July, 1970/75 cents Broadcast Engineering. · 2019. 7. 17. · staff at KCFA was plagued by...

July, 1970/75 cents

Broadcast Engineering.the technical journal of the broadcast -communication's industry .1 A HOWARD W. SAMS PUBLICATION

MeasuringRF Outputpage 24

Line Surge Protection

Setting Up SCA Operation

Campus Transmitter Control

How good is the new Electro-Voice RE20studio dynamic microphone?Here's proof from the new scoringstage at Glen Glenn.

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So for their new scoring Studio M,Glen Glenn engineers asked to see thelatest products in every category ... tape,film, electronics, and - of course - mi-crophones. Especially a new E -V dynamiccardioid microphone which they had seenin prototype form earlier.

Glen Glenn put the RE20 to the test.Including days of studio experiments andactual sessions that pitted the RE20against every type of musical instrument.Plus a searching critique by the musiciansthemselves. The RE20 passed every testwith flying colors.

As a result, when Studio M was com-pleted, RE20's were on the booms ...almost four dozen of them from ourfirst production run.

Since then, Glen Glenn has scheduleda number of major recordings withRE20's. And the RE20 has often beenused where previously an expensive con-denser was the automatic choice. Why?Because the RE20 has proved itself asignificant advance in microphone design.With wide -range, peak -free response onaxis (even the off -axis response is betterthan many other studio microphones onaxis). Transient response rivals any otherstudio microphone, regardless of design.Directional control is uniform and pre-dictable from every angle. Yet proximityeffect is virtually eliminated (a problemthat plagues almost everycardioid - except E -VContinuously Variable -D'microphones).

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July, 1970

July, 1970 Volume 12, No. 7

Broadcast EngineeringThe technical journal of the broadcast -communications industry

111

24 Measuring RF Power Output. Power measurement techniquesfor radio and TV stations. Includes the direct and indirectreading procedures and comments on directional and non -directional antennas. Pat Finnegan.

32 Line Surge Protection For Remote FM Stations. After select-ing a beautiful mountain site for their FM transmitter, thestaff at KCFA was plagued by excessive line surges. Articledescribes how they solved the problem using instantaneousrelays. Tom German.

36 SCA Principles and Practices. Second part of a two-part serieson getting into SCA. Includes equipment available in genera-tor and monitor lines. T. R. Haskett.

42 Feeding and Controlling Carrier Current Transmitters. Acampus FM station uses the phantom circuit to solve theirproblems. John A. Bredensen.

46 Burst Phasing Can Be an Operational Adjustment. Althoughthe manufacturers say "No", the operators insist on an easiermeans of controlling burst phase. Elmer T. Schorle, Jr.

48 Television: A Long Range Forecast. A scientist discusses theTV technological achievements we may expect to realize someday. Dr. Dennis Gabor.

50 Film Systems In CATV. A speech on film systems deliveredat the Pennsylvania CATV convention.

ABOUT THE COVER

Making RF power outputmeasurements can becometoo subjective, unless ac-curately calibrated testequipment is used. See page24 for a summary of mea-surement procedures. (Photocourtesy of Gates RadioCompany.)

DEPARTMENTS

Direct Current 4Letters to the Editor S

Industry News 14Educational Broadcasting 18CATV Scope 20Engineer's Exchange 52New Products 55Tech Data 60Ad Index 62Classified Ads 64

Copyright, 1970, Howard W. Sams & Co.. Inc. All Rights Reserved: Material may not be re-produced or photocopied in any form without written permission of publisher.

EDITORIAL

GEO. H. SEFEROVICH, DirectorRONALD N. MERRELL, EditorCARL BABCOKE, Solid State

MORRIS COURTRIGHT, AutomationPAT FINNEGAN, MaintenanceHOWARD T. HEAD, FCC RulesROBERT A. JONES, Facilities

A. PETERSON. Editorial AssistantH. G. ROESLER, CartoonistDUDLEY ROSE, Art Director

EDITORIAL ADVISORY BOARD

LES NELSON, ChairmanHoward W. Sams & Co., Indianapolis

CIRCULATION

ROBERT CURRY, DirectorEVELYN ROGERS. Manager

ADVERTISING

E. P. LANGAN, DirectorR. JACK HANCOCK, Manager

S. F. WILSON, ProductionJAKE STOCKWELL, Sales

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BROADCAST ENGINEERING is publishedmonthly by Intertec Publishing Corp.1 1014Wyandotte Street, Kansas City, Missouri64105. Telephone: 913/888-4664.

BROADCAST ENGINEERING is mailed freeto qualified persons engaged in commer-cial and educational radio and televisionbroadcasting. Non -qualified subscriptions inthe U.S. are $6.00 one year, $10.00 twoyears, $13.00 three years. Outside the USAadd $1.00 per year to cover postage.Single copy rate 75 cents. Back issue rate$1.00. Adjustments necessitated by sub-scription termination at single copy rate.

Controlled Circulation postage paid at In-dianapolis, Indiana.

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21

DIRECT CURRENTFROM D.C.July, 1970

By Howard T. Head

UHF Television Spectrum Reallocated to Land MobileAs predicted (April, 1970 D.C. Pompous Predictions), the Commission hasreallocated a substantial chunk of UHF television broadcast spectrum to theland mobile radio services. The upper end of the UHF television band,Channels 70-83 inclusive (806 MHz - 890 MHz), has been withdrawn fromtelevision service and reallocated to land mobile. Also reallocated toland mobile was half of the 942-952 MHz band formerly assigned for auralbroadcast STL use (See Oct. 1968 Bulletin).

On the lower seven UHF channels (Channels 14-20), the Commission hasauthorized sharing between television and land mobile on a geographicalbasis. One or two television channels in this frequency range arebeing assigned for land mobile operation in each of the nation's tenlargest urban areas. Engineering requirements are established toprotect television station Grade B contours from co -channel, adjacent -channel, and intermodulation (including I.F. beat) interference.

The bite at the lower end of the UHF band was considerably less thanthe television broadcasters had feared. The Commission had originallyproposed geographical sharing in the top 25 markets with as many asfive television channels being shared in some areas. Also, the finalprotection criteria are substantially more conservative than the Com-mission had originally proposed. Also turned down was a proposal bythe land mobile services for the complete reallocation of Channels 14-20to land mobile over a period of years.

Numerous details remain to be worked out. Opening up televisionchannels for land mobile in Chicago and Philadelphia requires reassign-ing presently authorized stations. Also, in the cases of Cleveland,Detroit, and Los Angeles, agreement must be reached with the Canadianand Mexican governments for the non -television use of the shared channels.

Also left dangling is the fate of over 800 UHF television translatorsnow operating on Channels 70-83. The licenses of these translators willbe renewed only on a "secondary" basis, that is, the translators willbe required to accept any interference from land mobile operation andwill not be permitted to cause any interference to land mobile operation.The Commission has proposed to open up Channels 14-69 for translators,but there is considerable question as to whether all UHF translators canbe accommodated on these channels unless the present protection rulesare substantially relaxed.

The Commission is also considering reallocating the frequency spectrumbetween 2150 and 2160 MHz as a replacement for aural studio transmitterlinks for the 5 MHz taken away between 942 and 952 MHz.

4

(Continued on page 6)

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The Commission does not intend to provide, at this time, for anyfurther sharing of the lower UHF channels by land mobile. The Com-mission is pressing forward with plans for setting up a RegionalFrequency Management Center in the Chicago area to improve existingland mobile frequency assignment proceedings, and is looking to the landmobile interests to exploit the new frequency assignments in the900 MHz region.

Commission Working on Further CATV RelaxationAlso as predicted (April, 1970 D.C. Pompous Predictions), the Commissionis preparing to announce plans for further relaxation of the presentrestrictions on CATV expansion. Expected to be announced shortly areproposals to permit CATV systems to import as many signals as necessaryto provide all three network services and at least four independentsignals. No limit would be placed on ETV importations.

The CATV systems would be required to delete commercials of distantindependent stations and insert those of local UHF stations. Engineeringstandards would be proposed covering most aspects of CATV performanceexcept on -channel ghosting. Consideration is being given to requiringa minimum of 20 channels for new CATV systems and possible requirementsfor two-way transmission. The system would be allowed a pay -televisionchannel on the same basis as provided for broadcast systems (Feb. 1969Bulletin).

Removal of AM Loss Resistors ProposedAn AM station at Havre De Grace, Maryland, required by the terms of itslicense to reduce the effective field of the antenna system, has askedthe Commission to permit this reduction by reducing the transmitteroutput. Under present requirements, the station must operate itstransmitter at the full 5 kW output while dissipating approximately1.1 kW in a set of loss resistors.

The same procedure is required to be followed by approximately 200 AMstations whose effective field at full power would exceed that penulttedby the allocation standards. The Commission's position in the past,in responding to informal requests for this change, has been that notype approval data are available for transmitters operating at otherthan the standard powers. The petition points out that this is aminor problem easily curable, and that the present system is wastefulin many respects by reason of the extra heat generated and the demandson final amplifier tube life. The petition points out the almost universalpractice of operating FM and television transmitters at less than ratedpower to achieve desired radiated fields.

Time Set for Retention of "Local Inspection Files"The Commission has amended the rules requiring the maintenance of"local inspection" copies of applications for construction permits andlicenses so as to specify a time limit for their retention. The rulespreviously in effect required such files to be preserved indefinitely.

Under the new rules, these public inspection files must be maintainedfor a period of seven years. A single exception is made in the caseof engineering material relating to a former mode of operation, suchas a different frequency, power, or directional antenna pattern, whichis required to be preserved for a period of only three years.

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LETTERS n Fil

Who's What In Broadcasting?Dear Editor:

I have just read with great inter-est the material in Mr. Head's por-tion of your fine magazine, as wellas comments made at the VirginiaAssoc. of Broadcasters by the FCCand as per your request for com-ments . . . here are some of mine.

I feel that one must go back tothe days of radio when you had anengineer in one room and the an-nouncer in another, this is rare to-day. The time came when the"Combo man" was born for severalreasons, the major one I would saywould be the advent of the "DJ"and economy on the part of radio ingeneral at that time. Later on withmore and more announcers gettinginto this "Combo man" position, away was found to get around therequirement that a person knowwhat he is doing from an engineer-ing standpoint to pass the first phoneexam . . . ala the advent of the"quickie school" or "six week won-der".

It is indeed funny that it hastaken the FCC all of these years tofinally realize that the "First Phone"is no longer an indication of theperson's knowledge about technicalsubjects . . . it has come to thepoint that it is no more than a pieceof blue paper that anyone with thetime and money and average abilitycan obtain purely for the privilagesit offers to the broadcaster/opera-tor/DJ. For those of us that wentto hours and hours of school to learnthe material so that taking the testwas easy it is nothing short of aninsult. So what do we have now..the radio business is full of "sixweek wonders" and I feel that it islike a person holding a driver's li-cense that he obtained without anymore than taking the written exam.

The FCC is showing signs of cit-ing the operators for violations thatoccur when they are "on the log"and making First Phone holders re-sponsible for being engineers . . .

this is great . . . it is one of thefirst truly great decisions that the

Commission has come out with inyears. For far too long the stationhas had to pay for a technicallystupid First Phone . . . but nowwhat happens to the DJ at a direc-tional when the FCC drops in andfinds the place "Out to lunch". Dothey hold this First Phone respon-sible? I feel that NAB's proposalto allow 3rd Phones to operate highpower and directional AM's is a stepin the right direction. And the re-vision of the First Phone exam toeliminate the possibility of a per-son passing without actual knowl-edge of the material to the extentthat the Commission requires theperson to have and be responsiblefor is another "well it's about time"move on their part.

This has been a long time coming,but perhaps if we all hold our fin-gers crossed, the FCC, the schoolsand the management of broadcastfacilities will know who is a tech-nician, who is an operator and whois a combo man.

These are my feelings and trustthose of many in my shoes, and Ihope that in some way my contri-bution to Broadcast Engineeringwill help keep this movement aliveand move it toward its logical con-clusion.

Clay FreinwaldChief EngineerKMOTacoma, Washington

Get And Keep TalentWith Reasonable PayDear Editor:

I have read with much interest,your article in the April issue con-cerning Educational Television andthe New Engineering Program. In-deed this should serve to eliminatesome of the problems of obtainingcompetent technical people, especi-ally for the educator. However, myreaction to the problem is a bit dif-ferent.

I believe there is one major prob-lem involved in the marriage of the


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July, 1970 9

Letters To The Editor


educator to television which tendsto "breed" a shortage of talent avail-able to him (the educator). Thisproblem is created by the educatorand in his hands is the solution. Theproblem is the educator's failure tor'recognize that television is a very

specialized field and consequently,unwillingness to provide a salarycommensurate with the technicaltalent required. I refer to the moresophisticated installations to befound in our institutions of highereducation.

While this is not true in everycase, I do know from experiencethat it is a real thing and is mostcertainly a deterrent to applicantsfor engineering positions. A univer-sity that spends a half -million dol-lars for the ultimate in a full color,network quality television produc-

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tion studio and then installs heavy-duty doors in anticipation of the on-rush of experienced, competent en-gineering personnel applying for theposition at $9,000 to $10,000 ayear is spinning its wheels and man-ifesting the epitomy of optimism.This is a rather sad commentary onknowledgeable people. Probably themost common argument against arequest for salary on a level withability is, "But our professors areonly making $10,000 a year!". Ofcourse if they can install, operateand maintain the system no prob-lems. Obviously, this type of state-ment is simply evading the issue,side-stepping the real issue of se-lecting specialized talent for a spe-cialized job.

Increasing ValueIndustry has recognized that the

experienced technical person, re-gardless of formal education, is avery valuable person and his valueis ever increasing, even to the pointof being preferred in some instancesover degree -type engineers. I believeeducators should be more aware ofthe nature of television hardware,its complexity, sophistication andthe high degree of technical skill re-quired to operate and maintain it.This type of understanding wouldloosen the purse strings a little, al-low a little selectivity in personneland buy some extra low-cost insur-ance for a very large investment.The benefits would be shared byeducator and personnel alike. Forexample, the difference between$10,000 and $13,000 spent for sal-ary could very possibly buy theextra technical "know-how" neces-sary to mean the difference in asystem maintenance cost which isrealistic and one which producesmild coronary thrombosis and gen-eral absenteeism at board meetings.

Price and quality have alwaysbeen directly proportional, whetherwe're talking about groceries, cars,equipment or whatever. The sameis true for personnel. Down -gradeon either and you have only saveda small amount at the moment. Ifeducators are willing to pay for whatthey get, then they can rightfullyexpect to get what they paid for.

Bob J. Henson, Engr.ITV ServicesPaducah Public SchoolsPaducah, Kentucky


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Keeping Up WithOp Amps

Dear Editor:In Mr. Dale Wolter's letter to the

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Is The NAB LoweringTechnical StandardsDear Editor:

It is interesting to read on pages8 and 9 of the May issue of Broad-cast Engineering of the difficultiesin obtaining competent engineeringpersonnel for broadcast stations dueto several reasons, most of whichstem from the FCC decision about20 years ago to allow remote con-trol of broadcast transmitters and/or lesser7grade operators-and thento turn the page and read on page11 that NAB is proposing still moreof the same medicine for the indus-try and claiming in face of all evi-dence to the contrary that this willnot result in a lowering of technicalstandards. I would like to see thereasoning behind the idea that re-placing an engineer who "hasknowledge of the facts" with some-one who knows little and probablycares even less about technical mat-

ters will have no effect on the qual-ity of operation of a station. Theaccompanying increase in FCCRules violations proves such reason-ing to be faulty.

Those who NAB proposes as op-erators are not engineers, they areannouncers and they do not obtaina license for any other reason thanto announce and to play records.They generally care little or nothingabout the engineering responsibili-ties of their jobs and do that partgrudgingly, if at all.

I am wondering when ALL theengineers are eliminated from theindustry and their jobs are filledby these and the "minority appli-cants" who will then fix it whenit quits and where will he havegotten his experience?

Lynn R. Williams, c.e.WBEJ Inc.Elizabethon, Tenn.

Hose That GunDear Editor:

I would like to impart a helpfulhint that I have found to be veryuseful in our shop.

To solve the problem of bent anddamaged solder gun tips, I cut afive inch length of water hose, andcut it down the side the full length.The sleeve is then slid down thetip, all the way to the trigger. Thissleeve will protect the tip from dam-age, even if the gun is dropped. Foronly a few cents worth of hose, youcan forget about worrying about thetips, when carrying the gun in thetube caddy, or out on remotes.

Perry LaddKMNE-TVBassett, Neb.

Send Your LettersAnd Comments

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Broadcast Engineering1014 WyandotteKansas City, Mo.

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July, 1970 I3

NEWS

CARS For CATV

FCC Holds Line On LinksPetitions filed by Laser Link

Corporation, the National Associa-tion of Educational Broadcasters(NAEB), and the Association ofMaximum Service Telecasters(AMST), asking reconsideration ofa Commission order, released No-vember 14, 1969, authorizing mic-rowave stations in the CommunityAntenna Relay Service (CARS) totransmit CATV-originated programmaterial have been denied by theCommission (Docket 17999).(CARS is a microwave serviceowned by a CATV system for thepurpose of bringing in televisionsignals for use over the system. TheCommission's November 14 orderalso authorized the licensing ofCARS studio to head -end links andCARS mobile pickup stations inthe 12.7-12.95 GHz band.)

In denying the Laser Link andNAEB petitions, the Commissionstated that they are substantiallyidentical to pleadings filed and de-nied in a ruling involving the estab-lishment of a CATV Local Dis-tribution Service in the 12.7-12.95GHz band (Dockets 18452, FCC70-404).

AMST's petition, the Commissionsaid, is largely a summary of its re-quest for reconsideration of the FirstReport and Order in Docket 18397(20 FCC 2d 201), concerning theorigination of programing by CATVsystems. To the extent that theAMST petition is directed to theorigination of CATV programinggenerally and not specifically to pro-gramming carried over auxiliarymicrowave stations, the Commissionremarked, the questions raised byAMST can more appropriately beconsidered in Docket 18397.

Specifically, AMST asked thatthe notification requirement of Sec-tion 74.1031(c) of the rules be ex-tended to require CARS applicantsto notify local broadcasters directlythat they are applying for a stationthat will carry originated program-

ing; that applications for studiohead -end link stations not begranted unless the alternative ofwire transmission is not reasonablypracticable; and that a CARS ap-plicant be required to show that itintends to make minimum use ofits remote pickup station, and itslicense renewal be denied if it can-not.

The Commission found no needto require direct notice to localbroadcasters of applications fortransmission of CATV-originated

program material. It stated that itpresently issues public notices of allapplications for authorizations in theCAR service; that a reporting formis being prepared that will makeavailable current information on or-igination being undertaken byCATV systems; and there is noneed to adopt special procedures justbecause auxiliary facilities are usedto carry CATV-originated pro-grams.

The Commission found it pres-ently unnecessary to adopt minimumusage standards for CARS pickupstations. The Commission statedthat it expects that CATV operatorswho invest in auxiliary microwavefacilities will use them regularly,and that it does not wish to discour-age investment in this type of equip-ment "by threatening, even in theabsence of alternative users of thesame frequencies, not to renew li-censes if the equipment is insuffi-ciently used."

Commission Knocks "Plugola"Rules to prevent outside financial

interests from influencing selectionor presentation of broadcast mate-rial, a practice known as "plugola",have been tentatively adopted bythe FCC. They require that selectionof broadcast material be insulatedfrom such interests; that they beidentified on the air when they areinvolved in a program; and that thelicensee be alert to the problem toinsure compliance with the rules(Docket 14119).

The Commission, in an appendixto the tentative order, issued a pri-mer of typical situations and rul-ings.

They said the rules, in a newSection 73.1204 were adopted be-cause sponsorship identificationrules didn't go far enough. Presentrules require disclosure to the pub-lic only where consideration has ac-tually been furnished by others tothe licensee or his employees forthe broadcast of promotions or theinclusion of certain matter in broad-casts, and do not require disclosurewhere the benefit has accrued indi-rectly to the licensee or employeeby reason of ownership of financialinterest in the products or services

promoted. The principle behind dis-closure is that the public is entitledto know the real interests of thosetrying to influence it.

It was also stated that public in-terest requires that broadcast mate-rial be presented on the basis of itsown merit, and when outside finan-cial interests are a factor influenc-ing the selection and presentationof broadcast material the provisionsand purposes of Section 317 of theCommunications Act require thatthe existence of such interests mustbe disclosed so that the audience"may evaluate the material withthis knowledge."

"And then for negative carriershift I'd recommend ..."


Rule Adopted

For BroadcastOf Phone Calls

Broadcast licensees will be re-quired to notify in advance anyparty to a telephone conversationthat is likely to be recorded forbroadcast or to be broadcast as itis going on, under new rules adoptedby the Commission (Docket 18601).

The new rule, Section 73.1206,specifies that: "Before recording atelephone conversation for broad-cast, or broadcasting such a con-versation simultaneously with its oc-currence, a licensee shall inform anyparty to the call of the licensee'sintention to broadcast the conversa-tion, except where such a party isaware, or may be presumed to beaware from the circumstances of theconversation, that it is being orlikely will be broadcast. Such aware-ness is presumed to exist only whenthe other party to the call is asso-ciated with the station (such as anemployee or part-time reporter), orwhere the other party originates thecall and it is ovious that it is inconnection with a program in whichthe station customarily broadcaststelephone conversations."

On July 9, 1969, the Commissionadopted a Notice of Proposed RuleMaking, 34 F.R. 11984, in orderto clarify the notice requirementsfor licensees for broadcast of tele-phone conversations. Prior to theCarterfone decision, (13 FCC 2d420 (1968)) a "beep tone" was usedto alert a party to a telephone con-versation with a broadcast stationemployee that the call was being re-corded,., and that the station mightbroadcast the conversation. Now,however,, broadcast stations may in-terconnect their facilities to ex-change and toll telephones andbroadcast live, two-way conversa-tions without the "beep tone" warn-ing. The tone is still required incases where the conversation is be-ing recorded, under the new rulethe licensee now must inform theother party that the conversation,whether live or recorded, is goingto be put on the air.

The Commission said there aresome situations where awareness

and therefore implied consent maybe presumed from the circumstancessurrounding the telephone conver-sation, such as "open mike" showsand conversation between stationemployees and station newsmen and"stringers."

FCC Cracks Down onStandard BroadcastModulation Rules

To counter the use of radio trans-mitters with excessively powerfulmodulators capable of producingharmful interference, amended stan-dard broadcast rules, limiting posi-tive modulation to 100 percent andproviding separate definitions ofpositive and negative modulationpercentages, have been advanced bythe Commission in a Notice of Pro-posed Rule Making.

The action would amend Part 73of the rules, Sections 73.55 and73.14. Present rules limit negativemodulation to 100 percent, but setno limit on positive modulation.

The Commission stated that cer-tain manufacturers are offering forsale broadcast transmitters withmodulators capable of supplyingconsiderably more power to the car-rier than is necessary for 100 per-cent modulation with a symmetricalwaveform-a 5 kilowatt transmitterequipped with a modulator normallyintended for a 10 kilowatt unit, forexample. Such transmitters, theCommission said, undoubtedly willbe employed with a substantial de-gree of negative peak limiting, toproduce positive peak modulationlevels greatly in excess of 100 per-cent. This kind of operation will ma-terially increase the sideband powerand the potential for interferencewith other stations, the Commission

Pe.

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remarked. The Commission ex-pressed particular concern with theeffect on co -channel and adjacent -channel operations.

The Commission found that 5kilowatt transmitters with "souped -up" modulators are presently beingdelivered to broadcasters and arebeing used by them without anyCommission authorization. (Com-mission acceptance requirements forparticular types of transmitters donot cover the modulator designchanges involved.)

The Commission noted that it ispossible to achieve positive modu-lation levels somewhat higher than100 percent with present transmit-ters, and that it has been consideredpermissible where the modulatingwaveform was only moderately un-symmetrical. Although proposing tolimit positive modulation to 100 per-cent, the Commission said that ithas not decided what higher limit,if any, should be permitted, and thatit will accept comments on thispoint.

17 UHF Channels TakenFor Land Mobile Use

A total of 17 UHF -TV channelsin tea states has been withdrawnfrom television service by the FCCfor the next five years to implementthe Commission's program to pro-vide additional spectrum space forland mobile radio services by util-izing certain UHF -TV channels forland mobile radio in the top tenurban areas of the United States.

The seventeen assignments, noneof which have operating stations,are in the states of California, Illi-nois, Massachusetts, Michigan, NewHampshire, New Jersey, New York,Ohio, Rhode Island and West Vir-ginia.

In Joliet, Ill., and New Bruns-wick, N.J., the withdrawn channelsare assigned to authorized stationswhich have not yet been constructed.In both cases, the Commission saidit was adding additional channelsto the Table of Assignments forthe cities affected, "so that inter-ested parties may proceed withprompt activation and rendition oftelevision service." Unoccupiedchannels in Elgin, Ill., and AsburyPark, N.J. will be reassigned forthis purpose. In Santa Barbara,

July, 1970 15

Ask these peoplehow to process16mm and 8mmEktachrome film fast.WANEFt. Wayne, IndianaCorinthian Stns.

KARDWichita, KansasKansas State Network Inc.

EASTMAN KODAKCOMPANYRochester, New York

KAUZWichita Falls, TexasBass Bcstg. Stns.

RAY -CHRISPRODUCTIONSLittle Rock, Arkansas

CBS NEWSNew York, New York

CBS NEWSWashington, D. C.

KCBDLubbock, TexasCaprock Bcstg. Co.

WCTVTalahassee, FloridaJ. H. Phipps Bcstg.Stn.

KDVTDallas, TexasDoubleday Stns.

GENERAL DYNAMICSCORP.Ft. Worth, Texas

KFDAAmarillo, TexasBass Bcstg. Stns.

KHOUHouston, TexasCorinthian Stns.

CHRYSLERCORPORATIONChelsea Proving GroundsChelsea, Michigan

WHTNHuntington, W. VirginiaReeves Bcstg. Stns.

KHVHHonolulu, HawaiiWestern Telestations

WISHIndianapolis, IndianaCorinthian Stns.

KJACPort Arthur, TexasJefferson Amusement Co.

WJARProvidence, Rhode IslandOutlet Company Stns.

WKYOklahoma City, OklahomaWKY-TV System Stns.

NEWS FILM LAB. INC.Hollywood, California

WNDUSouth Bend, IndianaNotre Dame University

UNIVERSAL LAB.Kowloon, Hong Kong

KNXTLos Angeles, CaliforniaCBS Owned Stations

ROJANASIL COLORPROCESSING LAB.Bangkok, Thailand

KOSAOdessa, TexasDoubleday Stns.

KOTVTulsa, OklahomaCorinthian Stns.

KRBCAbilene, TexasAbilene Radio & TV Stns.

WM:0WAugusta, GeorgiaRust Craft Bcstg. Stns.

KRGVWeslaco, TexasManship Stns.

WSWOSpringfield, OhioSouth -Western Ohio TV Inc.

KTVTFt. Worth, TexasWKY-TV System Stns.

KVIIAmarillo, TexasMarsh Media Ltd.

!CCTVSacramento, CaliforniaCorinthian Stns.

RAI RADIO TELE-VISIONE ITALIANARome, ItalyItalian National Network

WBRZBaton Rouge, LouisianaManship Stns.

KCSTSan Diego, CaliforniaBass Bcstg. Stns.WLUCMarquett, MichiganPost Corp Stns.

KNTVSan Jose, CaliforniaStd. Radio & T.V. Co.

KTULTulsa, OklahomaGriffin-Leake Stns.

SOUND PHOTO LAB.Lubbock, Texas

WTVCChattanooga, TennesseeMartin Theatres ofGeorgia Stns.

KTVEMonroe, LouisianaGray Communications Stns.

Do they knowsomething aboutJamieson's Mark IVcolor processoryou should know?

KATVLittle Rock, ArkansasGriffin-Leake Stns.

WUSNCharleston, South CarolinaReeves Bcstg.

VMVIndianapolis, IndianaSarkes Tarzian Stns.

WPTAFt. Wayne, IndianaSarkes Tarzian Stns.

WTVMColumbus, GeorgiaMartin Theatres ofGeorgia Stns.

WTOKMeridian, MississippiSouthern TV Corp.

KBMTBeaumont, TexasLiberty Corp.

KFYRBismark, North DakotaMeyer Bcstg. Stns.ABS-CBNManila, PhilippinesAlto Bcstg. SystemWPRIProvidence, Rhode IslandJohn B. Poole Stns.

NHK-NIPPON HOSOKYOKAITokyo, JapanJapan National Network

J. OSAWA & CO., LTD.Tokyo, Japan

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Calif., where an application forChannel 20 was recently dismissed,the Commission said it was makingeducational Channel 32 available.

In a separate action, the Com-mission issued a rule making noticeasking for comments on new assign-ments to accommodate ETV chan-nels 70 in Bowling Green, Ohio,and 77 in Glen Ridge, N.J., bothof which are in the Channel 70-83area re -allocated by the Commis-sion for land mobile use.

The Commission proposed to de-lete Channel 54 in Toledo to per-mit assignment of Channel 40 toBowling Green. In the case of GlenRidge, it noted that because of thenumber of UHF assignments in theNortheast, no replacement appearedpossible. But it said a study wouldbegin shortly on means to make an-other channel available and it askedfor comments on possible replace-ments. The New Jersey PublicBroadcasting Authority has filed anapplication for the channel for useat Montclair.

NAEB Selects TwoFor Top Positions

James A. Fellows, director of theOffice of Research and Develop-ment, National Association of Ed-ucational Broadcasters, has been ap-pointed executive director of theNAEB's newly -created ProfessionalServices Department, according toan announcement by NAEB Presi-dent William G. Harley. WilliamDale, who has been serving as as-sistant to the president, NAEB, hasbeen appointed associate director ofthe Instructional Services Depart-ment.

Both appointments are part of areorganization plan at NAEB whichwas voted by the association's Ex-ecutive Board of Directors at ameeting held in May. Fellows andDale assume their new responsibili-ties immediately.

Fellows, who will administer anexpanded range of services to allcategories of the NAEB member-ship, has been with the NAEB since1962 when he was named associatedirector of the Office of Researchand Development.

Dale came to NAEB last year.He had served for four years in theeducational system in American Sa-moa.

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EDUCATIONAL

1°1 EliProc Amps The New Breed

Amplifiers which correct videowaveform distortion resulting fromimperfect transmission paths havebeen with the broadcaster since theearly days of TV. Over the yearstheir capability has been graduallyextended and the past few yearshave witnessed the evolution of asophisticated breed of processingamplifiers which can correct manyvideo signal deformities quite re-liably.

With program origination at amultiplicity of points, often not un-der ideal conditions, the use of pro-cessing amplifiers to restore themaximum possible degree of stan-dardization to a signal is not onlydesirable but just about mandatory.

The educational broadcaster isbeset by the same type of trans-mission difficulties as any other TVstation; he utilizes network lines,originates and/or transmits remotefeeds, he uses ST links, and off -airpickup. Within his own plant hemay have a complex system of videointerconnections requiring standard-ization and restoration of signallevels at many points-VTR's stu-dio outputs, transmitter feeds, etc.In some cases the equipment hemust work with may not be so so-phisticated. He may for instancewant to use a helical VTR for in -class use and later dub this tapeinto broadcast format. So a videoprocessing amplifier must be usedon the output of the helical VTR.All of these locations can be wellserved by a processing amplifier, sowe'll take a look at what these de-vices can do in the way of signalrestoration.

A color composite video signalis an extremely complicated wave-form but there are a few basic par-

ameters about it which allow manycommon distortions to be removedor minimized. Basically this boilsdown to that information which isrecurrent or that about which thereis some pre -knowledge. The flat re-current portions of the horizontalsync interval can be used to DC re-store the waveform, thus removinglarge hum components, tilt and lowfrequency bounce. The incomingsync can be stripped off and usedto genlock a local sync generatorwhich is in exact phase (both lineand frame) with the incoming signal.Then the old blanking and timinginformation can be gated out andthe clean local version reinsertedwith the proper timing restored toFCC specs.

Color burst can be gated out,amplified, limited and used to locka local 3.58 MHz oscillator. This

Input

Buffer

AGC Level

man agc

Sync

Stripper and

Regenerator

GenlockedSync

Generator

AGC

oscillator is in turn gated by a localburst flag signal and a new andregenerated burst is added back tothe signal. These examples are theeasy part, since all of the timingcomponents of a video signal areknown in advance, and are repeti-tive.

Video Signal ProblemsThe picture portion of the video

signal cannot be regenerated. Anynoise, distortion, ringing or smear-ing must necessarily be passed alongwith the desired picture information.The best we can do is to re-estab-lish the correct peak level to 100IEEE units and normalize lumi-nance to chroma ratios. Peaks canbe set either manually or automatic-ally with video AGC. Chroma canbe split off separately through abandpass filter to give independentcontrol, allowing non -normal levelsto be brought back into balance.Black and white clipping can alsobe provided in the luminance chan-nel, which allows clipping of over-shoots and/or noise pulses. An over-all black level control can be pro-vided which allows matching thesetup of the original signal or cor-rection as may be necessary.

Since video processors are com-monly used as an integral transmit-ter component, they also containsome circuitry to pre -correct normalvideo modulator distortions. Thisusually amounts to some white

bypass Bypass

+ DCOutput

normal

setupwhite white blackstretch clip clip

Clamp BlankerWhite

StretchB and W

Clip

Luminance Channel

Band pass

FilterH Amp

H Delay

Match_L -

Chroma Channel

v bh Pulse Outputs

Fig. 1 Block diagram shows a viceo

abypassrelay

707rerOutputs

Sync

Amp

Output

Mixer

Burst

GenBurst

Amp

BurstPhase

proc-amp broken into its component pieces.


stretch and differential gain adjust-ment to compensate for inherentnon-linearities of the transmitter.These controls are not intended tocorrect for other defects, as otherforms of distortion are not predict-able.

These are the basics of whatvideo processors can do today.Many options and versions exist ofcourse; AGC or no AGC, burst re-gen or not, genlocked or regeneratedsync just to name a few. The degreeof elaboration necessary can onlybe determined by the individual as-sesing an individual situation. Andwith economics such an importantfactor, the luxury items such asautomated control will get the mostcritical appraisal. In Figure 1, theblock diagram shows how a videoproc-amp can be broken into itscomponent pieces. Judging fromyour own particular needs you canmentally select those features youneed.

Input video enters the process-ing amplifier and is buffered by aninput amplifier and applied to async stripper/regenerator and themanual gain pot. The sync stripperremoves the sync portion of thevideo signal and shapes it to a uni-form rise -time and constant level.

Although noise and amplitudevariations are removed by this stage,the original timing may be lost dueto pulse shape deterioration. Tocompletely re -time all the sync andblanking information, the signal isapplied to a genlocked sync gener-ator which can restore complete andaccurate timing of all pulses whichmake up the EIA waveform, evento the point of replacing missingpulses. This feature allows completecontrol of the output sync signals,and guarantees a constant sync sig-nal, even in the case where the in-put disappears, wherein the syncgenerator provides a "black" signal.

The input video also feeds amanual gain control. The variableoutput of this pot feeds the videomode switch, which selects the man-ual mode or the AGC mode. Thevideo is then split into two routes,the luminance channel and thechroma channel.

In the chroma channel, the videois filtered by a 3.58 MHz bandpassfilter which selects the chrominancecomponents, including burst. Burstis then split off separately and sentto the burst regen circuit. Contin-

uing through the chroma channel,the overall chroma level is modi-fied by a gain control which allowsthe correct luminance/chroma ra-tio to be re-established. A compen-sating delay is also used to matchthe delay of the luminance informa-tion and ensure correct luminance/chroma registration in the repro-duced picture.

Luminance ProcessingIn the luminance channel the pro-

cessing is a bit more complicated.An input clamp is used (driven fromthe horizontal drive signal) to DCrestore the video signal and removelow frequency disturbances. The DCclamping level is variable, which al-lows adjustment of setup. Next, theold blanking is removed by the re-generated blanking signal whichcompletely clears out the horizontaland vertical blanking intervals.Black and white clipping is used toclip transients above or below thedesired levels, and the white stretchcircuit gives a boost in levels aroundthe 100 IEEE point. The correctedoutput of this channel is applied tothe output mixer.

The burst regenerator gets a sig-nal from the chroma channel andthe sync generator. The sync signalis used to gate out the incomingburst, then it is amplified and lim-ited to a constant level and used tophase -lock a local 3.58 MHz oscil-lator. This oscillator is runningcontinuously and a local burst flagsignal (generated from local syncand blanking) is used to key out aburst signal which is applied to theoutput mixer. This circuit also hasa color kill stage which senses theabsence of burst at the input andkeys off the burst for monochromesignals.

As we said previously, the videochannel can get its input from twosources, the manual control or theAGC circuit. The AGC circuit getsits input from the input buffer andan output sample signal from theoutput mixer. It acts to hold the out-put peak levels to 100 IEEE as theinput varies over a nominal range.There is usually a preset lower thres-hold (to allow the fades to black)and a peak level control. These unitsusually allow the option of AGCaction on either VITS or VITS andvideo.

Regenerated composite sync isalso applied to the output mixer,along with all of the previously de-

scribed signals; luminance, chrom-inance and burst. These four com-ponents are linearly mixed in theoutput stage to recreate a compositevideo signal. To gain a better feelfor how all this fits together, theoperational controls will be de-scribed. All of the primary ratios ofa color signal can be adjusted in-dependently: sync, white level, set-up, burst, and chroma level. Theburst phase of the re-inserted signalcan also be adjusted. Additionally,the clip and stretch controls areavailable although these are gener-ally not primary controls. With theoption of automating many of thesecontrols it can be seen how thecomplexity of one of these devicescan grow. Commonly automatedfeatures are video AGC, color kill(delete burst and chroma), syncchangeover (reverts to black withabsence of input). Just how far youcan go depends upon your require-ments and pocketbook.

If you have a requirement for avideo processing amplifier, these area few basic things to keep in mind.Like almost anything these deviceshave their limitations. They will doa great job of cleaning up the syncportion of the waveform and re-establishing levels, but there is verylittle they can do with picture dis-tortions. And also, like many otherthings, they come in various de-grees of quality. It might pay tospend some "trial basis" time, ifpossible, to find the one proper fora particular requirement. When setup and operated properly, a videoprocessor can do a remarkable jobof restoring standardization to a de-graded signal.

We have tried here to set downa few of the basics of video process-ing as a starting point. Should youwant to dig into the area further trythe references listed to see how dif-ferent manufacturers approachthese problems. With this knowl-edge and a familarity with your ownparticular requirements, you shouldthen be ready to put one to worksolving those signal problems.References

1) Kenneth P. Davies, "AutomaticCorrection of Network Chrominanceand Luminance Levels" 1969 NABConvention Proceedings

2) Richard S. Wise, "A CombinedVideo Processing AGC Amplifier",Journal of the SMPTE, 78:261-265,April 1969.

July, 1970 19

C-7

CAN SCOPE

For CATV

Community Antenna RelayFor July, let us take a look at

what the Community Antenna Re-lay Service is and what it offersCATV operators.

The FCC, in Part 74, Subpart J,defines a Community Antenna Re-lay Station (CARS) as a fixed ormobile station used for the trans-mission of television and relatedaudio signals, signals of standardand FM broadcast stations andcablecasting, from the point of re-ception to a terminal point fromwhich the signals are distributed tothe public by cable.

AssignmentsIn conjunction with this, specific

FCC types of service assignmentshave been provided for use in theCARS program. These are:

1. Local Distribution Service(LDS)-This type of service usuallyis a fixed CAR station used withina CATV system or systems. Tele-vision, and related audio, FM andcablecasting signals, will be trans-mitted from a local point to one ormore receiving points and then dis-tributed to the subscribers by cable.

2. Community Antenna RelayStudio to Head-ed Link (SHL)-This is a fixed CAR unit used fortransmission of television programmaterial from a CATV studio tothe head -end of a CATV system.

3. Community Antenna RelayPickup-This is normally a landmobile CAR facility which trans-mits television signals from thescenes of events occurring at pointsdistant from CATV studios andthen fed to the CATV studios orhead -ends.

Cablecasting is defined as thatportion of the television program-ming originated by the CATV oper-ator and then distributed on theCATV system. This is exclusive oftelevision broadcast signals distrib-

uted on the CATV system.The CATV system operator's at-

tention is alerted to the fact thatrecent FCC actions have providedregulations so that CAR licenseesmay institute the transmission oforigination programming materialby CATV systems operating CARS

as described in sections 1, 2 and 3.CAR licensees may interconnecttheir facilities with those of otherCAR or common carrier licensees.

The frequency range set aside bythe Commission for Community An-tenna Relay Stations is essentially12,700 to 12,945.7 MHz dividedinto five groups. Group A and Bare for the sound portion of thesignal using FM transmission.Group A frequency assignmentsrange from 12,700 to 12,950 MHzand Group B are from 12,712.5 to12,937.5 MHz. Under Group A andB there are ten 25 MHz primarychannels along with nine secondarychannels interspaced between theprimary channels. The major factorin assigning the proper frequenciesis that television pickup, STL andintercity relay stations shall notcause any harmful interference toCARS. Similarly, CARS shall not


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July, 1970 21


cause harmful interference to tele-vision STL and intercity relay sta-tions. As an example, televisionpickup stations and CAR pickupstations shall cause no interferenceto existing and subsequently author-ized television STL, television in-tercity relay, fixed CAR, CAR SHLor LDS stations.

CARS authorized to operate withvestigial sideband AM transmissionfor the visual signal, will be allo-cated frequencies within Group Cand D. The Group C and D fre-quencies normally use a channelwhich is 6 MHz wide. Auxiliarychannels have also been assignedwithin the frequency bands of 12,-933.7 to 12,945.7 MHz.

Either AM or FM modulatedmicrowave signals may be used butfor vestigial sideband AM transmis-sion the assigned visual carrier fre-quency for each channel listed inGroup C or D should be 1.25 MHzabove the lower channel -edge fre-quency. The center frequency for theaccompanying FM aural carrier ineach channel should be 4.5 MHzabove the corresponding visual car-rier frequency.

LimitationsIn addition to the requirements

described here, just what are someof the more important FCC regu-latory limitations that CARS licen-see will have to contend with whenplanning a new CARS microwavesystem? Here are some of the pointswhich the operator must remember:

. . . Remote Control Operation-CARS can be remotely controlled,provided the equipment is designed,installed and protected to preventtampering.

. . . Unattended Operation -ACARS system may be operated un-attended if the transmitter isequipped with an automatic controlwhich will permit the unit to radi-ate when it is relaying an incomingsignal and provided the transmittingapparatus can be turned on and offat will from a location which can bereached at all hours and seasons.Licensed radio personnel should beavailable for technical servicing andmaintenance to assure expeditiousperformance.

. . . Power Limitations - Thetransmitter peak power outputshould not exceed five watts on anychannel. CARS LDS stations using

vestigial sideband AM visual trans-mission should make sure that thevisual peak power on all channelsshould be maintained within 2 deci-bels of equality. The aural meanpower on each channel should notexceed a level of 7 decibels belowthe visual peak power.

. . . Emissions and Antennas-Any type of emission suitable forthe simultaneous visual and auraltelevision signals transmission maybe employed in the CARS system.

Only directive CARS transmitterantennas can be used and the maxi-mum horizontal plane beam widthbetween half power points of themajor lobe should not exceed 3 de-grees.

CARS MicrowaveWhat is a CARS microwave sys-

tem? It is usually referred to thatportion of the radio frequency spec-trum as described and discussed inthe FCC Rules and Regulations.The microwaves are transmitted andreceived over paths where the an-tennas are normally visible. Averagedistance covered by CARS is possi-bly 35 miles or more. Present CARSequipment manufactured usually issolid state designed and constructed,having very high performancecharacteristics.

The most important achievementof modern CARS microwave sys-tems is the reduction of maintenancetime which keeps operating costsdown. The type of microwave sys-tem used for CATV operations nor-mally requires a one way, ratherthan a two way, communicationssystem. CARS in general are oper-ated in shorter system paths andbecause of economic and other fac-tors are only required to conformto the FCC standards discussed inPart 74, Subpart J.

The basic equipment required toset up a CARS microwave systemfor one way TV transmission con-tains a transmitter, RF transmissionline and antenna, a receiving an-tenna, RF transmission line and re-ceiver at the distant end of thepath. The mounting heights of theantennas are determined by theequipment manufacturer after con-sideration of the physical path. Bothantennas are 6 or 8 foot diameterdishes and the transmitting antennaserves to focus the signal beam anddirects it towards the receivingantenna.

System EconomicsEconomics and performance par-

ameters are the deciding factors inconsidering the use of cable orCARS in CATV operations. Micro-wave offers the advantages of highperformance and reliability com-pared to a long line of cable re-peaters.

The cable system operator shouldalso note that the cars system shouldbe capable of meeting the require-ments of Sections 74.1050 and allsections listed in Technical Opera-tion of Part 74 Subpart J.

The basis for overcoming the vitalproblems by prospective CARS us-ers is usually solved by purchasingtype approved and type acceptedequipment and be sure to make afull study of the merits of the equip-ment relative to range limitations,video signal-to-noise versus signalinput, fade margin, effects of mois-ture on path attentuation and at-mospheric attenuation so that thebeam of energy is not blocked thusreducing the received energy.

To maintain the CARS micro-wave system at an ideal peak per-formance efficiency, the systemcould be provided with an excellenttest maintenance service. The ap-plication of the vertical interval asa carrier of video test signals inthe microwave system could be in-corporated. Test generators whosetest signals may be added to thevertical interval where video is pres-ent could be used for testing at anypoint along the CARS microwavesystem during regular workinghours, individually or in sequence.

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Broadcast Engineering1014 WyandotteKansas City, Mo.

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23

Measuring RF power output"Everyone from the owner down to the janitor is a meter reader."

By Pat Finnegan*

Any broadcast station's RF out-put power should be maintained asnear its licensed power as possibleso that an adequate signal will beradiated into its coverage area, li-cense requirements will be met, andthe FCC Rules will find compliance.Knowledge that the transmitter is

BE Maintenance Editor and Engineering VP atWLBC. Muncie. Ind.

delivering the correct output poweris especially important in those sys-tems working near or at maximumratings. This information can beobtained by using monitoring de-vices that are reasonably accurate,and properly calibrated.

Accuracy of the monitoring de-vices and calibrating instrumentsshould at least fall within the ac-curacy prescribed by the FCC Rules.Don't expect to obtain "text book"accuracy. On the other hand, theuse of the regular bench type instru-ments will not ordinarily be suffici-

TRANSMISSION LINE

TUNING UNITTO REMOTE

METER

ANTENNA

RESISTANCEMEASURED

AND CURRENTMEASURED HERE

Fig. 1 Point is shown whereantenna resistance is mea-sured and the antenna cur-rent for a single towernon -directional antenna.Coupler for remote meter isincluded.

TOWER #1

COMMONPOINT

MEASUREMENT

Fig. 2 Location of the com-mon point in a directionalsystem where the poweroutput is measured.

ent for power measurements.The measurement should be made

with a high quality meter, and itshould be one designed for meas-uring antenna current, not a make-shift, haywire affair. Equally im-portant, this meter should be onedesigned especially for use on ornear your operating frequency. (Ed.Note: When repairing any testequipment, be certain to use a cool-ant on the parts you replace beforeputting the iron on the connection.Heat will change the value of thepart, especially carbon resistors.Otherwise, your standard instru-ments will give questionable read-ings. See April, BE, page 46.)

AM MeasurementsParts 73.39, 73.51, 73.52 of the

FCC Rules cover the accuracy ofand methods of determining

power for AM stations. Directpower measurements are required.This is the product of the antennacurrent squared times the antennaresistance. (P-riz).

AM stations use a variety of con-figurations, such as; single towernon -directional, multi -tower direc-tional, and part time directional-part time non -directional antennas.Station output power is measuredat one, two, or both positions de-pending upon whether it is non -directional, directional, or both. Themajority of stations use a series fedtower, although there may be a fewshunt fed towers still around.

Non -directional antennas aremeasured right at the lead to thetower itself. This point is after thetuning coils and other items in thetuning unit. The lead and tower arethe antenna elements. The coils andcapacitors of the tuning unit areused to cancel any reactance of thetower, and also to match the an-tenna resistance to the line imped-ance. Antenna resistance measuredat this point becomes the R factorof the power formula.

The setup for measuring antennaresistance usually includes an RF


bridge, RF signal generator, and asuitable detector. Since many AMstations do not have the requiredtest equipment, this measurement isusually made by a consulting engi-neer. It should be remembered thatthe antenna resistance will changeas the tower, guys and insulators,and the ground system deteriorate.Large metallic structural changes inthe vicinity will have some effect,too.

The RF current must be meteredat the point where the resistancemeasurement was made. A metermust be permanently installed atthis point, and provisions should bemade to short the meter to protectit from lightning damage. Currentmeasured at this point becomes theI factor of the power formula.

Directional AntennasDirectional antennas are consid-

ered as a system (the system as asingle antenna) and power is mea-sured at the "common point" feedto the system, rather than at atower base. This is not to ignorethe fact that each of the towers hasits own antenna resistance, as wellas mutual coupling among the tow-ers. Each of these factors is mea-sured and computed in the systemdesign, as is the base current ateach tower. These base currentsmust be maintained within 5 per-cent of their normal values, alongwith the proper phase readings, andall other parameters of the system.

The system includes all towers,transmission lines, phase and powerdividers. The single point immedi-ately before all this is the commonpoint, and it is at this point thatthe resistance is measured. Sincethere is some loss of efficiency ina directional system, the resistancemeasured is modified by a factor of0.925 for transmitters of 5 Kw orless, and by a factor of 0.95 fortransmitters above 5 Kw. For ex-ample, the common point resistanceis measured as 50 ohms and thestation uses a 10 Kw transmitter.

The R factor to use in the powerformula would be 47.5 ohms. Shouldthe transmitter be a 5 Kw unit, theR factor would be 46.25 ohms.

A proper RF current meter mustbe permanently mounted at the com-mon point, and the current mea-sured becomes the I factor of thepower formula.

Part time directional and parttime non -directional stations useboth methods of measuring outputpower. During the non -directionalperiod, the base current of theactive tower is measured, but duringdirectional operation, the commonpoint current is measured.

Indirect PowerIndirect power measurements are

permitted on a temporary basis forvarious reasons as outlined in theRules. Such a case may be a defec-tive antenna current meter orchanges in the antenna system.Power is then computed by usingthe plate input power of the finalstage times an efficiency factor.(P=Ep x Ip x Eff.)

The efficiency factor may be de-termined by various means. For anoperating station, the logged valuesof Ep and Ip of the previous week

are used and the average efficiencyattained during that week is thevalue to use. When figuring powerfor a new transmitter that has nolog time, you may use the effici-ency factor supplied by the manu-facturer, or use the charts in theFCC Rules.

When a station makes indirectpower measurements, appropriateentries should be made in the oper-ating log, along with the efficiencyfactor used and how it was derived.This should be included on eachday's log when the indirect methodis used.

Meters and CalibrationMeters used as remote reading

HIGH WATTAGER EO STA T

120AC 60CPS

STANDARD METER BEING

METER CALIBRATED00

Fig. 3 Setup for calibration of antennameter with a standard meter. Sixtycycle current is used.

3.0

cc

a

ANTENNA CURRENT METER S. N. 45278

(EXPANDED SCALE)

NOTES:

CALIBRATION MADE AT 60CPSWITH WESTON 904 AMMETER,ACCURACY + 0. 5%

105%

2 2.0ccce

100%--- 90%TEMPERATURE DURING

CAL I BR AT ION 60° F

L.) METER SPECIFICATIONS:

INDICATION DECREASES 0.9%

1.0FOR EACH 10° F RISE.INpEASES 0.9% FOR EACH10 F DROP

0,41.0 2.0 3.0

TRUE CURRENT (AMPERES)

Fig. 4 Graph of a typical meter calibration. Special calibrations were made at theoperating current points and the tolerance points.

July, 1970 25

VISUAL TRANSMITTERAND

SI DEBAND FILTERS

DIRECTIONALCOUPLER

U

SYNC.

BLANKING

TRANSMITTER

OUTPUT METER

0 SC I LLO SCOP

CRY STAL

DIODE

r-

THRU -LINE

WATTMETERDUMMY LOAD

WATTMETER READS

------ AVERAGE POWER

CHOPPER

Fig. 5 Typical setup for calibration of the visualoutput power and power meter.

antenna current devices should beof the same accuracy and scale re-quirements as the regular basemeter.

Any sampling device for remotemeters must be on the transmitterside of the antenna current meter.Nothing should be added betweenthe antenna meter and tower.

The antenna meter should be cali-brated from time to time to insureaccuracy. If the station doesn't havethe equipment to repair or calibratethe meters, or a consulting engineeris unavailable, the meters should besent to a meter repair laboratory.The equipment needed is a standardmeter of known accuracy, a reostatand a source of AC voltage.

A thermocouple works on theprinciple of a DC voltage developedacross the ends of two dissimilarmetals, when their junction is heatedby AC current. Frequency is not adetermining factor. Thus, a 120VAC line may be used for thecalibration.

A meter that works with an ex-ternal thermocouple should be cali-brated together as a unit, and eachshould be marked to show that theydo work together. Mixing thermo-couples and meters will give erro-neous readings.

To make the calibration, set upthe equipment, starting with somelower value of current than will beused during normal operations.Make point by point readings andplot these on a graph. Make aspecial effort to check at three cur-rent points, which would be 90percent, 100 percent and 105 per-cent power. These are the toler-ances. If the meter has an expandedscale for use at two operatingpowers, do the same for each powervalue. Draw a smooth curve throughthe plotted graph, and post it nearthe antenna meter.

Thermocouples are effected alsoby ambient temperature of the airwhich may cause incorrect readings.The meter spec sheet will tell whatthese effects are and how much tocompensate for various tempera-tures. It is important to note onthe calibrations curve what the roomtemperature was at the time ofcalibration.

FM PowerParagraph 73.267 of the FCC

Rules applies to FM power mea-surements. The station has a choiceof either using the indirect methodor direct method of power mea-surement.

The indirect method is computedfrom the plate input power of thefinal stage and the efficiency factoras supplied by the manufacturer ofthe transmitter. As a formula, Out-put power=Ep x Ip x Eff.

All transmitters have some meteror device to indicate that outputpower is present. Unless such adevice is calibrated, it can't be usedfor power measurement. When thestation is using the indirect method,this meter can be arbitrarily ad-justed to indicate 100 percent whenthe plate input power is 100 percent.

Power tolerance for FM is +5percent and -10 percent of thelicensed power. The plate inputpower should be computed for thesepercentages and posted at the trans-mitter or control point.

The direct method of measure-ment makes use of an output meterthat is accurately calibrated. Ordi-narily, the sampling device for thismeter is a directional couplermounted in the line right after thetransmitter.

A directional coupler will samplethe forward or reflected wave, de-pending upon how it is installed inthe line. Therefore, if the coupleris an adjustable type, care mustbe taken that it is inserted and ad-justed in the proper orientation. Twosuch couplers are often orientatedso that one will intercept the for-ward wave, and the other the re-flected wave. The output of thesecouplers is then fed through appro-priate resistors and switches so thatthe VSWR on the line may alsobe measured and monitored. Theoutput of the couplers is an RFsignal and must be rectified to beuseful. Ususally, this is done bycrystal diodes or tube rectifiers.

In order that such an arrange-ment may be used for power mea-surements, it must be calibrated.The Rules require that calibrationtake place as a minimum at six-month intervals, although shorterintervals are preferred.

A dummy load and accurate watt-meter are needed for calibration.The dummy load must be able toabsorb the full transmitter poweroutput and should be equal to theline impedance and with negligablereactance. The wattmeter should beone that has been designed and cali-


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27

brated to work on the frequenciesinvolved.

CalibrationConnect the dummy load and

wattmeter to the transmitter. Do notmodulate the transmitter. Adjust thetransmitter output power until thewattmeter reads the required power(licensed power). The output metershould then be calibrated to read100 percent. When the wattmeterreads the correct output power andthe meter is calibrated, record theEp and Ip of the final stage, or thetotal Ep and Ip if there is more thanone output stage.

Next, increase power output untilthe wattmeter reads 105 percentpower. Note the output meter read-ing. It should read 105 percent. Ifit does not, mark the point whereit is reading as 105 percent. Donot adjust any calibration controls.Record the Ep and Ip of the finalstage. Then, reduce drive until thewattmeter reads 90 percent of li-censed power. Calculation is againrequired. Mark the meter at thispoint if it is not reading 90 percent.Record the output stage readings,and lock the calibration controls inplace.

The next step is to replace the

Dual directional coupler with crystal diodes to measure both forwardand reflected power in a 11/e inch coax line.

Dual directional couplers for forward and reflected powersin a 31/8 inch line. This one uses tube rectifiers.

line and antenna as a load on thetransmitter. Go through the 90 per-cent, 100 percent, and 105 percentpower positions and record the Epand Ip of the final stage. Thesereadings should be essentially thesame as those measured into thedummy load. If they do not agree,there is something wrong either withthe load and wattmeter, or with theantenna. Any problem in the an-tenna or line will show up as highVSWR. If the VSWR appears nor-mal, the load and wattmeter mayhave been damaged and will needto be returned to the factory forrepair and recalibration.

TV Power OutputThe television transmitter is actu-

ally two transmitters in one, theaural and the visual. Each side hasa different mode of modulation.When measuring or calibratingpower meters, the opposite trans-mitter should be turned off so asnot to interfere with the calibrations.Rules pertinent to power measure-ments will be found in Paragraph73.689.

The aural transmitter is basicallyan FM transmitter, and except forthe carrier frequency and cross tieswith the visual transmitter, its out-put power is measured and cali-brated the same as an FM trans-mitter. There is the same choice ofusing either the direct or indirectmethods of power measurement.Most TV stations use the directpower measurement as there is acalibrated load and wattmeter onhand for the visual side.

The procedures for the aural arebasically the same as those for anFM station. Since the procedureshave already been given, only thedifferences will be given here.

Operating power tolerance is dif-ferent, in that +10 percent and-20 percent are permitted. TheRules call for measuring the powerat the output terminals of the trans-mitter. This is not always an easymatter, especially in those caseswhere the aural is diplexed into thesideband filters of the visual. Toopen the line at this point may re-quire disassembly of the coax lineand fittings. Most UHF transmittersare of this nature. If this is the case,the load and wattmeter may be con-nected at the point immediatly fol-


lowing the filter unit, at the sameplace the visual is measured.

The filter unit will have a fixedloss at the aural carrier as shownin the checkout sheet of the filterunit. This loss will not change unlessthe filter unit has been damagedand, in that case, other problemswill be readily apparent in highVSWR readings and visual pictureproblems.

When calibrating the output meterfor direct power readings, add theloss in the filter unit to that whichis read on the wattmeter to get thelicensed power output. For example,if the aural transmitter is requiredto put out 2.2 Kw and the fixedloss in the filter unit is 200 watts,the wattmeter will read 2 Kw.

Visual transmitters are amplitudemodulated and the power outputmethod must be by the directmethod. That is, the transmittermust be working into a dummyload with zero reactance and resist-ance equal to the line impedance.Both the load and wattmeter shouldbe designed and calibrated to workwith the range of carrier frequenciesthat will be present.

The calibrations are made withthe transmitter modulated with astandard black picture. A standardblack picture is sync and blankingonly (no picture and no fixed setup)at modulation percentages of 100percent sync and 75 percentblanking.

The wattmeter will read in aver-age power, so a factor of 1.68 mustbe used in the calculation to obtainpeak power as is read on the trans-mitter power meter. Thus, Pay x1.68 = Ppk.

The factor of 1.68 is based onthe duty cycle and pulse widths ofthe modulating signal and their re-lationship to peak power. It is im-portant that the pulse widths becorrect and that the current modu-lation percentages are maintainedduring the calibrations.

At 100 percent modulation, thecarrier disappears (in amplitudemodulation). Disappearance of thecarrier would represent zero outputfrom a diode detector. Thus, tosimulate this condition when moni-toring with an oscilloscope, a chop-per is used to short out therecovered video signal at repeatedintervals. This will produce a

straight line display across the scopeand give a reference base line forthe modulation percentages.

Start by connecting the load andwattmeter at the output of the filterunit. This filter unit is consideredas part of the visual transmitter.Leave the aural transmitter turnedoff.

If the dummy load is watercooled, it is important that the water

flow begins before power is applied.Without water flow, the load wouldsoon be damaged.

Calculate what average powerwill be required at licensed poweroutput, 80 percent and 110 percent.Increase the transmitter output untilthe wattmeter reads the correct aver-age power. At the same time, usingthe chopper and observing the oscil-loscope, make certain that the cor-

Fixed 2.5 Kw air cooled load and thru line wattmeter. It is shown herebeing used as a reject load on a diplexer.

Water cooled 25 Kw UHF load and thru line wattmeterconnected to a coax patch panel.

July, 1970 29

rect percentages of modulation aremaintained. At this point, the engi-neer will normally find that he hassome juggling to do; that is, a com-bination of adjustments of sync andblanking levels and transmitter out-put. The correct modulation levelsand average power must occur atthe same time.

Once these are correct, observethe transmitter power meter. Itshould read 100 percent. If not,change the calibration controls toread 100 percent. Lock the controlsin place.

Now record the Ep and Ip of thefinal stage, or the total Ep and Ipif more than one stage is used. Thenext step is a measurement at 80percent and 110 percent power. Dothis by changing the transmitter out-put controls until each is reached.The wattmeter should read the aver-age power for 80 percent and 110percent. If the transmitter meterdoes not indicate these percentagescorrectly, mark the meter wherethey do occur.

The dummy load and wattmetershould be removed and replaced bythe line and antenna. Go througheach of the power points and recordthe final Ep and Ip at each powerpercentage. The readings should beessentially the same as those withthe dummy load. If they do notagree, there is something wrongeither with the load or with the lineand antenna. Line or antenna prob-lems will quickly show up as highVSWR and ghosts in the picture.

You may think that going throughthe measurements again on the lineand antenna is useless effort. Thisprocedure does two things: first, itwill reveal problems with the lineor antenna since a correctly oper-ating line and antenna will matchthe line impedance so should putan equivalent load on the transmit-ter as did the dummy load; secondly,it serves as a reminder to restorethe line and antenna to the trans-mitter so that the morning man willnot be programming to himself.

On Pleasing EveryoneSeveral years ago in a small

eastern UHF station the chief engi-neer was having difficulty makingfull visual output. The tube wasgoing sour and there was no betterspare available. The station was hav-ing cash problems and the chiefhad tried to convince the ownerthat money must be spent for anew tube. The transmitter andstudios were combined, so manyon the staff could see that the out-put meter was reading far from fulloutput - for which the chief re-ceived much criticism. As he putit, "Everyone from the owner downto the janitor is a meter reader."Tired of the criticism and failureto get the needed tube, he simplyadjusted the output meter until itread 100 percent. Everyone washappy, but the output power con-tinued to decrease until viewers inthe city (2 miles away) started com-plaining that they were not gettinga signal from the station. At thatpoint, he got the new tube.

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England's ITA tookour integral cavity klystrons.

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That's why our integral cavity tubes wereselected to power ITA's twenty-four transmittersdirectly from solid state drivers. (Since launch-ing its pioneer UHF color telecasting throughoutthe UK last November, ITA's network has grownto twelve stations.)

Not that Var an was any stranger to the busi-ness. Since biilding the first UHF TV klystron in1955, Varian has made more of them-over 1500

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Circle Reader Ser./ ce Number 41.

Line surgeprotection for remoteFM stations

PLATE CONTACTOR PLATE TRANSFORMER

LINE

O

0

1201

TRANSMITTER

OVERLOADS

1(12 -1(16

T202

3 CYCLE

OVER LOAD

SYSTEM

REMOTE

RESET

dfoOVERLOAD

AUXILIARY

of

OC.

1

T203

PJC31-1

TO CONTROL

VOLTAGETO PLATE

INTERLOCK

K4

By Tom German*

*President of Professional Electronics and ChiefEngineer of KCFA-FM, Spokane, Washington.

Aside from the fact that it wasideally situated for maximum cov-erage, the most important factor inchoosing our FM transmitter sitewas that there was a high poweredradar station operated by the AirForce and the FAA only a thousandfeet away. This gave us the assur-ance of an adequate, reliable powersource on our remote mountain top.The power source was of particularimportance because we would notbe able to afford standby gener-ators in the forseeable future.

It was this reliability factor whichgave us our greatest problem in theinitial months of operation. Aftermuch checking, hunting and manytrips up the mountain, we foundthat the radar station personnel, ac-customed to being alone on the endof the power line, were in the habitof dumping over 300,000 watts onthe line every time they checkedout their standby generators. Thisnormally takes place once a week,but just after we first went on theair, it was happening several timesa day. And did we have troubles!We arced, sparked, and flashed ourway through each broadcast day.

After a few calls to the powercompany and the radar personnel,we got their assurance that all futuretesting and switching would be doneon a slow transfer basis in orderto enable the power company's reg-ulators to act. But assurance couldbe given that, under failure condi-tions, we would no longer receivetransients up in the thousands ofvolts on our 230 volt line. Thesesurges had power behind them andwere really raising havoc withdiodes, capacitors, transformers,meters, circuit breakers and evenresistors.

According to power company en-gineers, some of these surges werestill over 200 percent of line volt-age, some 45 cycles after initialsurge. This is when their regulatorskicked in.

Surge ProtectorsWe tried commercial lightning

arrestor type surge protectors on theFig. 1 Schematic of the first circuit using a PJC31 in the plate transformer primary. power line. Then we tried thyrec-CR1, CR2, CR3, T201, T202, and T203 have been added to the original circuit. tors, which were supplied by the


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July, 1970 33

transmitter manufacturer. Bothtypes of surge protectors did seemto hold down the extreme peaks,as we had less arcing, but sincethese allow 150 percent or morevoltage before any appreciable lim-iting, there was still considerable

over voltage for relatively long timeperiods.

The use of surge protectors alsohad the disadvantage of constantlypoping circuit breakers which werenot resetable by remote control. At50 miles per trip and with some

LINE0

PJC31-1

o

CR4

CRS

CRe

CONTAC1OR

CONTROL

CF F LAMENT

115

CR7 r

RI

CR8

+24V0

00

R E3

RE4

0

RESET

O oSIN1

REMOTE RESET

BREAKER

CAM

R E5 C")

-rSTEPPER

Fig. 2 Over -voltage circuit for the transmitter, audio and microwave gear. CR4, CR5,and CR6 give added transient protection and help Ooad the circuits for the over -current relays.

damage still being done to the trans-mitter, we soon concluded that whatwe needed was an instantaneoustype of protector, preferably allow-ing remote recycling.

Instantaneous RelaysAfter a long search, I found that

GE makes an instantaneous over -current relay that responds in 11/2to 3 cycles. The basic relay, modelPJC31, comes in several wiring con-figurations to meet specific needs.The armatures are adjustable overa 1 to 4 pickup range so they canbe set to critical overcurrent re-quirements in the field. The cost ofthree-phase units was about $270each.

Figure 1 shows the installationof the first PJC31 in the platetransformer primary. For currentthis heavy it was necessary to usecurrent transformers, T201, T202and T203 at about $30 each. Withover -current conditions, the over -current relay or relays close, sendinga pulse to the regular three cycleoverload circuit in our 20 kW CCAtransmitter. Thus, when a voltagesurge hits, the plate contactor isopened for 1 second, then is re -closed. By this time the power com-pany's regulators have had time toremove all trace of over -voltage andwe continue on the air with just a1 second break.

The thyrectors Crl, Cr2, and Cr3give added transient protection andhelp to load the over -current relays.We used IR's Clip -sell, KL11DBFat about $11 each. These are ratedthrough 250 amps, while the PJC31relay we have picks up at as low as2 amps. The continuous currentrating is 6 amps. The one secondrating of the overload coils is 275amps.

Installation ProtectionThe instantaneous relays proved

very effective, but there was no pro-tection for low voltage circuits.Figure 2 shows the overvoltage cir-cuit we installed for the entire trans-mitter and even the rack of micro-wave and audio gear. We installedthyrectors, Cr4, Cr5, and Cr6 foradded transient protection and tohelp load the circuit for the over -current relays.

In this application, the PJC31 iswired in series with the 230 voltprimary lines. The armature of each


coil is adjusted in service for opti-mum protection, and one set of con-tacts of the PJC31 is changed tonormally open operation. ContactorRel operates on 24 volts DC andthe resistor RI and capacitor Clare a time delay network while Cr7shorts through the N/O contacts ofthe PJC31 to allow for instantan-eous opening upon overload.

Re2 is a stepping relay, countingthe number of overload cycles.Eight cycles will turn off the trans-mitter until the overload is reseteither at the transmitter or by re-mote control. Time delay relay Re3resets the stepping relay to "start",if less than 8 cycles have occurredwithin two minutes.

The filament time delay relay inthe transmitter drops out in about5 seconds. Any problem of longerduration necessitates waiting for atwo minute time -delay before thetransmitter is restored to the air, butthat is better than the hour it takesto drive up the mountain.

Additional AC CircuitsT115 was installed in order to

achieve powerline isolation andtrue one -point ground and to pro-vide circuit protection for ourmicrowave, control, telemeteringand audio circuits. We also added abattery and an inverter as an emer-gency power supply for telemeteringcircuits for remote trouble shootingpurposes. We can isolate most prob-lems to specific areas remotely,even if overloads or circuit breakersare open . . . a considerable savingin diagnostic and driving time.

Our ideal site gave us nothing butheadaches at first, but our final cir-cuit greatly simplified our opera-tion. That's why we also installed asecond over -current relay. It mayseem to make the first unnecessary,but, as installed, it makes an excel-lent remote resetable breaker andoffers faster protection than theoverload protection supplied withthe transmitter. It is also a redun-dant protection for expensive highvoltage components.

We have had no equipment dam-age or outages in the last year dueto surges of any type. And just asimportant, we have complete con-trol and monitoring possibilities andour protection circuits are resetableby remote control.

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Fig. 1 A41 kHzSCA used as an AMbackup STL.

Fig. 2 Inserting1000 Hz tone foradjustment ofmodulation at100 percent on thesubchannel.

SCA principles andpractices

41kHz SCA

I

AM - FM STUDIOSAND

FM TRANSMITTER

SCARECEIVER I

REMOTE -CONTROLLED

AM TRANSMITTER

1000Hz

TAPE

1000Hz

AUDIOGENERATOR

AUTO

SWITCHER

MAIN -CHANNEL

CONSOLE

DEFEAT AGC

ACTION

AGC

AMPLIFIER

LIMITER

SCA

GENERATOR

DEFEAT LIMITINGACTION

FOR STEREO, FEED TONE INTO L INPUT ONLY.LEAVE PILOT GENERATOR ON.

TRANSMITTER

SCA

MONITOR


By T. R. Haskett

An SCA subchannel is sometimesused to relay news or sports toother FM and AM stations. Thismode is occasionally useful whenan AM station is the key for a base-ball network, but when its affili-ated FM station is programmedseparately and does not carry base-ball.

An ingenious use for an SCAsubchannel is shown in Figure 1.

The studios of commonly -ownedbut separately programmed AM andFM stations are located at the samesite as the FM transmitter. TheAM transmitter is remote -controlledand located at another site, andthe normal AM program line is aTelco circuit. An SCA subcarrier isavailable as a backup.

What is even more interesting isthat the FM station can normallyprogram stereo, and use a 67 kHzSCA for paying subscribers. A 41 -kHz SCA is used as the AM backupSTL. When the backup is needed,the FM station simply kills its 19 -kHz pilot generator (thereby elim-inating its stereo sideband channel)and turns on the 41 kHz SCA gen-erator. By remote control, at thetransmitter site the SCA receiver isswitched to feed the transmitter.

A further use for SCA is to tele-meter a remote -controlled FMtransmitter back to the studio. Youneed a wire line or STL to controlthe transmitter, but you don't needa return line to take transmitterreadings. The required readings areconverted to audio tones in therange of 20-40 Hz and transmittedon the SCA subchannel. Withproper filtering, you can providebackground music or other sub-scriber service on the SCA, andtelemeter back your own transmitteron the same subchannel.

RequiredTest Equipment

To install and maintain an SCAsystem, certain instruments arenecessary.

1. Main -channel frequency andmodulation monitors, and SCAmonitor. These are required bythe FCC.

2. A high -impedance electronicvoltmeter (VTVM or FETVM).

3. An oscilloscope with verticalfrequency response from DC toabout 5 MHz, and a low -capacitance probe.

4. An audio generator with nomore than 0.1 percent har-monic distortion in its output.

5. A harmonic distortion meterwith no more than 0.1 percentinternal distortion.

6. A wideband FM detector.7. An AM noise measuring set.8. Two dummy loads - one for

the main transmitter and onefor the exciter.

9. A wattmeter, to check trans-mitter power output and effici-ency.

10. A frequency counter. Obvi-ously, this is an expensive itemwhich few stations have used.It is, however, becoming essen-tial if you do anything beyondstraight mono FM broadcast-ing. If you are both stereo andSCA, a counter will be usefulin making daily frequencychecks of the pilot and SCAsubcarriers.

An accurately calibrated com-munications receiver is also useful.With it you can use Bessel functionsto check your modulation moni-tor(s).

System OperationAnd Maintenance

Having made the decision to getinto SCA, you will get FCC per-mission, buy the equipment, and getto work rounding up subscribers.But you cannot simply connect theequipment and expect everything towork properly. As Murphy's Lawstates: "In any endeavor, if any-thing can go wrong, it will."

From the standpoint of trouble-shooting, it makes no differencewhether you are setting up an SCAsystem or keeping it operating. Themost common problem is crosstalkin the SCA subchannel-crosstalk

which comes from the main channelor the stereo sidebands-crosstalkwhich annoys your subscribers andgenerates complaints.

Obviously the entire SCA system-from tape deck to subscriberspeakers-must be operating prop-erly for everyone to be happy. Whencrosstalk occurs, however, it usuallyleaks in at only one point in thesystem.

Actually, creeping crosstalk some-times occurs at several points in thesystem. You may find 5 dB ofcrosstalk here, 4 dB there. Thetotal is enough to seriously worsencrosstalk and S/N. But you stilltroubleshoot by cleaning up eachpiece of gear in turn.

To localize crosstalk, it's con-venient to divide the overall systeminto two separate subsystems: thetransmitting gear and the receivinggear. Fortunately, there are twoseparate monitoring instrumentswhich permit you to divide the over-all system into two parts. These arethe SCA monitor and the client'sreceivers. If you hear crosstalk inthe monitor, it's getting in at thetransmitting system. If you can'thear crosstalk in the monitor, butyou can at the receiver, it's gettingin at that receiving system.

The SCA MonitorThe monitor is the prime refer-

ence for the SCA system. It isessential that the monitor be freeof internal crosstalk, and that itperform all indications within ratedaccuracy. If you have any doubtswhatsoever about the monitor, writethe manufacturer for instructions.He may instruct you to performsimple field checks, or he may haveyou return the instrument for over-haul and recalibration.

The monitor is the readout indi-cator you will watch while trouble-shooting the transmitting system. Ifyou have leased the SCA to anoutside contractor, what you seeon the monitor is the last you willsee of your signal.

Crosstalk LocalizationHere is a relatively simple method

July, 1970 37

for checking each element in theSCA system. It must be performedwhile the station's normal program-ming is off the air. Of course, allthe equipment-including the trans-mitter-must actually be on.

Referring to Figure 2, if youwant to establish the 100 percentmodulation point on the SCA sub -

channel, make up a test tape con-taining several minutes of 1000 Hztone. Run this on a tape machinewhich is normally used to feed theSCA audio line. Defeat any com-pression or limiting action, but leavethe compressors or limiters in thecircuit as straight amplifiers. Try tokeep all attenuators at their normal

settings, but adjust gain so that SCA -

modulation (deviation) is at thenormal 100 percent point. Depend-ing on your particular practice, thismay be a deviation of ±7.5, 5, or3.5 kHz.

With the tape still running andSCA modulation at the 100 percentpoint, set the SCA monitor to take

SCA Generators

Mar ufac'L rer Model No. Unit DesignFrequenciesAvailable

Center Freq.Stability

AEL 2204 Self-contained 30 through75 kHz

±400 Hz

Bauer 7566,68 Plug-in unit 41 or 67 kHz ±500 Hz

Collins 786W-1 Plug-in for Collins310Z-1 Exciter

67 kHz only ±0.2% 50-15,000 Hz

Gates M-6160* Plug-in for GatesM-6146 Stereo Gen.

Any, 25-75 kHz ±500 Hz 30-15.000 Hz

Gates M-6507 Plug-in for GatesTE-1 Exciter

Any, 25-75 kHz 1_500 Hz 30-15000 Hz

Marti SCG-67 Self-contained un t 41 or 67 kHz only 5J() Hz 40-6,000 Hz

Moseley SCG-4- Self-contained un t Any, 25-90 kHz ±0.5% 30-12,000 Hz

RCA BTX-1B Plug-in for RCABTE-15A Excite-

Any, 30-75 kHz -±0.2% 30-10.000 Hz

Vacaum-tube model supplied far existing transmitters. Not recommended for rew installations, having bee,, superseded by M-6507.


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July, 1970 39

a crosstalk reading. Then stop thetape, but don't disconnect or turnoff the tape machine. When thetape stops, the head won't pick upany signal. You don't want programmaterial going through the SCAsystem, but you do want everypiece of equipment in the chain andoperating. Be sure to defeat SCAgenerator muting.

Now feed a 1000 Hz tone froman audio generator into the mainchannel, preferably as far back to-ward the system input as possible.The ideal place is the announce -microphone jack on the console.Defeat any compression or limitingaction in the main channel, butleave the compressors and/or limit-ers in the circuit. Adjust main -channel modulation to about 2 per-cent less than the maximum allow-able level for your mode of oper-ation.

Check SCA injection level andbe sure that it's at the proper value.

make sure it does not exceed 98percent.

If you are operating stereo, leavethe 19 kHz pilot on, and feed the1000 Hz tone into the left channelonly. Short the input of the rightchannel preamp at the console. Thisis the worst -case test of a stereosystem, since you are transmitting aleft -only signal, with half the infor-mation in the main channel andhalf in the stereo sidebands. Bothcan cause crosstalk in the SCA.

(A left -only signal is not onlyworst -case, it is somewhat unreal-istic and doesn't occur very oftenin stereo programming. If you can-not get an acceptable crosstalkfigure on the SCA with a left -onlysignal which modulates the mainL R channel to the legal maxi-mum of 40 percent, back it off alittle. The SCA may still have a bitof crosstalk, but only on extremeleft or right main -channel program-ming.)

You should now take a crosstalkreading with the SCA monitor.There is no modulation on the SCAsubchannel, but there is nearly max-imum modulation on the mainchannel (and on the stereo sub -

channel, if you are stereo). There-fore, anything you read on the SCAis crosstalk. If you are lucky, it willbe about 50 dB below the 100 per-cent modulation point, which is justabout the best obtainable figure foran SCA. Most likely you will findthe Cx about 40 dB down, whichyou can live with. If Cx is only-30 dB, you have trouble.

Reading CxSome SCA monitors include a

function which indicates crosstalkin dB below 100 percent SCA mod-ulation. Others don't. If yours isthe latter type, you will have touse the following method of readingCx. Feed the SCA monitor's audiooutput (the one marked "for dis-tortion measurements") to a har-monic distortion meter. Then simplyset level at the HD meter using 100percent SCA modulation by the testtape. Finally, remove the modula-tion and read Cx on the HD meteras residual noise. In this process,it's a good idea to hang a scopeacross the HD meter output andobserve exactly what the Cx wave-form is. It should be some com-ponent of the 1000 Hz on the mainchannel.

Obviously, the main channelnormally contains frequencies otherthan 1000 Hz. Therefore you shouldmake a frequency run, taking cross-talk readings with main -channeltones at several points between 50and 15,000 Hz. Readjust main -channel modulation at each tone sothat total modulation does not ex-ceed 98 percent.

Refer again to Figure 2. Firstyou will check the audio elementsof the transmitting system, by short-ing out each in turn and noting ifthe crosstalk gets better or worse.First eliminate the tape gear fromthe system by shorting the input tothe AGC amplifier. If Cx was -30dB before and is now -40 dB, thetape gear is at fault. If Cx is still-30 dB, the trouble is farther alongin the chain. Do the same with anyother units in the chain.

Finally, short the audio input onthe SCA generator. If crosstalk re-mains the same, it's getting in downthe line.

Still keeping the SCA generatoraudio input shorted, connect its RFoutput directly to the SCA monitor.Turn off the main -channel exciterand power amplifier. If the cross-talk figure remains substantially thesame, the trouble is in the SCAgenerator. But if Cx goes from -30dB to -40 dB (or something sim-ilar), the trouble is in the trans-mitter, line, or antenna.

Reconnect the SCA generator tothe main -channel exciter. Discon-nect the exciter RF output fromthe power amplifier, and terminatethe exciter in a dummy load. Besure the power amplifier is off, andcouple the SCA monitor samplingline to the dummy. Now you haveisolated the power amplifier, line,and antenna by removing them fromthe circuit. If crosstalk remains, itis in the exciter; if it doesn't, thetrouble is in the PA, line, orantenna.

Reconnect the exciter to the trans-and terminate the transmitter

in a dummy load. Reconnect theSCA monitor to sample normaltransmitter RF. Again you haveeliminated the line and antenna,and are including only the poweramplifier. If crosstalk is reducedwhen driving the PA dummy load,the trouble must be in the line orantenna.

You don't need to go to suchlengths to check the receiving sys-tem. Since you have many receiversand receiving antennas, you can al-ways check one against another. It'sa good idea to have at least onewell -aligned receiver driven by onewell -installed antenna as a refer-ence. Some chief engineers installan SCA receiver at their home forthis purpose. If you've leased yourSCA to an outside contractor, hismaintenance technicians will havesuch a reference system on theirtest bench.

Now your have seen how tobreak the system into its componentparts. In the last part of this series,we will cover specific problems andsolutions in audio origination equip-ment, the SCA generator, the ex-citer, transmission line, antenna,and the receiving installation. A


SCA Monitors

Manufacturer

Usable SCA 100% SCAoperating modulation

Type No. Use frequencies indicated at Indicates

Belar SCM-1

0 Luz MONII (-)

Plug-in forBelar FMM-1main-ch. mon.

Any 4 from24-74 kHz

2, 4, or 6kHz deviation

SCA freq.SCA mod.SCA inj.Cx in SCA

SCAmod.peakflasher

Yes

Collins 900E-1

4111111-tr-itio Plug-in for 67 kHz only 5 or 10 SCA freq. NoCollins 900C-2, kHz dev. SCA mod.900C-3, 900C -3Amain-ch. mons.

Gates GTA-6741 0 Plug-in forGates GTM-88M,GT M -88Smain-ch. mors.

41 or 67kHz only

5 or 7.5 SCA mod. YeskHz dev. SCA inj.

Cx in SCA

McMartin TBM-2000APlug-in forMcMartinTBM-4000A,TBM-4500Amain-ch. mons.

Any 2 4 or 6 SCA freq. YeskHz dev. SCA mod.

SCA inj.Cx in SCA

McMartin TBM-4000A Self-contained Any 2 4 or 6 SCA freq. Yesmono/SCA mor. kHz dev. SCA mod.

SCA inj.Cx in SCA

RCA BW-95A

Plug-in for Any 4 from 2, 4, or 6 SCA freq. YesRCA BW-75A 24-74 kHz kHz dev. SCA mod.main-ch. mon. SCA inj.

Cx in SCA

*GTA-88F Pilot SCA Frequency Comparator required as accessory to measure SCA frequency.

July, 1970 4I

Feeding andControllingCarrierCurrentTransmitters

Campus station WRST-FM solvedtheir campus limited transmitterproblems by using the old"Phantom Circuit".By John A. Bredesen, P.E.*

BOOSTER

AMPLIFIER

OUTPUT

TRANSFORMERTELEPHONE

LINE

4. CENTER

TAP0 ON -OFF

SWITCH

EARTH

GROUND

EARTH

GROUND

DORM

TRANSMITTER

INPUT

TRANSFORMER

Fig. 1 On/Off control was achieved by using an old "phantom" circuit. The currentequally divides to both sides of the output transformer terminals.

The Wisconsin State Universityat Oshkosh has had for severalyears a student operated radio sta-tion, WRST-FM. It began as a 10watt educational station serving thecity of Oshkosh, but as the numberof students living on campus in-creased, we decided to install a"Carrier Current" or limited fieldtransmitters in the dormatories toenable students to listen on conven-tional AM receivers. Equally per-suasive, a survey of the residentstudents indicated that only 25 per-cent owned FM receivers.

Our student enrollment of about11,000 is served by six low poweredtransmitters covering 14 dorms,with additional dorms planned forthe future. This number of trans-mitters posed two problems at in-stallation time, the solutions ofwhich are the subject of this article.First was the problem of feeding thesix audio lines (we lease lines fromthe telephone company but will beinstalling our own in the nearfuture) with the proper impedanceand audio level, and secondly theproblem of controlling the ON/OFF function of the transmitters.

Feeding The TransmitterLet's look at the feed problem

first. A telephone line should beterminated with a nominal 600 ohmimpedance. Moreover, these linesfor best hum cancellation and noiseimmunity are balanced, meaningthat neither side of the line isgrounded, and the level into the lineshould be about +8 dBm. In ourcase, the dorm transmitter takescare of obtaining the proper condi-tions at the input end.

The audio board in most stationshas an output level of +8 dBm at600 ohms. This is just what we needto feed one line. It is obvious thatwe shouldn't simply parallel the sixaudio lines across the output of theboard because six 600 ohm linesparallel is not 600 ohms, but 100ohms.

One possible solution would beto use a series of "building -out"*Director of Engineering for Radio. Television andfilm at Wisconsin State University-Oshkosh.


WRST FM

AM BOOSTER Mr

kM TRANSWTTER

UAL

Fig. 2 Front view of the WRST-FM AM boos

pads or splitters. The trouble hereis that while we could maintain theproper impedance this way, wewould lose our desired signal level,and this is not good from the stand-point of signal-to-noise ratio on thetelephone line. It was decided to goto an audio booster amplifier toovercome these problems.

Transmitter ControlThe second problem, that of ON/

OFF control, is solved quite neatlywith this unit, using what is referredto as a "phantom" circuit. This isnot a new concept. It goes back tosome of the earliest days of openwire telegraphy! (See Figure 1.) Inthe phantom circuit 27 volts DCis applied to the centertappedsecondary of the output transformerthrough the switch controlling theON/OFF function. The currentequally divides to both sides of theoutput terminals of the transformer;therefore, it is equal on both sidesof each audio line.

Another way to understand thecircuit is to measure across theaudio pair with a voltmeter. Youwouldn't measure any DC voltage atall, whether the transmitters wereON or OFF. If, however, you wereto measure from either line toground, you would read the powersupply voltage, assuming that the

er amplifier.

transmitters were switched ON.At the transmitter proper, the

audio pair terminates in a balancedinput transformer which has acentertapped primary. The DC volt-age is available here to operate arelay to apply power to the trans-mitter. The control voltage returnto the station is through earthground, therefore it is imperativethat each transmitter and the distri-bution amplifier at the studio bewell grounded.

The reason the DC doesn't inter-fere with the audio signal is that theline is balanced to ground. The

audio signal is "push-pull" on theline while the DC is "push -push".Any hum or other noise introducedby the power supply will cancel out.There is, however, always the pos-sibility that some unbalance mayoccur; this is one of the reasons whyI used an electronically regulatedpower supply with an inherently lowhum and noise level.

The particular relay selected forinstallation at each transmitter is aPotter & Brumfield ML11D with a10,000 ohm coil. This is a highenough resistance to avoid a size-able voltage drop on the phone line.

114 A

NEON

PILOT

LAMP

TRIAD

F -25X MOTOROLA

MDA920 A-1

12 hlAt

TO

AMPLIFIER

) 1N4739A

Fig. 3 Power supply.

July, 1970 43

One of our lines is more than twomiles long by the time it is routedthrough the telephone central ex-change. It still works well. Whenordering the line, make certain thatyou specify the need for DC con-tinuity, otherwise the phone com-pany may put a repeat coil in theline which will block DC.

With this research behind me, Ibuilt a unit that would give the de-sired results (See Figure 2). I usedan amplifier that was commerciallyavailable rather than build one upfrom scratch. The one selected isa small solid state printed circuitunit manufactured by AmperexElectronic Corporation, ModelPCA-1-9. The price is reasonable(about $10), and the performanceis quite adequate for this purpose.Only one addition is required on thePC board and this will be discussedlater.

The amplifier has a rudimentarypower supply requiring only an ex-ternally mounted transformer foroperation, but the hum level is quiteunacceptable in this application.The regulated power supply solvedthis problem.

The power supply was designedto provide an output of 25 volts toallow operation of the transmitterrelays. However, the amplifier re-quires only 9 volts, so a 10 wattzener diode and a dropping resistoris used. An alternate power supply(See Figure 3) provides the required9 volts directly, if relay operationis not required in your installation.

Construction DetailsNo particular attempt was made

to build a compact unit. Ours isconstructed using a 51/4" rack paneland dish chassis, but it could bevery easily built using a 31/2" panel.

The circuitry (See Figure 4) isstraight forward. The amplifier ismounted with two spacers to therear side of the front panel in sucha manner that the gain control isaccessable through a hole in thepanel (See Figure 5). The amplifierspecified has mounting holes thatlend themselves to this type ofmounting.

The amplifier output coupling ca-pacitor has a value of 125 mfd, notlarge enough to prevent an undesir-able low frequency rolloff. Toremedy this, connect a 500 mfd, 15volt cap across the one supplied andsupport it with its own leads. Besure to watch polarity. Bypass thediode Crl on the amplifier, it isn'tneeded.

Construction of the power supplyisn't critical. Ours was built on per-forated vector board with com-ponents mounted by their own

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Fig. 4 Simple schematic of the booster amplifier.


leads, but the supply is simpleenough to construct using terminalstrips and point-to-point wiring ifdesired.

The 2N456A transistor 01, mustbe mounted on a heat sink with atleast 12 square inches of surface.Mount the heat sink so that thefins are vertical to allow maximumuse of convection cooling currents.A coat of flat black paint from anaerosol spray can on the heat sinkwill aid in heat rejection. Don't getany paint on the area where thetransistor will be mounted and besure to use a silicone heat sink com-pound to assure thermal continuityfrom the transistor to the heat sink.

While the input transformer T1,is rated 600 ohm to 600 ohm, thisunit, and indeed any other trans-former with similar characteristics,will reflect a 600 ohm load in theprimary only if the secondary isterminated in 600 ohms. Since thetransformation ratio is 1 to 1, theprimary will reflect a much higherimpedance because the secondary isterminated with a minimum of 220kohms. Therefore, the input of thebooster amplifier may be freelybridged across a 600 ohm line, bal-anced or unbalanced without anysignificant loading.

It isn't necessary that the outputof the booster be terminated withall 12 lines if you don't have thatmany to feed. The amplifier isn'tcritical at all within the range of 600ohms (one line) to 50 ohms (twelvelines). This means that from 1 to 12audio pairs may be connected atwill.

The VU meter (if one is used)will read accurately with any num-ber of lines connected, but it maybe necessary to adjust the gain aslines are added to maintain the de-sired level. The VU meter was in-cluded as an aid in setting the gaincontrol. It is not really needed ifsome other means is available.

Our booster has been in opera-tion for almost a year and has notrequired any attention in that time.It has fulfilled every design ob-jective and has done so with a verymodest original cost.

Fig. 5 The amplifier is mounted on a subchassis with a hole cut in the front panelfor access to the level adjust pot.

Fig. 6 Top inside view of the power supply station.

July, 1970 45

Burst phasing can bean operational adjustment

By Elmer T. Schorle, Jr.*

Of all the equipment in use inTV broadcast stations, none is moreinvolved in both production workand on the air revenue productionthan the videotape recorder. Be-cause of this dual role most stationsevolve a complex work load fortheir machines that sandwiches airplayback of spots between record-ing assignments, often utilizing everyavailable moment on each VTR'slog for one function or the other.

At WCAU-TV this means put-ting up for air playback an averageof 60 (and as high as 80) shortterm (60 seconds or less) playbacksper day, plus three or four half-hour shows which are either na-tionally syndicated or locally pro-duced. To help the operator get thebest color quality, these VTR's haveauto-chroma, Mincom color dropout compensation, velocity compen-sators, and vectorscopes and colormonitoring for each machine. How -

*Videotape Technical Director, WCALITV,Philadelphia.

ARIAELE DFLAY NETWORKTd NSEC 12<IOORESC CORP.NO 7441.PALISADES PARR N J

ever, if care is not paid to the burstphasing of each of these tapes, allthe other gear could be super-filous, as we would air flesh tonesranging from green to purple. Mean-while, the sponsors and publicwould match the colors as they lookon in disbelief.

The Ampex recorder does nothave a quick or easily accessibleadjustment for changing the burstphase. Ampex takes the view thatthis should not be an operating ad-justment. However, some of thetape coming out of productionhouses has not been subjected toquality control. When we run someof those low quality tapes, we needto make some adjustment or theflesh tones end up covering halfthe rainbow. Since we run as manyas 30 sources in one day, the chanceof getting a poor tape is high.

Realizing that we wanted theoperator to correct for impropercolor phasing, it was apparent thatto adjust it by the book often re-quired more time than he couldspare, and chanced a slipped screw-driver falling down through the procamp PC boards while trying to

quickly tweak the delay line. Thecontrol had to be as convenient andas quickly set as the other operatingcontrols and had to provide therange needed to cover variationsfound in tapes in our library.

After considering voltage con-trolled delay lines, and tapped co-axial delay lines, we rejected each,for cost and size reasons. We thenasked ESC Electronics Corporation,who makes the delay lines used inAmpex recorders, to blend two oftheir products to give us a 25 nano-second delay line with a 1/4" shaftfor a knob. This would give us arange of plus or minus 22 degrees,with a five -turn control, and wouldamply cover our needs.

Electrically, the unit is placed inseries with the burst routing fromthe colortec to the proc amp. Me-chanically, we chose to mount it insignal system jumper module num-ber 8. The spare coaxial jack, andthe unused "'RP Dub In" jack onthe rear of the signal system wereused for the cables. Terminating thedelay line drops the burst levelsome, but it means only that theproc amp burst gain must be set at

COLORTEC

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PROC. AMPLIFIER

BURST IN

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MODULE 8 (PARTIAL)

Fig. 1 View showing mounting of the delay line Fig. 2 WCAU-TV's wiring plan, with the delay line inserted in the burst pathwithin the jumper module. Actual pin wiring from Colortec to the proc amp.would depend upon individual preference it theVR1200 or VR2000.


Fig. 3 Rub -on type lettering was used on the front of the module. Covered with athin lacquer, the lettering blends with Ampex's lettering.

about the 1:30 o'clock position in-stead of straight up in order to get4 IRE units of burst again.

We align the system by puttingthe 5 -turn control in the middle ofthe range, and adjust the proc ampdelay line for zero shift thru themachine. Then when the control isreset for a spot, it is quick and easyfor the operator to come back tostandard phasing after it airs.

Thus, for $67 per machine, wehave added a convenient operatingcontrol that aids in maintaining bet-ter color quality. We have not yeteliminated all the grumblings thatall non-standard tapes should be re-jected by sales (who ever heard ofsales rejecting spots for electronicquality). At least now, by the timehe has grumbled, he is also finishedcorrecting it, instead of still beingin the act of trying to find the slotin the proc amp delay while hewatches the monitor or vectorscope.

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"combo" working.All signal inputs and outputsare on XLR connectors at therear.Thus the BCM 10/2 providesfor every possible requirementwithin its class. It is com-petitively priced and availablefor quick delivery. Full speci-fications on request.

July, 1970 47

Television:A long range forecast

At a time when we are all seeking tocrystalize at least the goals of television,scientists are signaling even greaterchallenges from a distant horizon.

By Dr. Dennis GaborC.B.S. Laboratories

The following is a paper de-livered to the NAB convention inChicago this year. While BroadcastEngineering does not necessarilyagree with all Dr. Gabor says, wethink it is important to bring thesubject to the attention of thebroadcast/communications indus-try. The Editor.

I wish to give an outlook intothe scientific -technological possibili-ties of television. As a scientist Iwill take the liberty of not botheringtoo much about the economic vi-ability of some of these excitingprojects, but I cannot leave it quiteunmentioned. Everybody knowsthat it takes 10-20-30 years afteran invention has proved technicallyfeasible, before it becomes an "in-novation", that is to say it can besuccessfully marketed.

The popular belief is that thistime is required for the engineeringdevelopment, for pilot manufacture,for debugging, but this takes usu-ally only 5-10 years. In most casesthe delay is caused by finding theeconomic -financial basis for suc-cessful marketing. The technicalfeasibility of television was demon-

strated in 1928 by Zworykin. Ittook only 8 years for a televisionservice to start in Britain, where itwas financially based on a publiccorporation, the BBC. In the USAit took 20 years, because here thefinancial basis had to be createdby advertisements. If later on Ispeak boldly about some technicalprojects, I certainly do not under-rate the difficulties created byvested interests and habits.

British television started in 1936,with 405 lines. The USA leap-frogged this in 1948 with 525 lines.Continental television leapfroggedthis again with 625 lines, and Bri-tain had to follow suit. Millions ofAmericans have seen the superiorContinental services, and it is fairto expect that the USA will jumpto the front again, with somethinglike 750 lines, which would be asgood as perfection at the presentscreen sizes. In the case of colorthis would mean stretching theexisting techniques a little, but ev-erything is ready, except that we donot know where to take the 10 MHzwaveband which would be required.

Cassette TelevisionThere may be also another way

by which high -quality pictures canappear in the homes. There can be

no doubt about the great future of"cassette television", which is nottele-vision at all, but a customer -controlled visual display, analogousto the phonograph; the EVR ofCBS, the video tape of Sony -Philipsand the SELECTAVISION ofRCA. There is no difficulty in mak-ing these good enough for 750 oreven 1000 lines. For some years ofcourse people will use these withtheir ordinary TV sets, but it isprobable that in not too many yearswide -waveband sets will becomeavailable for office communications,and this may open the way for highresolution EVR devices. This inturn may encourage entrepreneursto speed up the development ofhigh -quality cable television net-works.

Let us now look farther ahead,towards large screen television, say4 ft. by 3 ft. 750-1000 lines wouldbe sufficient for these too, if peoplewould view them not from the usual4 ft. distance but about twice asmuch. Assuming that the wave-bands of 10 MHz will be availableby that time, the bottleneck will bein the display device. There are fourpossible solutions which I willdiscuss.

One solution is ready; it is theprojection system based on the Ei-dophor tube, and its improvementsby Dr. W. E. Glenn, Jr. It is perfect,but far too expensive for the home.

A second solution is the ingeni-ous image amplifier of Prof. Bau-mann of the ETH, Zurich, who wasalso one of the chief architects ofthe Eidophor. This too appears tobe far too expensive for the home.

A third solution has been muchtalked about for the yast 20 years.It is the "solid state" televisionscreen, composed of electro-lumi-nescent elements. In spite of theenormous amount of work done onsolid state physics, I do not thinkthat we have got much nearer toit in 20 years. The brightness ofthe electro-luminescent substancesis still so low that they would haveto be excited during the whole timefrom frame to frame, not during afew millionth of the time, like ca-thodoluminescent powders. Hence


each element of the screen wouldhave to be a device which feedspower into the electro-luminescentsubstance during the whole time,proportional to the signal which ithas received. Any electronic engi-neer can construct such a device,but I can hardly believe that itcould be done at 0.1 cents apiece,which would put a screen with afew million elements into the thou-sand -dollar range.

The possibility of a fourth sys-tem is just becoming visible. Anexciting new invention has just beenannounced; a glass fibre whichamplifies the light passing throughit by laser action. If it were possibleto produce such amplifying fibresfor the three basic colors, one couldthink of a large screen composedof glass fibres which lead to asmall, conventional color tube,amplifying the light on the way tothe large screen to full brightness.

Future RequirementsLet us now take a further step

into the future, towards the all -wall,three-dimensional television screen,the favorite of the science fictionwriters. We can perhaps believe init, if we believe in Herman Kahn'sextrapolation into what he calls the"Post -Economic Society" in whichthe G.N.P. per capita of U.S. citi-zens will be in the $20,000-100,000bracket. But let us leave economicsaside, and look into the technicalproblem. The waveband require-ment is not insuperable. We havecoaxial cables with 100 MHz band-width, and helical waveguides with1000 MHz. This would be enoughfor an all -wall two dimensional pic-ture. But the 3D feature is verydoubtful. Holography has beenoften mentioned as an exciting pos-sibility, and holograms are indeedreal three-dimensional pictures, butat what an expense! Even withpresent-day screen sizes a 3D holo-gram would require at the veryleast a 100 MHz waveband, and atthe receiving end it would requirea large Eidophor with strong lasers.For color pictures one would re-quire three lasers, because we havenot yet a medium for producing

erasable volume holograms, whichcould be illuminated with whitelight.

So it would be an enormoustechnical tour de force and verycostly to produce a 3D televisionpicture of the present-day size, butthe crux of the matter is that itwould not be worthwhile. I have,long ago, played about with 3Dprojection and it was very impres-sive in cinema size. But when I

tried it in television size, the resultwas pretty, but one could not takeit seriously. It was like a puppettheatre! As soon as one asks arealistic feature to a picture, theeye asks for more; for real dimen-sions.

So, to my regret, I cannot be-lieve in full 3D television, exceptin the remote and rather unlikelyfuture, the post -economic society,in which people will be willing tospend about as much on entertain-ment as they now spend on every-thing put together. Perhaps theywill be satisfied with cheaper sub-stitutes, with stereoscopic pictures,viewed through Polaroid spectacles,but this is rather unlikely.

Ultimate FocusFinally, I wish to say a few

words about television (and visual)displays in general) as a culturalmedium. We do not need MarshallMcLuhan to tell us how importantit is. Until he goes to high schoolthe American boy or girl has spentmany more hours watching tele-vision than doing school work. Heor she has formed many of hisviews on the world from television.

The American television net-works are doing admirable work inentertaining children and are facedwith a growing responsibility toplay a more vigorous role in edu-cating them as well as entertainingthem.

Unless we can harness all theidealism of which young people arecapable and direct it into construc-tive channels, I do not think thatwe need worry much about all -walltelevision in the 21st Centry. Bythat time there may not be evensmall black -and -white sets!

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July, 1970


49

Film Systems In CATV"The most meaningful area of activity

is your ability to originate truly local pro-gramming along with local advertising."

By Tom Levy, Eastman Kodak

"The CATV industry is going tohave a profound effect on the wholefield of communications . . . andwe want to furnish you with a bet-ter understanding of the potentialof the film system for cable TV."

The man speaking was Dr. Nor-wood Simmons, assistant vice-pres-ident and general manager of theMotion Picture and Education Mar-kets Division, Eastman KodakCompany. His recent appearance(5/6/70) before more than 100cablecasters at the PennsylvaniaCATV Convention in Lancasterunderscored Kodak's interest in thecapabilities of cable TV.

"Cable television has a potentialfar beyond that of simply providinga signal from a distant TV station,"Dr. Simmons said. "As a result, thelocal scene already is being re-flected by several cable systemswith some very effective local origi-nation."

Citing the strength of the indus-try, Dr. Simmons pointed out thatwhile the Gross National Producthas been growing at a 7.8 percentrate, the CATV industry, over thepast five years, has shown a com-pound growth rate of 13.5 percent.

"We challenge anyone to nameanother industry that has come sofar, in the face of so many an-tagonists," he said.

Dr. Simmons then went on tocompare the film system, oftentaken for granted by TV people,with the newer, and therefore moreglamorous, technology of videotape.

He asked his listeners to reversethe present situation and imaginethat CATV systems had availableonly videotape for all programming

other than live transmission or ma-terial picked up directly off the air.

"Then," he said, "suppose youheard about a remarkable discoverythat offered a complete system forproducing program material, requir-ing fewer components, less expen-sive equipment, smaller and moreportable pieces of hardware, fewerskills to operate, worldwide stan-dardization, easier editing, andcomparable, if not superior, colorfidelity.

"Furthermore, this system couldrecord events under extremely dif-ficult conditions, and could produceeither black -and -white or color pro-grams. In short, it would improveon virtually every characteristic ofthe videotape system except for one-it would require a more complexprocessing procedure. As youknow, I've just described the char-acteristics of the film system."

Pointing out the importance offilm in broadcast TV today, Dr.Simmons noted that some 85 per-cent of prime time TV is on film,and at least 90 percent of networkcommercials are on film.

Artistic FlexibilityDr. Simmons commented that

while simple commercials, producedby local stations, are, for the mostpart, on videotape, film is the me-dium of choice where a commercialcalls for realism, artistic flexibility,outdoor shots, and rapid switchingof scenes.

As for programming, he said,film is hard to beat "if the situationcalls for lively physical action ofeither the subjects or the camera-man, if there is going to be any

editing, and if your crew totals onlyone or two people."

He added that videotape hassome definite plus values, especiallyif immediacy is essential. "We be-lieve that tape will exist side -by -side with film," he said.

Dr. Simmons then turned his at-tention to the basic equipment foran effective film system for cableTV. He counseled his listeners that16mm film and 16mm equipmentwill continue to be the most widelyused film format in television.

8 vs. 16mmCiting the current discussion

about the potential of Kodak'ssuper 8 film format for TV, hesaid:

"We haven't the slightest doubtthat super 8 is going to find aplace in both broadcast TV andCATV. For anyone, however, togo into super 8 exclusively now,on the assumption that they are onthe wave of the future, would bea grave mistake."

He pointed out, for example, that16mm offers a wide choice ofequipment, while super 8 equip-ment is limited at the present time.Likewise, there is very little onsuper 8 in the way of existing filmlibrary materials-available free orotherwise. In contrast, there are lit-erally thousands of titles of 16mm.

"Furthermore," he said, "thispattern will continue for some timesince 16mm is the choice of seriousproducers of documentaries, educa-tional films, syndicated TV shows,and business and industry films."

Dr. Simmons summed up the16mm-super 8 choice this way:

"When super 8 finds its way into


TV, we believe it will be as ameans of recording news. We hopethat this occurs, since super 8 hasmany attractive attributes. When itdoes, the equipment probably willbe less expensive and more highlyautomated. For the present, wethink that the most practical choicewill be 16mm as the basis of yourfilm system, supplemented by35mm slides. Eventually, super 8should be added."

Film processing, according to Dr.Simmons, is the most inconvenientstep in the film system-yet themany advantages of film outweighthis one drawback. He cited thestreamlining of current procedures,widespread availability of process-ing services, and the number ofsimple, high -quality film processingmachines now available. He notedthat Kodak's ME -4 process cur-rently is installed in about 300 TVstations and 140 labs around thecountry.

"We find that most of these ma-chines, using the ME -4 process,particularly those in television sta-tions, are being made available toother film -users for fast processingservice," he said. "Many are doingwork for business and industry aswell as for other TV stations."

The remaining two elements inthe complete film -handling systemare editing equipment, availablefrom a number of service and spe-cialty dealers; and the film pro-jector, with associated multiplexerand pick-up vidicon camera, whichreceives all film originations.

Present And FutureDr. Simmons acknowledged that

the long-term prospects for CATVinclude such possibilities as the useof satellites, cable networks, andthe development of the cable as thepipeline into a home communica-tions center.

"But what of the present?" heasked. "The most meaningful areaof activity is your ability to origi-nate truly local programming alongwith local advertising. Just as thepublic is entitled to programs thatexplore local issues, so the smallbusiness is entitled to local adver-tising outlets. The broadcaster, al-ready feeling the pressure for morelocal origination, cannot competewith the capabilities of CATV inthis area. There seems little doubtthat the immediate future will seetransmission of distant TV signalsas the minor-not the major-ac-tivity of CATV."

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IC's In Audio ApplicationsDon't overlook the Fairchild 716

Integrated Circuit simply because itis sold as a "hobbyist" item by elec-tronics parts houses. These IC's, de-signed to feed a load of 150 ohmsor higher at power levels up to 1/4watt, offer very low distortion am-plification at audio frequencies.

The inexpensive blister -packaged716's appear substantially identicalto the regular 716's available fromFairchild distributors except somehave a higher noise level. The noisewas low enough in two dozen sam-ples I checked for program if notpreamplifier applications.

The schematic shows two stageswhich can be adjusted to voltagegains of 100 to 40,000 in steps of6 dB. One stage should be used ifa range of gain from 10 to 200 is

adequate. If gain of no greater than10,000 in two stages is used, distor-tion remains below 0.25 percent atlevels up to 50 milliwatts output.The voltage gain is determined bythe bypass capacitor connection to

singular or a combination of pins 1,8, 1 and 7, and 1 and 8.

Output source impedance is about1 ohm, but loading with much lessthan 150 ohms destroys the IC. A150 ohm resistor wired in serieswith the output makes the amplifierimmune to external shorting. Oscil-lation also destroys the IC, so watchlead dress if high gain is used. At-tach a heat sink to the IC's TO -5

case.I built two control boards re-

cently using these amplifiers. Theyresulted in lower cost and consider-able simplification over amplifiersusing discrete components exclu-sively.

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Plumber's Delight

For Engineers

At some long forgotten time inbroadcast history, there probablywere at least a few engineers whowere handling strictly electrical/electronic station duties. But a mod-ern day chief could hardly make ascratch on his weekly work load ifhe were not also functioning as aconstruction engineer, design engi-neer, plant maintenance engineer,and mechaical engineer. (You canadd your own categories to thelist!)

It is with this thought in mindthat we give you the following ac-count of Fred Clinger's debut in yetanother form of engineering. Callthe category what you may, but addit to the list for the stations in thecorn fields. The Editor.

A number of radio stations havea problem of supplying water fortransmitter personnel, when thetransmitter is in a rural area, withno running water, and the station iseither unwilling or unable to drilla well. WBCO was one of this num-ber.

The transmitter site is locatedmore than two miles from the near-est town, and about a quarter milefrom the nearest farm, in what wasin days past, a farmer's field. Forwashing hands, cleaning up thetransmitter room and workshop -studio, water was hauled every dayfrom the nearest farm in milk cans.

This soon became a large painfor the chief engineer and the dutyengineers. After the water washauled from the farm, a small elec-tric pump moved the water into anoverhead 30 gallon storage tank,which was connected to the washbasin.

This system was complicated bythe fact that the duty engineer couldnot leave his post to haul water. Hehad to wait for the chief to showup, or until his relief appeared be-fore going to get the day's supplyof water. This created an overtimesituation for supplying water, aproblem that continued until I de-cided the water problem would besolved. The answer was very sim-ple. All we needed was a rain bar-rel!

D

D

Puts a border around yourkeyed in lettering or any art-work to make them stand outagainst the lightest background.Just compare the top screenwith the one below it. The in-crease in readability heightensviewer enjoyment and drama-tizes. Sports News - Commer.cials can become more interestholding. Get them read!

BORDERLINE AVAILABLE FOR FREE TRIAL

Borderline has been on the marketfor little more than a year, but as faras the more successful broadcaster isconcerned it has become establishedas an essential piece of equipment.A survey of the many units sold indi-cates that the majority have been

purchased by the stations leading intheir market areas.

Broadcasters can now obtain withoutobligation a Borderline for a trial pe-riod of 30 days, by just filling out thecard and mailing it in.

*team ?wads ?at tole 7w c you2 7/eqwnori4fThe International Standards Converter CompanyA ANDERSEN LABORATORIES

1280 Blue Hills Avenue Bloomfield, Conn. 06002(Continued on page 54)

July, 1970


53

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Engineer's Exchange(Continued from page 53)

I spotted the evespout from thetransmitter building roof, which wasdraining the water into the field.The obvious solution was to catchthe rainwater in a container, andthen get it into the transmitter build-ing. The answer was to use a 55 -gal-lon oil drum to catch the water.

The spout was removed from thecenter of the eaves (the hole ce-mented shut) and inserted at theend of the building. Then a squarehole of about three inches was madein one end of the rainbarrel to ac-commodate the evespout.

A one -inch hose from an electricpump was brought out through thetransmitter wall, through a hastily

made hole in the concrete wallblock. The plug in the drum wasthen removed, and the hose in-serted through the hole.

After the first rain, we noticedthat about five percent of the waterentered the barrel, which was thenfull, and 95 percent went onto theground around the foundation ofthe transmitter building. Obviously,an overflow system was necessary.This was constructed by chiselinga small round hole in the barrelabout six inches from the top. Thena small piece of water pipe, aboutten feet long, was inserted in thehole. The pipe was then cementedinto place, using the black roofpatching compound.

Fred ClingerWBCO-Ohio

Setting Up RemotesFor Church Services

If you have found it difficult toget part time help to cover thosechurch pickups, or you wonder whyyou lug all that gear around, per-haps this little gadget is just theanswer you have been looking for.

We had a problem! Our churchbroadcasts originated from the samechurch for one month and thenmoved to another location for thenext month. It was possible to leavethe equipment set up, but we hadproblems finding part time help tomix the broadcast and set up thegear for each month's service. WhenI had been called out two Sundaysin a row I decided to solve the prob-lem with the device shown in Fig. 1.

A shielded transformer with four150 ohm windings is the main item.It was mounted on an aluminumright angle bracket inside a mini -boxjust large enough to hold it, thethree female mike connectors, andthe one male mike connector. Wir-ing is straight forward, just watchthe phasing and ground connections.If you use the RCA mike wiringsystem, just tie all the pin l's to-gether and do not ground them.

In the church three mikes (whichwill do almost any pickup) are setup and connected to the combiningnetwork, and a mike cable isplugged into the output of the net-work and run to a single mike inputremote amp. The remote amp canthen be placed in a convenient lo-

cation for AC, Telco loop, andwhere it will not be tampered with.

The trick to this setup is thechoice of microphones. They mustbe chosen and placed to do thebalancing. For example, the organchoir will be the loudest part ofthe pickup. If the choir is locatedin two lofts facing each other, abi-directional mike would be a goodchoice. Pick up the organ by na-tural balance as usually the organistwill try to balance to the choir, soa good clean choir pickup will do it.

For the pulpit or lecturns, a mikewith more output and a cardioidpattern would be a better choice.Try something like an EV RE15which has an output of -56dBm.For certain special pickups with softspeaking you could chose a mikewith higher output such as an EV667A. Its output is -51dBm. AnAltec 639 can also be useful be-cause you have six patterns. Thiscan be used to control the congre-gation level. Just one final point:when selecting mike outputs alwaysreference them to the same rating,e.g.; 1 mv/10 dynes/CM'.

William GrahamKitchener, Ontario

Fig. 1


IRA PRODUCTS(Use circle number on reader service card for further information)

Ampex Unveils DuplicatorA prototype ADR-150 was dem-

onstrated for the first time at theNational Association of Broadcast-ers' convention in April.

The ADR-150 is designed formodular expandability to accom-modate up to five slave reel systems,permitting duplication of from oneto five copies in a single operation.The price starts at $79,950, depend-ing on the number of slave modulesemployed. Deliveries will beginearly in 1971.

The ADR-150 is designed fortelevision stations, networks, tele-production centers and advertisingagencies that frequently require sev-eral copies of video taped commer-cials, promos, syndicated or net-work programs, news and sportsclips and feature segments for rapiddistribution.

Duplicates made on the ADR-150 can be played on any standardquadraplex broadcast videotape re-corder, and are interchangeable

with all conventional transverse -oriented, two -inch -wide video tapes.All broadcast formats, includinghigh -band and low -band, color andmonochrome and 525 and 625 linestandards, can be faithfully dupli-cated on the ADR-150.

The new duplicator uses a dy-namic transfer system by which aspecially formulated master tape isbrought into direct contact with con-ventional blank transverse -scanvideo tape. The blank, or slave tapeassumes the arrangement of mag-netic particles present on the mastertape with insignificant degradationof video signals on the master tapeafter repeated uses.

The duplication process occurs ina magnetic transfer chamber locatedin the center of the tape paths onthe ADR-150. Both the master andslave tapes, which are loaded onseparate reels, are threaded throughthe same transport area and broughtinto direct contact in the magnetic

Ampex ADR-150 Duplicator

transfer chamber.Vacuum chambers located on the

ADR-150 transport permit easytape threading and gentle tape han-dling, and provide for positive tapecontrol through the magnetic trans-fer chamber.

Ampex Model ADR-150 will en-able producers and distributors oftelevision commercials and pro-grams to make quality tape copiesof a master recording in one -tenththe time currently required in videotape dubbing, according to Law-rence Weiland, vice president -general manager, video products di-vision.


Portable MixerUnder type designation MP4,

Philips has introduced a portablefour -channel mixer specially in-tended for radio and television stu-dios and outside broadcast units.

Though compact and lightweight-a mere 38 pounds (including bat-teries for mains - independent op-peration when necessary)-the MP4meets the highest studio standards;its performance being comparableto that of advanced custom-builtmodular mixing consoles, accordingto the manufacturer.

Clean -sound circuitry has been in-corporated, there are two separatemixing busbars, and every channel(input and output) has insertionpoints for external equipment(equalisers, limiters, compressoramplifiers, etc.).

Primarily intended for broadcast-ing purposes the MP4 neverthelessfits the bill for many audio installa-tions. Its installation can be bybuilding it into a 19 -inch rack incompany with other audio equip-ment such as tape recorders, poweramplifiers, etc.; when mounted in asuitable frame, two or more MP4mixers in combination, with the fa-cilities by equalizers, compressoramplifiers and intercom equipment,results in an attractive low-pricedstudio mixing console capable ofhandling a wide variety of pro-grams, in both mono and stereo.

A three -position key -switch is as-sociated with each of the four chan-nels. The center position of theswitch is for channel muting and the

July, 1970 55

New Products(Continued from page 55)

other two positions are for inputselection. Each channel's input sen-sitivity can be set to any of fourdifferent levels by means of a ro-tary switch. Four selection switchesmounted inside the mixer adjusttheir associated channel pre -ampli-fier for use with either 200 ohm or50 ohm microphones. In the stand-ard version of the MP4 carbon -trackrotary channel faders are used.Other types of faders can be sup-plied on request and provision hasbeen made for sliding faders to bemounted externally. Each channelhas its own push-button switch forconnecting the input signals to theselected mixing busbar.


Digital MultimeterTriplett Corporation is introduc-

ing a new 3-1/2 digit table -top, Digi-tal Multimeter Model 8000-A withsolid-state circuitry that retains stor-age of any displayed readout indef-initely; has good AC accuracy andlinearity and 10 Megohm input re-sistance; and virtually no kickbackcurrent, allowing voltage measure-

ments in high reistance circuits atstated accuracy.

Triplett's Model 8000-A has pro-tective circuitry preventing damageto the unit when voltages as high as100 volts AC or DC are applied asinputs on and of the selectable volt-age ranges. Also, it has as much asa 50 percent over -range and asample rate of six times per second.

Measurements are displayed withexcellent resolution in the decimalnumber system by three gas -filledreadout tubes. The numeral "1" isdisplayed for over -range meausre-ments. The readout display is com-plete with a movable decimal point,and automatic over -range indica-tion (0/R).


Video Control CenterFor multi -camera television pro-

ductions in educational, military,medical and CATV systems, Tele-Mation, Inc., has designed a com-pact unit which handles all syn-chronizing, switching and control

functions of the several videosources.

The MULTICASTER® VideoControl Center (Model TMV-650)ties as many as four cameras to onecentral system for smooth, syn-

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chronous switching. Included are avideo processor, video level meter,two solid-state vertical -interval pro-gram switching buses, separate pre-view bus and splitarm fader control.Looping jacks in the MULTI -CASTER® can route the video fromeach camera to other system equip-mmt, eliminating the need for sepa-rate video distribution amplifiers, oreach input may be terminated in75 ohms by switch.

Multi -conductor camera inputscan be used for non -synchronoussources, such as a video tape re-corder or tuner. Gain and pedestalcontrols are provided for profes-sional one-man control of allsources.


New Clark 100AStereo Headset

David Clark Co., Inc. announcesthe redesign of Clark/100 seriesstereo headsets. Internally the trans-ducer has been redesigned to givesmoother frequency response, morerugged voice coil structure, bettertransient response and more lowfrequency output.



The improved models will carryan "A" designation; Clark/100A(17 ohms), the Clark/103A (300ohms), the Clark/106A (600ohms).

The transducer is the result ofnearly four years of research anddevelopment. Physically, the trans-

ducer is a dynamic, moving coilwith a mylar cone and ceramicmagnet. Power input, 1 watt con-tinuous. The frequency range is 20to 22 KHz, frequency respones 20to 16 KHz. Distortion is less than1 percent over the audio band.


Automatic Peak ControllerCBS Laboratories unveiled a new

automatic peak controller. Desig-nated the Volumax model 4000,this unit offers the broadcaster theopportunity to turn the asymmetryof speech waves to his advantageby ensuring that the highest ampli-tude peaks always positively modu-late the transmitter.

If the predominant asymmetrypolarity is positive, the signal is

passed through a non -inverting va-riolosser circuit. Conversely, if thepredominant asymmetry polarity is

negative, the sign al is passedthrough an inverting channel. Theswitching action between polaritiesis silent. A front panel switch al-lows the positive modulation levelto be limited at either 100 or 120percent.

The Volumax analyzes all pro-gram material and automaticallyselects the appropriate regulationspeed. Limiting action may begentle or microsecond fast, depend-ing upon the nature of the programwaveform.


Vertical IntervalProduction Switcher

DYNAIR Electronics, Inc., hasadded a new low-cost vertical -inter-val three -buss mix/effects produc-tion switcher to its line of profes-sional video programming equip-ment. The new VS -152A is com-pletely solid-state and has all thecapabilities necessary for profes-sional programming, including in-stantaneous switching, fade-in, fade-out, lap -dissolve, superimpositionand special effects.

The switcher accepts six non -composite and two composite videoinputs. The non -composite inputsare connected to three busses, twoof which feed an effects amplifierwith a split -lever control. The out-put of the effects amplifier and the

third buss is applied to the mixer,which also has a split -lever control.The composite inputs are switchedby a separate three -button buss,which provides a selection betweenthe mixer output and either of thetwo composite inputs. All video sig-nals are switched by Solid-statecrosspoints during the vertical in-terval to assure a glitch -free transferof signals.

The special effects amplifier pro-duces a single electronically com-bined signal from any two of thesix non -composite input sources,with capabilities for inserts fromeach of the four corners, and fullhorizontal and vertical wipes. Theinserts can be expanded horizont-ally, vertically and diagonally.

Circle Number SI on Reader Reply Card

VS -152A PRODUCTION SWITCHER

AIM Alm.

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Meantfor the BroadcastIndustry...

REMOTE CONTROLMIKE REELS

Specially designed reels. Remotecontrol by drum, push button orstation relay. 115 volt reversiblechain driven motor. 2 to 8conductor slip rings available.150' cable capacity.

POWER CABLEREELS

I.E.R.'slevel windPort -O -Reelsprotect andprevent mikeor extensioncord break-downs. Up to400' cablecapacity.

Write for Specification Data on themost complete line of RemoteControl Reels and Port -O -Reels.

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July, 1970


57

New Products(Continued from page 57)

Lead -Oxide Target VidiconCamera Tubes

A new family of RCA lead -oxide target vidicon television cam-era tubes, called Vistacons, that aredirectly interchangeable with com-petitive lead -oxide target types, wasannounced by RCA ElectronicComponents at the 1970 NationalAssociation of Broadcasters Con-vention.

"Two series of Vistacon cameratubes are included in this initialannouncement to the broadcast in-dustry," according to C. H. Lane,division vice president and generalmanager, RCA Industrial Tube Di-vision. "One series has internalmesh connections and the otherseries has separate mesh connec-tions."

Both series of Vistacon tubes fea-ture lead -oxide targets that arecharacterized by high sensitivity,very low dark current, very lowlag, and a "gamma" of nearly unity.


DC Voltages StandardCohu Electronics, Inc. has an-

nounced production of a new DCvoltage standard designed for con-trol by computer. The Model 381Programmable DC Voltage Stan-dard's accuracy/stability factor willhold the instrument within 0.003percent of set value for 12 months.It supplies output voltages to 120volts at either polarity. Current upto 100 milliamperes is limited to aselected level according to the con-trol equipment program.

Commands can be applied to theinstrument either automaticallyfrom a computer or by an operatorusing a decimal -to -BCD converter(available as an option). The Model381 responds to parallel -entry, 4421or 8421 binary -coded -decimal, 27bit commands. Twenty bits set themagnitude of the output voltage,two bits determine the polarity,three bits select the proper voltagerange and two bits set the limit ofthe output current.

Technical specifications forCohu's programmable standard are

CUSTOM

CONSOLE

Designed and

Built far

KVVVVL

WATER100,10ViA

Discussing the new FairchildCustom Console, designed and builtfor KWWL, Waterloo, Iowa, areEdward M. Tink, Vice President,Engineering of the Blackhawk sta-tions and George AlexandrovichVice President and Chief Engineer

of Fairchild Sound Equipment Corp.The new Fairchild console will

be utilized primarily as an oper-ating console for KWWL-AM andin addition will provide certain con-trol and monitoring capabilities forKWWL-FM's automated facilities.


engineered to meet the needs of awide range of user and OEM ap-plications including use as a DC sti-muli generator in instrumentationcomputers; calibration of amplifiersin process control computers; andas a precision DC source in auto-matic or semi -automatic checkoutsystems.

Noise and hum on the 1V and10V ranges is less than 20 micro-volts rms and less than 30 micro-volts on the 100V range. Fast set-tling time brings the output withinrated accuracy ±0.01 percent ofstep change in less than 100 milli-seconds from time of address.

Common -mode rejection is betterthan 120dB from DC to 400 Hz, upto 350V rms or 500V DC. Outputvoltage changes less than than 10-6of the applied common -mode volt-age. Output isolation permits eitherterminal to be floated up to ±500Vpeak from chassis to ground.


Duplication TapeMemorex Corporation has an-

nounced a breakthrough in colorTV recordings for broadcast, edu-cational and ultimate home use-anew low-cost high-speed process forthe mass duplication of video tapes.

The Memorex duplication pro-cess is made possible by a newchromium dioxide magnetic tapewhich Memorex will produce andmarket beginning this summer.

Memorex President Lawrence L.Spitters revealed that the duplicat-ing equipment now operating in thecompany's laboratories simulta-neously turns out multiple dupli-cates at high speed for an effectiveproduction rate 10 to 15 timesfaster than present processes. Exist-ing video type duplicating processesmust utilize a separate expensivevideo tape recorder which takes onehour to duplicate a one -hour pro-gram, whereas the new Memorexprocess takes only minutes. TheMemorex process requires no elec-tronic circuitry to transfer betweenthe master and an unlimited num-ber of copies.

"The physical properties ofchromium dioxide also producecopies which have twice the mag-netic energy or 'brilliance' of con-ventional original video tapes,"Spitters said.

The greater video informationstorage capacity of chromium di-


oxide will open the way to thedevelopment of a new generationof video equipment operating atspeeds down to one-half those ofpresent recorders. This means twicethe programming per reel or asignificant cost reduction per pro-gram for the user. This sharplyreduced media cost coupled withthe economies of the Memorexduplication process should set mag-netic tape as the standard massvisual medium.


Wide RangeCardioid Microphone

The latest advancement in dy-namic microphones, the RE20, iscurrently being marketed byElectro-Voice, Inc. This micro-phone is a rugged, wide -range, qual-ity cardioid dynamic microphone. Ithas been designed and manufac-tured for use in the professionalrecording applications as well asbroadcasting.

The RE20 has a wide uniformresponse curve comparable in char-acteristics to high quality condens-ers. Another important character-istic of the RE20 is its transientresponse. These electrical advant-ages are complemented by theusual ability of the dynamic mic-rophone to "take it."


CATV Data ModulatorA new data modulator to provide

an interface between the video out-put of alphanumeric generationequipment and the RF transmissioncapabilities of community antennatelevision systems has been devel-oped by the Catel Corporation.

Designated the DTM-2500"Data -Mod," the device incorpo-rates special video filtering to allowthe presentation of alphanumeric in-formation without ringing and/orovershoot and further allows the useof character generator chrominanceinformation. Since the Data -Mod isdesigned primarily for use with

CATV systems, a normal aural car-rier is provided, which can be mod-ulated with a local FM/AM tuner,tape deck, or other audio source.

All solid state silicon device con-struction, the Data -Mod is availablefor standard television channels,with midband and special frequen-cies optional at extra cost.


Microwave RepeatersA new series of all solid state

Microwave Heterdodyne Repeaters(no klystron) will be shown pub-licly for the first time at theAFCEA Show by RHG ElectronicsLaboratory, Inc. These repeaterssupplement the company's line ofmicrowave FM -TV relay links andexpand their complete line of micro-wave receivers, transmitters andcomponents.

The heterodyne repeaters, Series"FIR", are completely tubeless andutilize a unique double balancedparametric upconverter which per-mits transparent operation over therange of 2 to 8 GHz with outputpowers to 2.0 watts.

Meeting applicable FCC require-ments, the repeaters incorporatepreselection, delay equalization, andcrystal stabilized70 MHz IF provides for tie in toexisting systems.


Base Station YagiThe Phelps Dodge Communica-

tions Company has developed a new4.75 pound base station yagi an-tenna in the 450-470 MHz rangeand offering 10 dB unidirectionalgain. Nominal input impedance is50 ohms and maximum power in-put is 250 watts with a VSWR of1.5:1. Bandwidth is 20 MHz.


UHF TranslatorRodelco, Deer Park, New York

has a new all solid state UHF trans-lator ready for the market. Offeringlow power drain and virtually nowarm-up time, this translator is cap-able of 10 watts visual output atpeak sync and 2 watts aural.

Other features include completecircuit metering, automatic gaincontrol, .001 conversion accuracy,and an input level minimum tomaximum range of 100 to 5,000microvolts. Input impedance is 50and 75 ohms unbalanced, 300 ohmsbalanced. Output impedance isselectable at 50 or 75 ohms.


S DIDDIRECTC R TODEALERS

STUDIO -PROCUSTOM MODEL TURNTABLE

Single lever controls 33 8 45Speeds. Plays 45's withoutadapter. Illuminated speedindicators. Has detachabletone arm mounting plate.

Comes with syn. motor only.

INTRODUCTORYPRICE $198

"CoCUE- MASTERSTANDARD MODEL TURNTABLE;Ingle lever controls 33, 45 8 78

speeds. Rays 45's without adapter.

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'RICE WITH 4 POLEND. MOTOR $145

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PH. 299-4692

July, 1970


59

EMI DATAFor further information, circle dataidentification number on reader service card

100. AMERICAN ELECT.LABS. - An 8 -page AM/FMBroadcast Transmitter "short -form"catalog, which highlights the prod-ucts of its BROADCAST TRANS-MITTER DIV. is now available.The AM series includes a varietyof quality transmitters with powerfrom 250 watts to 110 Kw. Usingthe latest "start of the art" tech-niques, AEL assures the productionof transmitters of highest quality.The sister line of FM transmittersbegins with a 10 watt unit and in-cludes other standard powers up toa 20 kW model (FM-20KB). Inaddition to AEL's transmitter line,the catalog focuses on the AELAM/FM Automatic TransmitterSwitch Model # ATS Series (to 100kW), the Model 2203 all solid stateStereo Generator and the improvedModel 2202A all solid state directFM Exciter.

101. AKG-NO. AMERICANPHILIPS CORP.-A 20 -page cata-log describing AKG's CMS F.E.T.condenser microphone system isnow available. The brochure de-scribes in detail phantom poweringtechniques for F.E.T. condenser mic-rophones. The C -451E system per-mits interchanging of condenser mic-rophone capsules of various pick-up characteristics such as cardioid,omni-directional, figure -eight andinterference tube (shot gun) attach-ment.

102. AMPEX CORPORATION.-A two-color, 16 -page brochuredescribing the full line of Ampextelevision transmission products isnow available. It describes the com-pany's VHF and UHF transmitters,translators, antennas and coaxialproducts and antenna accessoriesfor use by commercial and educa-tional television stations. In addi-tion to technical descriptions andspecifications of the products, thebrochure gives space requirementsand describes the Ampex antennatest range in Westfield, Massachu-setts.

103. BIRD ELECT. CORP. Thenew 4 -page Short Form Catalog

SF -70 lists nearly all the coaxialload resistors, absorption wattmet-ers, and directional wattmetersstocked by Bird Elect. Corp. Thefeature product is a portable peak(and average) reading directional RFwattmeter, now equipped with a bat-tery charger/eliminator for extend-ed bench use at no additionalcharge. In addition to basic per-formance specifications and prices,SF -70 also describes related custom-built accessories such as coaxial fil-ters and the new Self -cooled 10kWRF Terminating Systems introducedat the IEEE Show. A useful chartof RF letter band designations withtheir associated frequencies is in-cluded with a directory of regionaloffices and overseas representatives.

104. BOSTON INSULATEDWIRE & CABLE CO. -A newbrochure covering the company'sunique capabilities in the design andmanufacture of specialized wire andcable products and systems is nowavailable. Developments describedinclude both insulation materials andprocesses. Special attention is givento BIW's wide range of productionfacilities, including: extrusion sys-tems, taping machines, rubber com-pounding, finishing and asesmbly.The braiding, shielding and armor-ing facility is one of the most versa-tile in the industry. Modern labora-tory, engineering, testing, and qual-ity control facilities are also de-scribed. The sophistication of thecompany's capability is indicated byexamples of innovations developedto meet customer's needs.105. COHU ELECT, INC.-A 6 -page condensed catalog on broad-cast television products is now avail-able. This catalog (6-545) has pho-tographs and brief specifications onnearly two dozen items-from pro-duction video switchers to colorvideo encoders.

106. ITT JENNINGS-A new20 -page catalog describing its en-tire line of vacuum contactors isnow available. The contactors areused to control DC, RF, and ACcircuits at voltage levels from 0 to

over 70 kilovolts. They also provideprimary control of power suppliesin high -power transmiters, heatingequipment, and industrial controls.The contactors can be coordinatedwith current -limiting uses in circuitsthat have high fault currents. In ad-dition, they can control furnaceloads, lighting loads, and high-pow-ered RF antenna switching. The cat-alog lists ITT Jennings' new 250 -to -900 -amp three-phase contactors.Standard operating voltages are1500 volts; interruption ratings are3,000 amps and 9,000 amps. In-cluded in the catalog are severalpages of application notes whichdescribe the characteristics and test-ing of vacuum contactors and howbest to apply them in circuits.

107. JFD ELECTRONICSCORP./SYSTEMS DIV.-A new8 -page catalog of hardware forequipping school districts and in-dividual schools with complete In-structional Television Fixed Service(ITFS). 2500 MHz micro -wave sys-tems is now available. The new cat-alog covers 10 watt transmitters,mini -power transmitters, micro-power transmitters, repeaters, re-ceiving systems, down converters,distribution systems, transmittingand receiving antennas, accessoriesand calibration equipment. Usingthis ITFS equipment, a school dis-trict may originate one to four in-structional TV channels and trans-mit them to all schools within thedistrict.

108. POMONA ELECTRONICS-The 1970 general catalog of elec-tronic test accessories is now avail-able. The new edition is expandedto 56 -pages and now contains 420items -50 of which are new thisyear. Featured new products in-clude: a new series of 3" highshielded "Black Boxes" with cardguides; a new series of shielded"Black Boxes" (now offered in fourdifferent sizes); two versions ofshielded "Block Boxes" with iso-lated BNC connectors; new Twinaxpatch cords and receptacle jack;two series/parallel isolation plugs;two pin connector test adapters; newminiature (1/2 " spaced) pin tip plugsand jack; plus several miscellaneousbanana plugs, adapters and acces-sories. Catalog provides completeengineering information on all items,including product photographs, di-mension drawings, schematics, spe-


cifications, features, and operatingranges.

109. PRINCETON APPLIEDRESEARCH CORP.-A new 20 -page catalog includes new additionsto the company's line of instrumen-tation for research. Signal process-ing instrumentation described in-cludes lock -in amplifiers, signal cor-relators, signal averagers and low -noise pre -amplifiers. Other equip-ment included are electrochemicalanalysis systems, Evoked ResponseSystems for neurological study, andan Instrument/Computer InterfaceSystem which can interface analogor digital instruments to a remotetime-shared computer via an ordi-nary telephone.

110. RCA-A new 12 -page bro-chure and series of catalog sheetsdetailing the complete complementof color television equipment is nowavailable. The brochure provides anoverview of innovative color cam-eras priced under $10,000. Colorfilm systems and video tape record-ers are also described. Several typ-ical TV systems for instructionaland training applications are de-picted.

111. TELEMATION-A heav-ily -illustrated 24 -page booklet out-lining progression from a singlecamera/VTR television facility to amulti -camera, full -color productionsystem is now available. The pur-pose of the System Expansion bro-chure is to help CATV and ITVoperators select equipment for avery small TV operation whichwon't become obsolete or incompat-ible as they expand to a larger sys-tem. Nine systems are detailed inthe brochure, each "complete" initself but capable of being incorpo-rated into gradually more elaboratesystems. In each major expansion,such as from a single -camera tomulti -camera operation requiringswitching, options in equipment areincluded to meet various budgets.

112. TENNEY ENGINEERING,INC.-An improved 3 -cubic -footBench Model Temperature -Humid-ity Test Chamber is described inBulletin No. 101C. This latest com-pact version of the popular TH Jun-ior has extremely wide operatingrange capability, occupying minimalspace. With temperature range from10°F to 200°F, and humidity rangefrom 20 percent to 95 percent, theavailable work space is an ample

161/2" x 20" x 153/4". Relativelymaintenance -free because of its sim-plicity, the TH Jr. employs separatesolid-state SCR instrumentation tocontrol its wet bulb and dry bulbtemperatures. These instruments fea-ture automatic reset and propor-tional controls, and a pyrometerwith an accuracy range of 1 percentis provided for indication.

113. TRIPLETT CORPORA-TION-A comprehensive new 20 -page catalog D-70 featuring stan-dard and special panel meters thatare designed for such applicationsas electronic instrumentation, com-munications equipment, industrialprocess control, military groundsupport equipment, laboratory andeducational uses plus many more, isnow available. The two-color Trip-lett catalog D-70, three holepunched for ring binder referenceusage, is complete with detailedelectrical and mechanical specifica-tions and dimensional and mount-ing drawings. User net prices arealso given for all panel meters listed.Many new instrument additions areprovided in the new catalog. Someof these are: a new line of Pyro-meters with thermocouples; specialmeters that are available with mir-rored scales, special scale readings,pointers, illuminated kits, custominserts, special accuracies; four newshallow barrel "G" type meters forspace saving instrumentation re-quirements; new DC millivoltmeterswith suspension type movement inthe 31/2" and 41/2" "G" Series panelmeters with optional half -bezel formounting behind panel and conven-tional flush type mounting; Trip-lett's new Model 300 meter ampli-fier with linear scale on all AC mea-surements; null meters; and portableinstruments for schools, labratoriesor shops.

114. TROMPETER ELEC-TRONICS-A new 1970 Catalogillustrating a complete line ofCOAX, TWINAX, TRIAX andQUADRAX Connectors, PatchPanels, Plugs, Jacks, Patch Cordsand Accessories is now available.The 44 -page catalog details highand low frequency COAX switchesand matrices employed in TVBroadcast, CATV, CCTV, ETVCommunications, Telemetry, Tele-phone, Nuclear Instrumentation andInformation Retrieval.


when you specify

SWITCHCRAFT"TELEVER"

TELEPHONE TYPE

SWITCHES

...smile

SERIES 16000

...you've doneyour product

a favor1. OUTSTANDING QUALITY

Virtually indestructible "T -Beam"frame. Proved and preferred Leaf -type switch stacks go on -and -onafter other types wear out. Mate-rials and finishes meet Mil specs. . . overall design meets rigidtelephone company standards (butwits- lots more uses).

2. CHANGEABLE FUNCTIONSInsert for

non -lockingoperation .

Remove insertwith 2 screws

ear- and it's alocking switch!

Now it locks-now it doesn't. Ex-clusive removable inserts convertsit either way-even in the field.Can be locked in any one or allpositions.

3. TOPS IN VERSATILITYIncomparable flexibility in contactarrangements (up to 8 -pole, doublethrow). Two and three position.Palladium or fine silver contacts.Unsurpassed for any criticalswitching function-telephonecompanies, communications andtest equipment, computers, groundsupport equipment, etc.

Write for bulletin S-312, or see your au-thorized Switchcraft distributor for imme-diate delivery at factory prices.

5535 Elston Avenue, Chicago 30, Illinois

Canada: Atlas Radio Corp., Ltd.,50 Wingoid Ave. Toronto, Ontario, Canada


July, 1970 61

new miniature

electronic pliersHOLD, BEND, CUT

ALL FINE WIRES

WITH EASE

CHAIN NOSE ANDDIAGONAL CLOSECUTTING PLIERS

SPECIAL TIPCUTTING PLIERS

RADIO AND TV PLIERS

Ideal for electronic, radio/TV, elec-trical service and assembly. Forgedalloy steel construction. Precisionmachined. All have polished headsand shoulders. Comfortable "CushionGrip" handles and coil spring openersspeed work, reduce hand fatigue.Miniature round and flat nose pliersalso available.

a complete line of regular

pliers and snips, too

Includes long nose pliers with andwithout cutters; diagonal, needlenose, chain nose, side cutting, andother pliers; electronic snips. Varietyof sizes. All available with "CushionGrip" handles. Professional quality.

XCELITE, INC.,.118 Bank St., Orchard Pa k, N.Y. 14127In Canada contact Charles W. Pointon, Ltd.



115. UNITRODE-A new ZenerSurge Selection Guide which listsall Unitrode zener types from 1 to10 watts with their specific voltageand surge rating for each idividualtype is now available. Included isa graph showing typical reversesurge power for pulse durationsfrom 100 sec to 10 msec for eachfamily. The handy reference guideis especially useful when designingfor surge applications.

116. UNIVERSITY SOUND,-A division of LTV Ling Altec. Anew 1970 comprehensive PA cata-log with the technical data on thelatest commercial products is nowavailable. Information on all Uni-versity Sound products from Power -Line amplifiers to portable Power -page systems is included in the newcatalog.

117. UPSON TOOLS, INC.-Anew catalog No. 171 consisting ofthe addition of 44 new items includ-ing assortments, kits and individu-ally carded tools is now available.The catalog also contains a list ofsales representatives as well as im-portant conversion tables applicableto the hand tool industry.

118. VIKOA, INC.-A new il-lustrated 63 -page catalog featuringwire, cable and electronic productsfor Internal Distribution Systemuses and needs is now available.Complete and extensive delineationhas been made regarding all typesand construction of wire and cablesused by the communications trades.Pictorially depicting wire and cableas well as electronic products, thisIDS/MATV equipment catalog hasa handy thumb-thru index as wellas a complete alpha -numerical in-dex.

119. VISUAL ELECTRONICS--This new brochure describes theVisual Educom 620P Portable TapeRecorder which is a professionalquality, high-fidelity recorder/am-plifier/speaker system. It providesthe untimate in reliability and crispaudio reproduction at a cost withinthe reach of most institutions. The620P consists of a magazine -typetape deck, dual channel amplifierand speaker system packaged in acompact, rugged carrying case. Stor-age space is provided for headset,tape magazines and other accessor-ies.

AME131Pla INDEXAmerican Data Corp. 27

Andersen Laboratories 53

Andrew Corporation 5

Broadcast Electronics 10, 51, 54

CBS Laboratories 17, 33

CCA Electronic Corp. 8-9

Cohu Electronics, Inc. 1

Electro-Voice, Inc. Cover 2

Fairchild Sound Equipment Corp. 54

Gates Radio Company Div., of Harris-Intertype Corp. 11

The Grass Valley Group Inc. 3

Industrial Electric Reels Inc. 57

Jamieson Film Company 16

Jampro Antenna Co. 52

Metrotech, Inc. 30

Mincom Div. 3M Company 21

Minneapolis Magnetics, Inc. 63

Quick -Set, Inc. 12

RCA Electronic ComponentsTube Distributor 35

RF Systems, Inc. 49

Rupert Neve & Co. LTD. 47

Russco Electronics Mfg. Co. 59

Schafer Electronics Cover 4

Spotmaster 10, 51, 54

Stanton Magnetics, Inc. 7

Switchcraft Inc. 61

Taber Manufacturing & Engineering Co. 56

Tape-Athon Corp. 23

Teac Corporation of America Cover 3

Tele Pro Industries 51

Thomson CSF 13

Varian Associates 31

Xcelite, Inc. 62

Buying? Selling?

Get ResultsWith Classified Ads

InBroadcast Engineering


Reference ListOf FCC Forms

For your reference we are including the followinglist of FCC forms. These often used forms may beobtained from your field office or by writing directlyto: Federal Communications Commission, 1919 MStreet, NW., Washington, D.C. 20554.FCC

Form Page202 Standard Broadcast RMS and Radi- 98:101

ation Pattern Data301 Application for authority to con-

struct a new broadcast station ormake changes in an existing broad-cast station 98:103

301-A Request for modification broadcaststation authorization (RemoteControl) 98:127

302 Application for new broadcaststation license 98:131

303 Application for renewal of broadcaststation license 98:138a

309 Application for authority to con-struct or make changes in an inter-national, experimental television,experimental facsimile, or a develop-mental broadcast station 98:147

310 Application for an international, ex -experimental facsimile, or a develop-mental broadcast station license 98:155

311 Application for renewal of an in-ternational, experimental facsimile,or a developmental broadcast stationlicense 98:157

313 Application for authorization in theradio broadcast services 98:159

314 Application for consent to assign-ment of radio broadcast station con-struction permit or license 98:161

315 Application for consent to transferof control of corporation holding

Tired ofHand -Me -Down

Copies ofBroadcast Engineering?

As a member of the communications

industry you probably qualify to re-

ceive a personal copy free! Just fill in

the Reader Service Card in the back

section of this issue. We'll do the rest.

radio broadcast station constructionpermit or license 98:179

316 Application for consent to assign-ment of radio broadcast station con-struction permit or license ortransfer of control of corporationholding radio broadcast station con-struction permit or license (ShortForm) 98:197

318 Request for subsidiary communica-tions authorization 98:199

321 Application for construction permitto replace expired permit 98:201

323 Ownership report 98:203324 Annual financial report of networks

and licensees of broadcast stations 98:209340 Application for authority to con-

struct or make changes in a noncom-mercial educational TV, FM, orstandard broadcast station

343 Application for authority to con-struct or make changes in a tele-vision broadcast booster station 98:213

344 Application for television broadcastbooster station license 98:219

346 Application for authority to con-struct or make changes in a tele-vision broadcast translator station 98:221

347 Application for television broadcasttranslator station license 98:229

348 Application for renewal of televi-sion broadcast translator stationlicense

98:212e

98:231

ERASERECORD

EPROVIte,2EMONO - STEREOProfessional Direct Replacement Heads withcomplete written and pictorial instructions

Our factory will clean, rebuild, adjust and test yourhead ASSEMBLY... install new M M I heads...replace minor hardware and modify your gateto accept our "NON- POPPING" springs

36 HOUR SERVICE - LOANERS AVAILABLE

(612) 884-7393

MINNEAPOLIS MAGNETICS, INC.8125 PLEASANT AVE. SO., MINNEAPOLIS, MINN. 55420

July, 1970


63

PROFESSIONAL EN CHFOR SALE

RADIO STATION -5,000 watts. Absenteeowned. $175,000 Terms. KHIL, Willcox,Arizona. 4-70-5t

Technical Services

VIR JAMESCONSULTING RADIO ENGINEERSApplications and Field Engineering

345 Colorado Blvd.Phone. Area Code 3031 333-5562

DENVER, COLORADO 80206Member AFCCE

TWX 910-931-0514

CAMBRIDGE CRYSTALSPRECISION FREQUENCY

MEASURING SERVICESPECIALISTS FOR AM -FM -TV

445 Concord Ave. Phone 876-2810Cambridge. Mass. 02138

ALLSTATE COMMUNICATIONSENGINEERS - CONTRACTORS

CATV -CCTV-VTR1200 WEST CHESTNUT STREET

UNION. NEW JERSEY 07083(212) 349-5240

PYRON TOWER SERVICESpecializing In

Tower Inspection-MaintenanceSuite B

108 East Granville RoadWorthington, Ohio 43085

614-885-8066

Advertising rates in Classified Section are152 per word, each insertion, and must be ac-companied by cash to insure publication.

Each initial or abbreviation counts a fullword. Upper case words, 300 each.

Minimum classified charge, $2.00.

For ads on which replies are sent to us forforwarding, there is an additional charge of$2.00 to cover department number, etc., whichis printed in advertising copy, and processingof replies.

Classified columns are not open to adver-tising of any products regularly produced bymanufacturers unless used and no longerowned by the manufacturer or a distributor.

Equipment for SaleTower Lite Control Panel Box contain-ing alarm. telo & auxiliary circuits, autotransformer and flasher units -115V 60cycle, unused. $125.00 each. Sierra -West-ern Electric Co.. Oakland. Cal. 94623.Phone 415-832-3527. 6-69-tf

CARTRIDGE TAPE EQUIPMENT-Com-pletely reconditioned Spotmaster andTapecaster Record/Playbacks. $375.00.Playbacks $250.00. 30 -day money - backguarantee on all equipment. BROADCASTPRODUCTS CO.. INC. 12330 Wilkins Ave-nue, Rockville. Maryland 20852. Ph: 301-933-3400. 10-69-tf

Highest prices paid for good used 1KWand 10KW AM Transmitters, FM Trans-mitters also. Geleco Electronics Ltd., 2Thorncliffe Park Drive, Unit 28, Toronto17, Ontario, Canada. Phone: 416/421-5631.

3-70-tf

RCA AVQ-10 Weather Radar system com-plete with Raydome, Heater, 400 cyclepower supply VJ-B monitors, cabling andspare parts-excellent condition. Broad-cast Engineering, Dept. 240, 1014 Wyan-dotte Street, Kansas City. Missouri 64105.

6-70-2t

SURPLUS 2 INCH VIDEO TAPE. Over200 full hour reels available in goodusable condition. Mostly 3M type 379,master tapes, few splices, low dropoutcount. Priced "as is" F.O.B.. N.J.. 1-5hours $50/hour, 6-10 hours $35/hour, 11or more hours $25/hour. COMQUIP, P.O.Box 12, Ridgewood, N.J. 07451 (201) 444-0196. 6-70-2t

Gates 10 watt FM transmitter modelBFE-10C, 91.1 MHz, Includes complete setextra tubes, Gates FM -22 (2 -bay) antenna.Total package, perfect condition. I-yr.old, sacrificed, $1000 FOB. WGGL-FMMichigan Technological University,Houghton, Michigan 49931, Area Code906/487-2617. 7-70-2t

RCA TK-30 and TK-31 image orthiconcameras: RCA TR-2 and TR-5 videotaperecorders plus many incidentals. Tele-vision Facilities. Inc., Box 396, Mont-gomeryville, Pa. 18936. Tel. 215-855-0970.

7-70-tf

3 -RCA COLOR CAMERAS TK-41C. Up-dated to NBC Specs., includes "paintpots". 50, camera cables, lenses, dollies,lenses, dollies, tilt heads, and Orthicons.All 3 for $43,500. COMQUIP, Box 12,Ridgewood, N.J. 07451 (201) 444-0196.

7-70-2t

RCA TK60 field chain, ready for studioor remote. Includes sync gen. tripod,waveform monitor, video monitor. andcabinet. Also TK30's, TK31's, MTI ORTHI's. and MTI solid state monitors. HeflinElectronics, Box 53B, Schwenksville, Pa.19473. 7-70-1t

Help Wanted

Job Headquarters for all Radio and Tele-vision Engineers. Immediate openings ex-ist in 9 western states and elsewhere forqualified engineer and technical person-nel. All categories from trainees to ex-perienced transmitter maintenance. chief.assistant chief, live color video mainte-nance and technical operations. Send usyour complete resume now. The AMPSAgency, 3924 Wilshire Blvd.. Los Ange-les. California 90005. Telephone DU 8-3116. By Broadcasters-For Broadcasters.

11-68-tf

CIRCUIT/PRODUCTDESIGN ENGINEERS

The engineers we seek willinclude their talents inVideo. Audio and Computerrelated circuitry designingproducts for the TelevisionBroadcasting Equipmentmarket. Send resume to thepersonnel manager, VitalIndustries, Inc., 3614 S. W.Archer Road, Gainesville,Florida 32601.

Metropolitan NYC and surrounding states.BSEE provides sales and technical ser-vices for out of town firms. Flexibleworking arrangements. Broadcast Engi-neering, Dept. 238, 1014 Wyandotte St.,Kansas City, Mo. 64105. 7-70-3t

Position WantedFirst Class Radio Telephone Licensee de-sires job as Transmitter Technician, pre-ferably in the south east, but will con-sider other locations. Available after 15October. Contact TSgt Duane L. Mitchell,105 North Boundary Ave., Proctor, Mn.55810. Phone 218-624-9138. 6-70-2t

Services

CUSTOM CARTRIDGE RELOADING, andrefurbishing. Fidelipac replacement partsand cartridges. Write us today for prices.PROFESSIONAL AUDIO SERVICES,BOX 1953, FORT WORTH, TEXAS 76101.

6-70-6t

Training

To advance in electronics, knowledge andability are required. Grantham offerscorrespondence and resident instruction.in depth, leading to the degree of Asso-ciate in Science in Electronics Engineer-ing. G. I. Bill approved. Credit for pre-vious training and experience allowed.Free Catalog. Write: Dept. E-2, GranthamSchool of Electronics. 1505 N. WesternAve., Hollywood, California 90027. 6-67-tfFirst phone through tape recorded lessonsat home plus one week personal instruc-tion in Washington, DC. Atlanta, Boston.Detroit. New Orleans. Minneapolis. Se-attle, Denver. Portland, Los Angeles.Proven results. Our 17th year teachingFCC license courses. Bob Johnson RadioLicense Preparation, 1060D Duncan. Man-hattan Beach, Calif. 80266. Phone 213-379-4461. 1-69-tfIMMEDIATE OPENINGS: Qualify for anyof the following positions: RCA CCTVEquipment, monochrome or color. Sales-men - TV Systems Engineers - ProjectEngineers - Supervisors - Managers -Maintenance Technicians - Video Engi-neers - to work either New York, Penn-sylvania. New Jersey or California area.Write: RCA Rep.. P. 0 Box 268, NewHyde Park. New York 11040. 4-70-tf

FCC 1st PHONE LICENSE 6 -Week CourseResults Guaranteed. Institute of Broad-cast Arts, Sharon Broadcast Training,Inc. WPIC, 2030 Pine Hollow Blvd.Sharon, Pa. (near Youngstown, Ohio).

7-70-1t

WantedWANTED: Used Allen Mod/Demod Mode1114 for VR1000-Ken Blue-SacramentoState College Television, 6000 Jay Street,Sacramento, California 95819. 7-70-1t

GET COMPLETEDETAILS

about the productsadvertised or described

in this issue.

Use FreeReader Service Card.

Be sure to includeyour name and address


ANY NUMBER CAN PLAY.The time is tomorrow. The name is TEAC. The machines are the Simul-trak'Series TCA-40. And they're here today.

This series of tape decks combines the best features of high -qualityquarter -track, two -channel operation with four -channel stereo capability.It's the best of two worlds, in three versions, four channels.

All three models feature four -channel playback, as wellas regular two -channel playback with auto reverse. What'smore, Models 40 and 41 can be modified later to the fullfour -channel capability of Model 42, at moderate cost.Meanwhile, any one of these machines is compatible withyour present equipment; no modifications or reassemblyare necessary.

So what are you waiting for?Simul-trak' surrounds you with sound - and gives you

a headstart on tomorrow.

TEACTEAC Corporation of America 2000 Colorado Ave. Santa Monica, Calif. 90404

General Specifications Speeds -71/2 and 33/4 ips Motors -1 hyst. sync., 2 outer rotors Wow and Flutter -0.12% @ 71/2 ips Freq. Response-±3 dB 50-15,000 Hz @ 71/2 ips S/N Ratio -50 dB Crosstalk -48 dB

KEGOIM VAECT 0 0KAY/AZIS

TEAC MODEL RA -41 STEREO RECORD AMPLIFIER

TCA- 40 1/4 -track, 2 -channel stereo playback, plus 4 -channel stereo playback (in -line) 1/4 -track, 2 -channel erase and record heads for future "step-up Automaticreverse for uninterrupted playback of conventional 2 -channel tapes Readily modifiedto TCA-41 or 42 Built-in solid-state preamplifiers Ideal for duplication master or copy deck

TCA- 41 (Illustrated) 1/4 -track, 2 -channel stereo playback, plus 4 -channel stereo playback (in -line) 1/4 -track, 2 -channel record Automatic reverse for uninterrupted playback of 2 -charnel tapes Readily modified to future 4 -channelrecording capability, or TCA-42 Solid-state playback and record preamplifiers Off -the -tape monitoring selector

TCA- 42 1/4 -track, 2 -channel stereo playback, plus 4 -channel stereo playback (in -line) 1/4 -track 2 -channel stereo record and4 -channel stereo record (in -line) Automatic reverse for uninterrupted playback of 2 -channel tapes Total of 8 separatesolid-state playback and record preamplifiers Off -the -tape monitor selectors

Circle Number 2 en Reader Reply Card

At WMOC Chattanooga,after 6:00PM the loudest

off -the -air sound is the

slop of the mop!

But On The Air ...Wow!

At WMOC, they lock the doors and turnout the lights each evening at 6 PM. Yetthe live modern Country -Western sound floodsChattanooga and the surrounding areaall through the night. The secret? Creativeprogramming and a remarkable SchaferAutomation System.

This amazing 24 hour -a -day AM station,featuring around -the -clock programmingof 7 of the area's top modern Country -Westerndisc jockeys, is a solid second in ratingsfor adults in the metro area-out of a toughfield of eight. And it runs completely unattendedfrom 6 PM until 6 AM -365 days a year!

Popular? You betl Profitable? Wow!WMOC has a total full time staff of only5 people; including the manager (who doesn'tannounce or cut spots), a copy writer, asecretary and a full time saleslady.

-..=,%111e-. -Plus, of course, the remarkabfkot,4.;!-*

-....

Schafer Broadcast Automation S atke

The WMOC success story is mu etthlirig 4ovu'iik,for everyone in AM and FM radio. It's Xksyours for the asking. Just mail the coupon.

schaferSchafer Electronics, 9119 De Soto Avenue,Chatsworth, California 91311 (213) 882-2000A division of Applied Magnetics Corporation

Send me the amazing WMOC success story (please print)

name

station job title

address

city state zip


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