5.Radio Transmitter-receiver

AN/WRC-1.

33

at all times. Manual controls are provided forfine tuning for maximum power output.

Transmitter AN/URT-24

When the receiver unit is removed fromthe AN/WRC-1( ) transmitter-receiver theremaining units form the AN/URT-24 trans-mitter. When used as an AN/URT-24, the toptwo units in figure 3-5 (RF amplifier and radiotransmitter) are seated directly on the shockmount, thus eliminating the receiver unit.

The transmitter is used for short rangecommunications.

Transmitter AN/UR T- 23(V)

The AN/URT-23(V) is a long and mediumrange transmitter which operates as a 1 KWsingle-sideband transmitter (fig. 3-6). The

E

'37

120.65Figure 3-6.Radio Transmitter AN/URT-23(V)

(with 60 hertz power supply).


RAOIO SET CONTROL

HANDSET

ANTENNACOUPLER

35 FOOTWHIP ANTENNA

ACCESSORY UNIT:USEO FOR SURFACESHIP AND SHOREINSTALLATIONS

ANTENNACOUPLERCONTROL

TRANSMITTERSWITCittiOARD

.IADIOTRANSMITTER

HANDSET

KEY

TELETYPEWRITERCONTROL PANEL

TELETYPEWRITER POWERSUPPLY

0co

TELETYPEWRITERPANEL

POWERSUPPLY

TELETYPEWRITER HEADSET RECEIVERSHOCK MOUNT

120.66Figure 3-7.A complete communications system for Radio Transmitter AN/URT-23(V).

normal configuration provides voice, contin-uous wave, and radio teletypewriter transmis-sions in the 2-30 MHz frequency range. Afrequency standard (either internal or external),with crystal-controlled synthesizers is used forfrequency control. The transmitter is equippedto provide automatic (digital) tuning to the cor-rect frequency within a frequency band. Twooptional power supply equipments permit theuse of any one of three, 3-phase primarypower sources: 115 volts line-to-line 400hertz or 208 or 440 volts line-to-line 60hertz.

The major units of the AN/URT-23(V) maybe stack or rack mounted for installationaboard ship or for shore installations to forma complete communications system as illus-trated in figure 3-7.

34

Transceiver AN/URC-58(V)

The AN/URC-58(V) radio set (fig. 3-8) isa single sideband (SSB) transceiver for gen-eral-purpose voice and CW communicationsand may be used for ship and shore fixed in-stallations, semiportable applications such asin vehicles, and amphibious landing craft, andfor use aboard ship.

The radio set operates in the 2 to 15 MHzfrequency range and provides transmission andreception on single sideband (3electable upperand lower sideband), CW and AM (compatible)signals. This equipment operates from anominal primary power input of 115/230 volts,50 to 60 hertz, single phase and either 12 or24 VDC power, providing a power output of

Chapter 3RADIO EQUIPMENTS

Figure 3-8.Radio Transceiver AN/URC-58(V).

100 watts. Audio and keying facilities areprovided for both local and remote operation.The transceiver is a triple-conversion super-heterodyne receiver and transmitter tunableover the entire frequency range in 1 kHzincrements.

Transceiver AN/URC-32B

Radio Transceiver AN/URC-32B (fig. 3-9)is a manually operated radio communicationequipment for operating in the 2 to 30 MHz(high-frequency) range. With a power outputof 500 watts, this transceiver is capable oftransmitting signals over long distances. Itis designed for single-sideband transmissionand reception on upper sideband, lower side-band, or the two independent sidebands simul-taneously, with separate AF and IF channelsfor each sideband. In addition to SSB opera-tion, provisions are included for compatibleAM (carrier plus upper sideband), CW, ortone-shift keying (AFTS). The AFTS mode ofoperation is used for sending radioteletype(RATT) and facsimile (FAX) signals.

35

,39

120.6'7

The frequency range of 2 to 30 MHz iscovered in four bands. The desired operatingfrequency in kHz is tunable in 100 Hz incre-ments on a direct-reading frequency counter.Frequency accuracy and stability are con-trolled by a self-contained frequency standard.Provisions are also made for using an externalfrequency standard.

Because of its versatility and power, theAN/URC-32B is installed on most Navy shipshaving a requirement for communicating overlong distances. It is being replaced by theAN/URT-23.

Transceiver AN/URC-35

Designed primarily for mobile operations,the AN/URC-35 (fig. 3-10) has continuous wavetransmitting capabilities, but is used chieflyfor voice communications over short andmedium distances. These portable sets arefound aboard vehicular and small surface craft,and aboard regular Navy ships for emergencyuse.


ANTENNANETWORK

(ACCESSORY)

DYNAMICHANDSET

RACK

CW AND AFTSUNIT

HIGH-VOLTAGEPOWER SUPPLY

N(1/4

LOW-VOLTAGEPOWER SUPPLY

JUNCTIONBOX

POWERAMPLIFIER

FREQUENCYGENERATOR

SIDEBANDGENERATOR

AUDIO ANDCONTROL

FREQUENCYCOMPARATOR

HANDSETADAPTER

BLOWER

32.135Figure 3-9.Radio Transceiver

AN /URC -32B.

The AN/URC-35 is a general-purpose HFradio set for transmitting and receiving SSB,AM, and CW signals in the 2 to 30 MHzspectrum.

The receiver and transmitter are automat-ically tuned to the same frequency at all timesby common electronic assemblies. All com-ponents in the electronic assemblies are trans-istorized, except the RF amplifiers.

Optional power requirements are met byeither internal or external 28 VDC batterysupply or by 115 VAC. Three different an-tennas may be employed: a 15-foot probe or


AN/URC-;s5.

whip, a 25-foot whip, or a 35-foot whip typeantenna.

Transmitter-Receiver AN/SRC-16

Communications central AN/SRC-16 (fig.3-11) is a shipboard, single-sideband com-munications system with a frequency range of2 to 30 MHz. In addition to the normal voice,CW, and AFTS communications, the system pro-vides high-frequency reception and transmis-sion for terminal equipment such as HCCS(high-capacity communications system) andNTDS (Navy Tactical Data System). The sys-tem uses dual single-sideband equipment andboth sidebands are available for use inde-pendently for either voice or multitone signals.The system operates on four independent chan-nels, each channel consisting of a single-sideband receiver, a single-sideband trans-mitter (exciter), and a 500-watt PEP linearpower amplifier. The frequency of each re-ceiver and transmitter is phase locked to asystem primary frequency standard.

Two transmitters, two receivers, one poweramplifier, and one frequency standard are lo-cated in each of the two cabinets in the com-munications central (fig, 3-11).

36

40


COMMUNICATIONS CENTRAL CONTROL

1,

r-

RADIO FREQUENCY AMPLIFIER ANTENNA COUPLER GROUP

I

Gib is

. Zle

705:: :

RADIO RECEIVER - TRANSMITTEREXCITER ) ANTENNA COUPLER CONTROL ANTENNA COUPLER GROUP

Figure 3-11.Communications Central AN/SRC-16 (doors open).

VHF TRANSMITTERS

Transmissions in the VHF range normallyare restricted to line-of-sight distances. Undercertain atmospheric conditions, they have beenreceived at considerably longer distances-500miles or more.

Shipboard installations of VHF equipmentsare retained for emergency communications,and for communication with allied forces thathave not yet converted to UHF equipments. TheVHF equipment is also being used as a backupto UHF equipment.

Tranceiver AN/VRC-46

The AN/VRC-46 transceiver (fig. 3-12) wasdeveloped for Signal Corps use, but has beenadopted for shipboard and amphibious navalgun fire support and joint communicationswith tactical Army and Marine Units ashore.

The AN/VRC-46 is a narrow-band FM trans-ceiver capable of 24 VDC or 115 VAC opera-tion in the 30 to 76 MHz (very high frequency)range. It is used for short-range, two-wayradiotelephone communications. It replacesthe older AN/SRC-10 through -15 wideband FMtransceivers.

37

120.69

120.70Figure 3-12.Radio Transceiver AN /VRC -46.

Transmitter AN/URT-7( )

The AN/URT-7( ) (fig. 3-13) is a crystal-controlled VHF transmitter that operates inthe frequency range 115 to 156 MHz. Al-though mountings for four crystals are pro-vided, permitting rapid selection of any oneof four frequencies, the transmitter must beretuned each time the frequency is changed.


32.40Figure 3-13.Radio Transmitter AN/URT-7( ).

With a power output of 30 watts, this equip-ment provides two modes of operation: radio-telephone and MCW.

UHF TRANSMITTERS

Most UHF radio transmitters (and receivers)used by the Navy operate in the 225- to 400 -MHz frequency range. Actually, this range offrequencies covers portions of both the VHFband and the UHF band. For convenience,however, radio equipments operating withinthis frequency range are considered to be UHFequipments.

The effective range of UHF normally islimited to line of sight distances, however,under certain atmospheric conditions UHF hasbeen received at considerably longer distances500 miles or more.

Transmitter Model TED

The model TED is a crystal-controlled,single-channel, UHF transmitter that operatesin the frequency range 225 to 400 MHz. Thistransmitter is similar to the VHF transmitterAN/URT-7 described earlier and illustratedin figure 3-12.

Transmitter-Receiver AN/GRC-27A

The AN/GRC-27A (fig. 3-14) is a UHFtransmitter-receiver set covering frequenciesfrom 225 to 400 MHz. This equipment isused for radiotelephone and MCW communica-tions from ship-to-ship, ship-to-shore, or withaircraft. The AN/GRC-27A is installed prin-cipally in carriers and antisubmarine war-fare ships, whose primary missions involvethe control of aircraft.

The transmitter has a power output of100 watts. It has three crystal-controlled

RF CABLE TOANTENNA

CONTROL ANUj AUDIO CABLES

TO SWITCHBOARD

CONTROLRADIO SET

DISTRIBUTIONPANEL

RADIO RECEIVER

RADIO TRANSMITTER

MODULATORPOWER SUPPLY

The TED has an output power of 15 watts. 32.109.2An RF power amplifier (AM-1365/URT, not Figure 3-14.Radio Transmitter-receivershown) boosts the output power to 100 watts. AN/GRC-27A.

38

*az


oscillators, using a total of 38 crystals. Thesecrystals, located within the transmitter, do notrequire handling by the cperator. From thecombination and multiplication of these 38crystal frequencies are produced 1750 fre-quencies spaced at 100 kHz intervals through-out the transmitter's frequency range. Any10 of these 1750 frequencies can be presetmanually with selector switch dials. Of the10 preset frequencies, one then can be selectedautomatically by a telephone-type dial. Theautomatic selection can be made either locallyat the transmitter or from a remote unit atother locations, su,:th as CIC and the bridge.Only 2 to 7 seconds are required to shift auto-matically from one channel to another in anyof the 10 preset channels.

The receiver also operates on any of the1750 channels. It is a triple-conversion super-heterodyne and has crystal oscillators using 38crystals in a system separate from but similarto that used in the transmitter. Here, again,automatic shifting of channels is done in about2 to 7 seconds.

Both transmitter and receiver normally usethe same antenna. A relay switches the antennafrom one to the other.

Radio Transceiver Sets AN/URC-9( ),AN/SRC-20( ), -21( )

Radio set AN/URC-9( ), used separately(fig. 3-15) is a UHF transceiver that providesfacilities for AM radiotelephone communica-tions in the frequency range 225 to 400 kHz.The equipment is crystal-controlled and pro-duces 1750 frequencies at 100 kHz intervalswithin its frequency range. Although it iscapable of operating on only one frequency ata time, any 20 of the 1750 available frequenciescan be preset for immediate selection fromremote positions. Channel selection requiresa maximum of 8 seconds. This set has apower output of approximately 20 watts.

When modified by the addition of certainunits (fig. 3-15), the AN/URC-9( ) is redesig-nated either AN/SRC-20( ), (fig. 3-15) or AN/SRC-21( ) (fig. 3-16). These modified setscan be connected to similar sets so that rceived signals are retransmitted automatically.This feature is useful when a ship (or air-craft) is serving as a relay station betweentwo stations that cannot communicate with eachother directly.

The difference between the AN/SRC-20( )and the AN/SRC-21( ) is that the AN/SRC-20( )has a linear power amplifier unit that increasesthe 20-watt power output from the AN/URC-9( )to a 100-watt output.

PORTABLE AND PACK RADIOEQUIPMENT

Because portable and pack radio sets mustbe lightweight, compact, and self-contained,they usually are powered by battery or handgenerator, have low output power, and areeither transceivers or transmitter-receivers.Navy ships carry a variety of these radio setsfor emergency and amphibious communications.The numbers and types of this equipment varyaccording to the individual ship.

Transmitter AN/CRT-3A

Radio transmitter AN/CRT-3A, popularlyknown as the "Gibson girl," is a ruggedemergency transmitter carried aboard shipsand aircraft for use in lifeboats and liferafts.It is shown in figure 3-17. No receiving equip-ment is included.

The transmitter operates on the interna-tional distress frequency (500 kHz) and the sur-vival craft communication frequency (8364 kHz).

The complete radio transmitter, including thepower supply, is contained in an aluminumcabinet that is airtight and waterproof. Thecabinet is shaped to fit between the operator'slegs, and has a strap for securing it in theoperating position.

The only operating controls are a three-position selector switch and a pushbutton tele-graph key. A handcrank screws into a sockin the top of the cabinet. The genautomatic keying, and automatichanging are all operated bycrank. While the handthe set automaticasignal SOS inconsists20-

terator,

frequencyturning the hand-

rank is being turned,y transmits the distress

Morse code. The code sequenceof six groups of SOS followed by a

econd dash, transmitted alternately on 500kHz and 8364 kHz. The frequency automaticallychanges every 50 seconds. These signals areintended for reception by two groups of stations,each having distinct rescue functions. Direction-finding stations cooperating in long-range res-cue operations normally make use of 8364kHz, whereas aircraft or ships locally engaged

39

"3


tt.

cNWI.. vet to%.4.w, RADIOFREQUENCY

AMPLIFIER

RADIO SETAN/URC- 9

RADIO SETCONTROL

ELECTRICALEQUIPMENT

RACK

50.160Figure 3-15.Radio Transceiver AN/SRC-20.

40


RADIO SETAN/URC-9

ELECTRICALEQUIPMENT RACK RADIO SET

CONTROL

50.161Figure 3-16.Radio Transceiver AN/SRC-21.

in search and rescue missions make use ofthe 500 kHz signals.

Besides the automatic feature, the trans-mitter can be keyed manually, on 500 kHz only,by means of the pushbutton telegraph key.

Additional items (not shown) packaged withthe transmitter include the antenna, a box kiteand balloons for supporting the antenna, hydro-gen-generating chemicals for inflating the bal-loons, and a signal lamp that can be poweredby the handcrank generator.

The equipment floats, and is painted brilliantorange-yellow to porovide greatest visibilityagainst dark backgrounds.

Transceiver SCR-536( )

Radio transceiver SCR-536( ), (fig. 3-18)is a low-power, battery-operated transceiverused for voice communication over very shortdistances (1 to 3 miles). The equipment iscrystal-controlled, and operates on a presetfrequency in the range of 3.5 to 6 megahertz.The operating frequency is varied by changingthe crystal and certain other frequency-de-termining components within the set. Usually,these changes are made by a technician.

The set is energized by extending the tele-scopic antenna. When thus energized, it func-tions as a receiver. Applying pressure on thepress-to-talk switch (located on the side of theset) shifts the equipment from a receive con-dition to a transmit condition. The set remainsin the transmit condition as long as the switchis held depressed.

Weighing only 5-1/2 pounds, this portableset comes equipped with a carrying strap.Often the set is used as a means of com-munication by personnel moving about on foot,as while on shore patrol. Also, it serves asa means of communication between small boatsand their parent ships.

Transceiver AN/PRC-10( )

The AN/PRC-10( ) portable radio set (notillustrated) provide voice communications foramphibious operations. These are man-packFM equipment sets.

Total frequency coverage of the AN/PRC-10( ) is between 38 and 54.9 MHz with an

76.32 output power of approximately 1 watt. TheseFigure 3-17.Emergency lifeboat Radio portable sets have an effective range of ap-

Transmitter AN/CRT-3A. proximately 5 miles.

41


I

4,1

120.'7Figure 3-18.Radio Transceiver SCR-536( ).

Transceiver AN/PRC -25

The AN/PRC-25 is a VHF man-pack min-iaturized radio set (fig. 3-19) now being used.It weights only 22 pounds with batteries, andreplaces three sets (AN/ PRC-8-9-10) that covera frequency range of 20 to 55 megahertz. TheAN/PRC-25 is an FM transceiver that operatesin the 30- to 76-megahertz range and provides920 channels spaced at 50 kilohertz intervals,with a power output of 2 watts. Stable fre-quencies are generated for both the transmitterand receiver by a frequency synthesizer.

The unit is transistorized throughout, withthe exception of one tube in the transmitterpower output stage. A future version will becompletely solid state. With 25 modular plug-insubassemblies, the set is easy to service.

Transceiver AN/URC-4( )

The AN/URC-4( ) (fig. 3-20) is a compact,portable transceiver. It is small enough toallow the combined transmitter and receiver tobe grasped and held with one hand. This unitis connected by a short cable to its batterycase, which is approximately the size of thetransceiver.

The complete set is intended to be carriedin a special vest type garment worn by airmenwhile they are on flight missions. It also maybe dropped by parachute to personnel in distress.

42

go


AN/PRC-25.


JAN WNWBA- 1260

No

0ITe OP MOOMR MI

I. a leAltoore a COW

TNIAPVTONN. NY

No No....N.-N.MAL."

120.6Figure 3-20.Radio Transceiver AN/URC-4( ).

The principal use of this set in the Navy isfor extremely short-distance distress com-munication between lifeboats (or liferafts) andsearching rescue aircraft or ships.

This transceiver is a crystal-controlledequipment that provides voice and MCW trans-missions over two frequency ranges within theVHF band. Frequencies covered are between120 and 130 MHz and between 240 and 260MHz. The operating frequency of the set isdetermined by a single crystal, which must bechanged each time the frequency is changed. Theset is pretuned, and can be operated by anyonefamiliar with its purpose.

Transceiver AN/PRC-41

Radio set AN/PRC-41 (fig. 3-21) is a water-tight, lightweight, purtable UHF equipment thatmay be operated on any of 1750 channels spaced100 kHz apart in the 225- to 400 MHz range.Its only mode of operation is AM voice, whichit supplies at an average output power of 3watts. Although designed principally for man-pack operation, the set also may be used forfixed station and vehicular operation when com-plemented by certain accessories. When not inuse, the equipment is disassembled and stowedin a compartmentized aluminum transit casesimilar to an ordinary suitcase.

43

HAt:L.SET

RUCKSACKFRAME

RADIO

STORAGE BATTERY

120.5Figure 3-21 . Radio Transceiver AN/ FRC -41.

RECEIVERS

Modern Navy radio receivers are easy tooperate and maintain. They are capable ofreceiving several types of signals and can betuned accurately over a wide range of fre-quencies. Because they are not required toproduce or handle large currents and voltages,their size is relatively small when comparedto the size of most transmitters.

Unlike the receiving units of the trans-ceivers described earlier, the radio receiversdiscussed in this section are separate equip-ments that are capable of independent operation.

Receivers with radioteletype capabilitiesare able to copy either radiofrequency carriershift or audiofrequency tone shift radioteletypetransmission information.

VLF, LF, MF, AND HF RECEIVERS

Most radio receivers operating in the VLF,LF, MF, and HFbands of the frequency spectrum


are of the continuous tuning type. They aretunable to any frequency within their frequencyrange, and they usually cover this range inseveral tuning bands. Switching from one bandto another changes the receiver's frequency-determining components, permitting more ac-curate tuning than is possible if the entirefrequency range were covered by a single setof components.

Radio Receiver AN/BRR-3

Radio receiving set AN/BRR-3 consists ofradio receiver R-988/BRR-3, connectors,clamps, and mounting hardware. The receiveris designed for general application aboard alltypes of U. S. Navy vessels. It covers the fre-quency range from 14 to 30 kHz and is normallyused to receive either on-off keying (ICW orAl) or radioteletype (RFCS or AFTS) typesof transmission. The receiver also has thecapabilities of receiving facsimile signals (FAXor F4) when provided with additional terminalequipment, and of being used as a homing de-vice when equipped with a Loop Antenna. Itis a superheterodyne receiver, the output ofwhich is supplied at a headphone jack for audiomonitoring of Interrupted Continuous Wave (ICW)signals. Figure 3-22 shows the radio receiv-ing set and accessory equipment.

Radio Receiver AN/SRR-19A

The AN/SRR-19A is a low frequency multi-channel shipboard radio receiver for the 30-300 kHz frequency range (fig. 3-23). Thisdual-conversion superheterodyne receiver isintended for single sideband, multichannel radioteletypewriter broadcasts, AM and CW recep-tion.

Receiver operation is characterized by ex-treme stability, permitting long periods of un-attended operation. Counter type tuning dialsfacilitate accurate tuning to a desired frequency,and frequency errors caused by drift in thelocal oscillators are removed by drift-cancel-lation circuits. The receiver can be incre-mentally tuned in steps of 10 hertz or con-tinually tuned (between increments) with partialdrift-cancellation during continuous tuning.

Radio Receiver AN/SRR-11

Radio receiver AN/SRR-11 (fig. 3-24) is amodern communication receiver used in all

types of Navy ships. The frequency range isdivided into five bands from 14 to 600 kilo-hertz.

The AN/SRR-11 receiver is used for moni-toring low and medium frequencies, such asthe international distress frequency (500 hertz).Its most general use, however, is for receivingthe VLF and LF transmissions of the fleetbroadcasts. This receiver can be used forCW, MCW, and AFTS or RFCSRATT and FAXreception.

44

Radio Receiver RBA

The RBA receiver (fig. 3-25) has been usedfor many years aboard ship. Although beingreplaced, many of these old receivers are stillin service. The frequency coverage of the RBAis 15 to 600 kHz.

The RBA is a TRF (tuned radiofrequency)receiver. The receiver may be used for CW,MCW, and voice signals, but because of itshigh selectivity, the RBA is not recommendedfor radiotelephone use. Most RBA receiverscan receive radioteletype and facsimile signalsalso. The receiver has high sensitivity andgood selectivity. As shown in figure 3-25, thepower supply is a separate unit from thereceiver.

Radio Receiver AN/WRR-3B

Radio receiver AN/WRR-3B (fig. 3-26) is adual-conversion superheterodyne receiver forsurface craft and submarine installations. Itreceives CW, MCW, and radioteletype signals.

The receiver covers the frequency rangefrom 14 to 600 kilohertz in five bands. Theya re

Band 1, 14 to 30 kHzBand 2, 30 to 63 kHzBand 3, 63 to 133 kHzBand 4, 133 to 283 kHzBand 5, 283 to 600 kHz

The frequency to which the receiver istuned is read directly from drum type dials.

An internal calibration circuit provides cali-bration points at each 10 kHz tuning pointwithin the tuning range of the receiver.

Radio Receiver AN/WRR-2B

Another shipboard radio receiver for useover the MF/HF bands is the AN/WRR-2B


WHIPANTENNA LOOP ANTENNA

)105/115/125V 50-60 H2)SUPPLY 120 WATTS

RADIO RECEIVING SETAN/BRR-3

HEADSET TELEPRINTER 110 V DC

Figure 3-22.Radio Receiving Set AN/BRR-3 and accessory equipment.

10

ism

4- I

,7712-1

Figure 3-23.Radio Receiver AN/SRR-19A.

45

120.72

120.73


(fig. 3-27). The same receiver, with rackmounting for shore station use, is called AN/FRR-59.

The AN/WRR-2B is a triple-conversionsuperheterodyne receiver. It covers the fre-quency range 2 to 32 MHz. This modern

In order to meet strict frequency toler-ances, a frequency standard, having a lowfrequency and very stable oscillator, generatesa very accurate fundamental frequency (andharmonics) to provide frequency reference checkpoints throughout the 2 to 32 MHz frequency

Figure 3-24.--Radio Receiver AN/SRR-11.

receiver is intended primarily for the recep-tion of single-sideband transmissions with fullcarrier suppression. It can be used also toreceive conventional amplitude-modulated sig-nals of various types, including CW, MCW,voice, facsimile, and radioteletype.

Jut

POWER SUPPLY

1.157

range. This facilitates accurate tuning and ahigh degree of stability over long periods ofoperation. Both upper and lower sideband chan-nels can be used simultaneously for receivingtwo different channels of intelligence or to re-ceive the same intelligence.

RECEIVER

34.17Figure 3-25.Radio Receiver RBA with power supply.

46

%.5.6


interpolation oscillator, each 0.5 kHz incrementis scanned either continuously or in 1 kHz steps.Counter type tuning dials permit accurate pre-setting to any desired frequency.

The frequency range of 2 to 32 MHz is coveredin four bands: band 1, 2.0 to 4.0 MHz; band2, 4.0 to 8.0 MHz; band 3, 8.0 to 16.0 MHz;and band 4, 16.0 to 32.0 MHz.

Radio Receiver AN/URR-44

The AN/URR-44 (fig. 3-28) is an eleven tubesuperheterodyne type radio receiving set de-signed for use aboard all types of naval surfaceships and at naval shore stations. The receiveris designed for voice modulated signal recep-tion on standard broadcast and shortwave bands

76.26 within the frequency range of 540 kHz to 16.6Figure 3-26.Radio Receiver AN/WRR-3B. MHz.

50.40Figure 3-27.Radio Receiver AN/WRR-2B.

Other features of the receiver also con-tribute to its high performance. Any error infrequency resulting from drift in the localoscillator is removed before the last conversionby a drift-canceling circuit. Receiver tuningis in 0.5 kHz steps. Through the use of an

47

Radio Receiver R-390A/URR

Operating in the frequency range 500 kHzto 32 MHz, radio receiver R-390A/URR (fig.3-29) is a high-performance receiver for bothshipboard and shore station use. It can receiveCW, MCW, AM, radiotelephone, radioteletype,and facsimile signals.

The receiver is a superheterodyne type,with multiple-frequency conversion. In thefrequency range from 500 kHz to 8 MHz, ituses triple conversion. Double conversion isused in the range from 8 to 32 MHz.

The tuning knob turns an arrangement ofgears and shafts to select the frequency towhich the receiver is tuned. A counter type

AF LEVEL

LOUDSPEAKER LOCK TUNINGDIAL

MAIN TUNING

MONITORLEVEL BAND

SELECTOR

DIALLAMP

POWERONOFF

MONITOR- PHONEPHONES JACK FIDELITY

RA010EXTERNAL AU010

120.74Figure 3-28.Radio Receiver AN/URR-44.


superheterodyne receiver capable of receivingany type of radio signal in the frequency range2 to 30 MHz. It can be used as an independentreceiver, or, in conjunction with a transmitter,it can be used to form a transmitter-receivercombination, similar to the Radio Set AN/WRC-1( ) described earlier.

Basically a c rystal-controlled equipment, theR-1051B/URR uses a digital tuning scheme.An additional fine tuning control provides con-tinuous tuning between 100 kHz increments.This receiver utilizes printed circuit boardsand is completely transistorized, except for RFamplifier tubes. It is designated as standardequipment for use aboard all ships.

34.15 VHF AND UHF RECEIVERSFigure 3-29.Radio Receiver R-390A/URR.

frequency indicator dial is provided. The dialis calibrated in kilohertz.

Radio Receiver R-1051B/URR

The R-1051B/URR (fig. 3-30) is one of thenewer radio receivers. It is a versatile

MEL

In most instances, radio receivers coveringthe VHF (and UHF) range are operated ascrystal-controlled equipments. They are tunedeasily and quickly. Once tuned, they operateefficiently for long periods of time withoutfurther attention. The trend is that moderntransceivers will probably be replacing moreradio receivers of this frequency range in thefuture.

=M. MA

Figure 3-30.Radio Receiver R-1051B/URR.

48

Jd

120.8


Radio Receiver AN/URR-21( )

The AN/URR-21( ) receiver (fig. 3-31) isused for receiving amplitude-modulated radio-telephone signals, in a portion of the VHFband, from 115 to 156 MHz. It is a crystal-controlled superheterodyne receiver. Althoughthe receiver dial is calibrated continuously,only four channels can be tuned within thefrequency range for a given set of four in-dividually selectable crystals. The four crystalsare plugged into a crystal holder on the re-ceiver chassis inside the cabinet. Specialfeatures include a front panel dial detent mech-anism for rapid selection of channels, and con-tinuous tuning of all RF circuits by means ofa single tuning control.

Radio Receiver AN/URR-27( )

Radio receiving set AN/URR-27 (fig. 3-32)provides for reception of amplitude-modulatedvoice and MCW transmission in the 105 to 190MHz frequency range. You will note that thisrange of frequencies slightly exceeds that ofthe VHF transmitters, which cover a band from115 to 156 MHz.

The AN/URR-27( ) is a superheterodynereceiver, designed chiefly for operation as apretuned, single-channel, crystal-controlled re-ceiver. Continuously variable manual tuningis also available. A single tuning control isused for tuning to any freqw icy for eithercrystal-controlled or manual tviing operation.

32.56Figure 3-31.Radio Receiver AN/URR-21( ).

32.42Figure 3-32.Radio Receiver AN/URR-27( ).

Radio Receiver AN/URR-35C

Radio receiver AN/URR-35C (fig. 3-33) isequipped for radiotelephone and MCW receptionfor use in tactical communications aboard ship.Although the frequency range of 225 to 400 MHzincludes the upper portion of the VHF band,the receiver is commonly called UHF equip-ment. Designed mainly for single channel,crystal-controlled operation, it may also be usedas a continuously variable manual tuned re-ceiver. This receiver is easy to tune andfeatures single tuning controls for tuning toany frequency within its range, for eithercrystal-controlled or manual tuning. It is adouble conversion, pretuned, single-channel,superheterodyne receiver.

The AN/URR-35C receiver is commonlyemployed with the TED transmitter. This com-bination is commonly referred to by operatorsand technicians as a TED/RED group.

49

J:5

SHIPBOARD ANTENNAS

Antennas used for radio communicationsare so varied in design that it is impracticalto describe every antenna you may encounteraboard ship. Consequently, this section dealsmainly with the use and physical appearanceof some of the more common shipboard com-munication antennas. Any technical discussionof antenna theory is avoided, when possible.To understand why a particular antenna issuited for use at one frequency (or range offrequencies), yet is unsuited for others, youmust have a knowledge of the relationship


Figure 3-33.Radio Receiver AN/URR-35C.

between an antenna's length and the frequencyat which it is radiating.

The strength of the radio wave radiated byan antenna depends on the length of the antennaand the amount of current flowing in it. Be-cause the antenna is a circuit element havinginductance, capacitance, and resistance, thelargest current is obtained when the inductiveand capacitive reactances (opposition to theflow of alternating current) are tuned out; thatis, when the antenna circuit is made resonantat the frequency being transmitted.

The shortest length of wire that will beresonant at any particular frequency is onejust long enough to permit an electric chargeto travel from one end of the wire to theother end and back again in the time of onecycle. The distance traveled by the chargeis one wavelength. Because the charge musttravel the length of the wire twice, the lengthof wire needed to have the charge travel onewavelength in one cycle is half a wavelength.Thus, the halfway antenna, sometimes calleda dipole, doublet, or Hertz is the shortestresonant length and is used as the basis formost antenna theory.

An antenna can be made resonant by twomethods: (1) adjusting the frequency to suita given antenna length; or, as usually is morepracticable, (2) adjusting the length of theantenna wire to accommodate a given frequency.

50

32.45

Every time the transmitter is changed to a newfrequency, it is, of course, impractical tolengthen or shorten an antenna physically. Theantenna length may be changed electrically,however, by a process known as tuning, orloading, the antenna.

The dipolea center-fed, half-wave antennais the basis for many complex antennas.When used for transmitting high frequencies,it usually is constructed of wire. At veryhigh and ultrahigh frequencies, the shorterwavelength permits construction with metal rodsor tubing. Because the dipole is an un-grounded antenna, it may be installed farabove the ground or other absorbing structures.

At low and medium frequencies (below MHz),half-wave antennas are rather long for useaboard ship. Another basic type of antenna,however, affords a solution to the problem ofundue length. It is the quarter-wave (Marconi)antenna.

The earth is a fairly good conductor formedium and low frequencies, and acts as alarge mirror for the radiated energy. Theresult is that the ground reflects a largeamount of energy that is radiated downwardfrom an antenna mounted over it. It is as thougha mirror image of the antenna is produced,the image being located the same distance belowthe surface of the ground as the actual antennais located above it. Even in high-frequency


range (and higher), many ground reflections oc-cur, especially if the antenna is erected overhighly conducting earth or salt water.

Utilizing this characteristic of the ground,an antenna only a quarter-wavelength long canbe made into the equivalent of a half-waveantenna. If such an antenna is erected verti-cally and its lower end is connected electricallyto the ground, the quarter-wave antenna behaveslike a half-wave antenna. Here, the groundtakes the place of the missing quarter-wave-length, and the reflections supply that part ofthe radiated energy that normally would besupplied by the lower half of an ungroundedhalf-wave antenna.

Another method of operating a verticalquarter-wave antenna is to use a ground planewith the antenna. The ground plane usuallyis made of wires or rods extending radiallyfrom the base of the antenna. Actually, theground plane substitutes for the ground con-nection, thereby establishing the ground levelat the base of the antenna. Thus, the antennacan be installed on masts or towers high aboveground. Ground plane antennas of this sortare used mostly for VHF and UFH communi-cations.

Although discussions of antennas ordinarilyconcern those used for transmitting, an efficienttransmitting antenna for any particular fre-quency is also an efficient receiving antennafor that same frequency. It must be remem-bered, however, that there may be other limi-tations affecting the use of an antenna for bothtransmitting and receiving.

Problems not usually present in land in-stallations arise when antennas are installedon board ship. Most of the masts, stacks,and other structures above decks are connectedelectrically (grounded) to the ship's hull and,through the hull, to the water. To obtainadequate coverage from the antenna, it mustbe installed so that minimum distortion ofthe radiation pattern results from groundedstructures.

The antennas described in the next sixtopics are only a sampling of the antennasused in the Navy. They are typical of theantennas you can expect to find installed aboardmost Navy ships.

WIRE ANTENNAS

Wire antennas (fig. 3-34) are installed onboard ship for medium- and high-frequency

51

BRACKET

I SULATORS

ANTTUNER

ATRANSMITTING

ANTENNA

BRECEIVINGANTENNA

ENTRANCEINSULATOR

1.46Figure 3 -34.Shipboard wire antennas.

coverage. Normally, they are not cut for agiven frequency. Instead, a wire rope isstrung either vertically or horizontally from ayardarm (or the mast itself) to outriggers, an-other mast, or to the superstructure. If usedfor transmitting, the wire antenna is tunedelectrically to the desired frequency.

Receiving wire antennas usually are in-stalled forward on the ship, rising nearly verti-cally from the pilothouse top to brackets on themast or yardarm. They are located as faras possible from the transmitting antennas sothat a minimum of energy is picked up fromthe local transmitters. The transmission line(lead-in) for each receiving antenna termi-nates in antenna transfer panels in the radiospaces.

Transmission lines of the transmitting an-tenna may be of coaxial cable or copper tubing.They are supported on standoff insulators andin some instances, are enclosed in rectangularmetal ducts called antenna trunks. Each trans-mission line connects with an individual trans-mitter or with an antenna multicoupler (dis-cussed later).

Metal rings, antenna knife switches, an-tenna hardware, and accessories associated withtransmitting antennas are painted red. Hard-ware and accessories used with receiving an-tennas are painted blue. This color scheme


is a safety precaution, and indicates, at aglance, whether an antenna is used for radiat-ing or receiving.

WHIP ANTENNAS

Whip type antennas have replaced many wireantennas in the frequency range 1.8 to 30 MHz.Because they are essentially self-supporting,whip antennas may be installed in many loca-tions aboard ship. They may be deck-mounted,or they may be mounted on brackets on thestacks or superstructure (fig. 3-35). Whipantennas commonly used aboard ship are 25,28, or 35 feet in length, and are made up ofseveral sections.

On aircraft carriers, whip antennas locatedalong the edges of the flight deck can be tilted.The tilting whip is pivoted on a trunnion, andis equipped with a handle for tilting and erect-ing the antenna. A counterweight at the baseof the antenna is heavy enough to nearly balancethe antenna in any position. The antenna maybe locked in either a vertical or horizontalposition. Where antennas have water drainholes, it is most important to keep them un-plugged during freezing operations.

FOUNDATION

35' WHIPANTENNA

DRAIN HOLE

INSULATOR

LINETERMINATION

BOX

TRANSMISSIONLINE

Figure 3-35.Whip antenna.

FAN ANTENNA

The fan antenna (fig. 3-36) is highly suitablefor shipboard installation. It is known as abroadband antenna since it is capable of radiat-ing over a wide range of frequencies. The fanantenna was designed principally for use inthe low-frequency range, but it also performssatisfactorily in the high-frequency band withproper multicouplers.

The antenna usually consists of four radiat-ing elements (wires) that are cut for one-quarter wavelength at the lowest frequency tobe transmitted. Whether one or all of theseelements are fed energy by the transmitter,the overall effect of the paralleled elementsis to increase the radiating surface. Effec-tively, the fan antenna is a single radiatorwhose diameter is substantially large in com-parison to its length.

SLEEVE ANTENNA

The sleeve antenna (fig. 3-37), originallydeveloped to fill the need for a versatile,long-distance antenna ashore, now is installedaboard many ships. Essentially, the 3lee'reantenna is a grounded, quarter-wave antennathat operates over a wide range of frequenciesin the high-frequency band. Although similarin appearance to the whip antenna, it is identified

INPUT

1.47 25.126Figure 3-36.Fan antenna.

52

6-4


UPPER RADIATOR

INSULATOR

SPECIAL TRANSMISSIONLINE MATCHING SECTION

SLEEVE

TRANSMISSION LINE

DECK

25.217Figure 3-37.Sleeve antenna (shipboard).

easily by the large diameter sleeve at itsbase. The sleeve usually is welded to thedeck or superstructure of the ship.

CONICAL MONOPOLE ANTENNA

Another broadband antenna used extensivelyis the conical monopole shown in figure 3-38.Like the sleeve antenna, it is used both ashoreand aboard ship.

When operating at frequencies near the lowerlimit of the high-frequency band, the conicalradiates in much the same manner as a regu-lar vertical antenna (omnidirectional on thehorizontal plane). At the higher frequenciesthe lower cone section radiates, and the effectof the top section is to push the signal out ata low angle. The low angle of radiation causesthe skywave to return to the earth at greatdistances from the antenna. Hence, the conical

53

monopole antenna is well suited for long-distancecommunication in the high-frequency range.

VHF-UHF ANTENNAS

At VHF and UHF frequencies, the shorterwavelength makes the physical size of theantenna relatively small. Aboard ship theseantennas are installed as high and as much inthe clear as possible.

For best results in the VHF and UHFranges, both transmitting and receiving an-tennas must be mounted on the same plane(vertically or horizontally). Vertically mounted

c3 7

25.214Figure 3-38.--Conical monopole antenna.


antennas are used for all ship-to-ship, ship-to-shore, and air-ground VHF-UHF communica-tions. Usually, either a vertical half-wave dipoleor a vertical quarter-wave antenna with groundplane is used.

The VHF antenna commonly installed aboardships is Navy type 66095, shown in figure 3-39.The horizontal portion of the antenna does notradiate, but acts as a mounting arm for theantenna and as an enclosure for the antennafeedline. The antenna is installed with theradiating portion in the vertical position. Theantenna works with any transmitter and re-ceiver operating in the frequency range 100 to156 MHz.

An antenna frequently used with UHF instal-lations is the AT-150/SRC (fig. 3-40). This

. I-WJ .

94140,A,1""AEI[BK-1

120.10Figure 3-39.VHF antenna NT-66095.

54

MOUNTING ARM

25.219Figure 3-40.UHF Antenna AT-150/SRC.

antenna is of the half-wave (dipole) type, and itcovers the frequency range 225 to 400 MHz.Like the VHF antenna just described, the hori-zontal (longer) section does not radiate, butserves as a mounting arm for the antenna. Theantenna is mounted so that the radiator is verti-cal.

The AS-390/SRC (fig. 3-41) is another UHFantenna that operates at frequencies between225 and 400 MHz. It is a quarter-wave antennawith a ground plane. The ground plane con-sists of a round plate (called a counterpoise)and eight equally spaced drooping radials (rods).The antenna is mounted vertically.

The AS-1018/URC (fig. 3-42) is an addi-tional 225 to 400 MHz antenna often installedaboard ships. This antenna is the UHF versionof the broadband sleeve antenna and is capableof radiating over a wide range of frequencies.The antenna provides essentially a horizon-to-90° overhead, 360° circular radiation pattern.The antenna is vertically polarized and haslower half power points on or below the hori-zon. The vertical upward propagation neededto fill the cone of silence is horizontallypolarized.

The AS-1018/URC consists basically of thepolyester fiberglass 6-foot mast (fig. 3-42A),the two-element colinear dipole array, and theinternal transmission line (fig. 3-42B).

5",


ANTENNA

COUNTERPOISE

RADIALS

CONNECTOR

FOR MOUNTING

25.220Figure 3-41.UHF Antenna AS-390/SRC.

MAST CAP

MAST

SLOTTED DIPOLE(OVERHEAD COVERAGE)

UPPER DIPOLEELEMENT

MAST SPACER (3)

MOUNTINGFLANGE

A EXTERNAL A INTERNAL

LOWER DIPOLEELEMENT

TRANSMISSION LINE

BASE

109.44(120)Figure 3-42.UHF Antenna AS-1018/URC.

AUXILIARY EQUIPMENT

The term "auxiliary" often is misleading,particularly in the field of electronics. Inmost instances, material categorized as aux-iliary equipment is essential to the efficientoperation of an overall system. But, becauseit is subordinate to the primary equipments,

such as transmitters, receivers, and antennas,it is classified as an auxiliary.

Some of the more prominent auxiliary equip-ments used in communication systems are dis-cussed in the ensuing topics of this chapter.

ANTENNA TUNING

Antenna systems are generally not ideal fromthe standpoint of position, efficiency, and an-tenna lengths, because of space limitations andthe crowded conditions which are often charac-teristic of naval vessels. Frequently, a rela-tively short whip antenna may be employed,even for frequencies at the low end of the highfrequency range.

Some transmitters are equipped with tuningdevices which manually or automatically tunethe antenna to the selected transmitter fre-quency. Proper tuning is necessary in orderto obtain maximum transfer of power from thetransmitter to the antenna.

Antenna Coupler AN/SRA-22

The antenna coupler AN/SRA-22 (fig. 3-43)is used for whip and other radio antennas nor-mally encountered aboard ship. It consists ofthe antenna tuner (fig. 3-43A), which is an allweather completely sealed unit mounted near thebase of the antenna, and a remote control (fig.3-43B), which contains all controls and indi-cators for complete operation of the couplerfrom the transmitter rack.

The AN/SRA-22 operates on a 120 VAC, 60hertz power source in the 2 to 30 MHz fre-quency range. This coupler was originallydesigned for the AN/URC-32 transmitter, butmay be used with other transmitters. Beingmanually tuned equipment, it will probably bereplaced by the AN/URA-38 antenna coupler.

Antenna Coupler AN/URA-38

The AN/URA-38 antenna coupler group con-sists of an antenna coupler and an antennacoupler control unit (fig. 3-44). The group isan automatic antenna tuning system intendedprimarily for surface ship and shore use withRadio Transmitting Set AN/URT-23(V). How-ever, the equipment design includes provisionsfor manual and semiautomatic tuning, thus, mak-ing the system readily adaptable for use withother high power radio transmitters in thehigh-frequency range. The manual tuning

55

Si?


A ANTENNA TUNER

iw

B REMOTE CONTROL

120.75Figure 3-43.Antenna Tuning Coupler AN/SRA-22.

4°-

COUPLER CONTROL ANTENNA COUPLER

120.76Figure 3-44.Antenna Tuning Coupler AN/URA-38.

capability is useful if a failure occurs in the (referred to as silent tuning). This method isautomatic tuning circuitry. The AN/URA-38 useful in installations where radio silence mustcan also be tuned without the use of RF power be maintained, except for brief transmission

56


periods. The control signals from the antennacoupler control unit automatically tune theantenna coupler matching network. A low pow-er CW signal is required for tuning.

During manual and silent operation, tuningis accomplished by the radioman operating thecontrols located on the antenna coupler controlunit.

ANTENNA MULTICOUPLERS

Because of the large number of transmittersand receivers on board ships, it is infeasibleto use a separate antenna for each equipment.One satisfactory approach to the problem isprovided by multicouplers.

Antenna multicouplers are devices that per-mit the simultaneous operation of several trans-mitters or receivers into (or from) the sameantenna. The term "multicoupler" is descrip-tive of two or more couplers stacked or groupedtogether to form a single equipment, which thenis connected to a broadband antenna. A separatecoupler is required for each transmitter orreceiver. Normally, the same antenna cannotbe used for both transmitting and receivingsimultaneously unless proper frequency separa-tion and/or a duplexing system is employed.

MulticouplersAN/SRA-13, -14, -15, -16

Four antenna coupler groups that operate inthe MF-HF range are the AN/SRA-13, -14,-15, and -16. They provide complete coverageof frequencies between 2 and 26 MHz. Thefrequency coverage afforded by each multi-coupler is as follows: AN/SRA-13, 2 to 6MHz; AN/SRA-14, 4 to 12 MHz; AN/SRA-15,6 to 18 MHz; and AN/SRA-16, 9 to 26 MHz.

Typical of this group is the AN/SRA-15,which is illustrated in figure 3-45. The fourcouplers comprising the multicoupler providefor the simultaneous operation of four trans-mitters (each with 500-watt power output) intoa single broadband antenna. As long as thereis adequate separation between the operatingfrequencies, the four transmitters connected tothe multicoupler may be operated anywhere inthe frequency range from 6 to 18 MHz. Sep-aration of 10 percent of the highest operatingfrequency is considered sufficient, however,a 15 percent figure provides better power

transfer and decreases the chance of damage tothe equipment in case of temporary malfunction.

Multicoupler AN/SRA-23

Antenna multicoupler AN/SRA-23, (fig. 3-46)consists of three couplers and associated con-trol and blower units. The couplers cover thefrequency range 2 to 27 MHz in three frequencybands. Each coupler operates in a differentband. These bands are 2 to 6 MHz, 5 to 15MHz, and 9 to 27 MHz. The coupler groupwas developed for use with 500-watt trans-mitters, but, with minor adjustments, it iscapable of handling transmitters with 1000 -watt outputs.

One coupler group accommodates only onetransmitter. Provisions are made, however,for connecting up to eight of these groupstogether to form a multicoupler system. Thisarrangement permits the simultaneous operationof eight transmitters into a single broadbandantenna.

57

Multicouplers CU-691/U andCU-692/U

Both the CU-691/U and the CU-692/Uare VHF-UHF multicouplers operating at

FUSEPANEL

ANTENNACOUPLER

6s/

120.11Figure 3-45.Antenna Multicoupler AN/SRA-15.


I

ZCOUPLER

CONTROL

COUPLER

COUPLER

BLOWER

12G.12Figure 3-46.Antenna Multicoupler

AN/SRA-23.

frequencies between 225 and 400 MHz. Exceptfor their physical dimensions and the numberof channels, the two sets are identical. TheCU-691/U provides for the operation of fourtransmitters or receivers, whereas the CU-692/U accommodates only two. Both multicouplersare tuned manually. The CU-691/U is shownin figure 3-47.

Like most VHF-UHF couplers, the perform-ance characteristics of these two types ofcouplers require that operating frequencies onthe common antenna be separated by approxi-mately 15 MHz.

Receiving Multicouplers AN/SRA-12

channels in the frequency range from 14 kHzto 32 MHz. Any or all of these channels maybe used independently of any of the otherchannels, or they may operate simultaneously.Connections to the receivers are made bymeans of coaxial patch cords, which are shortlengths of cable with plugs attached to each end.

A set of nine plug-in type filter subassem-blies is furnished with the equipment, but onlyseven of them may be installed at one time.The seven filters installed are selected to coverthe most-used frequency bands.

TRANSMITTER AND RECEIVERTRANSFER PANELS

Transmitter and receiver transfer panelsare an integral part of every shipboard radiosystem. They make it possible to connect

120.14The AN/SRA-12 (fig. 3-48) filter assembly Figure 3-47.UHF Antenna Multicoupler

multicoupler pfovides seven radiofrequency CU-691/U.

58

6A


L0

TO 14000 KCi

ANTENNA INPUT

'J =7:-. - %!--..

iN 4

TO 7000 KC TO SOO KC TO 300 KC TO TO 14KC

SO co

Figure 3-48.Electrical Filter Assembly AN/SRA-12.

transmitters and receivers to remote controlpoints located throughout the ship. These trans-fer panels formerly were of the cumbersomepatch cord type, but those currently installedaboard ships are of the switchboard type de-scribed here.

Receiver TransferSwitchboard SB-82/SRR

Receiver transfer switchboard, type SB-82SRR, (fig. 3-49) has five vertical rows of tensingle-throw (ON-OFF) switches that are con-tinuously rotatable in either direction. Oneside of each switch within a vertical row iswired in parallel with the same sides of theother nine switches within the row. Similarly,the other side of each switch is wired in par-allel horizontally with the corresponding sidesof each of the other four switches in a hori-zontal row. This method of connecting theswitches permits a high degree of flexibility.

In general, there are more remote stationsthan radio receivers, hence the audio outputsof five receivers are fed to the five verticalrows, and ten remote stations are connectedto the ten horizontal rows. With this ar-rangement, a selected receiver output is con-nected to any or all of the remote stationsby closing the proper switch(es). When oneswitchboard is inadequate for accommodat-ing all of the receivers and remote sta-tions installed in a ship, several of these

59

6S

As-

1.115

36.69Figure 3-49.Receiver Transfer

Switchboard SB-82/SRR.


switchboards are mounted together and inter-connected so that they form a bank of switch-boards.

The knob of each switch is marked with aheavy white line to provide visual indicationof whether the switch is in the ON or OFFposition. Switchboards are always installedwith the line positioned vertically when theswitch is open (off). To further standardizeall installations, receivers usually are connectedto the vertical rows of switches, and remotestations are connected to the horizontal rows.

Identification of the Receivers and remotestations is engraved on the laminated bakelitelabel strips fastened along the top and leftedges of the panel front.

Receiver Transfer SwitchboardSB-973/SRR

A recent model receiver transfer switch-board is the SB-973/SRR (fig. 3-50). Thisswitchboard contains 10 seven-position rotaryselector switches. Each switch or operatingknob relates to a remote control station. Switchpositions one through five relate to receivers.

Position X on each switch serves to trans-fer the remote control stations connected tothe original switchboard to the correspondingswitches in additional switchboards. In thismanner, any one of a number of receivers canbe connected to any of the ten remote controlstations. An additional switchboard is neededfor each five additional receivers.

Switchboards providing facilities for addi-tional remote control stations are mounted invertical sequence, whereas those containingadditional receivers are mounted in horizontalsequence.

Transmitter Transfer SwitchboardSB-83/SRT

Transmitter transfer switchboard, type SB-83/SRT, (fig. 3-51) has five vertical rows of tenswitches. Radio transmitters are wired tothe five vertical rows; remote stations areconnected to the ten horizontal rows. Switchesare off when the white lines on the knobs arevertical.

Although the switches are of the contin-uously rotatable type, most switchboards areequipped with a spring-loaded, mechanical in-terlock that allows the switches to be closedby turning the knobs in a clockwise direction.

60

MM.

(1)

120.16Figure 3-50.Receiver Transfer

Switchboard SB-973/SRR.

The switches are then opened by turning theknobs counterclockwise. The interlock alsoprevents additional switches in each horizontalrow from being closed when any one of thefive switches in that row is closed already.This arrangement prevents serious damagethat is certain to result from two or moretransmitters feeding a single remote-controlstation at the same time.

By wiring several of these boards together,facilities are available for transferring anytransmitter to any or all remote control stations.Transmitter Transfer SwitchboardSB-863/SRT and SB-988/SRT

The models SB-863/SRT and SB-988/SRTtransmitter transfer switchboards are replacing


36.70Figure 3-51.Transmitter Transfer

Switchboard SB-83/SRT.

the SB-83/SRT in shipboard installations. Ex-cept for their transmitter-handling capacity,these two newer switchboards are identical.The SB-863/SRT (fig. 3-52) handles up to 19transmitters, whereas the SB-988/SRT (notillustrated) handles only 6.

Both of these switchboards have 10 rotaryselector switches in two vertical columns. Eachrotary switch corresponds to a remote-controlstation, and each switch position either corre-sponds to a controlled transmitter or servesto transfer the remote station to an adjacentswitchboard. The remote station assigned eachrotary switch and the transmitter assignedeach switch position are identified on the bake-lite plates attached to the front of each switch-board.

61

REMOTE-CONTROL UNITS

To operate radio transmitters from remotelocations requires the use of remote-controlunits. Most of these units are used as radio-phone units. (RPUs). They provide for en-ergizing and deenergizing transmitters, forconnecting microphones, handsets, chestsets,telegraph keys, and headphones, and for con-trolling the audio output level (volume) ofradio receivers. Some units also enableremote selection of radio channels whenthey are utilized to control multichanneltransmitters and receivers (such as the modelAN/GRC- 27).

PILOTHOUSE

dt6

70.64Figure 3-52.Transmitter Transfer

Switchboard SB-863/SRT.


Radio Set Control C-1138( ) /UR

Radio set control C-1138( )/UR (fig. 3-53)is a remote-control unit designed for installa-tion in protected locations, as :,;1 the CIC orpilothouse. This unit contain- a start-stopswitch for turning a transtr.i.:.:-,! on or off,jacks for connecting a hand.lici. jz chestset,microphone, headphones, or tflegraph key, a. oli!me control for the headp;ione or Loud-sp;;X.7er, and indicator lamps for transmitter-on(p,iwer) and carrier-on indications. Althoughprovisions are ..Roe for CVO' operation, theunit seldom is used for thi' ::urpose. In mostinstances it is utilfzed for ra,r.otelephone com-munications.

'3y means o 7.;.clmitter and r-ceiver trans-fer switchboards, :.s many as fc, r of theca re-mote-control units may ke comecte,# to thesame transmitter or recelver. This a,- .ang?.-ment is utilized when is necessary t'iatradio channel be controlled from more thanone remote location.

The model C-1138( ) /UR is an improvedversi,:el of the older and slightly larger re -

mote- -control unit NT-235VO, still in service.aboard rri3ny ships. TIte two units are siw._ilar in appeannce and function, hence theolder set is ,,t.t desclieti nor illustratedhere.

04)

4

7.403-54.Radio Set Control

C-1207( )/UR.

Radio Set Control C-1207( )/UR

Radio set control C-1207( ) /rTR, (fig. 3-54)is designed for installation in areas that areexposed to the weather. Access to its con-trols is obtained by opening the front cover,which is hinged to the unit. The controls,consisting of a handset, a transtnittar start-stop switch, and a receiver volume control,are mounted on the frot.t panel of the unit.Also mounted on the panel are two indicatorlamps that provide visual in Acation of whetherthe transmitter power and car:nor-on circuitsare energized or deenergizeti, and two tack.,for connecting a chests& aiv!. a se:` of head-phones.

When connected to a standard shipboardtransmitter and receiver, the C-1207( ) /Urpermits remote control of the following func-tions: (1) energizing and deenergizinr, the

7.40.2A transmitter, (2) voiro modulating the trans-Figure 3-53.Radio Set Control mitter input, and (3) controlling the receiver's

C-1138( ) /UR. audio level the earphone(s/. As many as

62

G9 le


four of these units may be connected to thesame transmitter and receiver.

Control Panel Telegraph KeySB-315B/U

Control panel telegraph key SB-315B/U (fig.3-55) contains the components and circuitrynecessary to control the operation of a radiotransmitter from a remote position. Locatedon the plastic control panel are (1) a toggleswitch for turning the transmitter on or off,(2) an indicator light that glows red when thetransmitter is on, (3) a telegraph key thatprovides a means for keying the transmitter,and (4) a key jack that provides for an aux-iliary telegraph key.

This combination control panel and tele-graph key is used in conjunction with a CWor MCW transmitter for the purpose of trans-mitting messages in international Morse code.

Remote-Control/Indic atorUnit NT-23496

Although designed for use with a now ob-solete transmitter-receiver combination, theremote-control/indicator unit NT23496 still isused aboard many ships for controlling multi-channel transmitters and receivers. The unit,illustrated in figure 3-56, is capable of handl-ing a transmitter and two receivers simul-taneously. This arrangement permits guard-ing two radio channels, with the transmitteravailable for use on either channel. By op-erating an equipment selector switch and adial-type channel selector, the operator canselect any of ten preset radio channels on anymultichannel transmitter or receiver controlledby the unit. A set of the usual remote con-trols is provided for each equipment operatedby the remote-control unit.

20.18Figure 3-55.Control Panel Telegraph Key SB-315B/U.

63

(07


Figure 3-56.Remote-Control/Indicator Unit NT-23496.

Frequency Standard AN/URQ-10 andFrequency Distribution AmplifierAM-21 23/U

One of the latest frequency standards isthe AN/URQ-10 (fig. 3-57A). This compacthighly stable frequency standard is designedfor continuous-duty use aboard ships and atshore facilities. It has three fixed outputfrequencies: 5 MHz, 1 MHz, 100 kHz.

Because it is intended as a frequency stand-ard against which other frequency-generatingequipment can be compared, the AN/URQ-10is energized and calibrated at special calibra-tion laboratories. Once it is placed in opera-tion and calibrated properly, the frequencystandard must not be turned off. Any inter-ruption in its operation will cause a changein its output frequencies. Hence, the equipment

64

20.17

is transferred to the using activity while stilloperating.

A battery, which is built into the equip-ment, maintains operation during the time thefrequency standard is in transit. It also sup-plies power to the unit in the event of powerfailure aboard ship. When fully charged, thebattery is capable of operating the equipmentfor approximately 6 hours.

The frequency distribution amplifier AM-21 23/U (fig. 3-57B) is designed to providea means of distributing the precision frequen-cies of a frequency standard to many remotelocations aboard ship.

The three frequency channels from theAN/URQ-10 are accepted by the AM-2123/Uwhich can provide 12 channels of output fre-quencies in any combination of the three inputfrequencies (5 MHz, 1 MHz, 100 kHz).

692


A

Figure 3-57.Frequency Standard equipment.

ADDITIONAL RADIO EQUIPMENT

The radio equipments described in thischapter have been mostly of the general-

65

120.77

purpose communication type. Additionaland more specialized types of radioequipment are discussed in the nextchapter.

69

CHAPTER 4

TELETYPE AND FACSIMILE

The teletypewriter is little more than anelectrically operated typewriter. The prefix"tele" means "at a distance." Coupled with theword "typewriter" it forms a word meaning"typewriting at a distance." By operating akeyboard similar to that of a typewriter, signalsare produced that cause the teletypewriter toprint the selected characters (letters, figures,and symbols). The characters appear at bothsending and receiving teletypewriters, and oneteletypewriter actuates as many machines asmay be connected together.

To see how intelligence is sent by tele-typewriter, let us consider one of the simplerdevices for electrical communication: themanual telegraph circuit. In this series orloop-connected circuit, shown in figure 4-1, wehave a telegraph key, a source of power (calledbattery), a telegraphic sounder, and a movablesounder armature. If the key is closed, currentflows through the circuit and the armature isattracted to the sounder by magnetism. Thisaction causes a clicking sound. When the key isopened, current stops flowing and the armaturereturns to its original position. With these twoelectrical conditions of the circuitclosed andopenit is possible, by means of a code, totransmit intelligence.

The telegraph circuit in figure 4-1 can beconverted to a simple teletypewriter circuit by

STATION A

KEY

HCNIIRSOURCE

.LINE

STATION IS

SPRING

ARMATURE

SOUNDER

1.196Figure 4-1.Manual telegraph circuit.

66

substituting a transmitting teletypewriter forthe key at station A, and a receiving teletype-writer for the sounder at station B. Thisarrangement for a given word-per-minute sys-tem is shown in figure 4-2. In the teletype-writer circuit each current and no current in-terval consumes a set period of time, whereasin the telegraph circuit these time intervalsvary with the code being transmitted by theoperator.

70

TRANSMITTING I RECEIVINGTELETYPEWRITER TELETYPEWRITER

POWERSOURCE

1.200Figure 4-2.Simple teletypewriter circuit.

A teletype signal can be represented asmark and space pulses as shown in figure4-3. Shaded areas show intervals duringwhich the circuit is closed, and the blankareas show the intervals during which the circuitis open. A closed circuit produces a niarkand an open circuit produces a space. Thesignal contains a total of seven units. Fiveof these are numbered, and are called "intel-ligence" units. Various combinations of marksand spaces in the intelligence units representdifferent characters. The first and last units

TIME

START I 2 3 4 5 STOP

1.197Figure 4-3.Mark and space signals in the

teletypewriter characterR.

Chapter 4TELETYPE AND FACSIMILE

of the signal, labeled start and stop, arenamed after their functions: the first startsthe signal and the last stops it. These are apart of every teletype code character, and arethe means by which the teletypewriter machinesand signals are kept in synchronization witheach other.

When the sending and receiving teletype-writers are wire connected, the exchange ofintelligence between them is direct. But whenthe teletypewriters are not joined by wire,operation is more complex. Direct-currentmark and space intervals cannot be sent throughthe air. The gap between the machines mustbe bridged by radio.

RADIOTELETYPE (RATT) SYSTEMS

The Navy uses two basic teletype systemsaboard ship. One is the audio frequency tone-shift radioteletype (AFTSRATT) used for shortrange operation and similar to the familiarAM radio method of broadcasting. The otheris the radiofrequency carrier-shift radioteletype(RFCSRATT) used for long range operationand similar to the familiar FM radio communi-cations.

TONE-SHIFT MODULATION SYSTEM

A teletypewriter, a tone converter, and atransmitter are used to transmit messages bythe tone-shift modulation method. The tele-typewriter sends out a DC signal. The signalis changed to audio tones in the tone-shiftconverter. The transmitter impresses theaudio tones on the carrier and sends out atone-shift modulated carrier wave (fig. 4-4A).

To receive messages with the tone-modulatedsystem, a radio receiver, a tone-shift converter,and a teletypewriter are required. The tone-shift modulated carrier wave enters the re-ceiver, which extracts the signal intelligenceand sends the audio tones to the tone-shiftconverter. The converter changes the audiotones into DC mark and space pulses for theteletypewriter (fig. 4-4B).

In practice, the same tone terminal isused for the receiving and the sending cir-cuits inasmuch as it contains both a transmitkeyer unit and a receiver unit.

57

FREQUENCY CARRIER -SHIFT SYSTEM

At the transmitting end of the long-rangefrequency carrier-shift system (fig. 4-4C) isa teletypewriter, a transmitter, and a frequencyshift keyer unit. The keyer unit is built intothe newer transmitters, but in some older sys-tems it is separate equipment. When the tele-typewriter is operated, the DC mark and spacesignals are changed by the keyer unit intoaudiofrequency carrier-shift output signals.This AFCSRATT is transmitted by conventionalNavy transmitters.

On the receiving side of the long-rangesystem (fig. 4-4D) is a receiver, a frequencycarrier-shift converter, and a teletypewriter.When the frequency carrier-shift signal entersthe receiver, it is detected and changed intocorresponding frequency carrier-shift audiosignals. The audio output of the receiver isfed to the converter, which changes the carrier-shift audio signals into DC mark and spacesignals.

In both the tone-shift system and the carrier-shift system, all teletypewriter signals passthrough the teletypewriter panel that controlsthe looping current in all the circuits. Asillustrated in figure 4-5, the teletypewriter(RATT) panel patches the tone-shift modulatedsystem or the frequency carrier-shift system.It provides every possible RATT interconnectionavailable onboard ship. This operational flexi-bility gives maximum efficiency with the fewestcircuits and the least amount of equipmentin the Navy's compact RATT systems afloat.

TELETYPE EQUIPMENT

Because of the increasing variety of teletypeequipment installed aboard ship, it is impracti-cal to describe every piece of equipment youare likely to encounter. The equipment dis-cussed in the ensuing paragraphs, however, isrepresentative of the types commonly employedin shipboard installations. In some instances,this same equipment may be designated bynomenclature different from that given in thistext. But, in most of these instances, thisvariance in nomenclature merely indicates amodification of the basic equipment describedherein.

7/


FREQUENCY TONESHIFT CONVERTER

MARK a ISPACE

=.

SIGNALS.41

AUDIO ELECTRICALIMPULSES CORRESPOKING TO MARKf.3 SCE SIGNALS

a

TELETYPEWRITER

MODULATEDCARRIERWAVE

0ClgElla

TRANSMITTER

A FREQUENCY TONE-SHIFT

MODULATLU SYSTEM TRANSMIT

4197111\FREQUENCY CARRIER---...SHIFT MODULATED WAVE al

FREQUENCY SHIFT itKEYER 479-

MN .0E4iI -1DIRECT CURRENT

MARK a SPACESIGNALS

0TELETYPEWRITER

rtV.P 3-Eaust

TRANSMITTER

MODULATEDCARRIERWAVE

I i °-° I10' IKOIlpI

RECEIVER

FREQUENCY TONESHIFT CONVERTER

441Il000 41

I DIRECTCURRENTMARKa SPACESIGNALS

RECEIVERAUDIOELECTRICALIMPULSES

TELETYPEWRITER

B FREQUENCY TONE-SHIFTMODULATED SYSTEM RECEIVE

FREQUENCY AUDIOCARRIER ELECTRICAL

SHIFT =_NS IMPULSES

WAVE--

1=11.0 :":0, 0.111

011140

RECEIVER

FREQUENCY CARRIERSHIFT CONVERTER

Li, 0 0. ,,,,, .0_91

CORRESPONDINGDIRECT CURRENT=

MARK a SPACE'.SIGNALS

a

TELETYPEWRITER

C FREQUENCY CARRIER-SHIFT SYSTEM TRANSMIT D FREQUENCY CARRIER-SHIFT SYSTEM RECEIVE

1.228-.231Figure 4-4.Tone and frequency shift modulation.

68

7.2


W V

TONERCVR0 0

CONVERTER

0RCVRSWITCHBOARD

TONETERMINALEQUIPMENT

(i)RATT o 00000PANEL

mmit 1, 1rCARRIER SHIFT

RECEIVER

POWER SUPPLY

TELETYPEWRITER

prEg0 0 0 0 0 00 0 0 0 0 0

SWITCHING°O° CONTROL

XMTRSWITCHBOARD

KEYER

CARRIER SHIFTTRANSMITTER

Figure 4-5.Integrated RATT system.

TELETYPEWRITER SETS

Most of the teletypewriter sets used by theNavy belong to the model 28 family of tele-typewriter equipments. The model 28 equip-ments feature light weight, small size, quietoperation, and high operating speeds. Theypresent relatively few maintenance problems,and are suited particularly for shipboard useunder severe conditions of roll, vibration, andshock.

Mother feature of the model 28 teletype-writers is their ability to operate at speeds of60, 75, or 100 words per minute. Conversionfrom one speed to another is accomplished bychanging the driving gears that are located withinthe equipment. The majority of the Navy'steletypewriters are presently operated at 100words per minute.

Teletypewriters may be send-receive unitsor receive units only. They may be designed

69

1.225

as floor model, table model, rack mounted, orwall mounted sets.

Model 28 Send-ReceiveAnd Receive Sets

These model 28 send-receive teletypewriterpage printers are basically the same. TheTT-48( )/UG is a floor model keyboard-send-ing and page-receiving teletypewriter (fig. 4-6).The TT-48( )/UG provides means for exchangingtypewritten page messages between two or moreships or stations that are similarly equippedand connected by a radio (or wire) circuit.While transmitting from the keyboard, monitorcopy is presented by the typing unit. Hence,messages cannot be transmitted and receivedsimultaneously.

The TT-47( )/UG is an older floor modelstill in use, and differs from the TT-48( )/UGby the type of motor used. The TT-47( )/UG


s4', skA,

1.217Figure 4-6.Model 28 Teletypewriter

TT-48( )UG.

has a 60 hertz synchronous motor, and theTT-48( )/UG uses a series governed motor.

Another example of modification is theTT-69( )/UG, (fig. 4-7). Except for being in-stalled in a cut-down cabinet, the TT-69( )/UGis like the above equipment. It serves thesame purpose, and it functions in the samemanner. Usually, the TT-69( )/UG is installedon small ships where space is of prime con-sideration.

The TT-176A/UG (not illustrated) is like 1. 361the above equipment except that it is a Figure 4-8. Compact Keyboard Send-Receiverack-mounted send-receive teletypewriter. Teletypewriter AN/UGC-20.

1.217(76)Figure 4-7.Teletypewriter TT-69( )UG.

Rack-mounted units such as, teletypewriter,radio, and sonar equipments are designed nar-rower in width. They are mounted aboardships where space is a premium and stand-upoperation is necessary.

The AN/UGC-20 (fig. 4-8) is another send-receive teletypewriter which reduces the trans-mitter keyboard from 32 to 28 typing units.

70


All mechanisms have been mounted to requireminimum space. This compact teletypewriteris designed for use where space is of importance.

The model 28 receive-only sets are similarto the send-receive sets but have no keyboardsending capabilities. The AN/UGC-25 pageprinter (fig. 4-9) is a receive-only, compact,table model set seldom found aboard smallships, but used on large ships, chiefly forcopying messages from the fleet broadcast.

Teletypewriter Perforator - ReperforatorTT-253/UG

An extremely useful teletypewriter equip-ment is the TT-253/UG (fig. 4-10). Its chiefuse is for preparing messages in tape formfor transmission by automatic means. Whenconnected to an external circuit, however,the machine also can be utilized to transmitand receive messages.

When a character is typed on the keyboard,its corresponding teletype code is perforated inthe paper tape. Simultaneous with this action,the character is printed on the tape. In addi-tion, the mark and space combinations for thatcharacter are sent from the keyboard directlyto the external circuit (if connected).

Signals from the external circuit cause themachine to perform as just described. Thus,the TT-253/UG can be employed for communi-cating directly with distant stations or for the

1.362Figure 4-9.Compact receive-only

Teletypewriter AN/UGC-25.

71

eZzz8

50.116Figure 4-10.Send/Receive Typing

Perforator - Reperforator TT-253/UG.

off-circuit preparation of message tapes. Ifboth tape and printed page copy of a messageare desired, the perforator-reperforator isused in conjunction with a page-receiving tele-typewriter.

Teletypewriter Reperforator TT-192( )/UG

The TT-192( )/UG (not illustrated) is basi-cally the same as the TT-253/UG just describedexcept for not having a keyboard.

Normally, the reperforator's wiring is ter-minated in a patch panel (described later inthis chapter) so that it can be patched orconnected into any teletype circuit wired throughthe panel. By patching the reperforator into acircuit, a tape copy of eachmessage is obtained,and messages requiring further processing intape form need not be retyped by the operator.

Teletypewriter Set AN/UGC-6

The AN/UGC-6 teletypewriter (fig. 4-11)is a versatile communication equipment. Itreceives messages from the signal line andprints them on page size copy paper. Inaddition, it can receive messages and recordthem on tape and in printed form. NiN ith page-printed monitoring, the teletypewriter transmits


REPERFORATOR

TRANSMITTERDISTRIBUTOR -4"

PERFORATOR

1

AUTOMATIC TYPER

t.I

SELECTOR SWITCHLINE-TEST SWITCH

Figure 4-11.Teletypewriter AN/UGC-6.

messages that are originated either by perfor-ated tape or by keyboard operation. It mechani-cally prepares perforated and printed tape forseparate transmission with or without simul-taneous transmission and page-printed moni-toring.

The teletypewriter set is composed of thefollowing components: a cabinet, a keyboard, anautomatic typer, a typing perforator, a trans-mitter distributor, a typing reperforator, andpower distribution panels.

In operation, the components are linked byelectrical or mechanical connections to offer awide range of possibilities for sending, re-ceiving, or storing teletypewriter messages.All equipment components are housed in the

72

749

KEYE3CARI)

1.217(31)

cabinet. Transmission signals are initiatedthrough the keyboard or through the transmitterdistributor. Signals are received, and localtransmission can be monitored, on the automatictyper. The typing perforator and typing re-perforator are devices for preparing tapes onwhich locally initiated or incoming teletype-writer messages can be stored for future trans-mission through the transmitter distributor.

The keyboard, typing perforator, automatictyper, and transmitter distributor are operatedby the motor mounted on the keyboard. Selec-tion of these components for either individualor simultaneous operation is by the selectorswitch located at the front of the cabinet, to theleft of the keyboard. All these components are


connected in series in the signal line, but theselector switch has provisions for excludingvarious components from the line. The externalsignal line is connected to the equipment througha line-test switch located below the selectorswitch on the front of the cabinet. Thisarrangement provides a means of disconnectingthe equipment from the line for local testingof the components. The typing reperforatoris operated by a separate motor and powerdistribution system. It also is connected toa separate external signal line.

To become a part of the Naval TacticalData System (NTDS), the AN/UGC-6 is modi-fied to provide input/output communications witha selected data processing computer.

Teletypewriter AN/UGC-13

The Teletypewriter Set AN/UGC-13 whenmodified with Adapter becomes a part of theNaval Tactical Data System (NTDS). Theadapter (contained in the teletypewriter cabinet,fig. 4-12) modifies data to provide compati-bility .be tween a computer and the teletypewriterunit. With the addition of the adapter, notonly can the teletypewriter set communicatewith other stations, but also can exchangeinformation with the digital-data processingcomputer.

The teletypewriter keyboard consists of aset of manually operated keys which generateteletypewriter codes. The printing unit mayaccept teletypewriter codes from the keyboard,transmitter-distributor, or the computer. Thetransmitter-distributor (fig. 4-12) reads per-forated paper tape and converts it into teletype-writer codes which can be transmitted to theprinting unit, the typing reperforator, the auxil-iary typing reperforator, and the computer.The maintenance and control section producesthe control signals and the interrupt codeswhich are sent to the computer indicating thecondition which exists in the adapter. Byuse of the maintenance controls, the teletype-writer set can be disconnected from the com-puter and adapter so teletypewriter operationcan be tested.

An auxiliary line relay circuit (fig. 4-13)permits the adapter to perform multiplex oper-ation with equipment other than this teletype-writer machine. An auxiliary line relay, builtinto the teletypewriter cabinet, is connectedin the teletypewriter adapter loop. This linerelay permits radio link equipment and/or

73

other teletypewriter equipment to be connectedinto the teletypewriter adapter data loop. Com-pared to computer operation, the teletypewriterset is a slow-speed device. This permitsthe computer to perform other functions duringthe time between teletypewriter codes.

Teletypewriter ProjectorUnit AN/UGR-1

Teletypewriter projector unit model AN/UGR-1, (fig. 4-14) enables a teletypewritermessage to be read simultaneously by groupsof persons. It is installed in the pilot ready-rooms in aircraft carriers and in teletypewriterconference rooms ashore.

The bottom of the cabinet houses a page-printing teletypewriter. The message is printedon a roll of transparent cellophane. An opticallens system with a powerful lamp enlarges theimage of the teletypewriter message and pro-jects it onto a tilted mirror at the top rear ofthe cabinet from where it is reflected onto thetranslucent screen. The message is visiblealong the lower edge of the screen as it is beingprinted. With each successive line the messageadvances upward on the screen one line at atime and finally moves out of view at the top.A tape-typing unit provides a permanent type-written record of transmissions in the projectorunit, but at most installations this feature isnot used because a page copy from an additionalteletypewriter patched into the same circuithas been found to provide a more readableand more convenient file copy.

KEYERS AND CONVERTERS

Keyers and converters are an integral partof every radioteletype system. In some instan-ces, the keyer is built into the radio transmitter,but the converter is a separate piece of equip-ment.

Tone-Shift Keyer/ConverterAN/SGC-1( )

Toneshift keyer/converter model AN/SGC-1( ) is used for short-range RATT opera-tion. Normally it is used for communicationon UHF and VHF bands, but it can be used withany transmitter designed for voice modulation.The AN/SGC-1( ) is shown in figure 4-15,with blocks indicating other equipment necessaryfor a complete tone-shift system.

77


REPERFORATORCONTROL PANEL

TRANSMITTERDISTRIBUTOR

ADAPT ERCONTROL

PANEL

MAINTENANCEPANEL

1[4,1'.1,FArets1

.,;?

Q

i:".1

":;4 '

.rte-P-3.14;4*4811

,(k(''

.1 41

';;(4.11:A2

.

7 A-y: .;'%;

/ -

)

*,

FUSES

Figure 4-12.Teletypewriter AN/UGC-13 with adapter.

In tone modulation transmission, the tele-typewriter pulses are converted into corre-sponding audio tones, which amplitude modulatethe carrier frequency of the transmitter. Con-version to the audio tones is accomplishedby an audio oscillator in the tone converter,which operates at 700 hertz when the teletypeloop is in a closed-circuit (mark) conditionand at 500 hertz when the loop is in an open-circuit (space) condition.

74

1. 217

An internal relay in the tone convertercloses a control line to the radio transmitter,which places the transmitter on the air when theoperator begins typing a message. The controlline remains closed until after the message istransmitted.

When receiving messages, the t,tie con-verter accepts the mark and space tones comingin from an associated radio receiver and con-verts the intelligence of the tones into signals


r'COMPUTER - - -L -

COMPUTER

-t---INTER -

CONNEC -T IONPANEL

I COMPUTER V

L - -_J

AOAPTER

_41

TELETYPE-WRITER

AN /UGC -13

AUXILIARYLINE

RELAY

AUXILIARY I ANTENNAI TELETYPE-II WRITERIS/It_

PATCHPANEL

Figure 4-13.Teletypewriter system for NTDS.

+hat close and open the contacts of a relayconnected in the local teletypewriter DC loopcircuit. This action causes the local teletype-writer to print in unison with the mark andspace signals from the distant teletypewriter.

Converter - Comparator GroupsAN/URA-8( ) and AN/URA-17( )

The AN/URA-8( ) frequency carrier-shiftconverter-comparator group (fig. 4-16) is usedfor diversity reception of RATT and FAXsignals. The equipment consists of two frequencyshift converters (top and bottom units) and acomparator (middle unit).

For either space diversity or frequencydiversity reception, two standard Navy receiversare employed in conjunction with the converter-comparator group. In space diversity operation,the two receivers are tuned to the same carrierfrequency, but their receiving antennas arespaced some distance apart. Because of therequired spacing between antennas, space diver-sity usually is limited to shore station use. Infrequency diversity operation, the two receiversare tuned to different carrier frequencies thatare carrying identical intelligence. Frequencydiversity reception commonly is used aboardship for copying fleet broadcasts, which arekeyed simultaneously on several frequencies.

In diversity reception, the audio output ofeach receiver is connected to its associatedfrequency shift converter, which converts thefrequency shift characters into DC pulses.

75

RADIOCOMMUN-ICATION

EOUIPMENT

31.29(124)

The DC (or mark-space) pulses from eachconverter are fed to the comparator. In thecomparator, an automatic circuit comparesthe pulses and selects the better mark and thebetter space pulse for each character. Theoutput of the comparator is patched to theteletypewriter. The converter units also canbe used individually with separate teletype-writers to copy two different FSK signals.

The newest converter-comparator group,the AN/URA-17( ) (fig. 4-17 is a completelytransistorized equipment designed to perform thesame functions as the AN/URA-8( ). Althoughpresent procurement of frequency shift con-verters is confined to the AN/URA-17( ), thereare relatively few installations compared withthe larger number of AN/URA-8( ) converters.

The AN/URA-17( ) consists of two identicalconverter units. Each converter has its owncomparator circuitry. Hence, a separate com-parator unit is not required. The physical sizeof the AN/URA-17( ) is further reduced byusing transistors and printed circuit boards.The complete equipment is less than half thesize of the older AN/URA-8( ).

TELETYPE PATCH PANELS

To provide flexibility in teletype systems,the wiring of all teletypewriter and associatedequipments is terminated on jacks in teletypepatch panels. The equipment then is connectedelectrically in any desired combination bymeans of patching cords (lengths of wire with


r

31.34Figure 4-I4.Teletypewriter Projector Unit

AN/UGR-1.

plugs on each end). The plugs on the cords areinserted into the jacks at the front of the panel.In some instances, commonly used combinationsof equipment are permanently wired togetherwithin the panel (called "normal-through").They are wired in such a manner, however,that the individual pieces of equipment can be"lifted" from the combination, and then usedalone or in other combinations.

In addition to providing flexibility, teletypepanels also furnish a central point for connectingthe DC voltage supply into the teletypewriter

76

ro

RADIORECEIVER

RCVRTRANSFER

PANEL

IRADIO

1 R ANSMITT F.R

XMTRTRANSFER

PANEL

Art 0 OW* [If410

e),

TELETYPEPANEL

TELE TYPEWRITER

1.240Figure 4-15.Tone Shift Keyer/Converter

AN/SGC-1( ).

circuits. Thus, one source of supply can beused for all circuits passing through a partic-ular panel.

Teletype Panels SB-1203/UG andSB-1210/UGQ

Teletype panels SB-1203/UG and SB-1210/UGQ (fig. 4-18) are used for interconnectionand transfer of teletypewriter equipment aboardship with various radio adapters, such as fre-quency shift keyers and converters. The SB-1203/UG is a general-purpose panel, whereas


FREQUENCYSHIFT

CONVERTER

COMPARATOR

FREQUENCYSHIFT

CONVERTER

Figure 4-16.Converter-Comparator Group AN/URA-8( ).

FREQUENCY SHIFT CONVERTERSCV-483/URA-17

50.76Figure 4-17.Converter-Comparator Group

AN/URA-Vi( ).

77

1.235

the SB-1210/UGQ is intended for use withcryptographic devices. The colors RED andBLACK are used to identify crytographic equip-ments. A patch panel used cryptographicallyis commonly painted red and has red bandsinstalled or painted on its cables. Black isused to identify a nonsecurity patch panel.

Each of the panels contains six channels,with each channel comprising a looping seriescircuit of looping jacks, set jacks, and a rheostatfor adjusting line current. The number oflooping and set jacks in each channel variesaccording to the panel model. Each panelincludes a meter and rotary selector switchfor measuring the line current in any channel.There are six miscellaneous jacks to whichmay be connected any teletypewriter equipmentnot regularly assigned to a channel.

If the desired teletype equipment is wiredin the same looping channel as the radioadapter (keyer or converter) to be used (normalthrough connection), no patch cords are required.But, if the desired teletypewriter (for example,

Fr


SWITCH

LOOPING JACKS

SET

MISCELLANEOUS

Figure 4-18.Teletype Patch Panels SB-1203/UG and SB-1210/UGQ.

in channel 1) is not wired in the same loopingchannel as the keyer or converter to be used(for example, channel 3), one end of the patchcord must be inserted in the set jack in channel1, and the other end in either one of the twolooping jacks in channel 3.

In any switching operation between the vari-ous plugs and jacks of a teletype panel, thecord plug must be pulled from the looping jackbefore removing the other plug from the set(machine) jack. Pulling the plug from the setjack first open-circuits the channel, causing allteletype messages in the channel to be inter-rupted. It may also produce a dangerousDC voltage on the exposed plug.

REMOTE TRANSMITTER CONTROL UNITC-1004( )/SG

Another piece of equipment used with tele-typewriter installations aboard ship is theC-1004( )/SG control unit shown in figure 4-19.This unit is mounted close to the teletypewriterkeyboard and permits remote control of theradio transmitter. It has a transmitter poweron-off switch, a power-on indicator lamp, acarrier-on indicator lamp, and a three-positionrotary selector switch.

78

70.79

The TONE S/R switch position is used forboth sending and receiving when using a toneshift keyer converter. When using frequencycarrier-shift mode of operation, the operatormust switch to SEND position for transmittingand to REC position for receiving.

1.244.1Figure 4-19.Remote Control Unit

C-1004( )S/G.


MULTIPLEXING

The number of communication networks inoperation per unit of time throughout any givenarea is increasing constantly. In the not-too-distant past, each network was required tooperate on a different frequency. As a result,all areas of the radio-frequency spectrum hadbecome highly congested.

The maximum permissible number of intel-ligible transmissions taking place in the radiospectrum per unit of time can be increasedthrough the use of multiplexing. The mainpurpose of a multiplex system is to increase themessage-handling capacity of radio communi-cation, or teletypewriter channels and the trans-mitters and receivers associated with them.This increase in capacity is accomplished bythe simultaneous transmission of several mes-sages over a common channel. The frequencydivision multiplexing telegraph terminal em-ploys a number of tone channels slightly dis-placed in frequency. Each tone channel carriesthe signals from a separate teletypewritercircuit and modulates a common carrier fre-quency. Receiving equipment at a distant stationaccepts the multiplex signals, converts themto mark-space signals, and distributes themin the proper order to a corresponding numberof circuits.

Most of the active fleet is equipped withmultiplex equipment.

TELEGRAPH TERMINAL SETAN/UCC -1 (V)

Tha AN/UCC-1(V) (fig. 4-20) consists offrequency division multiplex terminal equipmentfor use with radio (or wire) circuits. Theequipment is completely transistorized.

Each of the two electrical cabinets (fig.4-20) houses one control-attenuator (right-side) for switch control. The module willalso have either 8 keyers for transmission,or 8 frequency-shift converters for receiving,or any combination of both.

Each channel has its own keyer and willhave one or more converters that will accepta keying speed of 100 WPM. When keyed byteletypewriter signals, the keyers generateone frequency representing a mark and anotherrep resenting a space (2 modes for each channel).The converters receive the signals and reversethe process performed by the keyers. Theyaccept a particular frequency-shift signal and

79

P5

z

120.26(120C)Figure 4-20.Telegraph Multiplex Terminal

AN/UCC-1(V).

convert it to the DC marks and spaces foroperation of the teletypewriters.

Because of its light weight, small size,and high message-handling capacity, the AN/UCC-1(V) is suitable for installation on mosttypes of ships.

A schematic representation of a 4-channelmultiplex installation is shown in figure 4-21.The frequency shift transmitter, the keyer, theradio receiver, the converter, the patch panels,and the teletypewriter equipment are included toshow the complete send-receive system.

Teletypewriter signals are fed to the terminalequipment's transmitting group from two, three,or four separate circuits. The signaling speedcan be 60, 75, or 100 wpm, but the speed mustbe the same for each circuit. In the trans-mitting group, the teletypewriter signals areconverted to multiplexed signals that are ar-ranged in sequential order f or transmission overa single radio circuit. The multiplexed outputof the transmitting group is fed through thepatch panel and frequency shift keyer to theradio transmitter, where the frequency-shiftedmultiplex signal is placed on the air.

At the receiving station, the multiplex signalsfrom the radio receiver are processed throughthe frequency shift converter. Then, they arepatched to the receiving group. The receiving


RADIORECEIVER

FREQUENCY SHIFTCONVERTER

RECEIVINGPRINTER

(CHANNEL D) rFREQUENCY SHIFT

TRANSMITTER

PATCH PAN E17..."'

1

()EYE R

/ I / PATCH PANEL.01(

.1.1111 IMO law

RECEIVINGPRINTER

(CHANNEL C)TRANSMITTERDISTRIBUTOR(CHANNEL D)

RECEIVINGPRINTER

(CHANNEL B)


(CHANNEL C)


(CHANNEL B)RECEIVINGPRINTER

(CHANNEL A)


(CHANNEL A)

KEYBOARDTRANSMITTER

50.83(120C)Figure 4-21.Multiplex installation employing 4-channel terminal equipment.

80


group converts the multiplexed signals backinto standard teletypewriter signals and dis-tributes the DC marks and spaces to the properteleltypewriters.

FACSIMILE

Facsimile (FAX) is a method for trans-mitting still images over an electrical com-munication system. The images, called picturesor copy in facsimile terminology, may beweather maps, photographs, sketches, typewrit-ten or printed text, or handwriting. The stillimage serving as the facsimile copy or picturecannot be transmitted instantly in its entirety.Three distinct operations are performed. Theseare (1) scanning, (2) transmitting, and (3) re-cording or receiving.

The scanning operation consists of sub-dividing the picture in an orderly manner into alarge number of elemental segments. Thisprocess is accomplished in the facsimile trans-mitter by a scanning drum and phototube ar-rangement.

The picture to be transmitted is mounted ona cylindrical scanning drum, which rotates at aconstant speed and at the same time moveslongitudinally along a shaft. Light from an ex-citer lamp illuminates a small segment of themoving picture and is reflected by the picturethrough an aperture to a phototube. During thetransmission of a complete picture, the lighttraverses every segment of the picture as thedrum slowly spirals past the fixed lighted area.

At any instant, the amount of light reflectedback to the phototube is a measure of the light-ness or darkness of the tiny segment of the pic-ture that is being scanned. The phototubetransforms the varying amounts of light intovarying electrical signals, which, in turn, areused to amplitude modulate the constant fre-quency output of a local oscillator. Then, themodulated signal is amplified and sent to theradio circuits.

Electrical signals received by the facsimilereceiver are amplified and serve to actuate arecording mechanism that makes a permanentrecording (segment by segment) on recordingpaper. The paper is attached to a receiverdrum similar to the one in the facsimile trans-mitter. The receiver drum rotates synchron-ously with the transmitter drum. This actioncontinues until the original picture is repro-duced in its entirety. The recording mechanism

81

may reproduce photographically with a modu-lated light source shining on photographic paperor film, or it may reproduce directly by burninga white protective coating from specially pre-pared black recording paper.

Synchronization is obtained by driving bothreceiving and transmitting drums with syn-chronous motors operating at exactly the samespeed.

Framing (orienting) the receiver drum withrespect to the transmitter drum is accom-plished by transmitting a series of phasingpulses just before a picture transmission is tobegin. The pulses operate a clutch mechanismthat starts the scanning drum in the receiver sothat it is phased properly with respect to thestarting position of the scanning drum in thetransmitter.

The equipment necessary for radio facsimileoperation and its relationship to other units inthe various receiving and transmitting systemsare illustrated by block diagram in figure 4-22.As shown in part A of the figure, the receivingsystem consists of a standard radio receiver,a frequency shift converter, and a facsimilerecorder. Part B shows two systems fortransmitting facsimile signals. One, the upperrow of blocks, is for long-range, carrierfrequency shift transmission and consists of afacsimile transceiver, a keyer adapter, a fre-quency shfit keyer, and a CW transmitter.The other, the lower row of blocks, is forshort-range, audiofrequency shift transmissionand employs a facsimile transceiver, a radiomodulator, and a voice transmitter.

The equipment discussed in the remainingportion of this chapter is representative of thatused in shipboard facsimile installations.

FACSIMILE TRANSCEIVERSTT-41( )/TXC-1B AND TT-321A/UX

Facsimile transceiver TT-41( )/TXC-1B(fig. 4-23), is an electromechanical-optical fac-simile set of the revolving-drum type for bothtransmission and reception of page copy. Col-ored copy may be transmitted, but all repro-duction is in black, white, and intermediateshades of gray. Received copy is recordedeither directly on chemically treated paper, orphotographically in either negative or positiveform. The equipment transmits or receives apage of copy 12 by 18 inches in 20 minutes at


I

IRECEIVER 0,

I

_ A _ _ _ _I

I

I TRANSMITTERCW

I

4

FREQUENCY

SHIFTCONVERTER

TRANSMITTERVOICE

IP

FREQUENCYSHIFTKEY ER

FACSIMILERECORDER

ORTRANSCEIVER

4 KEYERADAPTER

FACSIMILETRANSCEIVER

RADIOMODULATOR

Figure 4-22.Radio facsimile systems.

I

70.14

regular speed (60 RPM=LPM), or in 40 minutes The TT-321A/UX facsimile transceiver, al-with half-speed (30 lines per minute, LPM) so shown in figure 4-24 is the same transceiveroperation, as above but has an increase in motor speed.

13.70Figdre 4-23.Facsimile Transceiver TT-41( )/TXC-1B and TT-321A/UX.

82

F4


Figure 4-24.Facsimile Recorder RD-92( )/UX.

The TT-321A/UX transmits or receives a pageof copy 12 by 18 inches in 10 minutes at regularspeed (120 LPM), or in 20 minutes with half-speed (60 LPM) operation.

A facsimile transceiver (or transmitter)generates an amplitude-modulated signal, andthe recorder is designed to operate on thistype of signal. The signal generated by thetransmitter is unsuitable, however, for trans-mission by means of radio. For this reason, itis necessary to use signal conversion equip-ment between the facsimile transmitter andthe radio transmitter, and between the radioreceiver and the facsimile recorder.

FACSIMILE RECORDER RD -92( )/UX

Facsimile recorder RD-92( )/UX, shown infigure 4-24, is used for direct stylus recordingonly. Unlike the transceivers described earlier,it cannot be used for transmitting facsimile,nor can it be used to receive on photographicfilm.

83

13.71

When receiving copy, the recorder drumrotates at a speed of 60 rpm. (No provision ismade for multispeed operation.) As the drumrotates, a mechanical mechanism holding astylus needle is moved across the drum to theright. The stylus needle records on paperfastened on the drum at the rate of one scanningline for each revolution of the drum. When thepaper is covered completely, from left to right,the stylus is returned automatically to the leftside of the drum so that it will be ready torecord the next transmitted copy.

This basic RD-92( )/UX facsimile recorderwas updated to meet NATO requirements of60 -90 -120 LPM by modifying the recorder andusing a combined pair of equipments to getdesired results. The modifiedmodel RD-171( )/UX operates from 60-90 LPM: the RO-160( )/UX operates from 60-120 LPM: and theRD-1'72( )/UX operates from 90 -120 LPM. Anytwo combinations met requirements of 60 -90-120 LPM.

P7


FACSIMILE RECORDER AN/UXH-2B

A more modern facsimile recorder than theone just described is the model AN/UXH-2Bshown in figure 4-25. Instead of recording onpaper that is attached to a revolving drum,the AN/UXH-2B makes direct recordings acrossa continuous page of paper. Paper is suppliedfrom a roll within the machine.

Recording is accomplished by using threerecording heads that are carried across thepage on a rubber belt. The heads are spaced onthe belt so that only one head is touching thepaper at any given time, and the speed at whichthis head moves across the paper is the sameas the scanning speed at the transmitter.Recording speeds can be 60, 90, or 120 scansper minute, making this recorder compatiblefor operation with most Navy facsimile trans-mitters.

When receiving signals from a transmittercapable of sending the necessary control signals,the AN/UXH-2B can be left unattended. Upon

receipt of the proper signals, it automaticallyphases, starts recording at the beginning of atransmission, stops when the transmission iscomplete, and compensates for changes insignal level during the recording.

KEYER ADAPTER KY-44( )/FX

For frequency carrier-shift transmission,the amplitude-modulated audio signal from thefacsimile transmitter must be converted to DCkeying voltages before being applied to thefrequency shift keyer. This is the function ofkeyer adapter KY-44( )/FX shown in figure4-26.

The output of the adapter is a DC signalthat varies in amplitude from 0 to 20 volts,depending on the frequency of the audio inputsignal. When the DC signal is used to keya frequency shift keyer, and when the frequencyshift keyer, in turn, is controlling a radiotransmitter, the end result is transmitted fre-quency carrier -shift signal similar to a

70.88Figure 4-25.Facsimile Recorder AN/UXH-2.

84


Figure 4-26.Keyer Adapter KY-44( )/FX.

radioteletype signal. As stated previously, thismethod of transmitting facsimile signals is usedfor long-range transmissions.

MODULATOR MD-168( )/UX

For transmission of facsimile signals bythe audiofrequency shift method, a radiomodulator, such as the MD-168( )/UX (fig.4-27), is required between the facsimile trans-mitter and the radio transmitter. The modu-lator converts the amplitude-modulated signalfrom the facsimile transmitter to constantamplitude frequency modulation, which variesat frequencies between 1500 and 2300 Hz.This frequency variation is used to modulatethe radiotelephone transmitter. Modulator

1-

70.81

MD-168( )/UX can be employed with any trans-mitter capable of being voice modulated. Ingeneral, the audio-frequency shift method isused for short-range transmissions.

FREQUENCY SHIFT CONVERTERCV-172( )/U

With either the frequency carrier shift orthe audiofrequency shift methods of transmittingfacsimile signals, the output of the radio re-ceiver at the receiving station is an audio-frequency shift signal of constant amplitude.The function of frequency shift converter CV-172( )/U (fig. 4-28) is to convert the receiver'soutput to an amplitude-modulated signal thatvaries between 1200 and 2300 Hz. which is

Figure 4-27.Modulator MD-168( )/UX.

85

Al X

70.82


--1-42103::-0

Figure 4-28.Frequency Shift Converter CV-172( )/U.

the signal required for proper operation ofthe facsimile recorder.

The CV-172( )/U is not the only frequencyshift converter used by the Navy in facsimile

86

70.85

installations, but it is the one most commonlyfound aboard ship. Others you may encounterare models CV-97/UX and the CV-1066/UX.They all perform the same function.

90

CHAPTER 5

RADAR

Radar (from the words radio detection andranging) is one of the greatest scientific devel-opments that emerged from World War II. Itmakes possible the detection and range deter-mination of such objects as ships and air-planes over long distances: The range of radaris unaffected by darkness, but it often isaffected by various weather conditions; forexample, heavy fog or violent storms.

THEORY OF OPERATION

The basic principles of radar are similar tothose of sound echoes or wave reflections. If aperson shouts in the direction of a cliff or someother sound-reflecting surface, he hears hisshout return from the direction of the cliff.Sound waves, generated by the shout, travelthrough the air until they strike the cliff. Therethey are reflected or bounced off, and some arereturned to the originating spot. These reflectedwaves are the echo that the person hears.

Time elapses between the instant the soundoriginates and the time the echo is heard.Because sound waves travel through air at ap-proximately 1100 feet per second, the distance ofthe reflecting surface from the shouter can becomputed as (1100)t/2, where t/2 is one-half theelapsed time, corresponding to one-half theround trip distance out and back.

Most radar systems operate on a principlevery much like that just described. The majordifference is that radar utilizes radiofrequencyelectromagnetic waves, instead of sound waves,to detect the presence of reflecting surfaces.

At least three methods of radar detectionare in use today. These are (1) the continuous-wave method, (2) the frequency-modulationmethod, and (3) the pulse-modulation method.This last method is the most common.

In the pulse-modulated method (fig. 5-1),the transmitter sends out short pulses of RF

87

energy at regular intervals. Depending on theparticular radar, the duration of the transmitterpulse ranges between 0.1 and 5.0 microseconds.Each transmitting period is followed by a re-ceiving period of relatively much longer dura-tion than the transmitting period. The transmit-receive cycle is repeated many times persecond. This repetition rate depends on thedesign of the set.

RANGE DETERMINATION

The employment of radar to determine therange (distance) to a target is made possibleby (1) our knowledge of the velocity of thetransmitted radiofrequency energy in space,and (2) the measurement of the time requiredfor the energy to reach a target and return.

Once radiated into space, radiofrequencyenergy travels at the speed of light. In termsof distance traveled per unit of time, it travelsapproximately 186,000 land miles per second,or 164,000 nautical miles per second. To makepractical use of this velocity-distance relation-ship, it is necessary to consider distance interms of yards, and time in terms of micro-seconds (ps). Computing mathematically, wefind that RF energy travels 328 nautical yardsin 1 microsecond. This means that approximat-ely 6.18 microseconds are required for theenergy to travel 1 nautical mile, or 2027 yards(6080 feet). For convenience, however, allNavy radar ranging (including equipment cali-bration) is based on a flat figure of 2000yards (6000 feet) per nautical mile; and the6.18 microseconds is rounded of to 6.1.

The action of range determination is ex-plained with the aid of figure 5-2 and a targetat a 20-mile range. Information obtainedduring the radar operation is presented visuallyon the face of a cathode-ray tube (scope).(See discussion of A-scope later in this chapter.)The tube face (screen) for certain types of

9/


// / // / /

ANTENNA/

/ / // /RADIATING ,' / / //ELEMENT / ,/ /

, / /I / /' /

I , / r /1

/ / // r /

TRANSMITTED/ / , RF WAVEFRONT/ ' / /

ANTENNAREFLECTOR

DUPLE xER

RADAR

/ )/)TRANSMITTER 1

// I,I / ii I/

I I i II IiI I / I

I I I ' I / iI i I

I 1 I I iI I I

II I 1

I / I II

REFLECTED RF I I I II

I IWAVEFRONT I I 1 1 I I I I 1

RADARRECEIVER

Figure 5-1. Pulse-modulated method.

indicators usually is covered with a translucentscale graduated from 0 to the maximum range(in yards or miles). In this instance the maxi-mum range is 20 miles. A horizontal sweepvoltage causes the cathode ray beam to traceacross the screen beneath the scale. Scalereadings indicate the actual target range.

We discuss the A-scope only because it isan easy method of explaining how distance isdetermined by radar. The A-scope has beenreplaced by the. PPI (planned position indicator)in general-purpose radar sets. See discussionof PPI-scope later in this chapter.

In figure 5-2A, a radiofrequency pulse istransmitted and is just leaving the antenna.A small "pip" is produced at the zero-milemark on the scope at the instant the radarenergy is transmitted. The leading edge ofthis pulse serves as the reference from whichtarget distance is measured.

In part B, 61 p s later, the transmittedpulse has traveled 10 miles toward the target.The sweep trace, which is timed to show truerange by indicating one-half the distance theRF pulse has traveled, is now at the 5-milemark.

In view C of figure 5-2, 122 Ns after thetransmission interval, the RF energy hasreached the target, 20 miles away; a relatively

88

9c

120. 78

small RF reflection, or echo, has started back.The scope trace is now at the 10-mile mark.

In part D, 183 p s after transrrl'Lsion, theecho has returned half the distance from thetarget, and the scope is now at the 15-milemark.

Finally, at part E of the illustration, 244 p safter transmission of the initial pulse, the echohas returned to the radar receiving antenna. Thisrelatively small amount of RF energy is ampli-fied and applied to the vertical deflection sys-tem of the scope, and an echo pip of smalleramplitude than the initial pip is displayed atthe 20-mile mark.

If two or more targets are in the pathof the transmitted pulse, each returns a portionof the transmitted energy in the form of echoes.The target at the greatest distance away (as-suming all targets are similar in size andtype of material) will return the weakest echo.

BEARING DETERMINATION

Bearing (also called azimuth) is the direc-tion of an object from the observer, expressedin degrees clockwise through 360° around thehorizon. True bearing is measured from truenorth; relative bearing is measured from theheading of the ship. In radar applications,

Chapter 5RADAR

TRANSMITTED PULSE

IN

0

FLIS 20

MILES

TEDPULSE

SCOPE

IS 20

ECHO

',

TRANSMITTEDPULSE

0

HO- TI ECHOI I

MILES

IS 20

20.282Figure 5-2. Radar range determination.

bearing (true or relative) of the target maybe determined by concentrating the radiatedenergy in a narrow beam, and by knowingthe beam direction when a target pip is pickedup.

89

9,5

Radar antennas are designed to producea single narrow beam of energy in one direction(fig. 5-3). The receiving pattern is the sameas the transmitting pattern. The antennaand associated lobe of RF energy are eitherrotated in the horizontal plane through 360°or "rocked" back and forth so that they sweepover a given area. When a target is encountered(fig. 5-3A), a return signal is received. Theantenna may then be positioned so that the re-ceived echo signal is maximum (fig. 5-3B).The maximum signal strength indicates that theaxis of the lobe passes through the target.The radar set is equipped with bearing indicatorsso that target bearing can be measured eitherfrom true north or with respect to the headingof a ship (or aircraft) containing the radar set.

The bearing of a target can be determinedin several ways. When the single-lobe methodis used, the sensitivity of the system dependson the angular width of the lobe pattern. Ifthe signal strength changes appreciably whenthe antenna is rotated through a small angle,the accuracy with which the on-target positioncan be selected is great.

When the antenna lobe is rotated from posi-tion A to position B (fig. 5-3), the increasein the signal strength received is small. Thus,the bearing of the target cannot be determinedaccurately. When a radar has a narrow lobeof concentrated energy (fig. 5-3C), the changein signal strength is greater as the antennais rotated to the target and a more accuratedetermination of bearing is possible.

ALTITUDE DETERMINATION

The remaining dimension necessary to locatecompletely an object in space can be expressedeither an angle of elevation or as an alti-tude. If one is known, the other can be calcu-lated from one of the basic trigonometricratios. A method of determining the angleof elevation and the altitude is shown in figure5-4. Slant range (fig. 5-4A) is obtained fromthe radarscope indication as the range tothe target. The angle of elevation is thesame as that of the radar antenna (fig. 5-4B).Altitude is equal to the slant range multipliedby the sine of the angle of elevation.

In radar equipment with antennas that canbe elevated, altitude determination by slantrange is computed automatically be electronicmeans.


ANTENNAREFL ECTOR

GET

144C1-AR

A

1 /,/

-.-.........---- _ `,..

-..` ------- \ - - -- ....1- ,....,

..-- - \ -- -- - -- -- --- T

- -_\ -- -_-_- / //...- .... _.

..... ,..--1:,--- ' .---...

B

C

Figure 5-3. Radar determination of azimuth or bearing.

BASIC PULSED RADAR SYSTEM

A block diagram of the basic units of apulse-modulated radar system is shown infigure 5-5. The modulator produces the timingpulses that trigger the transmitter and in-dicator. These timing pulses are convertedby the transmitter into high-power pulses ofRF energy at the assigned frequency. Theuse of one antenna for both transmitting andreceiving is made possible by the duplexer.

90

LOBEAXIS

20.284(120C)

It directs the transmitter outgoing pulses tothe antenna (away from the receiver) and theincoming echo pulses to the receiver (awayfrom the transmitter). The antenna systemradiates the RF energy as a directional beam,and receives the echo pulses only from thedirection in which the antenna reflector ispointing. The receiver amplifies the receivedecho pulses reflected from the target, andapplies them to the indicator. There they aredisplayed on a cathode-ray tube. Necessary

Chapte- 5RADAR

RADARANTENNA

PN

TARGET

ALTITUDE

ANGLE OF ELEVATION

RADARANTENNA

ASLANT RANGE

ANGLE OF ELEVATION

DIRECT RAYONLY

EARTHS SUP ,'ACE

ANGLE OF ELEVATION

20.285 (120C)Figure 5-4.Radar determination of altitude.

power for the various radar functions is sup-plied by the power supply. A more detaileddescription of some of the individual blocksfollows.

MODULATOR

The transmit-receive periods in a pulsedradar system are controlled by synchronizingsignals generated in the modulator or syn-chronizer. Usually, the basic control devicewithin the modulator is a very stable oscil-lator. The oscillator output is amplified,shaped as required, and fed as synchronizingpulses to the transmitting, receiving, and in-dicating sections.

The transmit period in a radar system ismuch shorter in duration than the receive period.Sufficient time must be allowed during thereceive period (between transmissions) to en-sure the return of echoes from the maximumdesirable range of the system. Thus, themaximum range from which echoes can be

91

95

MODULATOR TEN

ANIENNA.,

POWER

SUPPLY OUPL LH

ACTORREF!

INDICATOR RECEIVER

72.59Figure 5-5.Block diagram of apulse-modulated radar system.

received for a target of given size dependson the relationship of the time between trans-mission bursts (pulse repetition) and the RFpower generated.

The relationship between pulse repetitionrate (PRR) and maximum range is explainedwith the aid of the following example. Assumethat sufficient power is transmitted to pro-duce useful echoes from a target of appreciablesize. The pulse repetition period is the re-ciprocal of the pulse repetition rate. Thus,PRP =1 /PRR. If the PRR is 250 pulses persecond (PPS), the period is 1/250=.004 secor 4000 p s. Assuming further that the trans-mission period contained in this time periodis of negligible duration, and by knowing thateach mile traversed by the RF energy requiresapproximately 6.1 p s to travel in each direc-tion (or 12.2 p s per mile), it is seen that themaximum range is 4000 p s/12.2 p s = 328miles.

Although maximum range increases witha decrease in pulse repetition rate, it shouldbe noted that the antenna system is rotatedat a relatively rapid rate, and the beam ofenergy strikes a target for a relatively shorttime. During this time, a sufficient numberof pulses must be transmitted and their echoesreceived to produce a visual indication oftarget presence. The most desirable pulserepetition rate, then, is a compromise be-tween maximum range and indicator require-ments.

The minimum range at which a targetcan be detected is governed largely by thewidth (duration) of the transmitted pulse. Ifa target is so close to the transmitter thatthe echo is returned before the transmitteris turned off, reception of the echo is masked


by the transmitted pulse. Hence, for shortranges, the transmitted pulse lust be of shortduration to permit the detection of close-intargets.

The choice of pulse repetition rate, pulsewidth, frequency, and transmitter power outputis decided by these five conditons: (1) thetactical use of the system, (2) accuracy re-quired, (3) range to be covered, (4) overallphysical size, and (5) the most practical methodof generating and receiving the signal.

TRANSMIT TER

An outgoing radiofrequency pulse of ex-tremely short duration is generated by thetransmitter each time a keying pulse is re-ceived from the modulator. The frequencyof the RF pulse is high. The directivity ofthe radiated beam is greater at highfrequencies.Moreover, the higher the frequency, the shorterthe wavelength; hence, the smaller and lighterwill be the antenna system components.

A special microwave oscillator tube, calleda magnetron (fig. 5-6), frequently is used asthe transmitting tube in radar systems. A pulsefrom the modulator, shaped and amplified toform a strong negative pulse, is applied tothe magnetron cathode. The presence of thispulse causes the tube to oscillate for the dura-tion of the pulse. The frequency of the mag-netron oscillations may approximate several

MAGNETRON FREQUENCYADJUSTMENT

AM.MAGNETRON

TODUPLEXER

-17

CATHODE TERMINAL

32.180Figure 5-6.Magnetron.

92

?4,

thousand megahertz. Usually the peak poweroutput ranges between 100 and 1000 KW but,because the short duration of the pulse resultsin a much lower average power, the com-ponents are relatively small.

In a radar system using a magnetron (fig.5-7), the magnetron output is fed to the radarantenna through a duplexer and a waveguide.The duplexer consists of antitransmit-receive(ATR) and transmit-receive (TR) switches thatprevent the high-powered RF output of thetransmitter from entering the receiver, but per-mit the returning signal to enter the receiverunimpeded. The duplexer and the waveguidephysically connect the transmitter to the antenna.

Some radar transmitters are similar toradio (communication) transmitters. Figure 5-8is a block diagram of a radar transmitter.Instead of the single magnetron, the radartransmitter consists of an electron tube oscil-lator, amplifiers, frequency multipliers,drivers, and power amplifiers. Although thestages and their purposes are the same asthose in a communication transmitter, thepeak power requirements are much higherin a radar transmitter, and it is necessaryto use special power amplifier tubes. Klystronsand traveling wave tubes are examples of thesetubes, but, because of their complexity, theyare not treated in this text.

In the electron tube type of radar transmitter,frequency stability is ensured by using only themost stable type of oscillator-buffer arrange-ment, and by operating the oscillator at asubmultiple of the transmitter output frequency.Frequency multipliers then are used to pro-duce the desired output frequency. The driverstages increase the RF power. The modulatorsupplies keying pulses to the final power am-plifier stages, thereby controlling the durationand repetition rate of the transmitted pulses.Finally, as in the magnetron type of transmitter,the duplexer and the waveguide provide thephysical connection between the transmitter andthe antenna. Monitoring circuits along the wave -guide produce information necessary for tuningthe transmitter and receiver, as well as forvarious tests.

RECEIVER

The receiver used in a particular radarsystem depends on the design of the transmitter.In the system with the magnetron, the re-ceiver (fig. 5-9) does not have RF amplifiers

Chapter 5RADAR

FROMANTENNA

(TRANSMITTER)MAGNETRON

ATR(SWITCH)

DUPLEX ER B WAVEGUIDE

e.ATR

(SWITCH)

ATR JUNCTION

I rRECEIVER I

TR JUNCTION

-.

TR(SWITCH)

ANTENNAREFLECTOR

ANTENNA

Figure 5-7. Transmitting section of pulsed radar system using a magnetron.

OSCILLATORAND

BUFFER

FREQUENCYMULTIPLIERS

ANDAMPLIFIERS

MODULATOR

.10.DRIVERS

AND

POWERAMPLIFIERS

1 DUPLE XERWAVEGUIDE,

ANDRF MONITORING

CIRCUITS

1

KEYING PULSEINPUT PATHS

RECEIVER I

ANTENNAREFLECTOR

ANTENNA

Figure 5-8. Transmitting section of pulsed radar system usingoscillator, multipliers, and amplifiers.

OUPLEXER

FROMTRANSMITTER(MAGNETRON)

CRYSTAL(DIODE)MIXEP

1

LOCALOSCILLATOR(KLYSTRON)

wrA

32.183

72. 60

/TOIF SECOND VIOE0 INDICATOR

AMPLIFIERS OETECTOR AMPLIFIERS

AUTOMATICFREQUENCY

CONTROL(AFC)

Figure 5-9. Radar receiver used in conjunction with a magnetron transmitter.

93

97

20. 293


preceding the mixer stage. The incoming signal(echo) is fed, via the duplexer, directly fromthe antenna to the mixer. In the mixer, the in-coming signal is mixed (heterodyned) with anunmodulated RF signal generated by the localoscillator. Heterodyning in the mixer pro-duces the intermediate frequency, which, inturn, is fed through several IF stages beforeit is detected. The detector output (called"video") is amplified in several stages beforebeing fed to the indicator where a visual in-dication of the received echo is proci,tced.

Another output from the mixer goes to theautomatic frequency control (AFC) circuit. Thiscircuit produces a DC voltage proportional to theamount of error (if any) in the frequency of theIF signal. The error voltage is applied to thelocal oscillator in such a manner that it changesthe oscillator frequency until the mixer outputIF is on frequEncy. This action ensures aconstant intermediate frequency, regardless ofchanges in the magnetron frequency or ten-dencies of the local oscillator to drift.

Some radar receivers (not illustrated) differfrom the type just described in thatthey requirethe use of RF amplifiers ahead of the mixerstage. Essentially, these receivers are of theconventional superheterodyne type.

INDICATOR (REPEATER)

The purpose of the indicator is to presentvisually the information gathered by the radarset. In the early days of radar, the indicatorwas a part of the main radar console. With theincrease in numbers and purposes of radarsets aboard ship, however, remote indicators(radar repeaters) became necessary.

A representative radar repeater is shownby block diagram in figure 5-10. The repeaterconsists of a scope (cathode-ray tube), a powersupply, video amplifiers, a sweep generatingsection, a sweep positioning system, impedancematching circuits, and a range marker circuit.

When the modulator sends a keying pulseto the transmitter, it also sends a triggeringpulse to the indicator. This trigger pulse,processed through the sweep generating sec-tion of the indicator, appears on the face ofthe scope coincidently with the transmissionof the RF pulse from the antenna. In otherwords, the trigger pulse initiates the traceor sweep across the face of the scope, and thebeginning of the trace indicates the time theradar signal is transmitted.

94

The target echo pulse (video) from the re-ceiver is increased in amplitude by videoamplifiers. It then is applied to the scopevia impedance matching circuits. Dependingon the type of presentation employed, theecho appears on the trace (or sweep) as apip or a bright spot. As stated earlier, thetime of appearance of the echo pulse is in-dicative of the target range.

Information from the ship' s gyrocompass andthe radar antenna assembly is applied to the in-dicator through a sweep positioning system.This system positions the sweep to a truebearing. At the same time the sweep positioningsystem synchronizes the rotation of the sweepwith the rotation of the antenna. Vv ithout truebearing data from the gyro, the position ofthe sweep indicates a relative bearing.

Range markers can be displayed on thescreen to aid the operatir in estimating therange of a target. In aL:ition, most radarrepeaters are equipped with a mechanical orelectronic cursor that facilitates the accuratereading of bearing. Some radar repeaters alsoare equipped with a range strobe or bug thatpermits accurate measurement of range.

Types of Presentations

While the radar beam is systematicallyscanning the surrounding area, the results ofeach scan are presented un various scopes.Several types of scope presentations (or scans)are used to display the target information. Onlythe basic types are discussed here, however.In each type, the screen of the cathode raytube is illuminated by an electron beam (spot),which moves swiftly across the screen, leavinga line of light (called the sweep or trace)in its wake. The manner in which the sweepappears on the screen depends on the typeof presentation.

A-SCOPE.Earlier types of scope presen-tations were identified by a single letter ofthe alphabet, such as the A-scope shown infigure 5-11. The A-scope is used to determinerange only. Its screen has a short persistence;that is, it glows for only a short time afterthe illuminating spot is removed. The echois presented on the screen as a vertical dis-placement of the horizontal trace, and thepoint at which the displacement occurs in-dicates the range to the target.

At one time, the A-scope presentation wasthe major type of display. For accurate

93"

Chapter 5RADAR

FROMRECEIVER

VIDEOAMPLIFIERS

RANGEMARKERCIRCUIT

FROMMODULATOR

IL

DELAYLINE

1111.IMPEDANCEMATCHINGCIRCUITS

FROM FROMANTENNA SHIP'S I

ASSEMBLY GYRO

POWERSUPPLY PROVIDES AC

AND DC POWERFOR ALL UNITS

PULSE

GENERATOR

IMPEDANCEMATCHINGCIRCUITS

SWEEP

POSITIONINGSYSTEM

PPI SCOPE

SWEEP GENERATING SECTION _J

Figure 5-10.Radar indicator.

LAI

59.4Figure 5-11.A-scope presentation.

measurements, however, the antenna had to bestopped and pointed directly at the target. Thisdisadvantage was overcome by the developmentof the planned position indicator (PPI) type ofdisplay.

PPI SCOPE.The PPI scope (fig. 5-12)presents both range and bearing information.Usually this scope is employed in a radarsystem whose antenna is uniformly rotatedaround the vertical axis. The trace on the Large numbers of pulses are transmittedscope rotates in synchronization with the for each rotation of the antenna. As eachantenna. pulse is transmitted, the scan spot starts at

72.61

NI ____L____ I

ISLAND

4t Amok4E%

Ot

TRANSMITTERNur

SHIP

53.109Figure 5-12.PPI presentation.

E

95

99


the center of the screen and moves towardthe edge of the screen along a radial line.Upon reaching the edge, the spot quickly re-turns to the center and begins another tracewith the next transmitted pulse. The returntrace of the spot is eliminated from the screenby a process called blanking.

When an echo is received, the intensity ofthe scanning spot increases considerably, anda bright spot remains at that point on thescreen. The position of the radial line on whichthe echo appears indicates the target bearing.The distance of the target pip from the originof the radial line indicates the target range.

Unlike the A-scope, the PPI scope haslong persistence. Because of this characteristic,it is possible to produce a map of the sur-rounding territory on the scope face, makingthe PPI presentation useful as an aid to navi-gation. The PPI scope presentations also pro-vide the observer with instantaneous changesof target positions in all directions.

RHI SCOPE.Some radars are equipped withspecial antennas that enable altitude informationto be obtained. The range height indicator(RHI) scope is used to display altitude data.(See fig. 5-13.)

59.11Figure 5-13.RHI presentation.

Except for the type of information dis-played, the RHI is similar to the PPI. Onboth scopes, the sweep pivots from one point,and target echoes are shown in bright relief

96

against the background. The sweep on the RHIscreen, however, does not go through 360°.Instead, the sweep is synchronized with anantenna that scans vertically through a fewdegrees and returns to a preset elevation.

An altitude cursor appears across the faceof the Rill scope. The cursor, curved to conformto the earth's surface, can be moved up ordown. The vertical movement of the cursoris recorded by an associated set of counters.With the cursor aligned so that it bisectsthe target, altitude is read on these counters.The slant range to the target is indicated alongthe baseline of the sweep.

Because bearings cannot be read from anRHI scope, the RHI operator usually worksin conjunction with the PPI operator who coacheshim onto the target on which altitude informa-tion is desired.

ANTENNAS

Instead of emitting radio waves in all direc-tions, the radar antenna must send them outin a concentrated beam. One method of ob-taining this directional effect is to arrangetwo or more dipoles so that radiation fromthe dipoles adds in some directions and can-cels in other directions. (Dipoles are con-ductors that are one-half wavelength long atthe carrier frequency of the radar.) Whena reflector (either metal or another set ofdipoles) is placed behind the dipoles, radiationoccurs in one direction, and the resulting lobesof transmitted energy are similar to thoseshown in figure 5-14.

/OD

DIPOLES

I ..e.MINOR LOBE

ANTENNA

REFLECTOR

33.108Figure 5-14.Directivity of radar beams.

Chapter 5RADAR

Another method of obtaining directivity inthe emitted radar beam is to situate the open,flanged end (feed horn) of the waveguide sothat the RF energy is sprayed against thereflector. Then, the reflector is shaped so thatthe beam is concentrated as desired.

Many types of antennas are used with militaryradar systems, and they vary in appearanceconsiderable. Although the radiating elementactually is the antenna, the entire antennaarray is implied when the term "antenna" isused in this text.

BEDSPRING ARRAY

The bedspring array (fig. 5-15), so calledbecause of its resemblance to a bedspring,is used with air-search radars. It consistsof a stacked dipole array with an untunedreflector. The more dipoles that are usedor stacked in one dimension (horizontal, forexample), the more narrow the beam of radiatedenergy becomes in that same plane. Con-sequently, the size of the antenna is not thesame for all installations.

PARABOLOIDAL ANTENNA

The paraboloidal (or parabolic) antenna,(fig. 5-16), consists of a dipole or feed hornradiator and a parabolic or dish type reflector.This type of antenna produces a narrow beam,the degree of whose concentration iS determinedby the size and shape of the reflector.

Because the lobe produced by the parabolicantenna is narrow and sharp, its chief functionis with fire control and special-purpose radars.It is not used with most shipboard air-search orsurface-search radars, because the roll of theship could cause the very narrow verticalbeam to miss a target. It is currently beingused, however, with height-finding radars whichdo have the pitch and roll stabilization systems.

BARREL STAVE ANTENNA

With a simple modification to the reflector,the parabolic antenna becomes the barrel staveantenna. (See fig. 5-17.) Essentially, the barrelstave reflector is a parabolic reflector withthe top and bottom cut away, leaving onlythe center part of the reflecting surface.

The lobe produced by the barrel stavereflector still is narrow horizontally. But,because there is no surface to restrict its

97

/Q/

vertical height, the lobe becomes a high verti-cal beam suitable for surface-search. The heightof the lobe is great enough to prevent theroll of the ship from causing a target to goundetected.

BILLBOARD ARRAY

A billboard or fixed array is one in whichan antenna or antenna system is placed infront of a large plane-reflecting surface. Suchan antenna is shown in figure 5-18. The re-flecting surface may consist of rods (joined atthe end), mesh, or a solid sheet of conductingmaterial.

Because of their large size and weight,fixed array installations presently are limitedto larger ships. The installation consists offour billboard antennas built into the super-structure so that each antenn2 covers a 90°sector around the ship. This type of installa-tion ordinarily is used with air-search radars.

RADAR FUNCTIONS ANDCHARACTERISTICS

No single radar set has yet been developedto perform all the combined functions of air-search, surface-search, altitude-determination,and fire control because of size, weight, powerrequirements, frequency band limitations, andso on. As a result, individual sets have beendeveloped to perform each function separately.

Most of the radar sets that are designedfor a specific purpose, such as surface-search,have certain system constants or general char-acteristics in common. The remainder of thischapter is devoted to a brief discussion of thefunctions and characteristics of various radarand radar ancillary systems.

SURFACE-SEARCH RADARS

The principal function of surface-searchradars is the detection and determination ofaccurate range and bearing of surface targetsand low-flying aircraft while maintaining 360°search for all surface targets withinline of sight distance of the radar antenna.The system constants of this radar vary fromthose of the air-search radar. Because themaximum range requirement of a surface-search radar is limited mainly by the radarhorizon, very high frequencies are used to


I

"Itwear.

le

:=.4.. igtao-yrY..

kt -

Figure 5-15.Bedspring array.

give maximum reflection from such smalltarget-reflecting areas as ship mastheadstructures and submarine periscopes. Narrowpulse widths permit short minimum ranges, ahigh degree of range resolution, and greaterrange accuracy. High pulse repetition ratesare used for best illumination of targets.Medium peak powers can be used to detectsmall targets at line of sight distances. Widevertical am widths are used to compensatefor pitc and roll of own ship and to detectlow-flying aircraft. Narrow horizontal beamwidths permit accurate bearing determinationand good bearing resolution.

98

AIR-SEARCH RADARS

32111ral..7"..

hadalooll.I.L.......a

IMM

33.109

The chief function of an air-search radaris the detection and determination of rangesand bearings of aircraft targets at long ranges(greater than 50 miles), maintaining complete360° search from the surface to high altitude.System constants must be selected with thisfunction in mind. Low frequencies are chosen(P- or L-band) to permit long-range trans-missions with minimum loss of signal. Widepulse widths (2 to 4 microseconds) increasethe transmitting power and are used to aidin detecting small targets at greater distances.

/OA

Chapter 5RADAR

Figure 5-16.Parabolic antenna.

A_

REFLECTOR

\--FEEDRORN

120.28

ANTENNA PEDESTAL

32.186Figure 5-17.Barrel stave antenna.

Low pulse repetition rates are selected forgreater maximum measurable range. Highpeakpower permits detection of small targets atlong ranges. Wide vertical beam width is usedto ensure detection of targets from the surfaceto relatively high altitude and to compensatefor the pitch and roll of the ship. Mediumhorizontal beam width gives fairly accuratebearing determination and bearing resolutionwhile maintaining 360° search coverage.

99

TRANSMITTINGANTENNA

WIRE MESHREFLECTINGSCREEN

RECEIVINGANTENNA

120.29(120C)Figure 5-18.Billboard array.

ALTITUDE-DETERMINING RADARS

The function of the altitude-determiningradar is to find the accurate range, bearing,and altitude of aircraft targets detected byair-search radar. Its antenna must be tilt-stabilized to provide a stable reference foraltitude determination. High frequencies (S-band) are chosen as a compromise between thelong-range capabilities of lower frequenciesand the narrow beam-forming characteristicsof higher frequencies. Narrow pulse widths (1microsecond) are chosen to permit good rangeresolution. High pulse repetition rates (600 to1000 PPS) permit detection of small aircrafttargets at medium ranges (30 to 50 miles). Highpeak power permits the detection of small air-craft targets at medium ranges while using nar-row pulse width. Narrow vertical and horizontalbeam widths (1° to 3°) are selected to permit ac-curate bearing and position angle determinationand good bearing and elevation resolution.

FIRE CONTROL RADARS

The principal function of fire control radarsis the acquisition of targets originally detectedand designated from search radars, and thedetermination of extremely accurate ranges,bearings, and position angles of targets. An-tennas must be tilt - stabilized to compensatefor pitch and roll of own ship. Very highfrequencies are chosen (X-band and K-band)to permit the formation of narrow beam widthswith comparatively small antenna arrays, detec-tion of targets with small reflecting areas,and good definition of all targets. Pulse widths(0.1 to 3 microseconds) provide a highdegree of

1o3


range accuracy, short minimum range, andexcellent range resolution. Repetition rates(1500 to 2000) afford maximum target detectionwhile using narrow pulse widths. Because verylong ranges are not required, low peak powerpermits the use of smaller components bykeeping the average power low. Narrow verticaland horizontal beam widths (0.9° to 3°) provideaccurate bearing and position angles and a highdegree of bearing and elevation resolution.

MISSILE GUIDANCE RADARS

In general, missile guidance radars operateon the same principles as the air-search,altitude-determining, and fire control radarsjust described. The guidance systems for themissiles we are concerned with can be dividedinto four groups: (1) self-contained, (2)command, (3) beam-rider, and (4) homing.

In a self-contained (inertial) guidance systemall the guidance and control equipment is insidethe missile. The guidance system neithertransmits nor receives signals during themissile's flight. This is a major advantage,since only limited countermeasures can beused against it. This means that the trajectorythat the missile must follow to hit the targetmust be calculated and fed into the missilebefore it is launched. The heart of the inertialguidance system is an arrangement of accelero-meters that detect motions along their sensitiveaxes. The inertial guidance system is used forlong range surface-to-surface missiles, suchas the Polaris.

A command guidance system is one inwhich directional commands are sent to themissile from some outside source. One radaraboard ship tracks the target, another radartracks the missile, and a computer takes thetwo sets of tracking data and issues radarsignals which guide the missile to the target.The equipment in the missile consists of areceiver and a control system. The shipboardequipment consists of two radars and a computer.

The beam-rider guidance method is verysimilar to the radar command guidance method.The principle difference is that the commandsystem gives specific signals to "turn right,or turn left, etc.," while in the beam-ridersystem the shipboard control equipmenttransmits information only, not commands.The missile guidance equipment must interpretthis information contained in the received radarbeam and formulite its own correction signals.

100

Therefore, we say the missile rides the beamto the target. The beam-rider system is highlyeffective for use with short-range and medium-range surface-to-air and air-to-air missiles.

Two types of beam-rider systems arepossible. In the simplest type, a single radardirector is used for both target tracking andmissile guidance. In the other, one radardirector is used for tracking, while anotherprovides the very narrow guidance beam. Thesingle-radar system has the advantage ofsimplicity, but it is not nearly as effectiveas the two-radar system.

In the two-radar system, a computer isused between the radars, and the missileguidance radar is controlled by the computer.The computer takes target informationspeed,range, and coursefrom the tracking radar,and computes the course that must be followedby the missile. The output of the computercontrols the direction of the guidance radarantenna, and points the guidance beam towardthe point of target interception. Becausethe computer receives information constantly,it is able to alter the missile course asnecessary to offset evasive action or changesin course by the target.

The homing guidance system controls thecourse of the missile by a device in themissile that reacts to radiation given off bythe target, such as heat, light, radio, or radarradiation. The radiation may be generatedby the thrget or reflected from the target whengenerated by some outside source. This systemis commonly used.

AEW RADARS

Airborne early warning (AEW) systems areused extensively in the Navy. These systemsare special shipboard and aircraft radar equip-ment that work together as a single unit.

The purpose of the AEW system is toextend the normal radar horizon by placingthe radar set in an airplane, and relayingthe radar information to the AEW ship forpresentation on the ship's indicator. Thus,targets can be seen at considerable greaterdistances than is possible with standard ship-board radar sets. For example, a plane ata 1000-foot altitude will have a minimumradar detection range of 55 miles on a target50 feet high. If the plane is relaying radarinformation to a mother ship 50 miles away,then the ship has an effective search range of 105

Chapter 5RADAR

miles in the plane's direction. If a relayis directly over a mother ship at 5000 feet,the ship has an effective 360° search rangeof 100 miles.

DOPPLER EFFECT

The doppler effect is the change in thefrequency resulting from motion between asource and a receiver. To illustrate thisconcept, consider two persons, source (S) andreceiver (R) (fig. 5-19A), standing along aswift-flowing stream some distance apart.Source (S) is tossing fishing bobs into thewater at a steady rate, say 10 BPM (bobsper minute). Receiver (R) has a .., )pwatch,and as the bobs begin to pass he takes acount for one minute, counting 10 bobs. Inthis illustration the time was one minute,distance remained constant between S and Rand rate of frequency of the bobs was thesame at S and at R. This would be known aszero-doppler.

Source (S) begins moving steadily away,tossing bobs into the stream at the samerate 10 BPM, figure 5-1913. Again receiver(R) counted bobs for one minute as they passed(say that he counted only 8 BPM). R observedthat the bobs were spaced farther apart,therefore the frequency at R is less (lower).The time interval has stayed the same, butdistance between bobs has increased; the rateof frequency has decreased, although the sourcefrequency has remained constant. This wouldbe known as down or low doppler.

Likewise, if S moves toward R tossingbobs at the same rate (fig. 5-19C), the bobswill be closer together and observer (receiver)R would see a higher frequency (say 12 BPM).Again the time interval is the same. Distancebetween bobs has decreased and frequencyincreased. This would be up or high doppler.

High doppler is explained again in figure5-19D. If the receiver runs toward the source,who is stationary, he views the bobs morefrequently and the effect is the same as infigure 5-19C.

Doppler effect may be observed in soundwaves when listening to a phonograph turntable,if the turntable's speed is varied. At a higherRPM, this voice is at a higher pitch, andat a lower RPM the voice is at a lower pitch.Another common example of the doppler effectby sound waves is at a train crossing (fig. 5-20).You listen to the high-pitch whistling sound

101

as the train approaches, and the low-pitchsound as the trsi.a passes and goes away.As the train approaches you, the relativemotion will cause your ear to receive morecycles per second than when there is norelative motion, and as the train moves awayyour ear encounters fewer cycles per second.This is the doppler effect and is due to frequencychange of the sound signal in relation to theobserver.

The doppler effect is also noted in electro-magnetic frequency waves, and extensive useis made of this phenomena in electronics.

/06

CONTINUOUS WAVE RADAR

Continuous-wave radar is used as a speedmeasuring device. CW radar cannot measuredista .ce because the wave is continuous andhas no time reference as compared to pulseradar. CW radar (fig. 5-21) uses two separateantennas since the transmitter and receiveroperate simultaneously.

The transmitter (fig. 5-21) has a modulatorto shape the high power input of the RF oscillator.The RF oscillator sends two signals. One isa weak signal sent directly to the receivermixer which can be compared to figure 5-19Ahaving no-doppler and the other is a verystrong signal radiated at the transmitter antennawhich has a high-doppler as compared withfigure 5-19D. The aircraft in this radar beamis shown reflecting some of the RF energyto the receiver antenna. The aircraft, in effect,becomes a second emitter of waves which givesthe high-doppler effect as shown in figure 5-19C.

The heterodyne receiver compares theinternally received frequency, which has no-doppler, with the transmitted frequency whichhas high-doppler, the difference being thefrequency shift. The radar can only indicatethe aircraft's presence and its relative speed.To determine direction of the aircraft, high-or low-doppler must be determined by theaddition of a local oscillator.

The doppler frequency shift is then amplified,detected, and sent to the indicator system forinterpretation. If the doppler frequency isin the audio range, a head set can be usedto indicate the presence of a target.

Continuous wave radar and pulse radarsystems can be combined to measure a target'svelocity toward or away from you and alsomeasure the distance and transit time. Thisis known as pulse-doppler radar.


rZ))Cr.,

Tq4

)

B

o0

o

STOP WATCHti'

0)).,

FLOW Op

C449

STOP WATCH

O

0

"-t

STOP WATCH

Op

N4-4,

RSTOP WATCH...di

0

0

Figure 5-19.Doppler principle.

Legit look at a pulse radar in its simplestform. The transmitter generates a very shortpulse of high energy radiofrequency. As thetransmitter pulse leaves the antenna, the radar' sreceiver becomes operative, allowing it to

102

120.79

receive and amplify any RF energy reflected bya target. The time between the transmission ofthe RF energy and the echo return is measuredelectronically and displayed graphically by aCRT (cathode-ray tube).

/06

Chapter ,7:RADAR

APPROACHING 0-

Figure 5-20.Principle of doppler sound waves.

TRANSMITTER TRANSMITTERANTENNA

RECEDING

71.37(120C)

RECEIVER

DISCRIMINATOR AMPLIFIER MIXER

ILOCAL OSCILLATOR

I INDICATOR

RECEIVERANTENNA

Figu-e 5-21.Principle of continuous wave doppler radar.

Thus the pulse radar can measure rangeaccurately, and does not depend on target'smovement for detection. Therefore it candetect both stationary and moving targets.

The CW echo is changed in frequency by amoving target. This change, as you remember,is called Doppler shift. The Doppler frequencyis used for target detection, and to indicatethe target's range rate. It is possible, by useof filter circuits, to reject all targets exceptthose traveling at or near a selected velocity.Normally a CW radzr will not detect stationarytargets. If the C' radar radiates energy

103

55.58(120C)

continuously, at a constant frequency, there isno reference by which we can measure rangedirectly. Even with a form of carrier modulationits ranging is crude.

On the other hand, pulsed radar radiatesenergy at a selected time interval. Thisinterval determines the usable range of theradar. Pulse radar, with its precise meas-urement of transit time, has a very accuraterange measurement capability.

The pulse-Doppler radar combines the bestfeatures of CW and pulse radar. The pulse-Doppler method uses high frequency CW, in

/a7


the form of short bursts, or pulses. Thepulse ,-3petition rate (PRR) is much higherthan that of a conventional pulse radar, andthe pulse length is longer.

A measure of the target's velocity towardor away from the radar can be obtained bymeans of the Doppler shift. This can beaccomplished in the same manner as in CWradar.

IFF SYSTEMS

Although technically not a radar equipment,an electronic system that is employed withradar permits a friendly craft to identifyitself automatically before approaching nearenough to threaten the security of other navalunits. This system is called identification,friend or foe (IFF) (fig. 5-22). It consistsof a pair of special transmitter-receiver units.One set is aboard the friendly ship; the other

REPLYCHALLENGE

A.SHIP'S CHALLENGE, AIRCRAFT'S REPLY

REPLY-1

\CHALLENGE

SMdakliL_\\\\B. AIRCRAFT.; CHALLENGE, SHIP'S REPLY

Figure 5-22.IFF systems.120.80

104

is aboard the friendly unit (ship or aircraft).Because space and weight aboard aircraft arelimited, the airborne system is smaller, lighter,and requires less power than the shipboardtransmitter-receiver. The airborne equipmentsare automatic, and operate only when triggeredby a signal from a shipboard unit.

The IFF systems are designated by MARKnumbers. In order to avoid confusion betweenIFF systems and fire control systems, the IFFmark number is a Roman numeral (Mk III),whereas the fire control number is an Arabicnumeral (Mk 29).

The IFF system operates as follows: An air-search radar operator sees an unidentified targeton his radarscope. He turns on the IFF transmit-ter-receiver, which transmits an interrogatingor "asking" signal to the airborne transmitter-receiver. The interrogating signal is receivedby the airborne unit, which automatically trans-mits a characteristic signal calledan identifica-tion signal. The shipboard system receives thesignal, amplifies it, decodes it, and displays iton the radarscope or on a separate indicatorscope. When the radar operator sees theidentifying signal and identifies it as the properone, he knows that the aircraft is friendly.

If the aircraft does not reply when inter-rogated, however, or if it sends the wrongidentifying signal, then the ship must assumethat the target is an enemy, and defensiveaction must be taken. The IFF equipmentscomprise the interrogator-responder and theidentification set (transponder).

The interrogator-responder performs twofunctions. It transmits an interrogating signal,and it receives the reply. The transponder alsoperforms two functions. Not only does it receivethe interrogating signal, but it replies auto-matically to the interrogating signal by trans-mitting an identifying signal. The two types ofinterrogation are direct and indirect. Interroga-tion is direct when the interrogating signal thattriggers the transponder is a pulse from theradar equipment. Interrogation is indirectwhen the interrogating signal is a pulse froma separate recognition set operating at a dif-ferent frequency from that of the master radar.

Early IFF systems used direct interrogation.Direct interrogation proved unsatisfactory, how-ever, because the transponder was required torespond to radars that differed widely in fre-quency. Later IFF systems, consequently, makeuse of indirect interrogation within a specialfrequency band reserved for IFF operation.

laY

CHAPTER 6

RADAR EQUIPMENT

The modern warship has several radars.Each radar is designed to fulfill a particularneed, but it also may be capable of performingother functions. For example, most height-finding radars can be utilized as secondary air-search radars; in emergencies, fire controlradars have served as surface-search radars.To familiarize you with some of the capabilitiesand limitations of radars and radar accessories,this chapter is devoted to describing the charac-teristics and uses of various shipboard radarequipment.

Because there are so many different modelsof radar equipment, the radars and accessoriesdescribed herein are limited to those commonto a large number of ships in the active fleet,and to those that are replacing older equipmentcurrently installed in the fleet.

SURFACE-SEARCH RADARS

As you learned in the preceding chapter,the principal function of surface-search radarsis the detection of surface targets and low-flying aircraft and the determination of theirrange and bearing. A common surface-searchradar in use today is the AN/SPS-10( ).

RADAR SET AN/SPS-10( )

Designed for installation aboard destroyersand larger ships, the AN/SPS-10( ) is a me-dium-range, two-coordinate (bearing and range)surface-search and limited air-search radar(fig. 6-:). Its maximum range when detectingsurface targets is greater, normally, thanthe optical horizon as viewed from the antennareflector. Actual detection range depends ona number of conditions, including antennaheight, target size and composition, weatherconditions, and the density of the atmosphere.You can normally expect to detect targets

105

1 1/4 times the optical horizon, due to therefraction of RF energy near the earth' s surface.In some instances, targets have been detectedat distances exceeding 100 miles.

The AN/SPS-10( ) operates in the frequencyrange 5450 to 5825 MHz, with a peak power out-put of 285 KW. Its magnetron is tunable overthe entire frequency range. This feature isdesirable so that its operating frequency canbe changed to minimize interference from otherradar sets operating at the same frequency.

Two pulse widths are available. The longpulse (1.3msec) provides a longer detectionrange than the short pulse (0.25msec). Inaddition, the pulse repetition rate (PRR) canbe varied between 625 and 650 pulses per second(PPS), which will enable the operator to checkfor "second time around echos".

The antenna used with the AN/SPS-10( )is a horn-fed, truncated parabolic reflector,which rotates in a clockwise direction at anaverage speed of 16 RPM. Radiated signalshave a beam width of 1.5° in the horizontalplane and between 12° and 16° in the verticalplane.

The major units of the AN/SPS-10( ) areshown in figure 6-1. These units are typical ofthose employed in most surface-search radarsystems.


The AN/SPS-5( ) radar set is used onships of escort size and smaller. Classedas a medium-range surface-search radar, theAN/SPS-5( ) has a tunable magnetron thatpermits selection of any operating frequencybetween 6275 and 6575 MHz. (Later modelsof the AN/SPS-5 have a frequency range of5450 to 5825 MHz.) Power outputvariesbetween170 and 285 KW, depending mostly on theoperating frequency selected. A pulse length of0.37m sec is used as a compromise between long

/09


INTERCONNECTING BOX

ANTENNA ASSEMBLYFt LTER,BAND SUPPRESSION

tI FF FILTER)

TO IFF EQUIPMENT

RECEIVER-TRANSMITTER, RADAR

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INDICATORS MODULATOR, RADAR

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CONTROL,RADAR SET

TOBULKHEAD MAINPOWER SWITCH

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ADAPTER, INDICATOR

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RADAR REPEATER EQUIPMENT

DRRANGE AZIMUTH INDICATOR

Figure 6 -1, Surface - search Radar Set AN/SPS-10( ) system.

106

/10

32.172

Chapter 6RADAR EQUIPMENT

and short ranges. The antenna is similar tothat of the AN/SPS-10( ).


The AN/SPS-21( ) is a short-range, compactsurface-search radar designed principally forinstallation aboard small ships. It also isinstalled on some of the larger auxiliary shipsfor use as a close-range navigational radar.Being a short-range equipment (75 yards to16 miles), the set has a narrow pulse widthof 0.2m sec and a low power output of 10 KW.Its operating frequency is selectable within thefrequency range 5500 to 5600 MHz, and itemploys a parabolic antenna that radiates abeam 2° wide in the horizontal plane and 15°high in the vertical plane.

RADAR SET AN/SPS-53 A

Radar Set AN/SPS-53 A (fig. 6-2) is a surface-search radar operating in the 9345 to 9405MHz band and is capable of detecting surfacetargets up to maximum range of 32 miles.The set operates from a 115-volt, 60 hertzpower source.

The antenna rotates at 15 RPM to providesearch facilities for both surface and low-flying targets. The feed assembly, containingthe slotted-array radiating element, producesa vertical beam width of 20 degrees and ahorizontal beam width of 1.f degrees. Thevertical plane beamwidth allows enough latitudeto keep the target in the beam pattern duringship's pitch and roll.

AIR-SEARCH 2-COORDINATE RADARS

The primary function of air-search radarsis the long-range (greater than 50 miles)detection of aircraft targets and the determi-nation of their ranges and bearings. Theseradars search 360° in azimuth from surfaceto high elevation angles.

Some of the most widely used 2-coordinateair-search radars in the fleet are: AN/SPS-6C;AN/SPS-29( ); AN/SPS-40; -40A; AN/SPS-37,-37A; and AN/SPS-43, -43A. These radar setsuse the PPI, display indicators for determiningrange and azimuth.

The main design features of the 2-coordinateair-search radars are basically the same. Theymay, however, vary in frequency, range, type

107

of antenna, and in design techniques. All ofthese radar sets, except the AN/SPS-6C usea Moving Target Indicator (MTI) to discri-minate against clutter of stationary objectsand to emphasize only moving targets.

All of the above 2-coordinate radars, exceptthe AN/SPS-6C and -29, transmit long pulsesfrom a generated narrow pulse and then receiveand compress the long pulse back into a narrowpulse. This minimizes the peak power re-quirements of the radar set without impairingthe range resolution. These modified shapedpulses also reduce interference with othershipboard electronic equipments.

RADAR SET A.N/SPS-6C

The AN/SPS-6C is a ship-borne, air-search,2-coordinate radar for target bearing andranging. This high-power (500 KW) long-rangeset is used in the fleet for detecting, ranging,and tracking both conventional and jet aircraft.

A description of the AN/SPS-6C radar setfollows. The power transformer (fig. 6-3)steps down the ship' s voltage to the 115 voltsrequired for operation of the radar set. Theline disconnect switch is bulkhead mounted.The electrical filter assembly prevents any RFpickup of the main power circuits from enteringthe radar transmitter-receiver.

The radar transmitter-receiver console (fig.6-3) has the operating controls in the topcompartment. The echo box is used to measurefrequency. The transmitter-receiver is tunableto any operating frequency within the rangeof 1250 to 1350 MHz, and provides a choice ofpulse lengths (1 or 4 m sec). The transmitterRF signal is transmitted through the rectangularwaveguide to the antenna. The directionalcoupler permits a sample of transmitted RFenergy to be coupled to the echo box.

The antenna is a unidirectional transmittingand receiving type with a 30° vertical beamwidth and a 3 1/2° horizontal beam width.The reflecting surface is a section of a pa-rabola. The feed horn is a dual frequencyradiator for radiating RF energy for bothradar and IFF recognition sets. The antennacontrol unit supplies DC power to rotate theantenna pedestal.

The radar set control contains the remotecontrols used for operation. Antijammingcontrols are also located here in recess behinda small door.


ANTENNA AND PEDESTAL

ANTENNASAFETY SWITCH

sir

RECEIVER TRANSMITTER

VIEWINGHOOD

SIGNAL DATACONVERTER

TRIGGERPULSEVIDEO

AMPLIFIER

CONTROL INDICATOR

120.81Figure 6-2.Surface-search Radar Set AN/SPS-53A units.

The video amplifier amplifies signals from The range indicator is used to indicatethe radar receiver and supplies video out- target range information. The 5-inchputs to the PPI indicator. This cabinet is screen is accompanied with a viewingdesigned for bulkhead mounting. hood.

108

-.........Mr


TO MASTER PPI

TO PPI REPEATER

ANTENNAPEDESTAL

RADARRECEIVER WAVEGUIDE

ANTENNA CONTROL

ELECTRICALFILTER

ASSEMBLY

LINEDISCONNECT

SWITCH

RANGE INDICATORHOOD

Figure 6-3.Air-search Radar Set AN/SPS-6C system.

109

I I 3

RAnAR SETCONTROL

0 VIDEOAMPLIFIER

VIDEO OUTPUTTO PPI

TRIGGER TOPPI

120.82


The AN/SPS-6C is an older Set but stillbeing used on destroyers and auxiliary ships.The set is capable of tracking aircraft atlow altitudes. It also is suitable for limitedsurface tracking and navigation. This radarexcels, however, in detecting targets of smallreflective surface at high altitudes. Jet air-craft are detected at altitudes up to 40,000feet and at distances as far out as 60 miles.Large conventional aircraft flying at high al-titudes normally are picked up in the range of70 to 140 miles, whereas smaller targets(such as fighters) are detected when they arebetween 60 and 80 miles away.


The AN/SPS-29( ) is a representative typeof air-search radar found on ships of DDsize and larger. It uses the co-linear broad-side antenna. The radar is used to detecthigh flying aircraft.

RADAR SET AN/SPS-40

The AN/SPS-40 and -40A feature an integralIFF antenna and radar antenna combination,thereby eliminating the need for separate units.Being a light weight and a smaller radarsystem, the AN/SPS-40 and -40A have thecapability of being installed on smaller shipswhich have a 2-dimensional requirement. TheAN/SPS-40 and -40A is a long-range radarused largely on escort ships and destroyers.A general pictorial and nomenclature of unitsare included on the AN/SPS-40 (fig. 6-4).

Radar Sets AN/SPS-37 or -37AAnd AN/SPS-43 or -43A

Both radar sets are high power, very longrange, 2-coordinate air search radars used onlarge ships. They are used for early warningand are capable of detecting fast moving targetsat very long range.

AIR SEARCH 3-COORDINATE RADARS

Among the height-finding radars currentlyinstalled aboard Navy ships, some of the mostcommon are the AN/SPS-8A, AN/SPS-30,AN/SPS-42, AN/SPS-39A, AN/SPS-52, andAN/SPS-48 (v).

110

The 3-coordinate radar functions much likethe 2-coordinate system, but will provide el-evation, in addition to a horizontal searchpattern, a vertical search pattern.

Most radars present only range andbearing,so their beams are narrow in azimuth and broadin the vertical plane. The beams of height-finding radars are quite narrow vertically,as well as in the horizontal plane.

Azimuth is provided as the antenna rotatescontinuously at speeds varying up to 15 RPMor selected data rates. The antenna may becontrolled by the operator for searching ina target sector.

There are two types of height-finding radars,those with stabilized antennas and those withunstabilized antennas. The stabilized radarantennas have a stabilized servosystem whichkeeps the antenna essentially in a horizontalplane regardless of the ship's pitch and roll.(A system of this type is discussed at theend of this chapter.) For those radar antennasthat rotate in the deck plane, the physicalantenna being unstabilized with reference to thehorizontal plane, their departure from thehorizontal plane is noted for each target de-tected and the target data corrected elec-tronically to the horizontal plane. Essentially,the antenna's position is sensed at the momentof data acquisition and corrected electronicallyto stabilized coordinates. Altitude informationdepends upon knowing the exact angular positionof the beam above the horizon and the slantrange to the target.

The elevation scanning is accomplished byone of two methods: (1) mechanical scanningvertically up-and-down with an antenna-feed(rotary-switch) type, while the antenna rotateshorizontally, as in the AN/SPS-8A and AN-/SPS-30 radar sets, or (2) electronic scanningvertically, as in the other radar sets listedabove, by changing the frequency of the trans-mitted beam in discrete increments (steps).Each applied frequency causes the radar beamto be radiated at a different elevation angle.Each step has its ownparticular scanfrequency.As the frequency increases or decreases, sodoes the slant range conversion factor. Acomputer can electronically synchronize theradiated frequency and give electronic scanning3-coordinate radars a high data rate and highangle conversion.

In addition to radar indicators used for2- coordinate radar systems, the 3-coordinatesystems also employ a RH1 (range height


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Figure 6-4.Air-search Radar Set AN/SPS-40 system.

111

120.83


indicator) for air search and interceptor direc-tion. These radars may use noise clutterand pulse compression techniques.

RADAR SET AN/SPS-8A

Radar Set AN/SPS-8A is a high-power,shipboard, height-finding radar system, and maybe used for fighter aircraft direction. Theset presents target height, slant range, bearing,and beacon (IFF) information on remote radarrepeaters and range-height indicators. TheAN/SPS-8A radar is found on large ships(cruisers and carriers mostly) and manydestroyer radar picket ships.

The operational characteristics of the AN-/SPS-8A are: frequency in the 3430 to 3550MHz range, peak power 650 KW, pulse width1 or 2 µ sec, PRR 500 to 1000 PPS, verticalbeam width 1.1° , and horizontal beam width3.5° scanning any vertical 12° sector from0 - 36°. Antenna rotation rates are 1, 2,3, 5, or 10 RPM. The antenna may be made toscan any sector from 30° to 200° horizontally,or it may be trained manually. Maximum rangeusing 1-p sec pulse is 83 miles; with 2-A secit is 165 miles. Minimum range is approx-imately 4,500 yards.

RADAR SET AN/SPS-30

The AN/SPS-30 (fig. 6-5) is a high-power,long-range shipboard radar system for airsearch and interceptor direction of aircraft.It provides information for individual and mul-tiple targets at a fast data rate and presentsthe information on PPI and RHI indicators.The AN/SPS-30 uses a stabilizing servosystemand mechanical scan, the same as the AN/SPS-8A.

RADAR SETS AN/SPS-42 AND -39A

The AN/SPS-42 with minor modificationsbecame the AN/SPS-39A radar set. These3-coordinate radar sets provide three-dimensional position data under all weather conditionson surface and airborne targets. The radarsets provide a means for detecting movingtargets in the presence of obscuring echoesand for detecting targets that would be obscuredue to large antenna side lobe return. Themain functional sections are: the synchronizing,transmitting, receiving, side lobe suppression,

112

antenna positioning, indicating, power distri-bution, waveform converting, and testing.

RADAR SET AN/SPS-52

The AN/SPS-52 (fig. 6-6) is a long-rangeand short-range radar. It is largely installedon guided missile destroyers. It provides thetarget input data required to support the missilesystem and employs air intercept control tech-niques.

The AN/SPS-52 radar utilizes a general-purpose digital computer with both automaticand off-line diagnostic test routines. In addition,it is possible to change the radar programs byuse of the input/output radar printer. Toenhance detection and accuracy, a digital displayindicator is furnished with the radar set.

The radar set employs a planar high gainantenna radar system which allowsa larger partof the radar system to be located in compart-ments below deck.

RADAR SET AN/SPS-48(V)

The AN/SPS-48(V) is a very versatile radarwith many modes of operation. It provides thenecessary target input data required to supportthe Navy surface missile systems (Tartar,Terrier, Talos) and also fills the requirementfor air intercept control. The system isinstalled on guided missile destroyers, frigates,cruisers, and aircraft carriers.

The radar is composed of six major units:antenna, transmitter, receiver, two computersand frequency control group, plus a number ofsmall 'auxiliary power units, data converters,and a control console.

The equipment uses solid state, modularconstruction techniques extensively and oper-ates on 400 hertz primary power. The belowdecks weight of the radar is approximately17,000 pounds and the antenna weights 4,500pounds.

FIRE CONTROL AND MISSILEGUIDANCE RADARS

Electronic equipment in the fire control andmissile guidance systems is closely related tomechanic al and optic al equipment both physicallyand electrically. Although the use of radar ismerely P. part of a whole fire control or missile


A JCONTROL

(CIC)ANTENNA VIDEOINTEGRATOR

WAVEGUIDE COMPONENTS

TRANSMITTER

DG SYNCHROAMPLIFIER

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MODULATOR

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14111.11111.°WSERVO

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Figure 6-5.Air-search Height-finding Radar Set AN/SPS-30 system.

113

// 7

120.84


ANTENNA

o v00000:.. ..,.-".1 .

.

1,.

A: . 0II

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,_I

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TERMINAL BOX DIGITAL DATAINDICATOR

120.85Figure 6-6.Air-search Height-finding Radar Set AN/SPS-52 system.

114


guidance problem, only the radar is discussedin this text.

FIRE CONTROL RADARS

Among the radars used for gun fire controlare radar sets Mk 25, Mk 34 (also designatedAN/SPG-34), Mk 35, AN/SPG-50, and AN/-SPG-52. The Mk 25 and Mk 34 are describedhere.

Mk 25 Mod-( )

The Mk 25 radar (fig. 6-7 an extremelyaccurate equipment, is capable of trackingeither surface or air targets. It is used prin-cipally in 5-inch 38-caliber gun fire controlsystems, but serves equally well for control-ling guns of other calibers.

This equipment operates on 5200 to 10,900MHz frequency band, with a peak power outputof 50 KW and a pulse width of 0.2psec. Itsaccuracy in bearing is ±0.1 °; range in yardsis ±15 yards to ±0.1 percent of the range;and elevation is ±0.1 °.

Early models of the Mk 25 has a maximumrange of 50,000 yards. Those now in use cantrack targets at distances up to 100,000 yards.

Mk 34 Mod-( )

Another fire control radar capable of track-ing either surface or air targets is the Mk34. It was designed for heavy machinegunbatteries, but its most common use today is inthe Mk 63 fire control system that controlsour 3-inch guns. When used in this system,the radar usually is listed as the AN/SPG-34.

Operating in the 5200 to 10,900 MHz fre-quency band with a peak power output of 32KW and a pulse width of 0.5p sec, the Mk 34can track targets at distances greather than30,000 yards. Its maximum range, however,is considerably less than the range of theMk 25.

The antenna for this radar may be found onthe gun platform itself (Mk 63 system) or on aeeparate director.

MISSILE GUIDANCE RADARS

Missile guidance radars currently installedin the fleet are liste,1 here for the purposeof making the reader aware of their existenceand use. The Tartar missile weapons system

115

utilizes Radar Set AN/SPG-51. This radarprovides a continuous wave radiofrequency out-put for the Tartar homing missle.

The Terrier missile weapons system uses1 of 4 radar models. The AN/SPQ-5 and AN/-SPG-55 models are for beam riding Terriermissiles only. The AN/SPG-55A have dualcapabilities. it can be used with Terrierbeam rider or Terrier homing missiles.

The Talos missile weapons system uses tworadar sets: the AN/SPW-2 for beam ridingguidance; and the AN/SPG-49 for tracking.

AUXILIARY EQUIPMENT

The equipment covered in the remainder ofthis chapter is used with the various radarswe have discussed. In some instances, thisauxiliary equipment is in a system that facili-tates the use of radar; in others, it is in theradar system itself.

REPEATERS (INDICATORS)

As the tactics of warfare became moresophisticated, there was more and more evi-dence that the information obtained from radarwould have to be displayed at any one of severalphysically separated stations. The site andweight of the relatively bulky and complexradar console made it unsuitable for remoteinstallations. The need was for a smaller andlighter general-purpose unit, capable of accept-ing inputs from more than one type of radar.To fulfill this need, the present-day remoteindicator (repeater) was developed.

Several types of radar repeaters currentlyinstalled on Navy ships are described in thefollowing topics.

Remote Indicator AN/SPA-4( )

The AN/SPA-4( ) range-azimuth general-purpose indicator (fig. 6-8), a remote PPItype of repeater, is used chiefly for surfacesearch and station keeping. It utilizes astandard 10-inch, flat-face cathode-ray tubeto show range and azimuth of a target. Itis a self-contained unit designed for opera-tion with any standard Navy search radarsystem having a pulse repetition frequencybetween 140 and 3000 PPS. This repeatermay be employed to select radar informationfrom any one of several radar systems. A

/19


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Figure 6 -7. MK 25 radar system.

116

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Figure 6 -8. Range - AzimuthIndicator AN/SPA-4( )

a

120.34

variable (rubber) range control is incorporated,whereby the range may be varied continuouslyfrom 1 to 300 miles.

Remote Indicator AN/SPA-25

The Range-Azimuth Indicator AN/SPA-25(fig. 6-9) is a light-weight transistorizedgeneral-purpose plan position indicator with astandard 10-inch screen designed for operationwith any standard Navy search radar systemhaving a pulse repetition frequency of 10 to5000 PPS (pulse per second). The indicatorcan be employed to display radar information

117

DEADRECKONING

UNIT

120.34Figure 6-9.Range-Azimuth Indicator

AN/SPA-25 with dead reckoningauxiliary unit attached.

from any one of up to seven radar systems,depending on the installation. The AN/SPA-25incorporates continuous range variation from1 to 300 miles, time sharing of the electroniccursor sweep with the video sweep, and asweep offset capability when a Dead ReckoningAuxiliary Unit is employed. Without the deadreckoning unit, the indicator does not have theoffset capability.

Range may be determined in two ways:by using the range rings, which occur at1/2-, 1-, 2-, 5-, 10-, 20-, or 50-mile intervalsfor the operator's selection, or by using theelectronic range strobe and a direct-readingmechanical counter.

Bearing (azimuth) may be determined in tw.)ways: by using the electronic cursor lindazimuth scale or by using the electronic cursorand a direct reading mechanical counter.

/



The AN/SPA-18 is a small, compact, re-mote PPI that presents range and bearing in-formation on a 7-inch screen. It is designedfor installation on small ships where space islimited. The unit is sealed in a sprayproofcabinet, and can be mounted in unprotectedareas either on the bulkhead or on a shelf.

This repeater has a continuously variablerange scale of 2 to 30 miles. It can be operatedwith any standard Navy search radar having aPRR of 57 to 3000 PPS.

Remote Indicator AN/SPA-50A

Range-Azimuth Indicator AN/SPA/50A (fig.6-10) is a transistorized, direct-view, large-screen (22-inch) PPI designed to display theoutput of any standard search-radar systemhaving a pulse rate frequency between 15and 5000 PPS. The indicator unit will displaythe signals from any standard search radar.

It normally uses only the electronic bearingcursor, although a mechanical cursor can beinstalled.

A reflector plotter is shown separately infigure 6-10. A plotting head enables the op-erator to plot the position and motion of aradar target accurately on a planned positionindicator.

The foregoing AN/SPA-4, -25, -18, and -50remote indicators are used primarily withsurface search radars. The following RemoteIndicators AN/SPA-8, -33, -59, -34, -66, -40,-41, and -43 are used more with air searchradars.

AN/SPA-8( ) Remote Indicator

The AN/SPA-8, -8A, -8B, -8C, are general-purpose PPIs employed with shipboard radarsto display range and bearing information. Theserepeaters have off centering capabilities and maybe used as master or remote PPI indicators,as relay search repeat indicators, or as radarrelay search repeat indicators, or as radarrelay search tracking indicators. They havethe capability for being utilized as trackingand repeat indicators with the shipboard sectionof the airborne early warning (AEW) system.

This equipment features (1) continuous-range sweep variation without loss of target,(2) time sharing of the electronic cursor andrange sweeps or the strobe and range sweeps,

118

RADAR DATA REFLECTIONPLOTTER

INDICATOR COVER

I NDI CATOR

120.34Figure 6-10.Range-Azimuth

Indicator AN/SPA-50A.

and (3) sweep and cursor offcentering, whichmake target identification possible without geo-graphic distortion. All these features areincorporated in the indicators. The AN/SPA-8cannot be used. for tracking but is used fora repeater (sometimes called a slave.) TheAN/SPA-8A, -8B, and -8C are single indicatorsused either for tracking purposes or as slaves.Some of its special features follow.

1. Manual offcentering: Any target within250 miles may be centered on the scope.

2. DRA offcentering: Information from theship's dead reckoning analyzer (DRA) may befed to the repeater. This DRA informationcancels own ship's motion, and shows all targets


(including own ship) moving on their truecourses.

3. Electronic cursor and range strobe: Pro-vided with a centered or offcentered electroniccursor and range strobe. Origin of offcenteredcursor and strobe may be controlled inde-pendently from sweep by tracking cranks.

4. Range scale: Rubber range, 4 to 300miles, continuously variable, with a choice ofsix different scale spacings between rangerings.

5. Tracking cranks: Used to position originof strobe or electronic cursor. The trackingcranks may be locked so that the repeatercan be used as a final (repeat) AEW indicator.

Remote Indicators AN/SPA-33 andAN/SPA-59

The AN/SPA-33 and -59 an. remoteindicators (fig. 6-11) which have offcenter ca-pabilities and may be operated either as ageneral-purpose PPI or as a part of an AEWsystem. The only difference between thesetwo sets is that the AN/SPA-33 has a 300 -mile range and the AN/SPA-59 has a 400 -mile range.

They have practically the same controls andcapabilities as the AN/SPA-8A, -8B, -8C.At first glance they look alike, but a closercheck shows that the AN/SPA-33 and AN/SPA-59 have two joysticks (switches) in place ofthe range and bearing cranks on the AN/SPA-8( ). The joystick on the left is for the cursororgin; the one on the right is for the rangestrobe and cursor bearing line. Another dif-ference between the two repeaters is that theAN/SPA-8A, -8B, 8C has provision for a DRA(dead reckoning analyzer) input, whereas theAN/SPA-33 and AN/SPA-59 do not.

Remote Indicators AN/SPA-34

The AN/SPA-34 remote indicator incorpo-rates into a single console the desirable featuresof the AN/SPA-8( ) and the AN/SPA-33. De-pending on the mode of operation selected,it functions as a general-purpose off-centeringtype PPI, as an AEW tracking indicator, or as

AEW repeat indicator. Because of itssize and weight, the AN/SPA-34 is installedonly on ships of DD size and larger.

119

AZIMUTH-RANGEINDICATOR

POWER

c_3(411

`--)''1* PI*I

TRANSFORMER

120.34Figure 6-11.Range-Azimuth IndicatorsAN/SPA-33( ) or AN/SPA-59( ) system.


The AN/SPA-66 (fig. 6-12) has improvedcapabiliqi s with respect to accuracy and willreplace the AN/SPA-34. The Remote IndicatorsAN/SPA-8A, -33, -59, -34, and -66 are alllong range and all perform the same function.They differ somewhat in range scales andaccuracies, however.


The AN/SPA-40 is shipboardequipment usedwith various height-finding radar systems (fig.6-13). The range-height indicator (RHI) displaystarget information by the sweep trace on thescreen. The height of the radar beam ispresented vertically to a maximum of 150,000feet. The range is presented horizontally toa maximum of 300 nautical miles. The RHIsupplies the third-dimension for a ppr s two-dimension target range and azimuth.

The general-purpose indicator AN/SPA-40displays a height-line cursor. This cursor isa straight line painted across the width ofthe screen. The vertical position of the cursoris controlled by the joystick which is centrallylocated a few inches below the bottom of thescreen. The indicator provides an angle mark


t

120.34Figure 6-12.Range-Azimuth

Indicator AN/SPA-66.

cursor used to determine the elevation angleof the target.

The operator may select a delayed sweepof a traverse 30-mile range segment to heights(above sea level) of 0 to 150,000 feet, 50,000to 150,000 feet, or 0 to 70,000 feet. The centerof the range segment may be adjusted any-where between 15 and 285 miles.

The height-determining capabilities of theindicator are produced by an analog computer.After calibration, this computer solves equationsto provide the target height above sea levelwhich is accurate within + 200 feet. The errorsdue to earth curvature and refraction of theradar beam are adequately corrected.


The height-finding Indicator AN/SPA-41 isreplacing the AN/SPA-40. The AN/SPA-40

120

I

120.86Figure 6-13.Height-finding

Indicator AN/SPA-40.

displays either target traces or angle-markcursor, but not both simultaneously as doesthe AN/SPA-41.

Intercept Tracking and ControlGroup AN/SPA-43

The AN/SPA-43 intercept tracking andcontrol computer is designed to aid the aircontroller in conducting air intercepts.

AEW TERMINAL EQUIPMENT

The purpose of the AEW system is (1) toobtain an extended radar horizon by operatingsearch radar equipment in an aircraft at highaltitude, and (2) to make available to surfaceships in the vicinity the extended radar andIFF information thus obtained. This action isaccomplished by transmitting to the surface


craft radio signals containing the radar and IFFinformation. From these signals the originaldisplay at the airborne radar is reproducedon the shipboard indicators.

TV/7 radio receiving sets and a video de-coder currently used in shipboard AEW in-stallations are the AN/SRR-4, the AN/WRR-1,and the KY-71/UPX. A description of eachfollows.

Radio Receiving Set AN/SRR-4

One or two radio receivers, a video de-coder, and a data converter make up the AN/SSR-4 radio receiving set. These units aremounted one above the other in a frameworkrack. The number of receivers is governedby the type of antenna available. If an omni-directional antenna is used with the set, onlyone radio receiver is required.

Because a satisfactory location for an omni-directional antenna is unavailable on mostsurface ships, the usual installation of thisequipment includes two radio receivers andtwo antennas operating as a diversity system.The antennas are mounted on opposite sides ofthe ships's superstructure so that each antennacovers half of the azimuth circle. The antennaand receiver arrangement that intercepts thestrongest signal takes control of the systemautomatically. With this arrangement, receptionof the strongest possible signal is assured atall times.

In either type of installation, the receiversprovide video outputs that are used for displayon the indicators. They also supply decodedsynchronizing pulses for further processingand use in the control of the indicator sweepsand associated IFF and beacon equipment.

Radio Receiving Set AN/WRR-1

The AN/WRR-1 radio receiving set is arefinement of the AN/SRR-4. Although the twosets perform the same functions, they havesomewhat different components. The AN/WRR-1consists of a signal generator, a radio receiver,a signal converter, and a power supply mountedone above the other in the same equipmentcabinet.

For diversity operation, the AN/WRR-1employs a single receiver and two directionalantennas. Each antenna covers half of theazimuth circle. The antenna that intercepts thestrongest signal is connected automatically to

121

the receiver by means of an antenna switchingdevice.

Video Decoder KY-71/UPX

The KY-71/UPX is a video decoder usedin conjunction with the shipboard AEW equip-ment. Radar data and the identification infor-mation (IFF) are transmitted on a commonlink, and it is the function of this unit to separatethe data into separate circuits.

By using this unit in conjunction with otherstandard identification data distribution acces-sories, an operator may display the identificationdata with or without the radar information. Healso may display radar information without theidentification data. Simultaneously, the otheroperators are able to select and display identi-fication and/or radar data as they desire.

IFF EQUIPMENT

Today's high-speed aircraft present a criti-cal problem in detection, identification, tracking,and evaluation. When enemy aircraft areapproaching, they must be detected and identifiedat the greatest possible distance in order toprovide ample time for initiating appropriateaction.

The Selective Identification Feature (SIF)is a recent development that makes the systemof identifying friendly units much more secureand more positive. The SIF operates in con-junction with the Mk X system but is a separatepiece of equipment.

Currently, the Mk X IFF system is in com-mon worldwide use by both civilian and military.It received wide distribution during and afterWorld War II. Today, pursuit effort is directedto the Mk XII system that provides greaterflexibility and security by use of more extensiveand complicated interrogations and replies.

Among the various models of IFF equipmentcurrently installed aboard ships are theAN/UPX-1( ), AN/UPX-11, AN/UPX-12( ),AN/UPX-17, AN/UPA-24 ( ), and AN/UPA-38( ). Of these six models, only the AN/UPX-1( ) and the AN/UPA-24( ) are discussed inthis text.

Radar Recognition Set AN/UPX-1( )

The AN/UPX-1( ) radar interrogator-recog-nition set (fig. 6-14) is designed to operatein conjunction with shipboard radar equipment.


RECEIVER-TRANSMITTER

3:5!;' ' 'a ' - , ,

-ile.' , ii e: 011111 014

_...._,--..._ ..co,zr,,r.,,A T,t-_,I.7.`41kfil I.

7 . l' .41

' V..:*';`.' edm' acit...

-; .1PP , -4.I. s 4' , 1

3.. . ,

VIDEO AMPLIFIER

CODER-DECODER

RAD441$0t,....CoNTROL.

120.38Figure 6-14.Radar Recognition Set AN/UPX-1( ).

122


VIDEO DECODER

Figure 6-15.Decoder Group AN/UPA-24( ).

It uses the radar display for presentation ofits IFF data. Its antenna is either integralto or slaved with the associated radar antenna.

The AN/UPX-1( ) is used chiefly for chal-lenging unidentified radar targets. It also canbe used to further identify friendly targets asspecific aircraft or ships, thereby providingadditional security and useful tactical infor-mation.

Although it is not discussed in detail in thistext, the AN/UPX-12( ) is the shipborne quip-ment that responds to the challenges transmittedby the AN/UPX-1( ).

Decoder Group AN/UPA-24( )

The AN/UPA-24( ) decoder group, shownin figure 6-15; facilitates the interpretation ofcoded IFF signals received from a radarrecognition set. It selects a coded videopulse-train from the recognition set and pre-sents the coded signal to a decode network. Ifthe pulse-train is coded correctly, an indicationin the form of a single decode pulse is displayedon the radar indicator. If the pulse-train is

123

RADARSET CONTROL

120.39

coded incorrectly, a decode pulse is unavailablefor presentation.

The AN/UPA-24( ) permits the presentationof the coded or decoded IFF signal alone, theradar signal alone, or the radar signal mixedwith either coded or decoded IFF signals. Italso provides the means for controlling theoperation of the recognition set.

ANTENNA STABILIZATIONDATA EQUIPMENT

The AN /SSQ -14 stabilization data set is avital link in establishing a stabilized antennaplatform. It supplies a synchro signal indicationof the angular displacement of the ship's deck,with respect to the horizontal, as the shippitches and rolls. Two gyro units, one associatedwith pitch and the other with roll, are mountedon a horizontal platform, their output axesvertical. Output of these gyro unitswiththeir associated servo loopsmaintain thisplatform in a horizontal position. By means oftransmitting synchros, geared to the pitch and

1.A 7


roll axes of the stabilized platform, the pitchand roll angular correction is sent to thedesired destination (the system that keepsthe radar antenna stabilized, for example).

Other equipment furnishing stabilization data(roll and pitch signals) are the AN/SSQ-4,Mk 8 (Mods 2 and 4) stable elements, andthe Sperry Mk 19 gyrocompass.

CHAPTER 7

SONAR

Sonar (derived from the words SOund Nav-igation And Ranging) uses pulsed transmissionof sound waves in water for detecting, tracking,and ranging of underwater objects, and isanalogous to radar which uses pulsed trans-mission of radio waves to detect, track, anddetermine the range of objects on the surfaceor in the air. Because ships afloat are partiallysubmerged, sonar is used for the detection ofsurface ships and submarines, for measuringwater depths (depth sounding), and also asa navigational aid. Commercially, sonar isused for detecting shoals of fish.

Sonar equipment may be of an active nature,transmitting sound energy into the water andthen obtaining bearing and range informationfrom returning target echoes; or it may beof a passive nature, depending upon the soundoriginating from the target (such as screwcavitation, machinery noise, and the like) forbearing information.

Before discussing the various sonars, let'sbriefly review some of the basic principlesof sound.

SOUND

Everything you hear is a sound. Thisstatement does not mean, however, that whenyou hear nothing there is no sound, becausemany sounds are beyond the frequency rangeof the human ear. Sound is a mechanicaldisturbance of the surrounding medium andmay be divided into three frequency groups.They are (1) ultra sonic thos t frequencies abovethe audiofrequency range; (2) sonicthose fre-quencies within the audiofrequency range, and (3)subsonicthose frequencies below the audiofre-quency range. As stated in chapter 2, theaudio range is from approximately 15 to 20,000hertz. The actual range of frequencies that

125

the human ear can detect varies with theindividuals themselves.

To make use of sound, it is necessary tohave a sound source, a medium for the soundto travel through (sound does not travel ina vacuum), and a detector to pick up the soundso that information can be obtained from it.

GENERATION AND TRANSMISSIONOF SOUND

Any object that vibrates back and forthdisturbs the material surrounding it, whetherthat material is a gas, solid, or liquid. Theobject that vibrates is the sound source (fig.7 -1). It may be a bell, a loudspeaker, or asonar transducer.

A transducer is any device that convertsenergy from one form to another. In sonar,the transducer contains a diaphragm that is madeto vibrate at the frequency of an applied voltage.When the diaphragm moves out, the mediumnext to it is compressed. As the diaphragmmoves back, the particles in the medium moveapart, causing a rarefaction or low pressurearea next to the diaphragm. When the diaphragmmoves out again, a new compression is produced.The out-and-in movement of the diaphragmcontinues, and the alternate compressions andrarefactions spread in a series of waves calledcompression waves. Compression waves, pro-pagated through a medium, are sound waves.

The number of complete cycles (one com-pression and one rarefaction) completed ineach second is the frequency of sound wavetrain. This frequency, of necessity, is thefrequency of the vibrating body (source). Thespeed at which the sound wave train travelsoutward depends upon the nature of the materialor medium surrounding the body. In 35 percentsalt water, sound travels at approximately 4800feet per second at 39°F.


TRANSDUCER

RAREFACTION

COMPRESSION

VIBRATIONS

WAVELENGTH /if(ONE COMPLETE CYCLE)

4.221Figure 7-1.Producing sound waves.

VELOCITY PROFILE OF THE OCEAN

The temperature, pressure, and salinityof sea water all affect the velocity of soundin the medium of the ocean. In each case,as the values of these variables increase,so does the speed of sound increase, or: highertemperatuie = higher velocity; higher pressure=higher velocity; and higher salinity = highervelocity.

Because sound will refract, or "bend" fromareas of high velocity to those of low velocity,oceanographers say the "sound is lazy." Eachof the variables affecting the speed of soundin ocean water is therefore important.

The effects of temperature, pressure, andsalinity combine to form a velocity profilefor the ocean (figure 7-2). Temperature isthe variable exerting the greatest impact uponvelocity near the surface. Relatively abrupt

126

FEET PER SECOND

(FPS) 4700 41100 4900 3000 5100 3200

500 SOILNO CHANNgl. 4111S _ _ 1

100 0

IS 00

2000

VELOCITY PROFILE(COMBINATION OF

TEMPERATUREPRESSURE

SALINITY)

120.87Figure 7-2.Velocity profile for the ocean.

and large changes may occur in the firstfew hundred feet of depth. The temperatureof the ocean levels off, often after the firstfew thousand fathoms, and remains at about30°F., so that it is less important as a variableat great depths. Pressure as shown on thegraph, is a steadily increasing effect, becominggreater as the depth increases and therebyincreasing velocity in a linear function. Salinityvaries less throughout the deep ocean areas,and has relatively less effect on the speed ofsound than temperature and pressure.

The velocity profile, resulting from theseeffects, shows a point of minimum velocity,normally occurring between 500 and 700 fathomsbelow the surface. This area, where the speedof sound is lowest, is called the deep soundchannel axis. Below the channel, pressurecauses velocity to increase, and above it, tem-perature has the same tendency. Within thisarea, low frequency sounds can travel thousandsof r-iles at the reduced velocities they seek.

SOUND PATHS AND MODESOF DETECTION

Most submarine detection by shipboardsonars is made using the surface duct path ofsound travel. This is so, because most sonarsin today's ships are capable of only this modeof operation and because submarines operatein the first few hundred feet of water, or inthe surface duct. As the ocean's sound velocityprofile shows, temperature has much moreeffect near the surface than do either of theother variables causing sound to refract.

Chapter 7SONAR

Information about the sea's temperature isgained from a device called a bathythermo-graph, which is described in the next chapter.

Thermal Gradients

Thermal gradients are indices of the changesin temperature vs depth near the surface.There are three types of thermal gradients:

NEGATIVE GRADIENTS.A negative gradi-ent exists where an increase in depth is ac-companied by a decrease in temperature. Soundin a negative gradient will bend down, seekingthe lower velocity caused by cooler water(fig. 7-3).

POSITIVE GRADIENT.A positive gradientis one where cooler water overlies warm, andan increase in depth yields a rise in temperature.Sound will refract upward toward the surfacewhere the cooler water produces lower velo-cities (fig. 7-4).

ISOTHERMALS.Isothermals are the thirdtype of gradient, and exist where a changein depth shows no change in temperature. Soundin an isothermal will bend slightly upwardbecause of the effect of pressure. Lowerpressures result in lower velocities; the reducedpressure at the surface will be sought by soundwhere temperature does not change (fig. 7-5).

Layer Depth

Layer depth is defined as the "greatestdepth at which the maximum temperature is

DEGREES FAHRENHEIT(DEGREES F.1-0- 40 50 60 70 00 00

SOUNO SEAMSENT DOWNTOWANOCOOLERWATER

71.31(120C)Figure 7-3.Negative gradient.

127

43/

DEGREES F 40 50 60

YARDS

100

I-

W 200IL

xI- 300

0

400

MOO 1500

70 80 90

2000 2500 5000

SOUNO SEAMSENT UPTOWAROCOOLERWATER POSITIVE

GRAOIENT

71.30(120C)Figure 7-4.Positive gradient.

found." Layer depths are the most importantsingle factor determining sonar ranges in thesurface duct. A layer can be caused by anisothermal condition terminating in a negativegradient (fig. 7-6) or a positive gradient intoa negative (fig. 7-7). Sound in either the isother-mal or positive gradients will bend upwardcausing it to return to the surface; while soundin negative gradients will bend downward re-sulting in shorter ranges. Generally, the deeperthe layer, the greater the surface duct sonarrange (figs. 7-6 & 7-7).

BOTTOM BOUNCE.For long-range searchin water depths over 500 fathoms, a bottomreflection or bottom bounce mode of operationmay be conducted with newer sonar equipments.

DEGREES F 4.. 40 50 60 70 80 90

YARDS

100

V. zoo3

f,L, 3000

400

000

*,5:twAtip.500 20 55

SOUNO SEAMSENT SLIGHTLYUP SY PRESSURE

ISOTHERMAL

0

120.88Figure 7-5.Isothermal gradient.


DEGREES F 40 SO GO 70 SO 90 DEGREES F. 40

120.89Figure 7-6.Isothermal gradient into

a negative gradient.

The bottom bounce effect is accomplished byusing automatically selected transducer anglesto reflect the sound beam up from the oceanfloor. Preselected transmission angles causesound to be reflected from the bottom into regionsnot normally possible with the velocity structure.The bottom bounce effect is illustrated infigure 7-8.

Bottom bounce is in part successful becausethe angle of the ray path (0° to 42°) is suchthat the sound energy is affected to a lesserdegree by velocity changes than the morenearly horizontal ray paths of other transmissionmodes. Transmission loss for bottom bouncecan usually be predicted on the combinedbasis of: (1) spherical spreading along theslant range to the receiver; (2) absorption lossdependent on water temperature and frequencyof sound source; (3) a loss associated with

60 60 70 60 90

120. PFigure 7-7.Positive gradient into

a negative gradient.

successive bottom reflections; and (4) bottomcomposition. Long range paths can occurwith water depths greater than 1000 fathomsdepending on bottom slope, but at shallowerdepths multiple bounce paths develop whichproduce high intensity loss. For this reason,bottom bounce is not used in less than 500fathoms. It is estimated that 85 percent ofthe ocean is deeper than 1000 fathoms, andbottom slopes are generally less than or equalto one degree (as an average figure). However,the slope must be 3 degrees or less beforeany bottom bounce operation is possible. Onthis basis, relatively steep angles can be usedfor single bottom reflection to ranges of approxi-mately 20,000 yards. With steep grazingangles, transmission is relatively free fromthermal effects in the surface region and themajor part of the sound path is in nearly stablewater.

SOUND SOURCE

51.7(120C)Figure 7-8.Bottom bounce.

128

/3.2

t

Chapter 7SONAR

Each bottom reflection is received froma limited range, and the maximum range ofreception for each reflection is defined by thelimiting ray which depends on bottom slope andthe sound velocity profile. The minimum rangeof reception is determined by the criticalangle ray. Where rays strike the bottom atangles more horizontal than the critical angleray, there is perfect reflection, and the intervalof best reception is between the limiting rayand the critical angle ray.

The rays which strike the bottom at anglessteeper than the critical angle ray are partiallyrefracted into the bottom with energy loss;this loss increases with increasing frequencyof the source and grazing angle.

CONVERGENCE ZONE DETECTION.Con-vergence zone detection (fig. 7-9) is made

25-35NAUTICAL MILE AVERAGE

FEET PERSECOND(FPS) - 4700 4500 400 5000 11)(1

500

1000

1500

2000

VELOCITY ATDEPTH BECOMESEQUAL TO ORGREATER THANTHAT AT SURFACE

51.8.1(120C)Figure 7-9.Convergence zone detection

(steep angle).

possible by a phenomenon in the ocean whichcauses sound, after reaching a great depth,to return to the surface approximately thirtymiles from its source. In discussing thismode of detection, and the deep sound channeldetection in the following paragraph, we areno longer concerned with the shallow waterand layer depths discussed. above. In orderfor sound to travel the convergence zone path,two criteria must be met; (1) The sound musttravel through the point of minimum velocity,or deep sound channel, at a steep angle (if it

129

reaches this area at a shallow angle as shownin figure 7-10, it will be trapped, or ducted);and (2) the sound must reach a depth at whichthe velocity profile (fig. 7-9) shows a speedequal to or greater than that at the surface.When this point is reached, the effect on velocitydue to pressure will cause the sound to returnby a path similar to the one it followed goingdown.

DEEP SOUND CHANNEL DETECTION.Thefourth path of sound travel again involves thevelocity profile. If sound enters the deep soundchannel, in the vicinity of 500-700 fathoms,at a shallow angle, it can be trapped sinceit tends to remain at low velocity. The shallowangle allows the sound to be influenced graduallyand once trapped, low frequency sounds canbe ducted over thousands of miles. Systemsusing hydrophones on the ocean floor make useof this path of sound travel.

TRANSDUCERS

A transducer is a device that converts energyfrom one form into another. An example is thechanging of electrical energy into mechanicalenergy or vice versa. This is the principle bywhich sonar transducers operate.

MAGNETOSTRICTIVE PROCESS

Magnetostriction is a process wherebychanges occur in metals when they are subjected

SOUNDSOURCE

SHALLOW ANGLE HYDROPHONE

DEEP SOUND CHANNEL

OCEAN FLOOR VELOCITY PROFILE

51.8.2(120C)Figure 7-10.Convergence zone detection

(shallow angle).


to a magnetic field. If a tube made of nickelis placed in a magnetic field, for example,it changes length as a result of the magneto-strictive effect.

The elements of the transducer each havenickel laminations pressed in a thermoplasticmaterial and wrapped with a coil of wire. Per-manent magnets are su mounted that they provideenergy for polarizing the nickel, thus estab-lishing an operating bias for the system. Duringtransmission when alternating current is. passedthrough the coil, the tubes shorten on lengthenwith each half-cycle of the alternating current.The resultant displacement of a chaphragmattached to the ends of the nickel tubes causessound frequency vibration to be transmitteathrough the water.

ELECTROSTRICTIVE PROCESS

The electrostrictive process in transducersrelies on the ability of certain manmade ceram-ics to produce a mechanical force when a volt-age is applied; or conversely, produce a voltagewhen a mechanical force is applied.

When ferroelectric material such as leadzirconate titanate compound is placed in anelectric field, it changes in dimensions. Thiseffect is very similar to the piezoelectric effectfound in some natural crystals whose oscillationschange in step with changing electrical ormechanical forces. For the ceramic materialto acquire the piezoelectric characteristic how-ever, an extremely high voltage is initiallyapplied to the material for several minutes topolarize it permanently to give an nperatingbias to the system. Then, as alternating currentis applied, the material will shorten or lengthenwith each half-cycle to set up mechanicalvibrations at the desired frequency.

Ceramic tranducers have high sensitivity,high stability with changing temperature andpressure, and relatively low cost. Their greatestadvantage lies in the mechanical propertiesof the material, which allow construction ofalmost any reasonable shape or size.

CYLINDRICAL ARRAY

A cylindrical array (fig. 7-11) illustratesa transducer made up of many individual ele-ments stacked in vertical columns called staves.Each stave (shaded area, fig. 7-11) has nineelements, and the total number of staves ar-ranged in cyclindrical form gives a 360° search

130

SHADED AREA SHOWINGONE STAVE WITH NINE

CERAMIC ELEMENTS

120.91Figure 7-11.Cylindrical array arrangement.

in azimuth. The physical size of the individualelements in the transducer is related to theoperating frequency and power output. Thepower output required determines the physicaldimensions of the array.

TYPES OF SONAR

The two general types of sonar are referredto as active sonar and passive sonar. Theactive sonar is a transmitting (pinging) andreceiving apparatus. It is capable of trans-mitting underwater sounds that strike targetsand are returned in the form of echoes. Theechoes so returned are received and presentedin a manner to indicate the range and bearingof the target. Passive sonars do not transmitsound. They merely listen for sounds producedby the target to obtain accurate bearing. Esti-mated range information can be Obtained bytriangulation.

Active sonars normally are associated withsurface ships, whereas passive sonars are usedprimarily by submarines. Submarines alsohave active sonars. Integrated sonar systemsaboard ASW vessels often employ passive equip-ment in conjunction with active equipment toextend their capabilities.

PASSIVE SONAR

Passive sonar depends entirely upon the tar-get's noise as the sound source. So efficient

/3 V

Chapter 7SONAR

is passive sonar that sounds many miles awaymay be identified and their source tracked.

An electoacoustic transducer, called thehydrophone (fig. 7-12), is used to detect under-water sounds. The hydrophone contains either

72.62Figure 7-12.Hydrophone.

a ceramic material or a metal alloy that reactsto mehcanical stress. When subjected to stress,such as that caused by sound waves strikingthe hydrophone, the material vibrates or under-goes a change in size. These vibrations orchanges in size cause a small voltage outputfrom the hydrophone. The frequency of theoutput voltage is essentially the same as thatof the received sound waves.

Passive sonars at one time used the singleline hydrophone system, which was trainedphysically to obtain bearing information. Today' spassive sonars utilize a hydrophone array,consisting of a number of hydrophones connectedtogether around a cylinder. Although the arrayis not trained physically, a directional effectis obtained electrically by employing a compen-sator switch. The switch is rotated and posi-tioned by the sonar operator at the controlconsole. A simplified block diapgram of thearray type of passive sonar is shown in figure7-13.

SCAN

SW

PRE.

AMP.

HYOROPHONE

COMP.

SW.

LAG

LINES

AUDIO

AMP.IND

76.55Figure 7-13.Block diagram of array

type of passive sonar.

When the sound waves are received by theindividual hydrophones, they are converted toelectrical energy. The electrical signal fromeach hydrophone in the array is then fed to aseparate preamplifier. After amplification, thesignals are collected by the compensator switchas it samples the output of each preamplifier.From the switch, the collected signals enterthe lag lines. The position of the switch indicatesthe direction from which signals are being re-ceived.

131

The circular arrangement of the hydrophonescauses the signals to be out of phase with oneanother at the output of the preamplifiers. Forthe signals to be usable, they must be placedin phase with one another. This action isaccomplished in the lag lines by delaying thefirst received signals a proportional amountuntil the last received signals catch up. Oncethe signals are in phase, they are additive. Asa result, we have a strong signal to feed to theaudio amplifier.

From the audio amplifier, the signal is fedto the indicator, and there it is presented bothvisually and audibly.

ACTIVE SONAR

The major components of a simplifiedactivesonar system are similar to those seen infigure '7-14. In this set, the sonar transmitterconsists of an audiofrequency oscillator andan amplifier. The transmitter feeds a shortpowerful pulse to the transducer for trans-mission into the water. The signal pattern istransmitted in 360° of azimuth in an omni-directional pulse.

The transducer converts electrical signalsinto sound waves. It also changes the receivedsound echoes back to electrical signals.

Another important part of the active sonarsystem is the sonar receiver. It functionsmuch the same as the conventional super-heterodyne receiver. In this unit, the extremelysmall audiofrequency electrical signals result-ing from the echo are amplified and convertedto stronger signals that can be heard througha loudspeaker. The sonar receiver also feedsthe amplified echo signal into the variousvideo indicating devices such as the cathode-ray tube (CRT) on the control indicator.

/35


SONAR

INDICATOR

RECEIVER

TRANSMITTER

TRANSDUCER

71.47Figure 7-14.Simplified active sonar system.

Types of Transmission Modes

There are two widely used transmissionmodes. These are the omnidirectional trans-mission mode (ODT) and the rotational direc-tion transmission mode (RDT). Omnidirectionaltransmission involves the radiation of soundenergy in all directions to produce a 360°circular radiation pattern. This nondirectionalsonar tranducer also receives returning echoesfrom all directions and converts them to in-telligible video and audio information, thusproviding indications of all underwater objectsaround the ship.

Rotational direction transmission involvesthe transmission of a directional beam whichcan be pointed through 360 degrees. An analogouseffect can be obtained by holding a flashlighthorizontally and turning it on and off (pulsing)while rotating yourself clockwise to completea circle (azimuth). By electronically scanningin this manner, the transducer can also receiveechoes from all degrees of azimuth.

Transmission

The functions of the principal componentsin a scanning sonar system are understood best

by breaking them down into three basic opera-tions: transmission, reception, and presenta-tion. In the following discussion, refer to theblock diagram in figure 7-15. This illustrationshows the keying pulses and transmitted outputsignals in solid lines; returning echo signalsare indicated by dotted lines.

Initiating keying pulses is an automaticfunction of the keying circuits in the sonarcontrol indicator. The time between pulses,as well as the duration of each pulse, is deter-mined by the position of the controls on theindicator console.

A pulse originating in the keying circuits issent simultaneously to the transmit-receive(T/R) switch and to the transmitter. Whenthis pulse is received by the transmit - receiveswitch, the transducer is switched from thereceiver circuits to the transmitter circuits,and it remains connected there until the out-going signal is transmitted. At the end of thetransmission, the switch automatically recon-nects the transducer to the receiver circuits.

The key pulse triggers the audio oscillatorin the sonar transmitter. The signal generatedby the oscillator is amplified to the requiredpower level, and then is delivered to the trans-ducer via the transmit-receive switch. Thesignal is applied simultaneously to all of thetransducer staves (fig. 7-11), and a sound pulseis emitted in all directions.

The acoustical wave released into the waterby the tranducer continues outward, ever ex-panding as it goes. When this wave strikesan object capable of reflecting the sound, asmall portion is reflected back to the trans-ducer.

132

Reception

When a portion of the transmitted signal isreturned to the transducer, it is converted toan electrical signal for use by the equipment.After conversion the signal is fed to a pre-amplifier (via the transmit-receive switch)for amplification to a usable energy level.Each stave of the transducer has its own pre-amplifier. The outputs of the preamplifiersare sent to the transducer scanning assemblyfor distribution to the receiver. The transducerscanning assembly contains a video scanningswitch and an audio scanning switch.

The video scanner rotates continuously,thereby sampling the echoes from each elementof the transducer, giving an effect similar to

154

Y.

6.

Chapter 7SONAR

VIDEO SIGNAL

AUDIO SIGNAL

TRANSDUCERSCANNINGASSEMBLY

PREAMPS.]

4

RECEIVED

SIGNAL

CONTROL INDICATOR CONSOLE

!CRT%

LS I

i CONTROL II AND

KEYING I

I CIRCUITS I

KEYING

z

TRANSMIT-RECEIVESWITCH

PULSE

TRANSMITTER

TRANSMITTED

TRANSDUCER

SIGNAL

ACOUSTIC SIGNAL

ECHO

120.41Figure 7-15.Block diagram of a basic scanning sonar system.

that produced by a rapidly rotating and highlydirectional transducer. The received signalat the receiver input comprises both videoand audio signals (fig. 7-15).

The audio scanner does not rotate continu-ously. It is positioned as desired by the sonaroperator. In this manner, audio signals can bereceived from any particular direction. Theoutput from the audio scanning switch is appliedto the audio channel of the receiver.

In the receiver, the video and audio signalsare detected and amplified, as necessary, forpresentation in the control indicator console.

133

3 7

Presentation

For the returning echo to be of any value,it must be presented in such a manner that theinformation it represents can be interpreted.

Before entering the receiver, the returningecho is converted from acoustical energy toelectrical energy in the transducer, from whichit is sent to the video scanning switch (notshown). The rotation of this switch is syn-chronized with the sweep presentatation, andthe echo appears as a brightening of the sweepon the CRT at the bearing from which it


originated. The sweep, seen on the CRT asan expanding circle, is adjusted to expand ata rate proportional to half the speed of soundin water. This adjustment is necessary becausethe transmitted pulse must travel to the targetand return.

For a target 2000 yards away, as an example,the sound must travel a distance of 4000 yards.By adjusting the sweep on the CRT to travel athalf the speed of sound, the sweep reaches apoint equivalent to 2000 yards from the centerof the scope at the same time the sound energyreturns to the transducer. This energy, orecho, produces a brightening on the scope at adistance from the scope center. The distancecan be measured to find the range to the target.

The audio signal is sent from the receiverto the loudspeaker or headset. Together withthe CRT information, the audio intelligence isutilized in ascertaining the nature of the target.

A line called the cursor is printed on thescope after each sweep. Because of the longpersistency of the cathode-ray tube, the tar-get echo remains visible for a short time todetermine range and bearing. The operatorcan control the direction (bearing) and length(range) of the cursor with the bearing andrange handwheels. By placing the tip of thecursor on the target, he can read the target'strue bearing and range from the dials locatedon the sonar control indicator.

Various switchs and controls also are lo-cated on the sonar control indicator. Theirpurpose is to give a better target presenta-tion. These switches and controls are explainedin the equipment technical manual suppliedwith each sonar equipment.

VARIABLE DEPTH SONAR

The thermal layer in the ocean is one ofthe problems affecting the ability of sonarto detect and maintain contact with a submarine.These layers reflect or bend sonar signalsso, that a submarine lying or cruising belowa particular layer may go undetected. Toovercome this obstacle, the variable depthsonar (VDS) was developed.

To differentiate between the two types ofsonars, the conventional sonars are sometimes

referred to as hull systems while the VDS arereferred to as towed transducer systems.

Becausea combinedprovides cotargets.adequate cogets.)

the target depth usually is unknown,use of VDS and hull-mounted sonarverage for both deep and shallow

(VDS alone does not always giveverage for shallow operating tar-

When used in this manner, there are fouroperating conditions which can be selectedby the operator. They are (1) hull transmitand receive, (2) towed transmit and receive,(3) towed transmit and hull receive, and (4)hull transmit and towed receive. Operatingfrequency of the towed transducer is derivedfrom the existing shipboard sonar equipment.

The general function of the VDS equipmentis to make use of the pulsed power for thetransmission of sonar signals by the ship-board sonar equipment. This pulsed poweris transmitted via the electrical cable thatextends through the center of the mechanicalarmor of the tow cable to the towed transducer.The transducer, operating on acoustic prin-ciples, converts the electrical energy to mechan-ical energy and transmits it to the surroundingwater. When the transmitted sound wave strikesan object with adequate reflective characteris-tics, a portion of the total energy is reflectedback to the towed transducer. The directionof the echo indicates the bearing of the object.The transducer then converts the mechanicalenergy of the echo into an electrical signal,whose magnitude and phase are determinedby the intensity of the received echo. Thiselectrical signal is transmitted up through thetow cable to the sonar system for displayand interpretation.

A later type of VDS is the IVDS (independentvariable depth sonar) which has its own hoistand sonar system independent of ships sonarsystem.

MINE HUNTING SONAR

Until relatively recent years minesweepingwas the only available means for eliminatingthe danger of mines in naval warfare. It stillis one of the prime methods of removing orneutralizing these hazards to safe navigation,but supplementing this plan is the procedure of

134

/3ir

Chapter 7SONAR

detecting the actual location of the mines sothat sweeping operations may be employed inonly the exact required locations.

In many instances, the known location ofmines is sufficient to neutralize their effective-ness. Marking the location of a minefieldwith buoys permits ship traffic to remain clearof the danger area. Thus no further actionis required when this obstruction can be by-passed safely and expeditiously.

Mine hunting includes all measures fordetecting, accurately locating, identifying, andclearing mines individually. The location ofmines by means of high-resolution, short-pulse sonar, mine detecting sets is becomingincreasingly successful. Mine hunting sonaraids in distinguishing between mines and theaccumulated debris cluttering the bottoms ofbusy harbors and their approaches.

FATHOMETER (DEPTH-SOUNDING SONAR)

The depth of the sea can be measured byseveral methods. One is by dropping a weighted,distance-marked line (lead line) to the bottomof the water, and observing the depth directlyfrom the line. The chief disadvantage of thismethod of determining depth is that its use islimited to very shallow water.

Sound is another method of measuring depth.A sound pulse is transmitted, aimed at thebottom of the sea, and its echo is heard. Thetime between transmission and echo receptionis considered in relation to the speed of soundthrough water, then the depth is determinedthereby. Depth-sounding sonars, or fatho-meters, apply this principle of sound physicsto determine the distance to the bottom of thesea.

Usually, depth-sounding sonars are calledfathometers. They operate on the same prin-ciple as subm. rine-detecting sonars, but, be-cause of the reduced power requirement, theyare much smaller in size and have fewercomponents. A representative block diagram of

135

CRTINDICATOR RECORDER

1,RECEIVER

KEYINGCONTROL

TRANSMITTER

TRANSDUCER

120.42Figure 7-16.Block diagram of depth-sounding

sonar system.

a depth-sounding sonar system is shown infigure 7-16.

When the system is keyed (either automatic-ally or manually), a pulse is generated in thetransmitter. The pulse is amplified and appliedsimultaneously to the transducer and the re-ceiver circuit. The transducer converts thesignal to acoustical energy and transmits itdownward into the water.

The returned bottom echo is convertedby the transducer to electrical energy andapplied to the receiver. The received signalsare amplified and presented on the recorderor the cathode-ray tube indicator.

SONAR ACCESSORIES

In many instances, it is difficult to catego-rize an equipment as an accessory becauseof its role in the overall sonar system. Forexample, the remote indicator is seldom thoughtof as an accessory. It is not essential to theoperation of the basic sonar system, con-sequently it is an accessory. Thebathythermo-graph is isolated from any sonar system.The information obtained from the bathythe rmo-graph is necessary, however, for the effectiveutilization of sonar.

The foregoing accessories and others aredescribed and illustrated in the next chapter.

/ 3 1

CHAPTER 8

SONAR EQUIPMENT

The future success of the Navy in maintainingcontrol of the seas will depend to a considerableextent on her ability to cope with the high-speednuclear submarines.

Immediate and compelling, then, is theneed for submarine detection capabilities atsignificantly increased ranges, with reliableperformance independent of the water char-acteristics of any particular operating area.

Sonar sets are used for detecting, tracking,displaying underwater targets, and navigation.This is accomplished by echo ranging and passivelistening. Target presentation is providedvisually on indicator scopes and audibly byloudspeakers or headphones.

Passive (listening) sonars are used moreaboard submarines and at harbor defenseactivities than aboard ships. Therefore, theyare not covered in as much detail in thischapter as are the active sonars.

SURFACE SHIP EQUIPMENTS

Sonar equipment installed on board surfaceships include hull-mounted equipments, variabledepth equipments, mine hunting equipments,fathometers and sonar accessories. Repre-sentative types of these equipments follow.

SONAR SET AN/SQS-4( )

The AN/SQS-4( ) search sonar is an oldset which is found on a few ships of the activefleet. It operates on the azimuth scanningprinciple. Like other scanning sonars, it isan omnidirectional echo ranging and passivelistening equipment. It provides a continuousvideo display of acoustic reception in alldirections, and an audio response from anydesired single direction.

The AN/SQS-4 also has a built-in test setand control unit. The test set and its control

136

provide facilities for testing and calibratingthe sonar system, and for training sonaroperators in the use of the system.

Most of the AN/SQS-4 equipments have beenmodified. The modifications (identified asMODS 1 through 4) can operate in the RDTmode and have received new designations asshown in table 8-1.

Table 8 -1

OPERATINGFREQUENCY

NEWDESIGNATION

OLDDESIGNATION

8 kHz

10 kHz

12 kHz

14 kHz

AN/SQS-29 ( )

AN/SQS-30 ( )

AN/SQS-31 ( )

AN/SQS-32 ( )

AN/SQS-4Mod 1

AN/SQS-4Mod 2

AN/SQS-4Mod 3

AN/SQS-4Mod 4

SONAR SETS AN/SQS-29( ) TO -32( )

The AN/SQS-29( ) to -32 sonar sets areidentical except for frequency determiningcomponents. Because of this similarity, onlythe AN/SQS-31 (fig. 8-1) is shown as repre-sentative of all of these equipments. Thefrequency bands are spaced so that interferencebetween sets is held to a minimum. Thenominal operating frequency of each is listedin table 8-1.

These sonar sets offer a choice of pulselengths, namely 2, 7, 30, or 120 milliseconds.The pulse length controls the amount of energyleaving the transducer. The power output canvary between 4 KW in handkey modes to50 KW in normal echo ranging modes.

196

Chapter 8SONAR EQUIPMENT

TRANSMITTERPOWER

AMPLIFIER (m)

TRANSMITBEAM

CONTROL*

TRANSMITTERPOWER

AMPLIFIER (II)

TRANSMITBEAM

CONTROL *

TRANSMITTER .-7:1POWER

AMPLIFIER (L)

CONTROL*

TRANSMITBEAM :17.1

=tINTERCONNECTING

BOX

JUNCTIONRELAY &

BOX *

VOS

POWER DISTRIBUTIONPANEL

MOTOR-GENERATOR

CAPACITORASSEMBLY

CONTRO-POWER

L

SUPPLY

(I MOTOR -GENERATOR

POWER OISTRIBUTION TRANSFORMERS

(11)MOTOR-G EN ERATOR

CONTROL-PROGRAMMER

i.

MOTOR -GENERATOR

TRANSMITBEAM

(CONTROL*VOS

I NOICATOR *CONTROL-

R- SK -1

SIGNAL OATACONVERTER

CONTROL*

TRANSMITBEAM

PROGRAMMER-LRECORDW* I

SONARRECEIVER -SCANNER

VOLTAGEREGULATOR

PR OGRAMMER-I RECOROER*

AFAMPLIFIER

R- SK -4

TRR

POWERPANEL

OATA OISTRIBUTIONPANEL

Brq REPEATER (081Brq REPEATER (CIC)T TSTO GYRO REPEATERTO SYNCHRO AMPLIFIER

TO OATA OISTRIBUTIONPANEL

TO PROGRAMMER-'RECORDER *

_I TRANSMIT BEAM'CONTROL *

41. 11

AZIMUTH ANORANGE INOICATOR

SPEAKERLOUD

TO T.C.O.CONTROLREPEATER (0 B)

1R -SK -2

- VOLTAGEREGPUOLWATERING

TRANSFORMER--I TRAINER TRANSFER

SWITCHCONTROL-INOICATOR

I PROGRAMMER-RECOROEH *

- (CIC) REPEATER- TO TRANSMIT BEAM CONTROL *

TO RANGE RECORDER-DATA OISTRIBUTION PANELcl LOUD

I

SPEAKERGAN

SONARTRANSOUCER

(HULL MOUNTEO TYPE)

TARGET SIGNALSIMULATOR CONTROL

NOTE:* SEE FIG. 8-2

Figure 8-1.Sonar Set AN/SQS-31 system.

: .0SONAR TEST SET

51.52(120C)

Available modes of operation are (1) listening 15,000 and 30,000 yards, (3) omnidirectionalfor echoes without transmitting (passive listen- transmission and (4) rotating directional trans-ing), (2) echo ranging at 1000, 2500, 5000, 10,000, mission (RDT).

137


When the equipment is set for passivelistening, the scope picture is a continuouslyexpanding circular sweep using the outer two-thirds of the PPI. The sweep recycles atthe same rate as the 5,000 yard scale. Signalsfrom an underwater noise source appear onthe screen as a narrow radial line or a wedgeof light. Bisecting the wedge with the cursorgives the bearing of the noise source. Rangecannot be determined because the noise sourceis not returning an echo.

In the echo ranging mode of operation,the cycle commences with the cursor appearingon the PPI scope at the instant a transmittedpulse is leaving the transducer. After thepulse is transmitted, the cursor disappearsfrom the scope, and an electron beam spiralsout from the center of the screen in an everenlarging circle at a rate proportional to one-half the speed of sound in sea water. Sweepof the electron beam is synchronized withthe rotation of the video scanning switch insuch a way that a returning echo brightensthe scope at a spot corresponding to the rangeand bearing of the object that produced theecho. Because the system is alert in alldirections and echo indications remain fora short time on the screen, the scope becomesa map of all echo-producing objects in thevicinity of the ship. After each scan period,the circular sweep fades out (or blanks), thetransmitter is energized with a new pulse ofenergy, the cursor reappears, and a new cyclebegins.

When operating in the rotating directionaltransmission (RDT) mode of operation, thetotal power available for omnidirectional trans-mission will be concentrated into a directionaltransmission beam that covers a narrow sectorat any given instant. This beam is thencaused to rotate a maximum of 360° in azimutharound the ship. Coverage is limited to amaximum of 300° and a minimum of 30°,selectable by the operator. In normaloperationfor search, the transmit sector width is 300°oriented about the ship's bow. The benefitsattained from RDT are greater power oftransmission and improved ranges.

The AN/SQS-29 to -32 series have a testset and control unit as a part of the system. Thetest set and its control unit provide facilitiesfor testing and calibrating the sonar receivingsystem.

These sonar sets, along with later sonars,may utilize Acoustic Short Pulse Echo

Classification Technique (ASPECT) equipment,giving a short burst of transmissions in asteered beam for greater accuracy in classifyingsonar contacts.

When ASPECT equipment is installed (fig.8-2) a transmit-beam control and a program-mer-recorder are added to the sonar equipment.The transmit-beam control has a steered beamtransmit scanner for short pulse operation. Theprogrammer-recorder controls transmissionand reception periods and receives the returningshort pulse-echoes, printing them on a recorderchart. Programming eliminates the necessityof continual changes as the range increases ordecreases. Since the sonar scope is blankedduring ASPECT operation, this gives the highestinformation rate while minimizing the probabilityof losing the target echo due to changes in range.

A few of the AN/SQS-29 to -32 series arefurther modified to permit use of the AN/SQS-10variable depth sonar (discussed later in thischapter).

When the AN/SQS-29 to -32 series receivesthe MARK (Maintainability And Reliability Kit)modification, the sets will become the AN/SQS-39, -40, -41, and -42 series sonars.The MARK program is a combined effort toextend the usable life of the sonar sets andimprove their operation and maintainability.

138


The AN/SQS-23( ) sonar detecting-rangingset i' a scanning type of search and attacksonar equipment which uses some of thedesirable features of the AN/SQS-29 to -32series of sonars. Besides passive listening,as with all sonars, it will echo range at anyone of six range scales; 1000, 2500, 5000,10,000, 20,000 and 40,000 yards with a 5 kHzoperating frequency and pulse lengths of 2(later models 5), 30, or 120 milliseconds.

A directional sonic beam rotates aroundthe transducer to form the echo ranging trans-missions. The transducer is designed sothat it can be excited without damage atmoderately high-power levels. The trans-mission frequency of the equipment, combinedwith rotating directional transmission (RDT),makes this set effective for longer range targetdetection than previous sonars.

Features incorporated into the AN/SQS-23( )include: (1) a means of lowering or raisingthe normal operating frequency a slight amountto minimize interference during multiship


VDS VOLTAGEREGULATING

POWER TRANS.

(VDS) CONTROL- (VDS) SON ARINDICATOR RECEIVER-SCANNER

(VDS)AF AMPLIFIER

SPEAKER .4--

PROGRAMMERCONTROL-

( FIG. 8-1)

Imo! d

DATADISTRIBUTIONPANEL( GYRO)

VDS VOLTAGEREGULATOR

INTERCONNECTINGBOX

(VDS) SIGNALDATA CONVERTER INTERCONNECTING

BOX (FIG.8-I

TRANSMITTERPOWER AMPLIFIERS IC

(FIG. 8-1)

CONTROL- PROGR AM MER1(FIG. 8-1 )

RECEIVER SCANNER(FIG. 8-1)

TRR

AF AMPLIFIER((FIG.8 -I) I

SIGNAL DATA ICONVERTER(FIG.8 -I)

SHIP'S POWER PANEL

CONTROL INDICATOR(FIG. 8-1)

CONVERTER(FIG.8-1)

SIGNAL DATA

UNDERWATER1 1 LOG

CONTROLINDICATOR(FIG.8-1)

PROGRAMMER-RECORDER TRANSMIT BEAMCONTROL

VDS SONARTRANSDUCER

Figure 8-2.ASPECT system and variable depth sonar AN/SQA-10.

139

/413

120.92


operations; (2) a beam depression control thatpermits a downward tilt of the transmittingand receiving beams for use in maintainingcontact with close targets; (3) a built-in testset for use in evaluating the overall performanceof the system; and (4) a unit for insertingsynthetic and maneuverable target signals intothe receiving circuits to provide for operatortraining.

Special programs have been developed forlater models of the AN/SQS-23( ) sonar sets.These include TRAM (Test Reliability AndMaintainability), and PAIR (Performance AndIntegration Retrofit). When the equipmenthas either the TRAM or PAIR modification,the Performance Monitoring Equipment (PME)is an integral part of the sonar system. Thiseliminates the necessity of having to openvarious receiving units to obtain a test pointfor metering and monitoring circuits that mustbe checked and adjusted for peak operation.The PME may also be used to record andreproduce taped signals for the indicator scopeand loudspeakers for training in tactical situa-tions.

The Test Reliability And Maintainability(TRAM) improves the test, reliability. and easeof maintenance of the sonar sets. This isaccomplished by modifying the transmittingsystem.

The Performance And Integration Retrofit(PAIR) will improve total system performanceby replacing the entire receiver indicator group.

When these special programs have beencompletely installed in the present AN/SQS-23it is scheduled to be designated the AN/SQQ-23integrated sonar system.


The AN/SQS-26( ) sonar is a more recentlydeveloped advanced search track and attacksonar that represents a radically improvedapproach in concept and in application to thepresent-day problems of submarine detection.Detection features and operational flexibilityof this equipment permit long-range coverageindependent of the depth and speed of thetarget.

The 5. basic modes of operation for theAN/SQS-26( ) are: (1) omnidirectional trans-mission (ODT); (2) rotating directional trans-mission (RDT); (3) convergence zone (CZ),(4) bottom bounce, and passive detection.

VARIABLE DEPTH SONARSET AN/SQA-10

Essentially, the variable depth sonar (VDS)is a conventional sonar that is modified totransmit and receive siglials through a trans-ducer contained in a towed vehicle (fig. 8-3).By means of a crane type hoist and a towcable, the vehicle is lowered below the inte rfer-ring thermal layers and then towed behind theship. Thus, the effect of the surface thermallayers on the sonar signals is minimized.

At present, the most widely used variabledepth sonar is the AN/SQA-10 Sonar Set.This set is used extensively with the AN/SQS-29to -32 sonar series and sometimes with SonarSet AN/SQS-23( ).

With the VDS modification, transmission andreception are available through either of twotransducers, one hull mounted and the other avariable depth transducer. Either omnidirec-tional or RDT transmission, as selected by theoperator, is available through each transducerin VDS. The towed or variable depth trans-ducer permits transmission and reception at aselected depth below the surface of the water toachieve optimum sonar performance, and repo-sitioning of the transducer as oceanographic con-ditions and tactical situations change. The VDSsystem (fig. 8-2) may incorporate its own re-ceiving and display system, or use the normallyinstalled equipment. In the latter case the op-erator selects the transducer to be used bymeans of a selector (Hull/VDS) switch.

140

Nv

MINE-HUNTING SONAR

Mine hunting includes all measures ofaccurately detecting, locating, identifying, andclearing mines INDIVIDUALLY. The clearancemay be accomplished by explosive destruction,by rendering safe, or by sweeping. The followingare two mine-hunting equipments which areused for detecting and locating mines.

Mine-Detection Set AN/SQQ-14

The AN/SQQ-14 (fig. 8-4) is a dual-purposesonar, which can be installed either as a hull-mounted sonar or operated as a variable-depthsonar. When operating as a VDS system,a towed body is used to house the transducersmaking it possible to operate at various depths.The high detection probability of the set isaccomplished by a wide scanned field of viewand a high resolution in both range and azimuth.


REMOTE

SONAR DATA

_

Figure 8-3.Towed vehicle for VDS (in suspension).

SONAR DATA

TRANSMITTER TESTAND CALIBRATE

SIGNALS

SHIP'S HEADINGFROM SHIP'S\ GYRO

SONARTRANSMISSIONSIGNALS

TILT DRIVE

INDIC ATOR,SONAR DATAHOIST, CH AIN SONAR

BEARING DRIVERECEIVER IF VIDEO SIGNALSHOIST UNIT CONTROL

IM

PORTABLE4t tiTEST

4PROBE T±3_SIGNAL

TESTCLASSIFYDISPLAYTIMINGSYNC

CONSOLE,SONAR

(CLASSIFY)

111

CONSOLE,SONAR

(SEARCH)

TRANSMITTER PULSES

SHIP'S4POWER

TRANSMITTERGATES

a.-0--CLASSIFY IPA AND BOTTOM DEPTH PULSES

SIGNALTEST

PORTABLE

TEST PROBE

TRANSM TTERSONAR

DEPTH

TRANSDUCER ,SONAR

CALIBRATEDSONAR CWSIGNAL

PROBE

XMITPULSES SCANNER

PULSES

51.63

BRG TILTDRIVE

CONTROL INDICATOR(DEPTH AND TEST)

CHAINCOVER

Figure 8-4.Mine-Detection Set AN/SQQ-14 system.

141

/X5

SWITCHASSEMBLY

SEA CHEST

TOWING EYE

TOWED BODYGROUP

WEIGHT:3000 LBS.

120.93


After detecting an object, the sonar'sclassification mode allows a trained operatorto quickly distinguish whether the object isminelike, or non-minelike bottom clutter suchas sunken oil drums, foot lockers, or anchors.The two consoles permit one operator to searchand the other to classify mines simultaneously.

Mine-Detection Set AN/UQS-1( )

The AN/UQS-1( ) sonar (not shown) employstwo transducers (transmitting and receiving)enclosed within a single housing. The trans-mitting (projecting) transducer uses the electro-strictive process to transmit a sonic beaminto the water that covers an arc 60° inazimuth and 10° vertical. Echoes reflectedfrom underwater objects are received by thereceiving transducer, converted into anelectrical signal, and applied to the PPI scope,showing an indication of range and bearingof the object.

Either manual or automatic searching isavailable. In manual operation, the transducersare caused to rotate as a bearing handwheelis rotated, searching through 360° in azimuthat selectable ranges of 200, 500, and 1000yards. When operating automatically, thetransducers may be caused to rotate through360° in azimuth, to search all around the ship,or to rotate back and forth through an arc90° in azimuth, searching from 315 relativeto 045 relative ahead of the ship. (A fieldchange to the equipmert provides for anautomatic sweep of 180° ahead of the ship.)For automatic search, the equipment can beset to search in ranges of 200, 500, or 1000yards. Whether searching manually or auto-matically, the operating angle of the transducersis controlled manually by a handwheel. Thetransducers may be tilted to cover from plus5° to minus 50° in depression. The angleof tilt can be observed on a depression indicatordial, which shows the angle of depression ofthe sound beam.

The scan pattern appears on the face ofthe scope as a 20° triangular sector with thevertex of the sector at the center. Targetsare indicated on the scope as a bright spotat the correct range and bearing of each target.

Mine Detection Range Set AN/PQS-1C

The AN/PQS-1C (fig. 8-5) is a portablehand-held sonar set used by SCUBA divers

during diving operations. It is incased ina waterproof hemispherical housing. A compassis located on top of the housing which canbe illuminated by a switch to provide thediver with an indication of the location ofthe detected underwater objects.

The AN/PQS-1C has two modes of operation.The search mode and the passive-listening mode.The search mode transmits an ultrasonic wavewhich sweeps through a 30 kHz bandwidthwithin the limits of a 50 to 90 kilohertzfrequency range. A transducer and reflectordirects the transmitted ultrasonic waves intoa narrow beam to provide precise angularsensing of the target location. The returningultrasonic echo is combined with a sampleof the transmitted signal, producing a differencein frequency proportional to the distance fromthe target. The lower the tone of this audio-frequency, the closer the operator is to thereflecting object. Three angle scales (20, 60,and 120 yards) are provided. The receivercompensates for variations in echo signalstrength and delivers 100 milliwatts of powerto the head set within the audiofrequency rangeof 250 to 2500 hertz.

During search operations, SCUBA diverswill set the range switch to a range com-mensurate with the depth of the water andsubmerge to the desired depth while holdingthe equipment so an echo is received fromthe bottom. The tone thus produced becomeslower in pitch as the bottom is approached.The range switch (fig. 8-5) enables the diverto search in a circular area having a radiusof 120 yards slowly scanning the target areawith The sonar beam and listening for a short-duration echo tone in the headset as the beamsweeps past an echo producing object. Hecontinues moving toward the object until theaudio tone in the headset is at a low pitch.The selector switch is then set on the 60yard range position, and the audio tone willimmediately increase to twice the pitch onthe 120 yard range. This allows the operatorto continue to close-in on the target, whilelistening for change in pitch. He continuesmoving toward the target until the audio toneis again at low pitch. The same procedureis continued at the 20 yard range until theexact object is located. If t1.2 target is amine, procedures can be initiated for itsdestruction.

In the passive-listening mode, the equip-ment can be used to locate marker beacons

142

i4


COMPASS

COMPASS

HEADSETCOMPASS LIGHT

PUSH BUTTON

PASSIVE-LISTENINGCONTROL

RANGESWITCHCONTROL

TRANSDUCER

A. FRONT VIEW


GUIDEHANDLE

CATCH ANDSPRING LOCK

HEADSET PLUG-IN HEADSET PLUG-IN

PRESSURE RELEASE SCREW

B. REAR VIEW

Figure 8-5.Mine-Detection Range Set AN/PQS-IC.

operating in the 30 kHz to 40 kHz frequencyrange.

FATHOMETERS

Fathometer equipments transmit accousticalpulses vertically downward and echo pulsesare reflected back to the fathometer fromocean floor or from intervening objects. Theinterval of time required between transmissionand reception is converted into a depth indicationon a recorder chart or cathode ray tube (CRT)indicator. The fathometer is used primarilyfor navigation purposes. It also serves asan aid in gathering depth information foroceanographic topography, and is occasionallyused as a sonar contact classification aid.The two fathometers used chiefly by the fleetin depth sounding for navigational purposesare the AN/UQN-1( ) and AN/UQN-4.

Depth-Sounding Sonar AN/UQN-1( )

The AN/UQN-1( ) fathometer and its trans-ducer are shown figure 8-6. This fathometer

143

120.94

is a compact unit, capable of giving reasonablyaccurate readings at a wide range of depth- -from about 5 feet to 6000 fathoms. It usesthe electrical stylus and sensitized paper methodof recording depths. For shallow depths,it has a visual scope presentation.

Three recorder chart ranges are providedon the AN/UQN-1( ). They are 0 to 600feet, 0 to 600 fathoms, and 0 to 6000 fathoms.In addition to recorder chart indications, two7isual indicator ranges are available: 0 to 100:'Pet; and 0 to 100 fathoms. The equipmentmay be keyed manually or automatically.

When the fathometer is operating in anyof the three recorder chart scales, a stylusstarts down the recorder chart simultaneouslywith the transmission pulse. The stylus movesat a constant velocity and marks the papertwiceonce at the top of the chart when thepulse is transmitted, and again on the depthindication when the echo returns. A depthrecording made by a fathometer of this typeis seen in figure 8-7. The recording illustratedwas made from a ship sailing over a sea

/4 7



62.9Figure 8-6.Depth-sounding Sonar

AN/UQN-1( ).

whose depth was decreasing steadily. Thefirst part of the trace was recorded on the6000-fathom scale. Inasmuch as the papermoves from right to left, you can see, inthe section of the paper shown, that the depthdecreased from 4000 to 600 fathoms. (Laterdepth information is to the right of the paper.)When depth was about 600 fathoms, the scalewas shifted to the 600-fathom setting. Becausethe depth decreased still further, the scalewas shifted to the 600-foot setting when adepth of about 100 fathoms was recorded.

Visual indication is supplied by a circularsweep on the face of a cathode ray tube. Trans-mitted pulse and returning echo deflect thesweep trace radially. The visual indicator,pointing to a depth of 82 (feet or fathoms,depending upon the scale setting), is shownin figure 8-8.

Depth-Sounding SonarA N /UQN -4

Sonar Sounding Set AN/UQN-4 is designedto indicate water depths ranging from 4 feetto 6000 fathoms, transitorily on a digitalnumeric display and permanently on a stripchart recorder. Digital numeric depth indi-cation is achieved by counting the number ofpulses provided by a clock frequency duringthe interval between the transmission of atransducer-generated sound pulse into the waterand the reception of its echo from the seabed. This count, after processing by digitalcountdown circuits, is indicated as feet orfathoms of depth on the numeric display.

To prevent false bottom depth indicationby echoes returning from fish shoals, planktonlayers or other anomalies, a "Range Gate"circuit insures that only signals received fromwithin the confines of the gated range shallbe effective at the digital readout. A permanentrecord is recorded on chart paper (similarto that shown in fig. 8-7) by a strip chartrecorder.

The AN/UQN-4 has the capability of trans-mitting numeric depth information to remoteindicators or sonar computers which can belocated up to 1000 feet from the fathometer.

144

SONAR ACCESSORIES

Supplementing the basic sonar system area number of equipments that either extendthe capability of the system or facilitate itsuse. Some of this supplementary or accessoryequipment forms an integral part of the overallsonar system, whereas other equipment inthis category is completely isolated from thesystem.

AZIMUTH-RANGE INDICATORS

A complete azimuth search sonar installationincludes one or two remote units called azimuth-range indicators. These units are remotevideo repeaters of the scope presentation atthe sonar control indicator. They providean indication of target bearing and range, andthey have provisions for monitoring the audioresponse from targets.

The PPI (scope) display modes of operation(echo ranging or listening) may be presentedin either of two ways: the ship center display


1, .

-TRANSMITTED PULSE TRACES

-TRACES MADE ON6000 FATHOM zi°

SCALE300

403

1161

,app

TRACES MADE ON TRACES MADE ON600 FATHOM 1b0 600 FOOT uo

SALE ; SCALE

- siro

0111111 010

0 ow //,i the end of the bearing cursor is on target.0 iNN

,,,, The SCD (fig. 8-9) utilizes a circular sweep., starting at or near the center of the screen

..

.:..-

.:-..

I

7:

which indicates the position of own ship. Variousunderwater objects are represented by the brightspots (pips) that appear on the screen. The

baba 6CO3IMAM a IMP WO

Figure 8-7.Fathometer depth recording.

U0

62.10

(SCD), whereas the ship is depicted in thecenter of the scope display; or the targetcenter display (TCD) in which the target isrepresented in the center of the display whenever

SCD is the normal operating mode becauseit allows the operator to observe many targetsaround the ship at one time.

'till Ito $ The TCD (fig. 8-10) uses an expanded sweepwith the target at the center of the scope.The sweep is enlarged to 2 1 / 2 times itsnormal size and is offset from the centeron a reciprocal bearing from the cursor.This mode is used only as an aid to classification.

One common type of azimuth-range indicator,71.57 the IP-286/SQ, is illustrated in figure 8-11.

Figure 8-8.Visual depth indicator. This particular unit is used with installations

145


120.43Figure 8-9.SCD sonar presentation.

DISPLAYOFFSET

ANDMAGNIFIED

000'

BEARINGCURSOR \A.

TARGET

51.55(120C)Figure 8-10.TCD sonar presentation.

of the AN/SQS-29 to -32 series of sonars(discussed earlier). A similar unit, designatedIP-481/SQ (not shown) is used with the AN/SQS-23 sonar equipment.

146

EARPHONEJACK

INTENSITYCONTROL

SIGNAL INTENSITYCONTROL

FOCUSCONTROL

SPEAKER VOLUMECONTROL

35.24Figure 8-11.Azimuth-range indicator

IP-286/SQ.

Controls on the front panel of the azimuth-range indicator affect the audio and videoresponse of the remote unit, but do not affectoperation of the sonar console. Three ofthe four controls are for adjusting the videodisplay. The fourth, labeled SPEAKER VOLUMECONTROL, is used to adjust the audio outputlevel.

Target bearing is read from an azimuthring surrounding the video presentation. Targetrange is indicated on two dials that are visiblethrough a window opening. Audio responseis heard from either an external speaker unitor headphones, as desired.

TARGET COURSE PROJECTOR

The target course projector (fig. 8-12) hasa servosystem, transistor amplifier, and opticalsystem. This unit is a sonar accessory whichresponds to target course orders from firecontrol, and projects a cursor image in theform of a red line on the screen of the rangeand azimuth indicator. The unit is located4 to 5 feet from the CRT screen and mountedin such a position on the overhead that personsviewing the screen do not obstruct the lightbeam.

RECORDER - REPRODUCER

A tape recorder-reproducer is employedwith most sonar installations to record audiblesonar information of actual ASW operations.


.

t

TARGET COURSEPROJECTOR

31

XS

I

AZIMUTH AND RANGEINDICATOR IP481/SQ

Figure 8-12. Target course projector, relationship to range and azimuth indicator.15.99

Information thus obtained is utilized for post- The AN/UNQ-7( ) recorder-reproducer setanalysis of ASW actions and for the aural (fig. 8-13) is a two-track recorder and repro-training of sonar operators in echo recogni- ducer that uses magnetic tape to record itstion. information. It stores for playback (immediately

147


0 ;AO'sVW'74;7 riernar

41,..".""

1 411V 41.

7.54Figure 8-13.Tape recorder AN/UNQ-7( )

or indefinitely) the sounds it "hears" withinthe limits of the audible spectrum. Two channels(A and B) are utilized. Voice informationfrom the vicinity of the sonar operator's stationis fed to channel A. Channel B track normallyis fed underwater sound information directlyfrom the sonar equipment. Both tracks canbe (usually are) recorded simultaneously,although either one may be recorded separately.In addition, the tape recorder allows simulta-neous recording and reproducing of sounds.This feature permits monitoring what is beingrecorded as it is recorded.

When a recording is played back, bothtracks can be heard at the same time, andboth tracks can be controlled in volume orcan be cut out entirely. In short, the AN/UNQ-7( ) tape recorder-reproducer acts as acombination of two tape recorders, coupledtogether, to allow superimposing upon eachother, two audio information sources.

The top half of the tape recorder-reproducer,as seen in figure 8-13, is the actual recorderand reproducer. The lower portion is the

amplifier section. It includes controls andindicators that directly affect the recordingand playback of tapes. The recording controlsare to the left of the amplifier section.Playback controls are at the right of theamplifier section. Both channels have separatecontrols for recording and reproducing.

BATHYTHERMOGRAPH

Pressure, salinity, and temperature affectsound travel through water. Increases inpressure speed up the velocity of sound, makingthe speed of sound higher at extreme depthswhere pressure is greater than on the surface.An increase in salinity also has a tendencyto increase the velocity of sound in water.The effects of pressure and salinity are notas great, however, as those caused by changesin temperature.

Temperature, then, is the most importantconsideration to contend with in calculatingvariations in the speed of sound in water.Information obtained about the ocean tempera-ture, at a given depth and time, can be usedto predict what will happen to the transmittedsound beam as it travels through the water.

The bathythermograph, commonly called theBT, is an instrument for obtaining a permanent,graphical record of water temperature (indegrees Fahrenheit) against depth (feet) as itdrops into the ocean.

Two types of bathythermographs are beingused. The expendable and the mechanical.The expendable BTs record the readingsautomatically as the probe falls to the oceandepths. This is in contrast to the oldermechanical BT system that requires retrievingthe BT in order to obtain data recorded ona metallic coated glass slide.

MECHANICAL BATHYTHERMOGRAPH

Mechanical bathythermographs are designedfor use in measuring three different depthranges. In general, a No. 1 designationmeans it is a shallow type, No. 2 meansit is a medium type, and No. 3 indicatesthat it is a deep type BT. Table 8-2 liststhe various BTs in use and gives their designdepth.

The mechanical BT consists of temperatureand pressure elements (fig. 8-14). Thetemperature element consists of about 45 to 50feet of fine copper tubing filled with xylene.


Table 8-2.BT Series Designations.

Series No. NameMaximum Towing Speeds

Maximum depth Nose Sleeve

Without WithOC - ls0C-1A/S0C-1B/S0C-1C/S

OC-2/SOC -2A /S0C-2B/S0C-2C/S

OC-3/SOC -3A /S0C-3B/S0C-3C/S

Shallow

Medium

Deep

200 feet

450 feet

900 feet

15 knots

10 knots

3 knots

22 knots

13 knots

6 knots

TEMPERATURE ELEMENT

STYLUSARM

PRESSURE ELEMENT

SMOKED GLASS

SLIDE

gene

Mr 1,10 I 114061

BELLOWS

XYLENE FILLEDTUBING

BOURDONTUBE

STYLUSLIFTER

nPISTON SPRING

HELICAL

HEAD

71.73Figure 8-14.Mechanical Bathythermograph temperature and pressure elements.

The tubing is wound around inside the tail or contracts with the changing water tern-fins of the BT, and comes into direct contact perature, the pressure inside the tubingwith the sea water. As the xylene expands increases or decreases. This temperature


change is transmitted to a Bourdon tube, ahollow brass coil spring, which carries astylus at its free end. The movements ofthe Bourdon, as it expands or contracts withchanges of temperature, are recorded by thestylus on a metallic-coated glass slide. Thetemperature range is from 28° to 90° F.

The slide is held rigidly on the end of a coilspring enclosed in a copper bellows. Water pres-sure, which increases in proportion to waterdepth, compresses the bellows as the BT sinks.

The dotted line drawings in the lowerportion of figure 8-14 illustrate the actionof the stylus moving left on the slide witha decrease in temperature and the bellowsbeing compressed to the right (arrow) asdepth increases. Increase in depth pulls theslide toward the nose of the BT, at rightangles to the direction in which the stylusmoves to record temperature. When the BTis raised toward the surface, the spring expandsthe bellows to its original shape. Thus, the tracescratched on the plated surface of the slide is acombined record of temperature and pressure,the pressure being proportionate to depth.

The mechanical type bathythermograph isbeing replaced by the expendable bathythermo-graph as they become available.

EXPENDABLE BATHYTHERMOGRAPHAN/SSQ-56

The expendable bathythermograph AN/SSQ-56 (fig. 8-15) consists of an expendableprobe, a launcher, and a recorder. The expend-able probe contains a thermistor connected to aspool of fine wire. The wire is dereeled as theprobe drops vertically through the water. Theother end of the wire is wound on a second spoolmounted within a probe canister aboard ship. Asthe ship moves ahead, this wire is also dereeled.The dual spooling technique allows the probe tofree-fall from the exact point of sea-surfaceentry without being affected by the movingship or sea state.

The nose of the probe is weighted andthe entire unit is spin-stabilized to assurea known rate of descent upon launching.Changes in resistance of the thermistor dueto temperature changes in the water aretransmitted by the trailing wire to the ship-board recorder. Since the rate of descentof the probe is known, depth can be read directlyfrom the vertical scale on the recorder. Afterthe probe passes 1500 feet, its full scope of wire

150

Canister Loading Breisch

Canister wire Spool

Launcher RecordrCable (4-wireshielded)

Optional

LAUNCHER

Stanchion

TerminalBoard

Alternati no-Current PowerCable (3-wire)

RECORDER

Depth/TemperotureChart

Woes, Level

Wire Spool

Thermistor

EXPENDABLE PROBE

71.126Figure 8-15.Expendable Bathythermograph

Set AN/SSQ-56.

will be exhausted and the probe sinks to thebottom of the sea.

The chart type recorder is programmedto convert time and thermistor resistanceinto depth and temperature in units of feetand degrees Fahrenheit, or meters and degreesCentigrade. A continuous temperature /depthprofile is traced on a 6-inch portion of the chartas the expendable probe descends.

The recorder has a completely automaticprogram, which is initiated by inserting a probeand closing the breech of the probe launchingdevice. This procedure completes a circuitbetween the probe and the recorder, lockingthe servo in the center scale position anddriving the chart for a few seconds. The chartdrive then stops. It starts again when theprobe is released and enters the watercompleting a seawater trigger circuit to beginthe measurement cycle. After 90 seconds, thetemperature depth profile has been recordedand the chart drive stops, indicating completionof the cycle. The launcher is then ready forreloading.

CHAPTER 9

ELECTRONIC NAVIGATIONAL AIDS

Basically, electronic navigation is a form ofpiloting. Piloting is that branch of navigation inwhich a ship's position is obtained by referringto visible objects on the earth whose locationsare known. This reference usually consistsof bearing and distance of a single object,cross bearings on two or more objects, ortwo bearings on the same objects with aninterval between them.

Position in electronic navigation is deter-mined in practically the same way that it isin piloting. There is one important difference,however. The objects by which the ship' sposition is determined need not be visible fromthe ship. Instead, their bearings (and in mostinstances their ranges) are obtained by elec-tronic meansusually radio.

The advantages of piloting by radio areobvious. A ship's position may be fixed elec-tronically in fog or thick weather that other-wise would make it impossible to obtain visualbearings. Moreover, it may be determinedfrom stations located far beyond the rangeof even clear-weather visibility.

This chapter will deal with electronic navi-gation by Loran, Shoran, Omega, SINS, Satel-lite, and Tacan.

LORAN NAVIGATION SYSTEM

The long-range navigation (loran) systemprovides a means of obtaining accurate navi-gational fixes from pulsed radio signals radiatedby shore-based transmitters. Depending onthe mode of loran operation and the time ofday or night, fixes are possible at distancesup to 3000 nautical miles from the transmittingstations.

The loran system comprises two subsystems,or modes of operation, called loran A andloran C. Because loran A is the basic modeof operation, it is used as the vehicle for

151

explaining the loran principle of operation.Loran C is a refinement of loran A, differingfrom the basic mode mainly in operating fre-quency and coding of signals employed. Ithas a much greater distance range thanloran-A.

LORAN PRINCIPLE

The principle of loran is illustrated infigure 9-1. If part A, stations A and B arepulsed simultaneously, the two pulses arrive atany point on the center line at the same time.This is evident from the geometry of thefigure; and an observer, with the proper receiv-ing equipment, could tell if he was on thisline.

Suppose, however, that an observer is locatedcloser to station A than to station B. Thenthe pulse from station A will arrive at hislocation before the pulse from station B. Assumethat the time difference is 800 As, as shownin part B. There are many points at which thereceiving equipment will indicate a time dif-ference of 800ms; these points lie on a hyperbola.Connecting the points where the time differenceis the same, forms a line of constant time dif-ference, or hyperbolic line of position. This line(solid curved line) forms the LEFT BRANCH ofthe hyperbola. It is concave toward station A.

If the observer knows that he is closerto station A than station B and that the timedifference is 800 As, he still does not knowhis exact position on the hyperbolic line ofposition.

Assume now that the observer is nearerstation B than station A and that the timedifference between the arrival of the two pulsesis 800µs. The line of constant time differenceis then the right-hand branch of the hyperbola,and appears as the dotted curve in figure 9-1B.

(Stations A and B are the foci of the hyper-bola.) If the pulses from the transmitters areidentical, the observer has no way of telling


STATIONA

LEFT-HANDBRANCH

//

/

RIGHT-

/ BRANCH

STATION STATION9 A

STATION

Figure 9-1.Principle of loran simplified.

152

/54

12.34(120C)

Chapter 9ELECTRONIC NAVIGATIONAL AIDS

which pulse arrives first. He then cannotdetermine on which branch of the hyperbolahe is located. This difficulty is overcome, andat the same time the measurement made by theobserver is simplified, by delaying the pulsingof one of the transmitters by an amount thatis more than one-half the pulse-recurrence in-terval from the other station. For example, theinterval between a pulse from A and the nextpulse from B is always made greater than theinterval between the B pulse and the next Apulse. Thus, the navigator can tell that the pulsefollowed by the longer interval is always fromstation A.

From the foregoing explanation it followsthat many lines of position may be obtained. Byselecting several time differences for a givenpair of stations, the result is a family ofhyperbolas like those shown in figure 9-2A.

b

2000IIILSE LINE EXTENSION

a

5

2000

A

USE LINE EXTENSION

In this figure the pulses from both transmittersare identical and no time delay is introducedas indicated by zero on the center line.

In actual practice, one station of a loranpair (fig. 9-2B) is designated the master sta-tion. It establishes the Pulse Repetition Rate(PRR). The second, or slave station, receivesthe pulses of the master station and transmitsits own pulses delayed in time but in syn-chronism with the master pulses. The timedelay between the transmission of a pulse fromthe master station and the arrival of this pulseat the slave station depends chiefly upon theDISTANCE between the stations. This delay iscaused by transit time.

After the pulse arrives at the slave sta-tion, there is a time delay of one-half thepulse-repetition period. This delay is nec-essary because of the two-trace method of

70.17Figure 9-2.Loran lines of position.

153


cathode-ray-tube presentation at the loran in-dicator.

In addition to these two delays, another delay,called the CODING DELAY, is added. Thesum of the three delays is called the ABSO-LUTE DELAY. The absolute delay is the timebetween the transmission of a pulse fromthe master station and the transmission of apulse from the slave station. The absolutedelay in figure 9-2B, is 3000 ps, as indicatedon the center line.

The PRR is different for different pairsof stations to enable the operator to identifythe pair to which the receiver is tuned. Thereare four loran channels, numbered 1 through 4,corresponding to carrier frequencies of 1950,1850, 1900, and 1750 kHz, respectively. TheBASIC PRR is either 25 Hz (the LOW, orL, rate) or 33-1/3 Hz (the HIGH, or H, rate).A third basic recurrence rate of 20 Hz (theSPECIAL, or S, rate) is not in operationaluse, but is provided in new equipment to allowfor expansion of the loran system.

The basic pulse recurrence rates are sub-divided into SPECIFIC PRR. The specific lowPRR is from 0 through 7, corresponding to25 through 25-7/16 pulses per second in stepsof 1/16 of a pulse per second. The specifichigh PRR is from 0 through 7, correspondingto 33-1/3 through 34-1/9 pulses per secondin steps of 1/9 of a pulse per second.

To establish his position, the loran operatormust have the proper loran charts, as wellas the proper receiving equipment. A loranfix is the point of intersection of two linesof position. Two pairs of transmitting stations,or one master and two slave stations, areneeded to establish the lines of position neces-sary for the fix. One pair of stations act asfoci for one family of hyperbolas. The secondpair of stations act as foci for another familyof hyperbolas. As has been stated, a fixis the intersection of two hyperbolas, onefrom each family.

Figure 9-3 illustrates a fix is obtainedby using only one master i two slave stations.This is accomplished causing the masterstation to transmit -istinct sets of pulses.The double-pulsed ma, r station transmits oneset of pulses at the PRR of the pulse trans-mitted by the first slave station and the otherset of pulses at the PRR of the pulses fromthe second slave station.

Lines of position are identified by a letterand several numbers. The letter represents

154

the basic PRR-Low (L), high (H), or special(S). The first number represents the channel(1 through 4), or carrier frequency; the secondnumber denotes the specific PRR; and thelast number is the time difference in micro-seconds. For example, 2L 6-2500 indicateschannel 2, which is 1850 kHz; a low basicPRR of 25 Hz; a specific PRR of 6, corres-ponding to 25-6/16 Hz; and a time differenceof 2500 ps.

For loran C operation, a master and twoslave signals are transmitted on a carrierfrequency of 100 kHz. These signals aremultiple-group transmissions, identified asmaster or slave signals by the number of pulsestransmitted in each group. The master grouptransmission is comprised of nine phase-codedpulses. The pulses are separated from oneanother by either 1000 or 500 /As, except thatthe ninth pulse is separated from the eighthby approximately 600 Ps. The slave grouptransmission is comprised of eight pulses, eachseparated from the others by either 1000 or500 ps to conform to the master station trans-mission. Phase coding is a method of changingthe radiofrequency of each pulse relative tothe frequency of the carrier. The phase isvaried within each group of pulses in accordancewith a prescribed program.

Loran C operation has capabilities f or singleor double rate reception. Single rate receptionprovides maximum time difference readingsof 30,000 (H), 40,000 (L), and 50,000 (S) micro-seconds. Double rate reception extends thetime difference readings to 60,000 (SH), 80,000(SL), and 100,000 (SS) microseconds. Forsingle rate reception, basic repetition ratesare 16 2/3, 12 1/2, and 10 groups per second;for double rate reception, 33 1/3, 25, and 20groups per second.

The advantage of loran C over loran A isdue to the characteristics of the transmissionand the lower operating frequency. Greaterpower output results from using group pulsinginstead of single pulsing. The lower operatingfrequency permits greater distances with theavailable power output. Measurement of thephase relationship between the pulses and thecarrier contributes to accurate fixes at greaterdistances. In addition, a fix may be made inone operation without changing the selectedchannel, the basic repetition rate, or the specificrepetition rate.

The instrument used for measuring thesmall periods of time that elapse between the


5.

Figure 9-3.Obtaining a fix with one master and two slave stations.


arrival of signals from the loran transmittingstations is a combination radio receiver andvideo indicator. The receiver accepts the RFpulses, converts them to videopulses, and sendsthe video pulses to the indicator for displayon the face of a small cathode-ray tube.

The master and slave pulses appear on twohorizontal traces, as in figure 9-4. With the

MASTER OR "APULSE MEASURED. TIME

DIFFERENCE

109.22Figure 9-4.Traces on a loran indicator.

two signals aligned properly, the time differencebetween their reception is read from timingmarkers displayed on the scope or from revolu-tion type counters on the front panel of thereceiving set. Because the measuring processis quite lengthy and varies from equipment toequipment, it is not discussed in detail in thistext.

LORAN EQUIPMENTS

A loran set aboard ship is a receivingset or indicator that displays the pulses fromloran transmitting stations ashore. Earliermodels have a separate receiver and indicatorwhile later models have a receiver set witha built-in indicator.

Loran Receiving Set Model DAS-4

Perhaps the oldest loran receiving set stillinstalled aboard ships in the active fleet is themodel DAS-4 (fig. 9-5).

156

120.46Figure 9-5.Loran A Receiver DAS-4.

This set, consisting of a receiver unit andan indicator unit, is capable of receiving loranA signals only.

The receiver (left-hand unit in the illustra-tion) is a conventional superheterodyne receiverthat covers the frequency range 1700 to 2000kHz. It has no variable tuning. Instead, it ispreset to four different frequencies, correspond-ing to the four loran A channels. Channelsare selected by means of a switch located onthe front panel of the receiver.

The indicator unit contains the circuitrynecessary for measuring the difference in timeof arrival of the pulses from a pair of lorantransmitting stations. By manipulating thefront panel controls (in the manner prescribedin the operating instructions accompanying theequipment), the received pulses and the timingmarkers are seen on the face of the scope.Interpretation of the timing markers resultsin a time difference measurement that is correctto 1 ps.

Loran Receiving Set AN/SPN-7( )

The AN/SPN-7( ), (fig. 9-6) is anotherloran A receiving set. Like the DAS-4, thereceiver portion of this set is a crystal-control-led superheterodyne receiver that is presetto the four loran A frequencies. .The indicator

/6 0


RECEIVER-INDICATOR INTERCONNECTINGCABLE ANDCONNECTOR

TRUNNIONMOUNT

MOUNTINGADAPTER POWER SUPPLY

Figure 9-6.Loran A Receiver AN/SPN-7( ).

portion is an accurate timing device that meas-ures the time difference in arrival of thesignals from the loran transmitters.

The receiver-indicator accepts the loransignals from the transmitting stations andpresents the two signals on the scope. Whenthe two signals are matched properly, thetime difference in their arrival is indicateddirectly on a revolution type counter and adial. Thus, time measurements are simplified,and inaccuracies that could result from mis-interpretation of timing markers are eliminated.

Loran Receiving Sets AN/UPN-12( )and AN/UPN-15( )

Originally designed for loran A operationonly, the AN/UPN-12( ) receiving set wasmodified to accommodate both loran A andloran C signals. Modification is accomplishedby adding a small receiver-control unit and

157

16/

ANTENNA INPUTCONNECTOR

CABLE CONNECTOR

M!=1"--.1111110

ANTENNACOUPLER

120.47

associated components to the existingAN/UPN-12( ) set. When so modified, thenomenclature of the receiving set is changedfrom AN/UPN-12( ) to AN/UPN-15( ). TheAN/UPN-15( ) is shown in figure 9-7.

When functioning as a loran C receiver-indicator, the set utilizes the signals receivedby the receiver-control unit mounted atop themain chassis. This unit contains a 100 kHzradio receiver of the tuned radiofrequencytype. The controls that affect its operationas a loran C receiver are on the front panelof the unit.

With the equipment set for loran A operation,the 100 kHz receiver is isolated from the setand the four-channel superheterodyne receiverin the main chassis is used to receive theloran signals.

The indicator unit of the set displays eitherloran A or loran C signals. When the receivedpulses are aligned as prescribed for the particu-lar mode of operation, time difference readings


Figure 9-7.Loran C Receiver AN/UPN-15( ).

are taken from a counter. By taking a secondreading from a different set of loran stationsand referring to loran charts and tables thegeographic position of the ship is determined.

Loran Receiving Sets AN/SPN-31,-32,-38

Loran receivers of this series operate in theLoran C mode. We will discuss the AN/SPN-38(fig. 9-8) as a representative type of the series.The receiver displays precise long range navi-gation time-difference measurements or Loran

158

120.'

signals au. omatically and continuously to 0.C5psaccuracy.

The system provide:: visial and electricaloutputs which can be used tc operate computerand recc -der navigational equipments. A three-inch reco3.10.11ar display indicator is locatedin the upper right-hand corner of the receiver.Loran video and RF signals are displayed inboth slow and fast CRT sweeps. The CRTalso serves as a testing oscilloscope for diag-nos,tic mantenance uz the receiver. A signalproduces simulated output signals for periodic

Chapter 9 ELECTRONIC NAVIGATIONAL AIDS

eel

120.48(120C)Figure 9-8.Loran C Receiver AN/SPN-38.

performance checks and serves as test equip-ment for the receiver.

The AN/SPN-38 automatically searches outloran signals, locks on, and synchronizes withthe ground wave. The two time differencemeasurements between each slave signal andmaster signal are read out on nixie tube dis-plays from digital logic circuits.

OMEGA NAVIGATION SYSTEM

The Omega System is an outgrowth of theloran A and loran C systems. The system,presently being installed, will provide eightposition-fixing transmitting stations locatedaround the earth to accommodate land vehicles,aircraft, ships and submarines (at moderateantenna depths). The system has been madepossible by recently uncovered facts concerningthe propagation of very low - frequency radio sig-nals over substantial distances.

The Omega Navigation Receiver AN/SRN-12(fig. 9-9) is a single frequency, phase-lockedsuperheterodyne receiver with a whip antennaand coupler for the reception of Omega navi-gational signals. The receiver operates in theVLF (10 to 14 kHz) range to provide a positionreadout in hyperbolic coordinates.

The fundamental measurement performedby the receiver is the relative phase compari-sons (phase angles) of the VLF signals. Thenavigator can determine the line of positiongenerated by any convenient pair of stations

159

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.41 ,o1 . air

Figure 9-9.Omega ReceiverAN/SRN-12.

120.48

and then cross it with one or more linesderived from another pair or pairs of stations.He may make, readings on four or five linesof position, but usually will choose the twopairs that jointly give the greatest precisionat his particular location. After the selectionof the two pairs (a minimum of 3 transmitters)the operation of the receiver is automatic inthe tracking of these signals, until the operatormodifies his choice of pairs, or until he arrivesat his destination. The indication of positionlines is continuous and may be recorded forthe convenience of the navigator.

SHORAN

Shoran (short range navigation) was de-veloped during World War II to permit bombingthrough undercast. It provided such greataccuracy that it has since been further de-veloped for surveying. It usually operates atfrequencies between 230-310 MHz. Thus, itis limited to line-of-sight ranges. Shoranpermits accuracies up to about 50 feet fora fix.

The basic principle of Shoran is as follows.Signals from one's own ship or aircraft auto-matically trigger two fixed beacon transmitterslocated ashore at some known distance apart.The signals emitted by these transmittersare received and displayed on an indicatorscope aboard. The two distances in the formof pips on the scope are continually available

/63


permitting rapid determination of position. Whenmeasuring and plotting these two ranges ona chart, the point of intersection is the fix.Charts that show a number of concentric circlescentered upon each beacon permits approximatepositions to be plotted by inspection.

Shoran using a medium frequency of 1900kHz was developed for use aboard ship tocover distances of several hundred miles fromshore.

SHIPS INERTIAL NAVIGATION SYSTEM

Ships Inertial Navigation System (SINS) isa method of navigation by dead reckoning, whichmeasures speed and heading and uses thesemeasurements to compute position change froman initial position fix. This method is incontrast to the loran and omega system methodswhich fixed the ship's position by measuringposition relative to some known object.

The basic components of an inertial navi-gation system (fig. 9-10) are the accelerometers,gyroscopes, servosystems, and computers (notshown). An accelerometer is a device whichmeasures changes in speed or direction. Itsoutput is usually in the form of a voltageproportional to the acceleration to which itis subjected. A set of two accelerometers

X - ACCELEROMETER

Y -ACCELEROMETERPITCH SERVO MOTOR

PITCH AXISPITCH GIMBAL

AZIMUTHSERVO MOTOR

AZIMUTH AXIS

ROLL SERVO MOTOR

ROLL AXIS

ROLL GIMBAL

162.55Figure 9-10.Stable platform with

inertial components.

160

are mounted on a gyro-stabilized platformin order to keep them in a horizontal positiondespite changes in the ship's movements. Theaccelerometers are attached to the platform bymeans of an equatorial mount (gimbal) whosevertical axis is aligned parallel to the earth'spolar axis. This permits the N-S accelerometerto be aligned along a longitude meridian, whilethe E-W accelerometer is aligned along alatitude meridian.

A three-gyro-stabilized platform is main-tained in the horizontal position regardless ofthe pitch, roll, and yaw of the ship. Whenthe ship's heading changes, the gyro signalswill cause servosystem motors to operate tokeep the platform stabilized. High-performanceservosystems are needed to maintain the plat-form stabilized to the required accuracy.

The self-contain navigation system contin-uously computes latitude and longitude by ac-curately sensing the accelerations of the vehiclewith respect to the earth's surface. A computercapable of converting distance traveled intocorresponding changes in latitude and longitudeis needed.

The system is expensive and its accuracywill decrease with time. A good coverage ofthe inertial system is found in ET3&2, NavPers10195.

SATELLITE NAVIGATION SYSTEM

Satellite Navigation was thought feasibleafter observation of Russia's first artificialearth satellite, Sputnik I. Scientists listened tothe beep generated by Sputnik as it passedby and noted the Doppler-like shift in the re-ceived radio frequency signals. Doppler effectis an apparent change in a received frequencybecause of relative motion between the trans-mitter and receiver. If the distance betweenthe transmitter and receiver is decreasing, thereceived frequency is higher than that whichis actually transmitted; if the distance is in-creasing, the received frequency is lower thanthat transmitted. It was later demonstratedthat accurate measurement of this dopplershift pattern would permit the determinationof a satellite orbit. From this successfullyproved technique it was further reasoned that,working from a known satellite orbit, a listenercould determine his position on the surfaceof the earth from an observed doppler pattern.From this point followed the first successful


satellite launch in April 1960, and the U.S.Navy Navigation Satellite System became anall-weather, highly accurate, fully operationalnavigation aid, that enables navigators to obtainaccurate navigation fixes from the data collectedduring a single pass of an orbiting satellite.

NAVIGATION SYSTEM DESCRIPTION

The Navy navigation system (fig. 9-11),is a worldwide, all-weather system of highaccuracy which enables navigators to obtainfixes approximately every two hours, day andnight. It consists of four earth-orbiting satel-lites, four tracking stations, two injection sta-tions, the U. S. Naval Observatory, a computingcenter, and shipboard navigational equipment.

Satellites

Four satellites (only two shown in fig.9-12) are placed 45 latitudinal degrees apartin separate circular polar orbits longitudi-nally around the earth, at known altitudes.(The altitude of the satellites is between500 and 700 nautical miles.) The earth rotatesinside these satellite orbits. Each time thesatellite makes a pass over the earth (aboutevery 108 minutes) its orbital position seemsto have moved farther westward. This is dueto the rotation of the earth. Externally, thesatellite is octagonal in shape (fig. 9-13).It has four solar cell vanes which are shapedlike a windmill and used to generate DC elec-trical power. The satellite's directional anten-nas point earthward at all times since theyhave been stabilized in the earth's gravita-tional field.

Internally, the satellite is made up of anumber of all-transistorized systems. Theseinclude

1. A command receiver and identificationcode facility for ground station communications.

2. A telemetering system for transmittingmeasured results to receiver sets locatedon the earth.

3. A digital memory system for storingtwo types of information:

a. The fixed parameters for all datait transmits that doesn't change, such as thesynchronization and identification signals, andthe fixed parameters transmitted from ground

161

station to the satellite every twelve to six-teen hours giving information describing allfour of the satellite's nominal orbits.

b. The variable parameters transmittedfrom the satellite to the earth receivers everytwo minutes giving information describing thefine structure in the satellite's nominal orbits,thereby keeping its time and location up-dated.

4. Two harmonically related transmitters(one for a standby unit) for sending out twodifferent phase-modulated radiofrequencycarrier waves.

5. Dual frequency systems, one at 400 MHzand the other at 150 MHz, used to minimize theeffects of ionospheric refraction.

6. An ultrastable transformer oscillator formaking accurate doppler-shift measurements.(The transformer oscillator is an arrangementof transformers and switching transistors.)

7. A digital clock for transmitting precisetime information.

8. Battery power supplies for receiving,storing, and releasing electrical energy foroperating the electrical powered equipment.

Tracking Stations

Four tracking stations, spaced to monitorthe four polar circling navigational satellites,are located one in each of the States of Hawaii,California, Minnesota, and Maine. The purposei3 to determine accurately the present andfuture orbits of each satellite. These stationshaving radio receiving and data processingequipment, will digitize and send the orbitaland time information via control center tothe computing center.

Naval Observatory

The Naval Observatory controls satellitetransmission of the two-minute interval timeperiod to an accuracy of one-millisecond ofthe even integer of universal time (UT-2).It accomplishes this by receiving the digitalmemory signals from the satellite during eachpass and comparing them to the observatory' sdata processing equipment. The time andorbital information is sent to the control center.

Control Center

All satellite data is routed through thecontrol center which acts as a switching central

/66

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for monitoring data to and from the CentralComputer Center.

Central Computing Center

The Central Computing Center continuouslyaccepts data inputs on the satellites from thefour Tracking Stations and the Naval Observa-tory. Periodically, to obtain fixed orbital para-meters for a satellite, the Central ComputingCenter computes an orbit for each satellitethat best fits the doppler curves obtained fromall Tracking Stations. Then using the com-puted orbital shape, the central computingcenter extrapolates the position of the satelliteat each even two minutes in universal time forthe next 12 to 16 hours, subsequent to datainjection. These data together with data onthe nominal shape of the orbits of the otherthree satellites, commands and time correctiondata for the satellite and antenna-pointing orders

162.59 for the Injection Station antennas are suppliedFigure 9-12.Four polar orbits to the Injection Stations via the Control Center.

with 45° nodes.

120.95Figure 9-13.Navigation satellite.

Injection Stations

The Injection Stations, after receiving andverifying the incoming message from the Cen-tral Computing Center, store the messageuntil it is needed for transmission to the satel-lite. As soon as the receiving equipment atthe Injection Station receives and locks on thesatellite' s signals, the Injection Station reads theinjection data and commands from storage andtransmits them to the satellite. Transmissionto the satellite is on a frequency different fromthose frequencies used by the satellite, andthe bit rate is much higher; therefore, injectionis completed in a matter of seconds. Oncedata injection is complete, the satellite continuesto transmit at the normal two-minute intervals.

Shipboard Navigation System

The final link in the satellite navigationsystem is the shipboard navigation system andthe one you, as a naval officer, will be mostconcerned with.

The satellite is continuously transmittingmessages. These phase-modulated data on twodifferent radio frequency carrier waves are attwo-minute intervals and start precisely onthe even minute mark. This permits thenavigator to check on any error in the ship'schronometer.

163

/6 7


The satellite is continually up-dating itselfgiving its orbital latitude and longitude coor-dinates and signaling this information earth-ward.

The area in the sky where accurate satel-lite readings can be taken is between 10°and 70° above the horizon (fig. 9-14).The reception pattern is like a large donut inthe sky with the hole overhead. When a satel-lite is passing overhead it has very little dopplerfrequency shift since the satellite and ship areclosely paralleling each other. Since thenavigation principle is based on measuring thedoppler shift, any area above the 70° markis avoided.

A minimum of 6 full minutes, or 3 completesimultaneous satellite messages (at 2-minuteintervals) is required to calculate a navigationfix. Additional periods of received satellitetransmissions will increase the accuracy ofthese computations. A satellite pass may lastfor as long as 16 minutes (eight 2-minuteperiods). Passes suitable for use in obtaininga navigational fix will generally occur at least

every two hours since fourearth-circling satel-lites are in orbit for this purpose.

MASTGROUP

(FIG 9-16)

ELECTRONICSGROUP

(FIG.9-17)

RADIONAVIGATION

SETAN/SRN-9

L

SPECIALPURPOSE

COMPUTER( FIG.9-19)

CONTROLGROUP

(FIG. 9 -18)

BUFFERUNIT

GENERALPURPOSE

COMPUTER

NAVIGATORHAND

COMPUTATION

162.60 (120C)Figure 9-15.Shipboard navigation system,

block diagram.

Figure

RADIO NAVIGATION SET AN/SRN-9

Radio Navigation Set AN/SRN-9 (fig. 9-15),represented in the dotted lines in the blockdiagram, consists of a mast group, electronicsgroup, and a control group. The radio navi-gation set reduces the satellite data to a formwhich is suitable for navigational computations.

The output of the AN/SRN-9 is sent to thecomputing system. There are three methodsof computation: the Special Purpose Computer

120.96 CP-827 (XN-1), the general purpose computer9-14.Determining satellites (which requires a buffer unit) or by navigator

accurate calculation areas. hand computation.

164

16,


VERTICALWHIPANTENNA

UPPERGROUNDPLANE

LOWERGROUNDPLANE

162.64(120C)Figure 9-16.The mast group.

Mast Group

The mast group (fig.. 9-16) receives, sep-arates, and amplifies the two modulated incomingcarriers from the satellite. The dual-frequencyvertical whip antenna receives both the 400MHz and 150 MHz satellite signals. A housingassembly inside the mast group, containingall the electronic circuits, will separate thesignals and amplify each separately. The upperground plane lowers the angle of radiationto establish a good antenna pattern. Thelower ground plane has 12 radial rods at thebase to isolate the mast group from any ofthe ship's hull effects and thus preservesthe antenna pattern.

Electronic Group

The electronics group (fig. 9-17) consistsof a receiver unit, data processor unit, and

165

a power supply unit. This group receives,prepares, and records doppler data, satellitedata, timing information, and refraction cor-rection data for suitable navigation computa-tions by the computer.

THE RECEIVER UNIT.The Receiver Unitis the phase-modulation decoder for the codedbinary signal received from the satellite. Theoscillator in this receiver must be very stable.In case of temporary power failure, the oscillatorrequires a warmup period of 10 hours for eachhour the power is off up to a maximum totalof 72 hours. This amount of time is requiredfor the frequency to stabilize sufficiently forhigh-accuracy navigation. Readings can bemade immediately after power is restored, butaccuracy will be decreased. It is recommendedthat the standby battery be kept in good condi-tion to assure continuous power to the oscil-lator unit in event the ship looses its powersupply. The battery connector (not shown infig. 9-17) is located on the side of the elec-tronic group.

THE DATA PROCESSOR UNIT.The DataProcessor Unit is located in the top drawerof the electronics group (fig. 9-17). It com-bines and processes the timing signals, satel-lite orbit parameters, and the doppler counts.This output information goes to the computerand the control group for printout.

THE POWER SUPPLY.The Power Supplyrequirements for the radio navigation set is115 ±10 VAC, 60 ±6 Hz with a maximum of220 watts.

Control Group

The control group (fig. 9-18) performsthe switching functions and is manually operatedby the navigator. In the TRACK positionof the main control switch, the control groupautomatically searches for, locks on, and tracksthe satellite. The entire navigation fix isprinted out, monitored, and controlled from thecontrol group. The digital printer prints outthe coordinate position of the ship.

/69


Computer

DATA PROCESSOR UNIT

4

RECEIVER UNIT

POWER SUPPLY UNIT

Figure 9-17.Electronics group.

NAVIGATION DIGITAL PRINTERThe computer uses the satellite's position

data and the ship's position data to computea fix in longitude, latitude, and coincidenttime. We have discussed the satellite datasupplied by Radio Navigation Set AN/SRN-9.The navigator will calculate and enter intothe computer the ship's heading and speed,water (currents) direction and speed, estimatedship's position, antenna height, and thetime-of-day accurate to within ±15 minutes.These entries are made at the end of thesatellite pass. Information is always rejectedif the time is less than a 2-minute perioaor is otherwise invalid.

THE SPECIAL PURPOSE COMPUTER.TheSpecial Purpose Con cuter CP-827/SRN-9 (fig.9-19) monitors all 'erations of the Navy'ssatellite navigation program. The two topdrawers hold the electronic logic card circuits.The middle drawer also has the controls andindicators. The bottom drawer contains the115 ±10 VAC 60 Hz single-phase power supplyand the tape' reader. The front panel of the

162.66

MAIN CONTROL SWITCH

Figure 9- 18. Control group. 162.73

Test Device (fig. 9-20), is equipped with neonindicators to give a visual display of the contentsof au the registers and the sequence eventsas they occur in the computer.

166

/'710


Figure 9-19.Digital CoMputer C P-827/SRN- 9. 162.74

162.80Figure 9-20.Test Device CP-827/SRN-9.

The computer readout is located in theelectronics control group (fig. 9-18). A partialsampling of the output printed data is shown

167

/

in figure 9-21. Some of the information thathas been extracted is the doppler count, timeof fix, latitude and longitude, and the offsetfrequency.

THE GENERAL PURPOSE COMPUTER.The General Purpose Computer may be used,but a buffer unit is necessary to process andconvert information into the appropriate com-puter format. The availability and time sharingof a general purpose computer makes this aless desirable choice since it may be requiredfor tactical data processing systems, etc.

HAND COMPUTATION.Hand Computationusing the printed data available from the controlgroup printer of the AN/SRN-9 may be made toobtain a position fix. The complexity of suchcalculations, however, leads to hours of com-putation time and an almost certain probabilityof human error.


3 4 8 3 5 7 9A -4-1 1 0 6 7 0 7 3

- +1206 9 1 0 6- +1306 7 1 4 0- +14062 1 7 5- +000 5 4 2 0 7- +01043235- +0202 92 5 8

0

-+0 3 0 1 4 2 7 4 Units Title and S bol

++1 2 8 1.0 8 1 5 Minutes Time of Perigee (to)+ .14 2 7 5 8 1 7 Deg/Min Mean Satellite Motion - 3 (M - 3)+ 3 2 0.2 0 3 4 Degrees Argument of Perigee (dp)+ .0 0 2 1 4 3 1 Deg/Min Argument of Perigee Change Rate (tM.)+ 0.0 1 1 1 1 5 None Eccentricity+ 0 7 3 7 14.0 1 Kilom. Orbit Semi Major Axis (A0)+ 2 1 1.8 4 8 2 Degrees Right Ascension of the Ascending Node (u.N)

.0 0 0 0 6 3 6 Deg/Min Right Ascension Change Rate (N)+ 0.0 1 5 7 0 7 None Cosine of the Inclination Angle+ 1 3 4.2 8 0 2 Degrees Right Ascension of Greenwich at Time of Perigee (uN)+ 0.9 9 9 8 7 7 None Sine of the Inclination Angle

3 9 7 7 4 9 2. Hertz (Doppler Count)

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* Time of Fix (GMT) (Twenty hundred hours twenty-six minutes)2 0 2 6 *

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99- 0 7 5 5 9 9 9 Initial Estimates

97+ 3 1 9 9 9 9 9

0 3 9 0 9 7 782

0 7 6 5 3 8 3 Second Iteration48

3 1 9 6 2 1 9

0 3 9 0 9 7 7 Latitude: 39° 09.7782' North820 7 6 5 3 8 3 Fix Result} Longitude: 76° 53.8350' West50

+ 3 1 9 6 2 1 9 Offset Frequency: 31,962.19 Hertz**

Figure 9-21.Printer readout navigation information.

168

172

120.97


INTEGRATED DOPPLER NAVIGATION

The navigational fix computed by RadioNavigation Set AN/SRN-9 is based on the shiftin frequency (doppler frequency shift) that occurswhenever the relative distance between a trans-mitter and a receiver is changing. Such changesoccur whenever a transmitting satellite passeswithin radio range of a receiver on earth andis due to the motion of the satellite in its orbit,the motion of the navigator on the surface ofthe earth, and the rotation of the earth aboutits axis. (You may choose to review the dopplereffect in chapter five.)

than at time T2 along S2, which is thereason for the doppler frequency shift. Asthe satellite approaches, additional cycles mustbe received to account for a reduction in thenumber of wavelengths along the propagationpath. Every positive doppler cycle receivedmeans the satellite has moved one wavelengthcloser. This is a very precise measurementbecause at 400 MHz a wavelength is only3/4 meter long.

The principle of satellite navigation involvesestablishing a fix at the intersection of two ormore hyperbolas of revolution. A hyperbolaof revolution in satellite navigation (fig. 9-23)

c nninoul CO C II/WIWI GO C MIIMU I CO

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IME I

'''r77.7.77":77:r7777rr7r:'r777777r77:77-EARfli 7-177

Figure 9-22.Integrated doppler measurement.

As previously stated, the satellite messagedescribes the orbital position of the satelliteevery two minutes on the even minute. Toobtain a navigational fix, it is necessary onlyto determine the ship's location relative to theknown satellite positions. The Radio NavigationSet AN/SRN-9 utilizes a so-called integrateddoppler measurement for this purpose. Figure9-22 illustrates four positions of the satellitein its orbit for arbitrary times shown as Tithrough T4. The slant range from ship tosatellite is given by 51 through S4. It is evidentthat the number of wavelengths of the transmittedsignal en route at time Ti along Si is greater

/ 7169

120.98

120.99Figure 9-23.Principle of satellitenavigation, hyperbola of revolution.


is a three-dimension geometric figure as com-pared to the two-dimension figure used in lorannavigation (fig. 9-1B). Using the known posi-tions of the satellite at T1 and T2 as foci androtating a hyperbola (on the axes which willalign with the satellite's orbit) establishes ahyperbola of revolution.

The hyperbola of revolution is electronicallyestablished when satellite positions at T1 andT2 are known and the integrated doppler meas-urement (being the count of the number ofdoppler cycles received between T1 and T2)has determined the direct measure of the totalchange in slant range during the two-minutetime interval. The receiver must be on somesurface defined by this measured slant rangeDIFFERENCE between these two points. Theship will be located, therefore, somewhere alongthe curve defined by the intersection of thishyperboloid and the earth's surface. This doesnot establish the location of the earth's surfacenor does it tell upon which of the two branchesof the hyperboloid the ship will lie. It does, how-ever, establish electronically the shape of thehyperbola of revolution used.

The next doppler count (between T2 andT3) will define a second curve, and the inter-section of these curves (not illustrated) givesthe navigational fix.

In actual practice, two factors complicate thissimple explanation. First, the doppler signalwhich is counted consists of the doppler frequen-cy plus a fixed, but not very accurately known,bias frequency which is the inherent variations offrequency differences between the transmitteroscillator in the satellite and the receiver oscil-lator aboard ship. Therefore, a third dopplercount is required in order to solve for the threevariableslatitude, longitude, and bias fre-quency. This means that integral doppler countsfor at least three two-minute intervals must beused (and preferably more than three) in order todetermine the three unknoWns. The second com-plication is the motion of the ship during the sat-ellite pass. To account for this, the best estimateof a ship's motion must be entered into thenavigational computation along with the dopplercounts and the satellite message.

TACAN NAVIGATION SYSTEM

Tactical air navigation (tacan), is an elec-tronic polar coordinate system that enablesan aircraft pilot to readinstantaneously and

170

continuouslythe distance and bearing of aradio beacon transmitter installed on a shipor at a ground station. In aircraft equippedwith tacan receiving equipment, an azimuthindicator shows the position of the transmittingsources in degrees of magnetic bearing fromthe aircraft. Also, the distance in nauticalmiles to the same reference point is registeredas a numerical indication, similar to that ofan automobile odometer. (Fig. 9-24) In the

MAGNETICNORTH

32.73Figure 9-24.Tacan polar coordinate

presentation data.

illustration, the aircraft is 106 miles from thecarrier, and the ship is on a magnetic bearingof approximately 230° from the aircraft.

To provide for a large number of trans-mitting stations, the system operates on 126selectable channels. No two stations withininterference distance of each other are assignedthe same channel. The pilot can switch channelsto select any tacan transmitter within range.

To aid the pilot in identifying a particulartransmitter, the transmitter automaticallytransmits a three-letter tone signal in inter-national Morse code every 37.5 seconds. Theaircraft receiver converts the signal to anaudible tone that is heard in the pilot's head-set.

Two radio frequencies are employed, asindicated in figure 9-25. One frequency (Y)


70.16Figure 9-25.Dual-frequency transmission.

is used for transmissions to the ai re raft; anotherfrequency (X) is used for transmissions fromthe aircraft. The surface-to-air frequency car-ries bearing and range intelligence as wellas station identification information. The trans-mission from the aircraft-to-surface unit isrequired to trigger the distance-measuringsystem.

When the pilot closes the proper switchon his set control, his receiver-transmitterradiates a series of range interrogation pulses(frequency X).

The interrogation pulses are detected byany ship or station operating on the samechannel. The pulses cause the transmitterto radiate a response, which is a series ofpulses on frequency Y.

When the reply signal is received in theaircraft, it is fed to range circuits that determine

171

/ 75

the time that elapsed during the round trip ofthe two signals. Other circuits convert thetime difference to equivalent dial indication inmiles. Bearing information is radiated con-tinuously on frequency Y.

The shipboard end of the system is theAN/SRN-6( ) (discussed in the next topic) orits older counterpart, the AN/URN-3( ). Theairborne installation is a combinationtransmitter-receiver-indicator, such as theAN/ARN-21( ).

TACAN RADIO SET AN/SRN-6( )

Radio set AN/SRN-6( ) is replacing theAN/URN-3 as tacan radio sets on board ship.The AN/SRN-6( ) system (fig. 9-26) comprisesthree major groups: receiver - transmitter,antenna, and power supply assembly.

As many as 100 aircraft may simultaneouslyobtain navigational information in conjunctionwith a single installation of the AN/SRN-6( ).The set is capable of receiving on any one of126 frequencies (channels) in the range of1025 to 1150 MHz. Transmission of informationalso takes place on 126 channel frequencies inthe ranges of 962 to 1024 MHz and 1151 to1213 MHz.

Two types of antennas are available for use.Each antenna operates on 63 channels, cor-responding to low band frequencies and high-band frequencies, respectively. Low-band in-stallations transmit at frequencies between 962and 1024 MHz inclusive, and receive atfrequen-cies between 1025 and 1087 MHz. High-bandinstallations transmit in the range of 1151 to1213 MHz, and receive in the range of 1088 to1150 MHz.

Two frequencies are used in each channel:one for receiving, and one for transmitting.The frequency used for receiving in low-bandinstallations is 63 MHz above the frequency usedfor transmitting in the same channel.


I-

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ADAPTER

RADIO SET

POWER SUPPLYTEST SET

GROUP

RECEIVERTRANSMITTER

GROUP

RADIOFREQUENCY

MONITOR

Figure 9-26. Radio Beacon AN/SRN-6 major components.172

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32. 72

CHAPTER 10

INTRODUCTION TO DIGITAL COMPUTERS

The Navy's reliance on computer technologyhas greatly increased in recent years becauseof the ability of computing systems to providefast and accurate analysis of logistical andtactical operations. Computing systems arehighly reliable and can perform several opera-tions simultaneously.

Computers are divided into two generaltypes, analog computers and digital computers.The analog computer is one which solvesproblems by translating physical conditions;such as flow, temperature, pressure, angularposition, and size of displacement into equivalentelectrical quantities. These electrical measure-ments are continually being updated as thephysical values change.

The gasoline gage on an automobile is onetype of analog computer. The liquid in thegasoline tank operates a float which, in turn,physically controls the amount of battery currentflowing through a rheostat mounted at the tank.The amount of current is proportional to theamount of gasoline in the tank and positionsyour gasoline gage to a position on the scaleindicator which indicates the approximateamout of gasoline in the tank. Thus an analogcomputer gives an approximate solution in acontinuous form, whereas a digital computergives exact data solutions of discrete values.

The digital computer is one which solvesproblems by repeated high speed use of thefunriamental arithmetic process of addition,subtaction, multiplication, or division inbinary,decimal or any pre-determined notation. Thedigital computer uses increments (digits) toexpress distinct quantities.

An example of a digital computer is acash register. Certain specific digits areentered at the console and stored, and uponrequest, a digital output representing the sum(or difference) is printed out. Other digitalcomputers include the abacus, desk calculator,punchcard machine, and the modern electronic

173

computer. The coverage in this text willbe devoted to the digital computer.

Digital electronic computers are classifiedas special-purpose or general-purpose com-puters. The special-purpose computer isdesigned to handle a specific type of dataprocessing task as exacting and as efficientlyas possible. A general-purpose computeris designed to handle a variety of data processingtasks in which its adaptability, storage capacityand speed are adequate.

Some of the more common places wherecomputers are used (mostly ashore but someafloat) are in command activities, operationcenters, communications, finance, medical,weather, supply, maintenance, oceanography,weapon systems, and Naval Tactical DataSystems.

BASIC COMPUTER

The oldest and still most common dataprocessor is man. In fact, man is still themost efficient data processor if size, mass,and power consumption are used as the criteria.The input to the human data processor ismostly through the eyes and ears. Hismemory (brain) stores data to be processedand the instructions for processing the data.His brain also functions as the arithmeticand logic element and as the control element.The output can be verbal, written, a physicalaction or a decision not to act.

Taken in perspective, the human being isthe most versatile data processor. He hasthe ability to interpret his instructions insuch a way that they will cover situationsthat were not explicit in the original form ofthe instructions. This, by the way, is not anability inherent in the electronic data processor.

Although man is a versatile data processor,he has some rather serious shortcomings.

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His memory capacity is rather limited (ona given subject). He is also unreliable. Whencalled upon to remember large quantities ofdata, he has an annoying tendency to forgetdetails. His calculating ability is quite limited.The average person, using only his mind, isunable to perform a series of simple cal-culations. Unaided, man is rather slow in per-forming the simplest data processing operation.

In addition, man is unreliable when per-forming repetitious operations. Most dataprocessing operations are repetitious, i.e.,the same basic operation is performed manytimes using different pieces of data. Man'sability to think tends to interfere with hisperformance of these boring operations. Thus,although man is a remarkable data processor,he needs some auxiliary equipment if he is to bepart of an efficient data processing system.

The basic computer (fig. 10-1) is madeup of a central processing unit and the input/output devices. Data processing equipmentshave five functions associated with them: input,storage, control, arithmetic, and output. Thecomputer's input section introduces data intothe system. Once interpreted, the informationis sent to a control section where it is furtherdirected according to programmed instiuctions.As specified, the data is sent to storage ormemory, a high-speed device able to readin and read out data in a few millionths ofa second. Data in storage can be used overand over, or can be used only once and replaced.If the computer is so instructed, the data canbe directed to the processor or arithmeticsection. It is here that the computer reallycomputes; adding, subtracting, and comparingnumbers. The organized results are transfer-able to an output section for the creation ofrecords and reports, or to produce new mediafor further processing needs.

CENTRAL PROCESSING UNIT

The basic sections of a digital computer areshown in figure 10-1. The three center blocks(arithmetic logic, memory, and control units)comprise what is generally referred to as theCentral Processing Unit or central dataprocessor.

Control Unit

The control section is comparable to a telephoneexchange. It directs the operations of the

computer under the direct influence of a sequenceof instructions called the "program". Theinstructions are comparable to the phonenumbers dialed into a telephone exchange andcause certain switches and control lines tobe energized.

The program may be stored in the internalcircuits of the computer or it may be readinstruction-by-instruction from external media.The internally stored program type of computer,generally referred to only as a "storedprogram" computer, is the most practical typeto use when speed and fully automatic operationare desired.

In addition to the command which tellsthe computer what to do, the control unitalso dictates how and when each specificoperation is to be performed. It is alsoactive in initiating circuits which locate anyinformation stored in the computer and inmoving this information to the point wherethe actual manipulation or modification is tobe accomplished.

In the stored program computer, the controlunit reads an instruction from the memorysection (as instructed by the program). Theinformation read into the control unit frommemory is in the form of voltage levels thatmake up a "binary word," and representsa specific operation that is to be performed.The location of the data to be operated onis generally a part of the instruction, andenergizes circuitry which causes the specifiedoperation (add, subtract, compare, etc.) to beexecuted. Subsequently, the control unit readsthe next instruction or jumps as directed,(explained later) to find the next instructionto execute.

The four major types of instructions are:(1) transfer; (2) arithmetic; (3) logic; (4) control.Transfer commands are those whose basicfunction is to transfer data from one locationto another. One of the locations is an addressin memory and the other is either a registeror an input/output device. Arithmetic instruc-tions are those which combine two pieces ofdata to form a single piece of data using oneof the arithmetic operations. In some typesof computers, one of the pieces of data isin a location specified by the address containedin an instruction, and the other is already in aregister (usually the accumulator). The resultsare usually left in the accumulator.

Logic instructions make the digital computerinto a system which is more than a high speed

174

1 71

Chapter 10INTRODUCTION TO DIGITAL COMPUTERS

CENTRAL PROCESSING UNIT

OUTPUT

CARD PUNCH PRINTER

MAGNETIC TAPE

Figure 10-1.Representative digital computer.

adding machine, By using logic instructionsthe programmer may instruct the system onvarious alternate sequences through theprogram. For example through the use oflogic instructions, a computer being used formaintenance inventory will have one sequence

120.100.2

to follow if the number of a given item onhand is greater than the order amount andanother sequence to follow if the number onhand is smaller than the order amount. Thechoice of which sequence to use will be madeby the control unit under the influence of the

175

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1


logic instruction. Logic instructions providethe computer with the ability to make decisionsbased on the result of previously generated data.

Control instructions are those which areused to send commands to devices which arenot under .direct command of the control unit,such as input/output units. The addresscontained in the instruction does not specifya location in memory but is usually a codegroup specifying an action required of aparticular piece of equipment.

In a single address computer, i.e., whereeach instruction refers to only one addressor operand, the instructions are normally takenfrom the memory in sequential order. Ifone instruction comes from a certain location,say X, the next instruction is usually takenfrom location X + 1. However, the executionof a logic instruction may produce a resultwhich dictates that the next instruction is tobe taken from an address as specified in aportion of the logic instruction. For example,the logic instruction may cause certain opera-tions in the computer to determine if thecontent of a given register in the arithmeticsection is negative. If the answer is "yes,"the location of the next instruction is thatspecified in an address section of the logicinstruction. If the answer is "no," the nextinstruction would be taken from the nextsequential location in the memory.

Every computer provides circuitry for avariety of logic instructions for choosingalternate instruction sequences if certaindesirable or undesirable conditions exist. Theability to "branch" at key points is the specialfeature of the computer that makes it ableto perform such diverse tasks as missilecontrol, accounting, or tactical air plotting.

Arithmetic Unit

The arithmetic unit of the computer is thesection in which arithmetic and logic operationsare performed on the input or stored data.The arithmetic operations performed in thisunit include adding, subtracting, multiplying,dividing, counting, shifting, complementing, andcomparing.

All arithmetic operations can be reducedto any one of four arithmetic processes;addition, subtraction, multiplication, ordivision.In most computers, multiplication involves aseries of additions; and division, a series ofsubtractions.

176

The arithmetic unit contains several reg-isters; units which can store one "word" ofcomputer data. This group of registers generallyinclude D, X, and Q registers (so named foridentification purposes only), and a unit calledan "accumulator" (A register). During anarithmetic process, the D, X, and Q registerstemporarily hold or store the numbers beingused in the operation, called "operands". Theaccumulator stores the result of the operation.The control unit instructs the arithmetic unitto perform the specified arithmetic operation(as requested in the instruction); transfersthe necessary information into the D, X, and Qregisters from memory (discussed later); andcontrols the storage of the results in theaccumulator or in some specific location inmemory.

The arithmetic unit also makes comparisonsand produces "yes" or "no" or "go-no-go"outputs as a result. The computer may beprogrammed so that a "yes" or "go" resultadvances the computer units to perform thenext step in the program, whereas a "no" or"no-go" instruction may cause the computerto jump several programmed steps. A computermay also be programmed so that a "no"result at a certain point in the program willcause the computer to stop and await instructionsfrom a keyboard or other input device.

Generally information delivered to thecontrol unit represents instructions, whereasinformation routed to the arithmetic unitrepresents data. Frequently it is necessaryto modify an instruction. This instructionmay have been used in one form in one stepof the program but must be altered for asubsequent step. Yr. such cases, the instructionis delivered to the arithmetic unit where itis altered by addition-to or subtraction-fromanother number in the accumulator. Theresultant modified instruction is again storedin the memory unit for use later in the program.

Memory Unit

In most digital computers the storage ormemory section is constructed of small magneticcores, each capable of representing an "ON"("1") or "OFF" ("0") condition. A systemof these cores arranged in a matrix can storeany computer word which is represented inbinary form.

All computers must contain facilities tostore computer words or instructions (which

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r.


are intelligible to the computer) until theseinstructions or words are needed in the per-formance of the computer calculations. Beforethe stored program type computer can beginto operate on its input data, it is first necessaryto store, in memory, a sequence of instructionsand all figures, numbers, and any other datawhich are to be used in the calculations.The process by which these instructions anddata are read into the computer is called"loading."

Actually the first step in loading instructionsand data into a computer is to manually placeenough instructions into memory by using theconsole or keyboard so that these instructionscan be used to bring in more instructionsas desired. In this manner a few instructionsare used to "bootstrap" more instructions.Some computers make use of an auxiliary(wired) memory which permanently stores the"bootstrap program," thereby making manualloading unnecessary.

The memory (or storage) section of acomputer is essentially an electronicallyoperated file cabinet. It is actually a largenumber (generally between 1 and 40 thousand)of storage locations; each referred to as astorage address or register. Every computerword which is read into the computer duringthe loading process is stored or filed in aspecific storage address and is almost instantlyaccessible.

Input/Output Unit

Input and output devices are similar inoperation but perform opposite functions. Itis through the use of these devices that thecomputer is able to communicate with theoutside world.

Input data may be in any one of threeforms: it may be fed in manually from akeyboard or console; from instruments orsensors; or from a source on which datahas previously been stored in a form intelligibleto the computer.

Computers can process hundreds ofthousands of 'computer words per second.Thus, a study of the first method (manualinput) reflects the incompatibility of human-operated keyboards or keypunches to supplydata at a speed which matches the electronicspeed of digital computers. A high averagespeed for keyboard operation is 2 or 3characters per second, which when coded to

LP/

form computer words may have more than15 to 20 binary digits. The computer iscapable of reading several thousand times thisamount of information per second. It is clear,therefore, that manual inputs should beminimized to make more efficient use ofcomputer time.

Instruments are used as input sensors,and are capable of supplying several thousandsamples regarding pressure, temperature,speed, etc., per second. This is equivalentto 10 or 20 thousand bits or binary digitsper second. Digital computers which usethese devices must be equipped with analog-digital converters to convert physical changeto specific increments.

Input data which has previously been recordedon punched cards, perforated tapes, magnetictapes or magnetic drums or disks in a formunderstood by the program may also be enteredinto the computer, this being a much fastermethod than entering data manually from akeyboard. The most commonly used inputdevices in this category are magnetic tapereaders or paper tape (perforated tape) readers.

Output information is also made availablein three types: human information, such ascodes or symbols presented on a cathode-rayscreen which are used by the operator toanswer questions or make decisions; informationwhich operates a control device such as alever, aileron, or actuator; or informationwhich is stored in a machine language orhuman language, on tapes, or printed media.

Devices which store or read-out outputinformation include magnetic tape, punchedcards, punched paper tapes, cathode-rayoscilloscopes, electric typewriters, line-at-a-time printers, and surface-at-a-timeprinters.

One of the main features of computers istheir ability to process large amounts of dataquickly. In most cases, the processing speedfar exceeds the ability of input devices tosupply information. One common limitation ofmost input devices is that each involves somemechanical operation, that is, the movement of atape drive or card feeder. Because a mechanicalmovement of some part of these devices cannottake place fast enough to match electronicspeeds within the computer, these input deviceslimit the speed of operation of the associatedcomputer particularly in cases where successiveoperations are dependent upon the receptionof new data from the input medium.

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t.


Several methods of speeding up mechanicaloperations have been devised, all of whichare designed to move a smaller mass a shorterdistance and with greater driving force. Manyof these designs have been directed towardincreasing the drive speed of magnetic tapes.Present day tape drives can pass up to 150inches of tape per second over a tape readinghead. Card readers can read between 100and 2000 cards per minute, depending on theparticular reader.

Another method of entering data into acomputer which has not previously beenmentioned is to link two (or more) computerstogether and program them to communicatewith each other. This is the fastest methodof entering or extracting data.

COMPUTER OPERATIONS

With an understanding of the function ofthe various computer sections, let us nowconsider a basic computer instruction andhow this instruction is executed. Let theinstruction be as follows:

"Add the contents of the A registerto the contents of memory address loca-tion 123 and store the results in address456 in memory."

We will assume that the computer usedis the stored program type and that allinstructions, data, numbers, and symbols havebeen previously loaded or stored in memoryat known addresses. The stored input mayhave been read from a magnetic tape (similarto that used with commercial tape recorders),from paper tape (similar to that used withteletype), or from punched cards.

If the instruction to be executed is thefirst programmed operation, energizing thestart button will cause the control unit toissue an order "Read instruction." Theinstruction will be read into a register inthe control unit where it will remain throughoutthe execution cycle.

Note that the mathematical operationrequested in the instruction is ADD. Theinstruction word thus contains a code whichis interpreted by the control unit as ADD.

After reading the instruction, the controlunit automatically energizes circuits whichwill (1) read-out the contents of memoryaddress 123, (2) .' transfer this information to

a register (say the X register) in the arithmeticunit, and (3) perform an add X to A operation.

The ADD process is thus accomplished,being constantly monitored by the control unitto ensure that no further actions are initiatedbefore the ADD operation is completed. Theresults of the ADD operation are stored inthe accumulator from which, by control request,it is transferred to address 456 in memory.This ends the instruction. The control unitwill read and execute the next instruction.

If the result is to be displayed at theoutput immediately or at a later time (asstipulated in the programmed instructions) thecontrol unit upon receipt of the instructionwill issue an order to read-out the contentsof memory address 456. Because read-out(which sometimes involves printing by someelectromechanical apparatus) is extremelyslow as compared to computer speed, mostcomputers use a secondary storage devicecalled a buffer into which data is readdirectly from the primary (main) storage atcomputer speeds. When read-out is desired,the control unit enables the buffer storageto read-out all or any part of the bufferstorage data. The buffer read-out is independentof the main computer operation, and in somecomputers only one instruction is required tostart and stop the read-out process.

COMPONENTS USED IN COMPUTERS

Unlike the mechanical computer, suchas adding machines and odometers which arebased on the decimal (ten) digit system,moderii electronic computers use componentswhich will represent only 2 conditions. Theseconditions are sometimes referred to as the1 (energized) or 0 (deenergized) states. Earlycomputers used relays and electron tubes;now transistors and silicon or germaniumdiodes are used because of the higher speedsat which they can react, and too, because oftheir lower power consumption.

Electronic circuits used in computers arebasically simple. To a large extent thesecircuits are of four types: the OR circuit whichproduces an output when one or more of itsinputs are active, that is, in the one state: theAND circuit which yields an output only whenall inputs are active; the flip-flop circuitwhich is a bistable multivibrator; and theinverter circuit which yields a high output witha low input or a low output with a high input.

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liA


COMPUTER TOOLS

Components or tools of a computer systemare categorized as either hardware or software.Hardware includes all the mechanical, electri-cal, electronic, and magnetic devices within acomputer system. Software consists of theautomatic programming materials developedfor the most efficient use of the hardwareand is usually supplied by the manufacturerof particular systems.

Hardware.Computer hardware falls intotwo categories, peripheral equipment and thecentral processor. PERIPHERAL EQUIPMENTincludes all input and output devices associatedwith specific recording media such as, a cardreader and punch with punched cards, ormagnetic tape units with magnetic tape. Thisperipheral equipment can operate ON-LINEunder direct control of the central processoror OFF-LINE, independently of the centralprocessor.

As previously stated the CENTRALPROCESSOR includes the Control, Arithmetic,and Memory units.

During ON-LINE operations, data can betransferred to and from peripheral devicesand the central processor under the influenceof CONTROL UNITS. These units may befree-standing, or built into either the centralprocessor or the peripheral device, and receivetheir signals or instructions from the storedprogram.

In OFF-LINE or AUXILIARY operations, theinput and output devices are used in conjunctionwith other peripheral devices not directly con-nected to the system. Since input output dataconversion operations are relatively slow com-pared to the speed of the central processingunit, off-line operations free the computer oftime-consuming procedures and provide moretime for the computing and processing of databy the central processor. For example, asystem's output data could be written on mag-netic tape (because of its speed) and, in an off-line operation, converted to some other recordformby a slower device. This allows thecomputer to continue processing new data.

Software.This consists primarily of gen-eral purpose programs that are common tomany computer installations. Included amongthem would be assemblers and compilers which

aid in producing machine language routinesfrom a relative or nonmachine language source,plus sort, control, and other utility programs.

ELECTRONIC DATA PROCESSINGEQUIPMENTS

In certain respects, electronic dataprocess-ing is similar to the unit record system in thatpunched cards may be used as input, and printedreports or punched cards may be produced asoutput. The unique difference lies in the mannerof processing the data and the electronic equip-ment used in its processing applications. Where-as the unit record system required the physicalmovement of cards from one machine to another,the electronic system permits many processingfunctions to be performed in one operation.This is made possible through the use of severalinterconnected devices which, working together,can receive, process, and produce data in oneoperation without human intervention. Thesedevices constitute an electronic data processingsystem.

The operations of preparing source docu-ments, punching cards from source documents,and (for a punched card EDPS) sorting punchedcards, are accomplished by the same methodsused in the unit record system. However,systems using magnetic tape for input generally.have punched card data transcribed onto thetape, and it in turn is sorted into a sequenceacceptable for processing by the computer.Once information has been entered into thesystem, all classification, identification andarithmetic operations are performed automati-cally in one or several processing routines.This is accomplished by a set of written instruc-tions called a PROGRAM which, when recordedonto punched cards or magnetic tape and fed intothe system, controls operations automaticallyfrom start to finish.

Information used as input to an electronicdata processing system may be recorded onpunched cards, paper tape, magnetic tape, ormagnetic ink or optically read documents,depending upon the system requirements.Similarly, output may be in the same formswith the addition of printed reports, againdepending upon the system.

Figure 10-2 shows some of the majorElectronic Data Processing (EDP) equipmentspresently in use.

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/si3


UNIT RECORDS

CARD PUNCH

CARD VERIFIER

CARD SORTERS

...........

TOW MATIOPIAL

..e.411.

4011/01:11894# 1110 1010000000111

.-=1117.1.-

0,4112ft

RELATED FACTS TREATED ASA UNIT, RECORDED ON INPUTMEDIA ACCEPTABLE TO ADATA PROCESSING SYSTEM.

A MACHINE WHICH ALLOWS ANOPERATOR TO PUNCH DATAINTO CARDS FOR CONVEYANCEINTO OTHER MACHINES ORDEVICES. SYNONOMOUS WITHKEYPUNCH.

CHECKS ORIGINAL PUNCHINGOF DATA IN CARDS FORTRANSCRIPTION ERRORS.

SELECTS OR ARRANGESPUNCHED CARD UNIT RECORDSIN A DESIRED SEQUENCE.

Figure 10-2.Representative Electronic Data P...ocessing Equipments.'

180

49.215.1


ACCOUNT INGMACHINE

INTERPRETER

REPRODUCER

COLLATOR

1004 CARDPROCESSOR

Ulk PERFORMS END OF THE LINEPROCESSING OF PUNCHEDCARDS THROUGH ITS ABILITYTO ADD, SUBTRACT, ANDPRINT REPORTS. SYNONYMOUSWITH TAB AND TABULATOR.

READS, INTERPRETS, ANDPRINTS PUNCHED CARD DATAON THE FACE OF A CARD.

USED PRIMARILY TO CREATENEW FILES BY REPRODUCINGALL OR PORTIONS OF DATAFROM ONE UNIT RECORD TOANOTHER, OR ADDING NEWINFORMATION TO EXISTINGFILES.

A FILING MACHINE USED TOARRANGE OR SEL ECT CARDSFOR SUBSEQUENT OPERATIONS.

A SOL ID-STATE ELECTRONICPROCESSING MACHINE WITH ANEXTERNAL CONTROL PANEL,INCORPORATING CARD READ-ING, ARITHMETIC PROCESS-ING, AND PRINTING FUNCTIONS.

49.215.2Figure 10-2.Representative Electronic Data Processing Equipments(Cont'd).

181


CEI-TRALPROCESSING

UNIT

SY ,TEM CONTROLUNITS

CONSOL E

CARD READPUNCH

MAGNETIC TAPEUNIT

THAT PORTION OF A COM-PUTER EXCLUSIVE OFPERIPHERAL EQUIPMENTTHAT CONTAINS THE MAINSTORAGE, ARITHMETIC-LOGICUNITS, AND CONTROL SEC-TION. SYNONOMOUS WITHCPU.

USED PRIMARILY TO CONTROLALL OPERATIONS INCLUDINGINPUT AND OUTPUT FUNC-TIONS.

PROVIDES EXTERNAL CON-TROL OF A DATA PROCESSINGSYSTEM. USED MAINL Y TODETERMINE THE STATUS OFCIRCUITS, COUNTERS, PANELREGISTERS, AND CONTENTSOF STORAGE.

AN INPUT AND OUTPUT DEVICETHAT READS AND CONVERTSPUNCHED CARD DATA FORTRANSFERENCE INTO STOR-AGE OR ONTO MAGNETICTAPE; TRANSFERENCE FROMSTORAGE OR MAGNETIC TAPETO PUNCHED CARDS; CAN BEINDIVIDUAL UNITS.

INPUT AND OUTPUT DEVICECAPABLE OF READING ANDWRITING INFORMATION(REPRESENTED BY MAGNETICSPOTS) ON AND FROMMAGNETIC TAPE.

49.215.3Figure 10-2.Representative Electronic Data Processing Equipments(Cont'd).

182

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INPUT AND OUTPUT DEVICESWHICH CAN SENSE AND PUNCH

PAPER TAPE THE HOLE PATTERNS OF PAPERREADER ANC Ti PE, COULD BE A COMBINED

PUNCH UNIT.

HI-SPEEDPRINTER

DISK STORAGE

DRUM STORAGE

A PRINTER OUTPUT DEVICEWHICH OPERATES AT A SPEEDCOMPATIBLE WITH THE SPEEDOF COMPUTER COMPUTATIONAND PROCESSING, ENABL INGIT TO OPERATE ON-L INE IFNECESSARY.

A STORAGE DEVICE INADDITION TO MAIN STORAGE OFTHE CPU WHEREIN DATA ISRECORDED BY MAGNETICSPOTS ON THE SURFACE OFFLAT CIRCULAR MAGNETICDISKS.

A STORAGE DEVICE INADDITION TO MAIN STORAGE OFTHE CPU WHEREIN DATA ISRECORDED BY MAGNETICSPOTS ON BANDS OR CHANNEL SOF A ROTATING CYL INDER.

49.215.4Figure 10-2.Representative Electronic Data Processing Equipments (Cont'd).

183

/6r17

a


DIGITAL DATARECORDERREPRODUCER

RD-270(V) /UYK

DIGITAL DATACOMPUTER

CP-789(V)/UYK

CARD READER PUNCHINTERPRETER UNITRD-293/UYK-5(V)

-I

INPUT /OUTPUTKEYBOARD PRINTER

TT -515 /UYK

I

Figure 10-3.Data Processing Set AN /UYK -5(V).

DATA PROCESSING SET AN/UYK-5(V)

The Data Processing Set AN/UYK-5(V)(fig. 10-3) is a general purpose processingsystem developed for shipboard installationsof the Standard Navy Maintenance and MaterialManagement (3M) system. It includes:

Digital Data Computer CP-789(V)/UYK

Digital Data Recorder-ReproducerRD-270(V)/UYK

Card Reader-Punch-Interpreter UnitRD-293/UYK-5(V)

Input/Output Keyboard Printer TT-515/UYK

Data Processing Line PrinterRO-302/UYK-5(V)

Motor-Generator PU-655/U (notshown)

The handling of supplies and accounts isaccomplished by a stored program type

184

120.100(120C)

real-time digital data computer. During the ex-ecution of stored instructions from memory, theinput/output section is continuously monitoredand whenever any peripheral equipment connect-ed to the computer has a request to send datato the computer or wants data from the computer,the computer program interrupts and honorsthe input/output request. After input or output,the computer resumes executing programmedinstructions as stored in memory.

The input/output sections have four channelsavailable. All input/output transfers are buf-fered under buffer control so that they do notrequire program attention, and will operate atthe rate required by the external device.

DIGITAL DATA COMPUTERCP-789(V)/UYK

The computer (fig. 10-4) consists of apower control panel, with either four or sixpull-out bays and a power supply. The upper

I"


POWER CONTROLPANEL

CONTROL PANEL I

INPUT/OUTPUTCONTROL PANEL

CONTROL PANEL 2

MEMORY PANEL

120.100.2Figure 10-4.Digital Data Computer CP-789(V)UYK.

185

/a'


left bay contains the input/output section logicand switches. The upper right bay (controlpanel 1) contains the arithmetic section logicand some of the control section logic andswitches. The lower left bay contains thecomputer memory. The lower right bay (con-trol panel 2) contains control section logicand switches. If six pull-out bays are present(not shown), the upper bay is empty and thelower bay contains a larger core memory.The pull-out bays extend forward to facilitateaccess to the printed-circuit cards, switches,and memory modules. Internal blowers coolthe computer.

The computer is basically an automatic ma-chine, however there are certain switches andcontrols that affect computer operation. Theseswitches and controls provide means of select-ing computer opc. rat; ng speed, selecting optionalprogram jumps or stops, selecting input/outputmodes, and setting and clearing the registers.

DIGITAL DATA RECORDER-REPRODUCERRD-270(V)/UYK

The RD-270(V)/UYK magnetic tape unit (fig.10-5) is a large capacity, medium speed, mag-netic tape storage system. It is capable ofreceiving data from the computer and record-ing it on magnetic tape or retrieving informa-tion previously recorded on tape and trans-ferring it to the computer. It is usually usedon-line, but it may be used in an off-line modeof operation with the high speed printer. In-formation recorded on magnetic tape is re-trieved and transferred to the high speedprinter for reproduction in printed form.

Card Reader-Punch-Interpreter SetRD-293/UYK-5( )

The RD-293/UYK-5( ) (fig. 10-6) unit is acomputer input/output device that provides in-terim storage for, and intermediate controlover information transmitted between the com-puter and keyboard-printer, high-speed printer,and reader-punch interpreter system. Thereader-punch-interpreter assembly is an on-line panel-mounted card reading, punching, andprinting system. It consists of a card punchhead assembly, a printer head assembly, twophotoelectric reading stations, an input cardhopper, two output card stackers, and theelectrical mechanical and pneumatic devices

186

necessary to select, transport, process andstack standard size 80-column cards.

Input/Output Keyboard PrinterTT/515/UYK

The teletypewriter set (fig. 10-7) providesa means by which an operator can convenientlytransmit information to and receive directreplies from the computer. As an input devicethe unit can be used for manually loading pro-grams and other input data, for example, con-stants and program parameters, into the com-puter; for altering existing programs, portionsof a program, or constants stored in the com-puter memory, and for initiating and terminatingvarious computer operations. As an outputdevice the unit can be used for printing outerrors, conditions requiring decisions or op-erator intervention, and various types of com-puter output data. The control logic for thekeyboard printer is incorporated in the cardreader-punch-interpreter cabinet.

DATA PROCESSING LINE PRINTERR 0- 302/UYK- 5(V)

The RO-302/UYK-5(V) is a high speed line/printer system consisting of two major sections(fig. 10-8) referred to as a printing compart-ment (mechanical section on left side) andelectronics compartment (on right side).

The printing compartment houses a highspeed line/printer mechanism which consistsof a drum gate assembly, interlock, drummotor, position pickup, paper feed assemblypaper interlocks, paper feed stepping motor,and paper feed magnetic pickup.

The electronics compartment consists of twopower supplies, printed logic chassis, twoprinted-circuit card chassis and cards, twocapacitor banks, fuse panel and a controlcircuit for the paper feed stepping motor.

The high speed line/printer can be used asan on-line computer output device which pro-duces printed copy in alphanumeric form frombinary-coded computer output data. The unitis capable of printing 64 different charactersincluding the upper case alphabet, numerals 0through 9, punctuation symbols, and spezir.1characters.

The high-speed printer control panel con-tains all the controls and indicators necessary


TAPE REEL

INDICATORS ANDCONTROLS

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7 MAGNETIC TAPECONTROL PANEL

120.100.1Figure 10-5.Digital Data Recorder-Reproducer RD-270(V)/UYK.

187

/I/


RIBBON MAGAZINE HOOD ASSEMBLY CARD PUNCH PICKERPRIM iER ASSEMBLY ASSEMBLY

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120.100.3Figure 10-6.Card Reader-Punch-Interpreter Unit RD-293/UYK-5(V).

188

Chapter 10INTRODUCTION TO DIGITAL COMPUTERS1IN WORM AT ION

'YIN DOW

CONTROLPANEL

CONTROLPANEL

Figure 10-7.Input/Output Keyboard Printer TT-515/UYK.

to operate and monitor the printer once paperand ribbon have been properly installed in theprinter mechanism.

UNIFORM AUTOMATIC DATAPROCESSING SYSTEM

The Uniform Automatic Data ProcessingSystem (UADPS) is a program designed toapply electronic data processing equipmentand techniques to the supply function at NavyStock Points. The Navy Stock Point providesa large variety of items for bulk and readyissue supply support to the operating forcesof the fleet and to shore based activities.

The UADPS system consists of InventoryControl Points, the Navai Supply Depot inRhode Island, and several supply centers. Thebasic control points are for navy ships parts,aviation supplies, and electronic supplies.

The UADPS centers use real time randomaccess computer operations to process incom-ing requisitions, receipt notices, and requestsfor information. Many incoming requests enterthe system from dockside input/output stations.

Upon receipt of a request, inventories areare automatically checked and warehouses arenotified of articles to be shipped, or whereneeded articles can be obtained. The system

189

120.100.4

also keeps accounting and inventory records,assembles and prints management reports, andpoints out trouble spots for immediate attention.

DATA PROCESSING SET AN/UYK-1

The AN/UYK-1 (not shown) is a generalpurpose, stored program computer set designedfor shipboard environment. The computercan be used with, but is not a part of, theNavy Tactical Data Systems, and with theoceangraphic and navigation systems. It com-putes and manipulates digital data at electronicspeeds, and stores data in its magnetic corememory. The computer controls, or can becontrolled by a variety of peripheral devicessuch as teletype machines, paper tape punches,and readers, magnetic tape transports, punchedcard readers, high speed printers, magneticdrums, and all components of NTDS. Thecomputer uses 30-bit words. Magnetic corememory may contain as many as 32,768 words.

Digital Data Computer CP-642( )/USQ-20(V)

The Naval Tactical Data System (NTDS)is an automatic data system for gatheringand processing data received from the ship's


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Figy.re 10-8.Data Processing Line Printer RO-302/UYK-5(V).

190

/91

120.100.6


CONSOLE

I'0 CHASSIS(AI-A3)

CONTROL ANDARITHMETIC

CHASSIS(A4-A6)

CONTROL ANDARITHMETIC

CHASSIS(A7A8)

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LOGICCHASSIS

MEMORYCHASSIS(A9A1I)

151.93Figure 10-9.Digital Data Computer CP-642( ) /USQ -20(V) showing major subassemblies.

sensors. It utilizes digital computers whichoperate in a real-time environment.

The NTDS computer CP-642( ) /USQ -20 (fig.10-9) is a general purpose, stored programcomputer. A list of instructions (program)is entered into the computer storage areaprior to executing the problem. The programdirects the computer in the execution of logicalsteps which ultimately produce a solution toa given problem. In addition to performingroutine tasks in connection with calculating andprocessing the information received in theCombat Information Center, such PS trackingand presenting intercept solutions, the com-puter can store a program to check out theNTDS equipments, or, when not needed forCIC use, it can be used to solve logisticproblems.

191

The CP-642( ) /USQ -20(V) is capable of rapidprocessing of large quantities of complex ciAta.The computer performs arithmetic and logicalfunctions by manipulating binary numbers inautomatic or manual modes of operation.

The major subassemblies of the computerare of modular design, having 13 roll-out typechassis; eight of which are logic chassis usedfor input/output, control, and arithmetic, andfive used for memory. Memory chassis areinterchangeable.

Connections between the chassis are madeby movable plug-racks (not shown) located onthe sides of the computer and jacks mountedon the sides of the chassis. Connections be-tween the compute: and external equipment isvia jacks (not shown) located on the top of thecomputer.

/9s-

SHIPBOARD ELECTRONIC EQUIPMENTS.

OPERATIONAL FEATURES

The major features of the computer include.

1. An internal, high-speed magnetic storagewith a cycle time of eight microseconds and arapacity of 32,768 30-bit words.

2. A repertoire of 62 instructions, most ofwhich provide for conditional program branches.

3. Average instruction execution time of 13microseconds.

4. A word length of 30 bits.5. Optional operation with 15-bit half words.6. Internally stored programs.7. Parallel, one's complement, subtractive

arithmetic.8. Single address instructions with provi-

sions for address modification.9. Internal 7-day real-time clock for ini-

tiating operations at desired times.10. Twelve input and twelve output channels

for rapid data exchanges with external equip-ment.

11. Two input and two output channels forintercomputer data transfer.

12. A 16-word auxiliary wired memory forstorage of critical instructions and constantsthat provide the facility for automatic reooveryin the event of program failure and for initialloading of programs.

Computer Console Set C-3413/USQ-20(V) isthe remote console associated with the com-puter (fig. 10-10). Although the computer itselfis basically an automatic machine, the consoleprovides facilities for manual intervention and

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sale

151.94Figure 10-10.Computer Console Set

C-3413/USQ-20(V).

control of the computer. The operator hasswitches on the console that are used to affectthe entire computer operation by injectingseveral modes of operation as, providing cer-tain jump or stop conditions, controlling com-puter operations, and governing speed of op-eration. There are also controls by which asingle stage can be set or an entire registercan be cleared.

192

/9'

CHAPTER 11

INTRODUCTION TO A SHIPBOARDWEAPONS CONTROL SYSTEM

This chapter will give you an overview of ashipboard gun and missile weapon system. Thetreatment is brief for several reasons. First,to describe the physical features and functioningof components of a weapon system in detailwould require several volumes. Second, securityrequires that we describe the functions ofcertain equipments in very general terms. Insome cases values of range, target height,target speed, and other characteristics of thetarget and equipment have been left out. Butthis chapter will provide you with the back-ground you will need to understand the manyweapons systems now in the fleet.

WEAPONS SYSTEM CONCEPT

The effective use of any weapon requiresthat a destructive device (usually containingan explosive) be delivered to a targetusuallya moving target. To deliver the weapon ac-curately, we must know the location of thetarget, as well as its velocity and directionof motion. Many targets now travel fasterthan sound, and must therefore be engagedat great distances. Against such targets, aweapon is most effective when it is used aspart of a weapon system. A weapon system isthe combination of a weapon (or multiple weap-ons) and the equipment used to bring theirdestructive power against an enemy.

A weapons system includes:

1. Units that detect, locate, and identifythe target.

2. Units that direct or aim a delivery unit.3. Units that deliver or initiate delivery of

the weapon to the target.4. Units that will destroy the target when

in contact with it or near it. These units areusually termed weapons.

193

DETECTING UNITS

The first steps in using a weapon system tosolve the fire control problem are to detect,locate, and identify the target. Initial contactwith a surface or air target may be visual,or it may be made by radar. It is difficult todetect a target visually at long range, or evenat short range when visibility is poor. For thatreason, targets are usually detected by searchradar. Search radars, as you know, keep alarge volume of space around your ship undercontinuous watch. The7 give the ship ac-curate information about the target's position,even when the target is hidden by fog or dark-ness. To determine a target's position we mustknow its range, its direction from the ship,and, for an air target, its elevation. Radargives all three of these coordinates. (Radarhas certain disadvantages, too. For example,it can be detected by an enemy at about 1.5times the range at which it can pick up anenemy target.)

Optical devices are used as a source ofinformation on slow-moving targets at rela-tively short range. They are useless againstmissiles or jet aircraft, which must be engagedwhile they are still beyond the range of opticalinstruments.

After we have detected and located a target,we must identify it. How can we identify a tar-get that may be several hundred miles from outship? The answer lies in a device called IFF(Identification, Friend or Foe). Radar alonecannot tell the difference between a friendly orenemy target. But the IFF equipment can chal-lenge an unidentified target, and determine fromthe answer whether the target is friendly. Theequipment consists of two major unitsthe chal-lenging unit which asks the question, friend orfoe, and the transponder which answers thequestion. IFF equipment is used in conjunctionwith search radar, and sometimes fire control

X97


radar. Briefly, this is how it works. To chal-lenge a target you press a switch attached tothe radar. The IFF transmitter will then sendout a pulse of low power radio energy towardthe target. If the target is friendly it will carrya transponder, which consists of a receiver anda transmitter. When the receiver picks up achallenge, it causes the transmitter to send outan answering pulse or pulses. The answer isusually a coded message. It is picked Alpby the challenging unit's receiver and sentto the indicator of the search radar.

CONTROL UNITS

Control units in a weapon system develop,compute, relay, and introduce data into a deliveryunit, a weapon, or both. They direct, control, orguide the weapon (destructive device) to thetarget, and cause it to function in the desiredway. These units form the heart of the wiaponsystem.

Types of Control Units

The devices that perform the control func-tions include: DATA TRANSMISSION SYSTEMSthat send target position information developedby the detecting units to the rest of the weaponsystem, and convey other data among thecomponents of the weapon system. Examplesare synchro, resolver, and potentiometer cir-cuits.

COMPUTER DEVICES are used co processthe input data from the detecting its andother sources, and put out the aiming andprogram instructions that cause the weape.to reach its target. Examples are range-keepei a and computers.

DISPLAY UNITS display information atvarious locations on the ship. These aregenerally electronic, electromechanical, oroptical devices.

DIRECTING DEVICES are those which, withthe aid of detecting devices, establish targetlo-cation. Directing devices can also functionto directly or indirectly control missile flight.Examples are gun and missile directors, andradar sets.

REFERENCE DEVICES are those such asstable elements, which establish referenceplanes and lines to stabilize lines of fire, linesof sight, and other references. These unitsusually are gyroscopically controlled.

DELIVERY UNITS

Broadly speaking, delivery units launch orproject destructive units toward the target.Examples are guns, missile and rocket launch-ers, torpedo tubes, and depth charge projectors.Don' t think of these device.. 'is weapons. Theterm WEAPON is properly applied to thedestructive unit that is launched or projected.Thus a guided missile launcher is not, strictlyspeaking, a weapon; the missile itself is theweapon.

To be effectively used against theirtargets, all weapons must either be aimed attheir targets or be programmed during flight;they may require both aiming and programming.Programming is the process of setting automaticequipment to perform operations in a predeter-mined step-by-step manner. Aiming and pro-gramming are done at or before the time oflaunching, either by or through the deliverydevice. This function is characteristic of alldelivery devices, even the simplest. Aiming thedestructive device (weapon) at the target maybe done simply by positioning the delivery device(a gun barrel or launcher guide arm, for ex-ample). Or it may be done without aiming thedelivery device, by placing program instructionsin the weapon. Some missiles are programmedto start searching for the target after thelaunching phase is over. Examples of otherprogrammed functions that could be performedin the weapon are ignition of propulsion unitsand arming of the warhead after a designatednumber of seconds in flight.

Types of Delivery Devices

Two representative types of delivery devicesare guns and missile launchers.

GUNS provide all the propulsion energy totheir projectiles, and direct (aim) the pro-jectiles by positioning the gun barrels.

MISSILE LAUNCHERS retain and positionmissiles during the initial part of the launchingphase, and, by means of attachments to thelauncher, feed steering, vertical reference,and program information into the missile up tothe instant of launch.

DESTRUCTIVE UNIT

The end purpose of detection units, deliveryunits, and control units is to cause the destruc-tion unit to intercept or pass near the target.

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Chapter 11INTRODUCTION TO A SHIPBOARD WEAPONS CONTROL SYSTEM

It is then the function of the destruction unit todestroy or inflict maximum damage on thetarget.

Basic Weapon Components

All weapons have these components:1. A CONTAINER or BODY which houses

the internal components. The body may havesuch other functions as piercing armor, break-ing up into high velocity fragments when theweapon or projectile explodes, or improvingthe weapon's ballistic characteristics by meansof fins or streamlining.

2. A DETONATING DEVICE (called a fuze,an exploder, a detonator, etc.) which initiatesexplosion at the proper time, and includessafety devices to prevent premature explosion.

3. A PAYLOAD which is the "reason forbeing" of the weapon or projectile. The payloadusually consists of high explosive or nuclearmaterial.

Weapons of some types have their own pro-pulsion systems. The outstanding examples areguided missiles, torpedoes, and rockets. Withthe exception of rockets, weapons that have apropulsion system also contain guidance andcontrol systems.

REPRESENTATIVE WEAPONS SYSTEM

Figure 11-1 depicts the major componentsof a representative weapons system. The equip-ments making up each of the four categoriesof functional components are enclosed inseparate blocks. We will introduce and discussthe four groups of equipments in the orderin which they operate to solve the fire controlproblem.

TARGET DETECTION, LOCATION, ANDIDENTIFICATION

The first contact with an airborne target isusually made by air search radar. These radarsare designed to keep a large aerial volume undernearly continuous observation. Jet aircrafttravel at high speed, and may launch guidedmissiles against our ships from a great dis-tance. This requires that our radar search becarried out to long range. To cover the neces-sary area, search radar uses a wide beam. Inaddition, most search radar antennas rotate asthey search. Targets show up on the radar's

195

target display indicators as alternately fadingand brightening spots. It is difficult to determinetarget range, course, and speed from thesespots. All of these factors limit the accuracywith which search radar can provide informationabout target position. For target informationof the required accuracy, we must depend onfire control radars.

After the search radar has detected a targetand determined its approximate location, thenext step in the development of the fire controlproblem is to identify the target. The problemof recognizing and identifying a friend or foeis as old as warfare. Passwords, flag hoistsignals, and even the uniforms we wear areidentification devices that have been developedthrough the years.

In modern warfare the identificationproblemis urgent. Radar systems present targets in theform of spots or spikes (called echoes) on aradar screen; but friendly and enemy targetslook alike on the screen. Furthermore, highspeed planes and guided missiles give us verylittle time to slove this problem. And whenfriendly fighter aircraft pursue enemy planesto within weapon range of our ships, the iden-tification problem is acute.

As we said before, IFF is the device we useto determine whether the target is a friend orfoe. Although search radar and IFF are notpart of the fire control system, they are com-ponents of your ship's weapons system.

Before we leave the subject of the majorequipments that fall in the category of detection,location, and identification units, we want toemphasize that solution of the fundamental firecontrol problem begins with detection of atarget. The next step is to locate it. And thefinal step in this initial phase is to identify itas friend or foe. These three steps combine toform the first phase (Phase 1) in the functioningof a weapon system. At this point you shouldbegin to see that you must think in terms ofa complete weapons system in order to under-stand the functioning of each individual com-ponent in the system.

Now let' s consider the CONTROL UNITSin group (2) (fig 11-1).

/9'9

THE WEAPON CONTROL SYSTEM

Once the air search radar detects androughly locates the target, and the IFF equip-ment has determined whether it is a friend orfoe, the target information from these sources

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is sent to the equipments that we have calledcontrol units. These units include fire controlradars, directors, computers, weapon directionequipment, stable elements, and many othermechanical, electrical, and electronic instru-ments.

Traditionally, the systems of equipmentusedfor the control of a particular battery of guns,torpedoes, or other weapons, have been knownas fire control systems. But the complexity ofguided missiles has required the introductionof new fire control instruments, and new termsto describe them. In the following paragraphswe will define some of these terms.

All the units that are enclosed by the solidline in block (2) of figure 11-1 form a WEAPONCONTROL SYSTEM. A weapon control systemis defined as a group of interconnected andinterrelated equipments that are used to controlthe delivery of effective fire on selected targets.The system is composed of a WEAPON DIREC-TION SYSTEM and one or more FIRE CONTROLSYSTEMS.

Weapon Direction System

A WEAPONS SYSTEM begins to function assoon as a target is detected. However, a FIRECONTROL SYSTEM begins its functioning bydetermining the future target position with allpossible precision, so that a line of fire can beestablished. Before a fire control system canestablish a line of fire, certain preliminaryprocesses must take place within the weaponsystem. These processes are:

1. Detection of a target by search radar orother devices

2. Identification of the target by IFF orother devices

3. Evaluation of the target4. Designation of the target to a fire control

system5. Acquisition of the target by a fire control

system

The target position and identification infor-mation obtained during the first two processesis sent to the CIC (Combat Information Center)and to the WCS (Weapon Control Station). Thesetwo organizations of equipment and personnelmay be in the same compartment or in separatelocations. Here, we will consider them to be inthe same compartment. This compartment alsocontains the units that make up part of the

197

Weapon Dire(' ion System (WDS). This partic-ular group of equipments is known collectivelyas WEAPON DIRECTION EQUIPKV.NT (WDE),The WDE, and units that support its functio::.make up the Weapon Direction System of aship.

The purpose of the WDS is to perform thosefunctions that are required during three phasesof a tactical situation. During the first phase,the equipment provides electronic means forthe display of targets detectedby search radars,and it provides devices for selecting and initiallytracking the targets that show up on the dis-plays. These displays are similar to the PPIs(Pi. Position Indicator). Targets show upas bright pips or dots on the face of the scope.

As the tactical situation develops, and thetargets get closer, the system provides meansfor evaluating the situation and assigning a firecontrol system or systems to acquire and trackdesignated targets. This is the second phase inthe tactical situation. The third and last phaserequires that weapons be assigned by the WDSto the fire control system that is tracking thetarget. Before weapons are assigned, the tac-tical situation must be reevaluated.

So far in this discussion, we have introducedthree new terms: evaluation, designation, andacquisition.

Target EVALUATION is concerned withthese questions:

1. What does the target intend to do? Is itgoing to pass close to the ship for observing,or is it going to launch an attack?

2. How threatening is the target to the ship'ssafety? If its obvious intent is to attack,how much time does the ship have to launch acounterattack? What weapons should the shipuse to repulse the target?

3. What kind of attack is the target capableof launching ? If the target carries missiles,the ship must launch weapons that will reachthe target before it can launch its missiles.

There are other factors involved in evaluat-ing a tactical situation, but these sample ques-tions should give you some idea of what theterm "evaluate" means. More examples willturn up later in this chapter.

The equipment in the weapon direction sys-tem presents a complete visual picture of thetactical situation. It displays all the targetsthat have been detected by the search radars.Each target must be evaluated with respect tothe overall defense picture. Decisions aremade to bring the ship's weapons to bear on


the most threatening targets. These selectedtargets must be assigned to the appropriatefire control systems. The assignme.it processincludes two functionsdesignation and ac-quisition.

DESIGNATION is the step taken to assignthe tracking element (director' s radar or opticalequipment) of a fire control system to a par-ticular target. On the basis target evaluationand the availability of fire control systems(some of which may be disabled, or busy withother targets), a decision is made to assign afire control system to the target. This isusually done by pressing a button to activatecircuitry that transmits target position infor-mation from the weapon direction system to theantenna positioning circuits of a radar set, orthe power drives of a director. These unitsautomatically move the radar antenna to thedesignated position. If the designation is in-accurate, the director must search for thetarget.

The searching process may last for a secondor longer, depending on the accuracy of thedesignation information and other factors. Oncethe director has found the target and starts totrack, it can be said that it has acquired thetarget.

ACQUISITION by the tracking device is theprocess of accepting a designation, acquiringthe target, and starting to track it. A target isacquired when the radar has "gated" it, or thecrosshairs in the director sights are on it.

In the preceding discussion we indicated thatthe W DS was further subdivided into the weaponsdirection equipment, and other equipment relatedto the overall function of the weapons directionsystem. In the following articles we shall takeup the units that make up the weapons directionsystem.

REPRESENTATIVE WEAPONSDIRECTION EQUIPMENT

The weapon direction equipment (WDE) in-cludes displays and controls for the evaluation oftarget data, and for the selection and engage-ment of targets so as to ensure the most effec-tive use of the gun and missile batteries. Atypical WDE conists of one or more TARGETSELECTION and TRACKING consoles, a DI-RECTOR ASSIGNMENT console, a WEAPONassignment console, and the necessary cabi-nets to house power supplies and computerunits.

198

Target Selection and Tracking Console

Figure 11-2 shows a representative targetselection and tracking console. Regardless ofthe mark or modification, they all have the samegeneral function. The console is used for

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.2 c2

Chapter 11INTRODUCTION TO A SHIPBOAR*3 WEAPONS CONTROL SYSTEM

selecting and tracking targets detected by searchradars. The principal indicator is a PPIthat displays the true bearing and slant rangeof targets picked up by a selected search radar.The primary controls are a pantograph arm forselecting and tracking targets, and pushLuttonsfor assigning targets to tracking channels.Other controls are provided for selecting vari-ous search radars for the PPI display, forse'ecting the range scale, and for insertingtarget position and height data into the trackingchannels.

Targets are displayed on the scope as radarvideo (pips). To select a target and assign it toa tracking channel, you position the pantographsighting ring over the target pip and then pressa channel button. Pressing the button gainselectrical access to that channel, and simul-taneously causes an identifying channel letterto appear next to the target pip. Successivecorrections of pantograph position develop tar-get course and speed in the tracking channels.

Director Assignment Console

The primary purpose of this console is topre side the information display and controlsrequired to assign fire control systems to thetargets being tracked by the target selectionand tracking console operator, when it is deter-mined that a specific target or targets shouldbe engaged. Figure 11-3 shows the panel layoutof the director assignment console for ourbasic WDE. Two plots are provided on the faceof the consolea plan plot on the left, and amultipurpose plot on the right.

The plan plot shows three range rings, andindicates true bearing with north at the top.Each target being tracked by the target selec-tion and tracking console appears on the displayas a letter, corresponding to the trackingchannel from which it originates. The figureshows that tracking channels A, B, and C aretracking three separate targets. The straightline associated with target A indicates thecourse of this target. The number 1 indicatesthe position of the director in the fire controlsystem. If the weapon control syptem had morethan one fire control system, these additicrialsystems would have associated numerals. Aship's heading marker, and radial clearancelines on either side of it, are presented elec-tronically and rotate when the ship changescourse. The sector between the two clearancelines indicates the region into which may

199

not launch missiles because of danger of strik-ing the ship' s superstructure.

The multipurpose plot is used primarily formaking time comparisons. These comparisonshelp the operator to decide whiA of severaltargets to designate to a director, and to planthe future handling of targets that cannot beassigned immediately. Once the director ac-quires the target and begins to track it, the firecontrol system is busy. During this time theoperator, with the aid of the information dis-played on the plot, can decide which target isnext in line for assignment.

The multipurpose plot also indicates thespeed and height of targets in the trackingchannels. As you can see in figure 11-3, it isdivided into three vertical lineseach linerepresenting a tracking channel. All changesin indications take place vertically, and you canread the values indicated as you would read athermometer.

The vertical lines show, for each target,the time within which the radar set must beassigned and a ni:ssile fired in order to inter-cept the target before it ,can reach its EstimatedWeapon Release Range (EWRR). The EWRRwill vary depending on the type of payload theenemy is carrying and on how accurate you guesswhat the payload is. For example, if you guessthat the target's payload is an air-to-surfacebeam-rider missile, the EWRR might be on I' :order of 25,000 yards. At the left of the pie,you can read how much time you have to assignthe target, solve the problem, and load and firea missile salvo, to intercept the target beforeit can release its missiles. This points upthe need for quick evaluation. In conjunctionwith the plan plot, the multipurpose plot providesthe necessary information to speed up thisprocess. It relieves the operator of the necessityof remembering how much average time eachcomponent in the weapon system requires toperform its function under varying conditions.

The scale used to measure assignment timeis also used with the height line. The heightline is a short horizontal bar which moves upand down the vertical channel line as targetaltitude changes (fig 11-3). In this case thenumber (not shown in the figure) representsthousands of feet. To the right of the displayis a target speed scale (marked knots) whichis used in conjunction with the speed circle.The speed circle rides up and down to indicatetarget speed.

SHIPBOARD ELECTRONIC EQUIPMLNTS

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AGAIN /

SECONDS ORTHOUSFEET

CHANNELTIMELINE

I KILL I INorwcs 04.)

5 `,_ - -

MULTIPURPOSEPLOT

TARGETSPEEDKNOTS

B

Figure 11-3.Director assignment console display.

The long horizontal line shown in this plotrepresents busy time for the fire control sys-tem. When the system is not acquiring ortracking, the time line and director symbolnumber rest at zero time. But when the directoris assigned a target, the time line and symbolmove up to indicate the time during which thedirector will be busy with that target; theyslowly move down as time elapses. After amissile salvo is launched, the line and symbolcontinue to move downward until they reachzero. The missile should have intercepted thetarget, and the fire control system is free tobe assigned a new target.

Above the two display plots is a field oflamps relating to th,1 gun and missile firecontrol system. The lamp with the numeral 1in it is called the BUSY lamp. (If our weaponcontrol system had more than one fire controlsystem, each of them would be represented bya different lamp and number.) The BUSY lamp

TARGETHEIGHTLINE

SPEED CIRCLE

DIRECTORSYMBOLAND TIMELINE

DESIGNATETO FCS

I I I

12.43

is lighted whenever the director is assigned thetarget. The IND lamp is lighted when thedirector is operating INDependently of theweapon direction equipment. The TRACK lampindicates that the assigned target is gated andis being tracked. The KILL lamp lights when atarget has been destroyed. The observation ofthe kill is usually visual.

The FCS NON-OP lamp indicates that somepart of the fire control systems is not in opera-tion. When missiles are launched, the SALVO-IN-FLIGHT lamp lights. If another salvo isordered to be fired, the FIRE-AGAIN lamplights to indicate that this order has been sentto the weapon assignment console, but that thesalvo has not yet been fired.

The pushbuttons at the left labelled DESIG-NATE FROM, and the pushbutton at the rightlabelled DESIGNATE TO FCS, are used inmaking assignments of a director to one of thethree tracking channels. The operator makes

zoo

0 I/


the assignments by simultaneously pressingthe selected "designate from" button and the"designate to FSC" button until both lightsfunction. This process connects the directorto the selected tracking channel and slewsthe director automatically onto the target.At this time the repeat-back symbol, (numeralrepresenting the FCS), moves until it issuperimposed on the track channel symbol.This indicates to the director assignmentconsole operator that the system is trackingthe proper target.

Weapon Assignment Console

The Weapon Assignment Console is theconnecting link between the fire control systemand the weapon launcher. It displays datafrom the fire control system, giving thetarget's present and predicted interceptpositions, and information from the computerindicating whether or not missile interceptis possible. It also has a summary displayof launcher information.

The missile firing key is located on theweapon assignment console. Decision of whetheror not to fire is made from this station.

The console has a PPI display showinga horizontal plot and true bearing, withown ship's position in the center. Aroundthis plot is a fixed bearing ring. Radiallines from the center to the edge of theplot, generated electronically, indicatelauncher unclear areas caused by ship'sheading. These lines' rotate with changesin ship's heading. This display is similarto the plan plot of the director assignmentconsole.

The other indications on the cathode-raytube display appear only while the fire controlsystem is tracking a target. These indicationsare:

1. An "X" indicating target present gosition2. A small circle indicating target future

position at the predicted point of intercept3. A large circle about the center, which

indicates the maximum range the missilecan reach at the target's predicted altitudeat intercept

4. A thermometer-type display at the left-hand edge of the plot, giving the target'spredicted altitude at intercept (H)

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REPRESENTATIVE MISSILE FIRECONTROL SYSTEM

In this section we will discuss the equip-ments that make up the fire control systemof a typical guided missile ship. Look againat figure 11-1. We have assumed that thefire control system shown is capable ofcontrolling gun and missile batteries at thesame time. This is a valid assumption,because there are systems with this capabilityin the fleet. But for now we will separatethe capabilities and consider the fire controlsystem a missile system. The fire controlcomputer calculates the prediction angle anduses it as an offset to the line of sight toestablish the line of fire and to produce weaponorders. The orders are transmitted to themissile launcher to position it in the lineof fire.

Thus the primary basic functions of thefire control system are: to acquire and tracktargets; to develop launcher and missileorders; to guide missiles to the target; and insome instances to detonate the missile'swarhead.

Secondary functions of the system are toprovide target information such as targetspeed, target course, range to the target,and system and weapon status information tothe display units of the weapon directionsystem. This information is used to evaluatethe tactical situation and to aid in the firecontrol system and weapon assignment.

The Director or Radar Set

The director or radar set can searchfor, detect, acquire, and track a target;and it can "capture" and guide a missile.Let's stop and consider the terms "director"and "radar set." A director may containa radar and/or optics for tracking and ranging,and it is usually manned. A missile directorhas no optical tracking device or rangefinderbut relies on its radar set for tracking.It is not manned in the sense that a manis located inside the antenna supporting struc-ture. True, there is an operator in theradar control room; but his primary functionis to monitor the equipment. In the restof this discussion we will use the term "radarset," rather than director, because that name ismore descriptive of the function of a missiledirector.


The radar set described here, and il-lustrated in figure 11-1, is an automatictarget tracking and missile guidance radar.It normally receives target designation signalsfrom the weapon direction equipment, via thefire control computer. The designation signalsposition the radar set at the designated range,bearing, and elevation. If the radar set doesnot acquire the target immediately the firecontrol computer originates a search programfor the radar set to seek out the target.If the ship has more than one fire controlsystem, designation between systems ispossible. Designation from another fire controlsystem, called "Inter-director Designation"or "IDD", is accurate and a search programis not needed. Therefore IDD does not goto the computer but through the fire controlswitchboard to the radar set.

When the radar set acquires the targetin range, bearing, and elevation the radarset locks on the target and starts to trackit. Tracking circuits within the radar setautomatically keep its tracking beam on thetarget. Target position is continuously trans-mitted to the computer. The computer andthe radar set working together solve for thetarget's rate of movement about the ship bycalculations based on the line of sightmovements.

The radar not only tracks the target, butalso transmits radar beams to control themissile and guide it to the target. In thecase of the beam-rider missile the radar setwill transmit simultaneously, on a commonnutation axis, three distinct beamsthetracking, capture, and guidance beams. Anarrow tracking beam first acquires andtracks the target. The wideangle beamcapturesthe missile after launch, and holds it untilit enters the narrow guidance beam that guidesit to the target.

Where a semiactive homing missile is used,the radar set will transmit simultaneously, on acommon nutation axis, a tracking beam, and anilluminating beam. After the missile is launchedit will lock on to the illuminating radar's energyreflected from the target, and home on it. If amissile whose guidance is a combination ofbeam-rider and semiactive homing is launched,the radar set will transmit a tracking beam anda beam-riding guidance beam and later switch onan illumination beam.

The radar set consists of two major groupsof equipment: an antenna group, and a power

202

control group. The antenna group, whichis located abovedeck, consists of a pedestalupon which is mounted the antenna and thenecessary electrical and mechanical componentsrequired to stabilize and position the antenna.Housed inside the mechanical structure ofthe antenna group are the transmitting,receiving, and associated microwave circuits.Here, too, are located the gyroscopes thatspace-stabilize the antenna, and thus the radarbeams, to compensate for the roll and pitchof the ship.

The control and power equipment groupis located belowdeck in a compartment usuallycalled the radar room. This room containsthe radar consoles used to operate, monitor,and control the radar set. Also located inthe radar room are the cabinets containingthe power supplies that provide the operatingvoltages for the various units in the radarset.

Representative Missile Computer

The representative guided missile firecontrol computer described here is an electro-mechanical type designed to operate auto-matically. No operating personnel are needed.It is located in the ship's plotting room, andis used with the radar set described previously.

The computer has three basic ways ofoperating. It can operate when designation isdesired; then, after the radar set has acquiredthe designated target, the computer aids theradar set in tracking it As soon as the missileshave destroyed the target, the computer shiftsto the air-ready method of operation. Thesedifferent methods of operating are called modes.The various modes of computer operation canbe briefly described as follows.

AIR-READY MODE.In this mode the com-puter is energized, but is receiving no informa-tion. It generates orders only to put theradar set and launcher in predeterminedair-ready positions. For example, the air-ready position of the radar set may be atzero° of train and 45° of elevation; the launcherair-ready position may be at 180° of trainand zero° of elevation.

DESIGNATION MODE.The computer goesinto this mode of operation when it receivesa "director assigned" signal from the directorassignment console of the WDE. The computer

BOG

Chapter 11-1NTRODUCTION TO A SHIPBOARD WEAPONS CONTROL SYSTEM

directs the radar set to the designated targetposition so that the radar line of sight willpoint at the target. It also sends a searchprogram to the radar set. The search programcauses the radar beams to move in a presetpattern about the designated target position.The radar searches for the target, and whenthe target is gated the computer automaticallygoes into the track mode of operation.

TRACK MODE.When the radar setacquires the target in range, bearing, andelevation, the track mode starts. The radarset then transmits an on-target signal to thecomputer. The computer sends signals tothe radar set that cause it to drive at a ratethat will keep it locked on the target. Thecomputer determines the proper lead anglesfor the launcher, and transmits these quantitiesin the form of electrical signals. Thesesignals drive the launcher to the proper aimingposition.

Before the missiles are launched, thecomputer determines and transmits to themissiles quantities that move the missile gyrosto their proper positions. The computer alsotransmits tactical data such as present targetposition future target position, and missiletime to target intercept (time of flight) tothe various display consoles of the WDE.

DELIVERY UNITS IN A REPRESENTATIVEWEAPONS SYSTEM

The delivery units of a representative weaponsystem are the gun and the missile launcher.In this section we will discuss only the missilelauncher and the equipments associated withit.

Guided Missile Launching System

The guided missile launcher shown in figure11-4 is part of a group of equipments thatare known collectively as a Guided MissileLaunching System. A guided missile launchingsystem has three major components:

1. Guided missile launcher2. Guided missile launcher feeder3. Guided missile launching system control

The primary purpose of a guided missilelaunching system is to stow missiles untilneeded and then supply them to a launcher

for firing. Its secondary function t to removeunfired missiles from the launcher and returnthem to the missile stowage area.

GUIDED MISSILE LAUNCHER.Except forPolaris, all Navy missiles that are launchedfrom ships use zero-length launchers. Thistype has one or two, usually two, launcherarms (or rails). The launcher shown in figure11-4 is the dual-rail type. It receives andsecures two complete missilesone on eachlauncher arm. The launcher automaticallytrains and elevates in response to synchrosignals (missile launcher orders) from thefire control computer. Through various deviceson the launcher arms, the missiles receivewarmup power before launch. Warmup poweris used to bring the missile gyros up to speed,and to warm up the vacuum tubes, withouttaking power from the missile power supplies.Preflight information is also supplied to theweapon through contactors in the launcherarms, and the firing circuit is connectedthrough the launcher to the missile's internalfiring circuitry. The launcher can automatic allyreturn to a predetermined fixed position inwhich a new missile can be loaded on thelauncher arm, or an unfired missile can bereturned to stowage.

203

,4O7

LAUNCHER FEEDER.The purpose of thisgroup of equipments (fig. 11-4) is to stowguided missiles and their boosters in magazines,to remove them from the magazines, and toload them on the launcher arms. There areseveral types of feeders, but they all havethese two purposes.

LAUNCHING SYSTEM CONTROL.Thisequipment group includes the panels used tooperate the missile launching system. Thepower panels contain circuit breakers,overload relays, and other electrical componentsrequired by the various power drives thatcontrol the movement of the launcher, rammer,and ready-service ring. Other panels containoperating controls that are used to start thesystem and control its operation. Thesepanels normally respond to orders from theWDE. For example, the WDE may send anorder to ALERT the missile launching system.An ALERT light on a panel flashes, indicatingto the operator that WDE wants the missilelaunching system's equipment put into operation.Several of the orders transmitted from the


DUD JETTISONINGCONTROL PANEL

BLAST DOOR

VIEW P RT

LAUNCHER

,

LOADER

LAUNCHING SYSTEMCONTROL PANEL

"B" ASSEMBLERCONTROL PANEL

DUD EJECTOR-414,

LAUNCHER TESTCONTROL PANEL

POWER PANEL

READY SERVICE RING

BOOSTER FINSTOWAGE RACKS (ASSEMBLER)

MAGAZINEDOOR

PERSONNF,. GUARD RAIL

MAGAZINE

FORWARD SUPPORT

Figure 11-4.Representative Terrier missile launching system.

WDE to the missile launching system are ofinterest to the FT.

TYPES OF ORDERS. The MISSILE SELECTorder is transmitted from the WDE to thelaunching system to indicate the type of missileto be loaded on the launcher. There areseveral types of Terrier missiles. All ofthese types may be loaded together in a singlemagazine. This is called mixed loading. Whenthe launching system has selected the typeof missiles called for by the WDE, it sendsback a signal indicating that the order hasbeen carried out.

The LOAD ORDER tells the launching sys-tem to start loading a missile or missiles. Aload order may be "continuous," "single," or

204

12.44

"hold." A "continuous" order causes missilesto be continuously supplied to the launcher. Thisoperation is similar to "rapid or continuousfire" in conventional gunnery. The "single"order causes one missile per arm to be loadedon the launcher. The "hold" order holdsthe launching system in a ready-to-loadcondition.

When the launching system receives theUNLOAD ORDER, it unloads any missilesthat may be left on the launcher arms.

The INTENT-TO-LAUNCH (ITL) is similarto the conventional "commence fire" orderin one respectit is transmitted by closinga firing key. But, while the gun firing circuitis completed almost instantly when the keyis closed, there is a slight delay before a

.2of....10111

Chapter 11 INTRODUCTION TO A SHIPBOARD WEAPONS CONTROL SYSTEM

missile firing circuit is completed. Thisdelay is necessary to establish certain operatingconditions in the missile, and other equipmentsin the weapon system. Before the missilecan be fired, it must indicate that it is readyto be launched. This indication, "missile-ready-to-fire," is sent through the launchingsystem control circuits back to the WDE.Almost every piece of equipment in the weaponsystem affects the operation of the firingcircuit, either directly or indirectly.

DESTRUCTION UNITS IN A TYPICALWEAPONS SYSTEM

As we mentioned earlier 'n this chapter,our typical weapons system is designed tocontrol two weapons, the gun (projectile) anda guided missile. Both of these weapons havealready been discussed; therefore these unitswill not be cover here.

GUNFIRE CONTROL SYSTEM

Here we will compare the functions ofthe major units in a GFCS with those in amissile fire control system, (MFCS). Sincethe same basic elements are present in themissile and the gun fire control problem,both types of systems will have the samemajor units and the primary function of theunits will be the same. This is clearly il-lustrated by the fact that the weapon controlsystem we just discussed can control bothmissile and gun batteries.

Variations between the problems and thefunctions of the major units are the resultof the differences between the guided missileand the gun projectile. The missile is guidedduring its flight; hence its control problemcontinues after launch. On the other hand,once a gun projectile is fired the gun controlproblem for that round is completed. Themissile, having a longer range and higheraltitude capability, extends the limits of itsproblem beyond those of the gun problem; butthis fact does not change the basic problem.

We will follow target information througha gun fire control system, starting with theinitial detection of a target by the searchradar. At each major unit we will pointout the principal differences between it andits counterpart in a missile system.

205

TARGET DESIGNATION SYSTEM

The target designation system (TDS) is theconnecting link between the search radar andthe GFCS. The function of the search radaris the same as it is on a missile ship. Due tothe limitations of the guns, particularly theirrange limitation, the designation equipment fora gun battery is simpler than the WDE for amissile battery. A single console with a PPIpresentation is used to evaluate, track, assign,and designate targets to the GFCSs.

Guns are assigned to a GFCS by a prear-ranged ship's doctrine. Thus when the TDSassigns a GFCS to a target, the assignmentincludes the guns. Normal procedure is tocommence fire as soon as the target is withineffective gun range. The firing circuit is con-trolled within the GFCS. Thus when the directorhas acquired the target, the TDS has completedits job with respect to this target and GFCS.DESIGNATION TRANSMITTER, an optical tar-get detector, can transmit target designationdirectly to the GFCS without going through theTDS.

If more than one FCS is installed, designa-tion can normally be made between the systems.As you know, this method of target designationis called IDD (interdirector designation).

GUN DIRECTOR AND COMPUTER

Gun directors are manned, and normallyhave both optical and radar equipment to detect.locate, and track a target. The director crewcan readily shift from optical to radar tracking.or vice versa. The radar transmits a singly?target-tracking beam. Another function of gundirectors is to furnish a centralized control sta-tion and a remote firing station for the battery.

There is little to distinguish between gunand missile computers. Due to the nature oftoday's air targets, Anti-aircraft (AA) com-puters are almost fully automatic, with littleor no provision for manual operation. Guncomputer outputs of train, elevation, fuze, andparallax orders drive the gun to the predictedposition of the line of fire. The entire problemof locating the correct line of fire is solvedbefore the projectile is fired.

WEAPONS SYSTEM FUNCTIONING

To provide a brief review of what you havestudied so far in this chapter, we list the


principal steps or phases a typical weaponssystem goes through to accomplish its mission.The mission, of course, is to destroy the enemyor a practice target. The principal steps, inchronological order, are:

1. TARGET DETECTION. Search radarsdetect targets at long ranges, to allow timefor the weapons system to go into action andcomplete its function.

2. TARGET SELECTION. The weapons di-rection system selects the targets that appearhostile, and that require missile and/or pro-jectile interception, and inserts them into track-ing channels. Target selection and tracking isperformed by personnel assigned to the targetselection and tracking consolea unit of theweapon direction equipment.

3. SEARCH RADAR TARGET TRACKING.The tracking channels (computing circuits) con-tinuously track selected search radar targetsto generate target rate of movement. This dataappears as a symbol (letter) on the face of alarge cathode-ray tube (scope). When the track-ing channel has computed the correct targetcourse, speed, and rate, the symbol on thescope will remain superimposed on the targetecho supplied by the search radar. This com-puted target position and rate data is used forevaluation of the tactical situation presentedto the ship, and for transmission to other unitsin the WDSespecially the director assignmentconsole. Each target that is being tracked isassigned a different symbol to prevent confusion.

4. EVALUATION. The weapon system eval-uates the threat of various targets, decideswhich should be engaged by guns and which bymissiles, and decides which targets should begiven priority. The evaluation is performedby personnel, but they are aided in this processby the displayed information on the variouscon-soles in the WDE and CIC.

5. DIRECTOR ASSIGNMENT. A radar setis assigned to the target having the highestpriority. When a radar set is assigned, thisimplies that a fire control system has beenincluded in the assignment.

6. ACQUISITION. The assigned radar set(fire control system) gets on the target.

7. TRACKING. The fire control radartracks the target to provide precise targetposition and rate data. The computer associatedwith the tracking radar operates on the datafrom the radar set to provide the solution tothe fire control problem. The computer answers

206

are supplied to the guns and launcher assynchro signals to position these units in trainand elevation.

8. REEVALUATION AND WEAPON AS-SIGNMENT. The target that is engaged by thefire control system is reevaluated with reEpectto the tactical situation (this may have changed),availability of the launcher or gun, and therange limitations of the weapons.

9. LOADING. Missiles are loaded on thelauncher, and the guns are prepared for firing.

10. LAUNCHING AND FIRING. The missilesare launched at the proper time and in theproper direction. The guns are loaded and fired.

11. MISSILE GUIDANCE. The fire controlradar guides each missile to the target beingtracked. Gun projectiles, .of course, receiveno guidance.

12. TERMINAL PHASE. When a missile orprojectile approaches to within lethal range ofthe target, a VT (variable type) or other typefuse detonates its destructive charges. This isthe "moment of truth" for the weapons system.

SUMMARY

A weapons control system consists of acombination of a weapon (or multiple weapons)and the equipment used to bring their destruc-tive power against an enemy. The system in-cludes:

1. Units that detect, locate, and identifythe target.

a. Search radarsb. Optical target designation transmitterc. IFF radar

2. Units that direct or aim a delivery unit.a. Gun and guided missile radar and

directors.b. Computer devices (rangekeepers and

computers)c. Display units (electronic, electro-

mechanical, or optical devices)d. Reference devices (stable elements)

to establish reference planes andlines to stabilize lines of fire andlines of sight

3. Units that deliver or initiate delivery ofthe weapon to the target.

a. Gunsb. Missile launchers

4. Units that will destroy the target whenin contact with it or near it.

a. Shellsb. Missiles

CHAPTER 12

MISCELLANEOUS FACILITIES

Although many of the equipments discussedin this chapter operate on the radio, radar,or sonar principle, their application is sospecialized that they are dealt with more ap-propriately as miscellaneous facilities, insteadof as radio, radar, or sonar equipments. Forthis reason, they were not included in pre-ceding equipment chapters.

RADIO DIRECTION FINDERS

The Radio Direction Finder (RFD) is in-stalled aboard most ships for use in locatingpersonnel afloat in liferafts or lifeboats equippedwith radio transmitters. It also is used toobtain bearings on intercepted radio and radarsignals of both known and unknown origin.

Essentially, the radio direction finder is asensitive receiver connected to a directionalantenna. Early models utilized a loop antennathat was rotated manually to the position ofstrongest signal reception. Bearing of thesignal was read from an indicating device con-sisting of a pointer and an azimuth scale.Modern RDFs have antennas that are rotatedat a constant speed by a motor. Bearing in-formation is indicated on the face of a cathode-ray tube.

Range data cannot be obtained by taking asingle bearing with an RDF. Usually, severalbearings are taken either as rapidly as possibleon several radio beacons or radio stations ofknown geographical location, or on a singlebeacon or station of known location, allowingfrom 10- to 30-minute intervals between bear-ings. Plotting these bearings gives a fix thatis more or less accurate, depending on theaccuracy of the bearings.

Currently, three different models of radiodirection finders are installed on ships in theactive fleet. They are models AN/URD-2( ),AN/URD-4( ), and AN/SRD-7( ). A combination

MF/HF radio direction finder, the AN/SRD-7( ),is installed mostly on submarines.

Shipboard installations of the AN/URD-4( )direction finder set (fig. 12 -1) consist of anantenna, a receiver/power supply unit, an azi-muth indicator, mid a signal data converter(not shcwn). The set provides visual (andsometimes aural) direction-finding informationfrom radio signals in the frequency range of225.0 to 399.9 MHz. For surface to surfaceoperation, the range of tne equipment is ap-proximately 20 miles; for surface to air, ap-proximately 90 to 125 miles. Bearing accuracyis plus or minus 5°.

Tuning controls for the receiver are locatedon the front panel of the azimuth indicator. Bysetting the digit selector switches to the de-sired frequency, the receiver can be tuned toany one of 1750 frequencies, spaced 0.1 MHzapart. To facilitate rapid tuning, any 20 ofthe 1750 available frequencies may be preseton the digit selector switches. Then, the pre-set frequencies are selected by means of asingle channel selector switch. For conveniencein servicing the equipment, or for emergencyoperation, digit selector switches also are pro-vided on the front panel of the receivers.

Visual information appears on the face ofa cathode-ray tube in the azimuth indicator.Around the perimeter of the scope is a compassscale from which is read the signal bearing.When no signal is present, the pattern on thescope is a circle. When a signal is present,this cirr resolved into a propeller-shapedpattern axis lies along a line indicatingthe signa. rce direction and a point 180°displaced . ... the direction or signal origin.To eliminate this ambiguity, it is necessary tocause a further change in the shape of thepattern. Placing the calibrate-sense switch inits sense position causes the propeller-shapedpattern to become a V-shaped pattern, the apexof which indicates the signal bearing.

207


VERTICAL CONTROL

MOTOR SWITCH

ANTENNA

AL 10A0EOPERATING RING

CHANNEL SELECTOR SWITCH

HORIZONTAL CONTROL RELEASE LOCK SWITCH

7777.71;

MANUAL PRESET SWITCH

SQUELCHSWITCH

FOCUSCONTROL

BRILLIANCE AF GAINASTIGMATISM CONTROL CONTROL RF GAINCONTROL

CIRCLE CONTROLOIAMETER LIGHTS CALIBRATESENSECONTROL SWITCH SWITCH

POWER SUPPLY

REMOTE-OFF-LOCAL SWITCH

AZIMUTH INDICATOR

RESETSWITCH

POWERSWITCH

OMITSELECTORSWITCHES

RA010 RECEIVER

RESET SWITCH

MAINTENANCECONTROLS

IL. (BENIN° PLATE)

dikagiiRECEIVER/POWER SUPPLY

PHONES (JACK)

Figufe 12 -1. Radio Direction Finder Set AN/URD-4( ) major components.

208

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Chapter 12MISCELLANEOUS FACILITIES

The direction finder set is designed for eithershipboard or shore use. When the equipmentis installed on ships, the bow of the ship isused as reference or zero degree direction.Signal bearings, consequently, are relative tothe ship's heading if not corrected by the actionof the signal data converter. A switch, on thefront panel of the azimuth indicator permitsselection of either a relative bearing or a truegeographical bearing of a received signal.

CLOSED-CIRCUIT TELEVISION

On larger ships closed-circuit televisionsystems are becoming commonplace. They make

SYSTEM CONTROL UNIT

CAMERA

it possible for shipboard personnel at remotelocations to view or monitor various operations,and to exchange vital information rapidly. Al-though present applications of TV are limitedto interior communications, it is envisionedthat future applications will include intershipconferences and briefings.

One closed-circuit TV system installedaboard ship is the AN/SXQ-2 (fig. 12-2). Thissystem consists of a camera, a system con-trol unit, an electronic equipment cabinet, andone or more viewer units. It is used prin-cipally for viewing the data displayed on theCIC plotting board at remote locations.

When the system is used to transfer tacticalinformation from the CIC to remote stations,

ELECTRONIC EQUIPMENTCABINET

Figure 12-2.Television System AN/SXQ-2.

209

4J3

VIEWER

27.189


the TV camera is fastened to the overheadin the CIC so that it overlooks the plottingboard. The video output of the camera issent to a maximum of eight viewer units. Fromthese video signals, the viewer units reproduceand display the data appearing on the plottingboard. Thus, cognizant personnel are informedinstantaneously and accurately of any changesin a tactical situation.

The AN/SXQ-2 system also is used aboardaircraft carriers for briefing pilots before amission. When the system is used for thispurpose, a viewer unit is installed in eachreadyroom. The TV camera is arranged sothat it picks up the briefing officer and anypertinent charts or displays. With this ar-rangement, all pilots concerned are briefedin one session.

Most aircraft carriers now have a closed-circuit television system that aids the landingsignal officers (LSO) in landing the aircraft.In general, the system operates in the followingmanner. A television camera mounted in thecenterline of the flight deck spots the plane atthe beginning of its landing approach, and followsit to the touchdown. A second TV camera onthe carrier's superstructure then takes over.Viewer units installed at strategic locationsreproduce the images picked up by the cameras.Crosshairs on the viewer screens and minute-by-minute records of time, air speed, windvelocity, and flight number on dials at the top ofthe screens are utilized by the LSO in talkingthe pilot down to a safe landing. All videoand audio information, including the conversa-tions between the pilot and the LSO, is re-corded on tape. The tape thus becomes acomplete record of each landing. This systemis referred to as the PLAT (pilot LandingAid Television) system.

ELECTRONIC COUNTERMEASURES

Electronic countermeasures (ECM) may beclassified as active or passive. Passive ECMis the use of receiving equipment to interceptenemy radar or radio transmissions. ActiveECM is the application of transmitting equip-ment that may be used for jamming the enemytransmissions.

In order to use countermeasures most effec-tively against an enemy radar, as many aspossible of the following characteristics shouldbe known about the enemy radar facility: (1) the

frequency, pulse width, pulse repetition fre-quency, and peak power of the transmissions;(2) the receiver bandwidth and the time con-stants of the receiver coupling circuits; (3) anti-jamming features; (4) amount of shielding; (5)type of indicator; (6) antenna beamwidth; (7) typesof scan; and (8) use of the radar.

To use countermeasures most effectivelyagainst enemy communications systems, thefollowing information is needed: (1) frequencyof transmission. (2) type of modulation, and(3) receiver bandwidth.

Some of the foregoing information is obtainedby analyzing the enemy transmission. Otherdata may be obtained by examining capturedequipment.

Special equipment has been developed foruse in analyzing RF transmissions. This equip-ment includes search receivers, which searchthe various frequency bands for the varioustypes of emissions; panoramic adapters, whichmeasure the frequency, strength, and type ofmodulation of a transmission in a selected bandof frequencies; and pulse analyzers, whichmeasure the pulse rate and width. The pulseanalyzer and the panoramic adapter a,-e usedwith the search receiver.

Antijamming measures or counter-counter-measures (CCM) are used to reduce the effectof enemy jamming on our own equipment. Someof the most important CCM devices in receiversare special filters that pass only the mostimportant parts of signals, thus rejecting asmuch of the jamming signal as possible. In thetransmitters, a great many radar equipmentshave tunable magnetrons whose frequency maybe varied at intervals toprevent enemy jammingtransmitters from locking on the radar signal.

Several ECM equipments (or systems) are inuse today. Among these equipments are themodels AN/SLA-1 and -2 series, AN/SLR-2,AN/SLR-10, AN/WLR-1, AN/WLR-3, AN/ULQ-5, and AN/ULQ-6. Because of the securityAN/SLR-10, AN/WLR-1, AN/WLR-3, AN/ULQ-tailed description cannot be given in this text.Further information concerning ECM and ECCMequipments may be obtained from the trainingmanuals for the Radarman rating, or from theappropriate equipment technical manuals.

UNDERWATER TELEPHONE

The AN/UQC-1( ) sonar set, popularly knownas the underwater telephone, provides CW and

210

Chapter 12 MISC E LLANEOUS FACILITIES

voice communications between surface vesselsand submarines. Although its application dif-fers, the set operates on the same principle asother sonar equipments.

The set consists of a transmitter, receiver,power supply, transducer, and remote controlunit. All controls needed to operate the setare contained in the remote control unit (fig.12-3).

To transmit by voice, a toggle switch onthe front panel of the remote control unit is setto VOICE & CW RECEIVE, the microphonebutton is depressed and the message is spokeninto the microphone. For CW transmission,the toggle switch is set to CW TRANSMIT, andthe handkey is used to send the message. Dur-ing either type of transmission, an output indi-cator on the control unit flashes each timeenergy is transmitted.

The range of the transmission varies withwater conditions and the relative noise outputof the ship. Under good conditions, com-munications between ships is possible at rangesup to 12,000 yards and in some instances farbeyond this range. On board submarines, therange may be extended over that obtained bysurface ships by the phenomenon of channeling,that is, keeping the transmission between sharptemperature gradients within the layer in whichit was transmitted. If this layer extends formany miles, the range of the signal also isextended for many miles.

lb

N

71.71Figure 12-3.Remote Control Unit for

AN/UQC-1( ).

211

COMMUNICATION CONSOLE

To centralize the control of voice com-munication circuits at key tactical stations,some large types of ships utilize communica-tion console equipments such as the AN/SIC-2(fig. 12-4). A system may conprise 1 or 2master consoles, 16 subconscoes, 4 radio-control/terminal-unit assemblies, and 1 or 2power supplies. The quantities of the variouscomponents may be varied to meet the require-ments of the vessel on which the equipment isinstalled.

Each master console provides pushbuttonselection of a combination of 1 to 16 radio-telephone curcuits (channels or frequencies)for both transmitting and receiving.

Selector switches and volume controlsmounted on the console provide facilities forthe connection of amplifiers and overhead speak-ers to permit monitoring any 4 of 16 radio-telephone circuits.

A selector switch provides for the selectionof any 1 of 16 radiotelephone circuits for quickrelay playback as recorded by a short-memoryvoice recorder.

An interphone system provides two-way ornetwork communications between master con-soles and subconsoles. Sixteen interphone cir-cuits may be selected at the master console.

At each master console, facilities are pro-vided for communications with any combination(up to 10) of 20 ship's intercom stations.

Intercom systems differ from the inter-phone in this manner: Interphones systems useradiotelephone handsets or headphones. Inter-coms are microphone speaker systems thatprovide amplified voice communications betweentwo or more stations. The intercoms are usedchiefly during routine conditims when personnelare unavailable to man all the sound-poweredtelephone circuits. During general quarters(CONDITION 0,4E) and general quarters relaxed(CONDITION ONE E), they should be used onlyfor passing emergency information.

Each master console provides facilitiesfor it mitoring or two-way communicationswithout crosstalk on any combination of 14sound-powered telephone circuits. Provisionalso is made for crossing 7 sound-poweredtelephone circuits, and for monitoring or trans-missing on the crossed circuits.

A microphone mounted on the masterconsole is provided for connection to the


SHIP'S WIRING I

sueICoNSOLESi

r.:.

.oC 0

Figure 12-4.Communication Console AN/SIC-2.

212

7.40


shipboard announcing system when the corn--renication console equipment is installed in

C1C.The subconsoles provide secondary control

points for radiotelephone and interphone cir-cuits. Each subconsole may select any 1 or 10radio circuits for both transmitting and re-ceiving. Two-way or network communicationsfrom the console to the master console andthe other subconsoles take place over any 1 of10 available interphone circuits. A radio-telephone jack is provided for monitoring theselected radiotelephone circuit or interphonecircuit.

Normally, the master console is the CICwatch officer's station while the ship is under-way. From this station, he can control asdesired: radiotelephone, interphone, intercom,sound-powered telephone, and shipboard an-nouncing circuits.

CARRIER CONTROL APPROACH (CCA)EQUIPMENT

Carrier controlled approach (CCA) equip-ment provides the means for guiding aircraftto safe landings under conditions approachingzero visibility. By means of radar, aircraftare detected and watched during the final ap-proach and landing sequence. Guidance infor-mation is supplied to the pilot in the form ofverbal radio instructions, or to the automaticpilot (autopilot) in the form of pulsed controlsignals.

Six CCA systems (or equipments) currentlyare installed aboard carriers in the active fleet.They are models AN/SPN-6, AN/SPN-10, AN/SPN-12, AN/SPN-35A, -35B, AN/SPN-42, AN/S PN-43.

The AN/SPN-6 CCA system displays anaircraft's position relative to an ideal approachpath on offset sector PPIs. These presenta-tions are viewed by an aircraft final controller,who transmits verbal landing instructions to thepilot. The aircraft is directed along an idealapproach path to a point where it is visibleto the landing signal officer (LSO). When theaircraft is visible, the LSO operates a "con-tact" light that informs the controller thatcontact has been made and that the aircraftis being brought aboard by visual means. Ifthe aircraft approaches to the minimum range of200 feet from touchdown without the LSO indi-cating that he made contact, it is given an

213

.1.J 7

instrument waveoff by the final controller atthe radar set.

The AN/SPN-10 is a computerized CCAsystem that provides precise control of air-craft during their final approach and landing.The equipment automatically acquires, controls,and lands a suitably equipped aircraft on CVAtype aircraft carriers under severe ship mution,or weather conditions.

Aircraft returning to the carrier are assignedto the AN/SPN-10 system by means of an airtraffic control computer. On receipt of anassignment, the system programs an optimumflight path for the aircraft. It also establishesa radar acquisition window (search area). Whenthe assigned aircraft enters the window, it isautomatically detected, locked onto, and trackedby the precision radar subsystem. The radar-derived data of the aircraft's position (flightpath) are compared with the optimum flight path.As a result of this comparison, correctionsignals are generated to control the aircraftalong the optimum flight path to touchdown.

If an unsafe flight or landing condition isindicated, the AN/SPN-10 signals a waveoffand returns control of the aircraft to the airtraffic control computer. In addition, the LSOor equiprent operator may initiate a waveoffsequence when, in his judgment, a safe landingcannot be accomplished. The pilot can ter-minate the automatic landing anytime at hisdiscretion.

The AN/SPN-10 has two identical controlchannels. These channels, operating inde-pendently, provide an overall maximum systemlanding rate capability of one aircraft every30 seconds, however one per minute is usuallyexperienced. Each channel has three modesof operation: automatic, semiautomatic, andmanual (voice talkdown). In all instances, themode of operation is determined by the pilotof the landing aircraft, after which the operatorwill take the appropriate action to furnish thepilot with the desired control guidance.

The AN /SPN -12 is a range-rate radar setthat computes, indicates, and records the speedof aircraft making a landing approach to thecarrier. Both true air speed and relative speedare indicated. Thus, the LSO is supplied withaccurate information on the speed of the ap-proaching aircraft, and can wave off thoseattempting to land at an unsafe speed.

The AN/SPN-35, -35A is a lightweight car-rier controlled approach radar designed to pro-vide precision range azimuth, and elevation


information for aircraft during the final ap-proach phase of flight onto aircraft carriers.

Aircraft normally enter AN/SPN-35, -35Acontrol approximately ten miles from tluch-down. Under optimum weather conditions, air-craft may enter AN/SPN-35, -35A control ap-proximately twenty-five miles from touchdown.Information presented on the indicators pro-vides the final approach controllers with pre-cision information as to relative azimuth, range,and elevation of the aircraft. This enables theoperator to direct the pilot along a predeter-mined glidepath and azimuth courseline. Allaircraft on the glideslope and azimuth course-line are displayed and can be controlled.

The three major modes of operation forthe AN/SPN-35, -35A are as follows:

(1) Normal ModeFor normal precision ap-proach operation the azimuth antenna scans a30 degree sector and the elevation antennascans 11 degrees vertically.

(2) 35 Degree Elevation ModeThe azimuthantenna scans a 30 degree sector and theelevation antenna scans 35 degrees vertically.

(3) 60 Degree Azimuth ModeThe azimuthantenna scans a 60 degree sector and the eleva-tion antenna scans 11 degrees vertically.

The AN/SPN-35A differs from the AN/SPN-35 in that the AN/SPN-35A employs a morereliable stabilization system to compensate forpitch and roll of the carrier in order to main-tain precision azimuth and elevation coverage.The AN/SPN-35A employs an electromechanicalstabilization system, whereas the AN/SPN-35utilizes the modified mechanical-hydraulic sta-bilization system of the AN/SPN-6 radar.

The AN/SPN-42 is a landing control centralwhich provides an automatic landing capabilityfor aircraft under all-weather conditions. Air-craft enter the system through an acquisition"window" approximately four miles from thecarrier. From this point to touchdown theoperation is completely automatic, the pilotserving only as monitor. When the aircraftenter this window, the precision radar of theAN/SPN-42 tracks the aircraft and feeds posi-tion information to the computer group via thebuffer group. The stabilization group feedsship's motion data to the computer group ina similar manner. Operating on the stabilizedaircraft position data, the computer group gen-erates control signals for holding the aircrafton a predetermihed flight path. Deck motion

compensation is derived by the computer groupfrom ship's motion data and is used to modifycontrol of the aircraft during the last twelveseconds of flight. Control signals and wave-offcommand are transmitted to the aircraft byway of the NTDS data link and are implementedby the autopilot and appropriate cockpit indica-tors. Video presentation is provided to theAN/SPN-42 console operator on a conventionalGCA type radar scope.

The AN/SPN-42 has three modes of opera-tion: automatic, semiautomatic, ana manual.

(1) Automatic (Mode I): In this mode, theaircraft is acquired and controlled from theacquisition "window" to touchdown without as-sistance from the operator or pilot, after thepilot signals that he is ready for control. Boththe Landing Signal Officer and controlling op-erator monitor the landing sequence and mayinitiate a waveoff whenever an unsafe flight orlanding condition exists. The pilot may alsoterminate the automatic landing at his discretion.

(2) Semiautomatic (Mode II): In this mode,the control signals are generated and trans-mitted via data link to cress-pointers forguidance to the pilot who has complete controlof the aircraft.

(3) Manual (Mode III): In this mode, theoperation is similar to GCA talkdown; no datalink is required, only voice communications.

The AN/SPN-42 is an improvement overthe present AN/S PN- 10 Landing Control Centralin that it offers far greater reliability andmaintainability. The AN/SPN-42 employs digitalcomputers and solid state circuitry, resultingin a Mean Time Between Failure of approxi-mately 250 hours in Mode I; whereas the AN/SPN-10 has a Mean Time Between Failure of35 hours in Mode I.

The AN/SPN-43 provides azimuth. and rangeinformation from a minimum range of 250 yardsto a maximum range of fifty miles at altitudesfrom horizon to 30,000 feet. The ship's radarindicators display the information to the op-erators in the Carrier Air Traffic ControlCenter. This enables the operator to directthe aircraft along a predetermined azimuthcourseline to a point approximately one quartermile from touchdown. At night or during ad-verse flying weather however, control of theaircraft is transferred to the precision approachradar (AN/SPN-35) or Landing Control Central(AN/SPN-42) for guidance along the glidepath andazimuth courseline to the carrier landing ramp.

214


The AN/SPN-43 modifies and improves theAN/SPN-6 radar air space coverage requiredfor carrier landing operations.

The present AN/S PN- 6 radar's vertical beamwidth of 2 1/2 degrees is inadequate to sim-ultaneously cover normal carrier approach andbolter/waveoff patterns. Furthermore, theAN/SPN-6 no longer provides adequate rangecoverage for surveillance of aircraft at highaltitudes.

TARGET CONTROL SYSTEM

The AN/SRW-4( ) target control system isinstalled principally aboard destroyers equippedwith the Drone AntiSubmarine Helicopter(DASH). The system provides positive controlof the drone during all phases of flight, in-cluding takeoff and landing, by transmitting tothe helicopter commands in the form of codedFM radio signals.

The system consists of duplicate trans-mitters, coders, antennas, and operating con-trol positions. Selection and operation of thetransmitting arrangement are accomplished bythe flight controllers at the operating position.Normally, one operating position is installedin the CIC; the other position is located in thevicinity of the flight deck. By manipulating thecontrols at the operating control positions, thecontrollers send altitude, bearing, speed, andvarious special command signals to the drone.In the drone, the signals are accepted by areceiver and processed and applied to an Auto-matic Flight Control Set (AFCS). The AFCScauses the drone to execute the commandsignals.

The drone is started and preflighted fromthe deck controller's position. On signal fromthe CIC controller, the deck controller launchesthe drone and vectors it toward the target orto a holding position. He then relays to theCIC controller the altitude, speed, and headingof the drone as indicated at his control position.The controller in CIC sets these data into hisoperating position, and takes control of the dronewhen it appears on the CIC radar display. Hepilots the drone throughout its mission andreturn to the ship. When the drone comesinto view, control is transferred back to thedeck controller, who executes the approach andlanding.

INFRARED EQUIPMENT

Infrared equipment belongs to a family ofdevices which use electro-optics for com-munication, surveillance, detection, and nav-igation. Also included are image intensifyingnight observation devices, low level television,and lasers.

Infrared equipment is designed to create,control, or detect invisible infrared radiations.The equipment is of two types transmitting andreceiving. The transmitting (source) equipmentproduces and directs the radiations. The re-ceiving equipment detects and converts the ra-diations into either visible light for viewingpurposes, or into voice or code signals foraudible presentation.

Infrared devices can be used for weaponguidance, detection of enemy equipment andpersonnel, navigation, recognition, aircraftproximity warning, and communications. De-pending on its application, the equipment iseither passive or active. The active methodemploys both transmitting and receiving equip-ment, whereas the passive method requiresonly receiving equipment.

The infrared spectrum, which extends fromthe upper limits of the radio microwave regionto the visible light region in th:: olectromagneticspectrum (fig. 12-5), is divided into three bands:near infrared, intermediate or middle infrared,and far infrared. Devices operating in thenear and middle bands are used for ranging,recognition, and communications. They nor-mally have a usable distance range of 6.5 to10 miles. Equipment that operates in the farinfrared band is used for ranging, missileguidance, and the detection and location ofpersonnel, tanks, ships, aircraft, and the like.This equipment is usually effective at distancesbetween 100 yards and 12 miles.

Some of the infrared devices in use in thefleet today are the blinker equipments AN/SAT-( ), and VS-18( )/SAT; the voice/tone equip-ments AN/SAC-4, AN/PAC-3, and AN/PAR-1;and the viewer AN/SAR-( ) equipments. Abrief description of the equipment follows.

Perhaps the most widely used infraredtransmitting gear is the VS-18( )/SAT hood,with filter lens. It is mounted on the standardNavy 12-inch searchlight (fig. 12-6). It blocksmost of the visible light so the searchlightcannot be seen at a distance. The light isoperated in the same manner as an ordinarycommunication searchlight. Using the same

215


FREQUENCY(IN MHz)

1014

1013

1012

io"

loo

109

108

101

io6

105

104

103

102

I0

GAMMA RAYS

X RAYS (HARD)

X RAYS (SOFT)

ULTRAVIOLET

VISIBLE LIGHT;%:*:141;:eNE g Itl.F RA R E D;i1V;;:ka;;Yild;

tt, FICP,

-le

EH F

SHF

UHF

VHF

H F

LF AND MF

120.49Figure 12-5.Electromagnetic spectrum

showing infrared bands.

design, there are variations to the VS-18( )/SAThood for use on nonmagnetic minesweepers, the8-inch signal light, and hand signal lamps.

Another type of infrared transmitting equip-ment is a 360° light, which is installed in pairson yardarms (fig. 12-7) of the majority of navalships. These lights, designated AN/SAT-( ),are operated in the same manner as yardarmblinkers. They can be used as a steady source

VY,

77.58Figure 12-6.The VS-18( )/SAT infrared

hood on 12-inch searchlight.

INFRARED TRANSMITTER INFRARED TRANSMITTER(STBD OR AFT) (PORT OR FORD)

101.6Figure 12-7.Infrared Yardarm Beacons

AN/SAT-( ).

for "point of train" (POT) purposes, or theycan be used for signaling or recognition pur-poses.

A third important transmitter is the X-9Bsmall craft beacon. It is similar to the AN/SAT-2 but is smaller and powered by 24 voltsfrom the small craft electrical system.

The voice-tone equipments are not ingeneral use. They work by modulation of

216


a light beam which is received and amplifiedby a photocell receiver.

Electronic infrared viewers convert theinfrared rays to visible light. They must beused to detect signals from the VS-18( )/SATor AN/SAT-( ), or to observe a night sceneilluminated by an infrared searchlight.

The AN/SAR-4( ) viewing set (fig. 12-8)is a very old set still used in the fleet. Itconsists of two main units; (1) a 115 volts ACconverted to a 20,000 volts DC power supply,and (2) the viewer unitwhichconsistsof a sealedhousing and two interchangeable sets of lenses.The housing contains an image converter tubewhich produces an image of the infrared sceneon a phosphorescent screen. The AN/SAR-6viewing set (fig. 12-9) is similar to the AN/SAR-4( ) except that it has an internal batterypower supply instead of a separate power unit.The AN/SAR-7( ) viewing set (not shown) is

malt SUPPLY

similar to the AN/SAR-6 but is smaller andlighter. The Type T-7 (AN/PAS-6) infraredmetascope (not shown) is a small pocket-sizedviewer used chiefly in amphibious operations.It includes an infrared flashlight which can beused for signaling, chart reading, and the like.

OBJECTIVE FOCUSING RING

RANGE LIMIT STOP

METEOROLOGICAL EQUIPMENT

Electronic meteorological equipments con-sist of a variety of equipments, each servingdifferent purposes. Electronic devices havebeen developed to measure cloud heights andvisibility. Others measure winds aloft, aswell as temperature, pressure, and humidityin the upper air. Still others were developedas complete weather stations that report auto-matically by radio. By far the most sophis-ticated of the recent developments of electronic

RUBBER EYE WIELD

$.6X EYEPIECE LENS FOCUSING RING

INFRARED VIEWER

FOCUSING KNOB

RID INDICATOR LIGHT

STRAIN CABLE RESTRAINING SCREW

TOGGLE SWITCH

DUST CAP

RUBBER SOOT

76.

PRIMARY POWER CABLE

IoiC-..- .,-...f

ia:Avo4oiftr-zu.

MECHANICAL STRAIN CABLE

I

PLUG CONNECTOR

HIGH.VOLTAGEPOWER CABLE ASSEMBLY

Figure 12-8.Electronic Infrared Receiver AN/SAR-4( ).

217

62.11


TECHNICAL MANUALS CARRYING CASE PROTECTIVE COVER

441411114___

CARRYING STRAPS

ACCONVERTER OUST COVER RECEIVER

LS% EYEPIECEASSEMBLY

4% EYEPIECEASSEMBLY

Figure 12-9.Electronic Infrared Receiver AN/SAR-6.

meteorological devices are the weathersatellites.

Two meteorological devices that are rep-resentative of the types carried aboard navalvessels are the AN/AMT-11( ) radiosonde andthe AN/SMQ-1( ) radiosonde receiving set.(Radiosondes are the flight equipment used inmaking upper air pressure, temperature, hu-midity, and, in some instances, wind observa-tions. Depending on the type they are carriedaloft by ballons or are dropped from aircraft.)

The AN/AMT-11( ) radiosonde (fig. 12 -10)is an expendable scientific instrument designedto be carried aloft by a sounding balloon. Dur-ing its flight, the radiosonde transmits pulse -modulated radio signals in the frequency range395 to 406 MHz. When properly recordedand interpreted, these signals give a continuousreading of the pressure, temperature, andhumidity of the atmosphere through which theinstrument passes. Wind direction and velocity

DUST COVER

120.50

are measured by tracking the radiosonde withradar or radio direction finders.

Radiosonde receptor AN/SMQ-1( ) (fig.12 -11) receives, amplifies, demodulates, andgraphically records the signals transmitted bythe AN/AMT-11( ). The received signals arepulses of RF energy. The frequency of repeti-tion of these pulses depends on meteorologicalconditions. Each pulse is approximately 250to 275 msec in duration, and the pulse repeti-tion rate varies from 10 to 200 PPS. Usually,the received signal is a series of pulses atone audio rate followed by a series of pulsesat a different audio rate. Each series of pulsescauses the receptor to record on a chart in acertain position, as determined by the audiorate of that particular series of pulses. Theorder in which these different series are re-corded is known and common to all radiosondesof a particular type. Thus, it is possible tointerpret and evaluate the chart.

218


TEMPERATURE

ELEMENT

RAIN-SHIELD

SUPPORT

HUMIDITYELEMENT

AIR DUCT

BATTERY

STRAP

ANTENNA

BATTERY

120.51Figure 12-10.Radiosonde AN/AMT-11( ).

RADIAC EQUIPMENT

An important factor in the control of dangerto personnel from nuclear radiation is thedetermination of how much radiation has beenabsorbed by personnel and how much is presenton the ship. Because it is impossible to see,feel, or smell radiation, special instrumentshave been developed to detect and measure radia-tion. These radiological measuring instrumentsare known as radiac devices. (Radiac is a shortterm derived from the underlined letters of thewords radioactivity detection, indication, andcomputation.) Radiac instruments are designedto (1) detect and measure alpha, beta, gamma,and neutron radiation, (2) measure the inten-sity of radiation, (3) determine the extent of con-tamination, (4) provide information for calcu-lating the length of time that contamination willexist in an area, and (5) protect personnel byproviding means for determining the radiationdose received.

Radiac instruments are of two general types:(1) those that show how much radiation has been

219

CABINET, ELECTRICALEQUIPMENT

RECEIVER, RA010

RECORDER,

WEATHER DATA

POWER SUPPLY

-\...ANTENNA

120.52Figure 12-11.Radiosonde Receptor

AN/SMQ-1H.

received over a period of time (accumulateddose); and (2) those that indicate the amountof radiation at any particular instant (doserate). Instruments of the first type, usuallycalled dosimeters, are used to measure theamount of radiation to which a person has beenexposed during a given period of time. Equip-ment of the second type are radiacmeters, andare used chiefly for surveying contaminatedareas, structures, or objects to determinethe amount and type of radiation emitted.

Dose rate or intensity is expressed aseither "roentgen per hour" or "rads perhour." The roentgen is the unit of exposureto radioactive doses of gamma and X-rays.The roentgen is being replaced by rad as thestandard unit of absorbed radioactive dose.Because absorbed dose is the most critical ofthe two, most new detection devices are scaledto read in rads. An added factor in using radsis that the term expresses the dose from any


type of radiation, whereas roentgen relatesonly to gamma radiation or X-rays. Due to thelarge number of detection devices still in usethat are scaled in roentgens, roentgen is usedin this text.

DOSIMETER

A typical pocket dosimeter of the self-reading type is the IM-9( )/PD. This instru-ment and its charging unit PP-354( )/PD areshown in figure 12-12. At one end of thedosimeter is an optical eyepiece; at the otherend, a charging contact. When the dosimeteris fully charged, an indicator viewed throughthe eyepiece is at the zero point on a scale.As radiation penetrates the instrument, itscharge is dissipated or neutralized, and theindicator moves along the scale a distanceproportional to the quantity of radiation re-ceived.

By holding the dosimeter to the light andpeering through the eyepiece, the total radiationdose received in milliroentgens can be readdirectly from the scale. The instrument meas-ures (up to 200 milliroentgens) the X- or gammaradiation accumulated by an individual. It isused by personnel who work in contaminatedareas to indicate when the accumulated maxi-mum permissible exposure is reached.

Although a self-reading dosimeter, it re-quires a separate charging and adjusting device

CHARGINGUNIT

POCKETiirprDOSIMETER---__,

11.360Figure 12-12.Pocket Dosimeter IM-9( )/PD,

with chargtng unit PP-354( )/PD.

for setting the movable element on the zeroof the interior scale. The charger (fig. 12-12)requires no external power source; it producesa static electrical charge when the knob onthe front of the unit is rotated. This pocket-sized device, known as the PD-354( )/PDcharger, can serve many types of dosimeters.

The high-range nonself-reading dosimeter,DT-60/PD (not shown) is for use by all ship'spersonnel. This dosimeter consists of a specialphosphate glass housed in a moistureproofplastic case. The dosimeter is about the sizeof a pocket watch, weights less than an ounce,and is of sturdy construction. It will measureaccumulated dose from 10 to 600 roentgens. Aspecial instrument, CP-95/PD, is required toread it. The dose indication does not changewith time (after use); therefore, the dosimetermay be reused and read repeatedly.

RATEMETER

Ratemeters used for measuring radiationintensity (dose rate) contain electronic circuitsthat detect the presence of radiation and indi-cate its intensity on a direct-reading meter.These radiac instruments are available invarious sizes; some are portable, others arefixed. The ratemeters use different detectionmethods to measure alpha, beta, gamma, andneutron radiation. Among the various typesare the AN/PDR-18, -27, -43, -45, -56, -65, -70and the AN/SDR-1, -2. A description of someof these ratemeters follows.

The Radiac Set AN/PDR-2'I (fig. 12-13) isa portable, watertight, battery-operated instru-ment that furnishes visual and aural indicationof the detection and/or measurement of gammaand beta radiation. It has a range of 0 to 500milliroentgens per hour (MR/HR) and is usedto detect low intensity beta radiation or lowintensities of beta and gamma radiations to-gether, or detect and measure gamma radia-tions alone. It is used to detect low intensitiesof beta and/or gamma radiation, such as mightbe found on clothing or hands of personnel,or in moderately contaminated radioactiveareas. In general, it is used for detailed moni-toring of personnel, spaces, and material.

The high-range intensity meter, AN/PDR-43( ), is a "pulsed" (controlled on time)end-window Geiger-Mueller (G.M.) type,portable radiac for measuring gamma radiationand detecting beta radiation (fig. 12-14). Theend-window G.M. tube and associated electronic

220


RANGEKNOB

HEADSETJACK

CAP ANDCHAIN

CABLE

Si UD CAP

METER

PUSHBUTTONSWITCH

ASSEMBLY

CARRYINGHANDLE

COVER

HOUSING

STUD

WELL FORPROBE

RADIACDETECTOR PROBE

100.128Figure 12-13.Radiac Set AN/PDR-27( ).

circuits are contained in a single metal case.X-ray and gamma radiation penetrates materialmore readily than does beta; therefore an"end window" of relatively smaller thicknesscompared to the remainder of the cylinderwall is used to permit beta penetrations. Thegamma-intensity range scales are 0 to 5,0 to 50, and 0 to 500 roentgens per hour.Beta-gamma radiation may be detected on theserange scales by properly positioning the functionselector slide (beta shield-source slide) locatedon the bottom of the case. A 50-microcuriesource is contained on the function selectorslide to check the range scales for responseto radiation. The numerals on the meterface change with the position of the rangeselector switch. The following controls areprovided; (1) a range selector switch withpositions for OFF, BATT, and the three rangescales; and (2) a function selector slide withOPERATION CHECK, GAMMA, and BETApositions. In the OPERATION CHECK position,the end-window of the G.M. tube is exposedto the 50 microcurie source. In the GAMMAposition, only gamma radiation is detected by

by the G.M. tube. In the BETA position,the end-window of the G.M. tube is exposedto beta and gamma radiations.

The AN/PDR-56 (fig. 12-15) is the Navy'sstandard alpha survey meter. This radiacset is hand carried and is comprised of aratemeter with an auxiliary probe, a shoulderharness, a headset, a probe handle extension,and a carrying case (fig. 12-15. The ratemeterreceives pulses from the probe and convertsthem in a discriminator and ratemeter ciruitto a meter reading. The reading is proportionalto the amount of alpha contamination as seenby the probe. The AN/PDR-56( ) detectsand measures the intensity of alpha radiationin counts per minute.

The AN/PDR-65 (fig. 12-16) is a high-intensity instrument that provides gammaradiation dose and dose rate information neededfor tactical decisions. It is designed primarilyfor fixed shipboard installation but can beused as a portable instrument. It measuresgamma field intensity to 10,000 rads/hr anddose to 10,000 rads. The rate meter portionof the instrument has four sensitivity ranges:0 - 10, 0 - 100, 0 - 1000, and 0 - 10,000.Accumulated dose is given numerically inincrements of 1 rad. The radiacmeter consistsprincipally of a detector assembly, power supplyand remote control unit, remote detectormounting bracket, 200 feet of remote detectorcable, and a carrying case.

The AN/PDR-65 utilizes a recycling ioniza-tion chamber detection principle with a recyclingevent occurring every 0.5 millirad. (A recyclingionization chamber charges and discharges likea capacitor.) A sounder with a low-rangecapability gives an aural indication of eachrecycling event. The detector assembly canoperate remotely up to 500 feet from theinstrument housing. Two units may be inter-connected, e.g., one at a topside station andone belowdeck, so that the dose rate topsidecan be monitored at the readout unit belowdeck.

The AN/PDR-65 is designed for continuousoperation from a 115-volt,, 80 -hertz circuit.For the portable mode of operation it is providedwith four rechargeable nickel cadmiun Ctatteries.

The AN/SDR-1 and -2 are older fixedradian systems aboard ships. They indicatefield intensity of gamma radiation up to 10,000roentgens per hour. These sets have audiblealarms that ring at a rate proportional tothe field intensity. The alarm may be set

221


A. RANGE SELECTOR svnTal

e. CALIERATION POTENTIOMETERCOVER

C. FUNCTION SELECTOR SLIDE

IRANGE

0-po soo0 so ,n,0 5 Om

Figure 12-14.Radiacmeter AN/PDR-43( ).

to operate when the radiation field exceedsa preset level of intensity between 0 to 1000milliroentgens per hour.

The systems include remote radiac in-dicators and a training device. The trainingdevice can simulate high-range readirgs forthe remote indicators during field defensetraining exercises. The radiacmeter is designed

222

100.129

for continuous operation from a 115-voltAC power source. It, in turn, supplies thepower to all other units. If the normal *powersource fails, a built-in battery operates theequipment for a maximum of 50 hours. Whenthe AC power is returned, the dischargedbattery commences recharging and assumesa full charge within 24 hours.

,Aa


A7,

Figure 12-15.Radiac Set AN/PDR-56.

100.213Figure 12-16.Radiac Set AN/PDR-65.

223

5.184

INDEX

Active sonar, 131-134AEW radars, 100-101AEW terminal equipment, 120-121Air-search radars, 98-99Air-search 2-coordinate radars, 107-110Air-search 3-coordinate radars, 110-112Altitude-determining radars, 99Amplitude modulation, 20Antenna stabilization data equipment, 123-124Antennas, 96-97

barrel stave antenna, 97bedspring array, 97billboard array, 97paraboloidal antenna, 97

Antennas and propagation, 18-19Auxiliary equipment 55-64, 115-124

AEW terminal equipment, 120-121antenna multicouplers, 57-58antenna stabilization data equipment, 123-124antenna tuning, 55-57IFF equipment, 121-123remote-control units, 61-64repeaters (indicators), 115-120transfer panels (transmitter and receiver),

58-61Azimuth-range indicator, 144-146

Basic computer, 173-192central processing unit, 174components used, 178computer tools, 179operational features, 192operations of, 178

Bathythermograph, 148-150expendable AN/SSQ-56, 150mechanical, 148-150

Buffer-frequency multiplier, 19

Carrier control approach (CCA) equipment,213-215

Classification of radio emissions, 26-28Closed-circuit television, 209-210Communication console, 211-213Component identification, 2Conical monopole antenna, 53Continuous wave radar, 101-104Continuous-wave transmitter, 19-20

Data Processing Line Printer RO-302/UYK-5-(V), 186, 190

Data Processing Set AN/UYK-1, 189-191Data Processing Set AN/UYK-5(V), 184Digital computers, 173-192Digital Data Computer C P-789(V)/UYK, 184-186Digital Data Recorder-Reproducer RD-270(V)/-

UYK, 186-187Doppler effect, 101, 169-170Dosimeter, 220

Electronic countermeasures, 210Electronic data processing equipments, 179-183Electronic navigation aids, 151-172Electronic terms, 4-16

Facsimile (FAX), 81-86facsimile recorder AN/UXH-2B, 84facsimile recorder RD-92( )/UX, 83keyer adapter KY-44( )/FX, 84-85modulator MD-168( )/UX, 85

Fan antenna, 52Fathometers, 135,143-144Fire control and missile guidance radars,

112-115Fire control radars, 99-100, 115Frequency bands, 18Frequency carrier-shift system, 67Frequency modulation, 21Frequency spectrum, 17-18

Glossary and nomenclature, 1-16Guided missile launcher, 203Gunfire control system, 205

gun director and computer, 205target .designation system, 205

224

HF receivers, 43-48HF tran3mitters, 29-36

IFF equipments, 121-123IFF systems, 104Infrared equipment, 215-217Integrated doppler navigation, 169-170

Joint Electronic Type Designation System,1-3

INDEX

Keyer adapter KY-44( )/FX, 84-85Keyers and converter, 73-75

Launcher feeder, 203LF receivers, 43-48Loran navigation system, 151-160

equipments, 156-159Omega navigation system, 159principle of, 151-156Shoran, 159-160

Mechanical bathythermograph, 148-150Meterological equipment, 217-219MF receivers, 43-48MF transmitters, 29-36Mine hunting sonar, 134-135, 140-143Missile guidance radars, 100, 115Modulator, 91-92Modulator MD-168( )/UX, 85Multiplexing, 79-81

Navigation aids (electronic), 151-172Nomenclature and glossary, 1-16

Omega navigation system, 159Oscillator, 19

Paraboloidal antenna, 97Passive sonar, 130-131Patch panels, 75-78Power amplifier, 19Power supply, 19-20Pulse-modulated radar system, 90-96

indicator (repeater), 94-96modulator, 91-92receiver, 92-94transmitter. 92

Radar, 87-104altitude determination, 89bearing determination, 88-89range determination, 87-88theory of operation, 87-89

Radar equipment, 105-124Radar functions and characteristics,

AEW radars, 100-101air-search radars, 98-99altitude-determining radars, 99continuous wave radar, 101-104doppler effect, 101, 169-170fire control radars, 99-100missile guidance radars, 100surface-search radars, 97-98

Radar set AN/SPS-5( ), 105Radar set AN/SPS-6C, 107-110

Radar set AN/SPS-8A, 112Radar set AN/SPS-10( ), 105-106Radar set AN/SPS-21( ), 107Radar set AN/SPS-29( ), 110Radar set AN/SPS-30( ), 112Radar set AN/SPS-40, 110Radar sets AN/SPS-42 and -39A, 112Radar set AN/SPS-48(V), 112Radar set AN/SPS-52, 112Radar set AN/SPS-53A, 107Radiac equipment, 219-223

dosimeter, 220ratemeter, 220-223

Radio, 17-28Radio communications

digital data, 17radiofacsimile, 17radiotelegraphy, 17radiotelephony, 17radioteletype, 17

Radio direction finders, 207-209Radio emissions classifications, 26-28Radio equipment, 29-65Radio Navigation Set AN/SRN-9, 164-168Radio operating positions and remotes, 2-3Radio receiver AN/BRR-3, 44-45Radio receivr AN/SRR-11, 44,46Radio receiver AN/SRR-19A, 44-45Radio receiver AN/URR-21( ), 49Radio receiver AN/URR-27( ), 49Radio receiver AN/URR-35C, 49-50Radio receiver AN/URR-44, 47Radio receiver AN/WRR-2B, 44, 47Radio receiver AN/WRR-3B, 44, 47Radio receiver R-390A/URR, 47-48Radio receiver R-1051B/URR, 48Radio receiver RBA, 44, 46Radio transceiver AN/PRC-10( ), 41Radio transceiver AN/PRC-25, 42Radio transceiver AN/PRC-41, 43Radio transceiver AN/URC-4( ), 42-43Radio transceiver sets AN/URC-9( ), AN/SRC-

20( ), -21( ), 39Radio transceiver AN/URC-32B, 35

9'/-104 Radio transceiver AN/URC-35, 35-36Radio transceiver AN/URC-58(V), 34-35Radio transceiver AN/VRC-46, 37Radio transceiver SCR-536( ), 41-42Radio transmitter AN/CRT-3A, 39Radio transmitters AN/SRT-14, -15, and -16,

29-31Radio transmitter AN/URT-7( ), 37-38Radio transmitter AN/URT-23(V), 33-34Radio transmitter AN/URT-24, 33Radio transmitter AN/WRT-1A, 31

225


Radio transmitter AN/WRT-2, 31Radio transmitter model TED, 38Radio transmitter-receiver AN/GRC-27A,

38-39Radio transmitter-receiver AN/SRC-16, 36-37Radio transmitter-receiver AN/SRC-23(V),

31-32Radio transmitter-receiver AN/WRC-1( ), 33Radio transmitter-receiver model TCS-( ),

32-33Radioteletype (RATT) systems, 67Ratemeter, 220-223Receivers, 22-26,43-49, 92-94

multiplexing, 26radiofrequency receiver, 22-23single-sideband communications, 24-25superheterodyne AM & FM receiver, 23-26UHF receivers, 48-49VHF receivers, 48-49VLF, LF, MF, and HF receivers, 43-48

Recorder-reproducer, 146-148Remote-control units, 61-64Remote transmitter control unit C-1004( )/SG,

78Representative missile fire control system,

201-205Representative weapons system, 195-201

target detection, location, and identification,195

weapon control system, 195-198weapon direction equipment, 198-201

Satellite Navigation System, 160-170description of, 161integrated doppler navigation, 169-170Radio Navigation Set .AN/SRN-9, 164-168

Shipboard antennas, 49-55conical monopole antenna, 53fan antenna, 52sleeve antenna, 52-53VHF-UHF antennas, 53-55whip antennas, 52wire antennas, 51-52

Shipboard weapons control system, 193-206Ships Inertial Navigation System (SINS), 160Shoran, 159-160Sleeve antenna, 52-53Sonar, 125-135

types of, 130-135active sonar, 131-134fathometer (depth-sounding sonar), 135mine hunting sonar, 134-135passive sonar, 130-131variable depth sonar, 134

Sonar accessories, 144-150

azimuth-range indicators, 144-146bathythermograph, 148expendable bathythermograph AN/SSQ-56,

150mechanical bathythermo; r; :ph, 148-150recorder-reproducer, 1.26-148target course projector, 146

Sonar equipment, 136-150Sonar set AN/SQS-4( ), 136Sonar set AN/SQS-23( ), 138Sonar set AN/SQS-26( ), 140Sonar sets AN/SQS-29( ) to -32( ), 136-138Sound, 325-129

generation of, 125sound paths and modes of detection, 126-129

layer depth, 127thermal gradients, 127

transmission of, 125Surface-search radars, 97-98, 105-107Surface ship equipments, 136-144

Tacan navigation system, 170-172AN/SRN-6( ) radio set, 171-172

Target control system, 215Target course projector, 146Target designation system (TDS), 205Telegraph terminal set AN/UCC-1(V), 79Teletype and facsimile, 66-86Teletype equipment, 67-78Teletypewriter set AN/UGC-6, 71-73Teletypewriter set AN/UGC-13, 73-74Teletypewriter set AN/UGC-20, 70Teletypewriter set AN/UGC-25, 71Teletypewriter set TT-47( )/UG, 69-70Teletypewriter set TT-48( )/UG, 69-70Teletypewriter set TT-69( )/UG, 70Teletypewriter set TT-176A/UG, 70Tone-shift modulation system, 67Transducers, 129-130

cylindrical array, 130electrostrictive process, 130magnetostrictive process, 129-130

Transfer panels, 58-61Transmitter, 92Transmitters, transmitter-receivers, and

transceivers, 29-43high-frequency transmitters, 29-36medium-frequency transmitters, 29-36portable and pack radio equipment, 39-43UHF transmitters, 38-39VHF transmitters, 37-38

226

X30

UHF receivers, 48-49UHF transmitters, 38-39

INDEX

Underwater telephone, 210-211Uniform Automatic Data Processing System

(UADPS), 189

Variable depth sonar, 134Variable depth sonar

140VHF receivers, 48-49VHF transmitters, 37-38VHF-UHF antenna, 53-55VLF receivers, 43-48

set AN/SQA-10,

Voice modulation, 20-22amplitude, 20frequency, 21

Weapons system concept, 193-195control units, 194delivery units, 194destructive unit, 194-195detecting units, 193-194

Whip antenna, 52Wire antenna, 51-52

227* U. S. GOVERNMENT PRINTING OFFICE : 1969 31.1-41.9/31

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Shipboard Electronic Equipments

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