32
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RADIO WORLD January 8, 1927
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January 8, 1927 RADIO WORLD 3
Good Back Numbers of
RADIO WORLDThe followheg illustrated artIclea have oss-word Ist recent Issues og RADIO WOIU-D:
1020:
April 3-Hew to Oct DX, by Capt. P. V.
O'Rourke, A Compact B Supply, by L.swle
Winner.
April I7-The New 1 -Dial Powertone, by Capt.P. V. O'Rourke. The Action of Transform-ers, by Lewis Winner.
May S-To Wind a Loop en a Cardboard Frame.flow to Reflex Resistance es, by Theo. Kerr.
Nay 15-Super-fleterodyne Results Brought HPto Maximum, by Herman Bernard. The TruthAbout Coll Fields, by J. E. 'Anderson.
May 22-A Bolit-to Speaker Set, by Herbert10. Hayden. The Powertone In Operation, beCent. P. V. O'Rourke.
June 5-Fire-Tube Compact Receiver, by Y. B.Andersen. A Teeter for Tube Circuits, bySpencer Hood. Problems of Portables, byHugo Clernaback.
Brae 111-BeleetIrIty'e Amazing Toll, by J. P.Anderson. The Light 6 -Tube Portable Set,by Herman Bernard
July 3-Set with a 1 -Turn Primary, by HermanBernard. Part 2 of the Victoreen Portable. byH. Bernard. Trouble Shooting Article for TheLight 6 -Tube Portable.
July 10-A Rub In Single Control, by HermanBernard. A DX Double Regenerator. byCapt. P. V. O'Rourke. A 2 -Tube Dry CellReceiver, by Samuel Schwala.
July 17-A Double Duty Loop Aerial, by I P.Anderson. How to bleure Coupling, byJohn Rider. A 1 -Control Crystal Sot, bySteedly Lyme.
July 24-Why the Super -Heterodyne le the BestSet, by Herman Bernard. A 1 -Tube ReflexReceiver, by IL A. Reed.
July 31-What's Rest In an Al' Amplifier, byHerman Bernard. A 6 -Tube Revelled Feed-back Sat, by X. D. Humphrey.
Aug. 7-The 6 -Tube Tabloid, by A. Irving Wits.The Wiring of Double Jack, by Samuel Lager.
Aug. 14-The Improved Browning -Drake, by /Ser-mon Bernard (Part 1). Storage Bettorlee,by John A. White.
Aug. 21-A New Stablilted Circuit. by K. H.Loftin Y. White (Part 1). The Brown-ing -Drake. by Heroin Bernard Mart 2).
Aug. 20-The Constant Coupling, by K. II LottInend S. Y. White Watt 2). The Browning -Drake. by Herman Bernard (Part I)
Not. 4-The Four Beat Oar Tyne., by K. B.Humphrey. A Simple Battery Charger, byJ. It. Anderson
Soot. II-Thu Beacon (3 -tubes), by James H.Carroll. The 1937 Male! Vietoreen, by Her-man Bernard.
Sept. I0-Thu 1027 Victoreen, by Arthur ILLynch. Eliminator In a Cash Sox, by PaulR. Fernald.
Sept. 25-The Lynch Lamp Socket Amplifier, byArLhur H. Lynch. Wring up ilw Victoreen.by Berman Bernard.
Pet 2-The Victoreen (Continued). by HermanIlernord. New Rquametto Pyetem, by Capt.I'. V. O'Rourke
fist 11-A Practical "A" Eliminator, by ArthurII. Lynch. Building tbo EqUareatie, by Capt.I' V. 0' Itoutke.
Oct. 10-The Bernard, by Herman Bernard. nowto Box an "A" Supply, by Herbert E.Hayden.
Sot. 23-The 6 -tube I'. 0. Samson, by Capt.P. V. O'Rourke. (letting DX on the Ber-nard, by howls Winner,
Oat, 30-The MIngtotrol Receiver. by Herbert le.Hayden How to Om Rid of Squeal.. by!lemon Bernard.
Nev. 0-Kodurtlen of Interference, by A. N.Noldemith. Variatione of Impedances, by J.10, Anderson.
Nov. 13-The 4 -tube M.Power Sol. by HerbertS. Hayden. A Study of Ffilminaters, by
I Lerman Bernard,Nov, In --Vital Pointers About 'Pubes, by Copt.
P. V. O'Rourke. The 4 -lobe Diamond ofthe Ale, by Herman Hereon!.
Nev. 2 7 --Vito Antnnnnlees Bora 1r or. by Br.Lupo ii. Man (Part It. Short Weres YieldSecrets. by M. L. Prescott.
Deg 4-The Itekenerative 6-Tobe Mot, by Capt.P. V. O'Rourke. The 8 -tube Lincoln Super,
. by !Sidney Stark. Th. Aotormoo. Receiver.by Dr, louts II. Mao (Pert Si. Whiner'sDP Eliminator, by Lewin Winner.
Dec. 11-The Bolcom! VIctoreen. by Ralph H.I Home retortion rellaoloe, by J. Si
Anderson.
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RADIO WORLD, 195 West 45th St., New York City. (Phones: Bryant 0558.0559.)
PICT REENin Super Sets meansVolume Selectivityand Satisfaction.
VICTOREEN RHEOSTATZero temperature coefficient. in-creased number of turns of wireThird terminal to simplify wiring.rive resIstanees-2, 6, 10, 20,30 ohms-$1.20 each.
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AUDIO CONTROL UNITPermits minimum number of panel controls andconsists of 3 rhomitn to of proper ohmage mountedon the bake; Ito hese. controls the second de-tector end motto tubes.Use Typo 3. It for 201 A tubes. Use Trim3- for power tube.Price -84.30 each,
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Tuned to a Preolston within one-third of one per emit-made bya pioneer radio manufacturer.Two types-No. 170 for use withregular tubes; No. 171 for drycell tubes. Price $7.00.
MASTER CONTROL UNITTills one dial unit has been so constructed thatby means of compensator controlling the antennacondenser, adjustment is permitted tip to o 90degree varlancy In capacity. with a 300 degreevernier motion. Used in circuits employing twoor more contlenaers of the Banos capacity. Bonymonnt-rui change In wiring necessary.
condenser type-PrIco $19.50.condoner-Prico $4.80.
The George W. Walker Co.6528 Carnegie Ave. Cleveland, 0.
Merchandisers of Victoreen Products
Vol. X, No. Ih. Whole No ,')50, dated January 8 9?7, of RADIO WORLD, a weekly Paper, published every Saturday by H Cot'Hennessy Radio Publicationsporsthin Irons the publication office, 148 West egth street, New York, N. Y. Telephones, Bryant 0558, 0559. Per copy, 15 cents: $6 a year. Entered asIlte,1141-Cia. matter, March, 1922, nt the post office at New York, N. Y., under the Act of March 3, 1879.
Vol. XNo. 14
JANUARY 8, 1927Whole No. 250
15e Per Copy. $0.00 a Year
RAp..10WORLD
A Weekly Paper Published by Hen-nessy Radio Publications Corporationfrom Publication Office, 145 W. 45th
Street, New York, N. Y.Phones: BRYant 0550 and 0154
(Entered as second-class matter, March, 1922, at the post office at New York, N. Y., under Act of March 3, 1897]
rhe NationaloLynchPower Amplifier and It Supply
A Raytheon Circuit for Use With the De Luxe Receiver or Any Other Set
DEEP entrancement attends dancing to the full -powered strains of music emanating from the De Luxe Lamp Socket Receiver,through the 3 -foot cone of the Enginier Service Company (in background). The receiver's tone ,is so pure, true and full that oKeimagines the orchestra is right there. The photograph was taken at the author's country house and the apparition devised with the- photograph on page 7.
THIS is the second of a series of four articles on the De Luxe Lamp Socket Receiver. These articles appeareach week in Radio World. Our technical staff attended several demonstrations of this receiver and doesnot hesitate in saying that for all-around performance it has never' heard one better.In th following article Mr. Lynch describes the theory as well as the construction of the National -LynchPower Amplifier and B Supply. This unit, though described by the author in connection with his Two -Tube DeLuxe Receiver, may be used to advantage with any receiver now on the market. 'Even though you may not desire to build any of the equipment in this series you will find that the articles areextremely interesting and describe in non -technical language many fundamentals of receiver design never beforepublished and little understood heretofore.
THE audio channel of the new DeLuxe receiver is perhaps the out-
standing development in the field ofradio receiver engineering during the
By Arthur H. Lynchpast year. Although essentially a unitof the complete De Luxe receiver, thenew amplifier is also particularly wellsuited for modernizing any other set. In
fact the improvement in tone quality andgeneral operating characteristics, whenthe new amplifier is used with such popu-lar factory -made sets as the Atwater-
RADIO WORLD 5January 8; 1927
FIERE you see Vincent Lopez himself, in person,. and nobody else but, leading h.si
mwn famous orchestra, which broadcasts regularly from WEAF and an imposing chain-of stations. To the tunes played by this orchestra the author's week -end guests 'were
dancing when the photograph on opposite page was taken. (Apeda)Kent, Freed-Eisemann, and Fada, is almostbeyond belief. Certainly the person whonow has such a receiver will never beable to imagine the tremendous differencethat the new amplifier -power unit cansnake in its performance until he hearsit. The amplifier -power unit was de-veloped after many months of experimen-tal and research work by the author inconjunction with James Millen, a well-known consulting engineer in the radiofield.- For purpose of discussion, the amplifier
and power unit, although so tied togetherelectrically and mechanically as to be,only one unit, will be treated separately.
The AmplifierFundamentally the audio channel con-
sists of a stage of impedance coupledand two stages of resistance coupled am-plification.
The input impedance is a National im-rpedaformer which contains in one com-pact unit, in addition to a high inductiveimpedance, a Tobe coupling Condenser,Lynch metallized filament grid resistorand an input radio -frequency choke coil.The RF choke is extremely important tostabilize the operation of the detectorcircuit and to prevent distortion due toaudio tube overloading as a result of the'presence of RF currents in the audio am-plifier.
Why An Impedance InputAlthough theoretically better quality
would be obtained as a result of the use"of resistance rather than impedance coup-ling in the first stage, the 'difference in'tone quality," when an impedance of thehigh quality of the National unit is em-ployed, cannot be detected by the human.ear as differing from that when using aresistance input. The advantage of an;impedance over a resistance input con-cerns mainly the new special detector-tubes, about which considerable was said.Eby the writer in the January 1 issue ofRADIO WORLD. The plate current drawn
'by such tubes is in the neighbor -'hood of 6 milliamperes at the highervalues of plate voltage recommended for-them. Such a current is considerably inexcess of the amount that even the newmetallized filament resistors will carry,Aso it is necessary to use an input device-that will safely and continuously carry atleast 6 milliamperes. As the Nationalimpedaformer will carry considerablymore than this current without difficulty-it was selected as the input unit.
The resistors used in the resistancecoupling units are of the metallized fila-ment type. They were used because of
-their high current carrying capacity,silence in operation and permanence of'ohmic value. The impregnated paper re-sistors formerly so much used in resis-tance coupled amplifiers did not possessany of these characteristics and as a re-sult did much to give resistance -coupled
amplification a poor name. Resistancecoupled amplification, employing highgrade resistors and coupling condensersis one of the most certain methods of ob-taining the very best of quality in a mostinexpensive way.
The Reasons For Each UnitThe coupling condensers are of large
capacity, 0.1 mfd., so as to reproduce thevery low notes, and at the same time arenot large enough to introduce distortiondue to the hysteresis loop of the con-denser.
CeCo high mu tubes are used in thefirst two amplifier stages because of thehigh amplification obtainable from thesetubes and because, unlike some other highmu tubes, the filaments require only fivevolts, hence function properly even afterthe voltage of the storage battery, if suchis used for A power, drops below sixvolts.
The last or final stage is a power stage.Real energy is required properly to re-produce the lower notes and the only wayto obtain real energy is from a powertube capable of passing a sizeable quan-tity of energy. There are on the marketat present at least two power tubes whichcan supply sufficient energy properly toreproduce signals at normal or naturalvolume without distortion. One is theCX371 or CeCo J-71 and the other is the210. To use the 210, however, is muchlike using a five gallon pail to carry aquart of milk. A half gallon pail is muchmore practical. As the 3-71 will supplymore than the necessary amount of en-ergy for use with the home radio setwithout the necessity of the dangerouslyhigh plate voltage required for the 210,it is quite foolish to even consider the210 under the circumstances.
Furthermore, due to its lower plate im-pedance, the use of the J -7I power tubewill result in a little more nearly perfectquality.
When receiving a very weak or distantstation, the overall amplification obtain-able may be increased by using the CX112or CeCo type F semi -power tube in placeof the CX371 or 3-71 power tube in thelast stage. The grid bias control will haveto be readiusted to a different value whenusing the CX112 or CeCo"type F, as theserequire a very much lower grid voltagefor a given plate voltage than the 3-71.
For normal use, however, the CX112or CeCo type F should not be employed asthey are too easily overloaded by loudsignals, resulting in distortion.
Using a Tone FilterThe final unit in the audio amplifier
proper is the output device. Output de-vices are of two general types, the im-pedance capacity units, known as tonefilters, and the transformers. The tonefilter arrangement is employed in thisamplifier for at least two good reasons:First, the tone filter unit is so designed
as to eliminate audio frequency currentcoupling between the plate circuit of thepower tube and the plate circuits of theother tubes. Although the phase of theAC in the plate circuit of the last tubewith respect to "the AC in the other platecircuits is generally of such an angle asnot to cause trouble, it is well worthwhile to eliminate this possible cause of"motor -boating." The second and moreimportant reason for using an inductance -capacity tone filter unit in preference toan output transformer is the fact that itis quite imposiible to manufacture foranything like a reasonable price an out-put transformer with sufficient primaryinductance to give good quality, whichwill have a core that will not saturatewhen used with the J-71 power tube with200 volts on the plate.
In a choke -coil-condenser output de-vice, the condenser should be of highcapacity -3 to 5 mfd.,--and the chokecoil of high inductance, at least 30 henrys.As the direct current cannot pass througha condenser, the direct plate current isforced to flow through, the choke coil inorder to complete the direct current cir-cuit. AC, or the fluctuating current thatactuates the loud speaker mechanism, onthe other hand, will readily pass througha large condenser, but not so readilythrough an inductance. The higher thecapacity of the condenser, the more read-ily will alternating current pass throughit, or, more technically speaking, thelower will be the impedance of the con-denser at any given frequency. As thefrequency, or pitch, of the audio currentdecreases, the more impedance, or oppo-sition, the condenser offers to the pass-age of alternating current.
How a Choke WorksNow, a choke coil has characteristics
that are just the opposite to those of thecondenser. AC will not readily flowthrough a choke. The higher the induc-tance of the choke coil, the less chancethere is of any AC being able to passthrough.
Like the condenser, the degree of op-position offered to the passage of alter-nating current by an inductance is a func-tion of frequency. In the case of the in-ductance, or choke coil, however, thelower the frequency the less oppositionthere is to its flow through any induc-tance.
As the purpose of the capacity -induc-tance output device is to separate theplate current of the last or power audioamplifier into its two components, and tomake each of these components gothtough separate circuits, it is essentialfor the best of quality that the separa-tion be complete. Thus, to prevent lossof the low notes, the inductance of thechoke coil must be sufficiently high toprevent any appreciable amount of lowfrequency audio current from 'passingthrough the choke coil rather thanthrough the condenser and speaker.
James Millen Designs Power Supply
Although Mr. Millen and the writerwere co -designers of the National -LynchAmplifier as a whole, Mr. Millen, who isa consulting engineer to the NationalCompany and one of the pioneer design-ers of radio power units, contributedmainly to the design of the power supplyand its component parts, while the writeris responsible for the amplifier design.
The power end of the amplifier operatesdirectly from any 110 -volt 60 -cycle AClamp socket and supplies constant andsilent filament power for the J-71 powertube, B power for all of the amplifiertubes, as well as the detector and RFtubes in the tuner unit, and C voltage forthe power tube. The power supply con-sists of a special National transformer,Raytheon rectifier tube, National filterchokes and special National-Tobe high
6 RADIO WORLD
AN END VIEW of the National -Lynch Power Amplifier, with the tubes in squadformation, "Corporal Raytheon" farthest from you. The other tubes are two CeCo
type G (high mu) and one CeCo type 1-71 (heavy duty power tube).
Tanuary 8, 1927
CLOSE-UP of "Corporal.Raytheon." B. H. are theinitials, and faithful duty atall times is his unblemishedrecord. He has four feetbut uses only three of them.He carries his own base withhim, like a provident sol-
dier.
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THE Two -Tube De Luxe Receiver (described in the January 1 issue) is connected to the audio circuit as shown. On the set aretwo output posts, P and Bt. Bt is connected to Bt Det. post of set and to Bt on the National Impedaformer. P on set goes to P onImpedaformer. The Lynch leak is part of the National unit.
voltage de-hidrated filter condensers, withfixed resistors and three Clarostats.
Mr. Millen was assisted in the designof the power apparatus by Phil Eyrickof Cambridge, who designed the powertransformer.
The transformer consists of a 110 voltprimary, a five volt and a seven and one-half volt filament winding, with centertaps, and a high voltage secondary withcenter tap. The secondary voltage acrosseach half is 300 volts. In order to reduce
stray magnetic flux from the transformerto a minimum, so that it will have no illeffect upon the proper action of thechoke coil, the transformer core is of theshell type and the complete instrumentis mounted within a heavy gauge metalshield. A bakelite terminal board is pro-vided with screw posts for all the lowervoltage taps, while completely insulatedflexible leads are furnished for the highvoltage leads so as to prevent any pos-sibility of shock from exposed high volt-age metal terminals.
The 110 -volt connections are madewithin the container and the completelyinsulated 110 -volt lamp socket cord isbrought out through a bushing in theback of the transformer case.
A very important feature-that of elec-tro static line noise shielding-was madeentirely automatic in the transformer byplacing the filament windings, which are'at all times within a very few volts ofground potential, between the 110 -voltwinding and the high voltage winding.
(Continued on page 23)
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RADIO WORLD January 8, 1927
runing Out Powerful LocalsMade Practical by Addition to the Receiver
A722ree Circuit Tuner
By J. E. AndersonConsulting Engineer
ILALIMINATION of interference pre-sents a difficult problem these days,
particularly to those who live in theneighborhood of a high power broad-casting station. Countless fans havevoiced complaints and asked for meanswhereby the trouble may be abated.
There are many things that may bedone which will help. All methods arebased on the two properties of a radiowave-direction and frequency. Stationstransmit on different frequencies so thatsignals differ in this respect. This dif-ference is primarily made use of in elim-inating interference. Most stations arealso located in different directions froma given receiver. This fact may also bemade use of in reducing interference.
When use is made of frequency dif-ferences between stations for cutting outinterference we speak of tuning. We ad-just a circuit in such a way that it willnot respond to more than one frequency,the one which is desired. But everytuned circuit of this kind has a limit ofdiscrimination, and that limit dependsmainly on the effective resistance in thecircuit.
Resistance Cuts SelectivityThe more resistance there is in the
circuit the less discriminatory it is, thatis, the less selective it is. If there is in-terference and the circuit is not selectiveenough to cut it out, one way of im-proving matters is to use a different coilwhich has less resistance.
If one tuned circuit is not enough totune out interference, the overall selectiv-ity may be increased by using two ormore tuned circuits in tandem, as is donein the Neutrodyne and other tuned radiofrequency receivers. But it may be thateven three or four tuned circuits in seriesare not enough to tune out a certaininterfering station, and it is not prac-ticable to increase the number of tandemtuned circuits. In that event the effect-ive selectivity may be greatly increasedby means of regeneration. This may bedone in any stage of a radio frequencycircuit by merely putting- in a tickler.
But ordinarily it is not practicable tomake any extended changes in receiversto cut out interference. The question is,What can the average fan do to get re-lief from an interfering station? Whatcan be added to the set which will reducethe interference without at the same timecutting out the signal or reducing itsstrength so greatly that it is too feebleto hear?
The only thing that can be done whichwill not at all cut down the volume is toinstall a radio frequency amplifier aheadof the main receiver. This will not onlyincrease the selectivity of the receiver
but it will also increase the volume orsensitivity. It is very easy to install anRF amplifier.
It consists of a tube and a three circuittuner. Wire it up just as a single tubereceiver was connected in the old dayswith the exception that no grid leak andgrid condenser are necessary, and the gridreturn is to negative A. Fig. 1 showshow it should be wired up.
The manner of connecting or couplingthe RF to the main receiver is verysimple. If there is no condenser in serieswith the antenna to ground circuit inthe receiver, and also if the ground bind-ing post is not connected to the filamentof the set, then it is only necessary toconnect the output terminals of the one -tube RF amplifier to the antenna andground posts on' the set. The antennaand ground leads should then be con-nected to the corresponding input ter-minals of the RF amplifier and the A andB battery terminals should be connectedto the proper posts on the main set.
How Connections Are MadeIf there is a condenser Cl in series with
the primary coil LI of the receiver, theoutput. terminals of the RF tubes must beconnected to a point below the condenserso that the plate current may flow inthe plate circuit of the RF tube. If theset proper is connected metallically tothe ground post of the set as in Fig. 1 C,then the connecting wire must be cutbefore the RF tube is connected to theset. Point X shows where the connectionshould be cut.
This addition to a set helps very greatlyto cut out interference, especially whenregeneration is used. Naturally, it in-creases the difficulties of tuning, but thatis a price that must be paid for highselectivity in nearly all circuits.
If it is not desired to use another tubeas discussed above, then a wave trap maybe resorted to. A simple and effectivewavetrap is shown in Fig. 2. It consistsof a small winding LI which is connectedin series with the antenna lead, a largerwinding L2 which is connected in in-ductive relation with Ll, and finally atuning condenser C. The coupling be-tween the two windings should be vari-able, preferably by means of varying thenumber of turns on LI. This coil maycontain a total of ten turns, variable insteps of single turns. L2 should be anordinary tuning coil, preferably of verylow loss construction, and it should havean inductance which matches with thecondenser which is used. For instance,when a .0005 mfd. condenser is used forC, the inductance of the coil should beabout 165 microhenries, or such as wouldbe given by 44 turns of No. 22 dcc wireon a 3" diameter. LI is of course woundon the same diameter or form..
The method of using this wave trap is
2 7'45. k- ZigS.
as follows: First detune CL2 as far aspossible. Then tune the receiver properto the station desired. If then there isan interfering station which spoils thesignal of the desired station, tune thewave trap to the interference. Any sta-tion within the tuning range of CL2 maybe tuned out with this combination, or atleast very greatly reduced.
The wave trap also absorbs part of thedesired signal, particularly if the desiredand -undesired signals are very close to=gether in the frequency scale. This ab-sorption is reduced by making the coup-ling between coils Ll and L2 very loose_But by making the coupling loose theelimination efficiency of the trap is re-duced. Hence the coupling should be ad-justed so that the interference is reducedto the necessary extent without seriouslyaffecting the desired signal. The wave'trap is very selective and it requires verycareful tuning to cut out the interference.
If there are two interfering stations,two wavetraps of the same design maybe used, each being tuned to one interfer-ing station.
Another effective wave trap, but onemore difficult to handle, is shown in Fig.3. This consists of a parallel circuit con-nected across the input terminals of theradio receiver. This is a shunt whichcuts out all frequencies except the oneto which CL is tuned.
Infinite ImpedanceFor the resonant frequency of CL this
circuit offers an infinite impedance andtherefore forces all the signal currentthat comes in over the antenna into theprimary of the first RF transformer ofthe set. For all other frequencies theparallel circuit CL offers a negligiblysmall impedance, and they are thereforepassed by the set.
This second form of wave trap is some-what difficult to manipulate because tun-ing the trap upsets the tuning of theradio receiver proper and vice versa.However, when the adjustment has oncebeen obtained it is very effective in elim-inating all interference. Despite this factthe first type of trap is much to be pre-ferred.
Reducing the number of primary turnson the radio frequency transformers alsoimproves the selectivity of the set andhence helps to eliminate interference.This is particularly true of the first radiofrequency transformer, that is, the onethat couples the antenna to the set. Ifthe coupling is close here the antennaintroduces a very high resistance intothe first tuning circuit and thus broadensthe set so that a great deal of interfer-ence can come through.
Hence one of the essentials of selectivetuning is to have loose coupling in theRF transformers, with particular empha-sis on the antenna coupler.
January 8, 1927 RADIO WORLD.
E
OOI
1;1
A Choice Superolleterodyneciency Factors Carefully Considered
By Brunsten BrUnnHE secret in building a five -tubeSuper -Heterodyne is to use nothing
but superior parts in its construction andmake every part operate at its peak ofefficiency. Thus the detector tube, ormodulator, should be adjusted to oper-ate with such a grid voltage that it pro-.duces the greatest intermediate frequencycurrent when fed by the output of a radiofrequency amplifier and an oscillator. Toadjust the grid voltage the grid stoppingcondenser C5 should be the standard.00025 mfd. and the resistance R1 shouldbe varied. This may be done by havinga variable resistor 250,000 (or less) to10,000,000 ohms, or by having a series offixed resistors which may be inserted intothe clips across the condenser, the onemost suitable being left in the clips.
Since the output of the detector isproportional to the square of the inputvoltage it is obvious that to obtain sen-sitivity of the circuit the input should bemade as great as practical before it isplaced on the grid of the detector. Thiscalls for a radio frequency amplifierahead of the detector. Another advantageof using a radio frequency tube ahead isthat it greatly increases the selectivityof the set, and it is an addition that isalmost a necessity in any Super -Hetero-dyne. It eliminates a certain type ofsquealing which is usually noticeable inreceivers of this type. In regards to gainin sensitivity, the RF tube will amplifythe signal about four times, and since thedetector output is proportional to thesquare of the input voltage, the effectiveamplification of the first tube is sixteentimes.
The coupling between the RF tubeand the detector should be a good low -loss tuning transformer with a fairly highturn primary. To offset any tendency tooscillate as a result of this high primarya neutralizing arrangement is employed,consisting of a coil L7 and a small vari-able condenser C3. The winding L3 mayconsist of about twenty turns of wire ona 3" diameter, and the, winding L7 shouldcontain about the same number. A 40 -turn mid -tapped coil will do nicely. Sizeof wire is immaterial, and very fine wireis just as effective as heavier. The vari-able condenser C3 may he a midget ver-nier, preferably one having a maximumcapacity around 50 mmfd. The secondarywinding L4 should consist of 44 turns ofNo. 24 double cotton or silk covered wireon 3" tubing, provided that the tuningcondenser C2 has a maximum capacity of.0005 mfd.
One of the most important things inany Super -Heterodyne is the oscillator.If the oscillator does not oscillate, thecircuit is dead: if it oscillates ever so
R/
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LS L.
Excellent engineering embodied in thisSuper-Hetrodyne, to which audio amplifica-tion may be added for speaker operation.The intermediate transformers may both be
General Radio filters (331 type).
little, the set is operative. One of thebest oscillating circuits is the tuned gridand tickler combinations as exemplifiedin this receiver. The grid coil L6 shouldbe wound on a 3" diameter tubing withNo. 24 double cotton or silk covered wire.The plate coil L should be wound onthe same form, with the same size wire,in the same direction, and it should con-tain about 36 turns. The two windingsmay be separated on the form by 14 inch,measured axially. To facilitate oscilla-tion a .001 mfd. condenser C7, is placedacross the B supply line as close to theoscillating coil as practical. For the samereason the rheostat, R3, is placed in thenegative leg of the filament line and thegrid return goes to the minus of the Abattery. The slight negative bias thusobtained makes the oscillator work onthe negative side and on the straight partof its characteristic, thus minimizing har-monics and at the same time increasingoutput.
Condenser C4 controls the frequencyand is the chief tuning control. Its cor-
, rect placement is of utmost. importance.Many complaints have come in fromSuper -Heterodyne operators because theirtuning condensers have not been con-nected correctly. The trouble is bodycapacity. The remedy is to ground therotor side of the condenser, as has beendone in this circuit. Actual metallic con-nection to ground is not required in allcases. It is sufficient if the rotor is con-nected metallically to the filament battery.A capacity connection to ground willhelp, provided the condenser is largeenough. Thus C6, a 25 mfd. unit is agreat aid in stabilizing the receiver asfar as body capacity is concerned.
Coil L5 is known as the pick-up and ittransfers the output of the oscillator tothe first detector. The closer the couplingbetween L5 and L6 is the louder will bethe signals, but the less the selectivity.It is therefore desirable that the couplingbetween these two coils should be vari-able, that is, placed on a shaft whichmay he turned from the panel. Thecoupling cannot be too close, either, be -
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icoce.11.15
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cause at a certain point of coupling thetwo tuned circuits c2L4 and C4L6 jumpin step and will not work independently.What happens is that the first circuitacts as a wave trap to the second andstops oscillations. This point of criticalcoupling is lower the lower the inter-mediate frequency is.
The stability of amplifier tubes in-creases as the frequency decreases.Therefore it is desirable from this pointof view to have a low intermediate fre-quency. A suitable one is 30,000 cycles.Transformers having a maximum trans-mission characteristic at this frequencymay be obtained on the market. Twostages of them coupled with storage bat-tery tubes will give a great increase inthe signal strength.
The second detector is as important asthe first and must be adjusted carefullyfor maximum efficiency. As in the caseof the first, the grid leak and stoppingcondenser method is used for changingthe frequency. The grid condenser CSshould be the standard value .00025 mfd.The grid leak again should be capable ofvariation within certain limits, but it isnot necessary to have a continuouslyvariable leak, but merely a supply offixed resistors in steps of about onemegohm until the right, one is found.
In the output circuit of the second de-tector the DC component of the currentis separated from the AC by means of achoke coil CH and a condenser C9. Thechoke coil should have a very high in-ductance, say 100 henrys or more. Itneed not have a carrying capacity ofmore than about 5 milliamperes. Suit-able coils may be purchased. The con-denser C9 in series with the output shouldhave a very large capacity, preferably 4mid. or more.
A variable resistance R4 is placed inseries with the speaker for controlling thevolume. This method of controlling thevolume may be employed in this circuitwithout causing any distortion becauseit does not affect the plate voltage as itwould do if it were in series with thechoke coil. The 'output is divided be-tween the loud speaker and the resistancein direct proportion to the impedances ofthe two. That is, when the value of theresistance is equal to the impedance ofthe speaker the volume is just half whatit Would be if the resistance R4 were zero.When the resistance is very high the ef-fective input to the speaker is very small,and consequently the volume is alsosmall.
A radio frequency choke coil RFC isinserted in series with the plate lead toprevent the radio, or intermediate fre-quency current, from entering thespeaker. Its value need not be large.
, (Concluded on page 31)
10 RADIO WORLD January 8, 1927
The Commonest Trouble CauseIs Mutual Imped
By Selwyn Thursten
T°judge from the number and style
of complaints received from fans, thegreatest source of poor results is thecommon impedance in the plate circuit ofamplifiers. This applies to receiversoperated by both dry cell B batteries andby B eliminators, but particularly to thelatter.
The trouble is variously described asdlucking, dripping, put -putting, motor -boating, squealing, oscillation, howling,overloading, blasting hissing and rough-ness of signals. In nearly every case thetrouble is the same-regeneration be-cause of feedback through the commonimpedance.
If the set misbehaves in a nanner thatmay be described by one or more of theabove terms, the first thing that shouldbe attended to is the impedance of thesource of plate voltage.
Remedies For the TroubleIf the audio amplifier is transformer
coupled, some relief may be obtained byreversing leads, but this is by no means asure remedy, as thousands of fans havediscovered. There are other and moreeasily applied remedies.
By-passing is one of the quickest toapply. A large condenser should beconnected across the battery or elimina-tor, particularly across the portion of itwhich is used for the detector. Thesize of the condenser to use depends onthe frequency at which the trouble oc-curs and on the value of the impedanceof the plate voltage source. If the fre-quency is high a small condenser will do,but if the frequency is low, a large onemust be used. In fact for the sameefficacy the product of the capacity andthe frequency should be a constant. Thelarger this constant is, the better. Thusa 1.0 mfd. condenser at 1,000,000 cycles,giving a constant of unity, will give al-most 100% by-passing for all reasonablevalues of common impedance.
The same efficacy would be obtainedat one cycle per second provided that theCondenser used had a capacity of 1.0
farad. But such a condenser would re-quire a skyscraper to house. Hence forthe low frequencies it is necessary to besatisfied with less complete by-passing.But in any case the condenser usedshould be several times larger than isactually necessary to stop the oscillationin order that any distortion of the signalmay be reduced to a minimum. -At thefrequency where oscillation occurs, blast-ing and overloading are likely to occurlong after the capacity has been increasedto stop oscillation.
Trouble at Low FrequenciesThe trouble often occurs at a fre-
quency considerably lower than one cycleper second, particularly in resistancecoupled amplifier receivers served by Bbattery eliminators. The better thequality of the circuit the more likely thetrouble will occur and very low fre-quencies. Old-time receivers and re-ceivers built with cheap audio frequencytransformers are not good enough toshow up the trouble, so that the °cur-rence of a very low frequency oscillationis indicative of an amplifier that iscapable of bringing out the low noteswhen it works properly. By-passing ofsuch receivers is expensive, since it re-quires enormous condensers, particularlywhen the oscillation is so low that it takesthe form of slow fading.
MC in Sets ancThere are other ways than by-passing
that may be employed. For instance,when the voltage on the various tubes isobtained from a high voltage source bydrops in resistors, separate resistorsshould be used for every plate circuit inthe amplifier. There should be no com-mon impedance, even for two circuits.Some common impedance is of coursenecessary so long as the same source ofvoltage is used for several tubes. Thesource has an impedance whether it be abattery or an eliminator. This part ofthe impedance should be by-passed by thelargest condenser that is practicable.
Another method that is usually mosteffective is to use a separate B batteryfor the detector. Even when the re-ceiver is served by an eliminator, the de-tector should be placed on a battery. Inmost cases, even the severest, the troublewill entirely disappear. However, itlargely depends on the type of couplingthat is used in the amplifier and on thenumber of tubes employed in it. Some-times it is better to use the battery on
Adjunctstwo tubes and the rest on the commonconnection. Another way of reducing thetrouble is to use a choke coil and con-denser in the output of the last tube andto connect .the speaker return to thenegative of the A battery. This by..passes the AC in the plate circuit in thelast tube almost completely and hence ithas no effect on producing oscillation.However, the impedance of the chokecoil must be very large at low frequen-cies, or the improvement will be slight.Also the condenser used in series withthe.speaker must be of large capacity,'oragain the trouble at the lowest frequen-cies will not be materially reduced.
The best and simplest way is to use aseparate B battery on the detector andperhaps on some one other tube. -
In resistance coupled audio amplifiers,if motorboating is experienced, then tryusing a larger resistor in the plate cir-cuit of the detector tube. HermanBernard discovered this remedy and sug-bests a .5 meg. resistor instead of theUsual .1 meg.
IF YOU have a 45 -volt B and a 41/2 volt C battery, and you wish to obtain 401/2volts C bias for your 71 type power tube, at 180 plate volts, connect the plus 45 of theseparate battery to the A minus, the B minus to the minus of the small C battery and theC plus of the small battery to the grid circuit of the power tube. Note the small battery
is used with reversed polarity to subtract 41/2 volts from minus 45 to make 401/2.
THE WATTMETER in the cellar tells how much electric energy is taken from theline. The energy required -to operate a B battery eliminator is so small that it makes
no appreciable difference on the monthly reading of the meter.
January h,
Radio Wave Not AlternatingSays Expert, Calling it Constantly Post
By Lewis' Rand'T'llE question has been raised as to
nhether a radio wave is alternatingor direct current or voltage. It is neither.It is not a current and it is not a voltage.It is a movement of energy in electro-magnetic form. It is capable of inducinga varying electro-motive force in a closedcircuit exposed to it. To have an electriccurrent it is necessary that electronsmove. But in free space there are noelectrons to move, yet an electro-magneticwave may pass through it. An exceptionmay be taken to the Statement that thewave is not a voltage, since the intensityof the wave may be measured in termsof volts per meter. But it may be meas-ured equally well in terms of magneticunits, that is, in magnetoetuotive force_
It is true that in the case of a verticalradio wave there exists a potential dif-ference between two points of differentaltitude, and this P. D. may be measuredin terms of volts_ But that it not all ofthe wave. There is a magnetic compon-ent which is horizontal and this may notbe measured in volts. This componentis just as much a part of the radio waveas the electric component. One cannotexist without the other.
It Varies, Not Alternates!Is it alternating in nature? All that
can be said is that it is varying in in-tensity at a certain frequency. Whetherit is alternating or not depends on thepoint of view. Consider as an analogy abody of water. Is the motion of thewater alternating? Each particle ofwater moves in a circle in a vertical planeand therefore the particle rises and falls,as the wave crest does. This motionmight be compared to the magnetic com-ponent of the radio wave. But does theheight of any particle alternate, that is,does its position alternately become posi-tive and negative? That all depends onthe level that is taken as the base_ Ifthe bottom of the ocean is taken as thebase, the height does not alternate, it isalways positive; but the height varies.That may be compared with the electriccomponent of the radio wave. If thesurface of the ocean when the water isstill taken as the base, the level or heightalternates, it becomes positive and nega-tive alternately, as a wave passes.
Another analogy may be taken frommeteorology. The air pressure variesfrom day to day, and it varies roughlyin the same way as does a radio wave.One day it is high, the next day it ismedium, and on the third day it is low,and so on. Is the meteorological wave'alternating or direct?
The Measurement DismissedThe pressure merely varies from day to
day, but it is always positive. The mo-tion of the air which results from thevarying pressure may be alternating, thatis, the wind may be northerly one day,zero the next, and southerly the third.The motion of the air is just as mucha part of the air wave as is the pressure.One cannot exist without the other inopen air.
Something may be put in the way ofa water wave to measure its height, andsimilarly something, like a barometer,may be put in the way of an air waveto measure the air pressure. A recordof these meters would show varyingheight and varying pressure. Likewisesomething may be put in the way of aradio wave to measure its intensity. Anantenna suitably coupled to an indicatoris such a meter. And in this case, asbefore, of course something may be put
ivc
To a man standing on the bottom rd a large And deep body of waterof the surface is not alternatmg always Vici-sitiee and ague iii he,distance to the surface is varying, however, between the edit*, Di -A toot Irwhere D is the mean depth of the water and A is the AtufShtstsle of the wavepressure of the water on hint as also varying nt the ea,"
of the water is circular, that is, as the wave passingthe surface describes a complete circle. On the wave ti,nt theon the crest it advances, CM the bark of the wave the water #0,,,trough it recedes. Thns the particle P traces out the each; drawn eindicated while the %save moves one wave length to the right- searthe water each particle describes tit etlitise, which degeneratesbottom. Ii the water depth is leis than A the waves break t. rashprogresses in some -what the came manner as a water wave.radio wave the electric component E is verticalhorizontal. The wave advances in a direction peep, 'the direction X. An antenna responds to the vertu-ai ov eke',a loop responds to the magnetic. But the two economies -its of the e -
and cannot he separated.
in the way of water and air waves tomeasure the speed of the moving mate-rials- Likewise something may be pot inthe way of a radio wave to measure thespeed of an "ether particle." Such am aer is a loop suitably coupled to anindicator.
When the question is railed as towhether a wave is alternating or varyingit it necessary to Fix a datum or baselevel. If the datum is so chosen thatthe pressure is alternately in sinetion and the other, it is alternating- Ifit is so chosen that it is always in Onedirection, it is varying in one (innition.or pulsating. The same holds true ofcurrent or motion.
In the case of motion it is easy to fixa datum so that the motion wilt he alter-nating. The datum is usually the posi-tion of the observer or that of his in-strument. In the case of pressure it isnot always as easy. Whe,re the observerposition may be taken as the datum thepressure will alternately be felt in onedirection and in the other. Bert if thedatum is taken as a position far away,the pressure will always be in one direc-tion, hut it may he of varying intensity.In the case of electrical potential thedatum is at a point infinitely far away.and it must be in one direction, but itmay vary in intensity from time to time.But it is possible to take the potentialof the earth as the datum, and that is
the same as to take the position or po-tential of the observer as the startingpoint. The pressure may he either inthe direction from the earth or toward
it, that io, it tn.Vftenti41 6b,
In amotive reireethat Strikes it is s,
suiting current ale,This means that the e for,- ,
ing the current is firstand then in the otherblowing in the circuitalternating E. 4f. I" tiro -
direction and then in th,fswoes riot Matter what point in ,.
chosen as the da t. r p,[14!.dikes it matter whether tbr
fir ii is alternating ear pulsating erThe, variation i. Oin thing
voltage on the grid of ,Sestilrrs!Ube is not alternating, hot varyitne Thecurrent in tbe plate rircuit is al,. , x.
ing, but Hart alternating It is Brea-;one direction. But the varyiM,:rent flOwing in the primary nf s, trail'firmer will indmse an atkmr.stmgin the secondary of tbe trareidome., is !
if the secondary is a ,11,tcurrent flowing will sttccc11.7_:!'f.
if one side of thethe filament of another tele an 1other side is tied to the grit, the es.etis open and the grid pester-it:4AI art thesecond tithe is not atternatiez. bti! fftvist.ating with the filament as Ore datr-ireiThat is, if the filament surrii,rstlypositive. It might hethe potential nf the plate an dateon
The point is that Positive and inn -ester.,demand a point nf view or a datum tasirtand that is entirely arbitrary.
American StationsCanadian authorities have called the
attention of the Department of Com-merce to the fact that American broad-casters are causing considerable inter-ference to Canadian stations.
In announcing the breakdown of regu-lations last July, Secretary of CommerceHoover made a special plea to American
Poach On CanadabroadraSteri to keep offwavelengths. Instead, a number of Amer-ican broadcasters promptly jumped to theCanadian waves with the resulting inter.ferenee and complaint.
Secretary Hoover has notified theAmerican broadcasters of the cornplaintand that's about all he can do about it,he says,
12 RADIO WORLD January 8, 1927
Direction Finder Free Electrons Playingids Loop ®f Its At Aerial Hart SignalsCapacity Pickup
(Underwood & Underwood)A RADIO direction finder of the rotat-
ing coil type suitable for use outdoors hasjust been developed by the U. S. Bureau ofStandards in Washington. The new finderis convenient in operation, portable, and hasa large range of frequencies -90 to 7,700kilocycles (3,300 to 39 meters). C. E.Dunmore of the Bureau staff is shown
operating it.
By Hari Kahn BeyA direction finder is nothing more than
a loop or coil antenna, attached to a gradu-ated circle. There may also be a compassfor orientating the loop and the graduatedcircle. It operates on the principle thatwhen the loop is parallel to the wave frontof the advancing wave no signal whatsoeveris picked up. A slight deviation from par-allelism in either direction shows a signal.If the pointer is attached to the loop insuch a way that the pointer is perpendicularto the plane of the loop, the pointer pointsdirectly to the station when the signal isminimum or zero, or it points in exactlythe opposite direction.
To determine whether the station liesahead or to the rear it is necessary toco-ordinate the observations of two direc-tion finders in different places, or else itis necessary to take two observations withthe instruments located at some distanceapart. If the distance between these twopoints is known it is also possible to deter-mine the exact location of the station. Thisis used in locating ships which art unable totake observations on the stars, for reasonsof fog, clouds and so on.
To get accurate directions with a directionfinder it is necessary to eliminate the an-tenna effect of the loop. Every loop actsas a miniature open circuit antenna, andthe pick-up of this antenna is not direc-tional. The effect of this is to unbalancethe loop and give a wrong direction.However, by means of balancing con-densers it is possible to adjust the loopso that the antenna effect is nil. Thedirection given is then the true one.
NO SUN SPOT LAWThat sun spots affect the transmission
of radio waves has been established, butnot enough data have been collected onthe subject to formulate a definite law.
(International Newsreel)The electrometer with which Dr. C. R. Wait is shown, measures the quantity of
electricity in the atmosphere. Since radio has become so extremely popular this devicehas been kept busy.
They Absorb Wave Energy, Thus Robbing the Receiver-Activeby Day, They Take It Easy by Night, Hence
Better Reception in Darkness
An electron is a very little thing and itselectric charge is extremely small. Yetwhen there are many electrons their com-bined effect may be very great. The numberof free electrons in the atmosphere has agreat effect on the operation of radio re-ceivers and transmitters and the progressof the radio wave between the two. Onaccount of the great practical importanceof the free electrons in the atmosphere itis necessary to measure them, that is, tocount the number of them in a gven space,say in a cubic inch.
To measure the number of electrons thatare flying around in the air it is necessaryto have extremely delicate instruments aswell as great skill in manipulating them.
In the usual radio calculations it is as-sumed that there are no free electrons inthe space through which the wave travels.But this assumption is not rigorously cor-rect when the wave travels through air orany material objects. There are free elec-to which the atmosphere is exposed. Someof these forces ar ultraviolet and visiblelight, the aurora borealis, X-rays and thelike.
When there are free electrons in the spacethrough which a radio wave travels its di-rection of motion is affected and its strengthdiminishes more rapidly with distance. This
accounts for the much lower efficiency ofradio during the day than during the night.Again if there is a great number of freeelectrons in the atmosphere condensers dis-charge much more quickly than if there areno free electrons. This has a bearing on theoperation of a receiving antenna. An an-tenna is nothing but a condenser, the con-ductor being one plate and the ground theother.
If there are many free electrons in thespace in which the antenna is erected acertain impinging wave will not be able tocharge the condenser to the same potentialas it would if there were no free electrons,that is, signals will be very much weakerwhen electrons fly around the antenna ingreat numbers.
"A YEAR OF TROUBLE"WASHINGTON.
Chief Radio Supervisor W. D. Terrellthinks the chief radio development during1926 was "trouble." He hopes the majoraccomplishment of 1927 will be relieffrom station interference.
"There are now too many stations forsatisfactory operation," says he. "Nodoubt Congress will be able to do some-thing about it."
P
BATTERY22%2 TO40V
r
0 0
BATTERYSWITCH
0 0 0A+ B- B+ B+ 8+
DET. 90V. 135V.
+0DETECTOR. TUBE
BATTERY .
CABLE
R.F.-CHOKE
.001 MF--- FIXED
CONDENSER
T-ANY RECEIVING SET -
LOUD SPEAKER
01.
INPU A+ A- C- 6t90 35
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:TWINICHOKE"AMPLIFIER
FIG. 5.The picture diagram illustrating the connecting 10 of a battery cable from the
unit to the set.
volts to the last tube when under load. supply about 180 to 200 volts to this tube.Some eliminators are designed for use The tone quality with an eliminator ofwith a -71 tube in the last stage and this type is exceptionally good.
January
The8,1927 RADIO WORLD
win,ChokeAudio Amplifier[The complete exposition on the theory,
building and installation of the Twin -ChokeAmplifier was discussed in last week's issue,January 1.]
By Kenneth HarknessNoted Designer of the Harkness Reflex and the
Counterflex
The exact connections of the sevenbattery cable from the unit to the re-ceiver, with the C battery and specialRabco radio frequency choke coil inser-tions are shown in Fig. 5. It will be notedthat the filament switch is inserted inscries with the A minus post. This, asstated last week, may be placed in theA plus lead, according to the individualwiring characteristics of the receiver youare now using.
A B eliminator can be used instead ofB batteries if desired. Unless the elimin-ator is specifically designed for use witha -71 tube, it will be necessary to use a-01A tube in the output. To obtaingood tone quality the eliminator must,however, be able to supply at least 135
4131-- -4)-4134
ANEL DRILL NG TEM(ACTUAL. SIZE)
PLATE-
14 RADIO WORLD January 8, 1g27A FREE Question and An-
swer Department con-ducted by RADIO WORLD
eon-
C1]l® University fart t"; its 0,7b;ZI):trIAddress Radio University,RADIO WORLD, 145 West45th St., New York City:
When writing for information give your Radio University subscription number.
(01
FIG. 491The back view of the Lincoln Super -Heterodyne.
FIG. 492The bottom view of the Lincoln Super -Heterodyne.
I HAVE two Precise audio frequencytransformers. Could I have a back andbottom view of the complete Lincoln Su-per -Heterodyne, using these transformersand a Silver -Marshall type 221 output coil,using the rest of the parts as specifiedin the Dec. 4 issue of Radio World.Please state the positions of all the parts.-Monroe Schultz, Montclair, N. J.
Figs. 491 and 492 show the views of thisset. as per request. In Fig. 491, the backview is shown. The two audio trans-formers are at each end of the subpanelin the rear. The three 20 ohm and one5 ohm rheostats are mounted in the rear,also, with the battery plug inserted be-tween. Directly in front of the plug is theoscillator coil, while to the left and righthand sides are the long wave transform-ers. On the extreme left and right handsides of the long wave transformers arethe first and second audio socket. The.other sockets are mounted near the panel.The 200,000 ohm variable resistance ismounted underneath the switch in the cen-ter of the panel. To the left and right.of this combination are the 20 ohm rheo-stats controlling the filaments of the os-.cillator and modulator tubes. The other.20 ohm rheostats control the filaments ofthr detector, first and second audio tubes."The 6 ohm rheostat controls the filaments.of the three intermediate frequency tubes.'The small midget condenser connectedin the plate return of the modulatortube, for controlling the regeneration, isplaced near the output transformer. It.can be noted by the small knob protrud-Eing from the subpanel. One of the jacks.can be seen in the lower left hand corner.of the panel, while the other is hiddenby the output transformer in the rightt hand corner. The bottom view is shownIn Fig. 492. The three 20 ohm and 6 ohm
rheostats can be clearly seen with the bat-tery plug between. Note the midget con-denser to the right, exactly to the end ofthe subpanel to the front. Any type ofmounting bracket can be used.
* * *
I HAVE a spool of No. 38 double silkcovered wire and a 1" diameter coil form._Please state the number of turns to windto constitute a radio frequency choke coil.(2) How should it be connected in the de-tector circuit to keep the RF currents outof the transformer audio amplifier. I usea non -regenerative detector.-L. MerwinGerad, Atlantic City, N. J.
(1) Wind 220 turns. (2) Break the leadof the P post which goes to the P poston the transformer. Connect the begin-ning of the winding to the P post on thedetector post socket. Connect the end ofthe winding to the P post on the trans-former. A .0005 mfd. fixed condensershould also be connected from the plateof the detector tube socket to the minusA post.
* * *
WHEN NO exact value is stated for thegrid leak, using a CX301A tube, what valueshould be used generally?-Irving Gold-enberg, N. Y. City.
Use a 2 megohm leak. A leak havinga higher value gives greater signal strengthon weak stations. It may, however, causeblocking or distortion on strong stations.
* * *
I RECENTLY heard a new station onthe air, whose call letters sounded some-thing like WBMC. I could not find themlisted in any of the station lists, I have.Could you please tell me on what wave-length they operate, by whom they areowned and where they are located?-Mor-ris Ernerst, Atlanta, Ga.
This is a new station, owned by the
Malbrook Company and located at Wood-side, N. Y. They operate on a wavelengthof 293.9 meters.
* * *
IS IT advisable to add regeneration tothe 5 -tube receiver shown on page 8, Dec.4 issue of Radio World, under the articleby K. B. Humphrey? This set was a re-flex, having the first two tubes act asRF-AF amplifiers, the third tube as a non -regenerative detector and the fourth andfifth tubes connected up in a transformercoupled audio frequency amplifier.-John Manlier, Brookings, S. D.
No, the set will be too difficult to con-trol.
* * *IS IT good practice to mount tubes
horizontally? (2) Many times I see speci-fic B voltages specified for the RF, de-tector or AF tubes in many circuits. How-ever, when I test out these sets using theseB voltages, I do not get good results. Butupon increasing the B voltage, the resultsare brought up to that point of satisfac-tion, as expressed by the designer. Doesthis hurt the tube?-Nurway Migrat,Brooklyn, N. Y.
(1) Always mount a tube vertically. (2)No, not as long as you keep within thehighest voltage specified by the manufac-turer on the carton. These voltages al-ways vary according to the different char-acteristics- of these tubes and should al-ways be experimented with, regardless ofspecified voltage by a designer.
* * *
I HAVE a fixed radio frequency trans-former, which covers from 200 to 550 met-ers. Could I have the circuit diagram ofa 5 -tube receiver, using this transformerin an untuned stage of radio frequencyamplification, two stages of tuned radiofrequency amplification, a crystal as a de-tector and two stages of transformercoupled audio frequency amplification aswell as a panel layout also. I have three.0005 mfd. variable condensers. Pleasestate the values of the coils, condensers,etc. Give subpanel layout suggestions,also.-Archie Murrels, Jersey City, N. J.
Figs. 493 and 494 show the circuit dia-gram of the set and the panel layout. Asto the circuit diagram, Ll, 1..3 and L5, theprimaries, consist of 10 turns. The secon-daries, L2, 1.4 and 1.6 consist of 55 turns.Each primary and secondary is wound ona 234." diameter tubing, using No. 22double cotton covered wire. A /4" spacecan be allowed between the two windings.The filament of the first RF tube is con-trolled by a 20 ohm rheostat, Rl. Thefilaments of the other two RF tubes arecontrolled by a 10 ohm rheostat, R2. Thefilaments of the audio frequency amplifiertubes are controlled by a % ampere bal-last R3, Amperite 112. Cl, C2 and C3are the .0005 mfd. variable condensers.They, you will note, shunt the secondariesof each of the tuned radio frequencytransformers, and are used for tuning eachcircuit. CD is a crystal detector. C4 is a.001 mfd. fixed condenser. The minus postof a C battery, which may be a 4% or 9volt type, depending upon the B voltageused, is connected to the F minus postsof both audio transformers. J is a singlecircuit jack. The grid returns of the RFtubes are brought to the A minus posts.S is a filament switch, inserted in serieswith the A plus, B minus lead. The -01Atubes should be used throughout the set.It will be found that the rheostat con-trolling the filament of the first RF tube,also controls the oscillatory action of thetube. Therefore, exercise care whenturning the knob of this rheostat. Thesame does not apply to the rheostat con-trolling the filament of the other RFtubes. The rotor plates of the variablecondenser in the crystal circuit is ground-ed. The panel layout for this set is shownin Fig. 494. A 7x18" panel is used. Thetwo rheostats p.re mounted below thelarger dials used on the shafts for thevariable condensers. The switch is insertedin the lower left hand corner, while the
RADIO WORLD 15
7119.1.1
jantlarY 8, 1927
FIG. 493The circuit diagram of the 5 -tube receiver. Using a crystal detector.
FIG. 494The front panel layout for the 5 -tube receiver, requested by Archie Murrels
jack is the opposite corner. Any size dialmay be used. As to the subpanel, the coilsmay be placed directly on the frames ofthe condensers, at angles. The fixed RFTis placed underneath the subpanel. Theaudio transformers are placed on top ofthe subpanel in the rear of the sockets,holding the AF tubes. The sockets shouldbe so mounted that the leads from thevarious transformers will be very short.This should be especially watched withthe G and P posts. Either a battery cableor binding posts may be used.
* * *
CAN VOLTAGE exist across the ter-minals of a condenser, without any cur-rent flowing? (2)-What different waysare there of storing up electrical energy?-Charles McLowd, Canton, N. Y.
(1)-Voltage, or potential difference,can exist across the terminals of a con-denser without having any current flow-ing, just as there can be a difference inair pressure inside and outside the tankwithout having any current of air.If the potential difference between theterminal of a condenser exceeds a certainvalue the condenser will break down.The analogy in the case of the tank is anexplosion if the pressure exceeds a certainvalue. The violence resulting in each caseis proportional to the energy stored in thecontainer. The energy stored in a com-pressed automobile tire is possibly billionsof times greater than that stored in thecondenser discussed above. (2)-Thereare different Ways of storing upelectrical energy. In the condenser it isstored by compression. In a primary bat-tery, as well as a secondary, it is storedin the form chemical energy. In an in-duction coil it is stored in the form ofmagnetic flux.
* * *HOW IS it possible to calculate the
capacity of condensers, where the parallelplates are separated by an insulation, hav-ing a known dielectric constant?-Law-rence Grader, Atlantic City, N. J.
The calculation of the capacity of homemade condensers is not extremely diffi-cult, particularly those composed of par-allel plates separated by insulation ofknown dielectric constant. The formula isC equals 0.0885KS divided by t, where Kis the dielectric constant of the insulator,S is the area of one side of one plate, andt is the thickness of the insulating ma -
tens!. All dimensions are in centimetersand the capacity is in micromicrofarads.If all the dimensions used are in inches,then the capacity will be obtained bymultiplying by- 2.54. The formula thenbecomes C equals 0.225KS/t micromicro-farads. If there are more than two platesin the condenser it is necessary to multi-ply the result by (N-1) where N is thetotal number of plates in the condenser.All the plates must be the same size.
* * *
IN REFERENCE to the 4 -tube receivershown in the Radio University columnsof the Nov. 6 issue of RADIO WORLD. (1)-Can resistance coupled audio frequencyamplification be employed successfully, in-stead of the transformer stages? (2)-Can high mu tubes be used in the firsttwo stages and a low mu or power tubein the last stage, using ampere ballastresistors to control the filaments of thehigh mu tubes and a IA ampere ballastresistor to control the filament of the lasttube? (3)-Is it 0. K. to connect upthese stages without any double circuitjacks intercepting the various stages, apair of phone tips being connected at theoutput ?-Henry French, Miami, Fla.
(1)-Yes. Be sure to use the properresistors in the plate circuits, e. g., .1megohm type; also in the grid circuits,
e. g, a 1 megohm resistor in the grid cir-cuit in the first tube, a .5 megohm resistorin the grid circuit of the second tube,and a .25 megohm resistor in the gridcircuit of the last tube. The couplingcondensers should be of the 25 mfd. type.(2)-Yes. (3)-Y:s.*
I AM going to construct the 2 -tubereflex receiver, using a crystal detector,shown in the Radio University columnsof the May 15 issue of RADIO WORLD. Ihave three audio transformers. One ofthese is a high ratio type, (6 to 1), whilethe other two are of lower ratio type,(3 to 1). How can they all be utilized?What changes will it be necessary tomake?-Leo Forren, Newark, N. J.
The high ratio AFT can be used in thereflexed stage, while the other two canbe used in straight transformer audiocoupling. The original hookup has asingle stage of audio coupling. However,the addition- of the extra stage is donevery easily. The plate output of the lastaudio tube in the hookup is brought tothe P post on the transformer, instead ofto the top terminal of the single circuitjack. The bottom terminal of this jackis brought to the B post on the AFT.It is also connected to a B plus post,(90 volts). The G post on the new AFTis brought to the G post on the newsocket. The F post on this AFT isbrought to a C minus post. The P poston the socket is brought to the top ter-minal of the single circuit jack, whichformally was inserted in the first audiooutput. The bottom terminal of thejack is brought into the B plus post, (135volts). The F post on the first AFT isnot brought to the A minus post as perdiagram. Instead it is brought to a Cminus post. Using -01A tubes, use a4.5 volt C battery for the first AF tubeand a 9 volt C battery for the last tube.Use a separate ballast resistor for thelast tube filament of the last tube.
* * *
I AM bit confused about the wiring upof the 5 -tube Diamond of the Air fromthe picture diagram on the blueprint.I am going to use standard variable con-densers, with the rotor plates going tothe frame. (1)-Do the rotor plates ofthe variable condenser in the tuner cir-cuit, connect to the A plus post? (2)--Do the stator plates of this same con-denser connect to the one terminal of thegrid leak and condenser combination?(3)-Is 32 necessary at the detector out-put? (4)-Can the small binding postsat this terminal also be eliminated con-necting the output of this portion of thecircuit directly to the input of the prim-ary of the audio transformer?-FrancisZander, Jersey City, N. J.
(1)-Yes. (2)-No. It just enablesyou to listen to the detector output. (3)-Yes.
Join RADIO WORLD'S University ClubAnd Get Free Question and Answer Service for the Coming 52 Weeks
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16 RADIO WORLD January 8, 1927
LOUD SPEAKERS ARE TESTED
(Herbert Photos)WILLIAM G. RUSSEL (left) and William W. Macalpintesting loud speakers in the Hartley Research Laboratory,
Columbia University.
FOR an aerial leadin standoff you may stock up two or moreporcelain insulators.
1-lomeNN eWire, Spool, N and
A simple circuit breaker for the protection of radio apparaisome heavy magnet wire, an empty thread spool, a wire nailover the gas stove to remove all temper, that is, heat it to rMount the spool vertically on the upright as shown with theand the other to a metallic plate on the baseboard directly uia certain predetermined value the nail will be lifted up and tlnail from falling down as soon as the circuit is broken, and t
provided the nail is pushed througi
319 New St.' tions1,000 Mark
More Than 116 Are Actually Under ConstrueHave Been Laid for 203 Additional-N
by Commerce Department
WASHINGTON.Increased understanding of the vagaries
of radio waves which has made it poss-ible to calculate definitely the servicethat can be obtained from a given trans-mitting station was one of the chief radioaccomplishments during 1926, accordingto Dr. J. H. Dellinger, chief of the RadioLaboratory of the Bureau of Standards.
"There were noteworthy contributionsto the understanding and control of thevagaries of radio wave transmission,"says Dr. Dellinger. "For many years in-tensive work has been done in improvingradio transmitting and receiving appar-atus, and the results of this work havefrequently been spoiled by the thingsthat happened to the radio waves in pass-ing from the transmitter to. the receiver.
"Further advance has, therefore, de-pended upon better knowledge of thetransmitting medium. This has led tostudies of wave transmission and severalimportant contributions to the subjectwere published during the year. Theyreveal many facts in regard to the natureand causes of fading, signal variation, at-mospherics, and other vagaries of re-ceived radio signals.
"The results all tend to corroborate thehypothesis which was conceived a fewyears ago of the effect of an upper con-ducting layer in the earth's atmosphere.This upper conducting layer, called theKennelly -Heaviside surface, has now beenlocated. Its height is found to vary atdifferent times of year and day all theway from 50 to 500 miles above theearth's surface. The action of this con-ducting or reflecting surface explains theenormous distances of transmission atnight and on high frequencies. It alsoaccounts for fading and skip distanceeffects.
"This knowledimission on anmakes it posibtthe service thatgiven transmittinage of this wort(connection withshort waves. Hparticularly erratinvestigations ofpossible to taketremendous carp
"An outstandir1926 was the pertelephony. A d(telephony betwe,don was conducAmerican Telephpany and the Brment. The systcpoint of being rcmercial- use, soscriber in the Urpersons in Grea
"The outstaybroadcasting hasest and importanto local receptionwrought by a tclarly the expanscasting and thestrictions. For aare able to obtattures through ain a station chslargely paid forresult many brcbecome self-supfof program time.tion of station i
very large amochaotic conditioncention."
There are mor
January 8, 1927 RADIO WORLD 17
Circuit Itreakerlips Constitute Device
nay be made out of materials at hand in every house. Required.ouple of Fahnestock clips and a wooden board. Heat the nailss. Wind the spoolfull of double cotton covered wire, say No. 20.inside. Connect one terminal of the line to the head of the nail
_:'the point of the nail. If the current through the coil exceeds- Teak the circuit. A Little friction on the nail will prevent theriction will be supplied by the paper on the end of the spool head
without removing any of the paper.
Sight1, While PlansSurvey
placing radio trans-) ineering basis and
calculate definitelybe obtained from aation. The advant-:specially marked inhigh frequencies orrequency waves areut as a result of the
'3: behavior it is nowadvantage of their
power.idio achievement ining of trans -Atlanticstration of two-way
i Few York and Lon -,c last Spring by then and Telegraph Cor-is Office Depart -,as developed to the
d for opening to eorn-i, any telephone sub -
States can talk with).'ritain.In- development ino'n the shift of inter -r'! -om distant reception
'his change has beenal:r of causes, pardon-,rof toll chain broad-rnoval of license re-
: jority of the listenerse best program fea-
al station connectedki , These features areft. advertisers, and as asa asting stations have
ng through the salee uncontrolled selec-encies has led to a
ri of interference anddistant station re -
,an 600 stations now.
17 New StationsWASHINGTON.
Seventeen new stations have beenlicensed by the Department of Commerce,two of which are of high power. Bothof these are equipped to use 1,000 watts,one on 340 meters, where interferencemay be caused with Lincoln, Nebraskaand Manhattan, Kansas. The other willoperate on the Pacific Coast, and distanceplus time difference may prevent inter-ference.
NEW STATIONSkc. m. w.
WRSC-The Radio Shop,Chelsea, Mass. 1110 270.1 15
WLBA-J. C. Van Horn,Philadelphia, Pa. 1270 236.1 50
KYA-Pacific BroadcastCorp., San Francisco,Cal. 750 399.8 1000
WBET-Boston Trans-cript Co., Boston, Mass. 780 384.4 100
KGDZ-Norwegian Lu-ther College, Decorah,Iowa 696 431 50
WTRL-Technical RadioLaboratories, MidlandPark, N. J. 1070 280.2 15
KGDY-J. Albert Lo-esch, Oldham, S. D 1428 210 15
WLBN-W. E. Hiler,Portable 1330 225.4 5
WLBP-R. A. Fox, Ash-land, Ohio 1360 220.4 15
WLBQ-E. D. Trout,Atwood, III. 1300 230.6 25
WLBJ - Henry Gross-man, Cleveland, O 999 300 100
WLBO-F. A. Trebbe,Jr., Galesburg, Ill. 1234 243 100
WCOM - 172nd FieldArtillery, Manchester,N. H. 1190 252 100
WLBR - Alford RadioCo., Belvidere, Ill 895 335 15
WMPC-First Metho-dist Church, La -peer,Mich. 1239 222 100
WOKT-Titus-Ets Corp ,
Rochester, N. Y. 882 340 1000WBSO-Babson's, Wel-
lesley Hills, Mass 1239 242 100
[See article on page 14 if you suffer frominterference.]
HANDY WAY TO MOUNT COIL
(Hayden)BUS BAR can be used to a great advantage for mountingcoils. The upper photo shows a portion of the wire beingbent into a U shape for the coil and another portion of thesame wire into a circular shape for the insertion of the screw.The insertion of the screw and the mounting of the coil is
shown in the bottom photo.
(Hayden)WHEN CONNECTING up the phone tips to the plug, besure that you insert the cords with proper polarity. The
positive cord is always indicated by the red stripes.
18 RADIO WORLD January 8, 1927A THOUGHT FOR THE WEEK
NOW that the more or less official holidaysare over, radio fans can settle down to
a long Winter of listening and waiting-andthe success of the whole thing will be basedon the Percentage of each. It looks like agreat 1927 for radio from where we aretuning in.
RAD IRE G. U.S. PAT. OFFt,
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INTERESTING FACTSLight is the same thing as radio waves,
the only difference being the length ofthe waves. The wavelength of yellowsodium light, that which is most fre-quently seen in flames, or when commonsalt is thrown in a flame, is about onebillionth as long as the 600 meter waveused by ships.
* * *
About 40 years ago Heinrich Hertzdemonstrated experimentally the exist-ence of electro-magnetic waves andproved the correctness of Maxwell'stheory. Herzt was the first human beingto send and receive radio waves. Hiswaves were very short.
About 25 years ago Guglielmo Marconifirst set up radio transmitting and re-ceiving of commercial significance. Hewas the first to send messages by radiowaves.
* * *
The term farad comes from the nameof Michael Faraday, one of the most pro-lific of all investigators of electrical andmagnetic phenomena.
* * *
The ampere takes its name from Am-pere, a French investigator in electricalphenomena.
Radio Greatly Incr asesN. Y. Edison Co. Income
Due to the large use of radios, theannual income of the New York EdisonCompany, has been increased by morethan $1,000,000. This, officials say, is dueto the use of electric sets, charging ofbatteries and sitting up late of fans listen-ing to distance, which occasions extra useof electric lights.
Arthur Williams, vice-president of theEdison Company, in charge of commercialrelations, told of the company's added in-come because of the radio while testify-ing recently before the Public ServiceCommission on a complaint that the com-pany's rates were too high. Part of thework of Mr. Williams is to increase thenumber of patrons of the company andto induce patrons to use more current.
Some of the expenditures of the com-pany are the cost of broadcasting thespeeches of some of the company's of-ficials and the cost of "Edison Hour,"consisting of entertainment broadcast byvarious stations, particularly WRNY.These costs have been criticized by As-sistant Corporation Counsel. M. M.Fertig and Joseph P. Morrissey. Thesecosts have affected the going value of the
company, which is part of the basis onwhich rates are fixed.
Mr. Williams said that the company'sexpenditures for radio programs repre-sented a most desirable branch of thebusiness -getting activities of the com-pany. He explained that investigationsmade by the company indicated a grow-ing tendency among radio owners to stayat home at night. Mr. Morrissey askedthe witness whether the radio had nottaken the place of the saloon and Mr.Williams replied that he believed it had.Mr. Williams proceeded to explain howthe increased consumption of electriccurrent benefitted the company by say-ing:
"We find that many complaints aboutthe lighting billS are more easily satisfiedbecause, when a customer complainsabout his bills, we ask him if he has aradio. If he says that he has, we remindhim that perhaps the radio induces himto sit up later, with the result that morelight is used. In practically every casewe find that this explanation satisfiesthe complainant."
The board was deeply interested.
ILA LandoGrant CollegesOper to Large Stations
ST. LOUIS, Mo.Extensive use of radio for spreading
information on agriculture and homeeconomics by land-grant colleges has beenreported to C. W. Warburton, directorof extension work of the Department ofAgriculture. The statement issued by theExtension Service on the use of radiofollows:
Nearly all of the land-grant collegesof the country are now using the radioin some way or another for disseminat-ing information on agriculture and homeeconomics. This is shown by returns re-ceived from a questionnaire sent to all thecolleges by C. W. Warburton. The re-turns show the following:
Thirty-four states are providing for thebroadcasting of extension programs, theuse of the radio varying in degree fromoccasional discussions of agricultural andhome economics subjects from commer-cial stations, to elaborate courses of lec-tures from the stations of the institutions.
Fourteen land-grant colleges of the in-stitutions of which they are parts, areoperating broadcasting stations withpower of 500 watts or more. In this listare Maine, Connecticut, Alabama, Arkan-sas, Texas, Michigan, Ohio, Wisconsin,Iowa, South Dakota, Kansas, New Mex-
ico, Oregon and Washington. Coopera-tive extension material makes up a con-siderable part of the programs of theseinstitutions at present. Stations of lowerpower than these are operated by Ver-mont, Indiana, and North Dakota forbroadcasting extension programs regular-ly or occasionally.
Commercial stations are used by 10States for broadcasting regularly, eitherby direct control, remote control, orthrough the furnishing of manuscriptmaterial to be broadcast by the stationannouncers. These States are Massachu-setts, New Jersey, New York, Maryland,Georgia, Oklahoma, Missouri, Minnesota,Nebraska, Colorado and Idaho.
Ten States-New Hampshire, Pennsyl-vania, Delaware, Rhode Island, Virginia,West Virginia, Illinois, Wyoming Mon-tana and California-occasionally con-tribute material to commercial stationsfor broadcasting by those stations, or,if opportunity offers, representatives ofthe colleges do the broadcasting.
Illinois has a station of its own underconstruction, and plans to send out pro-grams of agriculture and home economicsfrom this station. New York has plansfor an institutional station of its ownsoon to be erected.
Klan Members In RegaliaStart Fund for Own Station
PATERSON, N. J.Plans for the construction of a radio -
broadcasting station in this city are beingconsidered by the allied organizations ofthe Ku Klux Klan, according to an an-nouncement made at the close of theservices in the Wanaque ReformedChurch recently. Members of the alliedorganizations of the Klan attended theservices clad in full regalia.
Towards the close of the service theannouncement that the Klan intends tobuild a radio station was made. A specialcollection was taken for the btoadcastingstation fund after the members of theklan had contributed to the regularchurch collection.
WHAP Lecturer Is BarredFrom Jury for Prejudices
Charging Franklin Ford, announcerand special theological lecturer at WHAPof New York City, incompetent to rendera fair and impartial verdict, Judge OttoA. Rosalsky in General Sessions, recentlyexcused him from jury duty.
Mr. Ford's statements from the stationwere regarded as propaganda againstJews and Catholics. Mr. Ford said thateven though he had denounced certainteachings of the Catholics and Jews, theseideas would have no effect in changinghis decision toward a defendant, who inthis case was a colored man.
During the examination it was disclosedthat the station was sponsored by Mrs.Augusta E. Stetson.
January 8, 1927 RADIO WORLD 19
of1Fach rutbe I s L.,1 Tiny Ni
Electricity cashing From theJust As Water May Be Boiled to Give Off Invisible Vapor, So May
Certain Metals Be Heated, As In the Filament, to DischargeElectrons-Tremendous Quantities of Infinitely Small ParticlesAre Released-Why a Tube, Like Every Cloud, Has a SilverLining.
By Dr. A. N. GoldsmithChief Broadcast Engineer, Radio Corporation of
America
MUCH ado about nothing" "was thetitle given by Sheakespeare to
one of his famous plays. Yet the vener-able Bard of Avon, had he lived today,could have found no better title with whichto label the modern vacuum tube. Thevery nothingness of the vacuum tubeis its most important feature; for withoutthe vacuum, this device could not be; andwithout a high degree of vacuum, or vir-tually nothing, a good vacuum is, in gen-eral, quite impossible.
Now in order to get a true picture of thevacuum tube and its work let us start withan analogy. Consider, if you will, a dam,impounding millions of gallons of water.At one side there is a spillway, togetherwith a system of flood gates. A man,through the agency of a lever, can read-ily control the flow of water over thespillway, from a mere trickle to a com-petitor of Niagara.
In the vacuum we have preciselythe same state of affairs, although in elec-trical rather than mechanical form. Thereis a vast quantity of electricity impoundedin the tube filament and ready to pourforth when the filament is heated.
Flows from Filament to PlateThe flow of electricity is from the heat-
ed filament over to a cold surface of metalcalled the plate. However, this electricalspillway is controlled by a flood gate inthe form of a screen or mesh of wireplaced between the filament and plate andknown as the grid. The slightest variationin electrical charge on the grid imme-diately controls the flow of electricityfrom filament to plate.
Just how the vacuum tube accomplishesall this is a much longer story. Everybodyknows, first of all, that water can be boil-ed. What happens? Well, the water isconverted into an invisible vapor and dis-appears in the air. Likewise, almost every-body knows that camphor, left about thehouse at ordinary temperatures, willeventually disappear. Why? Because thecamphor has evaporated-tiny particles ofcamphor have been flung into the air topermeate it with the strong odor whichdrives off moths.
Few persons, however, know that elec-tricity can be boiled out of hot metals.Yet such is the case. A metal wire, suchas tungsten, when heated to incan-descence, will liberate tremendous quan-tities of tiny electricial charges, forming averitable fog or mist of infinitesimal pro-jectiles, called electrons, which leave thewire in all directions.
The Waterway ParallelSo here, then, we have an electrical
reservoir, a spillway, flood -gates and theoperating lever. Just as water flows overthe spillway and down the valley,so electrical charges or electrons can flowout of the hot filament and over to thecold plate in the vacuum tube, providedtwo things occur: First, that the spacebetween contains only almost infinitesimalquantities of gas; otherwise stated, itmust be a high vacuum, or the electrical
particles or electrons will collide with theremaining particles of gas and cause aserious deterrent action. Secondly, thatthe plate of metal be in proper electricalcondition to attract the electrical chargesto itself. We keep the plate in this propercondition by shaping and placing itproperly and by connecting it to one sideof an electrical source in the form of aB battery or B eliminator (socket powerdevice). The filament, on the other hand,is heated by means of current from theA battery or A eliminator. Thus we have established a constant
stream of electrical particles, quite in-visible yet very real, across the vacuum,or from the heated filament to the coldplate, while from the latter the electricalparticles in the form of electric currentcan flow out of the tube. We have, there-fore, an electrical Niagara.
The Grid Controls ElectronsBut how are we to control this electrical
Niagara? What is to correspond to thesystem of flood gates and the controllever of the dam? The solution is offeredby the grid. It was discovered some yearsago that an open work structure of metalcould be placed between the filament andthe plate, so that very trifling changes inits electrical condition would greatlychange the stream of electrons passingfrom the filament to the plate. Here, then,we have a potent, instantly responsiveelectrical control mechanism. The mostminute electrical charges impressed uponthe grid, even at a tremendous rate ofspeed such as radio frequencies with mil-lions of changes per second, cause muchgreater yet substantially identical changesin the electronic stream.
A vacuum tube, therefore, comprises(1) a filament; (2) a plate; (3) a grid;(4) a glass envelope or bulb ; (5) a basewith prongs, or contact pins for externalconnections. The functions of these mem-bers are obvious from what has gone be-fore.
In a general way, then, what are therequirements of each of these members?Well, taking the filament first, here is amember which must be a copious emitterof electrons at reasonable temperaturesto insure long and economical life.
Precision Is RequisiteThe lower the operating temerature of
the filament, the less the cost of main-taining the filament lighted, because ofthe lowered battery drain. Originally,chemically pure tungsten was consideredan ideal filament material, but a brilliantscientific inspiration led to a better sub-stance for tube filaments.
The plate and the grid must be precisein dimensions and most carefully mountedin exact relation to each other and thefilament. The necessarily delicate fila-ment-it can hardly be seen except whenlighted-must be delicately mounted so asnot to vibrate or shake from powerfulsound waves, of a nearby loudspeaker.Otherwise, the tube is "microphonic". Theplate and the grid must be scrupuiciuslyclean, so that they cannot give off gas orimpurities to interfere with the operationof the tube.
The leading -in wires passing through
',el garaFilament
THE GRID WIRES, shown in sectionabove, are negatively charged and thusthey repel the electrons coming from thefilament. Fewer electrons can reach theplate when the grid is in place than whenthere is no grid. It is only the faster ofthe electrons emitted by the filament thatcan sneak through the openings and getby the grid. Once they are through thegrid pushes them toward the plate and the
plate pulls them.
the glass must be of a kind that will notexpand or contract at a different ratefrom that of the surrounding glass. If theexpansion should be too rapid, the sur-rounding glass will crack; if slower, a leakwill be formed and the vacuum jeoparded.A cleverly conceived bi-metallic wire,known as dumet, is used for the bestvacuum tubes, insuring a tight seal at alltimes.
Fine Work is Vitalmethods have had to be evolved. Pump-ing alone could not achieve the highvacuum in a sufficiently thorough andrapid manner to meet the demand formillions upon millions of vacuum tubes.Here again, a clever inspiration has pro-vided what is in reality a vapor broom.Now the housewife would hesitate tosweep a room with a metallic fog. Cer-tainly a husky broom would be preferred.Yet vacua are swept with a metallic fog.A small quantity of suitable chemical,called the `getter", is placed in the tubeat the time of assembly.
Why the Silver LiningFollowing the sealing operation, when
the vacuum pumps have done their bestin the time allotted to them in quantityproduction, this "getter" is vaporized, inwhich form it combines with the remain-ing gas atoms and finally condenses onthe cool glass wall. And so the brightsilvery coating we see on the vacuumtube is the sign of good housekeeping ona minute scale. It signifies that the tubehas been swept clean.
20 RADIO WORLD January 8, 1927
.
The De Luxe Lamp Socket Receiver
3 ivNLTILYNCH POWER AMPLIFIER
NATIONAL TUNINGUNITS
-c omprise the wonderfulBROWNING -DRAKE R. F.Coils and Transformers withtheir SLOTWOND primaryand SPACEWOUND secondaries, EQUICYCLE wide -spacing condensers and vEL.VET VERNIER Dials. They
make good Radio sets.
NATIONAL ThdPEDA-FORMER-Type B
-includes in one case audiochoke coil 0.1 Mfd. TOBECondenser, mounted LynchResistor-for modem audio
amplification.Price OM each
THE NATIONAL -LYNCH Power Amplifier is a new com-bined B -power supply and 3 -stage audio amplifier, for usewith either the Raytheon BH or Rectron Tubes, and with
the UX-171 semi -power tube in the last audio stage. Made tobe connected instantly to the detector output of any set andgives real fidelity of reproduction.
Designed in collaboration with Arthur H. Lynch and JamesMillen. The fine appearance of this new instrument is but areflection of the quality packed within it.
The amplifier employs one stage of impedance and two of resistancecoupling. The output is through a NATIONAL Tone Filter, for protectionof loud speaker windings and further improvement of quality. The partsmount on a drilled and cored metal base in which all of the wiring isconcealed and protected. When connected to a first quality loud speakerthe fidelity of reproduction is limited only by that of the broadcast stationbeing received.
Price-Completely assembled and tested without tubes(state whether BH type or Rectron UX-213 is tobe used as rectifier) $89.00BH Tube extra $6.00
Price-NATIONAL-LYNCH Power Amplifier, in kitform, complete for assembly in one evening, withinstructions and BH Tube $84.00
NATIONAL products are builtto engineering standards of ex-cellence. Anyone who has everbuilt a set using NATIONALBROWNING -DRAKE Coils andTransformers knows what thatmeans. Send far Bulletin 116-W-1.
National Co., Inc., Engineers andManufacturers.-W. A. Ready,Pres., Cambridge, Mass., Makersof NATIONAL BROWNING -DRAKE Coils and R.F. Trans-formers, Impedaformers, Con-densers, Power Transformers,
etc., for Radio.
January 8, 1927 RADIO WORLD 21
F.
The De Luxe Lamp Socket Receiver
rVOSSAvWvk
Why the experts Choose the
LMETALLIZED
AMNWMIV
As Great an Advance asthe Tungsten Lamp
The old carbon lamp con-sumed more current to giveless light. Tungsten, whichis metal, proved more eco-nomical, more efficient. Itmeant more light, longerlife. Lynch Metallized Re-sistors are warranted abso-lutely noiseless, permanentlyaccurate, dependable.
Fixed Resistor
For BetterFilament Control
The NEW LYNCHEQUALIZORS - atype for each tube,and for any combi-nation of tubes.Complete, with Bet-ter - Built Mounting,$1.00.
Right Onthe Button,' PRICES
.25 to .10 MegohmsAbove .01 to .24 "
.001 to .01 "Single Resistor MountingDouble. Resistor MountingEqualizor, all sizes
TAMES MILLEN uses and endorses theLynch Metallized Resistor.
In describing the construction of experi-mental receivers, amplifiers and power units,it is significant that such authorities asLaurence M. Cockaday (Popular Radio),Herman Bernard (Radio World), E. M.Sargent, G. M. Best (Radio), and many othereminent designers specify Lynch MetallizedResistors.
These men know radio. They realize theimportance of resistors that will remain ab-solutely noiseless, permanently accurate,efficient, dependable - and they chooseLynch. There could be no greater testimonyof the true worth of our product.
s -so.75
1.00.35.50
1.00
ARTHUR H. LYNCH, Inc.FISK BUILDING
Broadway and 57th Street, New York, N. Y.
A concentrated metallized de-posit one -thousandth of aninch thick upon a glass coregives conductive, non -arcing,silent, resistance that winsin the acid test of time. Dealers-Get Our Free Advance
Information Service.
97 RADIO WORLD January 8, 1927
The De Luxe Lamp Socket Receiver
ClAROSTATthe greatest variable resistor!
SCORES AGAINSelected by
ARTHUR H. LYNCH for
THE DE -LUXELAMP SOCKET
RECEIVER
That's what 59 leading Beliminator manufacturersare doing. After exhaus-tive tests, they are con-vinced that only CLARO-STAT acts as the perfectvoltage control because . . .
it has a range of frompractically zero to5,000,000 ohms . . .
it has a, current carry-ing capacity of 20watts - greater thanthat of any othervariable resistor -without slightestdanger of packing,arcing or cracklingnoises.
Have you sent for your copyof "The GATEWAY TOBETTER RADIO"? Theedition is limited and youcan't afford to be without it.32 pages covering everything- reception, transmission,amplification and batteryelimination. Send 25c instamps or coin to Dept. RW.
American Mechanical Labs.285 N. 6th St., Brooklyn, N. Y.
Type U.X. UniversalPrice 60c
IRGAPSOCKET
Vtgets that fast mile'Specially Recommended by
Arthur H. Lynchfor the
DE LUXE RECEIVER
AIRGAP PRODUCTS CO.
Type U. V. StandardPrice 60o
Send direct Post-paid if your Dealer cannot supply you.10 CAMPBELL STREET NEWARK, N. J.
ARTERParts Specified for
LYNCHDe Luxe Receiver
1a
USS
ACarter parts are specifiedfor this efficient amplifier.
Whenever you find a cir-cuit that's popular and asuccess, you'll find Carterparts specified. In fact,much of the success of anycircuit is due to the carefulselection of parts.
If you're not now usingCarter parts, try them.You'll find, like thousandsand thousands of others,that Carter parts performwith a consistency and per-sistency unequalled.
Any dealer can supply(Pat. 1-30-23)
Full SIze 65c"IMP" Battery Switch
In Canada: Carter Radio Co., Ltd., Toronto
ARTER CO.CHICAGO ;Ca'
EL1KiWkQUALIZOp_up
selected personally Icy Arthur H. Lynch forthe Two -Tube De Luxe Receiver de-scribed In this issue and made by TheLangheln- Kew! man Radio Co. (Dept. W.),62 Franklin St., New Haverc, Conn.Write for prices and tables of values.
PRECISE 940 MICRODENSERSeries Antenna Balancing CondenserEspecially Designed for the Browning --Drake
ReceiverSelected and Specified by
Arthur H. Lynchfor the De Luxe Lamp Socket Receiver
100 Mmf. Capacity, $1.75A Precise Laboratory Quality InstrumentAlso made in 10, 20, 30, 55 and 135 Mmf. Cap.
PRECISE MANUFACTURING CO.ROCHESTER, N. Y.
New York Office: 126 Liberty Street
"HAMMARLUND, JR."The high -ratio shielded midgetcondenser, especially selected byMr. Arthur Lynch for use in the
De LuxeLAMP SOCKET
RECEIVERFeatured in RADIO WORLD
Made in four sizes for any circuit wherea small variable capacity is advan-tageous.
Write for PolderHAMMARLUND MFG-.,CO.424-438 West 33rd Street New York
3-0,1., Rattan. Radio-
ammarlundPRECIS/ON
PRODUCTS
ArthurLynch hasselected theFtadiohm tocontrol hisnew WonderSet.
With Switch$2.30
January 8, 1927 RADIO WORLD 23
The De Luxe Lamp Socket Receiver(Continued from page 6)
The filament windings are thus made toserve as a most excellent electro staticshield.
Raytheon Tube Used as RectifierThe rectifier tube used with the power
transformer and associated apparatus yetto be described for obtaining the B andC voltage is of the Raytheon filamentlesstype. The Raytheon tube was selected inpreference to others because of its .mark-edly superior performance when putthrough exhaustive laboratory tests byboth Mr. Millen and the writer. Althoughfor some uses the 213 tube was found tobe quite satisfactory, when used at thehigh currents and voltages to which therectifier tube in the National -Lynch am-plifier is subjected, its life was exceed-ingly short. Such was not the case, how-ever, with the Raytheon tube. Severaldifferent types of "bootleg" Raytheontubes were also tried, and without ex-ception, all those tried were found to bequite worthless, as their useful lives werebut a few hours under full load.
Two 0.1 mfd. high voltage Tobe con-densers mounted in a single case located
CentralsPAT -3-13-23
(MIER PATS PENN
STANDARDT.% centralato 11ffadioh
INSURES clearer, loud-er reception with mostany radio circuit. It
holds perfectly the sen-sitive regenerative posi-tion which immediatelyprecedes the oscillationpoint.Dependable,noiseless inadjustment, and full re-sistance variation with asingle turn of the knob.Resistance values re-main exact for life ofset. $2.00 for any re-sistance.
SWITCH TYPERcentralabioHas an "A" batteryswitch, also controlledby the knob, giving adouble purpose control.Is variable from zeroto 5oo,000 ohms. Alsofurnished in Modula-tor, for tone volumecontrol in all audiocircuits.
CENTRAL RADIO LABORATORIES'19 Keels Ave., Milwaukee, Wis.
Makers of a full line ofvariable resistances for69 makers of leading
standard sets.
tell
under the base of the amplifier and knownas "buffer" condensers are used to insurethe most efficient operation of the Ray-theon tube. Occasionally, when they arenot employed in the circuit a cracklingnoise, much like static, is heard in theloud speaker. The buffer condensers
(Continued on page 26)
CeCo TUBESSPECIFIED BY
ARTHUR H. LYNCHFOR THE TWO TUBE
. DE LUXE ...RECEIVERType El-Special Detector $2.50Type B X-199 $2.00
Ready to Mail in Special Mailing CartonUpon Receipt of Money Order.
K. W. RADIO CO., Inc.98 Park Place New York
The Tobe400 Line
Specially cased condensersfor 900 volts D. C.operating voltage. Foruse -slab Raytheon BHand similar high -voltagerectlifying tubes In B-BLitalnat6rs. Uses short -oath type condensers andis enuipped with unique
at base of can.TOBE safety terminals
Prices -1 Mfd2 If Id4 Mfd
22.002.754.50
The Tobe 600 Linenigh -voltage condensers for Et.merTranand similar high -voltage packs Big.husks 1000 -volt D. C. continuous -operat-ing voltage condensers-made to standthe gaff. Buttimed slue TOBE safetyterminals.Prices- 5 Mfd $1.75
1.0 Mid 2.502.0 Mfd 9.009.0 Mfd 7.00
Tobe Filter CondensersThe standard for general radio ustt. forall operating Voltages up to 300 voltsD. C. Used by Phlleo, National Coun-t/0.Y. General Radio Company. King Ra-dio. and many other leading manufac-turers.
Radio's Latest Necessittp-,
B H`7he%tr.POWERPLANT
MakeYon,BET
°POWERSET
CO TR i LITNo radio OM Will be without a Controlit whenhe realises how it adds to the pleasures of operation.Adding a Controllt to any set eliminates allswitches from "B" Battery Substitute and TrickleCharger and places complete, .11081331-1C controlof se and power supply in one switch-the settonmit Ind/. 9Without added wires or alteration.,the Controlit can be made a part of any set,
Price 56Specified by
ARTHUR H. LYNCHin
The De Luxe Receiver
Braci1C.Radio ProductsL. S. BRACH MFG. CO.
s of 7smen1 RR. blennnnaDept. 27, Newark, N. J.
TINY TOCONDENS
Actual Size"
S
A new TOBE product makingthe TOBE line complete, fromthe smallest to the largest fixedcondensers required in Radio.
TINYTOBES are made for con-tinuous operation up to 500 -volts D. C.,and are for all by-pass uses in Radiosets, for coupling condensers in im-pedance and resistance amplifiers andfor detector grid condensers.
TINYTOBES are specified in theLincoln Superhet., Victoreen, Samson,T. C., and many other leading circuits.
It would be hard to find a moreefficient, compact and generally ad-vantageous small fixed condenser thanthe TINYTOBE.
PRICES:.0001 Mfd., .00025 Mfd., .0005 Mfd 35c each.001 Mfd. and .002 Mid 40c each.ess and .006 Mfd. 45c each.01 Mfd. 55c each.02 Mfd. 60c each
No condensers of this kind are genuine unless theybear the trade -mark name TINYTOBB. Accept noaubstItutes.
TOBE Condensers are specified for the Infradyne, LC -27, Bernard Lamp SocketSet, Browning -Drake, Lynch Power Amplifier, Henry-Lyford Receiver, Carborundum,Alden, Somerbridge, R. B. Lab, DaUin-Haleo, Super and many other Sets, inciu dine
The De Luxe Lamp Socket Receiver
Tobe Deutschmann Co.Engineers and Manufacturers of Technical Apparatus
Cambridge, Mass.
24 RADIO WORLD January 8, 1927
The De Luxe Lamp Socket Receiver
diolight po4inv. you can have
radiol powewithout batteries
rt-1.1:431.1-t11BrBatteiyElimindt,,,
3-11 E S E radiomanufacturers.foremost in theirfield, use the RAY-THEON LONG LIFERECTIFYING TUBEin their B -powersupply units.They have acceptedRaytheon as THEHEA.RT OF RELIABLE
RADIO POWER.
`THAT the manufacturers whose namesappear on this page were quick to
standardize on the RAYTHEON LONG LIFERECTIFYING TUBE for use in their B -power supply units is a tribute to theRaytheon research organization.
The development of the Raytheon recti-fier from a mere idea to a remarkablescientific achievement has made possiblethe sale of nearly $20,000,000 worth ofB -power units, Raytheon -equipped, inthe comparatively short time since it wasfirst announced to the radio world.This means that there are already morethan 500,000 satisfied users of B-powerunits, Raytheon -equipped.
These B -power units utilize the electriccurrent which is furnished by the or-dinary domestic lighting system. Theydo away entirely with B -batteries.
lturn-FI'ee tr.,
41/1/01.1.6.`1?
The manufacturers who are listed on thispage have built B -power units to suitvarious types and styles of radio receivingsets, according to their own individualdesigns and the specifications of their ownengineers.
All of these supply units, however, havethis one thing in common-they use theRAYTHEON LONG LIFE RECTIFYINGTUBE, the perfection of which was madepossible by the development of the prin-ciple of gaseous conduction. The Ray-theon rectifier has no filaments or liquidsolutions. It has no parts to be replaced,and nothing which requires attention.
When you buy a Raytheon -equipped B-power unit you will get not only themost reliable rectifier that scientificmethods can produce, but you will alsohave absolutely reliable, unfailing B -power, improved reception, and freedomfrom the annoyance of run-down B -bat-
teries. You can dispense with B -batteriesentirely.
For your protection, the RAYTHEONLONG LIFE RECTIFYING TUBE iS Soldonly to those manufacturers whose B-power units have passed the rigid labora-tory tests of the Raytheon engineers.Look for the Raytheon Tube. It is usedby the manufacturers whose names ap-pear on this page in their B -power supplyunits. The Raytheon trade -mark is thesymbol which guarantees unfailing, re-liable radio power direct from your lightsocket.
Ask your radio dealer for a B -power unit,Raytheon -equipped. He has them-orcan get one for you.
n11-11,211 aytheon't.4. LONG LIFE RECTIFYING TUBE .11="
RAYTHEON IS THE IIEART OF RELIABLE RADIO POWER
January 8, 1927 RADIO WORLD 25
For the De LuxeLAMP SOCKET RECEIVER
Described in This Issue
Use CeCo Tubes, as Specified by
ARTHUR H. LYNCH
For the Amplifier
CeCo Type J-71OUTPUT TUBE
Operates largest loud speakersat full volume. Does NOT re-quire high voltage plate supply.At 90 V will give 12 times theundistorted power of the ordi-nary "A" type.
Price $4.50
CeCo Type GHigh Mu
For Impedance or Resist-ance Coupled Receivers
Fil. V. 5.0F II. Amp. 0.25Plate Volts. 90.180G Ives clearer reproduction with Increased volume.
Price $2.50
For the Two -Tube De Luxe Receiver
CeCo Type H CeCo BX TypeSpecial Detector
Fii. V. 5.0FII. Amu- 0.25Plate Volts. 67.90.
Improves reception especially on DXor distant stations.
Price $2.50
199 (U X base) gives Clearer Pro-duction with Increased Volume. Usedin the De Luxe Receiver as a RadioFrequency Amplifier, and chosen byMr. Lynch after Careful Tests.
RATINGFilament, volts 3.0Filament, ampere 0.25Plate, volts 20.90
Price $2.00
TRADE MARKREGISTEREDD.S.PAT.OFIR
The CeCo Tubes, types J-71, G, Hand BX, have the "X" base for pushtype sockets. These tubes, properlychosen, improve receotion on any set.
C. E. Manufacturing Co., Inc.Write for Complete Data Sheet
PROVIDENCE RHODE ISLAND
PERSONALLY PICKED BY ARTHUR H. LYNCH
$135 fo.b. New YorkWESTBROOKE
A BURLED walnut cabinet that cotnbinescorrectness and finest craftsmanship.
Borrowing an air from another period, andyet being extremely modern in feeling, itis a distinguished example of refined tasteexpressed in clea'r cut lines. Height, 57in.; width, 32 in.; depth, 15 in.Panel adjustable up to 10 by 29 inches.
You Can Have Your De LuxeReceiver In the Same Cabinet
In Your Own Home, TooTHE designer of the De Luxe Receiver has
been in radio many years; he knows values.Arthur H. Lynch dropped into the Chelten-
ham showrooms recently, and wrote out his per-sonal check for a Westbrooke cabinet. It wasfor his own home-that's what I call a real en-dorsement!
CHELTENHAM cabinets have all the author-ity and elegance required by the connoisseurwithout the exorbitant price which would be
requisite were it not for large scale production infactories which for many years have specializedon the fabrication of the finest in furniture. Allgenuine Cheltenham radio cabinets bear the fac-simile signature of J. Andrew White, dean ofannouncers, premier broadcaster of sportingevents, who for fifteen years has been a leaderas a radio dealer and manufacturer.
CHELTENHAM CABINET MAKERS, Inc.34 West 44th Street New York
Trade Inquiries Invited
FAIRFAXWALNUT panels which are beautifully
blended and grace of design set themapart from less expert attempts to attainthe perfection of balance required inauthoritative cabinets of the popular highboy type. Height, 48 in.; width, 29 in.;depth, 16 in.Panel adjustable up to 8 by 26 inches.
$102 fo.b. New York
26 RADIO WORLD January 8, 1927
How to Wire UpDeLuxe AudioAnd Eliminator
(Continued from page 23)completely eliminate any such noises.Frequently some trouble is experienced inpower supply circuits using the new BHtype Raytheon tube due to condenserfailures when the ordinary B blocks areused. For this reason the Tobe com-pany supplies a special high voltageblock, which has been thoroughly de-hydrated, for use in this amplifier. Thusthe constructor is insured against troubleand inconvenience from this source. An-other means of accomplishing the sameresult is at hand in the regular Raytheontype B tube.
The choke coils designed by Mr. Millenfor this amplifier -power unit are exceed-ingly effective. Aside from their highinductance and low DC resistance, thechokes have an unusually large air gapso that the inductance does not drop offappreciably due to core saturation evenat loads up to 80 milliamperes, at whichmaximum current the chokes are rated.The normal current in the chokes is gen-
Why is the Karas Equaraatie the MostEfficient Receiver Ever Designed?
Write us for Full Information
KARAS ELECTRIC CO.1148 Association Bldg., Chicago, IL
Sibt
220 and 221
The proof of the pudding is in eating, that'swhy S -M audios-sold on a satisfaction ormoney back guarantee, are the choice of theexperts the country over-that's why they areoutselling all other makes-that's why everyimportant magazine has recommended them.
Do you know that the largest telephonemanufacturing company has unofficially setup the S -M 220s as the finest they have evertested?-that custom set manufacturers, news-paper editors, testing laboratories, manufac-turers of phonograph records have endorsedthe S -M as the very finest?
Can you think of any better recommendationtor your audio transformers?
S -M type 220 audio transformer is designedfor all stage use in ordinary or power ampli-rfiers, with all standard tubes. S -M 221 is asoutput transformer, to be used between yourpower tube and loud speaker. It is guaranteedto improve quality and handling power un-conditionally with any set or speaker. Bothtypes are priced at $6.00.
Ask your nearest dealer for a copy of "TheSecret of Quality." It boils down in under-standable language every practical phrase ofquality amplification. It's free.
Prices 10% higher west of the Rockies.
SILVER -MARSHALL, Inc.878 West Jackson Blvd.
Chicago, U. S. A.
erally not in excess of 35 milliamperesand in many cases, such as when theamplifier is used with the De Luxe Re-ceiver, under .3C milliamperes.
By means of variable resistors (R1, R2)properly by-passed with fixed condensers,lower voltages of variable values are ob-tained for the plates of the detector andRF amplifier tubes. The detector voltageis variable so as to permit of the bestadjustment when the special detectortubes, such as the CeCo H, are employed,while the variable RF voltage controlpermits the amplifier -power unit to beused with sets possessing RF amplifiersof different types and numbers of stages.
The grid bias voltage for the last tubeis obtained by a combination of a variableresistor (R3) and a resistance -capacityfilter unit. (R9C4). The high grid volt-age required for the power tube makesit well worth while to obtain it from thelamp socket. This is in direct contrastto the grid voltage for the first two orCeCo high mu tubes, which is obtainedfrom a small flashlight battery. Thisbattery is inexpensive and will last wellover a -year. The necessary resistors andcondensers required to eliminate this bat-tery would not only cost many times asmuch as the battery but would also tendconsiderably to complicate the amplifier -power unit circuit. The grid bias volt-age on the power tube is made variablerather than fixed in order to permit theuse of the CX112 or CeCo type F tubeunder the conditions previously describedin this article.
The AssemblyThe complete unit is assembled by the
manufacturer on a substantial cast metalbase under which the greater part of thewiring is run and many of the small parts,such as buffer condensers, sockets, con-densers, resistors, and filament equalizors,are mounted.
JAYNXON TONE BRIDGENO TUBES
NO BATTERIESattached instantlyit you use aPower Tube youMUST protect
Your speaker
Your greatest RadioNeed. Order NOW.
JAYNXON LABORATORIES57 DEY STREET NEW YORK CITY
Approved by RADIO WORLD Laboratories
Math Rewarded
By U. S. Government
For Radio WorkMade Sr. Lieut. Naval Reserves For
Great Radio Advancements-FreeDetails Sent to All
Only a little over 21 years of age, but as aresult of his work, now a Senior Lieutenant inthe United States Naval Reserves-is the recordof Sterling G. Sears, called one of the foremostRadio Experts in America.
His latest development-an amazing 5 -tube Radio-with marvelous volume ,and tone quality, greatlysimplifies and improves home reception, but re-duces usual cost 60 to 75%. In addition to itsalmost unbelievable low cost, are natural reproduc--liens of tone values (music or voice) and thequick and simple ease of home installation andoperation.
For the -benefit of those interested in betterRadio reception and those who now own no Radio,but would like to have a really good one at verylittle cost-it has been arranged to supply Freeinformation and description about "The SterlingFive" to all who write Geo. W. Naylor, Jr.,Dept. 315E, 161 Chambers St., New York City.If you want to know all about it, write at once.Your inquiry will only cost you a 2c stamp andimplies absolutely no obligation.
Aside from its sturdiness the metal base,with its neat lines and black crystal -lacquer -finish, gives the entire unit amost handsome appearance. The ar-rangement of the parts on the base issuch, as to provide mechanical protectionfor the tubes and at the same time thegreatest isolation of those parts which,if placed too closely together, mightcause trouble due to coupling of straymagnetic fields. Thus, at one corner isthe transformer, while at the opposite endare the filter chokes. The fact that themanufacturer supplies the amplifier withall parts fully mounted is of great helpto the constructor as it elithinates thenecessity for such items as drills, taps,files, and muscular energy. Merely afew hours of pleasant work with a pairof wire cutting pliers, screw driver andsoldering iron, are required.
Wiring the AmplifierThe wire used should be of a well in-
sulated flexible type.First wire the power section. The two
flexible leads on the transformer are rundirectly to the two protected filamentterminals of the Raytheon socket andsoldered in place. Care must be exer-cised in soldering connections to thesockets to see that no soldering paste orflux gets between the contacts, or an arcwill result when the amplifier is put inoperation. The grid terminal of the Ray-theon socket is not used. Now connectthe two AC filament leads to the J-71tube, twisting them together.
The rest of the connections of thepower supply apparatus are perfectlystraightforward, and, after all of the ap-paratus in this unit has been connectedtogether the amplifier proper may bewired. The two leads, from each- of thegrid condensers (in the grid circuits ofthe second and last audio tubes) should be
to the grid and plate ter-minals of the proper sockets, as shown.While wiring, keep in mind the fact thatthe wires are finally to be grouped to-gether and bound into cables as men-tioned above. Ordinary grocer's string isquite satisfactory for this purpose and,if given a coat of shellac when finished,will be firmly held in place. The solder-ing lug visible on the bakelite socket stripbetween the second and third tube soc-kets, screws through the cast iron bas?and casings of the individual units, andis for the purpose of grounding the metalbase. It is connected to the negative
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January 8, 1927 RADIO WORLD 27
filament lead at the adjacent- tube nega-tive filament prong.
The negative terminal of the C batteryis the long strip. The short strip is thepositive. The positive C terminal mayeither be connected to the 'metal clampthat holds it in place or to the groundlug previously referred to. Both of thesepoints are grounded.
[This concludes the article on the Na-tional -Lynch Power Amplifier and B Sup-ply. The construction of the Two -Tube De.Luxe Receiver was described and generouslyillustrated in last week's. issue, January 1.Next week, issue of January 15, Mr. Lynchwill describe various alternate means nowavailable to the public for operating di-rectly from the lamp socket.]
Dill Asks 1,YearTrial of New It ill
WASHINGTON.Proposals and counter -proposals for
compromise between the Dill and Whiteradio bills in conference have been ex-changed between the conferees. Hoperuns high that a bill may be brought outearly this month.
The latest proposal was for a Com-mission to decide all matters of impor-tance in regard to broadcasting with en-forcement placed in the Department ofCommerce. Senator Dill proposed thisplan with a request that it be given aone-year trial. The proposal is like theWhite bill, but does not meet the Presi-dent's objection to an independent com-mission.
Senator Dill and Representative Whiteare both aware of the confusion in theair and are anxious to obtain enactmentof a regulatory measure as soon as pos-sible. If it appears as though comprom-ise will be delayed for any length of time,an emergency measure will be rushedthrough the House and Senate authoriz-ffig the Secretary of Commerce to refuselicenses to new stations.
LONG KHQ PROGRAMSPOKANE, Wash.
The 'dust to dawn' program. which wasrecently broadcast by KHQ, was a hugesuccess, according to the more than 2,000telegrams and letters received from peo-ple all over the country. Indications thatpeople in the Pacific Ocean islands werealso entertained, were given.
Hot off the press-lotost Radio Catalog and Guido for1027, brimful of now Worm, 160 pone of Bimini hook-upswith InforniatIon-all free. Shows Borings as high as50% on sots and supplies. Bo sure to got this thriftyillustrated book before you buy. It moans money in yourpocket. Standard guaranteed goods.
Write letter or postal now. Also please Includename of radio friend.
BA RAW IK CO., 550 Monroe Street. Chicago, U. S. A.
DIAMOND NAMEPLATESOUT
Our supply of nameplates for theDiamond of the Air has been ex-hausted. We can, however, con-tinue to send a booklet and blueprint for the 5 -tube Diamond of theAir on receipt of 50c, and a bookletand blue print for the 4 -tube Dia-mond of the Air on receipt of $1.00.Radio World, 145 W. 45th St.,N. Y. C.
THESE consoles, designed by Major J. Andrew White, noted sports announcer, offerhandsome housing for the De Luxe Lamp Socket receiver. They are Cheltenham mow-
" facture. Mr. Lynch bought the center one for his personal use.
Banquet Broadcast Given UpAs Listeners Await Program
WRNY, the "Radio News" station inNew York City, recently was scheduledto broadcast the entire proceedings of abanquet of the Young Men's Philanthro-pic League, in the Hotel Commodore,New York City. Many prominent actorsand actresses were supposed, to appearbefore the microphone. The crowd wasso merry it was difficult to get a properpickup. Also there was much difficultyin getting some of the stars to appearbefore the microphone, while others re-fused to appear if any mention was madeof their name. Consequently the ban-quet was not broadcast,, to the disappoint-ment of many. It is doubted, by the of -
Build a 3 ft. Cone Speakeras fine as any you can buy
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RetailPriceA3 ft.ConeSpeaker, which you can buildin one evening at home, with PENNCone Speaker Unit will give as fineTONE QUALITY at a factory -builtspeaker costing 5 times as much.
Received material and have com-pleted speaker. Sure is fine. Thankyou," writes R. Hansdn,Joliet, Ill.
"Never have heard its equal." "Havebuilt 6 and they are simply wonderful."
"Really enjoyed reception for the first time," areother comments.
Complete, detailed, easy- t a- follow instructionswill let you get same satisfactory results. It takesjust as long to build a 3 ft. speaker using a lesssatisfactory unit as it does to build one using the
PIM =RUNTwhich costs very little more. A marvel of design and.construction; adjustable to the audio output of setwith which speaker is used; so sensitive it workswith any set that will operate a loud speaker. Mag-net, pole plecee and armature are plated to preventrust, preserve magnetism; shortest, strongest driverod on any omit; full 16 oz. horse -shoe magnet; willtake all volume the tubes will pass. Unit only, $9.50.
Complete parts-including 2 sheets AlhambraFONOTEX, Back Rings, Unit Mountings, AmbroidCement and Unit-only $14.15.
Ask your dealer for the Wain,' PENN Cone Speaker Gaitand complete parts. If he cannot or mill not supply you, me millskip on receipt of price. Pamphlet, "lion to Build a 3 ft.
ono Speaker" sent for 10r, coin or stamps. Write today.
PENN RADIO SALES COMPANY104 FIFTH AVE. Suite 2193 NEW YORK CITYEselustre Selling Almelo,. G. R. PENN MPG. CO., 14. Y. C.
BLUE PRINT and Book, DIAMOND OF THEMR sent on receipt of 50c. Guaranty Radio GoodsCo., 145 West 45th Street, New York City.
ficials of this station if any further at-tempts to d3 this type of work will beattempted In the future.
Station WCCO, the Minneapolis -St.Paul station, has completely bannedbroadcasts of banquets.
Complete Parts for the
HARKNESSTwin -ChokeAudio Amplifier
This amazing new amplifier has the clearest andmost realistic tone you have ever heard. Wehave all the necessary parts in stock, includingcompletely drilled panel. All parts exactly asspecified by Kenneth Harkness. Mail your ordertoday. Send no money. just pay the postmanwhen he delivers parts. Satisfaction guaranteedor your money refunded. Complete parts include:One Drilled Panel, 7"x8%"Three KH Twinchoke Audio
CouplersOne KH Output Choke CoilThree Benjamin SocketsTwo Amperites, type 112One 2 Mfd. CondenserNine Eby Engraved PostsTwo ICA Bakelite Brackets
Cat. No.H-300
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Complete
RABCOQ. F. CHOKE
Cat No. R-24050c. each- Keeps R.F. currents out of
Three for $1.00 the audio amplifier. Es-sential to good tone qual-
ity. Use three in every set. Instructions en-closed. Order now at this money -saving price.
,RADIO BUILDERS CO.-124 Cypress Avenue Bronx, N. Y.
28 RADIO WORLD January 8, 1,927
THE RADIO TRADEU. S. Exports to Sweden
Drop Severely in a YeWhile Sweden increased its imports of
Tadio equipment in 1925, as compared'with 1924, the share of the United Statesdecreased by nearly a quarter, and thiscountry had only 7 per cent. of the Swed-ish trade in 1925. The Swedish' exports
.of radio apparatus fell off during theyear, the United States having no re -,corded share in this trade.
Trade advices from Samuel G. Ebling,discussing the subject, have been madepublic by the Department of Commerce.The full text of the report follows:
Imports of radio apparatus into Swe-.den during 1925 increased in value by1,464,581 crowns over that for 1924. The1925 value of Swedish exports of thisequipment decreased by 251,872 crowns,or over 39 per cent, as compared with1924.
Purchases from Germany constituted
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IFERBEND"B' ELIMINATORComplete. Operates direct from socket on110-120 volt A. C. lighting circuit. Deliversup to 103 volts. Second successful year.Amazingly low in price-high in value.Equal or superior to any "B" Eliminator,regardless of price. The FERBEND "B"Eliminator is approved and passed by therigid laboratory tests of Radio News andPopular Radio.
Ask Your Dealer-or Send DirectShipment made direct on receipt of price, orC. 0. D. if preferred. Use for 10 days toconvince yourself-if unsatisfactory write uswithin that time and purchase price will berefunded. Write for Literature.
FERBEND ELECTRIC CO.424 W. Superior St. Chicago, IIL
about 55 per cent of the total importsand the value of German goods receivedduring 1925 was more than double thatof 1924. Great Britain, which suppliedover 13 per cent of the total, increasedits sales by a little over 9 per cent.
Imports from The Netherlands, whichfurnished 9 per cent, increased in valuefrom 90,891 crowns in 1924 to 393,504crowns in 1925. The United States sup-plied 7 per cent, decreasing the value ofits shipments approximately 23 per centas compared with 1924.
France and Denmark furnished about5 per cent each, imports from the formercountry declining by 22,492 crowns, whilethose from Denmark increased by 38,492crowns. Norway, whose export of thisequipment to Sweden in 1924 totaled 226,-125 crowns, declined to only 125,029crowns in 1925.
About 20 per cent of the Swedish ex-port of radio equipment went to Norway,which received goods valued at 88,055crowns, as compared with 43,072 crownsduring 1924. Finland purchased 14 percent, Denmark 11 per cent, Brazil 8 percent, Germany 7 per cent, Italy 6 percent, France and Spain about 4 per centeach, and Great Britain, Japan, and Po
FINE RADIO CABINETSWE BUILD THEM
Complete lines built of hardwood gee ply built noatook solid walnut and genuine mahogany. Sim 7z1 Sz10 to 7430010. Priced from $3.25 to $12.00 Wespecialize on odd sizes, send sketch or blue prints forestimates on single or In quantities, write for catalogue.HICKORY TABLE AND NOVELTY CO.Hickory, North Carolina.
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land about 3 per cent each of the totalSwedish export value of radio apparatusduring 1925. Mexico and China receivedequipment valued at 27,547 crowns and53,547 crowns, respectively, in 1924 butpurchased done from Sweden, in 1925.
The greatest decline in Swedish radioexports in 1925 was in those to Switzer-land which fell off nearly 225,000 crowns,as compared with the previous year.Shipments to Spain decreased over 50,000crowns, and to Russia over 33,000 crowns.Sales to Germany declined almost 60 percent, while those to Denmark almostdoubled in value, and those to Brazil al-most trebled in value.
Six -Tube Factory SetMeasures 8 x 10 x 7 Inches
SPOKANE Wash.Manufacture of the Spokane Six Sym-
phony six -tube radio set, the smallestthat uses this number of tubes, is forgingrapidly ahead in the workrooms of theInterstate Radio Company, Spokane,Wash. The receiver, a one -dial affair,is 8 inches deep from front to rear, 10inches wide and 7 inches high.
D. J. Ives, Spokane, formerly with aradio factory in the south, is the designerof this set, which embodies a new type ofdesign for coil mounting.
TRADE NOTESGREENBERG, Pa.
Warren H. Walker, of Walker Radiorecently announced the opening of abranch store at 24 West Otterman St.,formerly occupied by the Harris Clothingstore.
A complete line of radios and access-ories as well as electrical supplies will behandled.,
*. * *
BELLEFONTAINE, O.Blair Brothers recently opened up a
radio store in this city, in the wall paperstore of Fred Neff, east Chillicothe Ave-nue. They have taken the agency forthe Metrodyne, a nationally known set.
TYPOGRAPHICAL ERRORIn the January 1st issue of RADIO
WORLD the type UX Universal Airgapsocket was quoted at 50 cents, while theprice is 60 cents, the same as the AirgapProducts Co. type UV Standard.
The address of the Airgap Products Co.is 10 Campbell St., Newark, N. J.
NAME CHANGED. S. Radio Carpi:Ration, Seattle, Wash., capital
stock $2,000, name changed to Robert Denny &Co., Inc.
World RadioStorage "B" Battery
12 Cell -24 VoltProved value. Thousands of users find reception almostmagical. Clear. true power-instantly Rubbero. ing IY . Wiseeconomy. Sturdy construction-Sohd Ease protec-tion. Recharged for almost nothing. Endorsed and listed asstandard by famous Radio institutions including Pop. RadioLaboratories, Pop. Set. Inst. Standards, Radio News Lab.,Lefax, Inc., and other Radio authorities. What more needbe said? Extra Offer: 4 Batteries in series (96 volts) $10.60.Send No Money L'I't:tg;Trdt?":"Attn.d 7,' VIOL'C. O. D. Pay expromman after exang batteries.discounttor cEsh with order. Remember-you save 50% on World Batteriee.
WQ3ailUtWiiVt6S1 '1219 So. Wabash Ave. Dept. 82 Chicago, III.Mob,,-, o/lho Rumour World Radio A Steer Botta,Prices: 6-oolt, Amu. 713.00.
e% set your radio dials at 288.3 meters for theWorld Storage Bat. 0City and State
January 8, 1927 RADIO WORLD 29
Trade and StationsMust Act as One,Dr.GoldsmithSays
According to Dr. Alfred N. Goldsmith,chief broadcasting engineer of the RadioCorporation of America, who recentlyspoke at a luncheon of the Radio Manu-facturers' Aisociation, at the Hotel Com-modore, New York City, broadcastingstations and manufacturers of radio re-ceivers must each play a part, in orderthat the public be satisfied with radio.
"The broadcasting stations must pro-duce programs that are diversified andinteresting," he said.
"No one wants to listen to a specifictype of program. Tastes differ, and whatis suitable for one is unsuitable for an-other.
"We are on the verge of a new era inbroadcasting when stations put 'chain'programs on the air. I hope that therewill be many such. programs in place ofthe features from individual stations.There is plenty of room for a few morereal good broadcasting 'chains.'
"The manufacturers must keep in mindthat there are certain qualifications thepublic wants when it comes to receivingsets. First, the designs must be simpli-fied. Reliability is another asset thepublic demands.
"If the broadcasters and manufacturerskeep these things in mind, there is noreason why the radio industry should notbe one of the greatest indutries in theUnited States."
18,000 SETS IN ERIE, PA.ERIE, Pa.
There are 18,000 radio sets in the homesof Erie, according to Frank Gannah ofthe Electric Supply and Equipment com-pany which handles Kolsters and Erlas.Mr. Gannah gets his estimates from otherradio dealers and from the Radio DealersAssociation which was recently organizedhere.
mASTERPIEcEAT SitRITIOINIZIZTI
FRESHMAN DEALERS Y
LiteratureWanted
THE names of readers of RADIO WORLDwhir desire literature from radio job-
ber. and dealers are published in RADIOWORLD on request of the render. Theblank below may be used, or a post cardor letter will do instead.RADIO WORLD,145 West 45th St., N. Y. City.
I desire to receive radio literature
Name
Address
City or town
State
Lester Martin, 2,4 Keeney Lane, New LondonConn.
J. E. Hein, 813 Bergline Ave., Union City, N. JJohn E. dummerson, 824 South 16th St., Lin -
cola, Neb.John E. Romer, 707 North Colonial Ave., Rich-
mond, Va.William Richards, 10 Sherman Ave., East
Port Chester,' Conn.Joseph F. Kitchen, 3310 Hibbing Ave., Minn.L. E. Koehmstedt, Overly, N. D.0. C. Williams, P. 0. Box 86, Greer, S. C.Theodore J. Lowery, 667 Glenwood Ave.,
Owosso, Mich.Harry Stewart, 143 Fairview AVe., Jamestown,
N. Y.R. W. Deck, 406 Center St., Sandusky, 0.I. Stein, 18 Baldwin Ave., Newark, N. J.G. W. Craig, 444 Delaware St., Gary, Ltd.E. Bauer, Box 101 Hobart, Ind.Joseph Pagano, 28 Erie St., Clifton, N. J.Clifford Sewr Seward, 1426 King Ave., Indian
apolis, Ind.Thomas 11. Adams, 37 Pleasant St., Bristol,
Corm.C. C. Noel, Boa., Ala.Harry Persson, 1516 Eastford Road, South-
bridge, Mass.Gunnar Peterson, 193 Eastford Road, South-
bridge, Mass.A. G. Beech,'428 Greenwich, Belvidere, N. J.
ARTER
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"Midget" Rheostatwith Filament SwitchSay "good-bye" to trou-ble when you install thisCarter part. Leave twoinstruments behind andreplace them with one.It will be well worth yourwhile. Furnished in allresistances.Any dealer can supply.In Crinadai
Carter Radio Co., Ltd., Toronto
ARTS] RADIO CO,CHICAGO .D,ZAT
Rochester TradesRe,elects I" cullers,Sharer The Head
Rochester, N. Y.The election of ' officers at the annual
meeting of the Rochester Radio Trades,Inc., resulted in the reelection of Presi-dent Thomas B. Sharer and all otherofficers, including Vice -President CharlesL. Horman, Treasurer William C. Lud-wig and Secretary Ray M. Smith.
Leon Goldsmith, William C. Ludwig,H. C. Johnson and Robert Harmon wereelected directors of the organization fora period of one year to co-operate withthe other seven directors.
Rochester Radio Trades, Inc., was or-ganized on January 25, 1926, with onlysix members. Today it has fifty-one.The ,purpose of the organization is topromote broadcasting, better merchan-dising and fair dealing in the radiobusiness in and about Rochester. Thespirit of the membership is said to beunsurpassed any organization of anynature in the city, all members co-oper-ating for the best interests of the tradein general.
Executive offices are maintained at No.122 Cutler Building. Radio dealers wish-ing to become associated with the or-ganization are invited to call.
NAAIpUX POWER TUBES lastalled In taw setwithout rewiring by Na-Ald Adapters andCesaascteralds. F er tun Information writsAlden Manufacturing Cu., Dept. 5-11.niwittirfield. Mass.
SHORETRANSFORMERS A N DCHOKES. FOR EVERYRADIO POWER NEED
Special Transformers Made to OrderWrite for Prices-Also See
Dec. 4 Issue
SHORE ELECTRIC CO., Inc.129 Cypress Avenue, New York City
B S T 5 $40.00
IMMEDIATEDELIVERY
DIRECT FROM FACTORY TO YOUSAVES HALF AND IS GUARANTEED
I take great pleasure in telling you that my B.S.T. 5 -tube setis working splendid in every way, and the cabinet itself isbeautiful, and admired by all my friends.
THOMAS HARTLE,155 Perry St., Paterson, N. J.
This highly sensitive, powerful and selective BST -5 radio re-ceiver has all up-to-the-minute improvements. Heavy alum-inum automobile type chassis, shielded against stray currentsand distortion. Flexible grip, Universal type sockets, elimin-ating microphonic noises. Has provision for battery eliminatorand any power tube. Fahnestock clips on sub -panel for ad-justing C battery, has voltages for power tube. Efficient oneither long or short aerial, including indoor aerial. This BST -5sets a new standard for true tone values and selectivity. ThisBST -5 gives greater volume than many six -tube sets andconsumes less current.
Shipment made same day we receive your cheque orP. 0. Money Order for $40.
New model cabinet Du Pont Duco finish; base 21" long by 8"wide, height 9,A", top 21" by 6". Five-ply walnut veneer
RADIO WORLD Guarantees the Responsibility ofThis Advertiser
GUARANTY RADIO GOODS CO. 145 West 45th St., New York
30 RADIO WORLD January 8, 1927
Television NeedsPhysical Motion
(Its last week's issue, Jan. 1, Dr. E. F. W.Alexanderson discussed the operation ofthe television apparatus, also how thepresent system was evolved. How the lightbeams are intercepted by a rapidly revolvingdrum, and interlaced so that recognizableobjects can be seen, is herewith told.)
There is another advantage in the useof the multiple light beam. Each lightbeam needs to move only one -seventh asfast and therefore needs to give only 43,-000 instead of 300,000 independent im-pressions per second. A modulation speedof 43,000 per second is high with ourpresent radio practice but yet withinreason, being only ten times as high aswe use in broadcasting.
The significance of the use of multiple
"Audio Amplification"A Book-Contains Valuable Suggestions forImproving Tone Quality.
SAMSON ELECTRIC CO.CANTON, MASS.
Radio Mailing Lists27428-Rad lo Dealers, Retail, Per M $7.602660-Rad lo Mfrs., Per List 20.002857-Rad lo Jobbers, Per List 22.601847-Radio Jobbers rated $5,000 and
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10.00and any other Radio List you want. Askfor detailed price lists ail guaranteed Hi%correct.
Trade Circular Co., Inc.116 W. Adams Street Chicago
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SEND FOR PAMPHLETS OF THE GOOD-MAN TUNER-In use for years and still good.Tested and approved by many technical labor.atones. L. W. Goodman, Drexel Hill, Penna.
PATENTS-Write for free Guide Books and"Record of Invention Blank" before disclosinginventions. Send model or sketch of your invention for our Inspection and Instructions Free.Terms reasonable. Radio, Chemical, MechanicalElectrical and Trademark experts. Victor J.Evans Co., 924 Ninth, Washington, D. C.
light beams may be explained from an-other point of view.
It is easy enough to design a televisionsystem with something like 40,000 pictureunits per second, but the images so ob-tained are so crude that they would havevery little practical value. Our work onradio photography has shown us that anoperating speed of 300,000 picture units persecond will be needed to give pleasingresults in television. This speeding up ofthe process is unfortunately one of thosecases when the difficulties increase by thesquare of the speed. At the root of thisdifficulty is the fact that we have to de-pend upon moving mechanical parts.
If we know of any way of sweeping aray of light back and forth without theuse of mechanical motion, the answermight be different. Perhaps some suchway will be discovered, but we are notwilling to wait for a discovery that maynever come. A cathode ray can be de-flected by purely electromagnetic means,and the use of the cathode ray oscillo-graph for television has been suggested.If, however, we confine our attention tothe problem- as first stated, of projectinga picture on a fair sized screen, we knowof no way except by the use of mechanicalmotion.
If we also insist upon a good image wefind that we must speed up the process7 times and in doing so we must reducethe dimensions so that we will have onlyone forty-ninth as much light. Our solu-tion to this difficulty is, not to attempt tospeed up the mechanical process but topaint seven crude pictures simultaneouslyon the screen and interlace them optically
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so that the combination effect is that of agood picture.
Tests have been made with this modeltelevision projector to demonstrate themethod of scanning the screen with sevenbeams of light working in parallel simul-taneously. A moving picture showing theapparatus and procedure during thesetests will be presented. The seven spotsof light may be seen on the screen as acluster. When the drum is revolved theselight spots trace seven lines on the screensimulatneously, and then pass over anotheradjacent track of seven lines until thewhole screen is covered. A completetelevision system requires an independentcontrol of the seven light spots. For thispurpose seven photoelectric cells are lo-cated in a cluster at the transmittingmachine and control a multiplex radiosystem with seven channels. A Hammondmultiplex system may be used with sevenintermediate carrier waves which arescrambled and sent out by a single trans-mitter and then unscrambled at the re-ceiving station so that each controls oneof the seven light beams.
The first part of the moving pictureshows the television projector in operationmoving faster and faster until the wholescreen is covered with a sheet of light.The second part shows a moving picturefilm transmitted by telephotography at arate of seven seconds for each picture.The same rate of speed with seven lightbeams would give one picture per second.Thus we see that in order to get televisionwe must speed up the process sixteentimes. However, this is not unreason-able because this film was made with acarrier frequency of only 3000 cycles.
Seven television carrier waves may thusbe spaced 100 kilocycles apart and a com-plete television wave band should be 700kilocycles wide. Such a radio channelmight occupy .the waves between 20 and21 meters. If such use of this wave bandwill enable us to see across the ocean Ithink all will agree that this space in theether is assigned for a good and worthypurpose.
D X POLE ANTENNAA PROVEN PRODUCT
Can be put up most anywhere. This DX ANTENNA has twicethe antenna Input of any other type-delivers same volume onone-half the current normally used. Saves half the batterycurrent. Is 100% self -directional. Separates stations more easily.Simply installed, rugged construction, takes practically no room.
DX Antenna Kit Complete, $13.50 PailWest of Rockies, $14.00 Canada, $14.50
Dealers, Jobbers, Agents Write for Trade TermsManufactured by the
DX LABORATORIES39 Soper Ave., Oceanside, Rockville Center, N. Y.
Tested and Approved by Radio World Laboratories
SPECIAL PREMIUM SUBSCRIPTION OFFERFor NEW RADIO WORLD Subscribers Ordering NOW
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DEALER or-POPULAR RADIO or -RADIO (San Francisco) or-SCIENCE AND INVENTION or -RADIO AGE.
This is the way to-for the price of one:-Send WIN today for RADIO WORLD-far one year (regular price-for 52 numbers)-and select any one of the other-nine publications for twelve months.
get two publications-Add 81.00 s year extra fee-Canadian or Foreign Postage.-Present RADIO WORLD subscribers-can take advantage of this offer by-extending subscriptions one year-II they send renewal. NOW!
RADIO WORLD'S SPECIAL TWO -FOR -PRICE -OF -ONE SUBSCRIPTION BLANKRADIO WORLD, 145 West 45th Street, New York City.Enclosed End $6.00 for which send me RADIO WORLD for twelve months (52 numbers, beginningand also without additional cost, Popular Radio, or Radio, News, or Science and Invention, or Radio Dealer, or Radio (San Francisco), or Radio Age,or Boys' Life (or $10.00 for two yearly subscriptions). (No other premium with this offer.)
Indicate if renewal.Offer Good UntilJanuary 29, 1927.
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January 8, 1927 RADIO WORLD 31
HOW TO WIND THE COILS FOR THE EFFICIENCY SUPER -HETERODYNE(Concluded frown page 9)
The set is arranged for either antennaor loop operation. A double pole doublethrow switch is provided for quicklychanging from one method to the other.This switch should be of the low capacitytype as indicated in the drawing, or asuitable switch jack that performs thesame purpose.
The antenna coil LI may consist ofabout ten turns of No. 22 double cottoncovered wire on a diameter of 3" andthe secondary may be wound on the sameform with the same kind of wire. Thesecondary should contain about 45 turnsprovided the tuning condenser Cl has amaximum value of .0005 otfd.
There is a. second rheostat R5 in the
filament circuits of all the tubes, and itis a master rheostat. Its only object isto adjust the filament current to normal,not to control volume, hence should bebaseboard mounted. It should be able tocarry safely without heating a current of154 amperes (as most rheostats do) andit may have a maximum resistance fromone to six ohms.
S is a filament switch for turning onand off the receiver.
The filament battery voltage shouldbe that furnished by a six -volt storagebattery. The voltage on the detectorplates should be 45 volts and that on theamplifiers and the oscillator should befrom 45 to 67% volts.
If desired an audio frequency amplifier
may be added to the circuit. This shouldbe one capable of retaining the goodquality which the circuit has up to thedetector terminals. Only a leak of about1 meg. is necessary in the first audiogrid circuit to complete the first AF stagecoupling. Add to that two stages ofresistance coupled AF or of impedanceor double impedance coupling for speakeroperation. If only moderate speakervolume is desired, simply acid to the firstimpedance stage one step of transformercoupled audio.
VOLT NAMED FOR VOLTAThe term volt comes from the name of
Volta, an early Italian investigator ingalvanic electricity.
4, 5KIT
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221 Fulton St., New York City
DEMAND frf...9114(DS_fee Fixed Condensers end Resistances. Approvedby M. I. T. and Yale. Used as standard equipmentby over 200 manufaeturers of Radio Receivers and"B" Eliminators.
AEROVOX WIRELESS CORP.489-491-490 Broome St. Nev York
ANY SET DESCRIBED IN
RADIO WORLDBUILT TO YOUR ORDER. WRITE
M. LERNER1498 Remsen Ave. Brooklyn, N. Y.
How to Build
THE DIAMONDFIVE TUBE MODEL
Herman Bernard, designer of this wonder cir-cuit, has written cn illustrated booklet os"How to Build Remo Womm's Improved Dia-mond of. the Air." Send SOc and get thisbooklet, including a full -sired wiring blueprintSend $6 for year's subscription and get book-let. and blueprint FREE.[Newsdealers or radio dealers, order the book-
lets with blueprints included, in quantity, directfrom American News CQ. or branches.]
RADIO WORLD145 WEST 45th ST. NEW YORK CITY
4 - TUBE DIAMONDBLUEPRINT
The Entire WiringShown in SimplifiedPicture Diagram Form
$1.00Copy of Nov. 20 issue, containing HermanBernard's article on how to build the set,15 cents extra.
Send money order, check or stamps.None sent C. 0. D.
All orders filled promptly.
RADIO WORLD145 West 45th St., New York City
HOW TO BUILD THE BERNARD, the beau-tiful 6 -tube thumb -tuning set, fully described sadillustrated in the Oct. 16 issue. Send 15c for copy. Namepieces for affixing to front panel freeto all on special request. Radio World, 145 W. 45thSt., N. Y. City.
The BRETWOODVariable Grid Leak
Is a Remedy for Distortion
Precision Range, to 10 Megohms
Much of the distortion present in radio receivers is dueto an overloaded detector tube. Too much power for thatlone tube to handle with fidelity. The Bretwood VariableGrid Leak permits control of the grid circuit so that themaximum efficiency without distortion is achieved. Puta Bretwood Variable Grid Leak in your set and marvel atthe difference!
"THE RESULTS ARE ASTONISHING"NORTH AMERICAN BRETWOOD CO. Dec. 26.Dear Sirs:
I feel as it is my duty to write and tell you that I bought a Bretwood grid leak andgot fine results. I placed it in the same position as a regular fixed grid leak.
THE RESULTS WERE ASTONISHING. I was quite a while adjusting it to its properposition. It means true tone, clarity, volume and many more DX receptions.
I have tried many other makes of all kinds and sizes, but THIS ONE IS THE BESTYET.
Most people will write credentials praising results from instruments they have tried onsets that anything at all would improve, but my set, I thought, could not be improved on.I was dumbfounded, for now I know I own a perfect set.
You may use this letter for advertising, also name and address for references ofany kind.
From a well -satisfied user of a Bretwood Grid leak.(Signed) GEORGE SORTWELL,
18 Dug. House, 1915 W. Wash. St., Indianapolis, Ind.- - - - - - - - - - - -NORTH AMERICAN BRETWOOD CO.,
143 West 45th Street, N. Y. CityEnclosed find $1.50, for which send me one Bretwood Variable Grid Leak
(or $2.00 for leak with grid condenser attached) on five-day money -backguarantee.
NAME
STREET ADDRESS
CITY and STATE(Inquiries Invited from the Trade)
RADIO WORLD'*-7)4,t7
January 8, 1927
IS MONTHS Cr iptii3uVA=8" U C U
'
StNO OTHEIR, BATTERY IS LIKE IT
The Layerbiltpatented con-struction re-vealed. Eachlayer is an elec-trical cell, mak-ing automaticcontact with itsneighbors, andfilling all avail-able space insidethe battery case.
Everette!), Layerbilt"B" Battery No.486, the Heavy -Duty battery that should bespecified for all loud -speakersets.
Practical tests have shown this to bethe most economical of13"BatteriesIN DAILY use in the home, EvereadyLayerbilt "B" Battery No. 486 hasfulfilled the promises made for it inlaboratory tests. More than a year'sstudy of the performance of this bat-tery in the hands of the public hasshown that it is the most satisfactoryand most economical "B" battery everdeveloped. All loud -speaker sets re-quire Heavy -Duty batteries-and theLayerbilt has proved itself absolutelythe best of them all.
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Those are the convincing reasons why
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Just remember this about "B" bat-teries-Heavy-Duty batteries are moreeconomical than the smaller Light -Duty batteries on all loud -speaker sets,and the patented exclusive EvereadyLayerbilt No. 486 is the most economi-cal of all.
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