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Number 10 *Tebruary 1948Microwave Relay * FM Transmitter Assembly Line

td,7/;),/,-.- -and you'llcome back for more!

It's justthis size!

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Brilliant performance is possible with an 8 -inchspeaker. Prove it to yourself by putting the 755-Athrough its paces. We'll bet you'll be so pleasedyou'll cone back for more!

Call Graybar today!Get your 755 -A's quickly-call your nearest Gray -bar representative right now-or write to GraybarElectric Co., 420 Lexington Ave.,New York17,N.Y.

Specifications of the 755-4Power Handling Capacity

8 watts continuousFrequency Response

70 to 13,000 cyclesInput Impedance

4 ohmsEfficiency

Sound level at 30 feet onaxis is 81.5db above 10-16walls per square centi-meter at 8 walls input

Coverage Angle70 degrees

Weightt3/4 pounds

DimensionsDiameter: 8%"Depth: Ws"Baffle Hole Diameter 7"

Enclosure Required2 cubic feet

010.0

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OSCILLATOR\./V \AA/VV

FEBRUARY 1948

A QUARTERLY PUBLICATION DEVOTED TODEVELOPMENTS IN COMMUNICATIONSAND ELECTRONICS AND PUBLISHED BY

Western Electric Company195 Broadway New York, N. Y.

S. BRACKEN . President

F. R. LACK Vice President

N. R. FRAME Secretary

H. H. REDDALL Treasurer

WILL WHITMORE, EditorVANCE HILLIARD, Managing Editor

GEORGE de MARE . . . Assistant Editor

R. S. LANIER Assistant Editor

The Oscillator does not accept responsibilityfor quoted statements appearing in the mag-azine. Such statements reflect only the opinionsof the person quoted.

Copyright, 1948by Western Electric Company, Incorporated

Printed in U.S.A.

THE COVER

FM transmitters in the making-the Koda-chrome on our cover, taken in the Burlington,N. C. plant, shows the assembly line for thefinal amplifier units of Western Electric's 10kw FM transmitters, with the similar line

for the rectifier units visible in back of it.

The units at the right end of each line arecompletely assembled and ready to go toinspection. On pages 22 and 23 are addi-tional pictures showing inspection and testingof the completed units.

THIS ISSUE

Microwaves in Harness 3

WTPS-FM, New Orleans 8

Standardized Quartz Crystal Units 12

Two Western Electric FM Tens Go on theAir in New York 14

Power Amplifiers for the ModernAM Transmitter 16

A New Ventilating System Adds Reliabil-ity to FM Transmitters 18

This is the Life 20

Production Line for FM Transmitters 22

WSB-A Dixie Institution 24

Custom Builders for Broadcasting . 28

FM'ing Around the Clock 31

New Order Wire Panel for Broadcasters 32

"Protected Networks"-A New Techniquein Hearing Aids 34

Complete Index for Issues Number 1.10 40

Contributors to this Issue 43

Distributors of Western Electric commercial

products: In the United States - GraybarElectric Company, 420 Lexington Avenue,

New York 17, N. Y. In Canada and New-foundland -Northern Electric Company, 1620Notre Dame Street W., Montreal, Quebec.

When you read this, a new year will be weeks old.

A new year that will carry us closer to a world of peace or

one that will shove us a little farther away from it.

We who make the coils and wires, the tubes, resistors

and condensers which make up radio broadcast transmit-

ters know that these are just inanimate parts which have

no heart, no soul, no love for man, but we also know that

when they are assembled and activated with current and

the words of man, they come to life. Inanimate themselves

but possessed of the marvel that is radio, they transmit to

the far ends of the earth the ideas, the dreams, aspirations,

fears, visions and hopes of a world.

For all of us who are part of this thing called BROAD-

CASTING, let us remember that man cannot live for long in

fear and despair. Let us realize the power, the force of our

medium. Let us use it wisely and well. Let us use it so that

someday fear and despair will be banished, and man

everywhere can again hold his head high in peace, free-

dom and tranquillity.

W. W.

2 Wooer?, Eleclric DV71:1417,031

MICROWAVES

IN HARNESS

V

System characteristics

and microwave techniques

in the newly opened

broadband relay which

carries video -width signals

between New York and Boston

CENTIMETER -BAND vacuum tubes, highlydirectional antennas, cavity elements

for tuning, crystal mixers and other tech-niques that are new-born from the vastprewar and wartime development in thehandling of microwaves are being giventheir first large-scale tryout in a draft -horsecommunications role in the recently openedNew York -to -Boston relay system. Thisbroadband radio relay link between the twocities, which opened for experimental oper-ation as a facility of the Bell System lastNovember 13, is expected to determinemany of the technical and economic per-formance characteristics of microwavecommunications systems which employ re-peaters at line -of -sight spacing to coverconsiderable distances.

The final service role of this radio relaylink, and of similar relay systems overother routes which are being developed,

is not expected to be determined for sometime, but its potentialities are of great sig-nificance to television and broadcasting ingeneral.

A trend in public service communica-tions practice has been toward use of everwider frequency bands to accommodatelarge numbers of telephone messages andother types of communications on a singlecarrier channel, through multiplexingmethods. In the case of the coaxial cable,these wideband transmission capabilitiesare utilized alternatively for transmissionof television signals. The intelligencehandling capabilities of microwave radiorelay systems can be used in much the sameway, and thus such relay systems could con-ceivably play a many-sided role in televi-sion, AM and FM broadcasting, telephone,and other services.

The New York -to -Boston system was

developed by Bell Telephone Laboratoriesand combines to a major degree the con-siderable experience of the Laboratories inmicrowaves, with their thorough knowl-edge of the performance characteristics re-quired of a public communications system.

The system operates at frequencies near4,000 megacycles, and provides facilitieswith a bandwidth of about 4.5 mc. Asinstalled, it provides two 4.5 mc channelsin each direction. Between New York andBoston seven repeaters are used, withhighly directional antennas to concentratethe signal in a narrow beam from one re-peater to the next. The repeaters are de-signed for unattended operation. Thetransmitting and receiving equipment atthe New York and Boston terminals is de-signed to accept television signals, or anysignal with a bandwidth not exceeding 4.5megacycles, such as the multiplexed tele-

February 1948 3

President Walter S. Gifford of A.T.&T. opens the microwave relay with first call, New York to Bos.

ton. Left, Frank P. Lawrence, Vice Pres., A.T.&T.; right, Carl Whitmore, Pres., N. Y. Telephone Co.

phone signals already referred to. Moni-toring facilities for both television andmultiplexed signals are built into the ter-minal equipment, as well as means for test-ing the essential characteristics of the sys-tem such as distortion and gain. Thus thesystem as a whole represents a markedadvance in the solving not only of the diffi-cult amplification, frequency stability, andother design problems of the microwavespectrum, but also problems of reliability,system monitoring, testing, and economicsof operation.

Effect of Rain on Signal StudiedIn choosing the characteristics of the

New York -to -Boston system, Bell Labora-tories had the benefit of a series of testson microwave systems, carried out in theNew York -Northern New Jersey area,which were started before the war andcontinued as soon as a return to peace-time conditions permitted. In these teststhe depth of fading at various frequenciesand over various path lengths was investi-gated, as a part of the work of determiningthe requirements for various elements ofthe proposed system. It was found that thedepth of fading increases with path length,and that both depth of fading and attenua-tion caused by rainfall increase as the fre-quency is raised toward 10,000 megacycles.Thus, while the higher frequencies are

advantageous in making possible highlydirectional antennas of moderate size, thefading and attenuation characteristics ledto the choice of 4,000 megacycles as apractical carrier frequency, with repeaterspacing limited to a maximum of 35 miles.

As can be seen on the map on page6, the actual repeater spacings rangefrom 11 to 35 miles. The average is 27.5miles. Naturally in choosing sites for therepeaters, accessibility, availability, andnearness to other facilities had to beweighed in addition to the fundamentalaim of obtaining a line -of -sight path to theadjoining locations. Choice of the sitesthus involved study of topographic maps,surveys of probable sites, and actual checkof individual paths with microwave testequipment, to guard against map inac-curacies.

The operation of the repeaters can bedescribed with the aid of the first block dia-gram in Figure 1 on page 7. One receivingand one transmitting antenna are used forthe two channels in each direction, or a totalof four antennas at each repeater station.The diagram referred to shows the equip-ment for two of the four channels of arepeater station. The antennas are of themetal lens type which has been describedin the Oscillator, April, 1946. These per-mit the focussing of the microwave energyinto a narrow beam between repeaters.

Energy is fed to the antennas and takenfrom them through a metal horn and waveguide system.

Carrier FrequenciesThe carrier frequencies used are spaced

at small intervals in the neighborhood of4,000 megacycles, as shown in Figure 1,to avoid interaction between the two chan-nels using each antenna. At the next re-peater station the frequency transforma-tions would be from the outgoing frequen-cies shown, back to the incoming frequen-cies shown. This staggering of frequenciesavoids bringing a high level and low levelsignal of the same frequency together atany repeater station. Thus four frequen-cies are actually sufficient for the en-tire two -channel, two-way system.

Vacuum tubes now available for wide -band amplification in the vicinity of 4,000megacycles are not developed to the pointwhere the internal tube noise energy is lowenough for use in low-level stages, whenthe amplification process is to be repeated

Two bays, each holding complete equipment for onechannel, are mounted together at repeater station.

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a number of times. Therefore, in the re-peaters the major part of the gain and theavc action are obtained in i-f amplifiersoperating at 65 megacycles.

The frequency conversions can be stud-ied by following a signal through fromreceiving to transmitting antenna. Refer-ence to Figure 1 shows that a carrier signalat, say, 3930 mc, is carried from the an-tenna in a waveguide along with the secondchannel signal which is at 4130 mc. Thetwo are separated in the branching filtershown in the photograph on page 6. The3930 mc signal is mixed with an oscillatorfrequency of 3865 mc in a silicon varistormodulator to produce the 65 mc i-f fre-quency. The signal then acquires the mainrepeater gain in a preamplifier and mainamplifier at 65 mc, which contain the avcsystem that maintains constant output fromthe repeater.

A second silicon varistor modulatorthen converts the signal back to the micro-wave range, to the 3970 mc outgoing fre-quency, by mixing the i-f with a local

Rear of repeater bays shows branching filters attop and at waist level, cooling blowers at bottom.

oscillator frequency at 3905 mc. Themicrowave amplifier that follows raisesthe power level to the 1 watt at which thesignal is sent to the antenna for beamingto the next repeater.

The gain of each complete repeater isautomatically variable over the range55-80 db, a design figure based on thefinding that the probable maximum depthof fading under the conditions establishedfor the new microwave relay link is about25 db, with a figure of 55 db as the mini-mum gain at each repeater that would berequired in the absence of fading.

The frequency stability of the localoscillator and of the microwave amplifieris maintained in a number of ways. In eachchannel the two local oscillator frequencieswith 40 mc spacing are produced with ahighly stabilized microwave oscillator, anda 40 megacycle crystal -controlled oscillator.Techniques have been developed to reducethe variation of frequency in these twooscillators to the low figure of .005%.A typical crystal oscillator is shown in the

Terminal equipment includes two bays, at left, withIn three bays at right are the FM transmitters and

photograph on page 6, with the front paneland the front of the temperature -controlledenclosure both removed.

A study of Figure 1 will show that theconversion system minimizes signal fre-quency variation in another way. As thesame microwave oscillator supplies the fre-quency for both the "down" and the "up"conversions, any slight shift in frequencyof the microwave oscillator will affect onlythe i-f frequency, since the error cancelsitself in the two conversions. The micro-wave oscillator has automatic temperaturecontrol.

The photograph on page 3 showsthe microwave amplifier unit with frontcover removed. The output cavity is beingadjusted with the threaded stud that actsas a frequency -setting element. The fourvacuum tubes used in the amplifier can beseen, with two additional tubes used asbuffer amplifiers below them, and belowthat the panel containing the modulator.

The anode end of each tube extendsinto an air cooling duct which is supplied

units duplicating those in the repeater channels.receivers and video and monitoring equipment.

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Rear of stabilized oscillator,showing crystals in cavities.

with air by a blower at the base of thebay. Two complete repeater bays areshown in the two views, front and rear, inthe photographs on pages 4 and 5. Thefront view shows a meter panel being read,just above which is the microwave oscil-lator, and below which is the microwaveamplifier with cover in place. The rear viewof the dual unit shows the wave guides withthe branching filters - the receiving filtersat the top, the transmitting filters closer tothe floor level, and the blowers at the base.

The very exacting design requirementsof a relay system using broadband micro-waves, which is to be adaptable to multi-channel telephony and television signals aswell as other services, can be judged fromthe repeater characteristics shown in Figure1. The most important characteristics arethe amplitude -vs -frequency response andthe amount of delay distortion. The latter,even in very small amounts, may becomeperceptible in television transmission, andmay produce serious crosstalk in multi-channel telephony. The curves in Figure 1show that the repeater is uniform within±0.1 db over the 10 megacycle signalband, with delay distortion at no greaterthan 25 millimicroseconds over the sameband. Relatively simple phase equalizersoperating at intermediate frequency havebeen added at each repeater, reducing sub-stantially even this seemingly small amountof phase distortion.

The necessity for reliability under con-ditions of unattended operation imposesfurther stringent requirements on everypart of the repeater design. The repeatersoperate on commercial power, but twoemergency supplies are provided in theform of a gasoline engine driven alternator,and a bank of storage batteries, which are

automatically cut into service in case ofpower failure.

Typical of the automatic safety fea-tures is the system for guarding themicrowave amplifier tubes against the over-loads that may occur under certain ab-normal conditions of operation. An over-load relay removes the high plate voltage,restoring it approximately one secondlater. If the overload condition has notcleared in that interval, the relay againremoves the high voltage to repeat thesequence. The overload circuit will makefive automatic attempts to restore the highvoltage. If the abnormal condition re-mains at the end of the fifth attempt, theplate voltage is left in the "off" state and awarning is sent to a control center indi-cating that the repeater is not operating.

Terminal EquipmentThe transmitting equipment at the New

Seven repeater stationsare placed on facinghilltops between NewYork and Boston tomake an unbrokenline -of -sight path overthe 220 -mile relay link.

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York and Boston terminals is designed toaccept a video signal from either a bal-anced or unbalanced line, to amplify it,and to apply it to an FM modulator whichimposes it on a 65 mc "i-f" carrier. This65 mc frequency modulated signal is thenamplified in an i-f amplifier and raised tothe microwave frequency in converter sys-tems identical to those used in the repeaters.

The receiving equipment reverses thisprocess, with an FM receiver that acceptsa 65 mc frequency modulated signal from amicrowave -and -converter system identicalto that in a repeater. The second diagramin Figure 1 is a simplified block diagramof the transmitting and receiving equip-ment. The photograph on page 5, showinga partial view of the equipment at the NewYork terminal, includes at the left the twobays which, as is indicated by their ap-pearance, contain the terminal apparatusduplicating that in the repeater stations.

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The three bays at the right hold the video equipment, and FMreceivers and transmitters for the two channels, as well as themonitoring, testing, and calibrating equipment that is an im-portant part of the terminal apparatus.

The third block diagram in Figure 1 shows the main featuresof the testing and monitoring techniques. In the upper part ofthe diagram a transmitter -receiver combination is set for moni-toring the quality of television signals and for checking theoperation of the automatic frequency control circuit.

Because of the nature of television signals, it is advantageousto regulate the frequency of the modulated oscillator to a fixedvalue at those periods corresponding to the tips of the synchro-nizing pulses, and to maintain this regulation regardless of thepicture content of the television signals. To this end, the trans-mitting video amplifier contains circuits that abstract from theinput wave a train of synchronizing pulses completely strippedof all picture signals. These pulses are used to "gate" an auto-matic frequency -control circuit which consequently samples thetransmitter frequency only at the tips of the synchronizingpulses and holds it at a predetermined value. Manual frequencycontrol is also provided for the initial lineup. The FM oscil-lator -amplifier finally delivers its output to the microwavetransmitter at a level of 80 milliwatts. It also provides aninput for an auxiliary system used for frequency monitoring.

To permit the operator to check the quality of the picturesignal as it exists at various points within the terminal duringa television transmission, three video monitoring points areprovided. Signals from these points can be applied to a picturemonitor which displays the picture as it appears in the ordinaryhome television receiver. This unit can be connected so as todisplay the picture as it exists at the point of application to thefrequency -modulated oscillator, or as it is delivered to the localtelevision network. In addition, it can be connected to a moni-toring point located in the microwave equipment, wherespecial microwave discriminator and detector are located.

The picture monitoring unit is also equipped with an auxil-iary oscilloscope which displays the television signal as itwould be seen with the type of cathode ray oscilloscope com-monly used for laboratory testing. This oscilloscope can bemade to synchronize at either line or frame frequency. It isused primarily for observing and measuring the instantaneousfrequency of the FM oscillator during normal operation. Thisis made possible by the use of a monitoring FM receiver whichpermits comparison of the frequency of the modulated oscillatorcorresponding to any portion of the television signal with thatof an auxiliary generator of continuous waves, operating in thevicinity of 65 megacycles, which can be adjusted manually toany desired value. Comparison is made with the aid of anelectronic switch. This consists essentially of two 65 -megacycleamplifiers connected in parallel and so arranged that they arealternately energized for equal periods of time by a multi -vibrator circuit.

Energy derived from the transmitting oscillator is appliedto the input of one amplifier of the electronic switch, whilethe second amplifier is driven by the calibrating oscillator.The composite output of the electronic switch is then im-pressed on the monitoring FM receiver which delivers a videowave containing information concerning the frequencies of both

(Continued on page 39)

Figure 1 -Top, block diagram of repeater equipment for two channels in onedirection. Second diagram, functional arrangement of units in the transmitting and receiving terminals, including the video, FM modulating and demodulating, and microwave equipment. Third diagram, monitoring circuits inthe terminal bays for showing the television signal at various points in thecircuit, and measuring the distortion. Bottom, the repeater characteristics show-ing the flat response over the video band, and the minimum delay distortion.

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February 19487

WTPS -FM, NEW ORLEANSThe historic Times -Picayune and New Orleans Statesbuild a three -quarter -of -a -million -dollar FM voice

wry 9avtge de Naite

NEW Orleans, the magic city . . . theboat ride around the crescent . . .

Antoine's and crepes suzettes . . . the VieuxCarre-these are the landmarks peoplethink of when one mentions this ancientand colorful city. And here it is that twoof the South's great newspapers, the Times -Picayune and its sister the New OrleansStates, the former of which has served thiscity for more than a hundred years, arebuilding one of the most elaborate andcarefully planned FM stations in the coun-try - WTPS-FM, a three -quarter -of -a -

million -dollar plant!H. F. "Bob" Wehrmann is in charge of

this enviable enterprise, as well as of thesister 1 kw AM station, WTPS. We, there-fore, flew down to see him and learn some-

thing about the FM station-its aim, itspolicies, and its technical facilities.

Three major elements - the old city,the newspaper, and the management'sfaith in FM - run like a theme through-out the background of this station.

Management's Faith in FM

First FM.WTPS-FM, "95.7 on your dial," is

clearly designed to become one of the toppower FM stations in the country with aneventual effective radiated power of 270kw. Right now, it is a 1 kw FM station witha 10 kw transmitter on the way and a 50 kwFM on order. It has coverage throughoutthe city and has received letters remarkingon the clarity of its signal from as far as

Clinton, Mississippi. This particularlypleases Bob Wehrmann because he is notonly a one hundred per cent FM man, buthe believes that the possibilities of FM havethus far been underestimated and under-developed by the Industry. With WTPS-FM, growing out of, and owned andbacked by, the city's largest and most influ-ential newspaper, he intends to show theNation what FM can do.

In WTPS's magnificent new studios inthe old Howard Memorial Building onLee Circle, we sat down to hear about thestation. The studio building is a NewOrleans landmark. Formerly a privatelibrary belonging to one of New Orleansold and wealthy families, this handsomeRomanesque edifice of heavy sandstone is

8 Western Electric oaruf,L'Irall

itself an indication of WTPS owners'policy of fitting the station into the life andheritage of the community. The buildingwas designed in the last century by HenryHobson Richardson, the designer of Trin-ity Church, Boston, and an outstandingarchitect of his day, and it was bought byWTPS with a condition by the originalowners that the exterior be in no essentialrespect changed. This condition has beenscrupulously respected. Inside, the studiosare modern and beautifully appointed. BobWehrmann spoke on his favorite subject -FM.

"You find a lot of people saying thatAM's doing all right. It's good enough forthe public. And besides, they say, the pub-lic's got a tin ear. The public doesn't careabout background noise if there isn't toomuch of it - it's used to it, and there'sno use going to the expense of an FMrevolution when AM can do the job.Well, I disagree one hundred per cent!

"I don't really think the public has atin ear. I think more people would liketo listen to FM but are prevented fromdoing so, because receiving set manufac-turers won't manufacture enough FM setsor push them hard enough or as hard astheir AM models, and finally because webroadcasters just haven't worked up anyFM programs worth listening to! Youknow that as well as I do.

'For example, here's what the averageFM program amounts to. Some announcer-generally a one-man FM program staffin himself - sits at a control desk. Heflips a switch and says: 'Good evening,Ladies and Gentlemen. This is StationWXXX-FM on the air two hours a dayfrom midnight to two in the morning,bringing you yesterday's up-to-the-minutenews.' (Perhaps, I'm exaggerating a lit-tle.) 'Now, friends,' the one-man staff

JOHN R. O'MEALLIECommercial Manager - WTPS-FM

announces, 'let's listen to Bing - youknow, ol' Bing Crosby - his new versionof that great new hit, played for the firsttime on FM - I'm Dreaming of a WhiteChristmas . . . And aren't we all . . . heh,heh. . . .' Then having floored his vast in-visible audience, most of whom, if theylead respectable lives, are asleep anyhowat this hour, he puts down the arm on theturntable and for the next hour regales hislisteners, if any, with old records thrownaway by the recording library of the sta-tion's AM partner! That's what we callprogramming in FM!

How Far Is Good Coverage?"Another point stressed by AM parti-

sans, however," Bob continued, "is thematter of coverage. Let me ask you this,how much coverage do you need ? Do peo-ple in Kalamazoo or Timbuctoo listen toNew Orleans stations? Do people inAtlanta or St. Louis listen to New York sta-tions? Of course not. People listen to theirlocal stations-those that come in clear andstrong, and we here want to blanket theNew Orleans area with a strong, clearsignal. We want to cover the areas ournewspapers, the Times -Picayune and NewOrleans States, cover with a day and night,winter and summer, rain or shine service.That's the kind of service we believe FMabove any other type of broadcasting cangive listeners!

"Of course, I know that FM hasn't thesponsors yet and that all is not as easy asit might seem at first glance. But we coulddo better- much better. So what isWTPS-FM doing about it?

"Well, right now," Bob continued,"we're doing two things. Initially, we'retrying to put over FM technically in ourown community. There are only about15,000 FM receiving sets in the New

BILL SEYMOURProgram Manager -- WTPS-FM

LEONARD K. NICHOLSONPresident - Times -Picayune Pub. Co.

JOHN F. TIMS, JR.Vice President - Times -Picayune Pub. Co.

H. F. WEHRMANNGeneral Manager -- WTPS and WTPS-FM

February 1948 9

Orleans area. And even now people don'tseem to know what FM is. For example,when WTPS-FM with much fanfare wenton the air a year ago and we publicizedthe inaugural, the day after the ceremonythe switchboards of the Times -Picayunewere flooded with calls from people say-ing, 'I understand your station is on the air.Why can't I hear it on my radio?' Ofcourse, the answer was they did not haveFM receiving sets - and many of them didnot even know such sets existed!

"Thus, we have been running advertise-ments - about $18,000 worth of them- in our papers to try to teach peoplewhat FM is and what it will do for themand to get people into the stores to buyFM receiving sets. Our ads say: 'FMmeans far more listening pleasure foryou!' They say: 'Do you get your Sto-kowski mixed with Spike Jones ?"Are youtuning in a beehive?' And we show aphotograph of a stormy night in NewOrleans with lightning licking throughthe sky and say: 'Even on a night like this,FM is static free!' As a matter of fact, dur-ing the recent hurricane down here with

its 104 -mile -per -hour wind, uprooted treesand floating debris, WTPS-FM stayed onthe air and came in static free!

"The other thing we are doing is to startto work hard on a real job of programming.WTPS-FM is now on the air twelve hoursa day, from 10 A.M. to 10 P.M. seven daysa week. We used to be on from 2 P.M. to10 P.M., but as is the case in many com-munities, a dealer in FM receiving setscould not even demonstrate an FM set inthe morning because there were no FMstations on the air at that time !

"A few months ago, pursuing our pol-icy of trying to build up and sponsor areal schedule of programs, we secured BillSeymour as our program director. He hasa staff of three writers and four an-nouncers now, and he is working out aseries of different programs, of live pro-grams for FM, 'programs with thought,'we call them. These programs are going tobe of three general types, like most goodAM program schedules: first, entertain-ment - music, specialty acts, drama (wehave our Quizdown, Teen Hall Today, ourSports Rallies and our You Loved It Then

Floor plan of the second floor of WTPS' two-story studio building showing arrangement of Studios A to D.

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g 2JIM

STUDIO I

PASSAGT

STONAGI STOMAGTNICORDINIG

1100M

' COMM&IAA

111"7UOIDSTUDIO (

IIP,ou111,1

1 _ 1 E 1 _

W. T. P S

SECOND FLOOR PLAN

Below: Viewing lobby giving view of Studios B to D in WTPS' new studios.

shows of this type. We are about to beginother programs, one of which, Records forChildren, we expect to become a big thingin radio programming!) Number two, weare working on public service programswhich are of particular importance to us,since we are born of a great public servicenewspaper rooted for more than a centuryin its community life. Here, we have ourTopics for Vets, our Army RecruitingPrograms, our Savings Bonds, CommunityChest Drives and our fund raising cam-paigns for victims of the hurricane andour Cancer and Safety Drives. We are con-templating also a Fight Inflation programand we have in mind an educational pro-gram sponsored by Tulane University'sPsychology and Sociology Departments.And then, we are planning a number ofCommunity type programs - programsborn and nurtured in this colorful com-munity in which we live . . ."

An Old and Exotic CityThe city, as a matter of fact, is the sec-

ond major element forming the back-ground of the station. New Orleans is, ofcourse, one of the oldest and most exoticcities of the Nation. Known as the Cres-cent City because it lies in a crescent -shaped bend of the Mississippi, it wasfounded in 1718 by the French, and itshistory is full of the sound of clangor andriot. The pirate Lafitte hid his gold here;the French and the Spanish mingled toproduce the Creole, the beauty of whosewomen is famous the world over, andfrom North Rampart Street to the riverfront and from Canal to Esplanade Ave-nue, the high lacy wrought -iron balconiesof the Old French Quarter hold the flavorof a time when Jesuits cultivated myrtle,oranges, figs and indigo, and Spanish andFrench made the city a distinctive andwidely known center of artistic and sociallife.

New Orleans is actually a city re-claimed from under water, for most of its

Below Main lobby at entrance to WTPS studios, leading to executive offices.

10 Western Electric rjf I.

200 square miles lie below sea level andmust be drained by its canals from BayouSt. John to the Inner Harbor NavigationCanal and by a system of water drainsinto Lake Pontchartrain and the Missis-sippi. It is, of course, one of the world'sgreat harbors, and along the river frontone can see and smell the ten miles ofspice -laden docks berthing ships from allover the southern world. Here also are themolasses plants and cotton seed oil mills,the oyster Tuggers and sulphur and saltdocks and the famous coffee and bananawharves. And now that the city is oil rich,since Louisiana has become the third of theNation's oil producing states, there may beseen the oil docks to the south.

This colorful background with the pres-ent-day vestiges of many old customs andmanners, the station intends to recapturein programs. As Bill Seymour put it: "Wehave in mind to capitalize on much ofthe city's exoticism. For instance, weare planning to send a man down to theold coffee shops in the Vieux Carre to re-cord the strange and indigenous languageof the coffee market and to record the oldpeddlers' chants nearby ('I got 'nanas! Igot 'nanas!') which have a flavor andbeauty all their own . . ."

The Times-Picayune-A Major InfluenceThe third major element which has in-

fluenced the policies of the station is thenewspaper - the Times -Picayune.

We drove to the handsome Times -Picayune building on Camp and NorthStreets to talk to James Witcher, Promo-

WTPS, the AM sister of WTPS-FM, uses this 1 kwWestern Electric transmitter for its AM broadcasts.Building has space for higher power AM equipment.

tion Manager of the Times -Picayune Pub-lishing Company. Jim Witcher had muchto tell us of the history of this famousnewspaper and how it went into radio.

"The Times -Picayune," Jim told us,"was founded January 25, 1837 by GeorgeW. Kendall and Francis A. Lumsden. Itwas then called 'The Picayune.' Kendallwon journalistic fame as the first editor toorganize a systematic coverage of a war.His pony express from battles of the Mex-ican War which he covered personally per-mitted the Picayune to scoop newspapersmuch closer to the scene of action. Thison -the -spot journalism was a feature ofthis newspaper's stories in all the subse-quent wars which the paper reported -the War between the States, the SpanishAmerican War and World Wars I and II.A staff representative of the Times -Picayune, for example, was present at thehistoric Japanese surrender of World WarII aboard the battleship U.S.S. Missouri.

"On April 6, 1914, the Picayune andthe Times -Democrat, founded in 1863,merged to become the Times -Picayune,and in 1933 the Times -Picayune Publish-ing Company purchased the 53 -year -oldNew Orleans States. Associated with thesepapers are many famous names of the pastand present literary and journalistic fields--such as Mark Twain, Lafcadio Hearn,0. Henry, Roark Bradford, George W.Cable, Gwen Bristow and Dorothy Dix."

"How did the paper make its decisionto go into radio?" we asked Jim.

"This is not the paper's first ventureinto radio," he replied. "As a matter of

fact, we went into radio back in 1923when the paper started station WJBO-the first radio station in this area. Theexperiment was carried on for severalmonths and I believe quite successfully.There are a number of stories about whythe station was abandoned, one of whichI think may amuse you:

An Early Venture Into Radio"It seems in those days the station used

almost entirely local talent for its pro-grams - people from around town -singers, specialty artists, cowboy enter-tainers, musicians from the clubs in thecity. Well, the studios were situated atTulane University and it was thought thatit might be nice to provide at least trans-portation for these performers who gaveof their services without recompense andmerely for the possible publicity. So wedrove them to the studios and back intaxis. At the end of the month, therefore,a bill was presented showing expenses:Taxi fares - $7.65. One of the officialslooked at the bill a moment, turned to theman in charge of the project and said: 'It'stoo expensive. Kill the station !'

"We won't vouch for that story," Jimsaid smiling. "It's more likely the timewas not ripe for a station, the public notequipped for radio here in its primitiveform. Today, of course, there are not onlyplenty of AM stations down here but threeother FM stations as well."

The men who are associated with thepolicies of the station and who run it are

(Continued on page 35)

Wow: WTP$-FM has this Western Electric 10 kw FM transmitter on the way, and a 50 kw FM on order.

el»viary 1948

STANDARDIZED

QUARTZ

CRYSTAL

UNITS

WITH the increasing use of quartzcrystals for oscillator control in every

branch of electronics, the need for stand-ardization of these units has become appar-ent. In the past a limited knowledge ofcrystals and their characteristics made itexpedient for design engineers to requestspecially made or "tailored" units. Thishas resulted in the development of manydifferent types, designs and varieties ofmountings for each crystal application.

Western Electric has just announced anew standardized line of crystal unitswhich should eliminate many of theformer problems confronting the circuitengineer. Designed by Bell TelephoneLaboratories with emphasis placed onestablishing a standard series of crystalunits with nominal tolerances to cover awide frequency range, they reflect signifi-cant advances in design and manufactur-ing techniques over units produced severalyears ago. In general these units aresmaller, more rugged and give better per-formance.

The initial introduction of ten standardtype units within the frequency range from1.2 kc to 50,000 kc is accomplished in fivestandard holders, of which two are identi-cal except for length. By the proper selec-tion of crystal blank size, orientation,mounting arrangement and holder, it isplanned to supplement these ten types to

cover a still wider frequency range andmaintain a minimum number of holdertypes. The following table shows the fre-quency ranges of the ten types introducedto date:

Type Frequency

20J2 IN21E22D22C24A22A24B22B23A

1.2 to 10 kc16 to 100 kc90 to 300 kc200 to 500 kc300 to 1,000 kc2,000 to 10,000 kc3,950 to 10,000 kc4,000 to 15,000 kc5,000 to 15,000 kc15,000 to 50,000 kc

To insure the proper operation of crys-

E E SeedoetRadio Division, Western Electric

tal units with the earlier "tailored" meth-od of manufacture, it was necessary forthe purchaser to supply the manufacturerwith an oscillator circuit for testing. Afterlearning some of the factors governing theoperating characteristics of crystal units itwas possible for the manufacturer toduplicate a "using" circuit and employ itas a reference standard.

While it is not yet practicable from amanufacturing standpoint to define allcharacteristics of crystal units, it is prac-ticable to standardize test oscillators formost applications. Eventually it will befeasible to define all characteristics inde-pendently of the oscillator.

For the new crystal units, the Bell Tele-phone Laboratories have developed a

group of standard test oscillator circuits, as

Below are shown four of the quartz crystal unit types in the newstandardized series. left to right, 23 types, 24 types, 21 types

and 22 types. A 20J type is illustrated in photo at top of page.

12 Westery Electric C a ,LITC g /

TABLE I

The letter coding used to designate theorientation and mode of vibration of theten units in the new series listed on theopposite page is as follows:

First Letter Mode ofof Code Cut Vibration

A AT Thickness shear modeB BT Thickness shear modeC CT Plate shear modeD DT Plate shear modeE 5° X Longitudinal modeJ -I- 5° X Duplex plate, length -

thickness flexuremode

N NT Length -width flexuremode

well as suggested "using" circuits, whichembody the recommended operating con-ditions for the various units. The usingcircuits are correlated to the standard testoscillators. The use of these specific cir-cuits is not necessarily mandatory for goodoperation of the crystal units, but theyoften provide an operating solution wherenone other is available. Figure 1 showstypical using and test circuits for the 22Atype of the new series. In employingother circuits it is desirable to adjust theeffective circuit capacitance and the crystalunit drive to the standard test circuit con-ditions. This standardization of test meth-ods and provision of recommended oper-ating conditions will assure uniformity ofperformance.

The variables which determine the per-formance of crystal units are:

(a) Nominal frequency.(b) Type of quartz plate (angle

of cut).(c) Frequency tolerance.(d) Operating condition.(e) Temperature range.

With the new crystals, nominal fre-quencies have been set, as can be seen inthe table, to cover a wide range in con-venient steps. Specific orientations -angles of cut - have been chosen thatgive a minimum temperature frequencycoefficient for a particular crystal unit.For example, low frequency crystals suchas the 20J and 21E types employ +5° Xcuts whereas high frequency units such asthe 22A and 23A types use AT cuts. Toobtain low coefficients in the other fre-quency ranges, double rotation of the plateis sometimes used.

The frequency of operation in an oscil-lator is determined by the crystal constantsand the "effective" capacitance of the

oscillator circuit (or operating condi-tion). It is necessary to specify thiscapacitance or operating condition. Theoperating condition for most applicationshas been established as 32 mmf, 20 mmf,or series resonance.

To meet the variations in operatingtemperatures and to simplify testingequipment the temperature ranges shownin Table H have been standardized. Typi-cal applications are shown for each rangein the table.

Standardized Coding

In order to simplify the application ofthe crystals, a simple coding has been de-veloped. The number refers to the typeof holder, of which representative unitsare shown in the photographs on the op-posite page; the first letter to the orienta-tion and mode of vibration as shown inTable I; and a second letter indicatesthe performance characteristics under aspecific set of conditions. A new bulletin,*Western Electric Quartz Crystal Units,T-2471, specifies the complete perform-ance characteristics of this new series ofcrystals.

The advantages of thus standardizingcrystal units and their characteristics, froman equipment design point, are apparent.The problem of determining what the con-trol frequency shall be for a particular ap-plication is very much simplified. Itmakes the design engineer's job of select-ing a crystal unit as easy as that of choos-ing a standard vacuum tube.

Figure 1-At right, stand-ard test oscillator circuitfor 22A crystal unit, andbelow, recommendedusing circuit for this unit.

a- CI RI:

VT

C2= R2

TABLE II

-55 to +90°C-Military and mobile use-40 to +70°C-Military and mobile use-35 to + 55°C-Commercial aircraft use+ 45 to +55°C-Oven control use+ 65 to +75°C --Oven control use+ 20 to -1-30°C-Normal room tempera-

ture use--10 to ±50°C-Fixed Station (unat-

tended) use+ 15 to ±45°C --Fixed Station (at-

tended) use0 to +65°C-Marine u:e

Several of the ten standard type crystalunits are used extensively in Bell Systemapplications such as mobile radio, powerline carrier telephone, point-to-point,single sideband and other radio systems.Other applications in which these crystalsare finding wide use include frequencystandards, commercial airline communica-tion, AM and FM broadcasting, police,transatlantic and ship -to -shore radio andmilitary communications and radar.

Through this standardization of crystalunits and the publication of complete char-acteristics it is felt that a more accurate jobof frequency control can be accomplished.

*This bulletin should be obtained from GraybarElectric Co., 420 Lexington Ave., New York 17,N. Y.

C3

C4

C5

G5250MM

0.0IMF

I F-01

Output

0//

1

111111

February 1948 I;

TWO WESTERN ELECTRIC FM TENSWGHE-101.9 mc. With its new 10

kw FM transmitter WGHF, Captain W.G. H. Finch's enterprising station, inaugu-rates its third year of FM broadcasting.Its 1 kw Western Electric FM transmitterwent on the air initially on February 25,1946, and the station began commercialoperation in June of that year.

The station is situated on the 43th floorof a New York skyscraper, 716 feet abovesea level. Its coverage includes the NewYork metropolitan area, and its programshave been clearly received from a distanceof 130 miles.

Its studio equipment includes two West-ern Electric 23C speech input consoles with

109AA reproducer groups and 633A and639B microphones.

Captain Finch, owner and general man-ager of WGHF, is well known in Broad-casting for his work in facsimile. Heserved with the FCC as head of the tele-phone engineering division until 1935.In 1941, he was called to active duty inthe Navy as communications officer,where he received the Legion of Merit forhis service.

WGHF Chief Engineer Veikko K. Westhas experience in both FM and television.He has served as transmitter and studioengineer at WABF and the experimentaltelevision station W2XMT.

Captain W. G. H. Finch (right), owner and generalmanager of station WGHF and Veikko K. West, WGHFchief engineer standing before new transmitter.

Left: THE NEW WGHF's 10 kw FM, one of the firstWestern Electric 10 kw FM's on air in New York.

Below: THE OLD-WGHF's 1 kw FM transmitter,which went on the air February 25, 1946. It is nowthe driver for the new 10 kw transmitter at left.

Western Electric t. (4-11'0.2

GO ON THE AIR IN NEW YORK

WMGM-99.3 mc. One of the first FMstations to go on the air with the newWestern Electric 506 Type 10 kw FMtransmitter, WMGM now broadcasts itsprograms seven hours a day in one of theworld's most thickly populated areas.

The station began operation with a 1 kwWestern Electric transmitter back in 1942at a frequency of 46.3 mc and with thecall letters W63NY (later WHNF). Sincethen, it has expanded in a big way, andthe new 10 kw transmitter is the presentculmination of some carefully laid plans.

In line with its established policy,Western Electric has worked with WMGMto keep its transmitter up to date, and atevery step modern developments have beenincorporated. When the band was raised to88-108 mc, the original 1 kw FM trans-

mitter was converted to transmit at the newfrequencies and its circuits were completelymodernized. Now WMGM's original 1 kw- housed in the new TRANSVIEW de-sign cabinet - serves as a driver for thebrand new 10.

Paul Fuelling, WMGM's chief engineer,has directed the growth of this stationfrom the beginning with plans to make itone of the best equipped in the land.

The FM studios are located in the trans-mitter building at Cliffside, New Jersey.Facilities include a Western Electric 25Aspeech input equipment, two turntableswith Western Electric reproducers, West-ern Electric 1126 Type Program Amplifier,and a Clover -Leaf antenna atop the 335-

foot Blaw-Knox tower adjoining thetransmitter building.

Top: THE NEW-WMGM's Western Electric 10 kw FM,beaming WMGM programs 7 hours a day to New York.At right is Grover Wizemon, transmitter engineer.

Below: THE OLD-Paul Fuelling, chief engineer,stands at the Western Electric 1 kw FM transmitter.

February 1948 15

POWER AMPLIFIERSFOR THE MODERN

AM TRANSMITTERThe Doherty Amplifier in Western Electric's AM transmitterscombines the simplicity of grid modulation with high efficiency

Asthe number of AM broadcast stationsswingswell past one thousand, it

is obvious to every AM broadcaster that inthe future there will be enlarged opportuni-ties, coupled to a new intensity in the paceof competition. Medium and high powerAM transmitters have come on the air inconsiderable numbers, bringing ownersand operators face to face with the impor-tant problems of space requirements, qual-ity of performance, and efficiency ofoperation, that center around high powerbroadcast r -f amplifiers.

The combination of design features inthe power amplifier stage of Western Elec-tric's medium and high power transmittersproduces basic advantages for the AMbroadcaster. Grid modulation of poweramplifiers is in general simpler than platemodulation, requiring less equipment andless modulator power. As is well known,grid modulated amplifiers must be linearamplifiers, which ordinarily entails the lowplate efficiency of linear amplification. Thepre -Doherty design choice was for the high

plate efficiency of the Class C amplifier,which carries with it the necessity for platemodulation.

With the use of the Doherty high -effi-ciency linear amplifier, Western Electric'smedium and high power AM transmittersoffer the advantages of grid modulation,combined with a high plate efficiency.

The principal results can be summarized:1. The tube complement is simpli-

fied, with no high -power audiotubes required. In the 50 kwtransmitter, for example, onlytwo high -power tubes are em-ployed, instead of the usual fourin the plate modulation system.

2. No modulation transformer orlarge plate reactor is necessary forthe modulation system, effectinganother substantial saving in cost,maintenance, and space require-ments.

3. As the modulation system doesnot involve large amounts of

stored energy, it has freedomfrom transient and overmodula-tion surges.

4. Because of the absence of themodulation transformer with itsphase shift, large amounts ofnegative feedback can be derivedfrom the output envelope and ap-plied to the audio input, result-ing in very low noise, hum, andharmonic and intermodulationdistortion, without critical adjust-ment of circuits or close depend-ence on precise tube character-istics.

5. Negligible carrier shift assuresfull utilization of the assigned car-rier power.

6. The Doherty high -efficiency am-plifier can be continuously over -modulated at any audio frequencyfor an indefinite period of timewithout endangering equipmentin any way.

7. Plate power consumption in the

Front panel controls are provided for rapid setting of signal phase relations scope is plugged into sampling jacks at bottom of panel. Two patterns cover allin power amplifier. In left picture above, adjustment is being made. The oscillo- adjustments: 90 degrees, center above, and "in phase", right picture above.

16 Western E7eciric eigaLECtit

At the top of Western Electric's 1 kw AM transmitter can be seen the plifier. The two tubes at the right are in parallel as "Tube No. 1" offour W.E. Type 357 tubes used in the high efficiency linear power am- the Doherty circuit; the two at the left work together as "Tube No. 2".

final amplifier is reduced by afactor of two to one, and the cool-ing load by a factor of three toone, as compared with the usuallinear amplifier.

The operation of the Doherty high -effi-ciency linear amplifier has been described anumber of times.12.3 It may be useful inconsidering it here to reduce the actionstaking place in the circuit to the two essen-tials of the design. Figure 1 is a block dia-gram of the power amplifier in WesternElectric's 1 kw AM transmitter. Rememberthat the low efficiency of the conventionallinear amplifier arises from the fact that itmust be operated with a low r -f plate swing

1. "A New High -Efficiency Power Amplifier forModulated Waves", Proc. I.R.E., Sept. 1936.

2. "Doherty Circuit", Pick -Ups, July 1936.3. -High Powered RF Linear Amplifiers-, Com-

m:sin:ration t, Nov. 1947.

CarrierInput

Phase -Shift

Network

AudioIn put

at its carrier (unmodulated) value in orderto permit the r -f plate swing to vary inamplitude between the limits of "zero" and"twice carrier swing" at 100% modula-tion. The logic of this is readily under-stood: 100% modulation raises the r -fplate voltage swing to twice its unmodu-lated value at the peaks of the modulation.A linear amplifier stops being linear whenthe r -f plate voltage swing exceeds a maxi-mum value, near the d -c plate voltage. Butthe efficiency of an r -f amplifier is propor-tional to the ratio of the r -f plate voltageswing to the applied d -c voltage.

The problem, therefore, is to keep ther -f plate voltage swing at maximum, but toallow modulation to take place withoutoverloading the tube. This makes clear theeffectiveness of the first of the two essentialactions in the Doherty amplifier:

ImpedanceInvertingNetwork

CombinedLoad

Figure 1 - Functional block diagram of power amplifier in Western Elec-tric's 1 kw AM transmitter, showing the elements which work together toproduce the high efficiency of this linear, grid -modulated amplifier.

(1) A linear amplifier tube (Tube No.1 in Figure 1) is operated so that underno -modulation conditions the r -f platevoltage swing (Er) is near maximum, butso the load impedance (Z) drops at anaudio rate in accordance with increases inthe modulation, thus allowing the modula-

(EZ

lion to produce additional power 2-

from the tube without raising the r -f platevoltage swing above the maximum value.

It is clear from simple arithmetic, ofE 2

course, that the power, Z-°, can be increased

either by increasing the voltage Er or bydecreasing the impedance Z. In this case,we wish to maintain Er at a constant level,so increased power is obtained by decreas-ing Z.

The second essential action in theDoherty amplifier is one that, in analogue,can be used to improve the efficiency of anysystem consuming power and carrying avarying load. The principle is most simple.When the load is light, only one tube,functioning as a generator, is required; asthe load increases, a second tube, generatorNo. 2, is brought into action to help carrythe load. Thus the consumption of poweradjusts itself to the varying load. This canbe stated:

(2) A second tube (Tube No. 2 inFigure 1) delivers power to the load inparallel to the first tube, the second tube

(Continued on page 36)

February 1948 17

A NEW VENTILATING SYSTEM ADDS, RELIABILITYTO FM TRANSMITTERS

It insures efficient removal of heat, negligible loading on airconditioning in building, and maintenance of operator's comfort

WTH air conditioning recognized asuch an important factor in increas-

ing operator efficiency and comfort, it isappropriate that the new Western Electric504B-2 (3 kw) and 506B-2 (10 kw) FMtransmitters are designed for installation inair conditioned rooms. This is in line withthe principle that an air cooling system for amedium -power broadcast transmitter mustmeet several important design require-ments, in addition to the basic one of keep-ing the temperature of the larger amplifiertubes within safe operating limits. Theeffect on operator comfort and efficiency,minimizing of dirt, avoiding overheatingthe smaller components in the cabinet,loading on the cooling system in the build-ing, must all be considered as prime factorsin the design.

The cooling system in the new WesternElectric 3 kw and 10 kw FM transmittersnot only has improved cooling action forthe high power vacuum tubes, but alsomakes specific provision for the additionaldesign factors mentioned above. The firstfact of importance is that the heat blownaway from the high power amplifier tubedoes not create a second cooling problem byheating other components in the cabinet.

This is accomplished by connecting aduct to the power amplifier tube to carrythe hot air away without allowing it toheat the air in the cabinet. The conventionalmethod of cooling a high power vacuumtube by air is to force the air through theanode fins in an upward direction. Becausethe grid and filament connections must bemade at the top of the tube, it is difficultto enclose the upper portion of the tube tocarry away the hot air produced and at thesame time have the tube easily removablefrom its socket.

18

ev 744rotold EckzegBell Telephone Laboratories

A novel arrangement is employed inWestern Electric's new FM transmitterswhich is without this disadvantage. Airis pulled down over the tube so the hotair may be carried away from the anodefins through a duct which is not compli-cated by the need for accessibility to ter-minals. Further, this method permits theintake air to cool the glass of the tubeand the grid and filament seals by im-pinging directly upon them. In the upwardblast method there is usually a "dead spot"directly above the envelope and in somecases an auxiliary stream of air is necessaryto cool the glass and terminal seals. In thegrounded grid circuit employed in the 3kw equipment where the grid terminal ofthe tube is a disc, there is an annular spacebetween the inside diameter of the discand the glass envelope to allow air topass from the top of the tube to the anodefins.

Importance of Cabinet TemperatureIf air is blown upward through the radia-

tor of a high power vacuum tube and al-lowed to permeate the cabinet, the tempera -

Figure 1 - Front view of 10 kw FM transmitter. In thecenter bay con be seen the circular housing for theamplifier tube, with the grille into which cooling airis drawn. Air comes into center bay after cooling driver.

ture inside the equipment will be about 35°Fahrenheit higher than if the hot air iscarried away from the fins of the tube byduct. A high temperature within the cab-inet has the four following effects whichare important considerations in the design:

1. The apparatus components in theequipment are unnecessarily sub-jected to higher temperatures, re-ducing the life expectancy of thesecomponents.

2. The hot air will escape through un-avoidable openings in the cabinetand materially add to the load onthe room air-conditioning system.Measurements made on a cabinet thesize of that used in the 10 kw equip-ment show that about 88% of theair will flow through these openingsand only 12% through an opening6" x 14" provided to exhaust thehot air, if no duct from tube to open-ing is used.

3. A cabinet operating at a high tem-perature will radiate heat to theroom adding to the air-conditioningload or causing operator discomfort

where air conditioning is not pro-vided.

4. The high temperature in the equip-ment will exceed temperature limitsestablished for mercury vapor recti-fier tubes causing arc -backs.

From the above it is obvious that a bet-ter design results if the hot air producedby the high power vacuum tubes is carrieddirectly by duct out of the cabinet ratherthan allowed to add to the heat producedby other tubes and components in theequipment before it is discharged.

Because the air is pulled through the finsof the tube, the cabinet is subjected to lessthan atmospheric pressure, and air fromthe room moves in through the seams ofthe cabinet. In urban locations where theexternal air is particularly dirty, and forinstallations in air conditioned spaces, itis recommended that a small blower beadded to the system, in the duct supplyingintake air, to maintain a slight positivepressure in the cabinet. This positive pres-sure minimizes movement of dust from theroom into the equipment, and prevents ex-pensive cooled air from being pushed outof the building through the exhaust duct.

Pressurizing Blower

This added blower in the intake duct mayhave a small capacity since it must forceair only through ducts, not through avacuum tube. The duct and filter loss inthe intake duct in most installations willamount to about 0.13 to 0.4 inches ofwater (static pressure) in comparison withabout 1.0 inch of water for forcing airthrough a vacuum tube. Use is made ofthe intake air to cool the driver unit bydirecting this air through the driver be-fore it reaches the amplifier, in such a waythat it sweeps over the components in thedriver where most of the heat is produced.The air after cooling the driver is thensucked into the high power vacuum tube

ELECTROSTATIC PRECIPITATOROR GLASS FILTER

'I 1

AIRINTAKE

PAPER FILTER

PRESSURIZINGBLOWER

MIXING CHAMBER

NEARBY ROOM

COOL AIRINTAKEDUCT

1I 1

J

eE 1

HOT AIRDISCHARGE

DUCT

\ DAMPER FORAUXILIARY ROOM

HEATING IF DESIRED

BLOWER((THERMOSTATICONTROLLE D)

DRIVER 10 KW AMPLIFIER RECTIFIER

TRANSMIT TER ROOM

in the amplifier unit, through the grille inthe front of the tube housing, as shown inFigure 3.

To avoid pulling dust into the trans-mitter through the intake duct, it isrecommended that a 2" to 4" thick spunglass filter or an electrostatic precipitatorbe installed at the intake of the externalblower. In locations where a large amountof material is carried in the atmosphere,a paper filter may be placed behind eitherof the two afore -mentioned filters to ob-tain optimum cleaning. A fireproof unim-pregnated type of paper filter is preferred.

Figure 3 - Cooling air in10 kw FM transmitter fol-lows course shown in thisdiagram. Most of air flowsfrom intake duct to driverunit, then into amplifierbay, where it is drawn intogrille over amplifier tub*.After cooling tube it is

carried by duct out of cab-inet and discharged. Sec-ondary cooling system is

controlled by thermostat tokeep rectifier tubes from ex-ceeding safe temperature.Filters at intake and pres-surizing blower are addi-tional equipment recom-mended when air carrieslarge amounts of material.

The filters should be located at the intakeside of the blower and the filter dimen-sions should be limited to approximately20" or 24" square to obtain the optimumair velocity for most efficient cleaning.

Figure 1 shows the 10 kw equipment,front view. The cooling air passes throughthe grille in the vertical surface of thecircular housing for the vacuum tube. Thisforces the air to sweep across the top ofthe tube to cool the glass and terminals.Figure 2 shows the rear view of the trans-mitter and the intake and discharge ductsoverhead. The duct at the left is thedischarge duct and the one at the right isfor s"pplying intake air. Openings areprovided in the top of the cabinet for useif it is desired to run the ducts to theceiling. The blower for sucking air throughthe amplifier tube is seen in Figure 2in the lower portion of the center unit.The duct arrangement, and the generalflow of cooling air in the transmitter, areshown in Figure 3. The same system is em-ployed for the 3 kw equipment with theduct connections made at the amplifier -rectifier unit.

(Continued on page 39)

Figure 2 - Bock view of 10 kw transmitter shows blowerin lower part of amplifier bay for pulling cooling air downover tube. Exhaust duct goes up left side, leaves cabinetat top left. Cooling air enters through duct at right top.

19

" THIS IS THE LIFE "

or

Making Your Way With a First Class Ticket in Alaska

Here is a saga of the dayswhen men were

men, but a job like this couldbreak a man's

heart! J. A.Johnson, now a Western

Electric Field Engineer,recalls his pre -Western

Electricexperiences as a radio

operator in the Alaska wildernessesof a canning

factory -- a tale to make the blood run cold and set the strongestkey -pounder

sobbing!

Big job. Is allhopped up at prospect of

nice trip to Alaska and nothingto do but in-

stall new transmitter(not Western Electric)

and operate it for couple of months.Stops in

at home office of canning companyfew days

before sailing.Is handed blueprint diagram

but doesn'tsee set already shipped. Studies

diagram.Makes a few notes.

Thinks must be

swell set.Nice diagram.

Leaves on boat. Meets coupleof Swedes

who were there last year. Both say it is a

helluva placeand that the Supt is a %#*$.

Arrives at Cannery. 3 A.M.Raining. Next

morning up early. Supt says last year's oper-

ator not much good.New operator

tells Supt

no chance of anythinggoing wrong

this season

with brandnew set - latest thing

out - lots

of power.Supt gives operator

three messages

and tellshim to send them right away.

New operatorinquires for

key to Radio Sta-

tion.Doesn't see any antenna.

Nobody knows

where key is. Oldest inhabitantpoints to

shack on hill up in woods.

Goes up to shack.Scraps of wire, old

burned out tube bases,old pieces

of a spark

transformer,and other radio junk lying around

shack. Can't get in door - finds window broken

so goes in that way.Two 18 foot

spreaders and

a 300 foot flat top antennafill room in one

grand tangle,as only phosphor

bronze wire can

kink and tangle. Transmittercovered with

dust, andpulled out from the wall and at a

weird angle.Much hay-wire

stretched around.

Lifts up lid of receiver andlooks in - shud-

ders.Goes outside

and looks around.Nice big

trees - beautifulview of baybirds singing.

Nice place.Goes back inside shack.

Shudders

again.Cleans up place - gets antenna

up -

repairs stovepipeand gets fire going to dry

place out.No light - Cannery generator not

in operationyet. So to bed and early start

next morning.In morning operator

gets help of gang of

husky Swedesto bring transmitter

to radio

P-.1,

el. Tfistrel MITT! R

TePPLES OPP WITN RAU:Pump !NO

t AS14 N

STARTS ENGINE A FLA'SA CURL OF 5 /40K E LiGNTS GO our .!

shack. Box is marked:"FRAGILE - This sideup - Handle

with care - Do not drop - Delicateinstruments." Big Swedes walk around boxthree times, then pick up and set it very care-fully on a truck. They start slowly and care-fully for the radio shack.Operator thinksmust be swell guys to be so nice to help him.Truck wheel slips and bigtransmitter boxtopples off and down into brush in small gullywith resounding crash. Swedes start cussingeach other in loud voices.

Operator shudders.Go down to Cannery to get block and tackle.Come back in an hour and with a lot of heavingand hooing set box up on truck again. Box toobig to go in door so isuncrated outside. Suptcomes up to look at new set.

Operator ex-plains howwonderful it is. Supt tells oper-ator to go down and fix lights in fish houseright after lunch.

Gets back from fish house about 4 P.M. Istold there will be nocannery power for sev-eral days so he had better

use emergency en-gine in shantybehind radiohouse.

Engine isso rusty it won't turn. Engine governor as-sembly missing - broken off. Finds governorin box with old spark plugs, rusty bolts andmiscellaneous junk. Beyond repair.Starts workconnecting up new set in morn-ing. Locates set where it goes. Then chasesall over Cannery to find carpenter to borrowbrace and bit to bore holes in table. Car-penter shop is locked and no one knows when hewill be back

- maybe day aftertomorrow.Decides to get receiver going. Hooks up"B" batteries.

Finds a storage battery thathas a littlelife in it, and listens. Setwon't oscillate.

Takes set out of cabinetand traces wiring. Finds wirecorroded off.Fixes it and checks battery connections.Hears many stations working, with strangecalls. Finally recognizes WXX, station he issupposed to work. Sounds like operator has"Jits", uses bug with weights off so dots don't

come thru thentries to send a mile a minute.Sends a whole

string of dots for an "H" or "5".Operator changes battery voltages. Receiverworks better.Operator feels proud. Laysphones on table to see how far away he can hear"WQN". Steps outside just in time to hear acouple of "Poofs" from

direction of the Can-nery. A couple of more "Poofs", a continued"Poofing", as big dieselengine gets down tobusiness. Roar comes from radio shack. Newoperator dashes in and shuts off receiver justin time to save his pet pair of phones.

Swal-lows hard. He had heardof induction at can-neries. This must be it.

But he was ready. Had along couple of con-densers for such an emergency. Puts them on.Someone has beat him to it with 10 mfds. acrossthe things.Also ground leads in every direc-tion. One big wire

through the dock floor tothe beach.Fellow here last year dug a holefour feet deep and ten feet long in mud underdock and buried stuff for a ground,

he is told.Tries antennas.Long ones - short ones - highones - low ones with a ground and

without aground. Finally hitscombination where canhear "WXX" enough to read through the stuff.Will have to do for now.

Starts hooking up transmitter.Finds wiresent will not reach to back room so puts motorgenerator under 'table in radio room. Hookssetup according to diagram.

Finally gets heragainst wall with all sixteen wires on back.Hooks up themotor -generator,

soldering allconnections, putting on lugs, fixing every-thing shipshape.Dusts off front panel oftransmitter. Shines up nickel.

Just filamentsfirst, with high voltagedisconnected. Fila-ments dull red. Cranks up rheostat. Rheo-stat already against peg.

Looks at voltmeter - shows 8 volts,insteadof 10. Key won't work. Voltage too low for

(continued on page 38)

Turns on transmitter.

PRODUCTION LINEFOR FM TRANSMITTERS

In the Burlington, N. C., plant, Western Electric's new FM transmittersare assembled, inspected and tested on a production linedesigned for efficient manufacture and precise quality control

ASSEMBLY Units of the 10 kw FM transmitter are assembled

and wired on the production line. Picture above shows final assem-bly of driver units; picture on front cover shows the final amplifierand rectifier units on the line. Subassemblies have been wired andtested, are built into frame of transmitter unit at left end of line.Units with all subassemblies in place are moved into position forfinal wiring, as shown in center of picture above. Preformed cabling

is being added to unit to connect all subassemblies. Completed unit atright end of line is ready to be moved to mechanical inspection station.

INSPECTION -Units get a thorough mechanical inspection,covering all soldered connections, tightness of screws, place-

ment of parts, finish, and general over-all assembly check.In picture at right driver units are having soldered connec-tions in subassemblies individually checked. Accessibility

of all wiring and components is apparent. After the mechan-

ical inspection of the separate driver, amplifier and recti-fier units, they are brought together at the testing positionfor the electrical test, as shown in picture at upper right.

22Westmt Ekeric COM11,a0)2

TESTING - Electrical and operational tests are carried out in specially built testpositions, like the one shown above. Permanently installed racks hold the unitsof completed 10 kw transmitter in normal operating relationship. Water cooleddummy load is seen against wall at left. Mobile test bay at right end holds oscil-lators, distortion meters, frequency meter, etc. Before shipment each transmitter istuned to the buyer's assigned frequency and tested at the full rated output. Testdata sheets, showing setting'of all controls, are furnished with each equipment.

23

WSB-A DIXIE INSTITUTIONPioneer southern station installs its fifth Western Electric transmitter

rhold the confidence of the com-nunity over a twenty -five-year career

that includes many historic "firsts" andprogramming innovations - that is thebasic story of a great broadcast station,Atlanta's WSB. In these days of question-ing, both from within and without theindustry, it is invaluable to have a stationlike 50,000 -watt WSB as a living, grow-ing, very healthy example of what broad-casting can mean. A trip to Atlanta to seeWSB and meet the men and women whomake it go, to learn its history, and to in-spect the installation of its new 50 kwWestern Electric transmitter, created inthe traveler's mind a full picture of thestation, one crowded with details of his-toric beginnings, famous events and re-markable community leadership.

WSB was the first broadcast station inthe South, and one of the first in the coun-try. It went on the air in March 1922. Itlays claim to a long list of other "firsts"in the South: first newspaper owned sta-

Vy R. S. Zaffier

tion its owner from the beginning hasbeen the Atlanta Journal, a Southern insti-tution itself; first station in the South tobroadcast religious services - on the firstSunday of operation, March 19, 1922, theservices of First Presbyterian Church ofAtlanta were broadcast, and have beenregularly ever since; first and only50,000 watt clear channel station in thearea including Georgia, South Carolina,Alabama, and Florida; first station in theSouth with network affiliation; etc.

Priority in all these matters demon-strates the vision and progressiveness ofthe men in back of WSB, but even moreimportant is the story of its excellence inprogramming, its service to the com-munity, and its technical competence,which are the real measures of a station'sstature.

The story of WSB's transmitting equip-ments is a fascinating one in itself. Therehave been six transmitters at WSB. Theoriginal one, a 100 -watt amateur rig con-

verted to broadcast use, served fromMarch to June 1922, long enough to formthe background for the delightful "pub-licity shots" shown on page 27. Theywere taken during the first week of opera-tion. Here we see Rosa Ponselle and heraccompanist on a visit to the infant station,listening to the broadcast, with the trans-mitter on the desk in back of them proudlydisplaying its open tank coils and shelf -mounted 50 -watt "bottles." The picture tothe right on page 27 shows the lateHenry Ford on a similar visit to the oper-ating bench in the transmitter room, withthe leads from the electrolytic rectifier onthe high shelf at the right forming a recti-linear pattern on the wall.

Early Visitors

During that first week, many othernotables visited the studio, among themCorra Harris, Roger Babson, Ruth BryanOwen, Alma Gluck, and, the actor OtisSkinner, who read a scene from "Blood

24 Western Electric VOCEMMI1

and Sand," his then current vehicle at theAtlanta Theatre. This attention to news-worthy personalities and emphasis onprograms of solidity and wide interesthave been characteristic of WSB over itsentire career.

WSB's second transmitter, and the fourthat have followed it, have all been ofWestern Electric manufacture. In June,1922, a 500 -watt Western Electric trans-mitter went on the air, one of the firstthree or four equipments of this powerbuilt by the Company. Used until July1925, this transmitter was then transferredto Station WGHB at Clearwater, Florida,and after years of service there, it wasacquired by the Smithsonian Institution inWashington for its industrial exhibit, asan example of early broadcast transmitterdesign.

WSB went to 1,000 watts in July 1925,with a Western Electric 1A installed inthe Hotel Biltmore in Atlanta. The sta-tion went to 5 kilowatts with a WesternElectric 5C in June 1929, building itsfirst separate transmitter building to house

Above, control room before partitions were removedfor new 50 kw equipment. In picture, page 24, thetwo 50 kw transmitters face each other in new room.

the new rig. It went on the air at 50 kilo-watts in July 1933, with a Western Elec-tric transmitter in a new building 10 milesfrom the center of the city. The 5 -kilowatt5C equipment was kept as an auxiliary until1946, then stored away in perfect condi-tion.

In December 1947, WSB took to theair with a new Western Electric 50 kilo-watt transmitter, a 470A-1, standing cheekby jowl with its old 50 kw equipment, toform a highly modern, flexible trans-mitting plant. The installation of this new50 kw transmitter alongside the old one,in a building originally designed for onelarge transmitter only, provides new lighton the adaptability of Western Electric'slarger transmitters, and a full descriptionof the solution of this interesting installa-

tion problem is given later on in this article.To understand the real quality of any

enterprise, it is necessary to talk to themen who make it go. This has particularpertinence in the case of WSB, because ofthe remarkable continuity of its policiesand personnel over its long career. Forinstance, consider John M. Outler, Jr.,General Manager of WSB, genial, shrewdSoutherner who has been with the AtlantaJournal for over 30 years and on the exec-utive staff of WSB for more than 16 years.Mr. Outler explains WSB's general policyin these terms:

"We have never sold time," he says,"we sell programs and a listening audi-ence. Our emphasis from the very begin-ning has been on programs. WSB hasnever been aggressively commercial, andwe have been rewarded with a faithfullistening audience. We operated on astrict non-commercial basis from our be-ginning in 1922 until the latter part of1929, with no income from programs,which meant that the cost of our materialhad to be watched closely. Then it be-came evident to us that revenue wouldallow us to expand our service to the com-munity many times over."

Even with the decision to go commer-cial, WSB did not find it necessary toemploy a salesman - and never has em-ployed an outside salesman to this day.From 1931 to 1940, Mr. Outler handledall the commercial activity of the station.Today one man, Frank Gaither, handlesall sales activities.

Mr. Outler describes his method of"making sales" as follows:

"Actually, I have more than 60 compe-tent sales people on my staff. They are the

Chief Engineer C. F. Daugherty inspects thecompleted installation of new 50 kw transmitter.

General Manager John S. Outler, Jr.

clerks, stenographers, musical and dra-matic talent, writers, producers, engineers,announcers, department heads, who worktogether in our studios. They are the oneswho have made and kept WSB so attrac-tive to our listeners that we can thoroughlydepend on at least 50% of the total tune -in in the city of Atlanta, and a muchhigher percentage in the outlying areas."

Rural CoverageSpeaking of WSB's high acceptance in

rural areas, Mr. Outler corrected any ideathat it was won with programs especiallytailored to a theoretical "hillbilly" or"rural" mentality.

"We find that people in the country likethe same programs as the city people andvice versa," he says. "We have a dailyfarm program - but we believe that thishas about as many listeners in Atlanta asin the country. And our weekly 'BarnDance,' broadcast from a local theatre,which might be considered strictly 'hill-billy' in musical character, has the highestlistener rating in the city of Atlanta of anyprogram we produce. The other side of itis that all our programs, including thosethat could be described as sophisticated orcity -bred, have ratings in the hill countiesequal to or higher than those in Atlanta."

Mr. Outler summed up the descriptionof WSB's general approach to program-ming in this way: "We like our presentpolicy, as it is a continuation of our wholetradition of programming and service tothe community; the South likes it, whichproves that it is a practical policy - itworks! Any skeptic has merely to look atour Hooper ratings."

Miss Jean Hendrix, WSB's young anddecidedly attractive publicity director,

February 1948 25

Exterior of transmitter building. Window at extreme right looks into rear of new 50 kw equipment.

Rear of main units, new 50 kw transmitter, has ample servicing space, accessibility to all components.

talked about some of the programs thathave expressed the station's leadershipin the community, a leadership thatcould be exercised only on the basis ofthorough respect on both sides. She wasparticularly proud of the dramatic series,written by Brad Crandall of the WSBstaff, titled "The Harbour We Seek," inwhich WSB spoke out on the race prob-lem in a way that amazed many criticsof the South, and fought a very effec-tive battle against the Columbians, thatshort-lived Georgia -grown Blackshirt

26

movement. And in the "Battle of the Gov-ernors," the struggle over Herman Tal-madge's accession to the Governorship tosucceed his -father, WSB attacked the Tal-madge methods with everything in itsarsenal.

Such programs as these have won a glit-tering string of awards for'WSB in recentyears: the Variety Award, in 1940, 1942,1944, 1946; American Cancer Society Cita-tion; four U. S. Treasury Citations; UnitedWar Fund Citation, 1944; George FosterPeabody Citation, 1940 and 1946; Na-

tional Conference of Christians and JewsAward, 1946; Billboard Award, 1946.

Miss Hendrix told how Atlantans havelearned to turn to the station for help inemergencies. When the tragic WinecoffHotel fire broke out in December 1946,the staff as though by common consentassembled at the studios and workedthrough the night and next day, as-sembling lists of the injured and missing,answering hundreds of phone calls fromanxious relatives, and acting as a clearinghouse for the Red Cross and local hos-pitals. That the city should have auto-matically considered WSB as a primesource of help in time of trouble seemedto Miss Hendrix the best possible testi-mony to the confidence that the station haswon in its community.

A station with the technical quality andprogressiveness of WSB implies an engi-neering executive of real talent and vision.This man is C. F. ("Harry") Daugherty,the friendly, able chief engineer of WSB,who has had much to do with building thestation to its present eminence. He is theoldest member of the staff in point ofservice, joining in September, 1922, afterhis service as a Naval radio operator inthe 1st World War. He has been ChiefEngineer since 1925. He is a man who ina very short time makes an impression ofsureness, comprehensive technical ability,and open, attractive personality.

He has done much more for WSB thankeep it at the highest pitch of technicalexcellence. In the early days, for instance,he toured the Georgia hill towns in atruck, equipped with one of the early radioreceivers and whole banks of storage bat-teries, to demonstrate the new miracle ofbroadcasting to people at fairs, meetings,wherever there were assemblies of anykind. The job was to teach people to lis-ten, even to prove to them that the thingworked, for skeptical listeners oftensearched the truck for a concealed phono-graph as the source of the music issuingfrom the loudspeaker.

High -voltage area, rear of old transmitter, beforeunits for new 50 were added. (See plan, page 37)

Mr. Daugherty tells the story, in thisconnection, of one elderly cotton planter,who followed the program for some timein a spirit of open disbelief. He was askedwhether or not he went to the telegraphoffice for the cotton reports every day at2:30, as did every cotton operator of theperiod.

"You'll get those same reports right outof this loudspeaker," announced Mr.Daugherty, "at the same time that theyreach the telegraph office." When this featwas carried out on schedule, the skepticwas forced to admit that broadcasting"worked."

Chief Engineer Daugherty has super-vised each of WSB's increases in power,the construction of its steadily enlargingseries of studios, and of the two trans-mitter buildings used to date. He is nowengaged in planning WSB's future in FM,television, and facsimile. Thus HarryDaugherty has had the experience ofpioneering with one of the earliest sta-tions in the country, building it upthrough the growth of broadcasting as apowerful national instrument, and now isdeeply involved in bringing in the muchwider and more varied future of the newtechnical developments in broadcasting.

Two 50's In One BuildingWhen it was decided that WSB's trans-

mitting plant was to be modernized by theinstallation of a new 50 -kilowatt trans-mitter, with the old 50 -kilowatt left inplace as a standby, Chief EngineerDaugherty surveyed the problem of ahousing for the new equipment. The mostefficient and economical solution obviouslywas the fitting of the new transmitter intothe existing transmitter building, withoutany disturbance of the old equipment thatwould interrupt air time, and without ex-tensive additions to the building.

This straightforward, economical, butat first glance improbable housing arrange-

ment turned out to be a practical one forWestern Electric's 50 -KW 407A-1 trans-mitter. A study by WSB's engineeringstaff showed that the new "50" in theWestern Electric line of high power trans-mitters could be fitted into the transmitterbuilding alongside the old equipment witha minimum of alteration to the buildinginterior and very little relocation of ex-isting equipment. The plan on page 37shows in detail how the new units wereadded in the building. The photographson pages 24 and 25 give a "before andafter" story on the new installation.

As can be seen in the photographs andthe plan, a partition was removed whichhad divided the space in front of the oldtransmitter into a control space and anentry space. With the removal of this par-tition, a much larger control area wasavailable. Then an office area at the rightfront of the building was split up, partof it being added to the new control area,and part of it reserved for installation ofthe main units of the new 50 kw equip-ment. These changes created an amplecontrol area with the old transmitter acrossthe back and the new one at right anglesto it at the right end of the area, as canbe seen in the photographs.

It should be interesting to point out theactual dimensions of the new room, shownat the right front of the plan, in which thenew rig is installed. All of the main unitshave been fitted into a space approximately16' x 10', with ample room in the rear formovement of the engineer who must domaintenance or servicing. The Dohertyhigh -efficiency amplifier should be givengreat credit for the compactness that makespossible an installation of this kind. Therelatively small size of the final amplifierand associated components such as thepower transformers, cooling system, fila-ment supply, etc., are prerequisite to in-stallation of a complete'50-kilowatt broad-cast transmitter in a space of this size. The

Rosa Ponselle samples WSB's program during first week on the air,March, 1922, with the original 100 -watt transmitter in background.

photograph at left center of page 26shows the rear of the new transmitter.

The rectifier, choke coil and thyriteprotector for the new transmitter werefitted into the high -voltage area inback of the old rig by moving certain ofthe corresponding units of the old trans-mitter a few feet toward the left wall ofthe area. Similarly, the plate voltage regu-lator and power transformers for the newtransmitter were installed in the areaalready set aside for the correspondingunits of the old transmitter. It was onlynecessary to add a new chain link fencearound the somewhat enlarged area forthese latter units.

Spray Pond for CoolingThe water cooling system for the new

transmitter uses a basement area directlyunder the transmitter. It proved to beeconomical and technically efficient to usethe spray pond installed with the oldtransmitter as the basic cooling agent forthe new one. A new circulating systembrings the cold spray pond water into thebasement. There it receives, in a set ofsmall heat exchangers, the heat carried bythe distilled water that circulates over thetube anodes, through the heat exchangers,into a tank, and back again, in a closedsystem. It occupies in the basement a16' x 10' space corresponding to thesimilar space for the transmitter just aboveit, with ample room for servicing, since agood part of the equipment is on the wallsof the room.

A further and most important way inwhich the new transmitter has fitted in

# beside the old one without disturbance isin its connection to the original two -wireopen transmission line. The WSB staffwanted, if possible, to use their transmis-sion and radiation system, without exten-sive changes, for the new equipment aswell as the old. The new transmitter has

(Continued on page 37)

Henry Ford was another early visitor to the transmitter room, pro-nouncing his interest in and approval of new art of broadcasting.

CUSTOM BUILDERS FOR BROADCASTING

How specialists in high quality motion picture sound recording

apply their unique skills to audio systems for radio broadcasting

THE Electrical Research Products Divi-sion of Western Electric-commonly

referred to as ERP Division-is not aswell known to the broadcaster as to themotion picture industry. Electrical Re-search Products, Incorporated, was formedin 1926 as a subsidiary of Western Elec-tric, to handle by-products of research byBell Telephone Laboratories having appli-cation in other than the telephone field.These organizations produced sound forthe first really successful talking motionpicture, premiered at that time, and the in-terest aroused by this event establishedsound recording and reproduction asERPI's chief activity. In 1941 ERPI wasmerged into Western Electric, becoming aDivision of Western Electric with itsheadquarters in New York but carrying onsome of its former functions.

The Products Division maintains officesand a laboratory in Hollywood for carry-ing out the design, manufacture andapplication of recording equipment formoving picture studios, calling uponBell Laboratories for fundamental devel-opment. Indication of the widespread useof Western Electric sound recording equip-ment may be found in the screen title credit

ev 7 4. eoNzetElectrical Research Products Division

Western Electric Company

at the beginning of motion pictures re-leased by M.G.M., Fox, Paramount, Co-lumbia, Universal, Goldwyn, Vanguard, J.Arthur Rank Organization, United Artists,and other important producers. In addi-tion, the Westrex Corporation, a subsidiaryof Western Electric, distributes motion pic-ture recording and reproducing equipmentin all countries outside the United Statesand Canada.

Techniques Applied to BroadcastingWhile the mechanisms for recording

sound on film, and for reproducing it, arepeculiar to motion pictures, the transmis-sion and control apparatus involved in suchsystems bears a close resemblance to theaudio facility equipments required bybroadcasters.

Performance requirements are compar-able: high -signal-to-noise ratio for normalconditions of input and output, minimumabsolute noise at the grid of the first pre-amplifier tube, wide frequency response,minimum harmonic distortion, and mini-mum crosstalk between circuits. Control ofsystems grounding and shielding is suchas to preserve the individual performanceof each of the various components which

comprise the whole system.Film recording divides into two main

categories and requires several types of sys-tem assemblies:1. Original Recording.

Dialogue recording on set duringpicture filming requires a portablemixer on the set with the remain-der of the system located in centralrecording rooms, or in a truck.Portable equipment is also re-quired for dialogue and, infre-quently, musical recording "on lo-cation," i.e., remote from the mo-tion picture studio in either out-door or indoor settings. This latteroperation corresponds to remotesor nemos in broadcasting, exceptthat the sound is usually recordedat the location rather than beingtransmitted to the studio. Soundrecording systems for locationwork are, in general, less elaboratethan studio installations and thepickup and control equipment ismore comparable to portablespeech input equipment for broad-casting.

(b) Musical Recording. This requires

(a)

28 Western Electric Otja_41.171

4

a much more elaborate mixingconsole, and is a fixed installation.Such consoles require a minimumof two men for operation.

(c) A composite type of system. Thismay be used for dialogue and mu-sical recording in a fixed installa-tion, or for rerecording.

2. Rerecording.This process precedes the preparationof a release print and combines the out-puts of a number of sound records suchas original dialogue, music, and soundeffects. The rerecording console hasfacilities for mixing as many as twentysound tracks, and, in addition, containsa variety of equalizers and filters forsimulating sound effects or for com-pensation for acoustical conditions ex-isting on the set. Such a console may re-quire four to eight men for its opera-tion, and is, consequently, a large andcomplex structure.

The typical custom built audio facilityconsole for broadcasting corresponds mostclosely to the motion picture musical orscoring recording console, the chief differ-ence being the fact that operation for radiois by one man and for motion pictures bymore than one man. The output of theseconsoles supplies either a transmitter ornetwork for radio broadcasting, or filmrecorders in motion pictures. Both indus-tries utilize disc recording, the radio indus-try for transcriptions and the motion pic-ture industry for immediate playback forchecking musical recording.

It can be appreciated that a backgroundof some twenty years in the design and ap-plication of transmission systems for mo-tion picture use has much to offer whenapplied to the radio broadcast and televi-sion sound fields. It is not surprising, there-fore, that the Radio Division of WesternElectric employs the facilities of theElectrical Research Products Division in

A A al A A A 11% PI API Pill A Pt A

111 II 111 II III III III 111111111111

.

TOP: First of three typical operations inthe construction of audio facilities forbroadcasting use - a wiring form formaster dispatching line channel cables.

CENTER: Wiring master control equip-ment for Mutual - Don Lee's KHJ, an-other vital operation in the construc-tion of audio facilities for broadcasting.

BOTTOM: Testing a master control panelfor KHJ - a final step in preparationof audio facilities for broadcasting useby Electrical Research Products Division.

29

the production of custom built audiofacilities for broadcasting use.

After consultation with a prospectivecustomer on his requirements for custombuilt audio facilities, a proposal is preparedby the Radio Division. This proposal out-lines briefly the type of equipment to befurnished, its physical characteristics, oper-ational characteristics and guaranteed per-formance. Drawings are included coveringthe physical dimensions of the proposedconsoles and power cabinets. Location ofequipment controls and a jack field layoutare also included. A block circuit schematicindicates the operating and transmissionfeatures of the system. Usually a descriptionof the functional operation of keys and re-lays is included, since it may not be obviousfrom the block schematic what sequenceof switching operations is initiated by theoperation of a key. Lists of standard equip-ment items to be supplied are also included.The methods used to measure the transmis-sion characteristics are given, together witha statement of performance. The proposalalso serves the Products Division as an in -

Operations for motion picture recording system oresimilar to those required in constructing audiofacilities for broadcasting. Here is wiring form.

Another operation in ERP Division's work for mo-tion pictures. This is a console assembly for re-

cording console designed for MGM International.

troduction to the project and serves as abasis for the estimation of shop costs.

With the signing of a contract withthe customer by Graybar, orders areplaced by the Radio Division, and specificengineering and drafting to enable con-struction of the equipment is begun by theProducts Division. Engineering may bedivided into mechanical, involving thesheet metal consoles and cabinets; and elec-trical, involving circuit schematics and wir-ing information. Shop drawings are pre-pared covering the construction of themain console components, as well as all thenecessary mechanical details. The latter in-clude various mounting details carryingpads, relays, coils and similar items, andvarious types of plug-in drawers to accom-modate amplifier and rectifier components.The art work from which the photo -etchedmats are made must also be prepared.

42,000 Square Feet of BlueprintsThe magnitude of the drafting program

for such a job as KHJ's new Hollywoodstudios and dispatching center for Mutual-Don Lee may be appreciated by the fol-lowing facts: for the Studio Consoles, 100original tracings and 151 running sheetswere required, and the total area of theissued blueprints was 12,000 square feet;for the Master Control Room equipment,192 original tracings and 288 runningsheets were required, and the total area ofthe issued blueprints was 30,000 squarefeet. The total weight of all blueprintsused was 660 pounds.

Circuit information to be developed in-cludes a system two -wire schematic. Thiscovers all equipment items, even thoughthey may be distributed between a console,power cabinet, or rack. Running sheets arecompiled which indicate to the wiremanand customer necessary interconnectionsbetween major units. Unless the consolesto be wired bear resemblance to others forwhich wiring forms have been designed, itis necessary to lay out such forms and to

make forming boards for the use of thewiremen. Such work involves a proper seg-regation of high and low level speech cir-cuits, signal circuits, various d -c circuits,and power. Where necessary, shielded pairsmust be specified and the treatment oftransmission and shield grounds indicated.

After this information is available, andupon completion of the console furniture,assembly and wiring may be started. As afinal step before delivery all individualcomponents and the system as a whole aregiven operational and transmission tests.The latter include gain, frequency, noise,distortion, and crosstalk checks. In addi-tion, key or relay clicks are removed bysuitable means, with the result that thecustomer receives a completely tested andoperating system, which can then be in-stalled with a minimum of effort.

The philosophy behind an all-inclusivestructure, such as a console, which housesall items from the microphone preampli-fiers to the line amplifiers as well as moni-toring and talkback amplifiers, is that itpermits the completion and testing by thesupplier of a complete system. Hence thecost of the console normally includes theexpense of assembly and testing whichwould with other special designs be as-sumed by the customer. The componentsnormally housed in a console may, ofcourse, be redistributed between a simplemixing desk and various relay racks andwall cabinets. In this form, however, morespace is required for a given facility andmore expense is involved for customer in-stallation and supervision, and the re-sponsibility for the ultimate system per-formance must of necessity be assumedby the customer.

Manufacture of such custom built ap-paratus is not, of course, restricted tostudio type audio facilities. Master dis-patching room systems have been designedand manufactured following essentially themethods outlined. The master dispatching

(Continued on page 35)

Completed recording control console designed forMGM International. Console is typical of ERP

Division's quality work for the motion picture field.

30 Western Electric f; I. t'T U2

Vice President and Treasurer, J. HaroldRyan; General Manager, Lee B. Wailes;Chief Engineer, Glen C. Boundy. The FortIndustry Company has a total of seven AMand six FM stations. The company has onorder three Western Electric 10 kw FMtransmitters for Atlanta, Georgia, Miami,Florida and Lima, Ohio.

FM1ING AROUND THE CLOCKThe Fort Industry's WJBK-FM Detroit is on the air 24 hours a day - its

1KW transmitter has not been turned off since October 10, 1947

DETROIT'S WJBK-FM is one of the na-tion's first FM stations to go on the

swing shift. In order to give both day andnight service, the station is planning acareful separate programming schedule,but at present all programs are similar tothose broadcast over WJBK, the sister AMstation.

The station is now operating with a 1 kwWestern Electric 503B-2 transmitter.When equipment on order is installed, thestation's power will be boosted to 10 kwand its effective radiated power, authorizedat 33 kw, will make it one of the mostpowerful FM stations in the state.

Periodic checks made by a commercialfrequency checking service since the sta-tion went on the air June 19, 1947, showthat the WJBK-FM transmitter stays onfrequency; in fact, many of the checks showzero variation from its assigned frequency.

Program reception has been reported atdistances of well over 100 miles. Chief En-gineer Paul Frincke, who supervises boththe AM and FM operations, has receivedDX reports from as far away as Zanesville,Ohio-approximately 150 airline miles.

WJBK-FM is owned by the Fort Indus-try Company; President, George B. Storer;

RIGHT: WJBK-FM Chief Engineer Paul Frincke standsbefore the Western Electric 1 kw FM transmitter.

BELOW: Ralph Elvin, managing director of WJBK andWJBK-FM, in charge of both AM and FM operations.

In addition to WJBK and WJBK-FM,the Fort Industries organization owns orhas an interest in such stations as WSPO,Toledo, Ohio; WWVA, Wheeling, WestVirginia; WMMN, Fairmont, West Vir-ginia; WLOK, Lima, Ohio; WAGA, At-lanta, Georgia; WGBS, Miami, Floridaand KIRO, Seattle, Washington.

31

NEW ORDER WIRE PANELFOR BROADCASTERS

Simple, compact, ring down and lamp indication panel has termi-nation facilities for 12 order wire lines-including operator's subset

THE new Western Electric RD -101Order Wire Panel is a small switch-

board unit for the telephone transmissionof operating orders between broadcastingstation control rooms and remote oper-ating points. It is a compact, flexible, com-plete and very useful operating unit forserving a maximum of twelve order wirelines. Two or more units may be used to-gether to handle a greater number of lines.

Ring down, relay lamp indication isprovided for each of the twelve order wireline circuits. The relays and lamps are partof the unit assembly, as are an operator'ssubset equipment of the preferred anti-sidetone type, an alarm buzzer, a set of sixprogram -line transfer keys, also regularand emergency battery and ringing sourcetransfer keys. All of this equipment occu-pies only 51/4 inches of panel space on astandard 19 -inch rack cabinet or desk unit.

Production and dispatching of programsfor broadcasting and like services fre-quently involve, of course, intercommuni-cation between two or more operators.Ready communication between them isessential for proper program coordination,especially in the case of remote "pickups"where programs are produced at pointsoutside studio locations and transmittedto a studio or to master control for distri-bution to AM or FM transmitters or net-work feed lines.

Order wire line circuits used for thisservice are primarily of the "local battery"or magneto type in which a single pair ofwires to each remote point is used for talk-ing and signaling. Talking current is gen-erated at each station by means of a localbattery, a carbon type transmitter elementand an induction coil so arranged that onlythe alternating (voice) currents reach theline. The telephone receiver is connectedto the induction coil circuit in such a wayas to make it fully sensitive to voice cur-rents coming in over the line but relativelyinsensitive to much stronger voice cur-rents from the local transmitter element.(This briefly is the "anti-sidetone" fea-ture.) Signaling is done by ringing on theline using 20 -cycle alternating current asin telephone practice.

By use of magneto type line circuits forcommunication, the standby program linecircuits can at times be used for communi-cation service when not transmitting pro-grams. The program line transfer keysassist in this interchange.

Unusually CompactThe whole unit has an unusually com-

pact construction, as may be seen in thephotograph above, and its operation isnot impaired by tilting to the rear aswould be convenient in a desk panelmounting. Instead of requiring a separate

"Telephone Panel" for the operator's sub-set equipment, adequate subset equip-ment has been included, and the only tele-phone set equipment which must be pro-vided externally is a suitable hand tele-phone instrument and switch hook such asthe Western Electric 214AW-3F HandTelephone set. If an operator's head tele-phone set such as the new Western Elec-tric 52AW or 52BW is available, it canbe plugged into the "Tel Set" jacks seenin the lower right corner of the front panel,and the panel operated whether or not thehand telephone set is connected.

External power to operate the panel isalso to be supplied. A maximum of 50watts of 12 or 24 -volt quiet direct cur-rent will supply talking battery and powerfor locking up the line relays and illu-minating the lamps. Five to ten watts ofstandard 20 -cycle ringing current is usuallyadequate. Two of the rotating type keysseen near the lower left of the front panelare for transfers between regular andemergency battery and ringing supplies. Aset of dry cells is adequate for the emer-gency battery and a hand generator of thethree or five bar type can be used for thesestandby sources. The third rotating typekey is a cutoff key for the alarm buzzersupplied in the panel to sound an audibleindication of an incoming call.

The twelve line keys with their asso-

32 Western Ekctrie Ogarra,02

ciated indicator lamps and designationstrips are arrayed across the top half of thefront panel. The line relays can be seen atthe rear of the panel, where they aremounted on a hinged panel which can bedropped back for access to the wiring sideof all apparatus. The terminal strip at theleft rear is not hinged and serves for allconnections to external circuits.

One of the features of this order wirepanel is the facility for transfer betweenregular and emergency order wire line cir-cuits. The six line transfer keys seen inthe central portion of the lower half of theface panel are arranged for connectionduring installation to jacks on the incom-ing lines rack so that they can be patchedto line circuits as required. The circuit foreach of these two position keys is shownin Figure 2 in the normal or unoperatedkey position - "regular line in" feeds"regular line out" and "emergency linein" feeds "emergency line out." With thekey operated, the lines are transposed sothat "regular line in" feeds "emergencyline out" and "emergency line in" feeds"regular line out."

Simple to OperateThe operation of this order wire panel

unit is simplicity itself. As soon as ringingcurrent comes in to any one of the twelveincoming order wire line circuits, the relayassociated with this circuit closes and indoing so illuminates its associated indi-cator lamp and also sounds the buzzer, ifdesired. The control room operator, notingthe illumination of one of the order wireline indicating lamps, operates the associ-ated order wire line key upward to theTALK position, which releases the relay,extinguishes the line indicating lamp andbuzzer and connects the control roomorder wire subset to the line over whichthe incoming call is being received. Con-versation between the operator at thepanel and at the remote point can then becarried on. When conversation has beencompleted, the operator simply restores theoperated line key to its "signal" position,so as to make possible receipt of the nextincoming call over its associated incomingline.

Whenever the operator wishes to placean outgoing call over one of the orderwire lines, he needs only to press the ap-propriate line key to the downward "non -locking" RING position. As will be notedon the Figure 1 schematic, this discon-nects all relay and subset apparatus fromthe line circuit and connects it to the 20 -cycle ringing bus. A resistance lamp con-nected in series with the 20 -cycle ringingcircuit prevents a defective (grounded orshorted) line from disabling the ringingsource by abnormal drain.

The call signal buzzer is a conveniencewhen the operator does not happen to benear the order wire panel position. Thisbuzzer sounds whenever any of the twelveorder wire line relay units responds to anincoming call. A cutoff key mounted onthe control apparatus panel assembly pro-vides a means of disconnecting the buzzerwhenever it is not needed.

While not primarily designed for inter-connection between two or more orderwire line circuits, it is possible to makesuch connection by operating the asso-ciated line keys to the TALK position.This connects the lines to the talking busin the panel, and not only can the paneloperator talk with the remote points butthe remote points so connected can hearand talk with each other. As with allmultiple connections, the transmissionlevel falls as more and more lines areconnected in multiple, but it is entirelypossible under the line conditions usuallyencountered, for all twelve lines and the

Figure 1 -

panel operator to be interconnected withoutfalling below an adequate communicationlevel. The exact levels, of course, dependon the length, type, impedance and noiselevel of lines and the efficiency and im-pedance of the telephone set equipmentused both at the panel and at the remotepoints.

For incoming ringing signals, the relaysare sensitive enough to respond to about35 volts of 20 -cycle current at the relayterminals which should be well within thecapabilities of both three and five bar gen-erators used on the remote telephone setsfor 1400 to 2000 ohm lines.

The battery supply to the panel can beeither 24 -volt (20 to 28 -volt range) or 12 -volt (10 to 14 volt range). As shipped,the panel is connected and equipped withlamps for 24 -volt operation. For 12 -voltoperation, a few straps need to be con-nected and the Western Electric type 2JSwitchboard Lamps replaced by 2FSwitchboard Lamps.

LINES 3 TO II INCL SAME AS LINES 1,2 AND IT

OPE N'SHANDSET

c -1L -

JACKS ON RACK NOTSUPPLIED WITH PANEL

Block layout of RD -101 Order Wire Panel, showing keys, relays, lamps for each of 12 lines.

Figure 2 -

SCHEMATIC OF ONE TRANSFER KEY CCT

TO HANDSET

20- RINGINGSUPPLY

ORERATOR'TEL SE T" JACKS

TALKOCX

BATTERYGR UNO

BUZZER BUZZER ALARMCONTROL RELAY

KEY

STRA FORVO,T

04OA110 44444, VOLT

LINE

LINE LAMP

SCHEMATIC OF ONE LINE CCT.

TO OTHERLINE CIRCUITS

LINE KEY

TO OTHER

LINE CIRCUITS

Detailed schematic of one line circuit equipment and (insert upper left) a line transfer key.

February 1948 33

"Protected Networks"A New Technique in Hearing Aids

N the field of sound reproduction, anI important modern application is thehearing aid. These tiny audio amplifiersinterest technical men because of the tech-niques used to provide ample amplifica-tion, power output, and fidelity in a unitas small and light as possible. WesternElectric recently introduced two new hear-ing aids with self-contained batteries,Models 65 and 66, that are smaller andlighter than previous designs. They includenew developments that solve the problemof protecting critical components frommoisture, dust, and dirt, and make foreasier, more rapid servicing.

"Protected networks" is a feature ap-plied to hearing aid construction for thefirst time. This principle includes the seal-ing of circuit elements in moistureproofblocks of plastic, the provision of a specialplastic -coated metal foil membrane as amoisture -resistant cover across the face ofthe Rochelle salt crystal microphone, andthe mounting of a tone control network in-side the metal microphone case for physi-cal protection and electrical shielding.

The provision of two models instead ofone resulted from studies which indicatedthat one instrument could not conven-iently and economically supply the needsof all who use hearing aids. Accordingly,Bell Laboratories designed one model (the65) for those who have moderate hearinglosses, and a second (the 66) with greaterpower output for those having severelosses and with extra fidelity for those de-siring maximum acoustical performance.

Model 65 weighs only six ounces and isabout four and one-third inches long. Itsresistance -coupled amplifier is powered bya miniature 15 -volt "B" battery and 1.5 -volt "A" battery and has a frequency re -

L

sponse with a gradually rising characteristicthat effectively covers the range that con-tributes most to speech intelligibility. Atone control permits tilting the frequencyresponse upward toward the higher fre-quencies at an additional 4 or 8 db peroctave. This allows the user to discriminateagainst unwanted sounds such as streetnoises, etc., or to change the response tothat most pleasing to the individual.

The condensers, resistors, and tubes ofthe three -stage amplifier are connected to-gether with the elements' own leads andmolded into one compact, moistureproofunit, 15/8 by 11/2 by 34 inches. Delays inservicing are eliminated by the simple andrapid replacement of the entire unit. Thetransformer -coupled output of the ampli-fier is connected by a cord to a midget typereceiver worn in the ear. Output capabili-ties of the 65 make it suitable for com-pensating hearing losses up to 65 db, withan operating cost well under a cent anhour.

The Super 66The Super 66 is slightly larger than the

65 and weighs eight ounces, includingself-contained batteries. The two inter -stage coupling networks are sealed in sepa-rate blocks of moistureproof microcrystal-line wax and installed in the amplifier unitas indicated in Figure 2; tubes are notsealed in as they are in the 65. This con-tributes to the versatility of the 66, wheretwelve different fitting combinations aremade available (in order to meet varyingpower requirements) by the choice of twooutput tubes, self-contained or separatebatteries, and four receivers (three air con-duction and one bone conduction) for eachtube and battery combination. The tone

Figure 1 - Simplified schematic of Super 66 Hearing Aid Amplifier. Protectednetworks are shown by shaded areas. MK 1 (left) is tone control network andmicrophone. Ni and N2 are interstage coupling networks in moistureproof blocks.

Held in the right hand is Hearing Aid Model 65,designed for persons with moderate hearing losses;in left hand is the Super 66 with a high poweroutput for persons with severe hearing losses.

control provides three different frequencyresponse variations for each fitting combi-nation. Operating cost, with self-containedbatteries, is less than a cent an hour. Thebattery compartment may be detached andreplaced with a separate battery pack con-nected through a cord to provide extrapower and even lower operating cost.

Frequency response of the 66 is uni-form within ± 6 db from 250 to 4000cycles when used with a 724C midgetreceiver. Other receivers can be used forhigher output with some reduction in re-sponse above 3000 cycles. The 66 has thelowest distortion and the best frequency re-sponse of any aid that has been tested byBell Laboratories. It is capable of deliveringa sound pressure level as high as 136 db

(Continued on page 38)

Figure 2 -- Two views of amplifier chassis of Model 66 Hearing Aid. Left aremoistureproof blocks containing interstage coupling networks, one tube, toneand volume controls; at the right are microphone, two tubes and transformer.

Western Electric V4T71:1,UO2

WTPS - FM, New Orleans(Continued from page 11)

progressive and experienced in communi-cations media.

President of the Times -Picayune Pub-lishing Company is Leonard K. Nicholson,a prominent New Orleans business manwho has been associated with the papersince 1902. He has been President of theCompany since 1918, four years after thePicayune merged with the Times Demo-crat.

Also on the policy -making staff of thestation is Vice President and BusinessManager of the Times -Picayune Publish-ing Company John F. Tims, Jr. Associatedwith the company since 1908, Mr. Timsbecame business manager in 1923, treas-urer in 1932 and vice president in 1939.

The Men Who Run ItThe actual operation and direction of

the station are in the capable hands ofHenry F. (Bob) Wehrmann, GeneralManager of WTPS-FM and WTPS. BobWehrmann graduated from Tulane Uni-versity School of Engineering and was aham operator from way back with call let-ters 5SZ. For 13 years, he acted as pur-chasing agent for the Times -Picayune Pub.Co. and was instrumental in guiding thepapers into radio broadcasting. He hasdevoted the past two years exclusively tothe organization and building of WTPS-FM and its AM sister.

Commercial Manager of WTPS-FM isJohn R. O'Meallie, another graduate ofthe Times -Picayune staff. John served for13 years as an account executive, handlingmajor retail accounts for the Times -Picayune and the New Orleans States. Hebrings to WTPS-FM 25 years' experiencein the advertising field.

For the important position of ProgramManager, the Station has Bill Seymour,who has a wide experience as writer, actor,news writer, announcer and supervisorat such stations as WLW, Cincinnati;WKRC, Cincinnati, and WBBM, Chi-cago.

The engineering force is headed byTransmitter Supervisor George W. De-Blieux and Studio Supervisor EdwardHolmes. George began his career as anengineer in the Electric Service Section ofthe New Orleans Public Service. In theNavy in World War II, he was AviationRadio Technician, and for the last year hasbeen assisting in the planning, construc-tion and maintenance of the studio trans-mitting equipment at WTPS-FM.

Studio Supervisor Edward G. Holmes isa graduate of Tulane University's Elec-trical Engineering School. A Radar Officerin World War II, he received his first-class

phone ticket in 1946 and went to workfor WTPS-FM installing the FM trans-mitter and later changing its frequencyand installing all studio equipment.

On the Air Since January 1947The Station has been on the air since

January 3, 1947. It is Western Electric -equipped from microphone to trans-mitter.

In the early part of that year, the stationbroadcast entirely from its studios, thetransmitter being set up in a special roomthere while the transmitter building andantenna were being erected at Gretna,across the river.

The studios are on an elaborate scale.In the two-story fortress -like edifice onLee Circle are main lobby, business,executive, production and sales offices andthe large and handsome Studio A, theceiling of which is two stories high. Onthe second floor are Studios B, C and Dlined up along a luxurious viewing lobby.The basement itself contains a lobby anddemonstration and assembly rooms as wellas space for the electrical and air con-ditioning equipment and for storage. Thelayout of these elaborate studios is shownon page 10.

Across the river in Gretna is the trans-mitter site within view of the skyscrapersof New Orleans about two miles away. Thetransmitter building is a large 60 by 40 -foot Quonset hut. Inside this building, thetwo Western Electric transmitters stand inthe main area at right angles to each other,the 1 kw AM unit with space for ex-pansion to a higher power on the left asyou enter and the 1 kw FM with space forthe 10 and 50 kw units to the rear center.Speech input equipment is placed on theright.

When the station is complete, its West-ern Electric equipment will include in ad-dition to its FM transmitter, a 10 kw AMtransmitter, 23C speech input and two 25Bspeech input assemblies, 639B and 633A

Gen. Mgr. H. F. Wehrmann enters WTPS Studios.

microphones, eight transcription turn-tables, two 22D remote amplifiers, ten753C loudspeakers (cabinet type), seven124F amplifiers and other studio andtransmitter building equipment.

No story of an FM station which placesits expectations in good programming andgood coverage would be complete withoutsome comment from the listeners them-selves. To provide this element, we did alittle doorbell ringing of our own. Wesecured a few names from dealers in FMreceiving sets and went around to visitthese FM set owners to see what they hadto say about FM and the stations whichprovide it. Of course, with a sample assmall as the one we were able to secure,it would be too much to make any majorgeneralizations, but some of the commentsmight prove of interest.

Listeners' CommentsAll of the set owners replied that they

preferred FM to AM reception, giving asreasons the clarity, quality and freedomfrom static. All set owners found the musi-cal programs most interesting, enjoyedthe relative freedom from too much adver-tising and counted short news reportsrepeated fairly frequently as valuable. Theset owners interviewed asserted that theylistened on an average of three hours perday. They complained chiefly of the lackof good "live" programs, comedy andspecialty shows and the elaborate type ofmajor program that AM can afford. Theycomplained that the stations were on tooshort a time each day, although oneowner remarked with approval on WTPS'morning programs. One set owner con-cluded with a remark which should warmany FM station owner's heart:

"After getting used to our FM radio,"he said, "my wife and I find the otherkind seems sort of noisy and off -beat. Youfind you kind of get to expect a betterquality. I don't know exactly what it is,but if they'd give us as good stuff as theother type of radio does, we wouldn'twant to get our programs any other way."

Custom Builders(Continued from page 30)

system for WHDH in Boston, and a stand-ardized master dispatching system, bothdescribed in recent issues of the Oscillator,were constructed by the Products Division.The latter system, together with customaudio facilities consoles for WHAM inRochester, and KHJ, Mutual-Don Lee inLos Angeles, were exhibited at the Instituteof Radio Engineers Spring Convention inNew York City in March, 1947. The origi-nal consoles constructed at the beginning

February 1948 35

of this cooperative effort are those installedat WOR, New York.

It has been found possible to utilize ma-jor furniture items rather interchangeablyfor radio and motion picture projects.Basically, an audio facilities console con-sists of pedestals which house amplifierequipment on a plug-in basis. Turrets,or console sections, which may bemounted upon the pedestals, contain pan-els carrying auxiliary controls and jackfields. The pedestals are connected to-gether by a table structure which carries amixer. This table may be of nearly any de-sired length and can, of course, supportmore than one mixer housing if required.Other versions of a table can be suppliedhaving a compartment underneath the top,and at the rear, which will accommodateamplifiers or various electrical networkssuch as filters and equalizers. While someof the described components are standard-ized, great flexibility is insured, since manyvariations of structure are possible by theassembly of different basic items.

Techniques in Two IndustriesCircuit features commonly used in both

industries include the so-called split -mixer,use of inclusive volume controls controllingthe output of several individual mixer at-tenuators, and various means of introduc-ing reverberation by by-passing part of theprogram through a reverberation chamberor some type of device which simulatesreverberation.

The radio and motion picture fields havedeveloped independently, and there aremany ideas which are peculiar to each.Since the Products Division has been par-ticipating in both types of project, therehas been an increasing transfer of ideasfrom one field to the other, so that eachcustom project has had the benefit of en-gineering experience gained from the com-bined fields. As an example, equalizer orfilter designs have been developed for mo-tion picture requirements giving nearly anyconceivable variation in transmission char-acteristic. The hearing aid type of receiver,724C, has supplanted in movie soundmonitoring (when loundspeakers cannotbe used), the usual type of high qualityhead set receiver for monitoring, due to itscomfort, improvement in low frequencyresponse resulting from better coupling tothe ear, and greater exclusion of externalsounds. Such receivers might find applica-tion in the radio field for monitoring of re-mote pickups. Current transcribed radioprograms which utilize as the final tran-scription a disc which has been rerecordedfrom several originals, indicate that thetechniques developed in the motion picturefield involving rerecording processes would

undoubtedly find use when applied to suchradio problems.

Elaborate devices for the investigationand measurement of film speed variationshave been developed by movie technicians,and the speed variations (flutter) of filmdevices have been reduced to a minimum.Similar techniques could probably be ap-plied by broadcast operating people to discrecording and reproduction as used inradio. The measurement of harmonic dis-tortion from a recorded film is often lim-ited by film noise. In order to obviate thislimitation, two -frequency tests were de-vised, and if the system was non-linear theside band products could be measured bythe use of a band pass filter, eliminatingmuch of the film noise. This method iscalled an intermodulation test, and whileoriginating in the motion picture field, isnow being used in radio. Here it may beused to check distortion in audio equip-ment, and it is an excellent way to studydistortion in disc recording.

The individual performance of micro-phones used in motion picture sound re-cording must be as nearly identical in re-sponse as possible. This follows since agiven actor's voice may in the course of apicture be recorded with different micro-phones, and in the subsequent assembly ofthe film record, the sound quality mustmatch. While radio does not have at pres-ent a similar problem, its problems willmore nearly approach the motion picturefield with the coming of television. Numer-ous other examples might be cited, butthese will illustrate the point, that knowl-edge developed in one field may oftenprove useful in another.

Future CooperationWith the coming of television the radio

industry will in the future become morefamiliar with many motion picture tech-niques. While undoubtedly many programswill be televised from live action, storageof programs on film for latter transmissionwill also be necessary, due to the same fac-tors which have made transcribed soundprograms necessary. In addition, the advan-tages of preparation of suitable programs,taking the necessary time to insure goodstory and action continuity, certainly sug-gest that much regular program materialbe taken on film, and subsequently editedbefore release on the air. Since WesternElectric has been a pioneer in the motionpicture -industry it can be of considerableaid to radio, in helping to adapt motionpicture techniques to television.

The experiments and demonstrations byBell Telephone Laboratories in the field of"Stereophonic" auditory perspective arewell known. It is not perhaps as wellknown that the Products Division has spent

considerable time in the study of suchmethods of recording as applied to motionpictures. While it may be entirely too earlyto consider multi -channel transmission inradio, the quality improvement afforded bysuch transmission is great, and might wellbe considered as one of the advances ofthe future.

The cooperative efforts of the RadioDivision and the Products Division ofWestern Electric provide a wider field ofknowledge and experience which will behelpful to the broadcaster. This, coupledwith the fundamental research develop-ments of the Bell Laboratories provides ateam difficult to match. Such teamwork be-tween organizations insures the broadcastercustom built audio facilities second to none.

Power Amplifiers(Continued from page 17)

being operated Class C so that it consumespower only in proportion to the amountthe modulation exceeds the no -modulationlevel.

The constants are such that at the peakof 100% modulation, each tube is deliver-ing half of the power to the load. The sys-tem is self-adjusting to maximum efficiencyat all levels of modulation: Tube No. 1operates with the r -f plate voltage swingconstantly near maximum, whereas TubeNo. 2 operates under Class C conditions.The combination forms a high -efficiencyamplifier that divides the load at the peakof 100% modulation equally between thetwo tubes.

The beauty of the Doherty circuit is thatthe first of these actions, the variation ofthe load facing Tube No. 1, is produced bythe second action, the drawing of powerby Tube No. 2, through the medium of thenetwork connecting the output of the twotubes. As shown in Figure 1, Tube No. 2is connected directly to the output load;Tube No. 1 is connected to the loadthrough an impedance -inverting network.The action of this circuit is that as TubeNo. 2 is made to act as a generator andhence deliver power to the load, the im-pedance into which Tube No. 1 "looks" iscorrespondingly reduced.

To understand the effectiveness of thecircuit, consider first the following simpleexample showing the effect of connectinga second source of voltage in parallel withone already pushing current through aload: battery "A" is delivering current "I"into resistive load "R". If another battery"B" be connected in parallel with "A", ofidentical voltage, the current which "A"will deliver is then "y2 I" - the voltageacross "R" has not changed, but there arenow two sources of power. Thus it will

36 Westin Ekenic egOILIENIR

appear to battery "A" that the load hassuddenly doubled to "2 R" !

This principle is used in the Dohertyamplifier as follows:

(a) With two tubes in parallel work-ing into the same load, the in-crease of current through TubeNo. 2 would be an effective in-crease in the load impedance fac-ing the other tube;The simple impedance invertingnetwork has the property that thechange of impedance lookinginto one end is the inverse of thechange of impedance at the otherend, so that the net result atTube No. 1 is a decrease in im-pedance when Tube No. 2 drawscurrent.

Thus, in proportion as the modulationlevel increases, forcing Tube No. 2 to drawcurrent, the impedance presented to TubeNo. 2 is increased, and the impedance intowhich Tube No. 1 works is decreased. Theinverting network produces a 90° phaseshift, a characteristic of all such networks,so the grid drive to Tube No. 1 is made topass through a network giving a compen-sating 90 -degree shift as shown in Figure1. The signals from the two tubes are thenin phase at the load.

Simple Modulation SystemGrid -bias modulation of the power am-

plifier tubes themselves, as used in WesternElectric's 1 kw 443A-1 equipment, is ac-complished with the audio voltage from atwo stage amplifier added in series to thebias on each of the four tubes in the high -

efficiency amplifier. (In the 1 kw, "TubeNo. 1" and "Tube No. 2" are each formedby two tubes in parallel.)

Maintaining the simplicity of the design,the elements of the grid phasing networkdo double duty and are used to feed theaudio modulating voltage to the gridsof the output tubes, while maintainingthe proper d -c, audio, and r -f separationsand phase relations. The modulating sys-tem thus takes full advantage of the sim-plicity inherent in grid -modulating the finalstage of the transmitter.

As the circuit is simple in operation, itis correspondingly simple in adjustment.The number of adjustable elements in theoutput circuits of the amplifier is reducedto a minimum by combining the shunt ele-ments of the impedance inverting networkwith the shunt elements in the tuned loadsof the two tubes. The only additional ele-ment then required to form the networkis a series inductance connected betweenthe plates of Tube No. 1 and Tube No. 2.

Neutralization is adjusted in a conven-tional manner. The loads on Tube No. 1and Tube No. 2 are adjusted to the proper

(b)

PLATETRANSFORMERS

OLD 50 KWTRANSMITTER

GENERATOR

PLATETRANSFORMERS

NEW 50 KWTRANSMITTER

ROOM

HIGH VOLTAGE

RECTIFIER UNITSOLD 50 K W

TRANSMITTER

HIGH VOLTAGERECTIFIER UNITS

NEW 50 KWTRANSMITTER

STORAGE

OLD 50 KW TRANSMITTER

STAIR

CONTROL ROOM

OFFICE

BOILER

ROOM

PUMP

ROOM

WASH

ROOM

0

- 41

Main floor plan of WSB's transmitter building shows how the new 50 kw transmitter was fitted in be-side the old one, with a minimum of alteration. Dotted lines indicate partitions that were removed.

resistive and reactive values at the station'soperating frequency, using an r -f bridge,as with any high -power r -f amplifier. Theproper phase relations in the power ampli-fier are set in a simple manner with frontpanel controls. Sampling jacks are providedfor determining the phase relations at theproper points with an oscilloscope, asshown in the photographs on page 16.Other adjustments correspond closely tothose used with any high -power r -f ampli-fier to get the excitation, modulation, etc.,etc., "on the nose," with full power intothe antenna.

And when tuning and adjustment of thehigh -efficiency amplifier have been com-pleted, it is stable. The experience of themany broadcasters who have used it forperiods up to ten years is - it stays put!

WSB-Atlanta(Continued from page 27)

been matched to the original open -wireline, with a changeover switch which per-mits instant change from one transmitterto the other without tuning or other

adjustment. The old equipment can be cutback to 5 -kilowatt output in case of anyemergency reducing the power available orputting the high -voltage equipment outof operation.

Chief Engineer Daugherty surveys hiscompleted dual -transmitter installationwith satisfaction.

"The installation pleases us very much,"he says, "especially the Doherty amplifierin the transmitter, which simplified thecooling system greatly by reducing theheat load. I believe that we have the onlydual -50 -kw transmitter installation in thecountry. Our success with this installationought to throw some new light on thegeneral problems of high power trans-mitter installation and operation."

Riding with Harry Daugherty over thepine -wooded, red -clay Georgia hills, on anIndian Summer afternoon, to see the trans-mitter building and its combination ofequipments, was a wonderfully pleasantfinish to the tour of discovery of WSB.Broadcasting has its finest champions insuch stations as this tradition -strong butforward -looking Voice of the South.

February 1948 37

W. H. Doherty of Bell Telephone Laboratories atthe International Congress for the 50th Anniver-sary of Marconi's development of radio, Rome,

Italy, held from September 28 to October 5, 1947.

Hearing Aids(Continued from page 34)

and is adaptable to the needs of most per-sons who can be helped by a hearing aid.

The two new aids are housed in moldedcases made of a carefully -selected inertplastic, ethyl cellulose, that is tough anddurable and has a very low coefficient offriction that serves to reduce clothing andfrictional noises. Background noises arefurther reduced by the resilient mountingof the microphones. New colors are alsoan innovation: French gray for the 65 andtwo-tone gray for the 66. Both are alsoavailable in flesh tint.

In order to provide improved servicingfacilities, which have always been an im-portant consideration, Western Electricengineers developed two new instruments,the Servicemaster and the Gainmaster,and a visually -indexed, rapid referencecard file of simplified, easy -to -follow repairdiagrams and instructions. This new systemmakes it possible for non -technical per-sonnel, with nominal training, to quicklyand easily service all models of WesternElectric hearing aids.

The new hearing aids are available inthe United States through nearly 300 deal-ers, authorized by the distributor of otherWestern Electric commercial products-Graybar Electric Company. In Canada,these aids are distributed by NorthernElectric Co., Ltd., and in other countries byWest rex Corporation.

This Is the Life(Continued from page 21)

key relay. Must be something the matterwith power supply. Will have to be fixed.

At noon runs into the Cannery foreman,already looking for him. "How in h - - I

can ye can fish when you take all theyuice? Tell me that. This morning ye vasrunning the can shop and the can line andthe fillers and the seamers and the machineshop and a few other things and the fishelevator just to try dem out vithout anyfish in dem and then you started thatc/0#&$ vireless radio and the whole vorksstopped. 80 amps you vas drawing! Tinkof it! Yust tink of it!"

Eighty amps at 100 volts equals 8 KW!Motor -generator couldn't have possiblydrawn over 10 amps the way it was run-ning, which only equalled one kilowatt."There must be a mistake", he ventures."Mistake h - - 1," answers cannery fore-man. "Yust have a look for yourself."

New operator decides to go to bottomof matter. Goes to engine house with fore-man. Looks more closely at meter, then atvoltmeter which registers 110 volts.Strange, an 80 amp load should pullvoltage down. Looks at meter again. No-tices that pointer instead of varying slight-ly is perfectly stationary. Thought strikeshim.

"There's nothing the matter" he tellsthe foreman, "except that your old rustymeter is stuck." To prove point further,new operator pulls all the switches on theboard: the meter sticks at 80. "You'renot so smart," says the foreman with ahaughty air. "Dat &%#$* vireless radiois not on a svitch. Dat feller last year datvas here used to get sore when ye vouldpull his svitch, so he come down and fixedthe &$%* vireless radio right off theyenerator vithout a svitch." New operatortoo busy to notice the generator before, butthought strikes him it looks awfully smallfor 100 amp. generator. Goes over, scrapesoff several coats of old paint with pocket-knife, gets down to numbers on name-plate. Reads; Volts 110 Amps. 20. Showscannery foreman. "Dat don't mean a&%$#* thing. Here is vhat ye go by,"foreman says, pointing in direction of bigammeter with pointer stuck at 80. "If Iknew vhich vires vas your radio, I vouldcut dem to pieces! Ve vill see about dattoo," foreman adds, as he barges away.

Operator decides spend rest of day re-pairing gas engine. Has hard time withgovernor as parts broken and missing.Finally gets engine ready to run.

Engine starts after much coaxing. Beltwon't stay on. Takes belt to machine shopto cut piece out and make repair. Puts onbelt, starts engine again. Goes to radio

station. Closes switch. Nothing happens.Increasing "Pop -Pop -Pop -Pop -Pop-" fromengine house tells operator things not go-ing so good up there. Dashes madly toengine house. Belt wrapped around fly-wheel whirring like airplane propellor.Old engine jumping up and down like itis ready to take flying jump to moon!Operator's first impulse, get out quickbefore she leaves. Remembers operatorsupposed to stay with ship. Ignitionswitch on other side of engine. Operatorgrabs first thing handy, an old rusty axewith broken handle, throws this at igni-tion battery, knocks it off shelf. One ofwires break. Engine stops.

Operator looks at rusty mass of junk-weeps. Pulls himself together, tries again.Hunts all over place for piece of samewidth belting to repair belt. Ends up bycarving down piece of wider belt foundin machine shop. Builds framework aroundbelt so can't come off this time. Installsignition switch in radio house to forestallcatastrophe like the last. No wire. Onlyalternative string. Asks storekeeper forball of string. Storekeeper wants to knowif operator going to fly kite.

Gets new rig fixed. Works perfectly.Can pull one string if engine goes too fast,cut off ignition, pulls other string and cir-cuit closes again.

Starts engine. A flash inside set, a curlof smoke, generator groans, lights go out.Operator fears worst. Lights candle, re-pairs blown fuse, gropes way out to enginehouse. Finds no damage there. Starts upagain for lights.

Finds transmitter damage quite exten-sive. Has to disconnect all 16 wires, takeout 38 screws. Two tubes shot. Finds flash-over down inside, inaccessible withouttearing set completely apart. Seems ashame-nice new set. Decides to trace outwiring. Finds it different than blueprint.Decides to take bull by horns, start over.Tears out defective wiring, replaces withwhatever handy. Has been at cannerynearly a week-no communication yet;has the Supt and cannery foreman sore athim; nearly wrecked engine and enginehouse trying to get power. Now nice trans-mitter all shot. Weeps.

After three days gets set back together.It doesn't look the same. Has temporarywiring all over it now. Sits out at an anglelike the old one used to, so operator canwatch insides for signs of smoke whileoperating. Operator gets schedule goingwith "WXX". Rush message from homeoffice three days old.

Now decides to try and get stand-inwith Supt by giving him good service onmessage. Raises "WXX" on morningschedule but "WXX" too busy, says "Ifit's a NL hold until PM schedule." Starts

38 wormy Ekdrie Witmanilea

to explain but "WXX" is gone, workingnext station. Evening schedule operatorgets engine warmed up early, be sure allset when chance comes to clear traffic to"WXX". Waits patiently until "WXX"clears other stations, comes to him."WXX" calls, operator closes switch toanswer. Engine dies.

Up next morning hour early. Guy with"Jits" on watch and worse than ever thismorning. " Why don't you keepyour skeds called you five minutesyesterday . . . Where do you get idea youcan come on anytime . skeds are for youto keep, see . . . . here's No. 1 rush . . . .

from Seattle .. . . etc." Operator does best,with induction and the "Jits." Delivers toSupt who has answer back, also in codefor evening schedule. Operator puts inseveral hours in afternoon cleaning up en-gine, getting it to run better. Engine holdsOK on evening schedule, code messagegoes through OK.

Down in Seattle next morning one ofthe big cannery executives twerps the dialon his desk phone, and the party answers."Say," he says, "we just got a long wirefrom our Supt up in-. Says that fellowyou sent up as operator is no good. Sayshe got into trouble with the Cannery fore-man, and that he can't make the set work,says he had that new radio all apart thatyou sent up etc., etc

This is the life!

Ventilating System(Continued from page 19)

In locations where low temperatures areencountered during the winter months, theintake air should be tempered by mixingit with the hot exhaust air in a sheet metalchamber, or in a basement or storageroom. In this way the mercury vapor recti-fier tubes and quartz plate unit for fre-quency control will not be affected. Airno lower in temperature than 40° F.should be supplied to the transmitter. Inwinter some of the hot air from the trans-mitter may be utilized for auxiliary roomheating purposes by diverting air from theexhaust duct by means of a damper.

There is one additional feature of in-terest. Mercury vapor rectifier tubes aregenerally adversely affected by wide varia-tions in temperature. As mentioned in thepreceding paragraph, temperatures in theequipment below 40° F. may be avoidedby tempering the incoming air. Tempera-tures above the tube limits are avoided byemploying a small blower in the rectifierunit which is thermostatically controlled.If the air surrounding the rectifier tubesexceeds the recommended ambient tem-perature, the blower in this unit operates

and directs a small blast of air at the neckof each tube. This condenses mercury atthis point and prevents arc -backs. Thisblower also sweeps any hot air which mayhave risen to the ceiling of the cabinet andunder the shelf immediately above thepower transformers toward the amplifierwhere it is mixed with the cool air andexhausted through the main blower.

The ventilation system designed for thenew FM transmitters should give broad-casters the kind of service they have beenlooking for - low cabinet temperaturesfor minimum load on air-conditioning sys-tems, maximum life of apparatus com-ponents, freedom from movement of dustfrom the room into the cabinet, and in-creased operator comfort, which is espe-cially needed in transmitter installationswhere space is limited.

Microwaves in Harness(Continued from page 7)

oscillators. Since the output of the moni-toring receiver is proportional to fre-quency, direct comparison of the frequen-cies of the two oscillators can be made onthe screen of the oscilloscope of the pic-ture monitoring set. In practice, the twotraces representing the individual outputsof the two amplifiers in the electronicswitch are made to appearupon the screen, one trace including thewave form of the modulation taking placein the transmitting oscillator, and theother a horizontal line which moves upor down as the frequency of the calibrat-ing oscillator is raised or lowered. In thisway, the frequency excursions of the trans-mitted wave can be accurately adjustedwithin the proper limits. These observa-tions can be made continuously withoutinterrupting normal service.

March 22 - 25

Grand CentralkPalace &

Hotel Commodore

New York City

RADIO ENGINEERING

SHOW -

NdThe 1948 I.R.E. Convention will include a large ex-hibit of products available to the broadcast andcommunications industries through the Bell Labora-tories -Western Electric-Graybar team. Don't miss it!

The scopes for video monitoring andfor the frequency calibrations can be seenin the third and fifth bays in the photo-graph of the terminal equipment on page 5.

The transmitter -receiver combination inthe lower part of the third diagram in Fig-ure 1 is connected for the distortion test.In this test the transmitter and receiver fora single channel are looped as shown, andthe distortion of the whole system is meas-ured by impressing a saw -tooth wave onthe transmitter and comparing it with theoutput of the receiver on the screen of themonitoring oscilloscope.

Although the New York to Bostonproject as a whole is described as "experi-mental," the system is suitable for com-mercial use and is expected to provide re-liable and satisfactory service. In this sense,the new relay link represents the successfulharnessing of the microwaves into a sys-tem with great present utility and importantpotentialities for the future.

RILL FOR 54LE5u1rAtILE roR

TEI...V1510N, FMOR MicRo WAY MRELAY sTA-l rsi

a.Am.

By Permimion. Copyright TheNew Yorker Magazine, Inc.

February 1948 39

INDEXThe Western Electric Oscillator

Issues Nos. 1-10 inclusive September 1944 through February 1948

A ISSUE PAGE

Alexander Graham Bell Centennial March 1947 14 Fastax -A New Tool for Industry

Amplifiers Fastax at Bikini, The106A, 120B, 121A, 124A, 124E, 124F, 124G,

129A, 130A, 131A, 132A and 133A Amplifiers April 1946 30Field Engineer, TheFilter, 730A

RA -1095 Amplifier April 1946 37 FM Goes to College at U.S.C.

1126B Peak Limiting Program Amplifier April 1946 33 FM Goes to War

A New Line of Amplifiers July 1947 22 FM'ing Around the Clock

Power Amplifiers for the Modern AM Transmitter Feb. 1948 16 For the New Era in SoundProgram Peak Limiter in FM Broadcasting July 1946 25 Frequency Standard

American Telephone and Telegraph Company. Frequency Watchman, The

A. T. & T. Plans for Television"And Now We Take You to ..."

Sept.Dec.

19441945

2110

G

Building Radio Relay's Stepping Stones Jan. 1947 8 Gearing Time to Science

Microwaves in Harness Feb. 1948 3Giant Voices

Stepping Stones for Voice and Vision Dec. 1945 20 Graybar Electric Company

"And Now We Take You to ..." Dec. 1945 10 These Men Serve Broadcasting

Announcing New Reproducer Sets March 1947 30 "Triple Play -

Antennas HCan I Use an FM Antenna on My AM Tower?Clover -Leaf, TheClover -Leaf Goes Up, AClover -Leaf in the Clouds

Oct. 1946April 1946July 1946March 1947

333

1220

Headsets, 1002F and 1002HHearing AidsHigh Flying TeletypeHow Don Lee Uses the 640 Double -A

Directional Patterns with a 54A Array March 1947 7 "How We Put Radios Hilversum andMetal Lens Focuses Microwaves

Architecture of Broadcast Transmitter Buildings, TheAprilSept.

19461947

188

Luxembourg On the Air"

Atom Bomb TestsThey Witnessed the Big Explosion July 1946 43 Industrial Design, Better Products throughFastax at Bikini Oct. 1946 17 Ingenious Test Sets Broke Mica Bottleneck

Audio Facilities, Special Section April 1946 23 Introducing a New MicrophoneAviation Clears Its VoiceAviation Radio (See Radio)

April 1946 5 J

BJacks, 218A, 218J, 225CE and 410D

Bell Telephone LaboratoriesJack Mountings, 221A and 222A

Bell Telephone Laboratories at War Sept. 1944 12 K

"Triple Play" April 1946 10 Keys, 92 Type, 498A, 547A, 547B, 552A, 553ABetter Products through Industrial Design Jan. 1947 20 and 554ABrackets, 711A and 712A Supporting April 1946 34 Key Handle, KS -10011Bridges Knob, KS -10088

A Simplified Radio Frequency Bridge July 1946 36 KOMA - The Sooner State's New 50 KW VoiceNew High Frequency Bridge

Broadcasting (See Radio)Oct. 1946 30 L

Building Radio Relay's Stepping Stones Jan. 1947 8Lamp, 2 TypeLamp Caps, 2 and 72 Types

CCan I Use an FM Antenna on My AM Tower?Cavity MagnetronsClover -Leaf, TheClover -Leaf Goes Up. AClover -Leaf in the CloudsCoils

Repeating Coils, 111C, 119C, 153A, 154C.170B, 172A

Cords. P2A, P2AA and P3J

Oct. 1946July 1946April 1946July 1946March 1947

April 1946April 1946

3373

1220

3942

Lamp Sockets, 47B and 49BLifesaver for SuperfortsLiveness in BroadcastingLoudspeakers

A Loudspeaker is Born728B, 750A, 751B, 753B and 753C LoudspeakersThe 757A LoudspeakerQuality Loudspeakers for Every UseWhat Makes a Good Loudspeaker?

CrystalsM

Direct Crystal Control at 50 MC July 1946 30 Magnetrons, Cavity

Standardized Quartz Crystal Units Feb. 1948 12 Master Control Equipment

Custom Builders for Broadcasting Feb. 1948 28 Program Dispatching Made Easy

DWHDH Modernizes for Service

Determining Degree of Modulation in FMMetal Lens Focuses Microwaves

Broadcasting Sept. 1947 Meter, KS -8218

Directional Patterns with a 54A Array March 1947 MicrophonesHow Don Lee Uses the 640 Double -AIntroducing a New Microphone

Equalizer, 23A April 1946 40 Spreading the Voice of the United NationsEqualizer Panel, 279A April 1946 40 633A, 639 Type and 640AA Microphones"Experiences I Won't Forget" Dec. 1945 18 Microwaves in HarnessEyes and Ears of a Carrier Dec. 1945 9 Miniature Electron Tubes

F Mobile Radio (See Radio)

Fastax Camera "Mobile Service Operator, Please!"

"Eight Thousand Winks a Second" Dec. 1945 33 Mounting Plates, 177A, 177B, 993A, 993B and 993C

ISSUE PAGE

Oct. 1946 15Oct. 1946 17Dec. 1945 26Oct. 1946 33March 1947 8

Sept. 1944 6Feb. 1948 31

July 1947 20July 1947 18

Dec. 1945 16

July 1947 18

Dec. 1945 I

April 1946April 1946 1uu

April 1946 41Feb. 1948 34Oct. 1946 24April 1946 15

March 1947 24

Jan. 1947 20Dec. 1945 25April 1946 14

April 1946 41April 1946 41

April 1946 42April 1946 42April 1946 42Jan. 1947 12

April 1946 42April 1946 42April 1946 42Dec. 1945 30Jan. 1947 3

July 1946 35April 1946 35March 1947 16July 1947 6July 1947 11

July 1946 7

Jan. 1947 22March 1947 26April 1946 18April 1946 38

April 1946 15

April 1946 14

April 1946 43April 1946 36Feb. 1948 3

March 1947 17

March 1947 4

April 1946 41

40Western Electric =031

ISSUE PAGE ISSUE PAGE

Music on the Menu Oct. 1946 19 WHDH Modernizes for Service March 1947 26Music Reproducing Systems (See Sound Systems) "WHN Does It Again ... in FM" Oct. 1946 8Music While You Ride March 1947 22 WINK-FM-First Station to Erect a Clover -Leaf Oct. 1946 31

N WLAW-A New Top -Power Voice fromNational Association of Broadcasters Oct. 1946 4 New England July 1947 14Navy Radar Puts on Civvies July 1946 28 WSB-A Dixie Institution Feb. 1948 24New Arc -Back Indicator March 1947 12 WTPS-FM, New Orleans Feb. 1948 8New "Free Field" Acoustic Test Room Mobile

at Bell Laboratories July 1947 39 FM Goes to War Sept. 1944 6New Order Wire Panel for Broadcasters Feb. 1948 32 "Mobile Service Operator, Please!" March 1947 4New Ventilating System Adds Reliability to Technical Details of SCR -508 and 608 Sept. 1944 7

FM Transmitters Feb. 1948 18 Telephone on Wheels July 1946 3

Notes on Modulation of AM Transmitters Oct. 1946 22 Railroad0 Radio Rides the Rails July 1946 32

Order Wire Panel for Broadcasters Feb. 1948 32 Rectifiers, 18A, 18B, 20B and KS -7593 April 1946 38Repeating Coil and Equalizer Assembly April 1946 34

Panels Repeating Coils (See Coils)Blank Panels April 1946 41 Reproducer, 9 Type April 1946 54271A Output Switching Panel April 1946 39 Reproducer Arm, 5A April 1946 34279A Equalizer Panel April 1946 40 Reproducing Group, 109 Type April 1946 33288A Terminal Panel April 1946 41 Reproducer Sets, 1304A and B March 1947 30296A and 296B Panels April 1946 41

PICAO - Key to the Future of Air Transportation Jan. 1947 10 "Seeing Is Hearing" April 1946 21

Plugs, 47A, 47B, 241A and 241B April 1946 42 Sound SystemsPower Amplifiers for the Modern AM Transmitter Feb. 1948 16 Giant Voices Dec. 1945 14

Power Unit, 12A April 1946 39 Music on the Menu Oct. 1946 19Production Line for FM Transmitters Feb. 1948 22 Music While You Ride March 1947 22

Program Dispatching Made Easy Jan. 1947 22 Putting Sound to Work April 1946 17

"Protected Networks" --A New Technique in Something New in Wire Program Distribution July 1946 15

Hearing Aids Feb. 1948 34 Sound Reproduction Comes of Age July 1947 3

Public Address (See Sound Systems) Stereophonic Sound Reinforcement July 1946 ItPutting Sound to Work April 1946 17 There's Music on the Beach at Waikiki Sept. 1947 6

QQuality Loudspeakers for Every Use July 1947 6

Speech Input Booklet, NewSpeech Input Consoles

Dec. 1945 33

Custom Built Studio Control Desk April 1946 24Radar Tailor -Made Console Gives Modern Program

Eyes and Ears of a Carrier Dec. 1945 9 Control Oct. 1946 39Navy Radar Puts on Civvies July 1946 28 22D Speech Input Equipment April 1946 29Radar -A Production Triumph Dec. 1945 6 23C Speech Input Equipment April 1946 28TWA Looks at Radar Oct. 1946 36 25B Speech Input Equipment April 1946 26

Radio 25B Consoles on the Job July 1947 28General Standardized Quartz Crystal Units Feb. 1948 12

Building Radio Relay's Stepping Stones Jan. 1947 8 Stepping Stones for Voice and Vision Dec. 1945 20FM Goes to War Sept. 1944 6 Stereophonic Sound Reinforcement July 1946 11Metal Lens Focuses Microwaves April 1946 18Microwaves in Harness Feb. 1948 3 Telephone on Wheels T July 1946 3Radio Fights its First War Sept. 1944 3 Teletype, High Flying Oct. 1946 24Radio Shops Move to North Carolina Oct. 1946 27 Television, A. T. & T. Plans for Sept 1944 21Stepping Stones for Voice and Vision Dec. 1945 20 Testing Equipment and FacilitiesWar Radio Equipment in Color Photographs Sept. 1944 17 Ingenious Test Sets Broke Mica Bottleneck Dec. 1945 25You Can't Win a War Without Radio Sept. 1944 15 New "Free Field" Acoustic Test Room

Aviation at Bell Telephone Laboratories July 1947 39Aviation Clears Its Voice April 1946 5 Torture Chambers-Modern Style Dec. 1945 43High Flying Teletype Oct. 1946 24 There's Music on the Beach at Waikiki Sept. 1947 6Lifesaver for Superforts Dec. 1945 30 Thermistors Dec. 1945 3PICAO - Key to the Future of Air These Stations-On the Air-Show March

Transportation Jan. 1947 10 of FM Jan. 1947 16Broadcasting These Men Serve Broadcasting April 1946 12

"And Now We Take You to ..." Dec. 1945 10 They Witnessed the Big Explosion July 1946 43Announcing New FM Transmitters July 1946 18 This is the Life Feb. 1948 20Architecture of Broadcast Transmitter Buildings Sept. 1947 8 Torture Chambers-Modern Style Dec. 1945 43Can I Use an FM Antenna on My AM Tower? Oct. 1946 33 Transformers, 18A and 19A Auto April 1946 40Determining Degree of Modulation in FM Transmitter Buildings, Architecture of Sept. 1947 8

Broadcasting Sept. 1947 3 TransmittersFM'ing Around the Clock Feb. 1948 31 Announcing New FM Transmitters July 1946 18How Don Lee Uses the 640 Double -A April 1946 15 First FM Transview Goes on the Air Jan. 1947 31"How We Put Radios Hilversum and Notes on Modulation of AM Transmitters Oct. 1946 22

Luxembourg on the Air" March 1947 24 New Ventilating System Adds ReliabilityKOMA-The Sooner State's New 50 KW Voice Jan. 1947 12 to FM Transmitters, A Feb. 1948 18Lifesaver for Superforts Dec. 1945 30 Power Amplifiers for the Modern AM Transmitter Feb. 1948 16Liveness in Broadcasting Jan. 1947 3 Production Line for FM Transmitters Feb. 1948 22National Association of Broadcasters Oct. 1946 4 RF Wattmeter and Impedance Monitor for**Radio Broadcasting -A Trust for the FM Broadcasting, An July 1947 25

American People" Oct. 1946 3 These Stations-On the Air-Show March of FM Jan. 1947 16RF Wattmeter and Impedance Monitor Two Western Electric FM Tens Go on the Air

for FM Broadcasting, An July 1947 25 in New York Feb. 1948 14These Men Serve Broadcasting April 1946 12 Typical Low and Medium Power AM Installations April 1946 8These Stations-On the Air-Show March Western Electric AM and FM Transmitters Sept. 1947 62

of FM Jan. 1947 16 "Triple Play" April 1946 10Use of Program Peak Limiter in FM Broadcasting July 1946 25 TWA Looks at Radar Oct. 1946 36

February 1948 41

U ISSUE PAGE ISSUE PAGE

Use of a Program Peak Limiter in FM Broadcasting July 1946 25 "Triple Play" April 1946 10

What Makes a Good Loudspeaker? July 1947 11V WGHF-101.9 me Feb. 1948 14

Vacuum Tubes WHDH Modernizes for Service March 1947 26Miniature Electron Tubes March 1947 17 "WHN Does It Again . .. in FM" Oct. 1946 8New Traveling Wave Tube Oct. 1946 35 WINX-FM-First Station to Erect a Clover -Leaf Oct. 1946 315541 Vacuum Tube, The Oct. 1946 14 Wire Program Systems (See Sound Systems)45,000 -Hour Tube at WRVA April 1946 21 WMGM-99.3 me Feb. 1948 15

Volume Indicators, 754A and 754B April 1946 38 WLAW-A New Top -Power Voice from

W New England July 1947 14

Western Electric CompanyRadio Shops Move to North Carolina

WSB-A Dixie InstitutionWTPS-FM, New Orleans

Oct. 1946 27

Feb. 1948Feb. 1948

248

Seventy -Five Years of Pioneering byWestern Electric

YSept. 1944 10

These Men Serve Broadcasting April 1946 12 You Can't Win a War Without Radio Sept. 1944 15

AUTHORSAugustadt, H. W. A New Line of Amplifiers July 1947 22

Ayres, R. C. and Davidson, R. M. TWA Looks at Radar Oct. 1946 36

Black, W. L. Use of a Program Peak Limiter in FM Broadcasting July 1946 25

Bohren, Arnold K. A Clover -Leaf Goes Up July 1946 13

A New Ventilating System Adds Reliability to FM Transmitters Feb. 1948 18

Bright, Robert, Jr. and Vanderbilt, Stanton Telephone on Wheels July 1946 3

Colledge, A. W. Stereophonic Sound Reinforcement July 1946 11

Gearing Time to Science July 1947 18

Davidson, R. M. and Ayres, R. C. TWA Looks at Radar Oct. 1946 36

DeMare, George Radio Fights Its First War Sept. 1944 3

"And Now We Take You to ..." Dec. 1945 10

"WHN Does It Again . . . in FM" Oct. 1946 8

KOMA - The Sooner States New 50 KW Voice Jan. 1947 12

WLAW-A New Top -Power Voice from New England July 1947 14

WTPS-FM, New Orleans Feb. 1948 8

DeMare, George and Pierce, R. Morris "Experiences I Won't Forget" Dec. 1945 18

Doherty, W. H. Notes on Modulation of AM Transmitters Oct. 1946 22

Donaldson, Carson and Sener, William H. FM Goes to College at U.S.C. March 1947 8

Drenner, Don V. R. "How We Put Radios Hilversum and Luxembourg on the Air" March 1947 24

Dreyfuss, Henry Better Products through Industrial Design Jan. 1947 20

Hall, E. M. Sound Reproduction Comes of Age July 1947 3

Heffron, E. J. National Association of Broadcasters Oct. 1946 4

Hilliard, J. V. FM Goes to War Sept. 1944 6

Hopper, F. L. Custom Builders for Broadcasting Feb. 1948 28

Johnson, J. A. This Is the Life Feb. 1948 20

Johnson, J. Clifford Cavity Magnetrons July 1946 7

Kennedy, Frank M. How Don Lee Uses the 640 Double -A April 1946 15

Kock, Winston E. Metal Lens Focuses Microwaves April 1946 18

Lanier, R. S. What Makes a Good Loudspeaker? July 1947 11

Building the Home for Your Broadcast Transmitter Sept. 1947 12

WSB-A Dixie Institution Feb. 1948 24

Lindsay, R. H. The Frequency Watchman Dec. 1945 16

Maass, Charles E. Navy Radar Puts on Civvies July 1946 28

Maxfield, J. P. Liveness In Broadcasting Jan. 1947 3

McMullen, F. C. PICAO -- Key to the Future of Air Transportation Jan. 1947 10

Miller, Justin "Radio Broadcasting -A Trust for the American People" Oct. 1946 3

Nickel, Frank Music While You Ride March 1947 22

Quality Loudspeakers for Every Use July 1947 6

Olmstead, N. C. New Arc -Back Indicator March 1947 12

Parker, Harry L. WHDH Modernizes for Service March 1947 26

Pierce, R. Morris and DeMare, George "Experiences 1 Won't Forget" Dec. 1945 18

Ragsdale, John W. Types of Broadcast Transmitter Buildings Sept. 1947 18

Scarr, H. F. Program Dispatching Made Easy Jan. 1947 22

Selover, E. E. Standardized Quartz Crystal Units Feb. 1948 12

Sener, William H. and Donaldson, Carson FM Goes to College at U.S.C. March 1947 8

Snow, C. E. The 5541 Vacuum Tube Oct. 1946 14

Sturges, Hollister, Jr. The Field Engineer Dec. 1945 26

Taylor, S. P. A Cooperative Enterprise for Broadcasting Sept. 1947 10

Thurston, George M. Direct Crystal Control at 50 MC July 1946 30

Tiffany, J. M. A Simplified Radio Frequency Bridge July 1946 36

Tweeddale, J. E. Thermistors Dec. 1945 3

Tyack, L. C. The Clover -Leaf April 1946 3

Vanderbilt, Stanton and Bright, Robert, Jr. Telephone on Wheels July 1946 3

Vanderlippe, R. A. High Flying Teletype Oct. 1946 24

Waddell, John The Fastax at Bikini Oct. 1946 17

Willets, H. N. "Mobile Service Operator, Please!" March 1947 4

Whaley, H. R. New High Frequency Bridge Oct. 1946 30Directional Patterns with 54A Array March 1947 7

Determining Degree of Modulation in FM Broadcasting Sept. 1947 3

Younker, E. L. An RF Wattmeter and Impedance Monitor for FM Broadcasting July 1947 25

42 Wailers, E'lec'tric (1)=2,Ern

F. L. Hopper Arnold K. Bohm+

CONTRIBUTORS TO THIS ISSUEF. L. HOPPER, author of Custom Buildersfor Broadcasting (page 28), was graduatedfrom the California Institute of Technol-ogy in 1922 with a B.S. in physics and en-gineering. He joined the Bell System aftergraduation, in the office of the Chief En-gineer of the Pacific Telephone and Tele-graph Company.

In 1929 he transferred to Electrical Re-search Products, Incorporated, where he hasbeen engaged with the design of film soundrecording equipment. During the war heworked on a research project under theauspices of the Office of Scientific Researchand Development.

In 1945 he began work in conjunctionwith the Radio Division of Western Elec-tric in the design and development of cus-tom built audio facilities for broadcast ap-plications. Mr. Hopper is a member of theI.R.E., the Society of Motion Picture En-gineers, and the Acoustical Society ofAmerica.

ARNOLD K. BOHREN, author of A Neu'Ventilating System Adds Reliability to FMTransmitters (page 18), was graduatedfrom Oregon State College in 1930 witha B.S. in Mechanical Engineering. Hejoined the Bell Telephone Laboratories in1930 and for four years was engaged inthe mechanical design of panel dial centraloffice equipment. In 1934 he was trans-ferred to the Commercial Products Devel-opment Department where he designedradio communication transmitters and re-ceivers for marine, police and aircraft ser-vices. During the war he designed the FMcommunication set for armored vehicles,and supervised a group working on themechanical design of Navy radar equip-ments. He is now in charge of the designof transmitters and antennas for broadcast-ing. He is the author of A Clover -LeafGoes Up, in the Oscillator, July 1946.

Mr. Bohren is a Senior Member of theI.R.E. and a member of Tau Beta Pi,

J. A. Johnson

Sigma Tau, and Phi Kappa Phi, nationalhonorary societies.

J. A. JOHNSON, author of This is theLife (page 20), studied electrical en-gineering at the University of Washingtonfrom 1924 to 1928. During college vaca-tions he made several trips to Alaska asradio operator, his first one in 1924, whenhe installed a spark transmitter at Kenai.Since then he has made 21 trips to Alaska.This is the Life was written after his re-turn from Alaska in the fall of 1927.

E. E. SELOVER, author of StandardizedQuartz Crystal Units (page 12), joinedthe Western Electric Radio Division in1944 as a Government Contract Specialiston special purpose vacuum tubes, aftereleven years in the Commercial and Gen-eral Sales Departments of the New YorkTelephone Company. He is now SalesSpecialist for Quartz Crystal Units in theWestern Electric Radio Division.

E. E. Selover

February 1948 43