JUN1935

ConstantFrequency

Monitor

CalculatingResistorCapacity

AssignmentsNews, Reviews

"Wrinkles"

IIP

Newuipment

...at Lausanne

Slip, Air,Broadcast

olice

A MONTHLY JOURNAL DEVOTED TO THE COMMERCIAL RADIO & ALLIED FIELD

)1's also aIiimameatRCA RADIOTRONSAt Radio City ... entertainment crossroadsof the nc ion . . . monument to radio ex-cellence ... hub of ihe National Broadcast-ing Company . . . there are hundreds ofradio tubes: tubes big and little, receivingand transmitting, whose glowing cathodes

represent the vital spar'< of life at the verynerve center of a great radio system.

These tubes are RCA Radiotrons. Their unfailing performanceis perhaps as great a testimonial to the name "RCA Radio-tron" as the towering magnificence of Radio City is to the ad-vancement of radio broadcasting. Whether for communicationsor entertainment RCA Radiotrons are the choice of those whoknow-the standard by which all other radio tubes cre judged.

RCA RADIOTRONSRCA Manufacturing Company, Inc.

New JerseyNEW YORK 1270 Sixth Ave.CHICAGO 111 N. Canal StreetATLANTA 144 Walton Street, N.. W.DALLAS Santa Fe BuildingSAN FRANCISCO, 235 Montgomery Street

Mention Cons ineirelat Rattio-n:hen n"le, ring Adrentis7mi.ei,

PUBLICATION OFFICENEW YORK

7 West 44th StreetPhone: VAnderbilt 3-8091

VOLUME IV NO. 8

JAMES J. DELANEY,Editor

BERNARD EPHRAIMTechnical Editor

L. D. McGEADY,Business Manager

Associate Editors:BALTIMORE, MD.

Wm. D. Kelly, WFBRBOSTON, MASS.

Harry R. ChethamSomerville, Mass., Police RadioCROWN POINT, IND.

Fred F. HallST. LOUIS, MO.

C. H. Stoup, WIL

TELEVISION keeps threateninglybobbing its head, but regardless of

the speed of development, it will not beahead of the public demand or anticipa-tion.

The recent intimations to RCA stockholders at their meeting by David Sar-noff, and other public announcements bythe same author are the official words ofthat corporation's continued efforts inthe direction of television.

Later announcement is that startingApril 1st next year the American Tele-phone & Telegraph will have placed andbe ready for experimentation of theirnew "coaxial" cable between Philadel-phia and New York which is the hope forthe 1,000,000 cycle frequency line transmission required for distance transmis-sion of television. This will be the firstlong distance actual test for the linetransmission that will answer the dis-tribution problems of television.

England, Germany, Japan, and evenhere in the United States some transmis-sion of disc scanning principle of tele-vision is "on the air" everyday. At theCamden RCA -Victor works Zworykin andhis staff are continuing their efforts. Atthe West Coast offices and the PhilcoPhiladelphia plant Farnsworth and hisstaff are each day recording some slightadvances.

It is such an extensive study that lit-tle can he accomplished by small individ-ual experimenters for want of funds,but an actual fact if it were not forthis the public would be kept better in-formed of the day to day progress. Itdoes appear a "large shop" proposition.

(FORMERLY "C -Q")The Only Magazine in America Devoted Entirely to the Commercial Radio Man

Contents for June, 1935

Page

General View of Control Room KYW, Philadelphia Front Cover

A Constant Frequency Monitor That Stays Put 5

By Roy H. McConnell

Electron Mechanics of the Cathode Ray TubeBy Bernard Ephraim

"In Baltimore "By Wm. D. Kelly

Electron Mechanics of the Cathode Ray Tube

By Bernard Ephraim

Variable Condenser Breakdown VoltagesBy Raymond L. Moorehouse

Methods of Calculating the Current Carrying Capacity

of Resistors

New A. C. Mains Operated Speech Input Equipment atLausanne

By Dipl. Ing. E. Metzler and R. W. Hardisty

Actions of the Federal Communications Commission

Assignments

.A Couple of "Kinks" from KBTM

By H. L. Kimsey

New Apparatus

7

6

7

10

11

14

18

19

27

29

Published Monthly by CQ Magazine Company, I West 44th Street. New York.N. Y., Phone VAnderbilt 34091. Yearly subscription rate $2.00 in U. S. and Canada;$2.60 foreign. Make all checks, drafts and money orders. pa.7.-abte to the Company.Single Copies, 20 cents. Text and illustration of this Magazine are copyrighted, andmust not be reproduced without permission.

Ghirardi'sRADIOPHYSICS COURSE

The most popular basic text on ra-dio in existence, used by students,schools, teehnicians and experimenterm the world over. Everythingfrom fundamental electrical theoryright up to the latest applicationsand developments. Clear. concise,complete, up-to-date, written in lan-guage easy to understand, withover 500 diagrams and Illustrations.Invaluable for broadcast techniciansfor rounding out their radio back-ground. You need this great I kin your work. (972 pages, 44.00 post-paid.)

RADIO OPERATINGQUESTIONS AND

ANSWERS

Nilson & HornungThis book gives over 600 questionsand answers covering all radio op-erator license examinations. Ques-tions are typical of those used onexaminations; answers are fulland well illustrated. This editionhas been enlarged to include infor-mation on broadcasting, marine,aeronautical, police and amateur ra-dio operating and contains manynew questions and answers on newtransmitters, new radio laws andlicense regulations, etc.

5th edition388 pages, 5%x8, 96 illustrations

$2.50

R ADIOTRANSMISSION

Practical Radio Communication, Nilson & Hornung $5.00How to Pass U. S. Govt.. License Examinations,

Duncan & Drew (1932) 2.00Radio Traffic Manual and Operating Regulations

(19291 2.011Radio Operating Questions and Answers, Nilson &

Hornung 2.50Practical Radio Telegraphy, Nilson & Hornung 3.00Principles of Wireless Telegraphy, George W. Pierce 1.00Principles of Radio Communication, J. H. Moreeroft 7.50

GENERAL

Principles of Radio, Keith IlenneyElements of Radio Communication, J. H.Radio Engineering Handbook, Keith HenRadio Engineering, 10, E. TermiteRadio Engineering Principles, Lauer &Hndlo Handl k, Moyer & M ()sire!Radio Telegraphy and Telephony, Duncan

SERVICE

$3.50Morecroft 9.00

ney 5.005.00

Brown 1.505 00

& Drew 7.50

Perpetual Trouble Shooters Manual, J. F. Rider, Vols.I, II, III, IV, V. each $7.60

Radio Construction and Repairing, Moyer & Wostrel 2.50

t. E.\ AL

THEORY

Radio Frequency Electrical Measurements, H. A.Brown $4.00

Electric Oscillations and Electric Waves, G. W.Pierce 6.00

ACUUM TUBES

Electron Tubes and Their Application, J. H.Moreesoft $1.50

Theory of Thermionie Vacuum Tubes, E. L. Chaffee 6.00Theory of Thermionle Vacuum Tube Circuits, L. J.

Peters 3.00Radio Receiving Tubes, Moyer & Wostrel 2.50

TELEVISION

Photocells & Their Application. Zworykin & Wilson $2.50Practical Radio -Including Television, Moyer &

Wostrel 2.50Television -Its Methods and Uses, E. J. Felix 2.50

SOUND

Recording Sound for Motion Picture Reproduction,L. Cowan 45.00

Projecting Sound Pictures, A. Nadel) 2.50

ELECTRICALstandard Handbook for Electrical EngineersHandbook for Electrical Engineers (Penders)Read) Reference Tables, C. HeringElements of Electricity for Tech, Students, W.

TimbleThe Elements of Electricity, W. Robinson

ADVANCED THEORY

47.1107.002.50

11.

3.501.1111

General Lectures on Electrical Engineering, C. P.Steinmetz 43.00

Theory and Calculation of Electric Circuits, C. P.Steinmetz 4.011

Theory Elements Of Electric Engineering, C. P.Steinmetz 4.00

TELEPHONY andommunication Engineering, W, L. Everitt 25.00

Handbook of Telephone Circuit Diagrams, J. M. Heath 2.50Principles of the Telephone, Jansky & Faber 1.50

RECTIFICATIONMercury Arc Rectifiers, Marti & WinogradElectric Rectifiers & Valves, I. R. Runtherschulze

TESTING

$6.004.110

I Irnieni tr VI...trice' Testing. V. Karapetoff $.50I teetrleal M. ashirements and Tooting, C. L. Dawes .75

MOTORS

%ma lure Winding and Motor Repair, D. H. BraymerRewinding Small Motors, Braymer & Roetit -mating Current Armature Winding, T. CroftCommercial Dynamo Design, W. I,. Waters

TELEGRAPHY3utomatic Telephony, Snutth and Campbell%IiirrIenn Telegraph Practice, D. McNicol

*3.002.5113 .1 in2.90

$3.005.00

Send Check or Money Order Only. Do Not Send Cash

Commercial Radio, Book Dept.West 44th Street

NEW YORK, N. Y.

Page Four Mention Commercial Radio when answering Advertisements

A Constant Frequency Monitor That Stays Put

WE about fourteen months ago de-signed and built a constant frequen-

cy motor which I believe will be of inter-est to anyone interested in the buildingof a frequency motor that is really ac-curate. The circuit diagram is shown inFigure 1, with which also is given dataregarding parts used in construction ofthe unit. The monitor has been tested forlong periods of time in direct comparisonwith a constant frequency monitor whichis a commercial product which was ap-proved by the Bureau of Standards forthe Federal Radio Commission. We havefound the monitor to be just as accurateas the commercial job. It will measurebeats as low as one per second which Ibelieve you will agree is getting downpretty fine. The photos give completedata for the construction of the frameand dimensions of the temperature cham-ber, inner oven or rather heat attenua-ting box which holds the crystal and lo-cations of the heaters.

Fig. 1. is the diagram of the monitor.The value of the various parts are givenin the drawing.

a.l. is an 0-15 Millammeter

a. is an 0-1% Millammeter.

X. Filament leads all connect to the2% volt transformer mounted on the lefthand side of the monitor frame. A 30ohm resistor is shunted across the 2%volt leads with the center tap grounded.

The screen grid voltage is 65, the platevoltage 120.

The oscillator and detector coils weresalvaged from an Atwater Kent model20 radio. The secondary was removedfrom the oscillator coil. The detector coilwas not changed in any way.

I would advise strict adherence to thespecifications of the various parts of the

monitor if you want to be sure of havinga job that will function as it shouldwithout any monkey business and somerebuilding. We spent considerable timeand effort before arriving at a designthat was satisfactory. This is particular-ly necessary regarding the temperature

JUNE, 1935

By ROY H. McCONNELL

oven. We built several before we hit ona combination that worked and reallystayed put. To start with we imaginedthat all that was necessary to have anaccurate temperature oven was to build awell insulated box and put a good heat-er unit in it and a mercury thermostat.Well it didn't work out that way, we had

j,Qbemelt F creitel M 0 k 'tenSC + 8+

equivalent of six inches of wood insula-tion in our first oven and used fourOhmspun heater units and an Ainsco mer-cury thermostat, and lo and behold, theblamed thing would vary as much as twodegrees centigrade, this was discouragingto say the least, and we immediately be-gan to have more respect for the menwho designed and built the frequencymonitors which received approval of theFederal Radio Commision. Then as oneof our Bohemian friends says "what todo is the next thing." Well we got ourheads together and had a conference,with the results that we built a new tem-perature oven much smaller than thefirst, put the heater units just two ofthem on each side of the inner crystaloven and put the thermoregulator in aholder fastened against the inner ovenand between the heating unit, this didthe job beautifully. The heat stays oilabout 45 seconds and off 75 and the tem-

perature is so even that we cannot detectany change on the thermometer. Thattook care of the heat problem.

Fig. 2 is a diagram of the heat con-trol unit. The resistor across the fila-ments is a 30 ohm center tapped.

C-2. are 300 volt I. MFD Condensers.The choke is the prilary of an old

trickle charger.The 2-45 tubes are used in parallel.The condenser across the relay con-

tacts may be anything from 1/10 to 1/4

MFD.

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0

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The circuit is given in Fig. 2 for theheat control unit. It is the most satis-factory unit of this kind we have everhad anything to do with and we haveused several kinds. It is simple and easily constructed and has given us uninter-rupted service for over eighteen monthswith no trouble at all. We are now usingthree of these units and like them fine.

Fig. 3. is the circuit for the powerpack for the monitor. There is nothingunusual about it and as you will notethe voltage is rather low but seems tomake for stability and gives us plentyof power. The crystal used is an X Cutoperating at 46 degrees centigrade. Thebolder is a standard holder with no ten-sion on the top plate. As you will noticein the photos the monitor is completelyshielded and we are showing in the photohow the leads are brought from the tem-

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170 1

tc

perature oven to the crystal stage. Inoperation the monitor is very stable andhas no body capacity effect. I feel surethat any one building a monitor of thistype will be highly pleased with the re-sults it will give. Ours is giving ussplendid service and satisfaction.

Page Five

Upper left-The photo shows the construction of the temperature oven. Theinner and outer boxes are made of 16 gauge galvanized steel with an inch of celo-tex between them for insulation. The photo shows how the celotex is put in. Thecover of the box fits inside the front of the oven and is bolted to the steel coverwith stove bolts. The dimensions of the oven are, height 10 inches, width 8 inches,depth 7 inches. These are inside measurements. The heat attenuation box is madeof aluminum and is 41/4 inches outside diameter. It is made from a standard6 inch aluminum box which we cut down to 4% inches, and is lined with Vsinch cedar wood. The copper box above the heat attenuating chamber containsthe oscillator coil and tuning condenser for same, its dimensions are 3 x 3 x 6.

The heaters are standard Ohms pun drawing 1/4 amper, of which two areused, mounted one on each side of the heat attenuating chamber as shown in thephoto. The .Amsco mercury thermostat is mounted between the heater unit andthe heat attenuator. The device shown under the heat attenuating box is a by -metallic thermostat and is installed as a safety precaution; it is set at aboutthree degrees higher than the mercury thermostat and will open in case anythingshould go wrong with the relay in the mercury thermostat circuit and ill shouldfail to function. In other words it is a safety valve. This was installed becauseof a sad experience we had with a commercial oven in which the relay stuck andburned up the lay out and just about ruined everything in it. The oscillator coiwas taken out of an Atwater Kent model 20 receiver and is tuned by a Ham-marlund 14 plate midget condenser, capacity 100 Mini.

Upper right-This photo shows the monitor back view with the cover on theheater oven. The frame is made of 3/4 inch angle iron and is 21 inches high,18 inches wide, and is 12 inches deep at the base. It is of welded construction. Thephoto shows the details of same. The method of bringing the leads from the crys-tal and oscillator inductance are clearly shown in the photo. The tubing carryingthe wires is 1/4 inch copper and the cover on side of the heater oven is also cop-per. The connections are under the cover and are soldered and taped. The chassispan upon which the apparatus is mounted is 131/2 x 7 x 2 inches, the sides be-ing copper and the top and bottom electralloy. The leads to the B -Supply areshown on the left hand side of the chassis pan. The leads to the heat control unitare shown on the bottom right hand side of the heater oven.

Lower left-This photo shows the front of the monitor. The panels are 7 x 18electralloy. The left hand meter is an 0 to 15 millammeter, the center meter an 0to 11/2 millammeter; the control on the right controls the signal input to thedetector circuit in the upper right hand corner is the binding post to which theantenna is connected. We use about 10 feet of wire stretched across the back ofthe transmitter room. The thermometer is shown in the center upper part of thelower panel; have always intended to get an angle thermometer but have neverdone it yet.

Lower center-Thin is a photo of the heat control unit used on the monitor.It was constructed entirely from the junk box with the exception of the relay/and tubes. The filament transformer came from a defunct midget set, the chokeis the primary of a trickle charger that had long since become obsolete. The bind-ing posts were once part of a Willard B Supply.

Lower right-This is another back view of the monitor. On the lower lefthand side is shown the filament heating transformer which furnishes the filament

Page Biz

"IN BALTIMORE"By WM. D. KELLY, WFBR

WPFH is the Police Radio in Balti-more. The main xmtr is a RCA UT 4199and is operating on 2414 ke with a 1/4wave T type antenna.

There are 44 cars and one police boatwith a receiver.

The following members constitute thestaff:

Chief -Lt. Wm. E. TaylorCharles E. A. Linn, OperatorGeorge J. Haslup, OperatorJoseph J. Recker, OperatorErnest E. Oliphant (Service & Relief)Sgt. Ferdinand I. Kammer (Relief

Op)John Quincy Adams (Service & Re -F. Russell Dunlap (Service & Relief)Karl Zeuch (Dispatcher & Relief)The Aux xmtr was built in the radio

shop of Lt. Taylor from frame up. Thisaux is giving as good avc as the mainxmtr.

At WCAO there's talk of a new trans-mitter, but no matter what all the trans-mitter salesmen say, the Chief EngineerJimmy Schultz says they haven't boughtone yet. However, Jimmy is buildingsome new studio and master controlmixers.

And, between times, Jimmy Schultz isworking on his ham station. He is put-ting in a lot of new stuff in that xmtrand says that it will be on the air soon.

Jones at WCAO has a net profit of.50c on this chain letter business. Jonesand Lynch are running a ham stationbetween them and claim good dx on 20meter phone.

Basford (WCAO) is trying to getenuf do re me from the Mrs. to in-crease his xmtr output. Well -

Doors at WFBR. one of the, boys,Clem Holloway, stepped off the end ofthe dock and went and got married theother day.

Paul Ruckert, WFBR control, has beenlooking over all kinds of maps and dopeabout good vacation places.

Wm. Q. Ranft, WFBR'c chief, is sport-ing a new Chevrolet.

George Porter Houston, chief WCBM,is still talking about having to getup 1 A. M. to make a frequency run onthe "Intercity" network. (Old ABC)

Snyder, WCBM control room, hasworn hole in the rug keeping time to themusic with his foot.

Ed Laker is still in the "Sound Re -enforcing" biz.

K ries has just put W3DYN on theair and reports dx using an inside an-tenna.

Craig Brown is in Baltimore on hisvacation and honeymoon. Craig spendsmost of his time in South America withthe Pan American Grace Airways. Allthe gang wishes him "Happy Landings".

current for the tubes. Between the tworight hand tube shields can be seen theknob which controls the output from thecrystal oscillator. A good view of theOhynspun heater units and the crystal andholder is shown. The detector coil is acoil taken from an Atwater Kent model20 receivers just as it is. It is mountedback of the two center tube shields andshielded with a copper can size 31/4 x 31/4x 31/2.

COMMERCIAL RADIO

Electron Mechanics Of The Cathode Ray Tube

THE growing popularity that has beengiven to the cathode-ray tube, since

the advent of television, can be attribu-ted to the remarkable advances of tech-nical applied science research. The vast

fr

By BERNARD EPHRAIM

which is characteristic of air, and if an-other gas were substituted, a differentcolor would, in general, be obtained.

The successive changes in the appear-ance of the phenomena when the elee-

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amount of engineering and the exhaus-tive efforts investigators have given tothe study would take volumes to record.In this short discourse, it is the pur-pose to clarify some of the more impor-tant phenomena that have heretoforebeen slightly confusing to the experimen-talist.

In 1869, the electrical research work-er, Hittorf, discovered the phenomenonnow known as cathode rays whilst con-ducting experiments pertaining to theconduction of electricity through highlyrarefied gases: It is of scientific inter-est to note the successive changes inphenomenon leading up to a cathode-raydischarge.

Cathode-ray Discharge in a Gas FilledTube

Ocular evidence of an elementary na-ture concerning cathode rays has itsgenesis in the lowly spark -gap, one timeused as part of the apparatus necessaryfor radio transmission. This visual phe-nomena is seen in the form of an elec-trical discharge bridging the interven-ing gap of the electrodes when the dif-ference in applied potential has beensufficiently raised. The size and shapeof the electrodes together with their dis-tance of separation are the main fac-tors determining the potential applied tothe gap to insure discharge. The sparkoccurs in a series of mauve colored flame

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JUNE, 1935

trodes are placed inside of a glass tube,which is slowly being evacuated, leadsup to what is known as a cathode-raydischarge. At low vacuum, the first visi-

cathode of the tube, which space gradu-ally extends toward the anode; alsothere appears a Narrow greyish regionvery close to the cathode. With furtherexhaustion this greyish region movesaway from the cathode leaving a seconddark space, and on the surface of thecathode a blue luminous layer now ap-pears. This surface is called the cath-ode layer. Referring to Figure 1, thefirst dark space F is called the Faradaydark space, the second, the Crooke's darkspace, and the greyish region between Nis called the negative glow. What isleft of the mauve discharge P is calledthe positive column, the latter is fre-quently striated as shows in the Figure.With continued exhaustion of the tube,the positive column continues to shortenand finally disappears. Next, the Fara-day dark space disappears, and finallythe negative glow reaches the anode ofthe tube; when this condition is reached,the phenomenon is called a cathode-raydischarge.

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The explanation of the cathode-raydischarge is as follows: If there is muchgas, perhaps the number of positive ionsmoving on the cathode produce apprecia-ble intensity or space charge of positiveelectricity, the electrons, because of theirhigh speed, being yanked out in 1/1000ththe time which the positive ions requireto cross. The layer of positive electric-ity occurring in the middle of the tubedisturbs the normal drop in potentialfrom the anode down to the cathode andextends the positive electricity of theanode well down the tube. This leads towhat is known as the cathode dark space,which is a space in which, perhaps, 80per cent. of the potential drop of thetube is concentrated. From the cathodeto the edge of this space charge the elec-trons are very rapidly accelerated andproduce the ionization accompanied bythe emission of light in the body of thetube. The blueish layer at the cathode

Page Seven

doubtless has to do with the conditionsresulting from the bombardment of thcathode by positive ions and the neutral-ization of those ions taking place at thatpoint. This layer will vary in color de-pending upon the nature of the gas oc-cluded in the metal.

Cause of Ray DischargeThe cathode-ray discharge will pass

through any highly evacuated tube inwhich there is still enough gas to enablethe mechanism to begin which possessesinternal conducting electrodes (prefer-ably of a non-metallic nature). Whenthe electrodes are subject to high elee-

The free electrons are repelled by thecathode or negative pole, and if the vac-uum is sufficient, pass through the great-er portion of the length of the tube with-out serious loss of energy. They there-fore have velocities which at maximumare equivalent to the potential dropacross the tube, but in general are some-what less due to the loss of energy toionization of neutral atoms on the way.On the other hand, the positive ions ac-celerated in the high field move towardthe cathode and impinge thereon withconsiderable energy. Of the positiveions impinging, a certain fraction, from10 to 1/10th per cent, succeed in knock -

in sufficient numbers to maintain thesupply of electrons. The cathodic elec-trons move in straight lines under the in-fluence of the field and are acceleratedso that many of them on reaching the an-ode, or positive electrode, have an ener-gy corresponding to the potential acrossthe tube. These straight beams of elec-trons are called cathode -rays.

Today electrical manufacturers donot bother with a gas -filled tube for ob-taining cathode rays. The modern cath-ode ray tube has a cathode of an incan-descent filament or an indirect heaterwhich emits electrons and acceleratesthem to the anode in the best possible

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tric stress by the application of somethousands of volts potential difference,the few ions existing in the residual gasdue to outside causes gain enough ener-gy in the high electric field to crashthrough many neutral molecules, tearingout electrons from these molecules andfilling the space between the electrodeswith positive ions and free electrons.

Page Eight

P61. 4-ing out more electrons from the cathode.The process goes o; the emission of eles-trons from the cathode increasing until aself - maintaining mechanism is estab-lished. Under these conditions a cer-tain number of electrons are 1:beratedfrom the cathode, which in turn succeedin ionizing enough of the residual gas sothat the positive ions reach the cathode

vacuum. The currents obtained in thisway are much greater, more uniform inintensity, and finally all electrons haveacquired sensibly the potential across thetube.

The Modern Cathode-ray TubeA sketch of a modern cathode-ray tube

is shown in Figure 2. The device func-

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tions as follows: A filament heats atube called a cathode, and negativelycharged particles of electricity are emit-ted in all directions. These electronsare attracted by a positively chargedplate called an anode. This anode has aperforation in its center and a stream ofelectrons shoots out through this open-ing and impinges upon a chemicallytreated surface (willeante or calciumtungstate) called a screen, which is atthe top end of the tube. Electrons strik-ing this surface produce a glow or flu-oreseense which varies in turn with theintensity of the element controlling theflow of electrons. A negatively chargedcylinder concentrates the electrons emit-ted by the filament so that practically allpass through the small hole iu the anode.The percentage of electrons passingthrough the hole in the anode dependsupon the size of the hole, the field be-tween the cathode and the anode, theshape of the surrounding electrodes, elec-trical conditions about the anode, andother factors dependent upon the temper-ature of the anode which are too nu-merous to mention. Possibly the fractionpassing the hole can vary from one -tenmillionth or less to possibly one per centof the electrons. The energy given tothe electron to pass to the chemicallytreated surface can only be approximat-ed by 'direct experiment; however, theelectrons gain their energy from the elec-trical accelerating field.

Phenomenon of FluorescenceThe phenomenon of fluorescence may

be best explained with the introductionof atomistic ideas and yet not be be-yond the comprehension of those notthoroughly conversant with electron me-chanics. The explanation is: Electrons.triking the fluorescent material at thescreen -end of the tube expel electronsfrom that material. In the course of re -

JUNE, 1935

turn of these electrons to their parentatoms, light is emitted. The cathode-rayin striking the end of the tube gradual-ly spends its energy ionizing atoms.They ultimately end with zero velocityand are picked up by some positive ionor else slide along the glass wall' of theenvelope to one of the electrodes andescape. Most of the cathode rays pene-trate the screen and are ultimately. ab-sorbed. A few are reflected with loss ofenergy. The rays that were not absorbedor reflected are scattered obliquely andgo forth with lesser energy, that is, withthe same frequency but of decreasedmagnitude, similar to that of scatteredquanta. The energy that must be ex-pended to cause fluorescence is at pres-ent unknown to the writer. Fluorescenceis caused by an electron with as little en-ergy as possible, perhaps one or twovolts. However, IT IS INVISIBLE. ToSEE fluorescence, enough energy must beliberated per unit volume so that the vol-ume of density of light emitted causesa visual effect on the eye of the observ-er. Taking into consideration the notaltogether improbable assumption, manyinvestigators are inclined to believe thatwhen an observer's eye is dark adaptedhe could just see the density of ioniza-tion in a gas in which there are onethousand million ions per cubic centime-ter emitting light. In other words, theenergy of electrons must be such that inthe region in which the cathode-raystrikes, it must be sufficient to give athousand million ions per cubic centime-ter or more. The fluoresent materialgets rid of the energy in the form oflight.

Scanning or Deflecting RaysThe scanning of cathode rays upon the

fluorescent screen is done oy deflecting(Continued on Page 13)

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Page Nine

Variable Condenser Breakdown Voltages

THERE is an increasing tendency onthe part of variable condenser pur-

chasers, both professional and amateur, todemand condensers with certain voltagebreakdown ratings. This has led tomany mis-ratings, with the result thateven experienced experimenters and ama-teurs are confused by the contradictoryfigures. The trouble is that most ofthese ratings are calculated on the ba-

8000

1500

By RAYMOND L. MOOREHOUSEEngineer, The Allen D, Cardwell Mfg. Co.

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gl.BREAKOOVIN OF PAR CONDENSERS

sis of air separation between the plates,and many of them do not take into con-sideration such important factors asplate thickness and shape, operating fre-quency and also the ratio of inductanceto capacitance in the actual transmittercircuit.

In this connection, prospective users ofhigh -voltage condensers should be inter-ested in the curves shown in Fig. I.These represent the average of hundredsof individual tests made on stock con-densers of various types :.nd sizes bymembers of the writer's organization andalso by independent testing laborator-ies. They reveal some pertinent factsthat apply to all variable air condensers,regardless of make.

All the tested condensers had polishedplates with rounded edges. The use ofsquare edge plates in condensers intend-ed for high -voltage applications is al-together unthinkable, as square -edgeplates reduce the flashover voltage asmuch as 20%. This figure is not a mereguess, but is based on actual measure-ments.

The curves are correct for plate thick-nesses from about .025 to .062 inch.

Page Ten

Thinner plates reduce the rating by 8%or more, a fact that is not generally ap-preciated. Figure 2 explains why this isso. The thinner the plate, the more near-ly does it approach a sharp point, andof course corona and jumpover effectstake place muc)1 more readily frompoints than from rounded surfaces. Thecomparative bluntness of plate B, as

measured against plate A, reduces thesparking tendency considerably. Theplate thicknesses have been exaggerateda little to show the general idea.

It will be seen that there is a 15%difference between the breakdown vol-tages of the same air gap when the con-denser is used first on 515 kc. and thenon 4000 kc. The first frequency is re-

garded as average for the broadcastchannels, and the second for the ama-teur and high -frequency communicationbands. No ordinary air dielectric vari-able condenser is ever used on 60 cycles,but the uppermost curve is included be-cause it is often convenient to test flash-over voltages at that frequency.

practical use of these curves is madein the following manner. Begin with the(I. c. plate voltage of the tube, multiplyby three, and from the chart pick a con-denser air gap with that flashover vol-tage, bearing in mind the approximatefrequency the transmitter is to use.

Fig L.

This procedure applies to circuits thatare keyed for c. w. teleg1raphy. Ifthe tube is plate modulated, use the mul-tiplying factor four.

Split stator condensers, which arewidely used in amateur transmitters,have a higher flashover voltage than theair gap alone indicates, as the sections

are usually in series in relation to theapplied voltages. In a series of measure-ments made on Cardwell condensers withair gaps from .07 to .218 inch, the flash -

Over voltage for two sections was from1.6 to 2.1 times that of one sectionalone.

The L -C ratio of the plate tuning cir-cuit must also be considered. The high-er the inductance, the greater the EMFdeveloped across the circuit, and thegreater the possibility of condenserflashover. This probably accounts forsome cases of flashovers in transmittersusing condensers of apparently adequaterating.

"Why worry about occasional flashov-ers in an air condenser, with its self -healing dielectrict" This question is fre-quently asked the writer oy amateursand engineers without much practicaloperating experienced with tube trans-mitters. The answer is found in the be-havior of a vacuum tube operated as anamplifier.

When the L -C circuit in the plate istuned to the same frequency as that ofthe exciting source on the grid, the platecurrent assumes a comparatively towvalue, only 10 to 20% of its normalvalue. Off resonance, however, it shootsup wildly. If the full rated plate vol-tage has been applied, the filament orcathode may readily lose all its emis-sion, or the elements may collapse be-cause of the terrific heat generated bythe bombardment of the plate. Cases oftube failure due to careless tuning areonly too common.

Now a condenser remains a condenseronly as long as its dielectric is intact.A flashover has the effect of short cir-cuiting the plates, with the result thatthe L -C circuit is thrown out of reso-nance and the tube takes the shock ofsuddenly increased plate current. Thecondenser itself isn't damaged apprecia-bly. A few small pit marks may devel-op at the sparking point, but these areeasily polished off.

The beet way to protect expensivetransmitting tubes from flashovers isto use condensers of suitable design an Ito operate the tubes within their ratedoutput, or below it. Plate current ,jumpscaused by off -resonance conditions willthen be less serious than with the tubesalready loaded to the limit.

COMMERCIAL RADIO

Methods of Calculating The CurrentCarrying Capacity of Resistors

By the Engineering Staff, Aerovox Corporation

IT is often required to find the maxi- mum safe current for a resistor ofgiven resistance and power rating, suchas a voltage divider. This problem canof course be readily solved with wellknown equations, yet it seems to takemore time and trouble than is warranted,probably because of the extraction of asquare root particularly when fractionsare involved. In this article the solutionby algebraical methods will be reviewed,showing how one can avoid the fractions;a labor saving chart is also presented,which shows the answer at a glance forpractically all such questions and withan accuracy which is sufficient for allpractical purposes.

Calculation of Maximum Currentor Voltage

The power in a circuit is found byany one of the three well known equa-tions:

P = E I (1)P = P R (2)

E2P = - (3)

depending on which are the given quan-tities. Here, E is expressed in volts, Iin amperes, R in ohms and P in watts.When the power is the required quan-tity, these equations are to be used, butif the power is one of the given quanti-ties and the voltage or current is re-quired, the equations have to be trans-posed so as to bring either E or I aloneto the left of the equation. This gives:

PI = amperes (4)

Ror,

P x 1,000,000I -VR milliamperes (4a)E=VP R volts (5)

Before going over to the examples,it is necessary to discuss the voltage di-vider some more. Such a divider mightfor instance be rated at 50 watts, al-lowing a certain maximum current. Nowthe resistor is divided into sections car-rying different amounts of current andconsequently dividing the power unequal.ly over the resistor. It should not bethought that since one section is carry-ing less than its share, that other sec-tions can handle more so as to bring thetotal up to 50 watts again. That cannotbe done; the maximum current is to bedetermined by supposing that the entire50 watts is to be divided uniformly andthe current found in this way shouldnot be exceeded in any section.

Similarly, the maximum voltage acrossthe resistor may be found by equation(5) again assuming that no current, isto be drawn from any tap. If any partof the resistor is to carry less than theallowable maximum current, the maxi -

JUNE, 1935

Maximum Current Ratings ofStandard Resistors

Resist. 10 25 50 75Ohms Watt Watt Watt Watt

1 3.16 amp.2 2.24 amp.2.5 2.00 amp.3 1.83 amp.5 1.41 amp.

10 1.00 amp.15 81720 70725 63430 57850 448

100 316 500 707 877200 224 354 500 613300 183 292 408 500400 158 250 354 432500 141 224 316 388750 115 183 258 316800 112 177 250 306850 108 172 242 297

1,000 100 158 224 2741,500 82 129 183 2242,000 70.7 112 158 1932,500 63.4 100 141 1723,000 57.8 91.2 129 1584,000 50.0 79.2 112 1375,000 44.8 70.7 100 1226,000 40.8 64.5 91.2 1127,000 37.8 59.8 84.6 1047,500 36.6 58.8 81.7 1008,000 35.4 56.0 79.2 97.0

10,000 31.6 50.0 70.7 87.712,000 45.7 62.0 79.215,000 40.8 57.8 70.720,000 35.4 50.0 61.325,000 31.6 44.8 54.830,000 40.8 50.040,000 35.4 43.450,000 31.6 38.860,000 35.475,000 31.6

Current ratings given above are allin milliamperes except those designatedin amperes (amp.). These currentsshould not be exceeded in any portion ofa voltage divider.

This list contains data on the mostpopular sizes of resistors. For similarinformation on other sizes, see othercharts.

mum allowable voltage is more than thevalue found by equation (5).

Mathematical Methods of Calculation

Example 1: What is the maximum al-lowable current for a resistor of 15000ohms and 25 watts? Using equation (4a)and substituting values:

25 x 1,000,000 5000P=V - -15,000 3

V1667 = 40.8 ma.

Example 2: What is the maximum al-lowable voltage across a 75000 ohm re-sistor with a power rating of 10 watts?Use equation (5); substituting values:

E V10 x 75000 =V750,000 = 100 V75 = 868 volts

Example 3: A speaker field has a resistance of 1000 ohms and is rated at 6watts. What is the current required? Useagain equation (4a)

6 x 1,000,000I-1000

V6000 = 77.5 ma.

Example 4. A resistor of 10,000 ohmsis to carry a current of 25 ma., what isthe dissipated power? Use equation (2),remembering that I is in amperes:P = .025' x 10,000 = .000625 x 10,000

= 6.25 watts

If the squaring of a fraction is incon-venient, the equation can be written:

PRP - watts (2a)

1,000,000

where I is in milliamperes. Using thesame examples:

25' x 10,000 625 x 10,000P -

1,000,0001,000,000

6.25 wattsThe table in this article has been pre-

pared for users of standard size resist-ors. It shows the maximum allowablecurrent for the most common resistorsof this kind; the current is given in mil-liamperes unless otherwise stated.

It is of course impossible to give thefigure for all possible cases in a table.The nearest approach one can make tosuch an ideal is to provide a chart andeven then it is difficult enough to coverthe complete range and to obtain suffi-cient accuracy to be of any use.

Logarithmic divisions are the onlyones which permit the coverage of a widerange keeping the accuracy the same per-centage throughout the range. The giv-en problem could be solved either by achart of the "alignment" type (also called"abac" and " nomograph "), or by theone shown. Both have their advantages.The first one does not have the page sofull of lines but it requires a straight-edge to get a solution. The second onedoes not require this; when two of thequantities: volts, milliamps, ohms orwatts, are known the other two can befound immediately.

The chart covers a range which shouldbe large enough for all radio work in-volving receivers and amplifiers. Theranges are from 1 to 1000 volts, from .1ma to 10 amperes, from .1 ohm to 10megohms and from .1 milliwatt to 10kilowatts.

The lines are plotted on regular fulllogarithmic coordinate paper. Currentis measured along the horizontal axis

(Continued on Page 13)

Page Eleven

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Electron Mechanics ofthe Cathode-ray Tube

(Continued from Page 9)the beam of electrons vertically and hor-izontally, that is, in a zig-zag fashionuntil the whole surface of the screen hasbeen irradiated. The deflecting actionmay be accomplished by either electro-static or electro-magnetic fields. Thesefields must be at right angles to one an-other and must intersect at the tube axis. In practice, one field is controlledby the current or voltage under observa-tion; the other is controlled by an alter-nating voltage to give a desired timingcontrol. This field serves to spread therays or tracing over the fluorescentscreen. Whatever method is employedfor deflecting the electronic beam, itonly need be remembered that the raysare attracted or repelled by the mechan-ical charges in the electric field. Howthis is done follows:

Theory of DeflectionThe cathode-ray particle is an electron,

nothing more or nothing less; thereforean electron is a moving electricallycharged mass, and its rectilinear propa-gation follows directly from the well-known principle of inertia in its motion,and its path in an electrical field is para-bolic in analogy to that of a stonethrown in the earth's gravitational field.Cathode ray particles may be attractedor repelled by a static or magnetic forcewhen in the field of these forces. Atthis point it is well to remember thatan electrical field produces a magneticfield, hence, it is this force that deflectsthe cathode ray beam. The theory ofdeflection is based upon electron median-ics which teaches: An electron movesfrom right to left with a velocity v, andhas a charge of value e. the electronconstitutes an electrical current movingfrom left to right. The value of thiscurrent is the number of units passingany point per second. The current valueis therefore e, because e units havepassed per second. In one second thiselectron has covered a length of path v,having an equivalent current strengthof e (electro-static units) in a length ofconductor v. (the cathode ray beam isa conductor.) If a current of strength iand length L is placed in a magneticfield H, Ampere's law states that sucha current will be urged at right anglesto the field and the current flow by aforce HiL. In the ease of the cathode-ray particle, a negative electron, the an-alogy would be Hey. There is no expla-nation to the fact that an electrical cur-rent is acted on by a magnetic geld.This is an observation of natural lawwhich has no explanation. and the onlyadaptation which must he made whendealing with electrons is that a movingelectron constitutes a current, the direc-tion of which, in the conventional sense,being opposite to the motion of the elec-tron. The law of electro-magnetic vibra-bration states: That a magnetic vibra-tion is always at right angles to the elec-tric vibration and proportional to it, andboth are at right angles to the directionin which the waves move. There is,therefore, a unique relation betweenelectric and magnetic vibrations in anelectric wave, this is graphically shownin Figure 3. Here, the magnetizing forceor strength of the magnetic field is rep-resented in the horizontal plane, that is,in the direction of the lines of force.

The theory of scanning or deflectionJUNE, 1935

may be summarized as follows: Thedirection of vibration of the electron isalways in the plane of the electric vi-bration, and perpendicular to the direc-tion of propagation of the waves, and isalso perpendicular to the plane of mag-netic vibration; hence, the intensities ofthe magnetic and electric fields are intime phase and space quadrature.How Cathode-ray Wave Patterns are

DevelopedNo simpler nor better explanation can

be given in describing how cathode-raywave patterns are developed than the in-formation disseminated by the WesternElectric Company, pioneer manufactur-ers of cathode-ray tubes and electronicapparatus. The explanation follows:

The electron stream in passing be -wren the lower deflecting plates (see

Figure 2) are deflected toward the posi-tive plate to an amount depending uponthe momentary electric field set up by thepotential difference between the plates.A second deflection at right angles to thefirst will take place when the secondpair of plates is reached if a differenceof potential exists between them. Theresult is that at any instant the record-ing point forming the end of the electronstream occupies a position on the view-ing screen, which, both in direction anddistance from its normal position is theresultant of the deflecting forces due tothe differences of potential acting atthat instant. In linear measurement,this distant amounts to about one milli-meter for each volt of the resultant po-tential difference. If the variations ofthe two intensities are cyclic and thefrequencies of the cycles bear some simpleintegral ratio to each other, the two com-ponents will be the same each time forany point in the cycle of the lower fre-quency and, therefore, the spot 3yill trav-el over the same path repeatedly andproduce a stationary pattern. The pat-tern may be considered as a plot in rec-tangular coordinates of the relation be-tween the two intensities or, if one ofthe fields is made to vary with time insome known manner, the variations ofthe other field with respect to time maybe studied.

The plot showing the relation betweenthe two intensities varies with anychange in phase, amplitude, frequency orwave shape of either of the deflectingfields. Figure 4 shows how the spotfollows the variations in Jhe two de-flecting fields. In this ease the twofields are 90 degrees out of phase, but ofthe same amplitude, frequency and waveshape. At the start of the cycle the firstfield is zero (A - 0°) and, therefore,produces no deflection of the electronstream. The second field at this sameinstant is at maximum (A, - 0°) and amaximum deflection of the stream isproduced when it passes between thepair of plates to which this field is connected. As a result of the two forces,the spot will occupy the position A,.When the two fields have passed through30 degrees of their cycle, the first fieldhas increased to B, the second decreasedto B,, and the spot is at Bs. At 60 de-grees the fields are at C and C,, respec-tively, and the spot at C,, and so on.

Figures 5 to 15, inclusive, illustratethe changes in pattern resulting from va-riations in the form controlling factorsmentioned at the beginning of the pre-ceding paragraph. In each figure A rep-resents the pattern B and C the deflect-ing fields.

Figures 5, 6, 7 and 8 show changes in

the pattern resulting from changing thephase of the deflecting field C but not B.

Figures 11 and 12 show the pattern re-mains unchanged when the phase of bothdeflecting fields B and C are changedalike.

Figures 5 and 10 show the change inthe pattern resulting from changing thewave shape of the deflecting C butnot B, when both fields are in phase.

Figures 5 and 9 show that the pat-tern remains unchanged when the waveshape of both deflecting fields B and Care changed alike, when both fields arein phase.

Figures 7, 11, and 13 show the chang-es in the pattern resulting from chang-ing the wave shape of the deflectingfields when they are not in phase.

Figures 7 and 14 show the change inthe pattern resulting from changing theamplitude of the deflecting field B butnot C when both fields are in phase.

Figures 5 and 15 show the change inthe pattern resulting from changing thefrequency of the deflecting field C butnot B, when both fields are in phase.

BibliographyWatson -Watt, R. A. "The Cathode -

Ray Oscillograph in Radio Research,"His Majesty's Stationery Office, London,England

Instruction Book and Treatise, RCAParts Division, Camden, N. J. (send10e to cover mailing)

See further references in the volumesof Science Abstracts, Engineering Index,Industrial Arts Index, and the Proceed-ings of the I. R. E.

Methodsthe

of CalculatingCurrent Carrying

Capacity of Resistors

(Continued from l'age 11)

(X-axis) and volts along the vertical(Y-axis). When this is done, the locusof all points representing a given resist-ance will form a line making an angleof 45 degrees with the X-axis. All theselines are parallel, sloping upwards tothe right. All points representing thesame power are situated on a straightline which makes an angle of 135 de-grees with the horizontal, sloping up-wards towards the left. These slantinglines are again spaced in logarithmicproportion, forming the network withquadruple index.

Use of the ChartA few examples will best illustrate the

use of the chart. Suppose the e.m.f. in acircuit is 100 volts and the current is100 ma.; what is the resistance and thepower? Beginning with the 100 ma.mark on the horizontal axis, follow thevertical line to the intersection with thehorizontal 100 volt line. This is also anintersection of the slanting lines. Fol-lowing the one going upwards to theleft read 10 watts; following the other,towards the right, read 1000 ohms.

A 5000 ohm resistor has a rating of20 watts; what is the maximum currentand corresponding voltage? Followingthe 5000 ohm line until the 20 watt lineis reached. Follow tie vertical lines downand interpolating by estimation read 63ma. Then follow the horizontal lines to-wards the left and read 316 volts.

Page Thirteen

New A -C. Mains Operated Speech

Input Equipment at Lausanne By DIPL. ING. E. METZLER and R. W. HARDISTY

THE new studio building of the So-ciete Romande de Radiophonie, which

was opened for service in February,1935, is situated close to the main Lau-sanne -Berne road at La Sallaz at aheight of about 700 meters above theLake of Geneva in a rapidly developingsuburban area.

The Societe Romande de Radiophoniehas operated a broadcast service in Lau-sanne from the earliest days of broad-casting when the small telephone trans-mitter, then located at the Lausanne air-port, was used and broadcasting had tobe suspended when service messages toaircraft were transmitted.

In 1930 the new Swiss National Trans-mitter at Sottens was opened, and broad-casting in French-speaking Switzerlandentered on a new phase of development.

Shortly after the opening of the Sot -tens station, the Bell Telephone Manu-facturing Company was commissionedwith the reequipment of the five existingstudio centres in Switzerland: Berne,Basle, Lausanne, Geneva, and Zurich, aswell as the installation of a new studiobuilding at Lugano to serve the Italian-speaking region.

I n 1933 the Societe Romande de Radio-phonie (S.R.R.)accommodation at Lausanne was inade-quate for their needs and purchased asite at La Sallaz, where the new studionow stands.

The new building is constructed of ce-ment -faced brick, the walls of the studiowhich are also constructed of brick be-ing insulated acoustically from the out-er shell of the building.

There are seven studios and an artifi-cial echo room. The largest studio is aconcert hall and has been designed toaccommodate the Suisse Romande Or-chestra. It is 25 by 15 by 10 meters highand is equipped with a concert organ.

There are three medium sized studiosfor chamber music and radio plays; thetwo radio play studios being differentlytreated acoustically. Two talks studios,an effects studio, and the echo room com-plete the programme accommodation inthe building. The remainder of the build-ing provides for the administrative offi-ces, a lounge for the orchestra, a musiclibrary, and the caretaker's living quar-ters.

The principal floor plans of the build-ing are shown in Figs. la, lb, and lc,from which it will be seen that only twoof the studios are visible from the Con-trol Room. This has necessitated a verycomplete signalling system.

Overlooking the two radio play studiosis the Dramatic Control Panel Room.This room contains an eight channelmixer which can be placed in the handsof the dramatic producer to enable himto fade his actors in and out as required

Reproduced by courtesy of "ElectricalCommunication," April, 1935.

Page Fourteen

1111,11 ...A new and up-to-date studio build-

ing has recently been inaugurated bythe Societe. Romande de Radiophonieat Lausanne, Switzerland. This stu-dio building, which caters for some ofthe programmes originated in French-speaking Switzerland, incorporatesmany new features and has beenequipped with the latest type of all -mains speech input equipment. Thisarticle deals with the design of thisequipment and its application to thevarious types of programme transmit-ted in modern radio broadcasting.

luring the play. On each side of the Dravatic Control Panel itself are the gramo-phone reproducer sets, used for effectsduring plays and for regular broadcastsof gramophone music. Stock market re-ports and sporting announcements aremade from this room. The Dramatic Con-trol Room is therefore also used as anannouncer's room.

In order to enable a correct modula-tion control to be effected during largeorchestral broadcasts, two special controlrooms have been provided. These havebeen equipped with a gain control poten-tiometer and a wide range loudspeakercombination so that the studio musicaldirector or other official can himself con-trol the modulation of the programmeduring the performance of the concert,while listening to the programme underconditions as nearly ideal as possible.

New Standard Speech Input Equipment

Amplifier DesignThe amplifiers which make up the New

Standard Speech Input Equipment asinstalled at Lausanne have been designedfor either mains or battery operation,and have the advantage of low consump-tion obtained by the use of quarter am-pere repeater type valves throughout.They do not, therefore, suffer from thedisadvantage of heavy filament batteryconsumption when operated from batter-ies, and their background noise whensupplied from a -c. mains is as low asthat obtainable by the use of specialtype equipotential valves, the actualnoise level due to a -c. components in thefilament current being below the level ofthe noise due to the various sources ofnoise in the valves themselves.

The total gain between microphoneand line is divided among four amplifi-ers. A microphone amplifier with a gainof 12 db. used between moving coil mi-crophones and studio mixers and an "A"amplifier with a maximum gain of 70db. constitute the "low level" amplifiers.In general, one microphone amplifier permicrophone and one "A" amplifier perstudio are employed.

The "high level" amplifiers constitut-ing the remainder of the chain am.; a"B" amplifier and a "C" amplifierwith a combined gain of 45 db. One

" B" amplifier per programme channeland one "C" amplifier per output lineare employed where more than onebroadcaster is supplied with the sameprogramme. In the installation now be-ing described, output branching is notperformed at the studio building, and a"B" amplifier with a single output isused. This amplifier has a gain of 35 db.

Figs. 2a, 2b, and 2a show the circuitarrangements of the microphone and" A " and "B'' amplifiers, respectively.

In every type of amplifier the filamentcircuits of all valves are built out, wherenecessary, to 4 volts and are brought toseparate terminals on the panel. Everyamplifier can therefore be operated from6 volt, 12 volt, or 24 volt batteries bysuitably connecting the filament circuits.With 6 volt and 24 volt supplies there issufficient margin of voltage to includefilament decoupling chokes as a safe-guard against crosstalk through the bat-tery; with 12 volt and 24 volt suppliesall grid bias potentials can be takenfrom resistances in the filament circuits.

Plate circuits are arranged for 130volt or 200 volt supplies and the equip-ment is therefore generally capable ofbeing adapted for operation from bat-teries which may already be in service.

Metering arrangements for plate cur-rents have been eliminated from the pan-els and are arranged at a central pointon the equipment. This arrangementmakes it possible to mount the ampli-fiers anywhere on a standard repeatertype rack without the necessity of tak-ing into consideration the question ofaccessibility, except for occasional valvereplacements.

Only the high level ("B," "C" andmonitoring) amplifiers have any appara-tus, projecting in front of the mountingplate; all valves in the low level (micro- .

phone and "A") amplifiers beingmounted under the can covers.

The elimination of noise due to me-chanical and acoustic shock on the valveshas received special attention. Every am-plifier both high and low level, isequipped with spring mounted valvesockets which, in the case of the lowlevel amplifiers, are themselves amountedon a sprung platform weighted with theinput and output transformers. In themicrophone amplifier, the valve is mount-ed under a felt -lined metal cover and asimilar precaution is taken for the firsttwo valves of the "A" amplifier. Fig.3 shows a bay of "A" amplifiers withcoverd removed. On the high level ampli-fiers metal shields are used over the pro-jecting valves.

All amplifiers are equipped with in-terstage equalisers so that the distortionat each end of the frequency range dueto the transformers may be compensated.By this means the overall characteristicsof a system comprising microphone am-plifier, "A" amplifier, "B" amplifier(and "C" amplifier when used for out-put branching) can be adjusted to lie

COMMERCIAL RADIO

PIJEL

ROOM

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CON3 N00

((LIAR, I CELLAR

CF,TC V 5

STUDIO AMR /410,A311.1ANS

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Fig. lb-Floor plan.

Fig. lc-Floor plan.

within 2 db in the range of 30-10,000cycles. Special precautions in the ampli-fiers have been necessary to ensure sta-bility, since the overall gain from micro-phone to line exceeds 100 db.

Single -output "13" amplifiers and"C" amplifiers are supplied with multi -ratio output transformers so that theoutput impedance can be adjusted to beconsiderably less than that of the line itfeeds, and the amplifier thus sends aconstant voltage to line independent ofthe impedance variations of the latter.

Mixer Design

Throughout the system only one typeof mixer potentiometer is used. This po-tentiometer provides twenty-two stepsand a cut-off position and can be builtup to two, three and four -channel units,terminating and building -out resistancesbeing provided so that all mixers haveinput and output impedances of 200ohms. Special arrangements have beenmade to reduce crosstalk to a minimum.

JUNE, 1935

Each potentiometer is furnished with anauxiliary cam -operated contact whichopens only in the "cut-off" position andwhich is used to operate warning lightrelays, etc. The attenuation per step in-creases as the total attentuation in-creases and a smooth fade out withoutsudden cut-off is therefore obtainable.

Reproducer Sets

The gramophone equipment suppliedis designed for 78 r.p.m. and 331/3 r.p.m.playing speeds. The pickup arm isequipped with an indicating scale sothat the pick-up may be lowered at anypredetermined point en the record. Thegramophone sets are built on a unit ba-sis as "playing units," each consistingof a pick-up, motor, turntable, and fadermounted on a steel plate. The fader isof the same type as that used on the mix-er panels and the auxiliary contacts areused to operate a device for raising andlowering the pick-up. This feature is es-pecially useful when using effects rec-

ords in radio drama, since the pickupmay be lowered on to a groove in therecord in which the desired noises occur.

Signalling System

Tn a modern studio building wheremany, if not all, of the studios are outof sight of the Control Room, a completeand unambiguous signalling system isessential.

The signalling system which has beenadopted after prolonged experience onStandard Speech Input Equipments pro-vides a "Ready" signal between thestudio and the Control Room, and a"Start" signal between the ControlRoom and the studio. In addition, a redwarning light in any studio lights whenthe microphones in that studio are con!meted through to the amplifiers. Thisred lamp is entirely automatic in opera-tion and is independent of the "Start"signal.

The "Ready" and "Start" signalsystem consists of a green lamp in thestudio and a corresponding switchboardlamp in the Control room. These twolamps light simultaneously and can be litor extinguished either from the studioor from the Control Room. The lightingof the lamps by the studio leader, or con-ductor of the orchestra usually consti-tutes the "Ready" signal and the ex-tinction of the lamps by the control engi-neer constitutes the "Start" signal.

In addition to the above, a simple sys-tem of blue lights is used from the Dra-matic Control Room as cues for the ac-tors to speak their lines during the per-formance of the radio plays. These lampsare operated by locking keys on the Dra-matic Control Panel and can be exting-uished only by the producer.

Level Indicators

The Lausanne installation is one of thefirst to use the newly developed Stan-dard Programme Meter. This device isa rectifying valve voltmeter which is ar-ranged to have an approximately loga-rithmic characteristic so that level is in-dicated directly in decibels. The milliam-meter included in the plate circuit isspecially calibrated from a level of -35db. to a level of +5 db. referred to azero level of 4 volts. A single frequencycalibrating oscillator is provided to en-able the zero indication at 4 volts to bechecked and adjusted periodically.

The advantage which the new paneloffers over the other types of level indi-cators can best be appreciated after ac-tual control of a musical broadcast. Thespecial logarithmic scale is obtainedwithout the use of multi -electrode valvesor of specially constructed meters, tworeactance coupled valves only being em-ployed.

The calibrating oscillator used with theprogramme meter can also be used tocheck the attenuation of an outsidebroadcast circuit. The circuits normallyused for outside broadcasts vary in lengthfrom 1 or 2 to 20 or 30 miles, and Stan-dard Electric outside broadcast ampli-fiers are used at the pick-up point. Theseamplifiers have a rectifier meter connec-ted across the output; and, by transmit-ting a known level from the studio withthe oscillator, the attenuation of the cir-cuit can be measured roughly by meansof the meter on the outside broadcastamplifier. The operator at the remotepick-up point can then adjust his ampli-

Page Fifteen

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fier gain so as to feed the correct levelto the studios.

Mains Operation

From the outset it was decided thatthe entire equipment should be operated

T2 from the 220 volt, 50 cycle a -c. mainswith the exception of the signalling sys-tem and the intercommunicating tele-

R8

IN system, which are operated from4 E a 24 volt battery.

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first scheme each amplifier is asso-oTwoschemes suggested themselves. In

4V elated with a separate rectifier andsmoothing panel for both high and low

8 66 tension supply; while in the secondscheme, floating batteries used in con-junction with large central rectifiers andfilters are controlled by means of volt-meter relays, so that at all times batterypower is available in case of mains fail-ure, while the batteries cannot be over-charged due to the action of the volt-meter relays.

After careful consideration, the SwissAdministration selected the first scheme.Each amplifier panel is, therefore, asso-ciated with a rectifier panel located on aseparate rack assembly so as to minimiseinduced fields. The rectifier panels incor-porate two stages of filtration and theseare found to attenuate the residual humsufficiently to permit satisfactory opera -

OUT tion of the high level amplifiers, Micro-phone amplifiers and "A" amplifiers are,however, each equipped with an addition-al smoothing panel incorporating a thirdstage of filtration. These smoothing pan-els are located on the amplifier bays closeto the amplifiers with which they are as-sociated in order to avoid induction from

o.urs the input of the filtering system to its0.1.7 2 output, the attenuation in the filters be-

ing of the order of 110 db. for the lowtension, and 130 db. for the high tension.o L71 Two transformers are provided, step-ping the 220 volt mains down to 35 and125 volts respectively for low and hightension supplies, and each rectifier paneltakes its supply from a separate low ten-

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INPUTIMPEDANCE

STRAPTERMS.

CONNECT TOTERMINALS

2511 966; lad 96105011 115,2.6 I 1 2

20011 i66 265

Fig. 2a-Circuit Schematic of Microphone Amplifier

INPUTIMPEDANCE

STRAPTERMS.

CONNECTTO TERMS,

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2001' It 6 2 as

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The background noise on the system,+12 when supplied from the mains, is reduced

to the level of the valve noise.

Circuit Arrangements in Lausanne

TYPICAL. GAIN FRE OU EN CY CM ARACTERISTIC.

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OUTPUT CONNCCT TOIMPEDANCE TERMINAL.5

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Page Sixteen

7 do 3 4 5 G 782 600 S

Fig. 2b-Circuit Schematic of "A" Amplifier

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Figure 2c-Circuit Schematic of "B" Amplifier

S 4 5 C. 8944 Speech Input EquipmentMicrophones

Standard moving coil microphoneshave been used for all general pick-upwork, condenser microphones being re-tained for orchestral broadcasts. Circuitarrangements have been provided to takecare of widely different output levels ofthe two types. In addition, it was neces-sary to cater for a certain number ofcarbon microphones for use in the effectsstudio and in the echo room where strin-OUTgent quality requirements do not exist.

The solution arrived at involves theprovision of the microphone amplifiersdescribed above for all moving coil andcarbon type microphones. These ampli-fiers are rack -mounted and are located inthe main amplifier room where they canbe under constant supervision and sohave an advantage over the condensermicrophone amplifiers which must belocated in the studios. The amplifiers forthe carbon microphones supply polarisingcurrent derived from the filament circuitrectifiers to the microphones themselves.Fig. 4 shows the general system layoutfrom which it will be seen that the three

COMMERCIAL RADIO

SLUNG PLATFORMFOR ALL VALVES

INTERSTACLEQUALISER

SMOOTHINC;PANEL

2") VALVES UNDERSHIELD

Fig, 3-"A'' Amplifier Bay (Rear view, covers removed)

principal studios are each equipped withseveral microphones and the outputs oftheir associated microphone amplifiersare brought to four, three and two -chan-nel mixers. The object of these mixers isto obtain a realistic reproduction of allthe instruments in the orchestra, and forthis reason the placing of the micro-phones and the setting of the mixers de-mand a great deal of patient experimenton the part of the programme staff priorto the broadcast. When the final settingshave been decided upon they are record-ed, and the conditions obtained can thenbe repeated during the broadcast per-formance.

With a view to the employment of aDramatic Control Panel and for otherreasons, high level fading and switchingwas decided upon, and every programmesource, studio, gramophone, etc. isequipped with an independent "A" amp-lifier so that at the switches on the en-gineer's control desk the level of thestudio programme is approximately equalto that, from the outside broadcast lines.This condition can be realised by the in-dividual adjustment of gain provided ineach "A" amplifier.

When used for the production of aradio play, any studio can be patched toany input channel of the Dramatic Con-trol Panel, and thenceforth it is complete-ly under the control of the producer up tothe time that the patching cords are re-moved and the studios are again connec-ted to the regular control and switchingdesks for normal programme use. Whileconnected to the Dramatic Control Panel,the red warning lamps in the studio areautomatically operated when the- pro-ducer fades out the studio. The layoutof the Dramatic Control Panel has beencarefully arranged for operation by es-sentially non -technical personnel.

Another interesting feature of the in-stallation is the provision of artificialecho. This device was at one time used in

JUNE, 1935

an endeavour to simulate concert hallacoustics when using a small heavilydamped studio, but its use is now almostentirely confined to the provision of spe-cial effects in radio plays.

Artificial echo is produced by splittingoff a small portion of the microphoneoutput and reproducing the sounds bymeans of a loud speaker in a reverberantroom. Here the reverberant sound ispicked up by another microphone and theoutput of this microphone is mixed withthe output from the studio. A commonway of achieving this result is to split offthe output of the studio "A" amplifierat a level of about -10 to -20 db. asshown in Fig. 5. The arrows indicate thedirection in which the amplifiers operate.An additional amplifier (AAA.) is oftenadded, as shown as a precaution againstsinging round the path a, b, c, d, e, andf.

In the Lausanne studios, however, theecho room loudspeaker is fed from a separate microphone and the resultant re-verberant sound may be mixed either atlow lvel on the studio mixer or at highlevel on the main control positions or onthe Dramatic Control Panel. With thisarrangement there is no possible singingpath and an anti -singing amplifier is notrequired.

The programme control equipment isduplicated so that it is possibln for re-hearsals before the microphone to be con-ducted at any time while broadcasting isin progress. Two control desks are pro-vided in the Amplifier Room, each beingassociated with a "B" or line amplifier,and each having access through itsswitching panel to every studio or pro-gramme source inside the building or toany outside broadcast line. In case of abreakdown of one programme channel itis possible immediately to pick up thestudios in use on the other channel andto continue the broadcast with a delay of

only 10 or 20 seconds. Crosstalk betweenthe two programme channels receivedvery careful attention and the figuremeasured on the installation was in ac-cordance with C. C. E. requirements forcrosstalk between repeaters (10 nepers=87 db.). The "B" or line amplifiersare designed for one output only; furth-er output branching is performed at theLausanne Repeater Station to which theoutput of the studio amplifiers passes.Here there are four branching amplifiersconnected with the broadcast repeaterwhich feeds lines to Sottens Broadcaster,Berne, Geneva (local broadcaster), andMartigny. The fourth amplifier (Nfartigny) also feeds the local teleprogrammeamplifier which provides the programmeto subscribers' loudspeakers on the Lau-sanne automatic exchange.

The above reference to teleprogrammeservices in Switzerland may call for somefurther comment. The service was insti-tuted in the larger towns in 1931 andprovides telephone subscribers who rentan amplifier -loudspeaker equipment withreliable high quality reproduction fromone of the three Swiss programmes (Ger-man, French, or Italian). This service isprovided entirely from the toll cable sys-tem and is therefore unaffected byweather conditions or by other sourcesof interference. It is now available innearly every important town in Switzer-land and is being extended as rapidly asthe high quality toll circuits themselvescan be extended to the towns concerned.The service is made use of by the studiofor quality checking and for verificationof the circuits when a change over to an-other studio is made. Such a change -overoccurs several times daily when the Ge-neva studio takes up the French pro-gramme or when the news bulletin is readfrom Berne. In certain cases relay opera-tion has been arranged so that the rever-sal of the repeaters may be effected fromthe studio building itself, but in othercases where manual operation is involvedit is of interest to check on the telepro-gramme service whether the switch -overhas been correctly performed. This caneasily be done because the teleprogrammeservice is branched across the output ofthe Lausanne Repeater Station and,unless the repeater is switched over toreceive the transmission from the studiocontinuing the programme, no outputfrom the teleprogramme service will heobtainable. A check by the radio receiverensares that the programme reaches thebroadcasting station. 11 isi thus possibleto cheek the programme at each stage ofits transmission between the studio andthe broadcasting station.

Monitoring, therefore, can be effectedon the outgoing line from the studiobuilding, at the output of Lausanne Re-peater Station, and by a radio receiverat the output of the Sottens broadcaster.In the amplifier room, in the two listen-ing cubicles, in the effects room, and inthe Dramatic Control Room, all three ofthe above monitoring services are avail-able on omnibus circuits. A fourth cir-cuit connected with the output of the sec-ond programme channel is also available.Elsewhere in the building only the tele-programme service is obtainable.

At all points loudspeakers of the tele-programme type with self-contained amp-lifiers are installed. These can hebranched across any of the four omnibuscircuits and each circuit is adjusted so

(Continued on Page 21)

Page Seventeen

Actions of The Federal Communications CommissionApplications for New

Broadcasting Permit

International Ladies Garment WorkersUnion, N. Y. City, 970 kc., 1 kw.

Caller -Times Pub. Co., Corpus Christi,Tex., 1330 ke., 1 kw.

Roberts MacNab Hotel Co., Jamestown,N. Dak., 1420 kc, 1 kw.

W. H. Kindig, Hollywood, Cal., 1300 kc.,1 kw.

George B. Storer, Detroit, Mich., 680 ke.,1 kw.

Golden Empire Broad. Co., Redding, Cal.,1370 ke., 100 watts

Thomas Broad. Service, Inc., Quincy,Mass., 1200 ke., 100 watts

Florida West Coast Broad. Co., Tampa,Fla., 1370 kc., 100 watts

Black Hills Broad. Co., Rapid City, S.Dak., 1370 kc., 100 watts

Northern California Amuse. Co., Yreka,Cal., 1500 ke., 100 watts

Hyman Altman, Detroit, Mich., 1370 ke.,100 watts

Pampa Daily News, Inc., Pampa, Tex.,1200 kc., 100 watts

Plainview Broad. Co., Plainview, Tex.,1500 ke., 100 watts

Bell Publishing Co., Belton, Tex., 1370Ice., 100 watts

Dudley J. Connolly & Co., Chattanooga,Tenn., 1200 ke., 100 watts

Valley Broadcasting Co., Pomona, Cal.,1160 kc., 250 watts

A. Corenson, Pasadena, Cal., 600 ke.,250 watts

Honolulu Broad. Co., Ltd., Hilo, Hawaii,

California Sales Contract Co., San Fran-cisco, Cal., 1280 ke., 500 watts

L & S Broadcasting Co., Waycross, Ga.,1200 ke., 100 watts

E. L. Sherman & H. L. Corley, Trinidad,Colo., 1370 kc., 100 watts

Walker Jamar, Duluth, Minn., 1500 ke.,100 watts

Golden Empire Broad. Co., Sacramento,Cal., 1500 ke., 100 watts

Herbert L. Blye, Lebanon. Pa., 1240 kc.,100 watts

Herbert L. Blye, Union City, Pa., 1420kc., 100 watts

Carl S. Taylor, Dubois, Pa., 850 ke.,250 watts

Raton Broad. Co., Raton, N. Mex., 1500kc., 100 watts

Waycross Broad. Co., Waycross, Ga.,1200 kc., 100 watts

E. W. Patrick, Brookfield, Mo., 1210 ke.,100 watts

Howard W. Haskett, Santa Rosa, Cal.,1280 ke., 250 watts

Pacific Acceptance Corp., San Diego,Cal., 1200 kc., 100 watts

L. E. Robideaux, Bend, Ore., 1500 kc.,100 watts

William S. Thellman, New Castle, Pa.,1200 ke., 100 watts

The Attala Broad. Corp., Columbia,Miss., 1200 ke., 100 watts

Ralph E. Smith, San Diego, Cal., 1200kc., 100 watts

Springfield Newspapers, Inc., Spring-field, Ohio, 1120 ke., 250 watts

L. & S. Broad Co., Atlanta, Ga., 1210kc., 100 watts

Oil Capital Broad. Assn., Kilgore, Tex.,1210 kc., 1.110 watts

R. E. Chinn, Moorhead, Minn., 1500 ke.,100 watts

Page Eighteen

Mason City Broad. Co., Mason City, Io-wa., 1420 kc., 100 watts

W. L. Gleason, Salinas, Cal., 1210 kc.,100 watts

Mrs. C. A. S. Heaton, Las Vegas, Nev.,1420 kc., 100 watts

Marysville -Yuba Publishers, Marysville,Cal., 1210 kc., 100 watts

Kelsey -Jenny Commercial College, SanDiego, Cal., 1210 kc., 100 watts

New Applications GrantedNational Broadcasting Co., Chicago, Ill.

Authorized to use visual broad. sta-tion WX9AP, Freq. 1606, 2020, 2102,and 2760 kc., 2 kw.

Isle of Dreams Broad. Corp., Miami,Fla., New pick-up Station freqs. 1606,

A Tough Order

TWENTY-ONEradio broadcasting

stations, many of them outstanding,must appear before the Broadcast Divi-sion of the Federal Communications Com-mission on October 3, 1935, and at ahearing prove that their continued opera-tion will be in the public interest. Pend-ing the outcome of the hearing they willbe granted temporary licenses.

The stations cited are:KNX, Los Angeles; WRAP, Fort

Worth, Tex.; WGAR, Cleveland., 0.;WBAL, Baltimore; WOR, Buffalo, N.Y.; WHEC, Rochester, N. Y.; WHO,DesMoises, Ia.; WIOD, Miama, Fla.;WIND, Gary, Ind.; WIRE, Indianapo-lis, Ind.; WJAS, Pittsburgh, Pa.;

Radio Inspector-You want a2020, 2102, and 2760 ke., 50 watts

WBNS, Inc., Columbus, 0., General ex-perimental 31100, 34600, 37600, 40600kc., 2 watts

WCBD, Inc., Waukegan, Ill., General ex-perimental same as above

East Texas Broad. Co., Tyler, Tex., Gen-eral experimental pick-up hags. 31100,:14600, 37600, and 40600 ke., 30 watts

TELEGRAPH DIVISIONMODIFIED RULE 28

RULE 28. Insofar as practicable,call signals of radio stations wlil be des-ignated in alphabetical order fromgroups available for assignment, depend-ing upon the class of station to be li-censed. Because of the large number ofamateur stations, calls will be assignedthereto in regular order and requests forparticular calls will not be consideredexcept on formal application the Com-mission may reassign calls to the lastholders of record.

Broadcast License on THIS?

WJJD, Chicago; WJR, Detroit, Mich.;WKBW, Buffalo, N. Y.; WOW, Omaha,Neb.; WOWO, Fort Wayne, Ind.;WSMB, New Orleans; WTMJ, Milwau-kee, Wis.; KFRC, San Francisco; KM -

BC, Kansas City; and KMOX, St. Lou-is, Mo.

Applications for renewal of licenseswere designated for hearing, for themost part, because the stations at vari-ous periods carried a program entitled"Marmola," a preparation representedto reduce fat. That preparation hasbeen under the ban of the Post OfficeDepartment for some years and also is indisfavor with the Federal Trade Commis-sion. Some of the stations still carrythat program.

In cases where renewal application isnot now pending the Commission adopteda minute reading:

"Applications for renewal of li-cense ordered to be filed under Rule17 and upon receipt thereof said ap-

(Continued on Page 19)

COMMERCIAL RADIO

ASSIGNMENTSVessel Radio Operator

88 Haiti-R. Wilson88 Seminole-C. A. Luckenbach ( Jr.)88 Exeter-D. Decker (Jr)SS Shawnee-T. J. Burns (Jr)SS Pecos-H. Weinstein88 Cities Serv. Toledo-G. BirdMS Tampa-E. Rocks58 Excalibur-E. Fazulek (Jr)SS Black Gull-R. JacksMS New Orleans-S. Rosenberg

BALTIMOREW. W. Bruce-J. J. KaresWalter Miller-J. W. GewekenVacuum-T. W. BraidwoodFirmore-H. B. BellImlay-Vic EhlersSantore-Chris. VossClairton-C. E. SeibertHoward-C. W. CoreCity of Norfolk-H. M. ShadeCity of Newport News-J. H. MajorCity of Hovre-M. E. BartlesCity of Hovre-F. H. FlandersSilver Sword-E. R. MessinaOradell-E. J. FredholmMarore-M. CourcheneMagneric-O. ThiessOakmar-J. V. PohlmanCity of Hamburg-C. E. CookEastern Glade-J. C. LawlerWillboro-A. G. Goldbach (relief)Beaconlight-Frank Carroll

BOSTONHarvester-M. C. WakeaieldTrawler Cornell-J. Fiste (relief)Tug Wyoming-A. FallabellaSouthern Sword-R. T. HemmesTelde-A. L. DiMattia

CLEVELAND and GREAT LASESWestern States-Charles MacomberEastern States-H. UhlCity of Cleveland III-J. MitchellCity of Cleveland III-J. SpychalskiSumatra-Wm. J. SlettnerTug H. B. Williams-M. JensenCarferry Ashtabula-A. H. FreitagD. L. Callender-L. L. DuellJohn F. Cushing-August GesekiWm. E. Fitzgerald-R. GuthrieHarvester-Frank ZurekJ. Floyd Massey Jr.-J. J. SchmittSinaloa-Peter JavurekJ. M. Kennedy-H. C. SwansonMichigan-Joe BubnaPioneer-E. BlazekYosemite-J. CraverPresque Isle-F. SagerCadillac-Chas. LohnerIshpeming-E. DietzFrontenac-Joe PerraultJ. H. Sheadle-GardnerJames E. Ferris-Silas MikhelsonJ. J. Sullivan- H. SiebertA. A. Augustus-John B. ClarkJoseph G. Butler-W. CraveJ. P. Walsh-KeeneA. M. Byers-MilliganYacht Olive K.-D. McGaffinP. D. Block-Clyde ShawN. F. Leopold-CarterW. D. Calverly-Frank Caster

NEW ORLEANSSama-Wm. J. NeelMunplace-R. WickboldtVirginia-Arthur PilzeckerGranada-W. E. FordGranada-A. T. Teeter (2nd)

JUNE, 1935

Granada-Cyril Burck (3rd)West Tacook-L. T. BlackburnSahale-J. H. BigfordClearwater-A. WilkersonCananova-Arthur BettertonSimonla-Marks P. MatherneSixaola-Wm. Cleveland AhearnCopan-Delery FreretCastilla-Thurman Wilson

New YorkSocony Vacuum-K. F. BlakelyManhattan-T. SeroisShawnee-E. ColeSeminole-T. CainBlack Hawk-H. HeweyColorado-C. ScruggsWest Hnmpaw-B. BernsteinBirmingham City-E. W. OjaDixie Arrow-F. BogutH. H. Rogers-B. B. FergusonPresident Roosevelt-L. C. WyndomLillian Luckenbach-L. E. MillhollinVirginia-A. StanfordPonce-H. S. KuchtaSanta Rita-A. E. SpicerSanta Monica-W. P. PaschalA. C. Bedford-F. J. MitchEagle-J. GottesfeldSanta Rita-M. CamilloOriente-H. BlattDixiano-J. L. ShowersExcelsior-J. W. VoshellChincha-L. H. BrennanBrilliant-T. R. HarrisonPaul H. Harwood-M. J. McDonoughConcord-A. L. WilsonChattanooga City-E. P. FosterScanmail-M. SanbornOriente-J. GottesfeldPennsylvania-G. M. CurtinSanta Barbara-E. R. FritzMayan-G. W. StewartMayan-R,. CuppRelief-J. H. PerimanChristy Payne-G. R. McCallumGranada-R. FosterBirmingham City-W. DisneyBessemer City-C. M. WonnebergerMeton-D. MoirSt. John-H. BlattAmerican Importer-W. J. McEnteeBirkenhead-H. WallinAncon-F. De LaHuntAmerican Farmer-T. L. SiglinSanta Lucia-J. P. KellySanta Lucia-S. KovacsYankee Arrow-A. J. WalkerStandard-W. E. GilsonBeaconlight-J. K. AirdCathlamet-A. L. WilsonMemphis City-E. W. OjaPresident Roosevelt-Donald ShawJ. A. Moffett, Jr.-F. E. CarrolOriente-L. R. BevenseeThomas Tracy-C. A. MakiWest Lashawy-C. H. WeirMohawk-C. P. WhiteE. T. Bedford-Mac. BougereF. W. Abrams-H. KleinklausT. J. Williams-R. CuthbertMevanta-A. McCarterChina Arrow-C. G. BergerPonce-L. B. MarkowitzEd. Jeromac-Nicholas Close (Ch)E. Jeromac-R. S. HorscroftBlack Hawk-H. HeweryColorado-C. ScruggsHaiti-H. W. Martin

Portland, Ore.General Pershing-Roy WelbonGeneral Pershing-Harry SchoolfieldGeneral Sherman-Karl SteinerGeneral Sherman-Ted ToppiGeneral Lee-Everett HenryGeneral Lee-James CrouseCalifornia-Ben CohenIllinois-W. T ShultxichMichigan-Dallas L. HughesTexas-Roy WhittingtonIowa-John WalkerOregon-Howard McMahonPennsylvania-K. V. HarrisWashington-John RobinsonNew York-Gordon BurnettWisconsin-Walton F. MeeKentucky-A. A. MarshSan Angelo-Frank CaldwellSan Anselmo-Earl GarrickSan Bernardino-Herbert OliverSan Clemente-D. E. YoungbergSan Diego-Claude WarehamSan Domingo-Dewayne DuncanSan Felipe-M. R. DarbySan Gabriel-James DinsdaleSan Julian-Edward BatsSan Marcos-Ralph DernbachSan Simeon-Donald KelseySan Vincente-F. G. LueckeSan Pedro-Sydney FergusonSan Rafael-C. P. BurtSan Lucas-R. L. NorgardPeter Kerr-L. K. Bradley

A Tough Order(Continued from Page 18)

plication will be designated forhearing."In April 1929 the Federal Trade Com-

mission issued a cease arid desist orderagainst the Raladam Company, distribu-tors of Marmola. The concluding orderin that case directed that the RaladamCompany to cease and desist:

"From representing Marmola as aremedy for the treatment of obesityunless such repret.entation is ac-companied by a statement thatMarmola cannot be taken with safe-ty to physical health except underthe direction and advice of compe-tent medical authority."In that order the Federal Trade Com-

mission indicated that the promiscuoussale and use of Marmola is inimical tothe public health and possible menace tothe public welfare.

The Supreme Court of the UnitedStates, however, reversed the FederalTrade Commission in that case on theground that competition in interstatecommerce was not shown but made thisstatement :

"Findings supported by evidencewarrant the conclusion that theprepaparation is one which cannotbe used generally with safety tophysical health except under medi-cal direction and advice."The Post Office Department some time

ago cited Marmola is fraud order pro-ceedings and at the conclusion of thehearing Marmola producers stipulatedthey would go out of business and ceaseits mail distribution. Subsequently theMarmola Company reorganized, becom-ing the Raladam Company. While dis-

(Continued on Page 20)

Page Nineteen

NEW APPARATUSA. P. A. Amplifier

THE Radolek Company announces anew high quality genuinely all-pur-

pose model medium power Public Ad-dress Amplifier.

This amplifier was especially designedfor the countless medium sized installa-tions in which higher power and there-fore necessarily more costly amplifiersare not necessary. Its low cost and ex-cellent quality opens a new field forthe Public Address Installation Engin-eer.

Pre-eminently flexible, allowing theuse of carbon, and capacity, dynamic orvelokity microphones-operating up to7 dynamic speakers-provided with com-plete plug-and-socket-input and outputconnections-two input channels withcomplete mixing and fading equipment-hum-free-equipped with toe control andwith a flat frequency characteristic curvefrom 100-7000 cycles, 8 watts.

New Condenser Line

A new line of porcelain encased micatransmitting condensers, designed foramateur, police and small broadcasttransmitters, has been brought out bythe Cornell-Dubilier Corporation, 4377

. Bronx Boulevard, New York. Designedas the Type 86, the line includes thirteensizes ranging from .00005 mf. to .1 anf.,in voltage ratings from 2000 to 12,500volts.

These new condensers are especiallyrecommended for plate blocking, gridand tank applications. Their power fac-tor is extremely low and they will carrytheir full rated load over long, periodswithout heating up.

The mica condenser elements are her-metically sealed in heavy glazed porcel-ain containers, which are provided withmounting feet and screw terminals. Thesecermatic cases are not subject to ab-sorption effects when placed near therowerful fields of tank inductors, andthey therefore eliminate that appreciableloss that occurs when metal eased capac-itors are used in a crowded transmitter.Page Twenty

New Velocity Microphone

The new SR 80 velocity microphoneby Amperite has 4 db. higher outputthan ever obtained before in velocitymicrophones. This is in part due to thenew nickel aluminum magnets which areused. These magnets arc much strongerthan even the best Cobalt magnets avail-able today.

A new ribbon is also used in thismicrophone which makes it possible touse it against wind velocities up to 50miles per hour without in any way dam-aging the ribbon.

The directional properties of the mi-crophone do not restrict the angle ofpickup. Its area of coverage withoutfrequency discrimination is greater thanthat of any diaphragm type microphone.Over an angle of 120° front and back,the frequency ditforimination between30 and 10,000 cycles is less then o.1 db.The sound level is uniform within thisarea. With the Amperite velocity, specialarrangements of orchestras are, there-fore, unnecessary. The high pitched in-struments will be properly reproducedirrespective of their position.

The variation in sound intensity withdistance from the microphone is 70%less with the Amperite velocity thanwith any pressure type microphone.

With the above in mind and the uni-form reproduction over the entire audiblerange without peaks, the new SR -80 isideal for studio work and its increasedoutput makes it very desirable for remotework.

New Universal OscillographA new inexpensive Oscillograph with

a variety of control panels, which areeasily interchangeable so that the Os-cillograph will exactly fit field or in-dustrial and laboratory investigationsand a wide selection of galvanometersfor producing up to eight records, isannounced by the Westinghouse Elec-tric & Manufacturing Company. Amongother features 1) the new type PA Uni-versal Oscillograph offers simultaneousviewing, the phenomena can be viewedwhile photographing, 2) daylight loadingholder which can use 5, 10, or 200 ft. of5" wide film or paper, and arrangedso exposed portion can be cut off at anytime desired with.ut disturbing supply,:1) wide range of speed by variable speed

motor, 4) interchangeable galvanometersand vibrators and 5) automatic type IAcycle starting time. The complete Oscillo-graph with controls exclusive of film -holder measures 25" long x 8%" widex 9%" high and weighs approximately50 lbs.

New Trimmer Condenser

Because the drifting of trimmer con-denser capacities has at times seriouslyinjured radio receiver sensitivity, theresearch department of Solar Manufac-turing Corporation has worked on thisproblem for several months to determinecauses of drifting. A new small cermaticbase trimmer just brought out by thiscorn ern is designed to eliminate drifting,as constructional features which mightcause drifting have been eliminated.Under the pressure of average settings,the top plate has anchorage at both frontand rear. The new trimmer is called the"Perms -Set", and is supplied ill max-imum capacities of :10 mud. to 180 nunf.

A Tough Order(Continued from Page 19)

tribution through the mails was elimi-nated, distribution through drug storeswas substituted.

While the Commission under the lawhas no authority to censor programs itis charged with the duty to see that sta-tions are operated for the pubic wel-fare and the courts have held that theCommission can take cognizance ofbroadcasts inimical to the public health.swealrrissem4frealemirreffewedipasepee

SOSTO THE RESCUE

A Wireless Operator Tells theInside Radio Stories of Great

Marine DisastersBy KARL BAARSLAG

THIS thrilling book tells, largely In theirown words, the radio operators' stories ofthe great sea disasters from the days of

Jack Binns and his CQD to Alagna and Rogersof the Morro Castle. The author. himself aship radio man, spent years of research andnow tells the stories brother radio men haveplaced at his disposal, many of them neverbefore fully revealed. Introduction by Capt.Felix Riesenberg. Illustrated. $2.60

OXFORD UNIVERSITY PRESS, 114 IifthAve. N.Y.

Mention Commercial Radio when answering Advertisements

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OUTUCE PROGRAMME UNES AA LEGENDMOVING COIL !MICROPHONE

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WIPE RANGELPJOAPCAKCR

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MIXER AMPLIFIERMIXER IS ENAMEL SHOWN) THNSICE0

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PROGRAMME SWITCHING A 1(

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New A. -C. Mains OperatedSpeech Input Equip-

ment at Lausanne

(Continued from Page 17)that a peak voltage of 3 volts is not ex-ceeded. The loudspeaker amplifiers areall fitted with volume controls.

In places where microphones are in-stalled, the monitoring service is cut offas soon as the associated "A" amplifieris connected at the Control Desk. The re-lay used to cut off the loudspeaker alsocuts off the intercommunicating telephone and puts the "busy tone" on theline.

In the two listening cabins for thespecial modulation control of a musical

r

I-

M.A.

STUDIO MICROPHONES

STUDIO

fLOUDSPEAKER

ECHO ROOM

Fig. 4-Overall Circuit Layout

programme, wide range loudspeaker com-binations are used. These are fed from aspecial power amplifier through dividingnetworks which split the frequency rangeinto two bands which are then reproducedby the low -frequency and high -frequencyunits.

A special feature of the installation isan arrangement whereby the announcermay introduce his microphone on theprogramme at any time without the in-tervention of the control operator. Thisfeature is useful, especially when agramophone recital is being given; itthen enables the entire programme tobe handled by one man, since volumecompression has already taken place

-when the original recording was made,and no further modulation control is

MIXER

PA A.S A

M MICROPHONE (MOVING COIL TYPE)M.A MICROPHONE AMPLIFIER 12 db GAINA 'A' AMPLIFIER 30- 70 db GAIN.P A SMALL POWER AMPLIFIER 20-40 db GAIN.A.S.A ANTI SINGING AMPLIFIER 12 db GAIN

MIXER

therefore necessary when the record isbroadcast. The large studio also in-corporates an announcer 'a position sothat announcements may be made fromthe studio itself.

Future IterelopinentsIn the main amplifier room, provi-

sion has been made for a second row ofseven amplifier racks which should pro-vide adequate space for apparatus re-quired in connection with future exten-sions. With a view to future televisiondevelopment, the building has been elec-trically screened by means of verticalcopper wires inside the walls and aroof of copper sheeting.

The Societe Romande de Radiophonieis now in possession of the largest andmost up-to-date studio building in

'Switzerland. Great credit is due to thejudgment and foresight of the Build-ing Committee presided over by Mr.Baud. chairman of the Swiss Broad-casting Co., and in particular to the ar-chitect, Brugger, for the provisionof many features which will prevent thebuilding from becoming out of date durto future developments in radio broad-casting technique.

TO SWITCHING &CONTROL POSITION.

Fig. 5-Eeho Circuit Schematic

JUNE, 1935 Page Twenty-one

Sending is EASYEasy -WorkingWith the Genuine Martin No. 6

New VIBROPLEXReg. Trade Marks: Vibroplex ; Bug;

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The smoothest. easiest -working bug onthe market. Easy to learn. Easy to oper-ate. Makes senclingleasy.

MARTIN JUNIOR

$10

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Black orColored 46,

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el 9VA -

Special Martin Radio Bug-Extra large.Specially Constructed Contact points fordirect use without relayBlack or colors. $25

Why be misled by offerr of anything but the GEN-UINE MARTIN VIBROPLEX? MARTIN JUNIORembodies all standard Martin features and quality.Like Improved Martin but furnished on 2% poundblack japanned base. Remit by Money Order or Reg-istered Mail.

THE VIBROPLEX COMPANY, Inc.825 Broadway, New York City

Cable Address: "VIBROPLEX" New York4M01141=.011.,141WONIMMIP04.11M1.1.0.1.1MMIMPA

New--DUCOS--NewPAPER CONDENSERIN NEAT BAKELITECONTAINERSCOST NO MORE THANCHEAP PAPER CONDENSERS

Patents Pending

OIL IMPREGNATED600V -1000V -1500V

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Manufactured by

Dumont Electric Co.453C Broome St., New York City

CLASSIFIED ADSCOMMERCIAL RADIO will accept ..las

sifted advertising at the special ratecf five cents per word.

Remittance in full must accompanycopy. Closing date for classified adver-tisements is the 15th of the month pre-ceding publication.FOR SALE-Radio Model Vibroplex,

heavy contacts, $10.50. Like new.Guaranteed. John Morgan, 54 HardingDrive, Glen Oaks, Rye, N. Y.ONE NEW SET Van Nostrand Mathe-

matic books: Arithmetic, Algebra,Trigonometry. Calculus and Home Study,4 vols. $3.50, list price $7.00. LD., careCommercial Radio, 7 W. 44th St., N. Y.

Page Twenty-two

Md.04M14

CQ,CQ Amateurs!Build the

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SUBSCRIBE NOW !YOU who have been fol-

' lo-wing our bookshould know better than oth-ers that an issue lost leavessomething_ to be wanted.NOW is the time to makesure of receiving every issue.

Send $2.00 at once to"Commercial Radio"

7 West 44th St.New York, N. Y.

A COUPLE OF "KINKS"From KBTM

By H. L. KIMSEY, Chief Operator

Here is something we use at KBTM.We have a rather high gain amplifier inour studios, so instead of using a remoteamplifier, we just use a Mike to linetransformer to couple our W. E. doublebutton Mike to our remote line. I usefour volts on the Mike at about 12 milsper button. This used up to distances ofseveral blocks from the studio, and bythe way we have been using a cuing sys-tem almost exactly as described by TedBinder in your April issue of CommercialRadio. It works out very nicely and isused with above coupling transformer. Itis much easier than carrying a separateradio to listen to the program.

Here is another one used here atKBTM. We have constructed a lightingantenna grounded switch. I have seenseveral small stations with snitches thatwere not of the low pass variety. Mostof them were mounted on state or com-position material, and in most cases wereeye sores to the station. Ours is of theceiling type with ropes attached to theblade to do the swit hing. We use twothree inch stand-off insulators for theends of the switch, and a five inch stand-off insulator for the center. These weremade by the Johnson Company. Theyare mounted on a fourteen inch piece ofhard wood and a twelve inch of strapcopper is used for the blade. The switchclamps are connected from a doublethrow, single pole switch. The ropes areconnected to the ends just inside theswitch jaws. This makes a very pleasinglooking switch and is a good :nsulator.

NEW RULE

On May 1st, the Federal Communi a-tions Commission adopted the followin7rule:

No one serving in the FederalCommunications Commission on orafter July 1, 1935, shall be permit-ted to practice, appear, or act as anattorney or agent in any case, claim,contest gr other proceeding beforethe Commission or before any divi-sion or agency thereof, until twoyears shall have elapsed after theseparation of the said person fromthe said service.

Mention Commercial Radio when answering Advertisements

Your Subscription se$

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MAGAZINESClubPrice$2.25 Radio News2.00 Radio Craft1.75 Radio Engineering9.25 Proceedings of the Institute

ClubAlone Price$2.502.502.00

Commercial RadioCommunication & Broadcast

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of Radio Engineers 10.00 Radio 3.00Short Wave Craft 2.50 QST 2.50

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Electrical Engineering 12.00Radio Amateur Call BookRadio Music Merchant

4002.00

General Electric Review 3.00 Radio & Electric Sales 1.00Electric Journal 2.00 Radio World 3.00Bell System Tech. Journal 1.50 Radio Retailing 2.00

Club Price

SystemPopular Mechanics

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$3.002.25

GENERAL MAGAZINESClub Price Regular

American Magazine $2.50American Boy 1.00

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Good HousekeepingJudge

Regular

$2.501.50

$1.35 Popular Science 1.50 Aero Digest 3.00 Ladies Home Journal 1.00

2.50 Review of Reviews2.25 Red Book

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Boys' Life

3.004.001.00

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3.75 Scribners 4.00 1.75 Colliers Weekly 2.00 Motor Boating 3.002.25 Science & Mechanics 2.50 2.75 Current History 3.00 National Geographic 3.50

3.75 Scientific American 4.00 Delineator 1.00Nations BusinessPictorial Review

3.001.00Saturday Evening Post 2.00 Esquire 5.00 Today t,00

Cosmopolitan 2.50 2.25 Field & Stream 2.50 True Story 1.50

1141041M0.=.0.1=101110401111111111MNDIMIH 04.10001.1If there are any magazines on which you wish a special quotation not listed above, or any group of magazines-

write us. We have a limited number of catalogues of magazine subscription prices and will send for the asking whilethey last.

1.04111041114,4=9.1.0114MOMM04,1=1 no.o,anwo.now14,41.104M.1141,.,,...M.O.M.,4111.04MH..M.04=1,04.1.1M004M141401.01M14.11,4,4=001M10.11M1.0411,11..14....DO NOT SEND CASH. SEND CHECK OR MONEY ORDER

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CQ MAGAZINE COMPANY, 7 CITYWEST 44TH ST.. NEW YORK1lcation Comm( rein( Radio who, answering Advertisement,

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