January 1942

V 40 I.* JANUARY 1942

of . eng!rieering and manufacture radio communication, indLstrial applications eectjç. AL

U. S. FDREST SERVICE AuToriAtIL: 111.1

STATION OPERATING IN 30-4C M R 'IC IC -1

'NAP' - *".4tOk

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- .

, `1.4 4, rf. 4,0".

- - low - 411r..-t 441V- 4 - - 17174 'w,04016 " -

, - 4 (7-- 1 s 1.4

ste , 1°' leb doesn the e tbodyngs tell me

is an ideal source for transformers to specifications

With improvements in materials, structural design, and production methods, UTC is producing, today, transformers which even a year ago would have been considered impossible.

As a typ cal example of such development is a transformer recently supplied to a customer for one cycle operation having the following characteristics:

Primary impedance IO ohms. Impedance ratio 75,000 : I. Secondary inductance 250,000 Hys. Self- resonant point above 7 cycles. Weight under 8 pounds.

In additicn to t4,ese difficult characteristics, this unit operates at -160 DB signal level and hum shielding was developed to provide negligible hum pick -up to signal ratio.

MAY WE ASSIST Y OU IN YOUR PROBLEM?

The same design experience and engineering ingenuity shown in the above example can be applied to your application. May we have an opportunity to cooperate?

150 VARICK STREET EXPORT DIVI SiO1`: i00 YARICK STREET NEW YORK, N. Y. S: AR AB" electronics A McCRAW-HILL PUBLICATION

CONTENTS-JANUARY, 1942

FOREST SERVICE RADIO Cover A field communication station of the U. S. Forest Service. Extensive use is made of radio in patrolling the forests and fighting Tres

30 -40 MC MOBILE RECEIVER, KEITH HENNEY by H. K. Lawson and L. M. Belleville 22 Editor An a -m receiver developed for use by the U. S. Forest Service under conditions heavy of ignition interference. Absolute signal values under I µ -volt Donald Fink Beverly Dudley a may be received on motor vehicles not equipped with spark plug suppressors Managing Editor Acting (on leave) Managing Editor BALLAST TUBE VOLTAGE REGULATORS, by S. Gordon Taylor 26 W. W. MacDonald Craig Walsh Automatic voltage regulation can be obtained in a number of devices by the use of a simple Associate Editor Associate Editor inexpensive iron wire ballast tube

M. L. Mattey J. M. Heron SUPER -CARDIOID DIRECTIONAL MICROPHONE, by B. B. Bauer.. 31 Assistant Editor Assistant Editor An acoustical phase- shifting network is used to produce the effect of the combination of a velocity microphone with a pressure microphone Harry Phillips Art Director PHOTOFLASH SYNCHRONIZER TESTER, by P. A. Marsal 34 A device for measuring the time from the closing of the synchronizer switch to the instant when the camera shutter is opened to the desired degree

SELF -CONTAINED MARINE RADIO UNIT 36 The high speed of producton of the Victory cargo fleet required the development of a quickly -installed radio transmitter and receiver unit such as the one described here H. W. MATEER Publisher RECTILINEAR RECTIFICATION APPLIED TO VOLTAGE Wallace B. Blood INTEGRATION, by S. S. Stevens 40 Sales Manager Non -linear rectifiers are combined in such a manner to produce rectilinear rectification and are used in conjunction with a condenser charging circuit to provide a voltage integrator with linear response

COMMON MISAPPLICATIONS OF GASEOUS TUBES, by W. W. Watrous and D. E. Marshall 42 A discussion of the do's and don'ts of gaseous tube application

TRANSMISSION LINE GRAPHS, by Bernard Salzberg 47 Contents Copyright, 1942, by Graphs for the determination of the characteristics of parallel wire or coaxial McGraw -Hill Publishing Company, Inc. transmission lines McGRAW -HILL PUBLISHING COMPANY, INC. DEPARTMENTS JAMES H. McGRAW Founder and Honorary Chairman CROSSTALK 21 THE ELECTRON ART 80 Publication Office REFERENCE SHEET 47 TUBES 94 99 -129 North Broadway, Albany, N. Y. U. S. A. TUBES AT WORK 50 NEWS OF THE INDUSTRY 100 Editorial and Executive Offices NEW BOOKS 62 NEW PRODUCTS 102 330 West 42nd St., New York, N. Y., U.S.A. INDEX James H. McGraw, Jr., President TO ADVERTISERS 114 Howard Ehrlich, Executive Vice President Mason Britton, Vice President B. R. Putnam, Treasurer ELFI,TRONICS, January, 1942. Vol. 15; No. 1. Published monthly, price 50c a copy. Allow at least ten days for change of address. A11 communications about subscriptions should be addressed to the Director of Cir- D. C. McGraw, Secretary culation, 330 West 42nd Street, New York, N. Y. J. E. Blackburn, Jr., Director of Circulation Subscription rates -United States and possessions, Mexico. Central and South American countries. $5.00 a year, $8.00 for two years, $10.00 for three years. Canada (Canadian funds accented), $5.50 a year. $9.00 for two years. $11.00 for three years. Great Britain and British possessions 36 shillings for one year, 72 shillings for three Cable Address: years. All other countries, $6.00 for one year, $12.00 for three years. Entered as Second Class matter, August 29, MCGRAWHILL, New York 1936, at Post Office, Albany, New York, under the Act of March 3. i879. BRANCH OFFICES: 520 North Michigan Avenue, Chicago; 68 Post Street, San Francisco; Aldwych House, Aldwych, London, W.C. 2; Washington; Member A. B. P. Member A. B. C. Philadelphia; Cleveland; Detroit; St. Louis; Boston; Atlanta, Ga. Rifid //, / //, %/ Tests Demand CENTRALAB Switches inrour Communication Systems

Don't hold up defense development! Centralab NOW offers a kit of parts of high grade Steatite Ceramic Switch Sections and necessary metal parts which will withstand the 200 hour Salt Spray Test, for the immediate construction Important Features of in your own laboratory of efficient highest Centralab Selector Switches quality SELECTOR SWITCHES (over 200,000 1. High grade Steatite sec ^.ions, vacu- electrical combinations available). um wax impregnated. Whether it is the first 2. Contacts, clips, eyelets and rivets "hand made" transmitter heavily silver plated. or receiver, or whether they are rolling off 3. Complete index mechanism and your production line; if you equip them with operating shafts of stainless steel. these CENTRALAB Selector All brass parts heavily nickel Switches they plated to withstand 200 hour salt will pass every test for they are "BUILT FOR spray test.

ABUSE ". For the first or thousandth unit . . . 4. Standard indexing 30° and 90° specify CENTRALAB SELECTOR between positions. Also available SWITCHES. in 60° on special request. Send for special bulletin on 5. Sections 3/16" thick. Mounting Selector Switches for Defense. center of sections 1- 9/,16 ". Over- all widest dimension 1 -7/8 ".

CENTRALAB Division of Globe -Union Inc., Milwaukee, Wis. 6. Choice of 2 to 11 positions per section. 7. Kit consists of 61 Steatite Sections of various switching combinations, 36 indexes complete with hardware for assembling 1 to 6 sections per index.

2 January 1942 - ELECTRONICS s° syntheticsynt . aper Papers . clear p Moat tcacMt of oll- OIL. kind <.IERAL e unstable. crystal-clear tracing with riyé ß11Y fI M treated cl cote' ties t, dries eral a decal °%rlf never In prcduc`Lte tcads to treated trans4arencY simple, wth sly e P r°° $ setmjr uP dust, age-proofs9 maties tree r ts orsa With ate. remark- orTec.icns, a sh2rp bluconstantc A,B NENE -:to wa= agent under handling. oa,ve No ,i', artizing to standup h 1f and rc 4.alites . Laboratories- owl,' all zblen'-`''nsñin Kg`E ment tracing all ttne working w ir ed ere 00 has develop tMs t. ul y perrr Of w s wanted-and initcl}' own produ- CNE is nade , yrh:t.ristics ijélf cu.) ou-: un- PAN t thew Cealer, chenticallY paper'- anite rags-treated a.IENEyoa' &E Papers treated pl;_ e crystal-c r -fry A Ask °°ur F+ OleßsilY rancid fiber d. Ted brochure oxidizes oil becomed opaque long n and chEml- stable. stable an rliTE-3 g with vegetableturn Ye11oW íoci- wri u for nr-p. and with l.ysica.ly not ate. cli3 P wt o awlf n with synthetic ' 6LBAlE1`E terns _terous 'lll/l' lose and a E,. calif irert. ljttttl(. OI ÉSgEß CO. become FEL w J. dite, wi_1 aage. has KO`_ REAI KEVfFEW tot MoNt a ALBAVENE or .s--r p "po_th" tañes ink cHICA60ANBtiS r 9ual y that ease 5 LOS sya -d "tooth es :itb FR+f+G -clear waa. ane ra- eras crYStal and o that fe a oil and from In ert. ße b .tifullo .ransparen-. pLBANITEsolid, freechemically pencil thetic an _ p ò FltyslcallY new sta.noaee isunot a degree { this Atbanen aih canes agent will or arentizi ;tsashlr clbe orne brittle affected by ate, otidise icß nsparefCY. Inge

RE:J.U.S.O 1ç&EI L R C THE STABILIZE '-4/1/a4 aW-a/ t%e COMPENSATION FOR FREQUENCY DRIFT IN HIGH FREQUENCY COMMUNICATIONS

ERIE CERAMICONS

FREQUENCY drift in communications They are made in 9 standard coefficients oscillators is caused by physical and ranging from +.00012/ °C. to -.00075/ °C. electrical changes that occur in various Insulated Ceramicons are available in ca- components. While it is possible to elimi- pacities from 1 mmf. to 375 mmf.; non - nate the drift in each component, such a insulated units from 68 mmf. to 1100 mmf. procedure involves considerable redesign Erie Resistor has developed special and probable increased cost of each electronic equipment used in producing component affected. It is far easier to corn - and testing Ceramicons that insures a high pensate for the total drift by introducing degree of uniformity of characteristics in an Erie Ceramicon in the resonant circuit these units. This uniformity is essential for having a temperature coefficient of the dependable compensation in high frequen- opposite sign and of such a value as to cy communications equipment for Military offset the undesired drift. and Naval uses. A revised data sheet giving Erie Ceramicons are small ceramic - the characteristics of Erie Ceramicons has dielectric condensers with definite, linear, just been published. Copies will be sent and reproducable temperature coefficients. to interested engineers on request.

ERIE RESISTOR CORP., ERIE, PA. LONDON, ENGLAND TORONTO, CANADA.

RESISTORS SUPPRESSORS SILVER MICAS CERAMIC,ONS PLASTICS

4 January 1942 - ELECTRONICS PERFORMANCE CHARACTERISTICS OF LAPP RADIO INSULATORS ARE DEPENDABLE FACTORS Lapp's contributions to radio broadcast engineering are recognized as highly significant in the advance of the science. Practically every development of antenna structure design, for example, has been worked out with the cooperation of Lapp engineers. Since Lapp developments have been wholly pioneering in nature, it has been necessary to maintain complete testing facilities. In the Lapp laboratory is the usual equipment for 6o -cycle electrical, mechanical and ceramic testing. In addition is complete equipment for determining characteristics of units at radio frequency -heat run, radio frequency flashover, corona determination and capacitance. For mechanical testing (lower picture), a 1,500,000 lb. hydraulic testing machine is used -for test of new designs, and for

proof -test of every insulator before shipment. _A

In the construction of new broadcast equipment-or the modernizing of old -the safe bet is to specify "insulators by Lapp." Descriptive literature on Lapp antenna structure insulators, porcelain water coils and gas -filled condensers is available on request. Lapp Insulator Co., Inc., LeRoy, N. Y.

FOR SECURITY IN ANTENNA STRUCTURE INSULATORS .

ELECTRONICS - January 1942 STABILITY PLUS

Marine condenser built to withstand severe vibration.

oPERATING on an "All Out For Victory" basis Hammar- lund is producing precision variable condensers for every Defense Communications Service. Many of these condensers are comparable to laboratory standards, though produced in

great numbers on a mass production basis.

THE HAMMARLUND MANUFACTURING CO., INC. 424 -438 West 33rd Street, New York, N. Y. IllMllTE sTets urnapaeî,a9if Rheostats Resistors Tap Switches Chokes

Rheostats Resistors Tap Switches

is ready for the job o I Ohmite ahead. Expanded factory facilities are operating day and night with increased momentum to produce more units, more quickly for In- dustry and the Armed Forces, for the planes, tanks, ships and other equipment needed for Victory. The design and construction of Ohmite Rheostats, Resistors, Chokes and Tap Switches insure utmost dependability. The wide variety and extensive range of 1.011fi . types and sizes in stock or special units make it easier to answer your exact needs. Ohmite engineers are glad to help you. Send for 96 -page Catalog and Engineering Manual No. 40. Most complete, helpful guide in the selection and application of resistance units. Write on company letterhead for your copy.

OHMITE MANUFACTURING COMPANY, 4816 Flournoy Street, Chicago, U.S.A. pp bbv1EI TE ,yoi cffFS wir* rive ,v,q riaN

ELECTRONICS - January 1942

4 1,6

SHORT LEFT- LEGGED COWS FOR

GRAZING ON HILLY TERRAIN

IT IS in the production of special, hard-to-get relays and timers that have never been made before, for exacting jobs that have never been regularly for everything from newly developed done before, that Dunco engineering excels. aviation jobs, to tank jobs and a host of other Hence the simile. military uses, as well as for countless indus- While cows to the above specifications are trial applications. probably a biological impossibility, relays Whatever your Relay or Timer need - designed to meet almost equally unusual speci- whether standard, special, or "extra special," fications are pretty much an everyday oc- it pays to come to Dunco- first. Whatever the currence at Dunco. We're producing these type, Dunco means dependability!

RELAYS AND D unto TIRING DEVICES STRUTHERS DUNN, INC., 1326 CHERRY ST., PHILADELPHIA, PA. DUNCO TYPES 30 AMPERE 6 AMPERE (midget) SENSITIVE LOW VOLTAGE, HEAVY CURRENT, D.C. INSTRUMENT CONTROLLED MECHANICAL LATCH -IN (Electrical Reset) MERCURY CONTACT TELEPHONE AUXILIARY LAMP CONTROLLING POLARIZED OVERLOAD MOTOR REVERSING SEQUENCE, RATCHET TYPE CLOSE DIFFERENTIAL TIMING ... and countless "Customer Specials" designed or adapted to meet your exact specifications. 8 January 1942 - ELECTRONICS These sensitive instruments can be used to record any quantity indicated by the movement of a tiny mirror. They are the most sensitive recorders known Typical Characteristics (Recording Galvanometer) which do not employ electrical amplification of the Range -0 to 1 microampere quantity being measured. Resistance -approx. 2280 They are very useful for recording values such as ohms grid currents of vacuum tubes, small photo -tube Response Time -approx. 4 sec. currents, and small thermocouple voltages for low - Dimensions -5.41 by 16 by temperature records. Measurements can also be 9'/a in. telemetered. Scale Length -3 A in. Eoth portable and switchboard types are available.

TO RECORD ONE MILLIAMPERE Direct- acting A new direct - current instrument in the Type CD Recorders Type CD line offers a convenient means for recording plate Typical Characteristics current and other small current values in lower ranges (Milliammeter) than were previously possible. Range--0 to 2 milliampere The chart is driven by a Telechron motor thus Resistance-approx. 1800 dependable operation. The instrument is ohms assuring Response Time-approx. 2 lightweight, easy to use, and can be obtaired in sec. both portable and switchboard types. Dimensions -5A by 12 by This Type CD instrument is one of a comple_e line 91'6 in. for recording current, voltage, watts, power -factor, Scale Length -4 in. and frequency.

New Inkless Recorder --ype CF TO RECORD MICROAMPERES Typical Characteristics ( Milliammeter) - Here is a new line of direct current INKLESS recorders Range -0 to 1 milliampere - available in high- resistance voltmeters and low - Resistance -approx. 16 ohms Response Time-approx. 3 sec ammeters, milliammeters, and microammeters *. resistance Dimensions -8;6 by 10A by 5344 in. A -c voltmeters and ammeters are also available. Scale Length -3A in. These low -cost instruments are well suited for electronics work because of their low power consumption. Exceptionally small and lightweight, they are readily portable. Provision is also made for wall mounting. The microammeters are available down to 125 microamperes, full scale.

r urt er in ormation a..ut t ese or of er in ruments in a comp e e Inc. ca e nearest G -E office, or write General Electric Company. Schenectady, New York. HEAARTERS FOR E '.CTRICAL MEASUREMENT GENERAL ELECTRIC

ELECTRONICS - January 1942 9 gART

THE SURN RECE,11

DELICATE though the job a radio tube must perform, upon its ruggedness depends the infallibility of the set it serves. And how importantly such ruggedness counts today - in the many wartime applications of radio.

But fortunately there is a tube that has what it takes to withstand the devastat- ing shocks and concussions of battle - a tube especially engineered to stouten the heart of sure reception. That's the Sylvania Lock -In Tube -with from which it derives its name. its connections welded, not soldered - with its fewer joints, its all -glass Here alert, progressive Sylvania engi- header, and its vastly improved mount neering has scored again -and at a time support - each as important as of vital import in the history of the exclusive lock -in lug radio's service to America.

HYGRADE SYLVANIA CORPORATION New York City EMPORIUM, PA. Salem, Mass.

Also makers of HYGRADE Incandescent Lamps, Fluorescent Lamps and Fixtures. 10 January 1942 - ELECTRONICS What it takes to keep 'em flying

Back of the safety record of America's

leading airlines is the world's most

dependable radio equipment. Signifi-

candy, Cornell -Dubilier capacitors are

used by all these major airlines both

in ground station and aircraft commu-

nications. Here is convincing proof

that C -Ds have what it takes - extra dependability not only to "keep 'em

flying ", but to meet your most exacting

capacitor requirements.

CAPACITORS MAY LOOK ALIKE BUT...

There is extra long life, extra uniformity and dependability built into C -Ds. Next

time you specify capacitors, look for the Cornell -Dubilier seal of experienced en- n1ilYñ gineering. And get the hidden extras at PART St _..._ ts.ACV. RECEWEk " rt11XtLtAiY REOElY_R ' . _ no extra cost. Send for catalog. Cornell - ` Dubilier Electric Corporation, 1006 Ham- ilton Blvd., South Plainfield, New Jersey. MI(:RiPnvn ` MEA YS TS UTAL.RY ®A' New England Div., New Bedford, Mass. Loop LOOP AMPLI LOCI, ORI\ AZ MUTA

VÀJiIier

ELECTRONICS - January 1942 II Communication in War Not only for the Army and Navy; not only for the 130,000,000 People; but for the COMMANDER IN CHIEF as well, RADIO is the accepted vehicle for local, national and world -wide dissemination of thought.

PER SUPERIOR TUBE COMPANY, NORRISTOWN, PENNSYLVANIA

To the RMA, and specifically the Radio Tube Manufacturers To the Electronics Industry as a whole, Superior Tube Company says:

WE believe it to be our duty to use to the utmost the greatly extended facilities in our Cathode Sleeve Department, where we produce Seamless and Lockseatn types to the full extent of raw materials that may be available to us. Not a thing has been left undone to save ounces of scrap, wherever possible. To us, 16 ounces of Nickel means 5,000 Sleeves, and a million of them above the usual output means someone's plant can run longer.

dìtt: Tubing from %" OD down...SUPERIOR Scamless in various "141" analyses.WELDRAWN C=ÉRAvjWelded and drawn Stainiess. BRAWN Welded and drawn NM "Monet" and "Inconel ". SEAMLESS and Patented LOCKSEAM Cathode Sleeves. 12 January 1942 - ELECTRONICS AS THE DOCTOR PRESCRIBES . .

AmerTran modulation transformers and re- ac'ors, o'1- immersed type, for large broadcast transmitters.

AmerTran RS plate transformers and reactors, oil -immersed type, for all large Just as the skilled installations. pharmacist compounds the drugs called for by AmerTran W plate the doctor's prescrip- transformers and reactors for all small tion ... so AmerTran's and medium installa- skill, experience and tions. quirements and conditions. facilities combine to For more than 40 years produce Transformers AmerTran has supplied to that exactly meet your all branches of the radio AmerTran and communications industry all types of prescription (specification). transformer equipment regularly required. Transformers are engineered mechanic- This equipment is manufactured for all ally and electrically to render dependable sizes of installations and in large or small service . . . they can also be designed quantities. Let us quote on transformers specifically to meet your particular re- for your needs.

AMERICAN TRANSFORMER CO., 178 Emmet St., Newark, N. J.

Manufactured Since 1901 at Newark, N. J. Ati EQTim Built to your Specifications ELECTRONICS - January 1912 13 INJECTION ,MYCALEXMYCALEX PROPRTIESE AND PES

WHAT IS INJECTION MOLDED MYCALEX? It is a ceramic material, composed of ground mica and a special glass, having unique heat and electrical insulating properties, and ranking above all other insulators for certain applications because of a combination of features possessed by no other material.

ADVANTAGES OF INJECTION MOLDING G.E.'s development of a technique for molding Mycalex by the injection method has resulted in several advances: A. Ability to produce more intricate shapes. B. Closer tolerances in molding. C. Reduction or elimination of finishing and machining operations. D. Molding of holes in part.

SPECIAL FEATURES a OR Incorporation of inserts often simplifies or eliminates assembly operations.

i. Mycalex may be drilled, filed, sawed O or polished. Thin sheets may be punched. Parts may be used as inserts in phe- . : : nolic moldings. Metallic fittings can be cast over ends of rods to form strain insulators without softening, blistering or otherwise affecting the Mycalex structure. PROPERTIES TYPES OF MYCALEX 1. High dielectric strength 2. Low power factor - -For Injection Molding 3. Prolonged resistance to electric arcs « 2801 General purpose grade for all 4. Chemical stability; no deterioration with injection molded parts. Used where age. mechanical strength is of primary importance. S. Dimensional stability; freedom from war- page, shrinkage, etc. u 2800 Lower loss factor, lighter weight 6. Imperviousness to water, oil, and gas. and smoother finish. Unaffected by changing atmospheric 7. Resistance to sudden temperature changes. conditions; has superior stabilityy of power factor after Low 8. coefficient of thermal expansion, prolonged immersion in water. 9. Ready anchorage of metallic inserts in Write Section J -1, G.E. Co., 1 Plastics Ave., material during molding operation. Pittsfield, Mass. PLASTICS DEPARTMENT GENERAL ELECTRIC

I I January 1942 - ELECTRONICS Radio ... all out forr Victory Research and invention have placed radio in the first line of battle COMMUNICATION -rapid communi- The Radiomarine Corporation of America cation-is a vital necessity, on land, at has equipped more than 1500 American sea and in the air. RCA research and engi- vessels with radio apparatus and is com- neering developments in both radio and pletely engaged in an all -out war effort. electronics are strengthening -and will fur- * * * ther fortify -the bulwarks of our communi- Radio broadcasting is keeping the Ameri- cations system. At Princeton, New Jersey, can people informed accurately and up -to- the new RCA Laboratories -the foremost the- minute. It is a life-line of communica- center of radio research in the world -are tion reaching 55,000,000 radio sets in homes under construction. and automobiles. It stands as the very sym- * * * bol of democracy and is one of the essential International circuits, operating on short freedoms for which America fights. The and long waves, have made the United National Broadcasting Company -a service States the communication center of the of RCA -and its associated stations, are world. Today, R.C.A. Communications, fully organized for the coordination of war- Inc., conducts direct radiotelegraph service time broadcasting. with 49 countries. * * * * * * New radio operators and technicians must Production of radio equipment is essential be trained for wartime posts. RCA Insti- for news and timely information, for mili- tutes, the pioneer radio school of its kind tary and naval communications, for dis- in the United States, has more than 1,200 semination of news among foreign coun- students enrolled and studying in its New tries. The "arsenal of democracy" has a York and Chicago classrooms. in range and effi- * * * radio voice unsurpassed took its place RCA Manufacturing Com- When war came and America ciency. In the front, radio was workers have pledged them- on the widespread fighting pany's plants, with radio men and radio promise," in production At the Ready ... selves to "beat the to answer the call to duty and delivery dates of radio equipment needed facilities prepared "in the most tremendous undertaking of our for war and civilian defense. * * * national history." American life and property at sea are being safeguarded by ship- and -shore stations. I'NRRInENT Had io Corporation of America RADIO CITY, NEW YORK The Services of R(' A: RCA :Manufacturing Co., lne. R('A Laboratories . R.C.A. Communications, Inc. National Broadcasting Company, Inc. Radiomarine Corporation of America . RCA Institutes, Inc.

ELECTRONICS - January 1942 Contact springs employing any of these forms can be furnished.

T FORM B T FORM A FORM C J FORM D L FORM E

'"Arg Iutossnnx,,....,».

High voltage pile -up insulation withstands heavy break - down tests. i' Contacts of rare metals and special alloys, "over- Springbush.ng insulators all" welded to nickel made Ey a patented silver springs. proc- Multiple Plug-I, ess from Bakelite rod. type mounting Illustration also shows makes for easy twin contacts. maintenance.

Yéiu^- ?rarr'.fiúéi.Ez ` Double arm armature RfSiS3'rA!Ií:'t' ',i!;í.i!J r;iiA'iS. with stainlesssteelshaft °"' in marine brass yoke t°'' 4. CLAP6r. r" r' 4.e q s: can be furnished.

Clare Type C d. c. Relay with Plug -In Mounting Data regarding turns and resistance appears on all coils - protected by transparent covering. THIS Clare Relay CAN Take the Place of Many

For engineers who want a rugged multi- 3 The relay shown has high voltage spring pile -up trial usage. For heavy duty service a double arm ple contact relay that permits innumerable insulators of special heat -treated Bakelite which per- armature assembly, util.zing a stainless steel shaft mits punching without contact arrangements which will enable cracks or checks, has minimum operating in a marine brass yoke, as illustrated above, them cold flow properties and low moisture absorption con- can be supplied. The heel piece, coil core, and arma- to design their product to a smaller size, re- tent. The pile -up assembly is locked together under ture assembly of this relay is magnetic metal, care- duce the number of relays employed, and fa- hydraulic pressure. Projecting wafer insulators which fully annealed. Where sensitivity and timing are provide cilitate relay maintenance, we suggest the use creepage path of V," between contact springs important factors, a special magnetic metal is recom- can be furnished. The entire assembly withstands very mended to provide permeability. of the Clare Type C d.c. Relay with Plug -In heavy break -down tests. Mounting illustrated and described here. Coils are carefully wound to exact turns 4 The spring bushing insulators are made of Bakelite 6 on precision machines. Lead -out wires are securely soldered. This relay is ideal heavy rod under a patented process. These strong, hard, long for duty service Coils impregnated a special varnish wearing bushings are essential where heavy contact with are available. in machine tools, welding timers, Data regarding resistance, number automatic pressures are employed, where vibration exists, or of turns, type of wire appear on as weighing equipment, and similar products. heavy duty service is desired. the coil illustrated. The coil is protected with a transparent acetate covering. It is particularly adapted for use in elec- 5 The armature assembly of this relay is standard for light duty and stand tronic control devices. It renders excellent will up under ordinary indus- 7 The relay illustrated is arranged for octal base plug service in sequence control and interlocking mounting which makes for easy service and replace- operations. Wherever unusual arrangements ment. Other types of mounting such as individual of relay angle bracket, strip or panel can be furnished. Easy to control, ordinarily impossible with handle slip -on Bakelite covers for individual mounting ordinary relays, are desired, it can be used or metal covers for group mounting can be supplied. advantageously.... The reasons for this versatility are as follows: These features, plus the fact that all Clare Relays are á Its standard spring assemblies may embody any carefully designed, well- manufac- combination of the five combinations illustrated. It tured from the best available materials, and may be equipped with as many as 20 springs per pile- precisely adjusted, assure you that this Clare up with two pile -ups per relay -a total of 40 spritsgs. "Custom to Type d. c. Relay will reduce your over -all Think what this means! -Built" a relay cost, simplify your designing problem Prize- Winning Design 2 It can be provided with twelve different standard - and insure you better and more dependable or special -types and sizes of contacts which are The Carson Electronic Micrometer which measures to performance. Clare engineers are ready welded to the nickel ... silver springs by a special proc- .000025" without pressure, won the recent Electrical ess. The contacts are made from precious metals and at all times to assist you in developing a relay Manufacturing Design Award. This unusual instrument alloys, such as silver, palladium, palladium-iridium, specifically "custom- built" to meet your is fitted with a Clare Relay. Its manufacturer, Instru- tungsten and elkonium. They can be furnished in sizes requirements. A "blueprint" of your prob- ments Specialty Company, Inc. Little Falls, New Jersey, from .062" silver, rated at I ampere, 50 watts, to lem will bring our suggestions. In the .1875" tungsten, rated at 4 amperes, 100 watts. Vari- says: "Clare engineers deserve credit for having de- ous types may be incorporated in one relay. Also fur- veloped this special relay... We have had to re -order meantime, send for the Clare catalog and nished with Micro or other snap action switches which this relay several times ... have been well satisfied with data book. C. P. Clare & Company, 4719 CLAREcarry a higher rating. its ability to duplicate its initialRELAYS performance." W. Sunnyside Avenue, Chicago, Illinois. "Custom - built" Multiple Contact Relays for Electrical, Electronic and Industrial Use 16 January 1942 - ELECTRONICS FORMICA -wif/s Glass C/fÁ Base, (FIRER 61453)

FABRICS of glass impregnated with phenolic resins are used to produce several recently developed grades o Formica to meet special conditions. They provide a material better in heat resistance than other types of Formica - a material especially adaptable for instance for motor slot wedges where heat may reach 350 degrees. The material has low moisture absorption and very little cold flow. Another grade with Fiberglass base has been developed for flexibility and -tracking" or arc resistance. And a third provides an efficient low loss electrical material at radio and high frequencies. This type of Formica is available in the form of sheets, tub ing and rod from which a wide variety of parts may be machined. If you have a problem that requires a material with these properties ask for samples:

The Formica Insulation Co., 4661 Spring Grove Ave.,Cin.,O. ôRMIci **BIG PRODUCTION FOR DEFENSE** More than 75 per cent of the production of the Formica factory is now going for defense - mechanical and electrical parts for airplanes, signaling systems, and electrical circuits of all types as required for war equipment.

ELECTRONICS January 1942 17 TO COMBINED MAD X?!1 DEFENSE PRODUCT _ _,,.,:.,,,

ram

-.. wes.:C`

Lnd pr c ductïoand pro , n.gi1 eers n.,ent B -M - Je%Jrj R'g_ ruction and defense t R-B- electrical a vi-al ly' engineer- i.s 1prod Engi- needed relay f R -B-M neer- rola because facilities- Lei far prob- was selected QfgYtt n3rtic[I hugelsuge on your_ e lati ins neing staff recomm neers make lems.

high Receivers are and T1teY are TransmittersTransmi Pense. Mobile National De plants also Motorola FM for ordnancece p Defense f products tcarton t. the list ,,,y For Mo- for two e4uiPmequipment. departments.artmentb' used e.haniz Ppolice P Ü. S M and defense the this vital fire. ambulance in they serve Relays torola use% Co . M AN ,- \3' M 14 CoRpoiL,,TIo WIRE 1NI,lA:A. RhAY sx 30 LOGANSPOTZT' TYPE

January 1942 - ELECTRONICS "`\\\\\\\\ \\\\\.\\\\\ ~\\\\\\\` \ \\\\\\\\\ \\\\`\\ \\ \\ 7/4W.,,BOLDERLESS PINSandSOCKETS ÎSave up to 50% of installation time by sub- stituting bench -tool opera- speed in assembly with CANNON'S New Solderless Pins tions for laborious hand - GREATER wiring on aircraft parts and Sockets that's our answer to the call for increased aircraft production. during final assembly. Always first with developments in the Cable Connector Field ... such as (1) Elimination of all machine screws, (3 ) Shell polariza- Eliminate soldering of Split Shell construction, (2) 2 pins and sockets ... tion, (4) Spaced end belt rotation ... and now CANNON announces to the all wires are attached by aircraft and allied industries, "SOLDERLESS PINS AND SOCKETS." "crimp- seal" method, ap- No basic departures from approved proved by Army and Navy. CANNON designs ... but another forward- Pins and sockets are in- looking CANNON IMPROVEMENT in dividually locked into Cable Connectors to speed aircraft output. bakelite inserts by an ingenious new Cannon de- Tooling now in progress. Preliminary velopment, after crimping. information available on request. Pro- Solder -type terminals Typical Cannon AN9574 duction planned within 90 to 120 days. MAY be used for Plug Assembly emergency replacement in field or substituted in bench production, with proportionate time -saving. CANNON

Electric Development Co. 1942 PLU © Cannon CANNON

CANNON ELECTRIC DEVELOPMENT CO. 3209 HUMBOLDT STREET, LOS ANGELES, CALIFORNIA Blvd. Eastern Sales Office: Empire State Building, New York City Chiraóo Agency: Kelburn Engineering Co., 6001 W. Jackson

ELECTRONICS - January 1942 19 NATION -WIDE SERVICE THROU H You Can Put Your Finger On Parts 253 SELECTED DISTRIBUTORS Like These At Your Mallory Distributor

Mallory makes ft easy for you to get essential are well trained and able to help solve your prob- electronic parts ... the ones you need for: lems. Want a rectifier ? Condenser ? Resistor ? Test or experimental work in your engi- Switch? Electronic hardware? Your Mallory Dis- neering department, research laboratories, tributor is the man to see. pilot plants or proving grounds. For handy reference, you'll want the Mallory Replacements in plant equipment. catalog ... perhaps several copies for members of your organization. This catalog gives terse, factual Efficient operation of some device yowl:din information otiory parts used in the aero- to put into production. nautical, automotive, electrical, geophysical, radio Distributors carefully selected by Mallory -253 and other industries. Use this catalog as your of them -are ready to serve you promptly. These buying guide ... depend on your Mallory Dis- conveniently located Mallory Distributors keep tributor as your supplier ... for your industrial adequate warehouse stocks. Their representatives electronic needs.

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20 January 1942 -- ELECTRONICS What Can I Do?

SINCE that Sunday morning when havoc swooped Efficiency in production is not the responsibility of as we all put to useful EvERfrom the skies upon Honolulu, a new question has a few. It can be achieved only been churning about in millions of American minds. It purpose every minute of our time, every ounce of our is this: What can I do to help my country win this war? energy, and every pound of our materials. This insistent question has pushed aside all matters This responsibility of industry is the more vital be- of personal interest. From now on, individual wants and cause of what has happened to the business of making wishes must give way to the paramount needs of the war. There was a time when success in war was chiefly nation. We all accept that. We have undertaken a huge a matter of well -trained, well -disciplined armies and job. Or, I should say, we have had a huge job thrust competent leaders -when men were everything. In those upon us. And unless we see that job through successfully days, military strength was a matter of strong battalions it won't much matter what any of us may want. and able generals. Both still are vital. But today military That job is to win this war. might is essentially mechanical might. Modern war is No longer are we trying to prepare for a war that we an industry just as much as a factory or a railroad. In may get into. Today we are trying to win a war we're the first World War, mechanical equipment was rela- already in -and in up to our eyes. Nothing that any one tively simple and limited. But today the special equip- of us now can do to help himself can get him very much ment of war and the expert skill needed to use it spell if it does not also help our country to win this war. the difference between victory and defeat. is I am sure that those who read these words will find We Americans are not expert war -makers. That many things to do. Some will enlist in the armed ser- why we must expect to suffer grievous losses before we vices. Some will become active in civilian defense. Some can win substantial gains. We do not have military will labor to relieve distress in their home towns. Some training and experience ready to hand when we need will work with organizations set up to serve the men at them. Neither do we have, ready for action, enough of the front. Each can and will find something he can do. the machines that are so essential to modern warfare. But this insistent question "What can I do?" goes So, when it becomes necessary to fight for our lives, beyond the individual and his personal service. It re- we must start from scratch. And today, after a year's echoes through the offices and the shops of every effort, we still are not ready to trade blow for blow with American business concern. And what I have to say enemies who for years have schooled their leaders, here is not directed toward individual effort. Rather trained and disciplined their people, and organized their is it intended for the men and women of American industries to make war. We shall need more time to industry who make that industry a living part of develop our strength. And while we are doing that, we American life. Today they are asking themselves: What must expect reverses. can industry do? Or better still, what must industry do But there is a brighter side to all this. For it follows if our country is to finish the job it has started? that if we are granted this all- important time, the Those of us who work in and with American indus- change in the method of warfare is right down our alley. try have one supreme obligation. We may feel very The greater importance of mechanized equipment plays patriotic; we may be willing to serve "in any capacity :" straight into the hand of the world's greatest industrial we may be willing to sacrifice ... if necessary. But if nation ... if there is one thing America does know, it is we fail to meet that one obligation, we shall fail our industrial production! Our industries know how to pro- country in its time of need. duce. They have the skilled manpower. They have the THAT SUPREME OBLIGATION IS AN HON- organized facilities. Beyond any doubt, we can produce win victory that we must win EST DAY'S WORK, EVERY DAY, FROM EVERY all that we need to the - if only we are given the time. MAN, EVERY WOMAN, EVERY MACHINE... . OF THE ARMED IT IS AS SIMPLE AS THAT! THE FIRST RESPONSIBILITY IS TO GAIN THAT TIME FOR US. And that goes for all of us, whether we are engaged FORCES OF INDUSTRY in civilian production or working directly on the wea- THE FIRST RESPONSIBILITY pons of war. American victory can be won only through IS TO USE TO THE FULL EVERY SECOND OF the productivity of American industry. THAT TIME IN PRODUCING THE WEAPONS THE ARMED FORCES NEED TO WIN THE gent cooperation that the men in the shops can give. ULTIMATE VICTORY. INDUSTRIAL PRODUC- It calls for inventive ingenuity to match that of a nation TION IS THE KEY TO VICTORY. BUT IT MUST which has produced some of the world's outstanding BE BIGGER PRODUCTION AND FASTER PRO- technical genius. For this is a war of technical pro- DUCTION THAN WE EVER HAVE KNOWN. ficiency. But above all, it calls for a new devotion to the day's Heretofore American industry has worked to produce work. For so long as we are at war, the day's work will more of those things which make our lives more enjoy- determine our country's security. able. Today it must divert much of its energy from the Whatever may be our material resources and our products of peace to the weapons of war. technical skill, however resourceful our management, This change sets up a new yardstick of industrial per- however broad the scale of our effort, industry cannot formance. In time of peace we measure production effi- measure up to its prodigious responsibility if any of us ciency in terms of money saved. From now on, we must shirk the day's work. Right there is where we find the measure efficiency chiefly in terms of time saved. For one thing we all can do -the one thing that is within the plane, the tank, the gun, or the ship that is ready the power of each of us. when it is needed to win a victory, is worth a million times more than the one that is delivered too late to THAT ONE THING IS SIMPLY TO DELIVER avert a defeat. AN HONEST DAY'S WORK WHEREVER WE Everyone knows how short we are of some materials ARE CALLED TO SERVE. HONEST WORK and machines. But our most tragic shortage is the short- WILL WIN THIS WAR. LOAFING WILL LOSE age of time. So whatever we may waste in the days IT. THE SHOWDOWN WILL BE WHETHER ahead -and unhappily we are bound to waste plenty- HITLER CAN DRIVE HIS PEOPLE TO WORK let us never forget that the most deadly waste of all is HARDER THAN WE ARE WILLING TO WORK. the waste of time. THERE IS NO ONE TO DRIVE US. WE MUST Time wasted never can be replaced. No one ever has DRIVE OURSELVES! discovered a substitute for time. If we would avoid the Is that so much to ask? It is all our country asks of waste of this irreplaceable ingredient of victory, we is all men must must use every minute of it effectively -while we still us, the men of industry. It that the who have it. work the guns and tanks in the field ask of us. It is all planes That goes for us all. It goes for the man or the woman that the men who work our ships and our ask of us. us ships, the tanks, at the bench, at the desk, at the counter, in the field, or "Give the planes, the guns, the and all rest of our tools," they tell us, "and we'll in the executive office. It goes for the politician as well the give you victory means so much to us all. But, as for the business man. It goes for the humblest and the that the most powerful. A nation at war cannot carry dead- in the name of that victory, give them to us quickly - QuIcxr.Y- QUICKLY!" heads. It cannot spare a square foot for any one who will not pull his weight. Is that, I repeat, too much to ask of us? In this war, nothing short of complete victory can save the liberties of us all, rich and poor, employer and To help American industry achieve ever -higher stand- employee, haves and have -nots alike. The price of that ards of efficiency has been the traditional mission of victory is the labor, the loyalty, and the devotion of McGraw -Hill for three-quarters of a century. Normally every last one of us. Winston Churchill said it well for that effort has been directed toward higher efficiency in the British people. You know how he said it. I need the business of peace. But, as in the first World War, not repeat it. twenty -five years ago, it now is directed toward efficiency As this imposes upon American industry, its owners, in the business of war and in every department of its managers, and its responsibility workers, the gravest American effort that can contribute, directly or indi- they ever have assumed. If our country is to survive as a rectly, to the achievement of victory. free nation, American industry must rise to re- that And to that mission, I here pledge every resource of sponsibility. If our country should fall, it would fall this company, its publications, its books, its staff, and because American industry fell short of the need. It every service it is qualified by experience and training to would be another case of "too little and too late ". render to American industry, now enlisted in our com- This grave responsibility calls for the keenest man- mon cause. agement industry ever has known. calls It for unremit- That is what we of McGraw -Hill can do. And that is ting research to make most the of our resources. It calls what we shall do to our utmost. for the reduction of waste to a record minimum: that goes for waste of time, labor, and material. It calls for keeping our machinery working as near to full capacity as we can contrive. It calls for the highest rates of unit production we ever have known. That will mean skill- ful coordination by management and the most intelli- President, McGraw -Hill Publishing Company, Inc.

This message is appearing in all McGraw -Hill industrial and business publications, reaching over a million readers. ELECTRONICS .... KEITH HENNEY Editor .... JANUARY, 1942

CROSS TALK

a ABOUT OURSELVES . Now more subscribers would take advan- come, the publisher either makes that we are at war, it is vitally neces- tage of these questionnaires to tell the profit or he takes a loss. sary that every operation in which we editors what they want. Editors can Other readers have trick ideas about editors and readers engage be aimed (and do!) guess at what readers want how they wish the contents to be ar- at the business of prosecuting this con- to read but much better results can be ranged-no articles "turned over" into flict to our advantage. This means, im- had if the readers help by contributing the back of the book; all articles on a mediately, that waste effort must be their own desires. given subject placed in one part of the To us this means In a recent survey of reading habits, issue so they can be filed together, all completely eliminated. text that ELECTRONICS must be aimed at one answer indicated that the sub- advertising in one section and the you, the reader. Material which the scriber felt the quantity of the editorial in another, and all sorts of ideas which reader does not read represents wasted contents had been reduced recently. would be swell for some and terrible effort, paper, printing time and ex- This is not the case. Since 1937 the for others. All of these ideas have been pense, etc. To you, the reader, this editorial contents have increased considered; and many of them have means that you must help us not only steadily. At the same time the number been tried out. It is a fact, however, the paper but you must help of advertising pages has increased too, that present -day magazine arrange- by reading of us select the editorial contents, help and apparently it is this increase which ments suit most of the readers most us edit and publish it. has given the reader the impression the time, and that must be the aim. of sug- ELECTRONICS was founded to be a that the number of editorial pages has Your editors want all sorts "campfire of council" to all those who gone down. gestions for improving this service. are vitally concerned with designing, It is as important to the reader as to Contributed articles, criticisms, even manufacturing and using electron tube the publisher that manufacturers of an occasional kind word (!) are always apparatus. For nearly 12 years ELEC- equipment tell their messages in the greatly appreciated. Many plans are 1942, and as these TRONICS has been written by its readers advertising pages of any publication. in the making for and its editors for their mutual benefit. For if there were no advertising the plans unfold we hope to get closer and This must continue; and without beat- reader or the publisher would have to closer to you 17,300 readers. cost of publication. The ing around the bush any more the edi- bear the entire UHFI . . . In a recent conference tors hope that every reader will con- publisher has no interest in maintain- of college professors called together to sider ELECTRONICS as a medium by ing a paper just for the hell of it, nor provide plans for courses on uhf, ques- which he, individually, may contribute has he any philanthropic motives in tion of terminology came up now that his bit of information to all others publishing. If there were no advertis- the ultra -ultra high frequencies are similarly engaged. No matter how ing in ELECTRONICS, the average issue being used. It was decided to use the the small a contribution to saving mate- would cost considerably more than terms UHFI ( "ultrahigh frequency in- rial or labor or time, or to making ex- reader pays now, especially since .many deed") for these super -short waves. isting equipment last longer or operate readers take advantage of reduced sub- Speaking of initials -what do you betterthat information may be worth scription rates by buying more than suppose WRGB stands for? You're a gold mine to other electronics people. one year at a time. Under these con- wrong-they're the call letters of G -E's To find out what our readers want in ditions there would be no publication. commercial television station. the way of editorial contents, we make Each of the 17,300 paid readers to continual surveys of reading habits and ELECTRONICS (September issue) bears FREE ... Copies of Mr. McGraw's reading preferences, by mail and by a certain portion of the total cost-of statement, "What Can I Do ? ", appear- actual contact with readers through publication., The revenue frpm adver- ing in this issue are available in reprint our editorial research and circulation tisers is tlie, only other source of in- form for those who want them. No field men. The results of these ques- come. We have no, membership dues, charge will be made for small num- tionnaires are of inestimable value to no angels! If there is a difference be- bers of reprints, larger numbers will be the editors; and our only wish is that tween the total cost and the total in- supplied at cost. Mobile 30 -4o Mc Receiver

A receiver, for mobile use, and receiving amplitude -modulated signals, designed to compete with frequency modulated systems from standpoint of immunity to pulse -type noises. May be manually tuned, or spot- frequency tuned

INABILITY to obtain adequate a background for the requirements tivity in the vicinity of 1 µv coverage abso- with mobile equipment of this unit. Of the 4000 radio tele- lute. Usable sensitivity in employing this case amplitude modulation, as phone units in use by the U. S. is not considered as being realized opposed to frequency modulation, is Forest Service over 90 percent are under ideal laboratory conditions, in practically all cases the result of of the strictly portable type falling but rather under actual inferior road test receiver performance in the in a weight class of from 6 to 21 conditions and through electrical presence of heavy ignition interfer- pounds complete with all accessories noise encountered in heavy traffic. ence. The U. S. Forest Service Type and power. During the past five KU -R receiver herein described re- years the trend of forestry radio has Primary Design Considerations lieves this condition to such an ex- been toward a more intensive use of The requirements of such a re- tent that many amplitude modula- those frequencies lying between 30,- ceiver are: tion communications systems now 000 and 40,000 kc. Of the 2,000 u -h -f 1. Provision for manual tuning being discarded with heavy invest- radiophone transmitters in use, only over the range of 30 to 40 Mc as ment loss can be made to serve ade- 1 percent have a power output in ex- well as crystal controlled spot fre- qúately. This receiver will not provide cess of two watts. The maximum quency operation. completely noise -free reception nor power of this group is 20 watts. 2. Compact structure to permit in- is it directly comparable to fin in Quite naturally there is an urgent stallation in space restricted by spe- this respect. Its performance is, how- need for communication with mobile cial fire fighting tools and devices ever, so outstanding as compared units, such as fire tank trucks, in all types of motor vehicles. to mobile a -m receivers with con- forest highway patrolmen, and su- 3. Low primary power consump- ventional noise limiter circuits that pervisory personnel on large proj- tion to permit prolonged use with- it will undoubtedly assist in solving ect fires. The limiting factor in out constant battery charging while many of the problems arising from the successful application of mo- the car may be temporarily immo- limitations imposed by ignition and bile ultrahigh frequency equipment bile in fire service. other sharp pulse type noise. The to this job has, up until this time, 4. High sensitivity to fit into the Type KU -R receiver permits actual been the lack of a satisfactory re- general scheme of low power trans- use of absolute signal values below ceiver. mitter operation. 1 or when used on cars without With the normally low signal 5. Broad acceptance band to mini- spark plug suppressors or other fields provided by the portable mize criticalness of manual tuning forms of ignition noise treatment. units, it is essential that the mo- and loss of signals due to all sources An occasional noisy generator re- bile receiver provide usable sensi- of drifting. quires correction by electrical filter- ing and cleaning, but beyond this no special preparation is required to make a workable installation. A 111 convenient i and simple measure of + 60 btained- useful sensitivity is the signal 8 Low limit input >° d¡, de bi value required ise (Optimum} to produce a 4 to 1 l change in the audio power output 4 '1;140 when modulation is increased from N + o, 0 to 30 percent. Measured by this o v method the average sensitivity of a >.2 ó 20 U group of 25 receivers was 1.4 µv. d Q (See editor's note at end of article.) 0zo Before entering upon a discussion 01 o 100 1,000 10 000 100,000 of this receiver it is of interest to Signal Input -,u.V review briefly the general trend of forestry radio equipment to provide Ideal and realized characteristics of the noise silencer circuit 22 January 1942 - ELECTRONICS for the U. S. Forest Service

By H. K. LAWSON and L M. BELLEVILLE U. S. Forest Sricc Radio Laboratory Portland, Oregon

6. Freedom from pulse type inter- U. S. Forest Service type KU -R ference, particularly ignition noise, Mobile Receiver. Top to bottom, speaker, r -f tuning head, originating in both the forest car amplifier unit. Note universal and in other traffic. mounting clamp which permits These requirements appear gen- steering -column or under -dash erally conventional and relatively mounting of r -f tuning head. universal Bottom cover of amplifier unit with the possible excep- serves as mounting plate and tion of the combination of tunable entire unit may be removed for and spot frequency operation. s e r v ice by releasing trunk The two requisites for maximum hasps sensitivity in a receiver are; the highest possible signal -to -noise ratio and adequate gain to deliver full audio output with no input other than the first circuit noise. A triode first detector is used in this receiver to keep the conversion noise at the lowest possible value. One stage of r -f amplification adds further gain in signal -to -noise ratio and assists in suppressing image interference. It should be noted that the r -f and first and second i -f tubes are of the sharp cutoff type. Among several considerations dictating this choice, the g,,, /Ik* noise factor of merit was of major importance, a higher ratio of gm /Ik being available in tubes of the sharp cutoff type. Further, where power con- pression. Some of the better receiv- yet such communication is relatively sumption is a consideration the va- ers indicated high sensitivity as incidental to their entire field of riable-mu tube is at a disadvantage. measured in the laboratory and at usefulness. Consequently it would The saving in plate current by the the same time developed acceptable not be economically sound to at- use of sharp cut -off tubes in this noise suppression at relatively high tempt a replacement of all equip- receiver amounts to approximately signal levels, but all failed to per- ment merely to provide a more ideal two watts. Better a -v -c characteris- mit use of their maximum sensi- mobile system. Second ; frequency tics are also realized with tubes tivity in the presence of heavy igni- modulation technique has not ad- which do not require a high bias tion interference. vanced sufficiently far to date to per- for cutoff. Although fm may be considered mit design of a reliable portable Careful investigation of the field to be the ultimate answer to this unit that can compete in size, weight, of commercially available receivers problem there are two outstanding cost and over -all low power con- failed to disclose a unit with all reasons that immediately rule out sumption with the portable units essential features combined. The this system for U. S. Forest Serv- now in service. most generally available types were ice application. First; the Forest A thorough investigation of avaiI- of fixed tuned design intended for Service now has on hand some 2,000 able mounting space in various types police service. In this field there u -h -f radiophones, all amplitude of cars and trucks, resulted in a de- appeared to be a lack of high usable modulated and all serving a useful cision to break down the receiver sensitivity and good pulse noise sup- purpose in forestry communication. into two small units, plus an ex- Any one of these may be called upon ternally mounted speaker. To avoid * Ratio of traneconductance to cathode current. See RCA Review, April 1941, page 518. to communicate with a mobile unit, mechanical complications arising ELECTRONICS - January 1942 23 from an attempt to eliminate rub- desired to avoid using such devices. all of the above factors, the fre- bery backlash from remote mechani- The i -f amplifier is substantially quency of 1600 kc was selected pri- cal tuning, a complete r -f tuning flat over a band of 50 kc centered at marily for the advantage of stability head was designed to be mounted 1600 kc. This choice of bandwidth so necessary in mobile equipment. in the same manner as the conven- was influenced by the necessity of By far the greater part of the tional remote tuning mechanism. receiving some of the older type work on this receiver went into the The common flexible shaft method modulated oscillator transceivers design of the noise silencer. A si- of mechanical tuning becomes satis- which are still in service. A rela- lencer of practically the same design factory over the relatively wide tively wide acceptance band also as appears in the present model was range of 30 to 40 Mc only when ex- serves to minimize the effect of nor- incorporated in one of the test re- tremely high gear ratios are em- mal drift of various crystal con- ceivers at the beginning of this ployed. Such an arrangement results trolled transmitters. Although all work. Due to what appeared to be in slow and tiresome manipulation current transmitting equipment of excessive space requirements and to tune over the entire band. the U. S. Forest Service employs circuit complications, the much simp- crystals having a temperature coeffi- ler and more compact series diode Radio- Frequency Tuning Head cient of four parts per Mc per de- limiter was employed in the next The r -f tuning head of this re- gree C or better, none of these units test receiver. Analysis of the series ceiver contains the signal r -f am- are temperature controlled, and diode limiter indicated that this type plifier, detector, tunable heterodyne when operated on a mountain peak, of circuit could be expected to ac- oscillator, crystal oscillator, and fre- may encounter temperatures vary- complish everything that might be quency multiplier. ing from near freezing in the morn- expected from any form of limiter. An eight- conductor cable and sep- ing to over 100 degrees by mid- A receiver employing this circuit arate i -f transmission line connect afternoon. gave excellent results under re- the tuning head with the larger unit. stricted conditions but the design The eight -wire cable carries pri- would not stand the test of use in The Cover Picture mary power from a switch on the heavy traffic. A battery- operated automatic relay head unit to tube heaters and plate It was finally realized that the di- or repeater station is shown in op- supply, plate voltage in ode for tubes the eration. It utilizes the 30 to 40 Mc limiter could do an acceptable tuning head, squelch control and region and ties 5 forests into a job of silencing only up to the point audio level control. The intermedi- central fire and weather forecasting where interference became strong ate frequency of 1600 kc is fed to office in the State of California. It enough to actuate the avc. When the i -f unit through a length of 64- also serves as a repeater for mobile this condition is reached, which is ohm flexible concentric transmission equipment in the forest in which it is usual in the presence of heavy igni- line. Careful design of the 1600 -kc located. The longest circuit covered tion noise, the signal will be reduced inter -unit line coupling transformers is 200 miles. For reasons which our by action of the automatic volume eliminates line resonances and per- readers will understand, the loca- control until it is lost in the residual tion of these installations mits the use of any length of high cannot be noise. published now Resulting aural effects range quality line found necessary. from an increase in the staccato Transfer from manual tuning to noise to a complete blanketing of crystal controlled spot frequency The requirement of a 50 -kc band the signals, depending upon intens- operation is accomplished by a rela- necessitates three i -f stages for ade- ity and rate of ignition. The noise tively rough setting of the tuning quate gain. It can be shown that for silencer herein presented is based on dial to a pre -marked point and a given bandwidth and stage gain variations in the type of silencer first throwing the "manual tune - spot the intermediate frequency can be proposed by J. J. Lamb (see QST frequency" toggle switch on the tun- varied between fairly wide limits. Febuary 19, '36). To the best of our ing head to the spot frequency po- With available i -f transformer Q's knowledge the most important of sition. The panel switch serves a 50 -kc bandwidth can easily be had these variations first appeared in a merely to transfer plate voltage from at an intermediate frequency of 5,000 receiver manufactured by the Pear - the tunable oscillator to the crystal kc. Such an amplifier would have son-Delane Company. controlled oscillator and tripler. It excellent skirt selectivity. The same This form of limiter not only is evident that the tunable oscillator gain and bandwidth can also be ob- serves as a noise silencer but also and the fixed frequency tripler are tained at a much lower frequency by protects the avc from the overload- in a measure interlocked through proper adjustment of circuit Q. This ing produced by strong impulse in- their common coupling to the de- shift will produce several results. terference. This silencer incorpor- tector grid. Special attention to me- First, the image response will be ates two major variations in the chanical layout and simple but ade- closer to the signal frequency; and fundamental circuit proposed by quate shielding have minimized the second, skirt selectivity will be re- Lamb. First, the output of the noise interlocking between the tripler and duced. This latter factor may be rectifier is impressed on the injector tunable oscillator to a point where it either an advantage or a disadvan- grid of the third i -f stage through is not apparent at any position of tage depending upon the application a coupling condenser. This prevents the manual tune dial. The use of an of the receiver ; third, stability with the d -c component in the output of entirely independent spot frequency drift of trimmer condensers due to the noise rectifier from appearing heterodyne source eliminates the temperature change or vibration, on the controlled stage and thus necessity of switching in high fre- will be improved at the low fre- eliminates the blocking normally en- quency circuits where it is usually quency. With consideration given to countered with this type of silencer. 24 January 1942 - ELECTRONICS The second circuit variation is made 7F7 + possible o by the first, and consists of s an automatic threshold control circuit which maintains the bias on the noise rectifier at the proper value now-- 7 L7 for optimum silencing with 47Kn4V 75 K12 varia- '0-0000N-JA tions in signal level. H 0.0005 7F To The fundamental operation of the IK12 L. 0 O0 6D+ silencer may be briefly described as 38 V 0 follows : The output of the second 00005 Bot i -f amplifier feeds both the noise ¢7Kn View controlled third i -f amplifier, and in- Crystal 60Ò06L dependent noise amplifier in parallel. U0 34 /Kn The output of the 6J7 noise ampli- 5K12 0.01 fier is rectified by one of the 7A6 ) 11- diodes, and any pulses or irregu- f- - Bottom To heaters i larities in this rectified output are Vibrator View -- fed through the coupling condenser Bottom 0.01 to the injector grid of the 6L7 third View i -f stage. These pulses serve to block this tube for the duration of the rectified noise voltage and thus pre- -13V 7L7 vent the rise of the original noise 006s impulse to full amplitude in its out- ô 270Kn 49 V 0.01 r put circuit. The foregoing consti- 40012 0005 IKn tutes the fundamental actions of this -1F S ñ 1001(12 circuit, but without additional de- J vices and elaborations the system re- i mains unworkable. J To produce a workable circuit, it U is necessary to adjust automatically the threshold of rectification so that 1K12 modulation peaks are not rectified 18V 1 and thus cause to clip and distort, 6J7 and to maintain this threshold of rectification as closely as possible to 001 72 V these peaks to prevent the rise of 001 An ideal curve for unwanted noise. 1 K1 J this condition was plotted by applying manual control to the rectifier 00/ for various signal levels from 1 µv to /50 1 volt. The nearest possible duplica- Kll 0.000/ was --1 tion of this curve then obtained Noise Rect. 1 with one section of the dual triode 470 K.12 7F7. The slope of the plotted curve produced by this tube can be con- 7A6 trolled largely by selection of the 470 Kn -J proper proportion of a -v -c voltage. AVC Rect. The starting point or height of the Noise Threshold curve can be further controlled by Control 10 4112 means of the variable positive potential available at R,,,. By careful selection of the values of the com- 01 /00 V in these circuits, it is pos- ponents 7F? sible to obtain almost ideal control 470K12 -0.7V 2M12 of the noise rectifier, and accord- ingly to realize optimum silencing at all signal levels. /M12 470 K12 7B5 25 V-- 0004 /5K11

Squelch Circuit 0.01'13 The audio output of the receiver 0004 is effectively silenced by the opera- Speaker Q tion of a d -c amplifier between the a -v -c bus and the grid return of the (Continued on page 98) Complete circuit diagram of the Forest Service receiver ELECTRONICS - January 1942 25 Ballast Tubes as Automatic Voltage Regulators

FOR many years resistors cap - both inductive and resistive loads, lamps which have regulatory charac- able of automatically varying can be incorporated as built -in com- teristics when employed in series their value with variations in the ponents of the equipment to bè con- with a load. Curves of Fig. 2 show current flowing through them have trolled or can be used externally to the vastly greater effectiveness of a been employed as self- adjusting cur- control existing equipment. ballast tube. For reference purposes rent and voltage regulators. In spite Their chief limitations for certain the linear voltage -versus -current of this, their numerous advantages applications lie in (1) a lag of a few curve of a perfect fixed resistor are not as widely recognized as they seconds in responding to any appre- is also included. The nominal ballast should be. It is therefore the pur- ciable variation in load or supply and curve is that of the minimum regu- pose of this article to present perti- (2) reduced effectiveness as supply latory characteristics likely to be nent information on their character- regulators where the load is other found in a wide variety of ballast istics and applications. than a substantially constant value. types. The curve of the 3AS shows To avoid possible confusion it is In many cases these limitations are the greater effectiveness more well to mention here that this type readily overcome, in other cases they nearly representative of ballasts de- of resistor is properly termed a even prove advantageous, as will be signed for use with loads of 1.0 "ballast" or "ballast tube ". In re- demonstrated in applications dis- ampere or less. cent years these terms have some- cussed later. times been carelessly (and always Figure 1 shows the nominal con- Comparison to Tungsten and Carbon erroneously) applied to the fixed trol characteristics of a typical bal- Lamps dropping resistors incorporated in last tube. It will be noted that with In Fig. 2 all characteristics are many ac -dc receivers. According to a 200 percent increase in applied plotted on a percentage basis to RMA terminology such usage of the voltage (above the rated threshold more directly show their relative ef- terms is incorrect and misleading. value) the current change is limited fectiveness. In Fig. 3 are shown Because of the widely prevailing 10 percent. Even to more important, actual voltage-current measurements belief that effective automatic regu- over a greater part of this voltage for a number of different lamps and lation is necessarily expensive, there range the characteristic is substan- ballasts. The ballast curves are ex- are many electrical and electronic tially flat with the result that the tended somewhat beyond their nor- designs whose functions, under ab- current change is negligible. mal rated operating ranges to normal or subnormal supply voltages, Fundamentally, show this type of regu- overload characteristics available for are impaired by failure to include lator is approximately a constant - use over such regulation. Actually short periods of excessive the ballast current device, increasing and de- dissipation. tube will completely satisfy the re- creasing its resistance automatically quirements of many of these designs to compensate any tendency to and yet add little to their cost. change in the current flowing The Ballast Tube per se Ballast regulators offer many ad- through it. It is immaterial whether The ballast tube consists of a re- vantages aside from their extremely this tendency is developed as a resistance element of iron wire sealed low cost. In many applications they sult of changes in the supply voltage in a glass envelope containing hy- will maintain supply voltage con- or in load resistance. In the former drogen or helium. Its regulatory stant within one or two percent un- case the regulator varies its own action is based on (1) the high tem- der conditions of relatively wide line voltage drop to offset supply -voltage perature coefficient of resistance of voltage variation. They function changes, thus keeping constant the the iron wire, which causes large with equal effectiveness in both a -c voltage applied to the load. If the variations in resistance for rela- and d -c circuits and, having no mov- load resistance varies, the regulator tively small changes in the current ing parts, are free from mechanical will vary the voltage applied to the flowing through it, and (2) the cool- troubles. They are compact in size load to the extent necessary to main- ing effect of the gas used which and light in weight, yet are capable tain the current constant. stabilizes this action and provides of controlling loads up to 1000 watts Not infrequently one sees refer- a means for shaping and extending or more in certain types of applica- ences to the self -regulating charac- the regulatory characteristic. tions. They are suitable for use with teristics of tungsten and carbon When currents of lower value than

26 January 1942 - ELECTRONICS Well known among radio receiver engineers for their current regulating characteristics, ballast tubes may be employed as inexpensive regulators for many other useful applications

By S. GORDON TAYLOR

1.0 100 sa. r 10% iñcreóse in I currenf in i J E . 1i 0.8 : i through ballast i ,

,,V I 80 5. i--, l e, l? // " ; Y 1 ------i- l g 0.6 5i6,11'. m _------t 60 `A ó/ 0-I Vt`` ;i;t J" s / 7-* I 200 % increase in É' (>1 J I 2,0.4 I. vo/tage across ballast 40 ó Ell s e V° ¿rci/,o =C2. o c 20 E .- j 00 5 10 15 20 25 30 35 40 0 20 40 60 80 100 Voltage Across Ballast Tube -Volts Percent of Rated Voltage

current characteristics of carbon Fig. 1- Nominal characteristics of ballast tube. For a 10 percent Fig. 2- Voltage- re- change in current through the ballast, a voltage change of 200 and tungsten lamps compared with those of percent occurs sistance regulators. Neither type of lamp offers much advantage over a straight dropping resistance whereas the regulator tubes provide regulation over a wide voltage range

Fig. 3- Constant - current characteristics of three typical resistive regulators compared with other types of resistors often recommended for voltage dropping purposes 1.0 {e ßP5 0.5 Pe III I____. Amperi/e 8, 0.8 Fe

t;` Fig. 4- Voltage distribution in a typical a -c radio receiver utilizing a resistive regulator to tnsure reasonably constant supply voltage despite wide variations in the line \ il watt Cotbo^ 0 0.4 k- Narmo/ voltage to ' , 88 volt primary 90 mPgrile 3A5 of load trans- E To former h fi /s. 0.3 ó 100 To Voltae (I.o T° 88v 0.2 applied , Surplus line j etc. to load voltage absorbed in Typical A G. regulator Receiver Power 0.1 I l , tube Transformer

a!° 140 50 60 70 80 90 100 110 1 70 80 90 100 110 120 130 140 20 30 40 Applied Voltage Voltage, Volts

ELECTRONICS - January 1942 27 the range for which the ballast is flow, from the threshold value to a -c or ac -dc receivers. Substituted designed are passed through it there another value, for example, 10 per- for the original fixed dropping re- will be some heating of the wire but cent higher, will result in a 200 per- sistors in such receivers, these pro- the resistance change will be grad- cent increase in the voltage drop vide the added feature of controlled ual, as indicated by the steep slopes across the regulator. Voltage thres- drop. They are available in sufficient at the beginning of the three regu- hold values can be supplied as low as variety to meet the requirements of lator curves of Fig. 3. At some par- 0.3 volt or as high as 80 volts. In normal load values from 0.2 to 1.5 ticular value of current, determined many types, including the three amperes. by the design of the ballast, a criti- shown in Fig. 3, the range of volt- cal point is reached beyond which age change is actually wider than How to Specify Ballast Characteristics any in will 1 3 further increase current the to ratio mentioned. Where a ballast tube is to be in- very cause a rapid change in the Ballast tubes are made in differ- corporated in a production design or resistance wire. of the At another ent physical sizes, depending largely where even a single unit may be re- higher and less critical value the on the amount of energy to be dis- quired for some individual applica- resistance once change more becomes sipated. Inclosed in a tube envelope tion, it is the practice to list the more gradual. It is between these equivalent in size to a 6L6G tube actual requirements of the design and submit these specifications to the regulator manufacturer. In- cluded in the data should be maximum and minimum values of : (A) Voltage variation of supply (B) Maximum permissible voltage variation at load (C) Required drop across ballast tube (A minus B) (D) Load current with voltages shown at (B) Manufacturing processes are such that samples can be made up speed- ily and at negligible cost.

Examples of Ballast Application To illustrate how this works out, the case of a manufacturer of airplane instruments is cited. One of his instruments employs a bridge Fig. 5- Resistive regulation can be applied to existing equipment if provision is circuit and it is necessary that the made for stepping up the supply voltage to compensate the average drop across the regulator tube. Here a stock replacement ballast tube and a filament transformer voltage across this bridge be kept capable of providing a 22.5 -volt boost combine to form a hurriedly assembled plug-in constant despite a 27 percent varia- unit which maintained the supply to a communications receiver constant within two tion in the only available voltage volts with the line varying between the limits of approximately 105 to 130 volts supply source. His requirements, are as follows: two values, known as the "thres- (diameter 1 inch, height 4 inch), Supply-airplane battery, varying hold" and "end" values, that the the regulator will dissipate up to 20 from 22.5 to 28.5 volts. operating range of the ballast is watts in constant service and up to Permissible range of voltages ap- placed. Within this range is an- 30 watts over shorter periods. Life plied to load 1.95 to 2.0 volts. other range over which the resis- is rated at 3000 hours where dis- Required drop across ballast tube tance increase is so rapid as to com- sipation does not exceed 20 watts. 20.55 to 26.5 volts. pletely offset any tendency toward Where constant dissipation up to Maximum permissible variation of current increase. It is over this por- 40 watts is necessary, a tube envel- current through load 0.49 to 0.50 tion of its operating range that the ope of about 2 inches diameter and amps. ballast provides maximum effective- 5 inches long is employed. This will This problem was a simple one, ness. provide for short -period dissipation involving a ballast that would pro- By varying the form, size and up to 50 watts and a 3000 -hour rated vide a minimum drop of 20.5 volts length of the iron wire employed, life where dissipation does not ex- and automatic variation of about 30 and its distribution on the spacer - ceed the normal 40 -watt rating. percent to compensate variation of forms, ballasts can be made to Bases may be of the vacuum -tube, approximately this same ratio in the widely different specifications. The lamp or miniature -bayonet types, supply source. Although a range of current threshold, for instance, may those of the vacuum -tube type rang- variation not exceeding 2 percent be any specified value from 30 ma ing from two -prong to octal. was specified-a value less than the to 10 amp. The range of control While these units are made in a maximum error in the meter move- voltage is usually considered to con- variety of stock ratings for retail ment employed in the instrument, stitute a ratio of 1 to 3; that is, an distribution, these are intended pri- and less than the error which may increase in the controlled current marily for replacement purposes in be introduced by the eye in reading 28 January 1942 - ELECTRONICS this meter-the sample ballast made troduced by a regulator in this case any more complicated. The ballast up and submitted to the instrument would mean subnormal voltage ap- manufacturer should be consulted manufacturer proved fully capable plied to the tube filaments. This when the transformer specifications of maintaining the load within the would likewise be true in the case of are drawn, as the required primary- specified values. 1.4 -volt filaments working from dry voltage rating will depend on the It is not always possible to pro- cells. But it is seldom, in either of elaracteristics of the ballast tube to vide this perfection in the form of these applications, that any form of be used and these in turn are de- a resistive regulator nor is such ac- regulation is needed. pendent on the anticipated variation curacy always essential. In one case in supply voltage, the load current, a manufacturer desired a ballast Operation on A -C Circuits the degree of regulation required and to a certain extent on the nature tube capable of maintaining a rela- In a -c circuits it is almost always of the load supplied by the trans- tively uniform voltage across the possible, if a discrepancy does not former. filaments of a group of 2 -volt tubes already exist between supply and re- When the necessary regulator when using a 3 -volt dry -cell source. quired load voltages, to redesign the drop cannot be taken care of in the Moreover, it was desired to obtain equipment to provide for the voltage design of the equipment itself, it is maximum battery life, which meant drop called for in using a ballast. sometimes practical to increase the that the minimum resistance intro- Thus where the equipment includes supply voltage if the source is either duced by the ballast would have to be a line transformer this can be an a -c line or battery. In the former very low if the battery were to prove wound for a primary rating of 90 case a transformer of suitable step- usable to a reasonably low end-volt- volts instead of the conventional 115 up ratio can be added between line age. The ballast supplied in this volts, if the ballast is one which re- and load. In battery- operated equip- instance provided the following 25 drop at normal sults in a -volt ment the battery voltage can be in- range of operating variations : line voltage. Line variations above creased. Dry -cell battery supply variation below value will then be or normal Where a regulator is to be em- 2.2 to 3.0 volts. in the regulator with the absorbed ployed with an individual piece of Variation in voltage applied to tube result that the voltage applied to the a -c equipment, as in the case of filaments 1.85 to 2.0 volts. will remain transformer primary existing laboratory apparatus, in Range of drop across ballast 0.35 to constant. substantially application of communications re- 1.0 volts. Figure 4 illustrates the regulatory ceivers in which constant voltage Current variation through load 0.49 obtained in the case of one action supply may be important, in the sub- to 0.51 amperes. set employing a ballast a -c radio stitution of automatic for manual To achieve this degree of regula- normal line voltage intro- which at regulation of filament voltages in tion the ballast had to be capable of of 27 volts. The power duced a drop transmitters, etc., it is quite possible automatically varying the voltage primary was designed transformer to provide this form of regulation, drop across it in the ratio of 1 to 3. 88 volts. For line for a supply of externally or internally, with- In spite of this wide variation it 105 and either voltage variations between change in ex- proved capable of maintaining the pri- out resorting to any 130 the voltage applied to this or other com- filament voltage at the controlled isting transformers accomplished by within a total variation of 7.5 ponents. This is tubes through a percent and the filament current supplying the equipment -up and a bal- 4 percent. small step transformer within serves Had the nature of this tube equip- last tube. The transformer existing line voltage ment been such that a higher degree to step up the drop introduced of regulation was necessary, it to provide for the thus allowing the could have been obtained by using a by the regulator, voltage to be applied to 4.5 -volt battery. The ballast then normal rated Fig. 6- Circuit of the set -up shown in the apparatus to be controlled. Such would have been called upon to pro- 5 in which a filament transformer Fig. of a trans- vide a drop varying only between 1.3 supplies the additional voltage required a simple unit, consisting and outlet re- and 2.5 volts or a ratio of 2 to 1. Its by the drop in the ballast resistance former, ballast tube Fig. 5 and its operation could have been confined ceptacle is shown in entirely to the flat portion of its mary remained within plus or minus circuit in Fig. 6. so far has been characteristic and the voltage ap- 1 volt of its rated value, the regula- The discussion with the use of plied to the filaments held to a max- tor drop varying automatically be- concerned primarily tube in series with a load. imum variation of 1 to 2 percent. tween 17 and 41 volts to maintain the ballast is il- Because this type of regulator is this substantially constant value. Another type of application and curves resistive device its incorporation Even for the wider and highly un- lustrated in the circuit a output voltage in any supply circuit necessarily in- likely variation range of 90 to 140 of Fig. 7. Here the d -c generator, troduces some drop in the applied volts the voltage applied to the trans- of a compound -wound water wheel, voltage. It therefore does not find former suffered a maximum varia- driven by a low -head the wide vari- application in all circuits. Where tion of 6 volts, equivalent to about suffered as a result of load which it 6.3 -volt tubes are operated from a 7 percent. ation in the lighting With a suitable ballast 6 -volt storage battery, for instance, In manufactured equipment a supplied. the series field the minimum voltage supplied by transformer such as this costs no tube shunted across improved to such the battery when partly discharged more than one having a conventional the regulation was generated voltage may be only 5.7. Any resistance in- 115 -volt primary, nor is its design an extent that the ELECTRONICS - January 1942 29 across the regulator therefore neg- 13 1,300 13 ligible. This places practically the full line 12 1,200 12 0 - A voltage across the load. In the case of a radio set with a 90 -volt 11 1,100 11 0 - C transformer primary this would be 10 1,000 100 distinctly undesirable. 9 900 90 - íÖ: 03/010=0 To avoid this latter condition, bal- sses last tubes can be supplied 8 800 80 with an additional fixed resistance shunted d 7 ? 700 4.4. 70 Ballast a by an automatic time -delay switch. Q 6 d 600 >° 60 This switch is normally open so that 5 500 50 when the power is turned on the fixed resistance is in series with the 4 400 40 load and limits the current to a de- 3 300 30 sired low value. After a predeter- A= Load-amperes 100% variation from maximum mined 2 200 20 time interval the switch auto- - B= Speed r. p. m. 30.6 % variation from maximum matically G= Volloge shorts out this resistor 1 4.3 - 100 10 variat¡on from maxi and the ballast resistor takes its 0 0 0 normal control. Such an arrange- 50 60 70 80 90 100 ment provides Percent, Full Load completely automatic protection in starting. Because the resistor and switch are inside the Fig. 7 -Load characteristics of compound wound d -c generator driven by water ballast tube, with connections wheel with constant head. Ballast placed in parallel with the series field brought out to the tube prongs, they introduce no mounting or wiring complications. Fixed resistors was maintained to serve other pur- constant between these conditions the change to the poses can also be included 112.5 and within 116 from zero to full load approximate vicinity of the new the ballast tube. and with generator It is common prac- speed variations value will be relatively rapid, the tice to include pilot of 30 percent. -light shunts in greater part of the time lag lying ballasts designed In this application for use in ac -dc re- the ballast op- in the gradual approach within im- ceivers, for instance. Automatic erates over the steep, initial portion mediate proximity of the final value. switches of either the thermostatic of its curve as well as into the flat Thus from a cold start, regulators or hot wire types can also be in- portion. At low load current its re- designed for controlling currents up cluded and these are available sistance is relatively in low with the to about 1 amp will reach approxi- wide variety, from s.p.s.t. to d.p.d.t., result that a good portion of the mately 5 percent of their proper con- for opening or closing circuits and load current is by- passed around the trol value within 3 sec. for instant or delayed action. series field. As the load current in- In some applications this lag may Where the controlled equipment creases, however, the regulator re- be an advantage. It is possible, for includes a stand -by switch to cut off sistance increases, forcing more and instance, to introduce time delay in plate current this does not by any more of the load current to flow the operation of a relay by shunting means preclude the possibility of through the series field winding. a suitable ballast resistor across its utilizing a regulator. It is only The result is that unusually good coil. When the actuating current is necessary regulation to incorporate a fixed re- is obtained at all values applied the ballast serves momen- sistance in series with of loading. the supply tarily as a low-value by -pass. The line, and so arranged that it is in- current flowing through it causes its serted in the circuit by the action The Time Lag Characteristic resistance to rise until the voltage of a section of the stand -by switch required to operate the relay is to serve as an auxiliary dropping Reference was made earlier to a reached. Delay periods of from a resistor during periods when no lag in the control action of regula- fraction of a second to 10 sec can be plate current is being drawn. tors of the resistive type. This lag economically obtained in this way. There is no practical type of regu- varies anywhere from a fraction of The other limitation mentioned is lator device capable of universal a second to as much as two minutes, presented in cases where load varia- service in all types of applications. depending on the power being dis- tions assume wide proportions. A Some are limited in their applica- sipated in the regulator and the typical example is found in vacuum - tions by the type of current deliv- range of regulation. This is quite tube equipment which has provision ered by the source, others by their understandable when it is realized for cutting off the plate current dur- mechanical complications, size, that a change in resistance is de- ing stand -by periods, or during the weight, cost, etc. Regulators of the pendent on changing temperature of few seconds after such equipment is resistive type are perhaps the most the wire. When dissipating energy turned on, while the tubes are warm- universal of all and certainly the near the limits of its rating this may ing up and no plate current is being least expensive. Their possibilities involve stabilization of the sur- drawn. Under such conditions the are well worth investigating when- rounding temperature at the new load current drawn may be less than ever a problem involving regulation level. Even when operating under half the normal value and the drop arises. 30 January 1942 - ELECTRONICS Super-Ccirdioid DIRECTIONAL MICROPHONE

By B. B. BAUER Shure Brothers, Chicago

Desirable directional properties have been obtained in .a single unit microphone employing the principle of acoustic Another commonly accepted index response, of directivity, although not neces- phase shift. Ruggedness, low noise, good frequency sarily of unidirectional properties, axial symmetry of directional pattern and high degree of is the random efficiency of a microphone', i.e. its ability to receive directivity characterize the Uniphase microphone sounds arriving from all directions, as compared with that of a non -directional microphone having equal normal incidence efficiency. Decrease in reverberation energy pickup is given, in percent, by E= 100 (1 -ri) ex- UNIDIRECTIONAL microphones tional microphone as "one which has where 71 is the random efficiency have been accorded an ever - a high front -to -back response ratio" pressed as a fraction. Again, proba- increasing acceptance in recent years i.e. is sensitive at the front and bility calculations indicate that min- when in the broadcasting, recording and relatively insensitive at the rear, imum random efficiency occurs and public address fields. The advan- along the line passing through the the proportions of circular in a ratio of tages which a cardioid (or heart - 0 to 180 deg. axis. It is apparent, cosine components are This pat- shape) pattern presents over a non - however, that sounds originating 25 percent to 75 percent. directional pattern, found in pres- precisely at the front or at the rear tern has been termed a hyper - sure microphones, are a two- thirds of a microphone occur relatively in- cardioid.' with decrease in reverberation energy frequently. The function of a uni- The polar patterns obtained and pickup, separation of the desired directional microphone appears to be various proportions of circular Fig. from the undesired sounds, and more properly defined as that of ac- cosine components, is shown in -to -back simplification of microphone place- cepting the sounds arriving from an 2 which also lists (a) front ment problems. The cardioid is ob- imaginary hemisphere at the front of response ratio ; (b) front-to -back and (c) tained through the addition in equal the microphone, and rejecting those hemispherical random ratio; -car- proportions of a bi- directional (co- arriving from a hemisphere at the random efficiency. The super as unidirec- sine law) characteristic and a non - rear of the microphone. Calculations dioid is roughly twice circular characteristic, re- based upon the probability of ar- tional as the cardioid or the hyper - directionaI of sulting in the expression p = (0.5 -I- rival of sounds from random direc- cardioid from the standpoint random ratio. On the 0.5 cos B) shown in Fig. 1A1. Later tions indicate that the optimum pat- front -to -back studies indicated that for maximum tern in accordance with this defini- basis of random efficiency, it permits unidirectional action it is necessary tion occurs when the proportions of a 73 percent decrease in reverberation with 66 to mix the circular and cosine law circular and cosine components are energy pickup, as compared in a different pro- in a ratio of 37 percent to 63 per- percent for the cardioid and 75 per- characteristics The portion. cent (see Appendix). This pattern cent for the hyper -cardioid. The cardioid fulfilled the formerly has been termed the super -cardioid, hyper-cardioid has a front -to -back 2 1 and is, accepted definition of a unidirec- and is shown in Fig. 1B. discrimination of only to ELECTRONICS - January 1942 31 Front- to-back Random Ratio (Un/a/rectrona/ index I/7 Random Efficiency 9 27o. 1111111W MEW

b) /B0' '-(a)

(a) Card /oid (0 5 # 0 5 cos 9). 25 - (b) Sup èr -Card o/d I (037.063 cos 01 Percent

Fig. 1- (Above) Cardioid and super -cardioid (;) directional patterns. Probability calculations Super Hyper Circle Cardioid Cardroid Cardioid Cosine indicate that few sounds originate directly in front of the microphone Front-to-back Response.

Fig. 2- (Right) Random efficiency and front - to -back random ratio curves for various proportions of circular and cosine com- Random Efficiency. ponents and a comparison of several types of directivity patterns

therefore, somewhat unsatisfactory There is considerable evidence that tortion of the polar pattern increases as a unilateral microphone. These other investigators found similar with frequency and with separation considerations definitely point tow- problems in connection with two -unit of the two units. This is indicated ard the super -cardioid as providing unidirectional microphones. in Fig. 3, which shows polar pat- a more satisfactory unidirectional Realization of these difficulties led terns in the horizontal and the ver- pattern. These conclusions have been to the development of single -unit tical plane of a commercial two -unit checked by extensive field tests in uniphase cardioid microphones op- cardioid microphone, in which the which microphones employing dif- erating on the principle of acoustical separation between the pressure ferent patterns were used. phase shift. A uniphase piezoelec- and the velocity units is two inches. tric cardioid microphone was first These polar patterns were obtained The Single Unit Unilateral Microphone made available in 1937,5 and a uni- by using three bands of random phase moving -coil cardioid micro- frequency noise, of 100 to 400, 400 Early cardioid microphones were phone appeared shortly afterward. to 1600, and 1600 to 6400 cps. Hori- constructed using a velocity -type Recent studies of the general acous- zontal plane patterns closely ap- ribbon microphone, connected in tical problem involved resulted in proximate a cardioid; however, the series with a pressure ribbon micro- the development of a new single - patterns in the vertical plane are phone.' In later years various unit microphone with a super - distorted at high frequencies, where cardioid microphones have been de- cardioid pattern and with a greatly the separation is comparable to the veloped following the same principle, improved performance. The new wavelength of sound. There is no but employing other types of pres- microphone has the following fea- evidence of such a considerable pat- sure units in combination with a tures : (a) a super -cardioid pattern tern distortion with the single unit velocity element.' Considerable manu- for optimum unidirectional proper- microphone. It is evident, therefore, facturing experience with such mi- ties, and low random noise pickup, that the single unit microphone may crophones indicates that the two -unit (b) an excellent frequency response, be more effective, in eliminating cardioid process entails many tech- sensitivity, and high signal -to -noise sounds reflected from above or be- nical difficulties and high basic costs, ratio, (c) ruggedness and low wind - low, than a conventional two unit because (a) the frequency response noise pickup common to moving -coil microphone. of the two component microphones microphones, (d) simplicity and must be held to close limits economy to pro- which result from the use Structure and Theory of Operation duce a good directional pattern at of only one translating unit, and all frequencies; and (b) electrical (e) axial symmetry at all frequen- A cut -away photograph of the networks have to be provided be- cies. The point (e) has not been gen- dynamic uniphase structure is shown tween the two units to compensate erally recognized in connection with in Fig. 4, and a cross- sectional view for the effect of phase shift, due to two -unit unidirectional microphones. is shown in Fig. 5. The moving coil the difference in operating principle However, it is obvious that since is wound on a tubular bobbin and of the velocity and pressure units, such units are not symmetrical about suspended from two elastic spiders. and due to the physical separation the normal axis, they are not cap- It has been found advisable to use between the units which becomes able of having polar patterns sym- the clearance between the moving significant at higher frequencies. metrical in all directions. The dis- coil and the inner pole piece as one 32 January 1942 - ELECTRONICS Fig. 3 -(Left) Horizontal (a) and vertical (b) plane polar response patterns of a two unit cardioid microphone

Fig. 4 (Right) Cutaway photograph of the dynamic uniphase structure of the new microphone

Fig. 5 -(Below) Cross section of the unit shown in Fig. 4. An acoustical phase - /00-400 C P5. shifting network produces the effect of com- - 400-1600 C PS bining a velocity microphone with a pres- ---- /600-6400 C PS. .'- (.Qandom noise / sure microphone source)

Magnetic circuit return

of the phase shifting network ele- - Magnet ments. The action of this network is Outer po /e piece. i h pole o described in detail below. The vol- D ap ra9m -inner ece. umes enclosed between the diaphragm and the inner pole piece, and inside of the magnet, are also used as part of the phase shifting network. These volumes are subdivided by an acoustical screen A. The magnetic circuit return consists of the Et, Ec outer pole piece and four iron bar-. which are designed to provide an adequate magnetic path, and at the same time permit a free access of T sound waves to the slit S between the inner pole piece and the coil. The complete unit is covered with a wind screen and suspended in a cradle, Fig. 6 (Above) Equivalent the object of which is the elimina- electrical circuit of the tion of stray vibration pickup. acoustical network Referring to Fig. 5, a plane sound the unit from the wave, approaching Fig. 7 (Left) Phase shift front, first acts upon the front of and pressure curves of the the diaphragm with a pressure P., super -cardioid microphone then flows around the outer pole piece, past the slit S, acting upon it with a pressure P,,. The time required cal, and P., and Pb are in phase. upon the acoustical network and in traveling from the diaphragm Likewise, it is apparent that for produces a pressure P.. within the The to the slit is d /C,. second, where d is waves arriving from any other angle, volume under the diaphragm. the effective air distance from the 9, the effective distance d is de- magnitude of P., is the same as that diaphragm front to the slit, and creased by the factor cos 0, and hence of P, but it is shifted in phase by in super - is the velocity of sound (34,400 cm the phase shift between the pres- an angle 4,, which, the per sec). This time interval cor- sures at the diaphragm and the slit cardioid case, is 37/63 of s6, at any The phase angle, responds to a phase shift of cud /C,. is ¢, = (wd/Cr)cos O radians. There- given frequency. radians. If the wave is approaching fore, ¢, may be compared in function ¢, depends solely upon the network parallel to the diaphragm (90 per- with the velocity (cosine) compon- constants, and is, therefore, entirely of cent incidence), the time of arrival ent of a two -unit unidirectional mi- independent of the direction at the diaphragm, and the median crophone.° sound incidence. Hence, ¢, may be on page 91) time of arrival at the slit are identi- The pressure Pb at the slit acts (Continued ELECTRONICS - January 1942 33 Photoflash

By P. A. MARSAL Research Laboratories, National Carbon Co., Cleveland

ing the start of the time interval to tional photoflash lamps. One of these be measured, exercises control in may be conveniently connected Fig. 1 -Basic circuit of interval tinier using grid G, two gas tubes and a condenser circuit and causes T, to ion- across R1.) ize. Condenser C starts to charge A light source, such as the 6-8 through Ti, but before it is fully volt, 21 candlepower automobile charged event No. 2 occurs, marking headlight lamp contained within the THE device to be described was the end of the time interval to be case at the left of Fig. 3, is mounted designed to quickly indicate vari- measured. A pulse of voltage exer- so that illumination from it impinges ations in the timing of photoflash cises control in grid circuit G2, ion- upon the 917 phototube through a synchronizers, i.e., the interval be- izing T2. With T2 ionized, the plate magnifier. The camera shutter, with tween closure of the synchronizer potential on T, is reduced to a value synchronizer shutter actuator at- switch (with consequent rapid at below the extinction potential and tached, is interposed between light tainment of peak flashlamp bril- T, is deionized, leaving condenser source and phototube. When the liancy) and opening of the camera C with a definite charge, the magni- shutter opens, permitting light to shutter. tude of which is a measure of the fall on the phototube, current flows Flashlamps in synchronizers un- time interval between events number through R2 and the voltage developed der test appeared to require the shut- one and two. across this resistor trips the second ter to open in 20 milliseconds. The 2051, extinguishing the first 2051 Practical Circuit range covered by the photoflash syn- by virtue of the virtual short circuit chronizer tester is therefore from A practical circuit is shown in Fig. across Re and stopping the condenser 10 to 45 milliseconds. 2. The photoflash synchronizer un- charge cycle. Operation is accomplished by two der test is connected across R, in The voltage across C. is immedi- gaseous tetrodes which control the such fashion that the voltage of the ately read by rotating switch SW charging of a condenser in accord- battery within the synchronizer ap- one step clockwise, which connects ance with the time interval to be pears across this resistor as soon as it to the input of a degenerative vac- measured. The basic circuit'' 2 is the synchronizer operating switch is uum -tube voltmeter, calibrated di- shown in Fig. 1. Tube T condenser closed, ionizing the 2051 at the left rectly in milliseconds as shown by C and resistor R are connected in of the diagram and starting the con- typical curves in Fig. 5. After read- series across a source of d -c poten- denser charge cycle. (This connec- ing the time interval, switch SW is tial. Bridging the resistor R and tion is facilitated by the fact that moved one more step clockwise to source of potential is a second tube most commercial synchronizers have discharge C,, is then returned to the T2. In operation, event No. 1, mark- extra sockets for attachment of addi- original or "charge" position after pausing for an instant in the central or "read" position to note whether 917 e the meter returns fully to the index 2051 6C5G mark denoting a completely discharged condenser. The pushbutton is then depressed, opening the anode circuit of the second gas tetrode and permitting its grid to regain control. Sync The device is now ready for another o 0 -tn'a time interval measurement. Initial Adjustments VR 1054. Two initial adjustments are re- RS l,000 z04

A phototube, two gaseous tetrodes and a receiving triode used as a degenerative v -t voltmeter combine in one compact instrument to permit rapid measurement of time intervals between 10 and 45 milliseconds on a 0 -1 milliameter

Fig. 3- Completed photoflash synchronizer tester. with light source at left

bias 0.5 volt is required from the the instrument in its cathode circuit synchronizer battery and any value through improper manipulation for the maximum current which can flow greater than this will, of course, Fig. 4- Chassis layout. showing components serve equally well. Bias is readily through it is limited to 1.2 ma. a 1,000 ohm/ adjusted by connecting Design Details volt meter between a "Sync" terminal and ground, adjusting potenti- The operating range of the volt- LO 0.8 ometer R, on the back of the chassis age regulator tube incorporated 3 illustrated in Fig. 4 but not visible within the power supply of the de- L 0.6 in the photograph. vice is from 5 to 30 ma. If good regu- 0.4 The second adjustment pertains to lation is to be obtained the instan- 2 0.2 taneous current required from the the bias on the gas tube controlled 30 40 50 exceed a 00 10 20 by the phototube and a satisfactory powerpack should never Vol -s Input setting is one which causes the tube value which will reduce the VR105 is current below 5 ma. The various Fig. 5 -VTVM calibration curves. Above- to trip when the camera shutter input volts. Below loads have been worked out accord- current output versus - three -quarters open. To effect this calibration of current output in terms of time adjustment, the testing device, light ingly. It is desirable to have source and shutter are arranged in the capacity of C1 large so that the 50 the respective positions which they effects of leakage do not reduce its se- are to occupy during subsequent voltage rapidly (the condenser 40 tests. The shutter is placed on "time" lected should, of course, embody low- is est possible leakage in its design.) m and opened. The iris diaphragm I1 30 then stopped down 1i stops from the On the other hand, if the capacity i.e., an f/4.5 is excessive it will be necessary to m fully open position, 20 lens is adjusted midway between use a lower value of resistance at f/5.6 and f /8. Pushbutton is momen- R, to arrive at the same charging 10 O tarily depressed and then, viewing voltage in the same time interval. the gas tetrode controlled by the There is then danger, due to the in- required from the o phototube through the case grille, creased current o 0.2 0.4 0.6 0.8 10 turning R, (also out of sight in Fig. powerpack, of the voltage regulator MA. Reading 4) slowly until ionization occurs. tube dropping out. The maximum The device is then ready for use. voltage to which the condenser is charged is kept low with respect The degenerative type vacuum REFERENCES to the applied voltage in order to tube voltmeter is unaffected by nor- I Lord, H. W., "Measuring Small Time In- between 6C5G tubes. operate on the steep portion of the tervals", ELECTRONICS, Oct. 1932. mal variations 2 Bradford, C. I., "The Chronoscope ", ELEC- There is little danger of damaging charging curve. TRONICS, 1940. 35 ELECTRONICS - January 1942 STANDARDIZED MARINE RADIO UNIT

UP to the present time the instal- to improve operation, increase oper- on the left hand side of the unit, lation of radio equipment on ating efficiency and permit ready provides operation on any five pre- shipboard has followed no fixed plan. maintenance. determined frequencies in the range The principal demand for ship radio The equipment includes a main and 350 to 500 kc (835 to 600 meters). The facilities has been for replacement emergency radio transmitter, pro- transmitter circuit combines of obsolete sim- equipment on old vessels, viding a power output of 300 watts plicity with ruggedness. or the installation The fre- of selected units MCW (A -2) emission, or 240 watts quency determining oscillator, which of equipment in the case of new CW (A -1) emission when powered utilizes a 210 tube, employs ceramic ships. In either case, the equipment from the ship's d -c lines. In addition coil forms and low temperature coef- was placed where space and con- the transmitter will deliver 50 watts ficient, aged condensers to insure venience dictated, a and tables or MQW (A -2) emission, or 40 watts minimum frequency deviation from benches were constructed'to support C* (A -1) emission when operated any cause. A buffer amplifier con- the apparatus. As regulations with from a 24 volt storage battery. Two sisting of a F -123 -A tube in a band respect to equipment details and in- motor generators are provided, one pass circuit, is used to drive a pair stallation methods became more operating from the ship's power, and of similar tubes in parallel in stringent the the time required to per- the other from the battery power. final amplifier. This stage is form the installation coupled of a complete Selection of one or the other sources to the antenna circuit by means of a shipboard equipment has increased of power is provided by panel radio frequency transformer, to a matter ad- of weeks. switches. This transmitter, which is justed at installation to the antenna With the plans for building a large resistance. The antenna circuit com- number of new cargo vessels came prises a high Q loading inductance the incentive to standardize radio FEATURES OF and variometer. Only two controls room installations, MARINE and to unify the RADIO UNIT are necessary to change frequencies. equipment to the point where the 1. Installation, Servicing, and Repair Features The oscillator is employed to obtain majority of the labor could be ac- All equipment completely wired at factory MCW. Protective devices such as complished prior to placement of the Only power supply and antenna need be connected fuses and a resetting circuit breaker apparatus on board a vessel. on board ship To this All equipment completely standardized associated with the power amplifier end, and and in keeping with the trend interchangeable plate circuit reduce the possibility toward speedier production of qual- All equipment readily accessible for inspection, of failure to a minimum. In addi- ity equipment, the Federal Telegraph cleaning, or repair Installation can be made. in small fraction, the circuits employed are those Division of International tion of time usually required Telephone in which the amplifier power is re- and Radio Mfg. Corp., of Newark, 2. Features of the Transmitter duced to a low value if the frequency N. J., I.T. Main transmitter &T. associate, has devel- delivers 300 watts, is changed, or the antenna detuned, oped a single unit of operating from ship's power line equipment in Emergency opened or grounded. which is housed unit, operating from batter- all of the apparatus ies, delivers 50 watts The production of a transmitter of required Two generators are provided; for a modern, efficient and one for dimensions and characteristics adap- completely reliable radio room in- ship's power and one for batteries Transmitter operates on five predeter- table for use in a compact unit stallation of for cargo vessels. mined frequencies this type has been a matter of prog- This Frequency is changed by adjusting only marine radio unit is fur- ressive development. Outstanding in nished completely cabled, adjusted two controls Power supply to rectifiers is at 720 cps. this connection is the use of a high and ready for installation. The as- 3. Features of the Receiver frequency power source. The gener- sembly includes an operating shelf, Receiver covers 15 to 650 kc in four ators, which are powered from the message racks and all necessary bands ap- ship's d -c line, develop power at 720 purtenances for complete and effi- Receiver is battery operated to minimize noise cps for operating the full wave mer- cient operation. The marine radio Emergency receiver uses no power cury vapor rectifier and filter system unit, possesses all of the features re- 4. Alarm and Direction Finding Features in the transmitter. The use of a -c quired by the Federal Communica- Warning bells automatically rung upon supply provides safety to operating Commission, reception of distress tions the Bureau of signals personnel, inasmuch as no high volt- Marine Inspection and the U.S. Mari- Manual and automatic means for transmitting distress signals is age exists outside of the transmitter time Commission, plus provided many addi- Direction finding facilities are provided panel. The physical dimensions of tional features which are included the power units for operating at this

36 January 1942 - ELECTRONICS Production for defense is the keynote of standardized marine radio equipment, completed in factory and ready to plug in to ship's power line and antenna. Ease of accessibility of all parts which are standard simplifies and expedites training of personnel using these packaged units. Alarm, distress, and direction finding facilities are provided

45 or 90 degree angle for service or replacement of parts. Two receivers are also incorporated in the unit. The regular receiver, 128AX, covers the frequency range of 15 to 650 kc in four bands. It is battery operated, providing as a result, reliability in case of failure of the ship's power. The receiver uses a tuned radio frequency circuit, into which has been built all of the desirable features required in a marine receiver, such as absence of images, smooth regeneration, sharp- ness of tuning and freedom from vi- brational or microphonic noises. The dial is directly calibrated in frequency, and illuminated. The receiver chassis is completely removable from the front, cable length permitting servicing of the receiver on the operating table. The chassis may be completely detached for replacement by removing two plugs at= tached to the power cables. The second receiver, 123 -BX, is a simple affair using a crystal detector. This

Below, the transmitter unit is hinged at the bottom and may be swung out for inspection and frequency are so reduced over that Above, All radio equipment required repair necessary at lower frequencies, that for shipboard op- they fit conveniently into the trans- eration is contained mitter frame. The motor generators, in this single unit mounted in the lower section of the unit, although rated at 750 watts, are small enough to be carried by one man. Both machines are mounted on rubber cushions, and arranged on separate bed plates which permit the machines to be slid outward for servicing without disconnecting any wiring. The transmitter fuses and power components are accessible from the left side door, or the transmitter can be swung outward to a All parts of the unit are easily reached for inspection because of the several panels provided for that purpose. A crystal receiver is included for use when all power supplies fail

receiver, use of which is mandatory mounted in the lower chassis. This of the apparatus which comprises the on all ocean going vessels, provides selector, which is motor driven, circuits is immediately accessible means for reception should all other segregates the incoming signals, dis- from the front of the unit. devices fail. Though outmoded, and criminating between distress signals An antenna transfer switch is only dimly recalled by many in con- and those of other origin, such as at- mounted near the top of the unit to nection with the infancy of radio, mospherics and routine ship busi- effect the transfer of antennas and the crystal receiver in its modern ness. When the international dis- circuits associated with the auto form with etched panel and double tress call, which consists of 12 four - alarm and receivers for any desired circuit tuning, is quite an effective second dashes spaced one second functions. When in normal operating and reliable device when used with a apart, is received, bells in the radio position, the main transmitting ship's main antenna. room, the operator's quarters and on equipment is connected to the main A complete auto alarm equipment the ship's bridge are operated. and antenna, and the receivers arranged is provided in the marine radio unit. can only be silenced from the oper- to operate through a break -in relay The auto alarm, which is composed ating position. The device is fool- from the main antenna. When placed of two separately mounted chassis proof. It possesses such features as in the auto alarm position, the main hinged to the front panel, is used to automatic transfer to battery power antenna is connected to the auto monitor the calling and distress band upon failure of the ship's power, alarm receiver, and an auxiliary re- (500 kc) whenever the operator is not and operation of an alarm bell should ceiving antenna is connected to the on watch, or when he is engaged in a tube fail, the motor speed vary, receivers to permit reception of press reception on other than this band. or the voltage of the battery supply and weather reports on other bands The upper section of the auto alarm drop abnormally. Signal lights on without leaving the distress band houses a sensitive receiver, receptive the bridge and on the operating unmonitored. By simply placing the to modulated signals in a band ap- panel also indicate misadjustment switch in this position, the power cir- proximately 12 kc above and below or the requirement for adjustment cuits which place the auto alarm in the 500 kc band. The output of this re- due to increasing atmospherics or operation are closed. The auto alarm ceiver is rectified, and employed to noise level. Both units are hinged to is thus placed in service by this operate a selector device, which is the front panel of the unit, and all single simple operation. Another

38 January 1942 - ELECTRONICS switch position, labelled Direction equipment controls and motor gen- gether after being mounted in place. Finder, closes through the circuits erator units is provided, to permit Special terminal facilities are pro- to the radio direction finder on the efficient operation in case of failure vided to simplify this procedure. A bridge, permitting its operation. of the ship's power. compartment is provided in the base Antenna grounding facilities are also Accessibility of the internal parts section for spare parts. provided. The design of this switch has been extended to a point not The apparatus has been carefully is such that only the grounded han- previously approached in marine treated for electrical noise by use of dle is exposed to the operator, all equipment. All panels with the ex- filters and adequate shielding of con- high voltage connections being back - ception of the antenna switch are ductors. panel. removable from the front. Two side This marine radio unit is being A radio clock is placed directly in doors permit additional access to the placed on all of the 312 "Liberty" front of the operator, in line with his interior for routine inspection. (EC -2) vessels now under construc- eyes. The clock has special indica- This marine radio unit has been tion by the U.S. Maritime Commis- tions for silent periods, and the four constructed mechanically for severe sion. It is estimated that the time second intervals are marked in red use under conditions of unusual vibra- required to install the marine radio on the second hand scale to aid the tion which might possibly occur in unit is but one fifth that required operator in transmitting the inter- marine service. All panels are heav- to install the twelve equivalent national distress signal, should this ily copper plated before painting to pieces of apparatus which this unit be necessary. An automatic keying prevent rust should the paint become replaces. The standardization of parts device, associated with the auto chipped. Equipment labels and desig- and placement is also being hailed by alarm, may be placed in operation nation plates are finished in a soft those responsible for operator in- by throwing a single switch on the grey tone, adding considerably to struction, as it is now possible to auto alarm panel, whereupon the in- the finished appearance of the unit. place an operator familiar with this ternational distress signal is trans- All doors are reinforced to avoid equipment on any vessel in the "Lib- mitted automatically, using either annoying rattling, and three point erty" fleet, with the assurance that the main or emergency power sup- door latches are employed. To facil- he will be enabled to operate effi- plies. itate handling, and to enable the ciently without additional instruc- Battery charging and control cir- equipment to be transported through tion, inasmuch as each knob and con- cuits are located on a panel directly narrow passage ways and doors, the trol is in exactly the same place on above the receivers. Two sets of equipment may be divided into two every vessel. This represents a de- batteries are provided for both the equal sections, which are bolted to- cided step forward in marine design. auto alarm and the main receiver, and the switching facilities permit Motor -generator sets operate either from the ship's main power line or from charging of one set of batteries storage batteries. The rectifier unit for the radio equipment is supplied with while the other is in use. The charg- a -c power at 720 cps ing switches associated with the transmitter emergency battery are mounted on the front of the transmitter panel. All charging resistors are placed within the cabinet, a ventilating fan serving to exhaust the heat generated. This fan, which also serves to cool the transmitter components, is automatically placed in operation when any of the charging or transmitter switches are thrown, its speed being proportioned to the heat generated. When the batteries are being trickle charged, the fan rotates slowly. When one or more chargers are placed in full operation, the fan operates at high speed, exhausting quite completely the heat generated. Although the placement of charger components and the discreet use of baffle plates provides natural ventilation, absolute safety in case of failure of the fan is insured by a thermostat which functions should the generated heat become excessive, turning off the supply power. The resistors are mounted in clip holders, to enable their ready replacement. Emergency illumination of the ELECTRONICS - January 1942 39 Rectilinear Rectification Applied to Voltage Integration

The average value of small alternating potentials may be determined by rectifying the voltage, summing it up over a known time interval, and measuring the voltage after it has reached a relatively large value. An integrator for this purpose, which overcomes the difficulties and limitations of imperfect rectification, is described

BY S. S. STEVENS flow through the galvanometer G I, p,,rt"¡cot of Psychology when the input terminal 1 is posi- Harvard University tive. Furthermore, since the galvanometer circuit taps the midpoint G of the voltage drop between termi- FREQUENTLY desirable in A nals 1 and 2, equal changes in the physiological experimentation is resistance of the two rectifying ele- a knowledge of the average voltage ments will not affect the voltage im- produced by a nerve or muscle over Rt Ra pressed upon the galvanometer cir- a period of time. Outside of biology cuit. Analogous considerations ap- arise many other situations where a . Q ply to the full -wave circuit of Fig. 2 time -average of a fluctuating or al- G 1B. ternating voltage must be obtained. Since we are here using a variable The problem is to determine the area shunt resistance to compensate for under the curve which would repre- Fig. 1- Fundamental half -wave circuit (A) the variations in a series resistance, sent the fluctuating voltage graphi- and full wave bridge rectifier circuit (B) for it is possible, by a proper selection cally recorded. If the voltage straightening out the characteristic of the of the rectifying elements and the rectifier changes sign it is the area between resistances, to obtain almost any de- the curve and the zero axis that must sired relation between input voltage be measured. 400 v and output current. In particular, Electrical integration of alternat- it is possible to adjust the rectifiers ing voltages requires (1) rectilinear and resistances so as to compensate rectification (an ideal rectifier) and for the fact that the galvanometer (2) a means of accumulating and © 200 v draws a finite current and for the storing electric charge. Given fact that the inverse resistance of proper precautions, charge may be the rectifiers is not infinite. Using stored in a condenser, but rectilinear only resistances, copper -oxide recti- rectification is ordinarily considered fiers and microammeters, the author gapl°5foge impossible because rectifying ele- u/ofor has constructed several a -c volt- ments such as copper -oxide units and meters with linear scales. By means diodes have resistances which vary of a resistance in series with the in- with the current passing through Fig. 2 -The basic circuit of the voltage input, the response of these meters them. The problem, then, is to corn - tegrator using two pentodes and a voltage has been rendered independent of regulator tube biné non -linear rectifying Mements frequency over the range 5 to 20,- in such a way as to produce recti- 000 cps. linear rectification. These principles of rectification The principle e m p l o y e d to have been utilized in the construc- straighten out the characteristic of tion of voltage integrators capable a rectifier can be illustrated by the of a rectilinear response. The basic half -wave rectifier in Fig. 1A and circuit of the integrator will now be the full-wave rectifier in Fig. 1B. described. In Fig. 1A, if the two rectifying As shown in Fig. 2 a pentode V, is elements have comparable character- used to control the flow of current Fig. Practical network fot obtaining istics, if R, R2, and if R3 is large 3- to a condenser C. In order to reduce = linear output from a commercial bridge type compared to the combined resistance copper oxide rectifier. Resistance values the current to zero without recourse of the rectifier and R2, current will are given in ohms to a large negative bias on V, a 40 January 1942 - ELECTRONICS The current to the condenser in switch relay which in turn activates the circuit of Fig. 2 is not directly a marker on a moving tape. The to- proportional to the voltage applied tal number of marks within a given to the grid of V and when this period provides a measure of the voltage is fed through a conventional muscular activity. arrangement of copper -oxide recti- In order more perfectly to balance fiers the non -linearity is made even to zero the current to the condenser, greater. Therefore, in order to ob- a 3 -gang selector switch is provided tain direct proportionality between which on position 4 (as indicated the applied alternating voltage and in Fig. 5 below) shorts the con- the plate current of V, it is neces- denser and on position 5 connects sary to arrange a network of recti- the microammeter across the con- fiers which will exactly compensate denser. In this position the circuit for the curved grid -voltage plate - is balanced by adjusting the variable current characteristic of the tube. bias resistor R. At positions 1 and Such a network is shown in Fig. 3. 2 of the selector switch the meter is The rectifiers in Fig. 3 are com- in series with the condenser and at mercial instrument -rectifiers. Those position 3 the meter is shorted out. in the bridge are rated at 50 ma and The rectifier network of this in- those in the shunt arm at 15 ma. strument was adjusted until the fre- The latter have a higher resistance quency with which the condenser and a lower capacitance. The 400 - discharged was directly proportional ohm series resistor in front of the to the applied alternating voltage. 4 6 8 10 a range Input Voltage (1.000 cps) -Volis bridge serves to make this particular Linearity was achieved over network flat to within 1 db from 5 of from 0.5 to 20 volts. The con- Fig. 4-Input -output characteristics of the to 20,000 cps. The effectiveness of denser discharges once per second combined circuits of Fig. 2 and Fig. 3, il- this network, combined with an 1851 for an input of 5.6 volts rms. At lustrating that a linear relationship is ac- tube, in producing rectilinear recti- voltages lower than 0.5 the time be- curately attained fication is shown in Fig. 4. To a tween discharges is so long that close approximation the rectifier has sufficient charge leaks from the con- of the densers to cause a significant amount second pentode V2 provides a path corrected the characteristic for a bucking current to flow tube. of non -linearity. But over a range through the condenser circuit. When A voltage integrator is now being of approximately 40 to 1 the inte- is the circuit is balanced by the proper used in a medical research labora- grator gives a measure which area un- adjustment of the bias resistor R, tory to measure the total amount of closely proportional to the a fluctu- no current flows to the condenser. action potentials produced by the der the curve representing But then, when a positive voltage is muscles of various patients. The ating voltage. amplified and The integrator in Fig. 5 has a impressed on the grid of V3 the cir- action potentials are is flat to cuit is unbalanced and if switch S fed to the instrument diagrammed frequency response which 0 15,000 cps. is open, charge accumulates on the in Fig. 5. In this integrator the within 0.5 db from to ohms at condenser. The voltage on the con- 5µf condenser is discharged through Its input impedance is 3800 1000 and denser may be read directly by the 884 tube whenever the voltage 100 cps, 2700 ohms at cps 10,000 cps. It is fed means of a vacuum tube d -c volt- on the condenser reaches 110 volts. 900 ohms at meter or the voltage may be used to The discharge activates a micro- through a 250 -ohm transformer. activate a relay through a thyratron circuit. Both methods of recording the accumulated charge are at pres- Fig. 5- Schematic wiring diagram of the voltage integrator used in biological research ent being used in different experi- ments. As the voltage across the condenser rises, the plate voltage on V,

decreases and that on V2 increases by the same amount. For this reason, the choice of tubes is important. The situation calls for a tube whose plate current is as nearly invariant with plate voltage as possible. When type 1851 tubes are used the current to the condenser can be made to change by less than 3 microamperes as the condenser is charged from 0 to 100 volts. Under these conditions the plate voltage of V, falls from 250 to 150 volts and that of V., rises from 150 to 250 volts.

ELECTRONICS - January 1942 41 c\ b Gaseous

d Fig.la Tube voltage and i r current resistive load By W. W. WATROUS and D. E. MARSHALL

á Westinghouse Electric & Manufacturing Co. r Bloomfield, N. J. b NA/

d Fig. lb Tube voltage and current inductive load in the hope that a better understanding may be had of the factors Fig.1 in- a Anode current volved in securing long and trouble - b /on density free life. Certain examples c Forward tube vo /toge of short d inverse tube voltage tube life and their most probable e Tube aro drop causes will be discussed.

e Misinterpretation of Rating a b Information r ¡ All tube manufacturers publish data intended to define and limit the 4/14 various quantities which have importance in determining the amount 9 of power which 2a Phase shift control a given industrial Using sine grid tube will control, and the voltage probable length of trouble -free life which the e user d can expect. \ . ,a In general, these ratings are carefully observed. However, the authors have observed cases where the Ai, ratings were exceeded with consequent short tube life. This is probably due to lack of suitable measur- o Anode current 2 b Phase shift control ing instruments for determining b Grid voltage using peaked voltage the c Tube drop actual duty required of a tube in a d Supply voltage toir e Forward voltage given application, or a lack of ap- f Inverse voltage Fig. 2 preciation g Grid control characteristic of the role which each rating quantity plays in the satisfactory operation of the tube. Sev- eral of the most important and some of least well understood ratings will be discussed in the following para- graphs. AGASEOUS conduction tube is with which the authors have been inherently a trouble -free and concerned, that there is still con- Hot Cathode Ratings comparatively rugged device. How- siderable misunderstanding regard- ever, like any other piece of equip- ing gaseous tube application. This By far the largest number of ment, a certain amount of care must lack of comprehension, or perhaps failures found at "end of life" are be exercised in its application if sat- the disregard of known facts, has chargeable directly or indirectly to isfactory service and maximum life in a number of cases produced un- cathode phenomena. For the most are anticipated. favorable reaction toward the use part, these failures are the result of This article is written with the of electronic tubes. Furthermore, loss of electronic emission. Loss of knowledge that much of the mate- equipment designers are often as emission usually occurs after the rial may be a repetition of informa- guilty as equipment users in certain loss of emissive coating due either tion which has appeared in techni- instances. It is the purpose of this to normal evaporation of the active cal data sheets and engineering paper to point out the most impor- material, or to the more rapid action texts. It has been concluded, never- tant considerations to be observed known as stripping. Emission loss theless, from a large number of cases in the application of gaseous tubes, may also occur without loss of coat- 42 January 1942 - ELECTRONICS Tubes -and how to treat them

in Neglect of the rules for properly operating gaseous conduction tubes is certain to result unsatisfactory operation, and often to short life. Proper attention to the problems discussed here will prevent unfortunate and disappointing events

may result in tube failing and such a condition is fre- cathode potential. However, nominal der -voltage, a very few hours. quently found after a tube has been line voltage varies considerably in ure within re- Over -voltage, in general, results overloaded either in current or in- various sections of the country, enhanced electron emission and verse potential. sulting in cathode potential vari- in ± be considered beneficial. How- The rate at which evaporation ations which may exceed 10 per- might increased cathode tempera- (which is usually a normal effect) cent. ever, the resulting from the higher volt- and stripping (which is abnormal) In certain installations, change ture age, accelerates the rate of evapora- occur, varies widely with condi- from no load to full load conditions of active cathode material. The tions. A cathode which has a life ex- may reduce the cathode potential tion of this is not only reduction pectancy of several thousand hours considerably. result in cathode life, but arc -back or loss may have a life of only a few hun- Probably, one of the worst sources of grid control caused by the de- dred hours due to improper operating of trouble is faulty sockets. Either position of emissive coating on the conditions which accelerate the rate the sockets are not designed for the and grid. at which active cathode material is high currents required, or long use anode ten- The present form of cathode, used lost. has resulted in loss of spring in the majority of hot -cathode gase- While the remainder of the dis- sion, or corrosion of the contact sur- ous tubes, is designed to operate cussion on cathode life is concerned faces. It is surprising to measure the over a narrow temperature range, with loss of emission, it should be loss of cathode voltage sometimes and variation of temperature in realized that such emission loss is a found either in the socket, or in the either direction will materially affect very fundamental cause of other associated wiring when relatively life. of tube failure. Even in cases high cathode currents are employed. types Another cause of reduced cathode where the degree of evaporation or The purpose of the foregoing dis- is the application of anode po- is not sufficient to deplete cussion is to emphasize the need of life stripping the cathode tempera- the secondary effects, due insuring that the cathode potential tential before emission, has reached equilibrium. The to the deposition of active material is correct under all conditions of ture of such operation is exactly the other tube elements, may be operation. The cathode potential, effect on same as operating the cathode enough to cause a defective tube. (which means actual potential on the -voltage. The only differ- to such reasons as the pins of the tube), should be held at under Tube failures due ± this condition obtains, of grid control, and to within 5 percent of the rated ence is that arc -back, loss few times per day, burnouts are at times di- potential to insure maximum life perhaps, only a cathode under -voltage is continuous. rectly attributable to the primary expectancy. whereas A value for cathode heating time is reason that caused the loss of emis- The importance of this close con- usually a part of the tube ratings sive material. trol is understood when it is realized should be rigidly observed. The underlying causes of rapid that a reduction of 10 percent in and cathode potential may in some in- stripping, as determined by the Pool Type (Ignitron) Ratings examination of field returns over stances increase the arc -drop and is probably the most the course of several years, indicate starting potential 40 percent, and The ignitron ionic tubes. It has no the abuse of certain fundamentals reduce the value at which the cathode rugged of all there are few ways in in gaseous conduction tube applica- sparks* by perhaps 50 percent. Loss filament and user can misuse the tubes tion. More thorough consideration of emissive material, either by ca- which the a standard ignitron principles on the part of the thode bombardment resulting from when also using of these are designed equipment designer, and user, will high arc -drop or by sparking is very circuit. These circuits correct current to the result in much more satisfactory rapid, and, in extreme cases of un- to apply the proper time if the tube life. ignitor at the * Sparking is a phenomena obtained in an within the rat- The question of cathode potential oxide coating when the emission demand ex- equipment is used ceeds the capability of the cathode. Elec- from the ratings is one of utmost importance. Fila- tronically, it is the change from distributed ings. Departure thermal emission to an extremely localized often occurs in the following ment transformers are, almost with- arc spot. Physically, it results in the actual most mechanical removal of oxide coating from the ways : out exception, designed for the rated base metal. ELECTRONICS - January 1942 43 In welding control service, the Peak Inverse Voltage Rating However, tube heating is directly demand currents drawn by the dependent upon the average current, welder Inverse voltages which exceed the and controlled by the tubes so that an overload increases dissi- may tube rating, even momentarily, exceed the rated value. This pation from the anode. The result occurs while perhaps not causing destruc- because often no accurate is an increase in anode temperature determination tive arc -backs, may permit inverse is made of the actual which may release gas and ruin the demand current to flow. This inverse cur- current. In many cases a tube. A secondary effect is the re- measurement rent, although low in magnitude, of the demand current sulting increase in grid temperature can may be accompanied by a high volt- be made by closing the jaws of which promotes loss of grid control. the age drop. This high drop results in welding machine on a copper Operating a tube well within its bar the production of an electron velocity and quickly reading the current average rating pays large dividends with an ammeter, allowing the cur- which may be sufficiently high to knock in life. rent to flow only long enough to off active cathode material. make the measurement. Frequency Rating The Peak Current Rating percent duty rating is some- There is a definite upper limit in times exceeded because the original Normally, a new tube will stand a supply frequency which can be ap- setting of welding time was later certain amount of peak current in plied to a tube. The reason for this found to be inadequate and since the excess of the tube rating. The re- limitation is that a finite rate time is re- of making welds easily in- sult of such operation, however, if quired for the products of ionization creased, the duty required of the continued, is (1) shortened life and to disappear, or in other words for tube is increased. (2) rapid cathode failure. The first the tube to deionize. The higher If the the demand current of the weld- effect is caused by an abnormal rate frequency, the more the ion density

Fig. 3 Fig. 4

cP9 R

Cgf

a b Thyratron Cirr`uit showing the use of o Equivalent grid circuits to explain action of reectox to eliminate positive grid swing //rye transients on grid potentials

ing machine is too low, the ignitors of loss of emissive material due to lags behind the current. The result may not fire reliably. In nearly all positive ion bombardment, as the is a reduction in the amount of in- welding control circuits, the ignitors result of the high arc -drop occur- verse potential that the tube can are fired by the load current passing ring at the high current values. The withstand. In many cases, the ion initially through the ignitors. It is second effect occurs when the cur- density remains high enough due to possible that if the jaws of the rent overload is enough in excess inverse current to prevent control welding machine open before the of the rating to cause sparking. The (in the case of a thyratron or igni- ignitor circuit is opened, a small result of the sparking is the me- tron) in the forward direction. A exciting current will flow of too low chanical destruction of the emissive clearer understanding of this effect a magnitude to fire the ignitors, but material. Continued sparking results may be had by examining (Fig. 1 -a). high enough to cause them to over- in tube failure within a very short heat with consequent deterioration. time. Surge Current Rating Present practice is to connect an The surge current rating is auxiliary Average Current Rating resistance in parallel with thought by some to define a sort of the welder which draws about 25 Exceeding the average current super peak current rating. Actually, amps when the welder operates and rating of a tube providing the peak this rating is intended to be used furnishes enough current to fire the current is kept within limits, has by the circuit designer as indicated ignitors. On any welder application little direct effect on cathode life, below : where the current can fall below 40 other than an increase in the rate of The effective impedance of the amps rms., the auxiliary load must emissive material evaporation due power source which supplies the load be used. to the cathode temperature rise. current should be made high enough 44 January 1942 - ELECTRONICS to limit the tube current to the surge Therefore, some limit must be placed caused by failure of the water -cool- are current rating, in case the load por- on the averaging calculation. This ing. The water flow ratings outlet tion of the circuit is short circuited is done by limiting the time value by given in terms of maximum flow in accidentally. The time duration of which the current is divided to a temperature, and minimum these the short circuit should be limited definite maximum value. As an ex- gallons per minute. Both of by protective means, such as fuses ample, if a tube were rated 10 amps ratings are important. The tempera- well ob- or circuit breakers, to a time less average at a maximum averaging ture provision is usually of water than the maximum time specified in time of 30 sec., the maximum aver- served, but the importance the definition of surge current rating age current the tube could conduct velocity is not always appreciated. to given in the tube data sheet. If the within the ratings during a one The function of water -cooling of the tube short circuiting action is a part of minute interval would be 10 amps. keep the temperature vapor pressure the normal regularly reoccuring ac- If the pulse duration were 15 sec., wall and thereby the a given value. tion of the circuit, then the tube the maximum averaging current inside the tube below will assume a tem- current should be limited by the during the 15 sec. could be 20 amps, The tube wall of the maximum peak current rating. since the actual conduction time is perature higher than that the energy The tube designer considers the less than the maximum averaging water in the jacket, since the water. surge current rating to define a value time. As the actual conduction time is moving from the wall to difference is a of current which will not immedi- decreases, the maximum average This temperature with which ately destroy the tube, but which current during the pulse increases function of the velocity past the cooling will materially decrease the safety until the peak anode current rating the water sweeps of low factor in the tube rating at each is reached. The value of the maxi- surface. Under conditions or low load occurance. mum averaging time depends on the input water temperature heat capacity of the tube parts. on the tube, it is easily possible to reach a condition wherein the out- is below the rated Maximum Temperature Ratings let temperature Fig. 5 maximum and yet have the velocity An effect often overlooked by the so low that parts of the tube are tube user is the extremely rapid in- operating at too high a temperature. crease in mercury vapor pressure Another difficulty sometimes en- with temperature. The importance countered occurs where several tubes of this physical law results in the are operating with their water -cool- necessity of operating mercury tubes ing jackets in parallel. If the water within a limited range of tempera- rate is allowed to decrease, there is ture. great danger that the water flow is Operating a tube above the high not dividing in correct proportion temperature end of the published and that the flow in one tube may range, may cause high inverse cur- fall dangerously low. In cases where rents, loss of control, or arc -backs. the water temperature is low enough, Below the lower temperature limit, the tube water jackets should pre- the vapor pressure is so reduced that ferably be operated in series, thus action of cathode potential Rectifier there may be an insufficient number insuring equal flow in all tubes. of mercury ions to carry the required Many protective water flow relays current. The result is high arc -drop, have been tried in this service. and, in some instances, surging. Many of them actually caused tube Maximum Averaging Time These effects are both very injurious failure due to stoppage of water lodging The maximum averaging time is to the cathode. The importance of flow caused by silt or scale a manner that a part of the average current rating proper temperature control cannot in the orifices in such closed. as it defines the method of calcu- be stressed too highly. the relay contacts remained service lating the average current. Since the It should be borne in mind that Annoying interruptions to in water arc -drop of a gas -filled tube is practi- cathode heating time and tube heat- were caused by fluctuations to its cally independent of the anode cur- ing time are not the same. Tube flow operating the relay due rent, the loss in the tube becomes heating time depends on transformer lack of time delay features. now recommended a function of the average current regulation, ambient temperature, The type relay device, flow in the tube. When a tube is method of enclosure, the other wide- for this service is a thermal used continuously, the average cur- ly variable factors. In all cases, the a part of which is heated electrically, water rent can be obtained by calculation tube heating time should be sufficient and which is cooled by the is from the waveform of the current. to allow the condensed mercury flow. A bi -metal thermal relay the However, when the tube is used in- temperature to come within the pub- actuated by the temperature of termittently with very short pulses lished range before anode potential heated part of the relay. It is thus of current, the average current is impressed on the tube. responsive to water temperature action drawn would be very small if aver- Many tubes, such as ignitron and water flow. Time delay capacity aged over the entire time between tubes, depend on water -cooling to occurs because of the heat pres- pulses. However, the current of any make possible their high rating. It of the parts. Since hydraulic in action of one pulse could be high enough and is often found that troubles in the sure plays no part the nec- last long enough to damage the tube. field occuring with these tubes are the switch, no constrictions are ELECTRONICS - January 1942 45 essary and therefore clogging of the cathode to a more positive value reach sufficient magnitude to be switch is kept to a minimum. until a point is reached where, at, noticeable, except with the most deli- Deposits forming on the tube walls the will of the user, the retarding cate instruments, and they usually can cause loss of efficient cooling and potential of the grid is released, or cease to exist before a stable reverse consequent loss of tube life. A good an ignitor is fired. As the current arc can be built up. This concept practice is to flush water jackets at flows, the anode -cathode space is may appear plausible if we postulate regular intervals as determined by completely filled with ionized atoms a mechanism. This may be one vari- the amount of solid material in the of the gas with which the tube is ation of the well known patch theory. water. If the water is re- circulated, filled. As the current nears zero in According to this theory, particles it may be advisable to include a com- the cycle, a value is reached at which of material appear on the anode mercial rust inhibitor. the rate of production of ions be- originating in a variety of ways; comes less than the rate of loss, and such as, sputtered anode material, Measurement of Rated the tube ceases to conduct in the flakes of cathode coating, mercury Operating Conditions forward direction. However, there scum, etc. These particles are The best method of becoming ab- are still a great many ions remain- charged by the positive ion currents solutely sure of most tube operating ing in the space, thus leaving it and very strong fields may appear partially conditions is by the use of an oscil- ionized and in a state that on the anode surface which cause loscope. Economically, such measure- may initiate a current through the the phenomena mentioned above. ments where values of potential and tube in the reverse direction. These The role of the circuit comes into ions diffuse out of the space current are in doubt, are more than at a the picture as follows : When the justifiable. rate determined by a number of fac- incipient arc -back occurs, the reverse tors, Measurements of average current among which are the geometri- current increases at a rate deter- cal configuration should be made only on instruments of the inner parts mined by the external circuit. The using the D'Arsonval principle. of the tube, the ion temperature, cause or the patch is destroyed by the Many cases have been found where vapor or gas density, etc. The the discharge. If the current builds effect is, ion a so called a -c or d -c instrument has that the density lags up to a stable value before the patch the current been used. The error resulting can in the tube by an ap- is destroyed, a power arc follows be very large especially with preciable angle. and a real arc -back occurs. Accord- wave- If forms departing from sine waves. as shown in Fig. 1 -a, the circuit ing to this theory, the probability Condensed mercury temperature is such that the current and line of a tube arcing back increases as voltage approach measurements are difficult to obtain zero together, then the rate of change of current the precisely. However, a measurement, the presence of the ions is not serious connected circuit can supply to an accurate enough for practical pur- as the inverse voltage is low during incipient arc -back increases. An- deionization poses, can be secured by attaching the period. However, other way to prevent an incipient if the circuit one or more thermometers to the contains sufficient in- arc -back from developing to a stable ductance 1 glass envelope, by the use of putty as in Fig. -b the current arc is to limit the current which will continue or similar material. The exact loca- to flow for a time in the circuit can supply to a value opposition tion of the point of measurement is to the line voltage. When below which most arc -back causes it finally usually specified in the tube data reaches zero, the current will develop into true arc -backs. information. In cases where this conduction is expected to cease for This theory furnishes an explana- point is not shown the measurement the remainder of the half cycle even tion for a number of phenomena though now should be taken on the glass im- the inverse voltage is observed by tube and tube circuit almost mediately above the cathode base. at the peak of the line voltage designers, as enumerated below: and the tube is well ionized. Thus, 1. The stiffness of the circuit has Influence of Circuit Constants there is an increase in the prob- an effect on the arc -back rate. By on Arc Back Probability ability that arc -back will occur and stiffness is meant the degree of that the current will reverse and maintenance of voltage when a load Often errors are made in the orig- flow backwards through the load current is drawn. The better thé inal selection of a tube by choosing circuit. In the two cases cited, the regulation of a rectifier, the more one not designed for the type serv- peak inverse voltage could easily difficult the duty imposed on the ice the user has in mind. The reason have same values, but the duty im- tubes. for this lies in the inability of the posed on the tubes is by no means 2. A live load has more effect on ratings to completely define the capa- equivalent. the arc -back rate than a dead load. bilities of the tube. Arc -backs do not always occur A live load is one which has the Industrial tubes are rated in terms when the tube is deionizing, but may ability to store energy and feed of the maximum it inverse and forward occur at other times in the reverse back through the tube when voltage an in- and the peak and average voltage cycle. There is no definitely cipient arc -back occurs. current. That Connected these quantities are known explanation for arc -back, and electromechanical loads of high ener- not fundamental can be seen by con- probably no one cause. The expla- tia, electrical condensers, or chemical sidering the function the tube per- nation which seems most plausible cells may serve as examples of live forms through a cycle of its opera- for the arc -back at times other than loads, while inductance which tends tion. A gas -filled controlled rectifier deionization is that all times in- to keep the load current from re- prevents current from flowing as the cipient arc -backs may occur, which versing, or resistance which has no anode potential increases from a have a very short time duration. stored energy are dead loads. negative value with respect to the These current reversals seldom (Continued on page 110) 46 January 1942 - ELECTRONICS GRAPHS FOR TRANSMISSION LINES

The two graphs making up this Reference Sheet give the characteristic impedance of parallel wire or coaxial cylinder lines, together with the length of the line in electrical degrees or in fractions of a wavelength for capacitance shunted across sending end terminals and distant end short circuited

(4) the characteristic im- THE two graphs of this Reference BY BERNARD SALZBERG wires, and pedance of a uniform transmission line Sheet provide a quick and simple Washington, D. C. (1) the length of coaxial cylinders. The charts are means of calculating: necessary of a uniform transmission line required easy to use, for it is merely with the far end result of using the condenser, for the to determine the value of the quantity to establish resonance abscissa and short -circuited and a capacitance con- same conditions of operation as above, for the horizontal axis or (3) the characteristic impedance of a then read off the required value from nected across the sending end, (2) the at the amount of shortening of the line as a uniform transmission line of parallel the vertical scale or ordinate

Graph for determining the characteristic impedance of a uniform transmission line of either the parallel wire or coaxial cylinder type

90 0.250

- -0225 80 . ctr 0.200 e. ' .c 70 \e _ - .-- .61 _ \oe CO

- - -0.175 > - a 60 - 3 co - i n - LENGTH OFA UNIFORM TRANSMISSION LINE - 0.150 on - -o line c .c 50 Length of a uniform transmission - which is required to establish'

0 40 I - B = X ñ , 360° ZóÌ -0.100 c a) w o á 30 0 o - -0.075 +t 4------C _ 0) C11 - v - -J 20 - 0.050 - e

10 (90 -9) _ -0.025

0.000 OU.I 0.2 0 3 04 0 5 06 07 Q8 1.0 2 3 4 5 6 7 8 9 10 20 30 40 60 80 100 Ratio of Capacitive Reactance to Characteristance mpedance of Line (Xc/Zo)

ELECTRONICS REFERENCE SHEET point where the appropriate curve cor- in terms of fractions of a wavelength. cps) and a capacitance of 1,000 µµf relates the two coordinate axes. The second graph relates the char- (10-°f) is used at the sending end of For the graph giving the length of acteristic impedance of a uniform the line, the capacitive reactance is the transmission line, the horizontal transmission line with the dimensions Xc = 1/(6.2832 X 10° X 10-9) = coordinates are given in terms of the of either a coaxial or a parallel wire 1,000/6.2832 = 159 ohms, and the ratio ratio of the capacitive reactance of the line. The abscissa is given in terms of the capacitive reactance to condenser the line C to the characteristic im- of the ratio of spacing of the two con- impedance is X0/Z = 159/83 = 1.92. pedance of the transmission line. This ductors of the line, whereas the ordi- From the curve showing the length capacitive reactance in ohms is given nates are given in terms of the char- of the transmission line we find re- by the the equation, X, =1 /C2rfC, where f acteristic impedance of the line in quired length of the line 62 is to be de- the frequency in cycles per second, ohms. grees or 0.172 of a wavelength. and C is the capacitance in farads. In this particular The Example case the length electrical length of the line re- of the line, in feet, may be obtained quired to produce resonance may be As an example of the use of the very simply. Assuming the rate of determined in terms of the electrical graphs, assume we have a coaxial, uni- propagation length along the line at the speed of the line in degrees from the form transmission line whose inner of light, the required length in meters left -hand ordinates, or in terms of conductor is i -in. in outside diameter, is 300x0.172=51.6 meters or approxi- fractions of a wavelength from the while the inner diameter of the outer mately 170 feet. Therefore right -hand a coaxial ordinates. The degree of conductor is 1 inch. The ratio, do/d, line of the dimensions given, across one line shortening as a result of using the is consequently 4, and we find the char- end of which condenser is a capacity of 1000 µµf C, is also obtainable in terms acteristic impedance to be 83 ohms. must be 170 feet long to resonant at of the length in electrical degrees or If this cable is used at 1,000 kc (10° 1000 kc.

Graph for the determination of the length of a uniform transmission line which is required to establish resonance under the conditions stated on the chart. Line length is plotted as function of ratio of capacitative reactance to characteristic impedance of the line

900

l l i 11 i -_ - CHARACTERISTIC IMPEDANCE OF UNIFORM TRANSMISSION LINES 800

For parallel wires, Zo= 120 Cosh -IC(á )J 700 S= Wire separation / - d= Wire diameter -3d _ Fore-02>.> 1, Z0=276 Loa d 600 w For coaxial cylinders, Z0 = 138 Log á4. do= inside did. of outer cylinder diì¿ d0 ó dt= outside dia.of inner cylinder d c - ^0 500 N - - tes - u o 400 - - P _ V 147: - a, ú 300 t. a v der' I cylt0 200 ¡a

100

0 2 3 4 5 6 7 8 9 10 20 30 40 60 80 100 200 300 400 600 800 100 tá Spacing of Conductors, (7) or °i )

ELECTRONICS REFERENCE SHEET are precision . Cinch parts and permanence made for performance one can foretell ob of all ... No IN the bigg est J of the little -the p erfection upon so safeguard how much may depend easy But it is comparatively minutest detail. alert insure constant -and so perf rm nc - dep endability o into service. of parts to g the choosing satisfaction. CINCH in it's CINCH for connectors ... skilled, contact strips,p machinery and with modern large especially equipped small pparts in is for assembling labor, available Work. efficient of National Emergency facilitating production volume, Patents. H. H. Eby Socket licensed under Radio Sockets are Cinch and Oak Serves You and US

WEST VAN BUREN STREET CHICAGO, ILLINOIS CINCH MANUFACTURING CORPORATION 2335 SUBSIDIARY: UNITED -CARR FASTENER CORP. CAMBRIDGE, MASS. 49 ELECTRONICS - January 1942 drawn at a position on the chart where TUBES AT WORK the recorded amplitudes are at (or exceed) the specified level for 50 percent of the mileage represented by the A portable field intensity recorder, elec- segment line. The air-line distance from the station to the end of the segment tronic apparatus on exhibiton at the is the distance plotted for a point on a Chemical contour of specified field intensity. Exposition, a phototube width This field intensity recorder is par- gage, and nail detector ticularly adapted to obtaining this in- are discussed formation. The main unit can be installed on a small bench in front of an operator sitting in the rear seat of the New Field Intensity Recorder Requirements of the Federal Com- average motor car. All controls are munications commission By H. W. KLINE specify that facing the operator. Means for sup- broadcasters of f -m and television pro- porting the dipole antenna General Engineering Laboratory grams at the rear General Electric Co. obtain a knowledge of the dis- of the car can be installed at the op- tribution of field from their stations. tion of the user. The mast is usually CONTINUOUS RECORDINGS of the inten- This is done in order sities to register the high enough to elevate the dipole 10 of radiated fields from radio extent of the service area of a given feet transmitting stations above ground level. operating on fre- station, and to govern future alloca- In recording the intensities quencies of 26 to 155 Mc are of the possible tions for these types of services in a radiated field from W2XOY, radii were with the portable field intensity re- given territory. These corder findings must first determined as nearly straight as recently developed in the Gen- be submitted to the FCC within possible eral Engineering Laboratory one on roads from the transmit- of the year after a station goes on the air. ting station. One of these radii was General Electric Co. The broadcaster is usually This instrument required traveled ter a point sufficiently beyond can be used for re- to determine the pattern of distributed the level of 50 microvolts cording the tapering of field per meter to intensity fields at two levels -one millivolt per substantiate its location. The equip- as a function of radial distance from a meter and 50 microvolts transmitter. per meter for ment was then turned on and allowed It can be operated in a the f -m band. These signal levels are to record continually, motor car or at a fixed point the intensity for re- required when receiving on a dipole fluctuating with distance, due to local- cording field intensities of the various antenna 50 feet above the ground. ized classes of transmission, reflections and other effects. Be- such as fre- To plot the contours of these levels, cause of such fluctuations it was found quency modulation, television, com- it is necessary to munication, makefield intensity desirable to hold the car speed between or special service. surveys on eight different radii 20 A photograph from and 25 miles per hour. This allows of the main unit is the station. It is extremely difficult to the recorder sufficient shown in Fig. 1. time to record The overall dimen- obtain the correct position for a level the rise and fall of these peaks. sions of this unit are: 121 inches in unless this data is recorded. Another height, 31i inches field in which this instru- in width, and 10B The problem becomes more involved ment is applicable is inches in depth. It is furnished that of determin- with an in that the FCC requires that a point ing the effective radiation from differ- accessory case containing a long and on a contour shall be plotted a as repre- ent types of transmitting antennas. short adjustable dipole antenna, a sentative of the mileage to the end of Relative fixture common data can be obtained under to both antennas for a segment of length representing 10 actual operating conditions mounting them to which will a masthead, 30 feet percent of the radial distance from a result in improved designs of radiators of shielded transmission line of new, transmitter. The field intensity in low -loss this and higher radiation efficiencies for design, a flexible cable for segment must be that of the specified transmitting antennas. driving the recorder directly The recorder from the level, or greater, for 50 percent of the can also be used to determine the ex- speedometer of a car, and minor ac- distance within the segment. cessories. tent of fading and other characteris- On the record chart the correct value tics on these frequencies, well The total weight of as as for the accessory of amplitude is drawn, representing locating the proper site of a receiving case, loaded, is 17 pounds. The total the field intensity level specified. weight This antenna for optimum reception from of the equipment, ready to op- correct value of amplitude is also a given transmitter. erate independently in the field, is 69 pounds. Novel features incorporated into the design of the main unit include : (1) simple calibration, (2) the use of new, low-drain battery tubes, (3) the internal inclusion of the battery power supply, (4) the internal inclusion of a recorder, and (5) means for driving the recorder chart and marker from the speedometer of a car, thus gearing the chart to the road. Only two external connections to the unit are necessary. This is especially helpful in mobile installations, where space is limited. The connections are those of the transmission line, which connects to a socket in the front panel, and the flexible shaft which connects to the right hand side of the case. The present converter unit can be inter- changed with one extending the frequency range when desired. Optional accessories can be obtained for driving the chart of the recorder at fixed -point installation. This is explained in greater detail later in this Fig. 1 -The field intensity recorder is shown installed in an article. automobile. The recording mechanism is at the far right 50 January 1942 - ELECTRONICS Reducing Diet for Propeller Parts : SYNTHANE

VERYpound of weight saved means just the warship will find a larger place later that much longer range for a bomber, in appliances for the home, equipment for added payload for a transport. Light- weight the office and the factory. Synthane is used for many parts of air- Already, companies ... looking ahead ... planes, including propeller assemblies. are planning future applications using The same light weight, corrosion resis- Synthane Bakelite-laminated. If you have a tance,structural strength, dielectric strength, future use for versatile Synthane, why not machineability... and other properties that gain time tomorrow by working on it to- took Synthane into the plane, the tank, and day? We'll be glad to help you. SYNTHANF. TECHNICAL PLASTICS

GEAR MATERIAL SHEETSROM.STUBESFABRICATED PARTS SILENT STABILIZED A- Turned and threaded stud for SYNThANE seam shove. Bakelite-0 laminated B- Shaved and dri.led insulatcr C- Sawed, millec, drilled and counterbcred card gcide Incorporated into this equipment is a specially designed superheterodyne receiver having features desirable for For Your this class of service. The converter and calibrating oscillator were designed as an interchangeable unit capable of being changed to another converter DEFENSE unit to expand the frequency range if NEEDS desirable. The various sections of the main units are shown in Fig. 2. The total frequency range of this SEE equipment, from 26 to 155 Mc is obtained continuously by switching the calibrating oscillator and converter to STANCOR! three separate bands. Band A covers a range of from 25 to 50 Mc, band B a range of from 50 to 85 Mc, and band C a range of from 85 to 155 Mc. Both the calibrating oscillator and the heterodyne oscillator employ an acorn type 958 triode. Special types of tank circuits, for use with these tubes, were developed for bands B and C, enabling wide band operation. The circuits of the oscillators are similar; the heterodyne oscillator operates five megacycles lower than the signal frequency. This feature requires tracking compensation at one point only-in the grid input circuits of the converter. The converter tube is a type 1R5. Its function is to pass only the difference frequency of five megacycles by virtue of the beating of the heterodyne frequency with the signal frequency at its input. The converter component of five megacycles in the output circuit of this tube is delivered to the first intermediate frequency transformer. The secondary of this transformer is connected to a fixed capacitor attenuator. The output of this attenuator can be adjusted to 1, 6, 1/20, 1 /100, 1/500, 1/2000, or 1 /10,000 of its input voltage. Its accuracy is high for this type of equipment. The maximum error encountered on any tap was plus or minus 3.5 percent. The output of the attenuator is The three tiny hearing aid trans- connected to formers shown at the right have many the input of a 4- stage, in- defense applications. They are illus. termediate frequency amplifier. This (rated approximately one-half actual size. amplifier is designed for maximum stability and minimum regeneration. Four type 1T4 tubes are used. The gain is controlled by varying the negative d -c STANCOR transformers are giving a good account of them- bias on the grids of the first three selves in today's defense program. This is only natural tubes. The 88 -kc band pass of this because Stancor's plant facilities and personnel are long amplifier allows a deviation from its accus- mean tomed to the manufacture of special transformers to customers' resonant frequency of 5 Mc to a exacting requirements. frequency plus or minus 44 kc. The output of the i -f amplifier is applied Whether to the diode elements of a type you are making communication equipment, public 1S5 diode pentode tube. This is the address systems or any other electronic apparatus requiring final tube in the line -up. This tube the use of transformers or reactors, regardless of how stringent rectifies the intermediate frequency the specifications may be Stancor will be pleased to assist you voltage to a direct -current bias which with your problem. is applied to its pentode grid. If there is audio frequency modulation, this Illustrated above are some component is also applied to the pen- of the various types of special tode grid simultaneously mountings made to customers' specifications. with the d -c bias. The pentode half of the tube functions d Write as a -c and audio fre- Dept. D -1510 for assistance with your specific problems. quency amplifier. In measuring the field intensities of f -m stations, it was found that modulation had a negligible STANDARD TRANSFORMER effect on the results. SS CORPORATION The negative bias voltage from the 1500 diode when NORTH HALSTED STREET . CHICAGO applied to the grid of the pentode causes a reduction in the plate 52 January 1942 ELECTRONICS IRC

MORE IRC RESISTORS ARE

USED IN DEFENSE EQUIPMENT, BOTH HERE AND ABROAD, THAN ANY OTHER MAKE

WRITE FOR THESE RESISTOR ENGINEERING DATA BULLETINS (Please ask for them by number) BULLETIN I -Two sizes "Metallized °and Wire Wound Volume Controls and Potentiometers up to 2 watts and 20 megohms resistance.. BULLETIN I I -Metallized-type Resistors: 4 insu- 10 high fre- lated sizes, % -, 1/2 -, 1- and 2- watts; quency sizes, %- to 150- watts; 4 ultra -high range sizes; 5 high voltage and high frequency power sizes; 5 suppressor sizes. BULLETIN III - Insulated Wire Wound Resis- tors: 7 sizes from 1/2- to 20- watts. BULLETIN IV- Power and Precision Wire Wound Resistors: 53 sizes of fixed and adjustable power types from 10- to 200-watts; in a wide variety of shapes, mountings, etc. Inductive and non -inductive. 14 Precision Wire Wound Resistor types to as close as 1 /10 of 1% accuracy. BULLETIN IV- B- Sealed Precision Voltmeter Multipliers, 2 sizes, 1.0 megohm to 5 megohms resistance and 1 kilovolt to 5 kilovolts. Impervious to moisture. BULLETIN V -Attenuators: Unique new IRC molded motor commutator type 20 -step Attenu- ator; also, conventional 30-step units. Ladder, potentiometer or bridge T. all - BULLETIN V I - Quick heat dissipating metal Rheostats, 25- and 50-watts. 2 -watt Wire Wound Potentiometer and Rheostat. .. Pa. I ` fiIO ' AL R ÉIST C i 'r' ANY, 401 N. Broad St., Philadelphia, ELECTRONICS - January 1942 53 current of the pentode. A visual meter, recorder, and audio frequency impedance are connected in series and form the plate load of the pentode. The two instruments are operated by the change in plate current. They are first set, under no- (WEAF transmitter of signal conditions, to read zero Port Washington, by putting a bucking current through N. Y., them. When a reduction in plate current is effected, the compensating current causes an effect equivalent to increasing the current through the instruments, making them read up -scale proportional to the applied grid bias. The deflection of the recorder needle is the same as that of the visual meter. A telephone jack is connected across the audio frequency impedance so that the modulation can be monitored with ordinary headphones. Before recording, the gain of the intermediate frequency amplifier is pre- set by applying a known voltage at signal frequency from the calibrating oscillator, with the attenuator on a specified tap, and with the transmission line disconnected in case the signal level is high enough to interfere. The signal to be measured is inter- cepted on the horizontal dipole antenna, which is adjusted to a length commen- surate with the signal wavelength. The transmission line is connected to the dipole at points of low impedance. The receiver end of the line terminates in the low of the convertor unit's input circuit or at the same point at which the calibrating voltage from the calibrating oscillator is applied.

First i -f I-F [I M A C «cftQiWi,le>1 trans- - former - Amplifier

1f2 trhtch C A L L I T E Power su pply H T was axiomatic that tube operating efficiency decreased as size was increased - until Eitel- McCullough revolutionized tube design by mounting four triodes within a single envelope. Fig. 2 -Block diagram of the portable field intensity recorder Today the Eimac 304T tube, pictured above, is seeing service in the key sockets of the world's most important transmitters including new FM installations. Although The fundamental calibration of essentially a low voltage tube the 304T is often used with this as much as 20,000 volts complete unit was made in the field by on the plates, 10 times the rated voltage. Contributing to this stamina are grid and coordinating deflections obtained with plate leads fashioned from Callite tungsten rods and Callite thoriated filament - fields of known intensities over its eloquent evidence of Callite dependability. signal frequency range. The signal amplitude capabilities, given for the There is a large group of Callite Tungsten products, each designed to do a extreme frequencies are 15 to 600,000 particular job better. Callite research and resourcefulness have contributed to microvolts per meter at 26 Mc, and 125 to 3,000,000 microvolts countless technical and scientific developments. If you have per meter a special problem, at 155 Mc. The minimum amplitudes why not consult Callite's engineering department today? give instrument deflections of 20 percent of full scale with Specialists in the manufacture of electrical contacts of refractory and precious metals. an attenuator bi- metals, amplitude pass of 1.0. lead -in wires, filaments and grids -formed parts and raw materials for all electronic applications. Frequency -modulated stations are identified, orally, by slight signal de- CA tuning so that deviation of the signal LLITE is i CORPORATIONTUNGSTEN linear over the -f band pass characteristic. Recordings are made on 644-39th STREET TUNGSTEN UNION CITY, N. J. peak tuning, however, where modulation has negligible effect on the results. l'il!I(gTi A modified G Cable: "CALCITES^ Branches: Chicago. Ill. Cleveland. O. -E inkless recorder, type CF2, is used for recordings. The 54 January 1942 - ELECTRONICS ------14.----.-

ftsymooM

NOWHERE is dependable material provides the necessary heat-resisting service of greater impor- qualities required in the special units for tance than in power sta- high - capacity applications. tion equipment. Failure of a single component Lava combines this valuable property with may cause interruptions over wide areas. high electrical resistance at room and ele- Certain larger sizes of the well-known current - vated temperatures. limiting resistors made by Schweitzer and The manufacturing cost of Lava is reasonable, for Conrad, Inc., have cores made of Lava both in small and production quantities. supporting the resistance wire. This insulating material, which has proved its value for Mechanical and electrical properties of Lava over fifty years, has been chosen in this mod- are well defined and engineering data will be em equipment because no other insulating gladly sent on request.

Trade ?stark Reg, U. S. Pat. O. AMERICAN LAVA CORPORATION CHATTANOOGA TENNESSEE BOSTON PHILADELPHIA WASHINGTON, D. C. CHICAGO CLEVELAND NEW YORK ST. LOUIS LOS ANGELES SAN FRANCISCO

ELECTRONICS - January 1942 modifications consist of the addition of a gear train for driving the chart and marker at rates found by experience to be best for this class of service. This . recorder imprints a record on its chart by action of a cam -driven hammer which strikes the deflecting needle of the movement. By this action, the needle is pressed against the back of the chart. A typewritter ribbon runs across the face of the chart so that each time the needle is struck, a dot is impressed on the chart. The shaft driving the chart and hammer extends through the right hand side of the case together with a gear shift knob. The end of the shaft is fitted with a universal key allowing drive either by Telechron motor or speedometer. For mobile measurements, the recorder is mechanically driven by the car speedometer. Fittings are furnished with the flexible coupling shaft to enable connecting it in series with THE ONLY the speedometer without interfering with RESISTORS WOUND the normal speedometer action. WITH With this drive, the chart speed is 1 CERAMIC INSULATED* WIRE inch per mile and the marking rate is 240 *Flexible.. dots per mile. Moisture -proof .. 1000° C. For fixed point recordings, heat -proof .. withstands high voltage the chart can be driven by a 1 rps Telechron motor at a rate of 2 dots per second. Power Supply The battery complement for this equipment consists of a 1.5 -volt dry THESE RESISTORS DO THE cell, a 4.5 -volt bias battery, and 3 medium- sized, 45 -volt plate batteries. JOBS Access to the compartment holding the THAT COULDN'T BE DONE batteries is obtained by removing the back ... and the reason is this: Whereas of the main unit. other resistors are space -wound with bare Initial amplitude wire, Sprague Koolohms are layer -wound calibrations of the with wire that is insulated before if is field intensity recorder involve errors wound with a special ceramic material. This insulation is so flexible it can be wound not exceeding plus or minus 10 percent on small forms without cracking. It is so moisture -proof it excels in any moisture of true levels. test -so heat -proof that the insulation is actually applied to the wire at 1000°C. Repetitive surveys on a given radius -and so good as an insulator that it has an insulation strength of 400 volts per showed that the 1 millivolt and 50 mil. at 350° F. Small wonder then, that Koolohms outlast, outperform old style re- microvolt per meter levels could be as- sistors where shorted windings cause trouble, where bare wires must be protected certained with an error of considerably by outside coatings less than plus or 5 of brittle cements and enamels and where heat and moisture minus percent in represent problems that have true distances. been only partially solved. Koolohms are smaller, sturdier, better protected. They are more accurate -and they stay accurate because windings will not short. Your inquiry will bring the complete Koolohm Catalog, samples and engineering information.

Koolchm wire with sec- Electronics at the tion of ceramic insulation removed to show contrast Chemical Exposition between bare and insulated v. ire. EVIDENCE THAT ELECTRONIC METHODS UNEXCELLED FOR DEFENSE APPLICATIONS are being used to a large degree for Not only are Koolohm Resistors approved industrial purposes was less space; larger, sturdier wire sizes; seen at the for much defense equipment but, in various 18th Exposition truly non- inductive units, even at 50 to of the Chemical In- instances, Koolohm insulated layer -wound dustries held in New 103 Mc.; faster heat dissipation; easier York during the construction and design week of December 1. features have mounting; greater humidity protection; Electronic equip- enabled defense manufacturers to ment was exhibited by meet closer accuracy; and an absence of at least 14 dif- heretofore "impossible" specifications. ferent companies and brittle cements or enamels that so often ranged from the Koolohms mean higher resistance in chip, peel or crack. familiar rectifier sets to new devices which record the voltage- current curve S P R A G U E S P E C I A L T I E S C O M P A of a solution under certain conditions RESISTOR N Y DIVISION NORTH ADAMS, MASS. by which an analysis of the solution can be made. By little more than cas- ually examining the exhibits and looking for electronic equipment, your editors were impressed with the growth of electronics in chemistry since the last chemical exposition held in New York two years ago. (Continued on page 58) 36 January 1942 - ELECTRONICS NSR A ó

..designed to stand severe conditions ! When requirements call for an insulation that will do more than the average job - an insulation that will "stand the gaff" . . . specifications calling for TURBO provide complete insurance. Higher dielectric constants, abrasion resistance and the overall protection of inside impregnation always stand guard. TURBO is especially suited for the vital spots of vital machines, generators, motors, transformers, switchboards, etc., that are relied on for trouble -free service. A free sample card mounted with samples will be sent on request. A ready reference and handy gauge. WILLIAM BRAND & CO. 276 Fourth Ave. New York N. Y. 325 W. Huron Street Chicago. Ill.

VARNISHED TUBING SATURATED SLEEVING CAMBRICS

VARNISHED TUBING

NOW (TURBO GLASS) VARNISHED TUBING in complete range of A.S.T.M. standard sizes. Send for sample strands and engineering data. IN GLASS TUBING TOO -IT'S THE VARNISH THAT COUNTS

ELECTRONICS January 1912 57 Mercury vapor rectifiers were shown by General Electric Co., Westinghouse Electric & Manufacturing Co., and Allis- Chalmers Manufacturing Co. FOR EVERY SMALL CIRCUIT These rectifiers are intended for use in power systems for electric arc welding, manufacture of aluminum, and for all kinds of d-e machinery. It was stated at the GE exhibit that mercury vapor rectifiers having a total capacity of 674,422 kw. had been sold to the chemical industry alone by Gen- eral Electric. This is an impressive figure by itself and if the totals for the other rectifier manufacturers and for other industries are added to it we have HAS THE a rough idea of the importance of SWITCH YOU NEED! rectification to American industry. Selenium rectifiers manufactured by International Telephone & Radio Manu- SINGLE POLE - SINGLE THROW facturing Corp., were exhibited by Fansteel Metallurgical Corp., Chicago. These rectifiers can be arranged in single -phase or multiphase circuits to provide half-wave or full -wave rectification. They find use as the d -c power source in a wide variety of applications MODEL SS -I . Slide ac- including battery chargers, arc weld- tion switch suitable for two - ing, burglar alarms, carbon arc lamps, position tone control, sensi- counting machines, elec- tivity control, line switch for and grading small sets, small motor con- trical precipitation, electroplating, rail- trol, tap switch for power way signalling, and therapeutic equip- transformers and many ment. other uses. Carries Under- Another rapidly growing field is the writers' Approval for .75 electrostatic separation of dry powdered amp., 125 volts. materials having different electrical sus- ceptibilities. The electrodes are supplied with very high d -c voltages. of the order of 15,000 volts, either by elec- FOUR POLE - DOUBLE THROW tronic rectifiers or by motor -generator sets. Exhibitors of electrostatic separators were Sutton, Steele & Steele, Inc. of Dallas, Ritter Products Corp. of Rochester, and Separations Engi- neering Corp. of New York. A partial MODEL SS -12 . . . Slide list of separations possible by this action switch for circuit method are as follows: changing and a wide va- 1. riety of applications to all Sphalerite (zinc blend of the rosin types of electrical equip- type) and barite from iron and copper ment. Underwriters' Ap- pyrites. proval with a .5 amp., 125 2. Graphite from mica. volt rating. Terminals in two 3. Biotite micas from the muscovites. planes, extremely accessible 4. Garnet from iron pyrites and for wiring. Mechanically metal particles. rugged; fully enclosed. 5. Silica from fluorspar. 6. Purification of barium spar from iron and other minerals. 7. Zircon from rutile. 8. Steel grindings from abrasive STACKPOLE SWITCHES are designed to out-per- grains. f orm any switch in their class regardless of price! They Commercial capacities of the order of are available from single pole to four pole models and in 5,000 pounds per hour on materials any combination between these extremes. They are de- finer than 60 mesh are being obtained. signed A number of different instruments and constructed by an organization of engineers depending upon the change in fre- and craftsmen with years of experience and leadership quency of an oscillator were shown by in this field. Rugged construction, precision workmanship the Wheelco Instrument Co., of Chi- and operating efficiency insure trouble -free performance. cago. The essential feature of the oscillator is a pair of coils between which Samples and prices sent on request. a vane passes when it is desired to make some change in the process. A typical illustration is a meter or a gage with a light metal vane attached to the pointer and with the oscillator coils placed at some desired point which may or may not be adjustable. When the value measured by the in- ST. MARYS, PENNA. U. S. A. strument reaches a critical value, the pointer moves across the scale and the January 1942 - ELECTRONICS STATION MONITORING IS EASY

with this G- unit

Distortion is prevented by careful adjustments on a G -E wide -band oscilloscope.

Approved by the F.C.C. With this new nioni =or, General Electric laas removed one more hurdle from your path to FM. You will find this self - con = aired, multi -purpose* instrument one of the most valuable units in your FM station. Who It provides: FM Pioneers Some of the G -E Monitors Direct reading of center -frequency deviation (with or without Already Bought * Have Sacramento. Cal. modulation) t Royal Miller. Broadcasting Co.. John L. Booth Midland Broadcasting Direct reading of modulation percentaget Mich. Mo. * Co., Detroit, Inc.. sas City. Co.. Institute, Chicago Capitol Broadcasting Moody Bible Instant calibration against a precision crystal standard N. Y. New York * Schenectady. Syndicate Co., Broadcasting Sys- News Columbia Y., and Adjustable modulation -limit flasher New York, N. ewsS Engineering Y. * tern, units; Long Island City, N. Ill. (Five San output for audio monitort Chicago. for "S -T" o City Schools, * High fidelity three of these San Diego Cal. Diego. Los System,y Broadcasting Co.. be reached easily through the Don Lee eleadal. Standard units, one All tubes and crystal units can Angeles, Cal. (Two Los Co Angeles,Ano service l chassis assembly from cabinet Broadcasting these for "S -T" top of the cabinet. Removing FM Rade N. Y. Urbana. New York, of Illinois, access to all panels and wiring. Inc., Co.. Schenec- University allows complete General Electric one Ill. (Three units; Radio Cor- tady, N. Y. Walker- Downing necessity. This for "S -T" service, h Pa. In FM, more precise measuring techniques are a these sound) poratn.Pittsburg for television g Corpora - Order your and one Broadcastin instrument is custom -built for your requirements. Gray, Winston-Salem, WFIL Pa. Gordon lion. Philadelphia, G -E office, or direct from Ia. monitor now through the nearest N. C. Milwaukee, Inc., Chicago. Journal Co.. WGN, ass Radio and Television Dept., Schenectady, The Networkk Paxton.M General Electric, Wis. Y ankee ton. N. H Stockholm, Mt. Washing New York. Johan Lagercrantz, and Sweden tProvision has been made for remote c)ns. 1e operation.

C. FOR ALL YOUR FM NEEDS f- Tubes FM Broadcast Transmitters Relay Transmitters Receivers for Home FM Police ant Emergency 250 to 50,000 Watts and "S -T" Service Transmitters ad Receivers GENERAL ELECTRIC vane passes between the coils thereby changing the frequency of the oscillator. This causes the plate current to change by a sufficient degree to permit the operation of a relay. This principle has been applied to a large number of processes ánd Wheelco has developed several types of controller heads for various applications. An immersion head, which operates the oscillator circuit when a liquid rises and immerses it, consists of two metallic plates of a condenser. When the liquid passes between them the dielectric constant is changed. This changes the capacitance of the circuit which in turn changes the frequency of the oscillator. A controller head for attachment to the exterior of a glass liquid level guage is also used. A photoelectrically controlled scale was shown by the Kron Scale Co. of Bridgeport, Conn. A phototube is located behind a window in the pound scale with a lamp directly in front of it. As the load is placed on the platform of the scale the pointer rotates and when it reaches the desired point where the phototube is located, the pointer covers the window, shutting off the light to the phototube. Two titrimeters using electronic amplification were demonstrated by Eimer and Amend, New York and Fisher Scientific Co., Pittsburgh. End points of chemical reactions are char- acterized by changes in the conductivity of the solution. Therefore, the end point of a titration can be indicated by a change in the flow of current through the solution upon the application of a known voltage. The Junior titrimeter uses d-c amplification to in- ay,iZedf crease the current to deflect a fairly Kt rugged milliameter. The Senior model also uses d -c amplification, but with a TRANSFORMERS OF ALL cathode -ray indicator tube of the 6E5, 6G5, etc. series as the indicator for TYPES UP TO the end of titration. Once these instru- 1OKVA ... ments have been standardized and a titration curve set up, routine titrations The Chicago Transformer Corporation specializes in, and is can be conducted very rapidly. The unusually well equipped Junior titrimiter is applicable to oxida- to handle, both the design and tion- reduction, acid -base, and precipi- the manufacture of Custom Order Transformers for new and tation titrations, but not for titrations requiring a glass electrode system. The difficult applications. Senior model can be used, in addition to those titrations mentioned above, for A large and competent staff of electrical and mechanical pH work, d-c resistance and voltage engineers, working in a most modernly equipped laboratory, measurements, and conductivity titrations. An electrophotometer for use in have spent experience -building years in creating transformers colorimetric analyses was also demon- for unusual uses. strated by these companies. This instrument uses two phototubes to corn - in It Given the application description, and the pensate changes line voltage. electrical results can be standardized very quickly and desired, the Chicago Transformer organization should best be readings can be made in a few seconds. able to solve your new An electrophotometer for colori- and difficult transformer problems. metric analysis of solutions was also shown by the Fisher Scientific Co. In this instrument a light beam is passed through a standard solution in a standard container to maintain the same distance through the solutions and CHICAGO TRANSFORME through a solution of unknown concentration. By the difference of light ab- C O R P O R A T I O N sorption of the standard and unknown solutions, the degree of concentration 3505 WEST ADDISON STREET CHICAGO can be determined. Where a large num- (Continued on page 64) 61I January 1942 - ELECTRONICS Argus, Guardian

Watchful, hundred-eyed Argus, of mythological fame, examines all units, its concern to see that all meet them. had a principal role. He was guardian for the gods. fully the rigid specifications demanded of ¶Equally important in the radio field is the part ¶With modern precision testing devices and up -to- played by another guardian- Collins inspection date methods, Collins inspection department is our department. All- seeing as Argus, inspection's concern keeper of quality, your guardian of reliability in is the close surveillance of components and parts your Collins transmitter.

that go to make up a transmitter. Inspection COLLII`S ILAIIIO COMPANY CEDAR RAPI DS, IOWA NEW YORK, NY: 11 WEST 42 ST. facture the reader will find the history of the lead -acid battery, chemistry New Books and construction of pasted plates, data on separators for lead -acid cells, con- tainers and types of cells. Then follows a description of the Edison cell. A chapter on the electrolyte discusses the properties of sulphuric acid solutions, measuring the solution, the effect of impurities in the electrolyte, and properties of alkaline electrolytes. A chapter deals with the theory of re- Theory of Gaseous Conduc- formation will be invaluable to him actions, energy transformations and in providing a basic understanding voltage -which is the theoretical section and Electronics for the conduction of electric current tion of the book. Other chapters deal with methods of BY through gases. The chapters on electron FREDERICK A. MAXFIELD, U. S. emission rating capacity, methods of operating Naval Ordnance Laboratory and R. treat the subject in the usual way common to engineering and charging batteries, testing bat- RALPH BENEDICT, Assistant Professor teries, present day applications, etc. of Electrical Engineering texts and discuss thermionic, field, and at the Uni- photoelectric versity of Wisconsin. 483 pages. emission. The chapter in Illustrated. Price $4.50. McGraw -Hill the book by Maxfield and Benedict is Book Co. much more complete on this subject and provides a general introduction to Photo Relays : some of the more elementary consid- Their Theory Gaseous Conductors- Theory erations in two, three and other multi - and Application electrode tubes. On the other hand, the and Engineering Application text by Cobine is much more complete BY F. H. SHEPARD, JR. Printed by Manville Press, Inc., New York BY with regard to material on the rectifi- City. JAMES DILLON COBINE, Assistant 28 pages, illustrated. Price 25 cents. Professor of Electrical Engineering, cation of current by vacuum and gas- Harvard University. 606 pages. Illus- eous discharge tubes. In fact, the chap- THOUGH A COMPREHENSIVE and detailed trated. Price $5.50. McGraw -Hill Book ter on rectifier circuit theory contains treatment of this subject is beyond Co. about as complete an analysis as has the scope of this booklet, it covers the so far appeared in American text- field in an interesting manner. The THE TWO BOOKS ENUMERATED ABOVE, books. language is non -mathematical and easy and released by the publisher at While it is to be regretted that two to understand. The topics treated are approximately the same time are suffi- books on essentially the same subject photoelectric phenomena, amplifiers, ciently closely allied to one another have appeared almost simultaneously, glow discharge tubes, light sources, and that they will be treated in a single either one will provide an excellent applications. The booklet might well review. Indeed, the scope and general text for reference work for those who serve as an introduction to the photo- treatment of both books is quite similar are fundamentally interested in the electric field for those engineers who and there are chapters in each covering conduction of electricity through gases may be a little rusty on their knowl- electron emission, arc discharge, kine- from the point of view of the physical edge of this rapidly expanding branch tic theory of gases, ionization of gas operation involved rather than from of electronics. -E.E.G. and glow discharges. Both books are the point of view of applying the prin- intended for the upper class or gradu- ciples in engineering practice. The ate student in electrical engineering rather considerable amount of mate- and physics, both bridge the gap be- rial on such subjects as the deionizing It's About Time tween the better known physics text processes, sparking potential and co- on kinetic theory of gases and the rona By PAUL M. CHAMBERLAIN, Richard discharge, glow discharge, the arc R. Smith, New York, engineering texts on the theory and discharge, space charge, plasma, 1941, 490 pages. and Price $7.50. application of electron tubes, and the gas discharge light sources will be point of view and general method of particularly useful as reference mate- "IT'S ABOUT TIME" is all about time- treatment is similar in both cases. Of rial to communication engineers whose pieces, written by a structural engineer course, as might be expected from au- previous experience and training has with a hobby of collecting old watches. thors working independently, there are been largely confined to a study of the As a book for the expert on watches certain subjects treated in one of these theory and application of vacuum and other timekeepers, this book is a which are not treated in the other. tubes but who feel the need for be- beauty; and for anyone whose hobby In the case of both books, the em- coming more familiar with the whole is watches, it is a "must." phasis has been placed upon the field of electronics. The book is divided into three broad underlying principles involved rather This reviewer believes that those in- sections, the first devoted to escape- than upon current engineering prac- structors having need for a text on ment mechanisms, the most complex tice. For this reason both should pro- gaseous conduction would find either and vital part of any time-telling ap- vide a sound basic training for the of these recent books well suited to paratus. The history of the escape- physics or electrical engineering stu- their purpose. -B.D. ment as it developed into modern dent for a number of years to come practice is written in such a manner and should be affected little, if at all. than anyone not necessarily interested by changes in engineering practice. in time pieces, can find both pleasure The engineering student making his Storage Batteries and information by the reading first acquaintance with electronics and thereof. The second part deals with the By GEORGE WOOD VINAL, Sc.D., Na- theory of gases may be somewhat tional Bureau of Standards. experimental and unusual time pieces disturbed to find a John rather considerable Wiley & Sons, Inc., New York. -such as those ingenious instruments section of each of these texts is devoted Third Edition. 1940, 450 pages. Price which strike the hours, or tell the time to the kinetic theory of gases, to the $5.00. of sunset or sunrise -the development motion of charged particles in a of watch regulators, etc. Finally a vacuum or gas, to a discussion of the "A GENERAL TREATISE on the physics section on famous watchmakers closes electrostatic field, and to the mechan- and chemistry of secondary batteries the volume. ism of ionization and deionization and their engineering applications." Throughout, the book is most inter- which subjects are adequately covered This is exactly what this book is. estingly written, and most adequately in both texts. Nevertheless, such in- Under materials and methods of manu- and beautifully illustrated. -K.H. 62 January 1942 - ELECTRONICS How Important is a Filament?

Zt's a well known fact that the vacuum tube is the filament will function at top efficiency. Contributing heart of radio communications, but it is important to factors to this efficiency are: Tantalum plates and grids remember that the filament is the heart of the vacuum and the super -vacuum which removes all contaminat- what tube! Thus, the efficiency with which these tiny strands ing gas particles. All these factors and more are of tungsten wire perform may mean the difference make it possible for Eimac tubes to carry the uncon- between success and failure of the tube itself...victory ditional guarantee against emission failure caused by and defeat for tanks or battleships ... life and death gas released internally. for millions of people. You can't always tell by appearance whether a fila- Eimac's unusual performance capabilities are ment is efficient or not. The two assemblies shown receiving enthusiastic acceptance in all branches of above look exactly alike but when put to the test one the service ... ARMY, NAVY and the AIR CORPS may not do its job. Into the production of filament for Eimac tubes has gone much research and experimentation. Among the many special instruments de- Follow the leaders to signed and perfected by Eimac to insure perfect filaments, none is more interesting than the electron mic- roscope which virtually gives a moving picture of how works under actual operating conditions. a filament Eitel-McCullough, Inc. Behind every Eimac tube is the assurance that its San Bruno, California

Foreign Division: FRAZAR & CO., LTD., 301 Clay Street, San Francisco, California, U.S.A. (Continued from page 60) ber of determinations are to be made a calibration curve made with known con- centrations of solution will speed up the operation by an appreciable amount. A voltage regulated power supply is used to assure constant reading in spite of varying line voltages. The American Instrument Co. of Silver Spring, Md. exhibited a Polar - ometric Analyzer for the analysis of solutions by the use of a dropping mercury cathode. A pool of mercury lies at the bottom of a glass container and acts as the anode of the system. Im- mediately above it is the solution to be analyzed in which is immersed the dropping mercury electrode which acts as the cathode. A direct voltage is applied between the anode and cathode as shown in the diagram. As droplets

-To amplifier +and recorder Dropping mercury cathode-

Solution - Charged mercury Mercury,, drop lets anode'

Diagram showing the principle of operation of the dropping mercury cathode of mercury drop from the cathode they are negatively charged. The degree of charge is a function of the voltage applied to the electrodes. Positive ions of various elements are attracted to the mercury droplets as the applied voltage is increased. This changes the amount of current flowing through the system. By noting the variations of current through the solution as the voltage is increased and by referring to previously prepared data or calibration 4% curves, the elements contained in the solution can be determined. The current is amplified by a vacuum tube amplifier and applied to a mechanical recorder which produces a voltage -current curve. Two magic eye tubes are - also used for indication of null points of bridge circuits during calibration of CommunicationC ormn l.Ì shed the instrument. estabi The measurement of hydrogen -ion concentration (pH value), an indication Sfer ' of acidity or alkalinity of solutions, nsOrn ' can be made with pH meters shown by t tra Coleman Electric Co. of Maywood, Ill. wth° and National Technical Laboratories of but not transformers! South Pasadena, Calif. Spectropho- tometers for determining the light ab- dependable sorption characteristics of solutions were also shown by these companies. A light beam from an incandescent lamp is passed through a prism which can be rotated so that any portion of the resultant spectrum can be made to pass through a narrow slit and then through the solution to a phototube. Thus, the absorption at any portion of the spectrum can be measured. The Wheatstone bridge has been ap- THORDARSON ELECTRIC MFG. CO., CHICAGO, ILL. plied to several instruments shown by Industrial Instruments of Jersey City, Transformer Specialists Since 1895 N. J., for the measurement of con- 64 January 1942 - ELECTRONICS Low resistance high cur- YEAR rent to glass seal- YEAR after copper ed plate connector. Op- erates at much lower temperature than ordi- Gammatron tubes have set the nary tungsten seals. pace. Note the "Firsts "... by the pioneers in the tantalum tube field.

Plate cap for improved UHF efficiency confines entire electron stream and protects glass from electron bombardment. 411

Mechanically rugged plate support. Has low Large, low inductance, lead inductance for UHF copper to glass seal grid operation. connector.Tantalum channel grid support is rugged and short ...UHF neutral- ization is easy.

Tantalum date and grid. Cleaned, processed and pumped by improved Gammatron methods.

Sturdy, long life filament is specially processed to give mcre than ample emission Flament stem is shielded from electron bombardment.

It is reasonable that radio engineers think first of Gammatrons when new designs are considered. Because, they know that select- ing Gammatrons assures the maximum UHF efficiency, protection against failure through overload and extra long life. Write for data. GAMMATRONS of course!

HEINTZ & KAUFMAN LTD.. SOUTH SAN FRANCISCO, CALIFORNIA, U. S. A. ductivity of solutions and the resistance of various types of insulation. The concentration of solutions and impurities in solutions can be determined by the use of the Solu Bridge which uses a cathode -ray tube of the magic eye type as the null point indicator. This instrument measures the conductivity of a solution and by the use of previously obtained data with standard solutions, any impurities can be detected and the concentration of any electroly- tic 'solution can be determined. The Megabridge insulation tester, also using a Wheatstone bridge with a magic eye null point indicator, for the measurement of resistances from 100,000 ohms to 100,000 megohms was exhibited by this company. Also shown was a bridge for laboratory use for the measurement of resistance over the range from 0.2 to 250,000 ohms measured resistance and 0.2 ohms to 2i megohms specific resistance with an accuracy of one percent. Equipment for the measurement of vitamin concentration was demonstrated by Photovolt Corp. of New York. Under proper excitation by light from a mercury vapor lamp, vitamin A in solution will fluoresce. Advantage is taken of this phenomenon by using a barrier - layer photocell to measure the intensity of the fluorescence under known conditions for the determination of the concentration of vitamin A. It is also known that vitamin B will absorb light from the Original by in the 328 millimicron region (ultra- Allen Houser, Grandson of Geronimo violet) to a greater degree than at other wavelengths. Therefore an argon lamp, rich in ultraviolet light, is used to pass a light beam through the vitamin B solution to a phototube (type &frivtlie 929). By the degree of absorption the concentration can be determined. A photoelectric colorimeter was also shown by this company for the determination AMERICA DEPENDS ON of the characteristics of solutions. . s s 1xsy Photoelectric by GUARDIAN Width Gage BY E. H. ALEXANDER LAND . . . SEA . . . AIR . . . Industrial Engineering Department, Guardian is ready with controls approved General Electric Co. by the U. S. Army -Army Air Corps As ANOTHER EXAMPLE of the increasing - use of electron tubes for industrial Navy Naval Air Corps Marine Corps - - purposes, mention may be made of a -Signal Corps- Ordnance. recently developed instrument for measuring the width of flat strips or webbing GUN SWITCH during production, with the HANDLES possibility of controlling the manu- Samples of Approved REMOTE FIRING EQUIPMENT facturing operations in accordance with the desired strip width. TURRET CONTROLS Controls Available The half-tone illustration, Fig. 1, on Short Notice RADIO CONTROLS shows the general appearance of the photoelectric width gage, which is NAVIGATION CONTROLS normally divided into a left -hand and AIRCRAFT CONTROLS a right -hand phototube unit, and a width indicating instrument. The dia- BOMB RELEASES gram of Fig. 2 will illustrate the principle of operation, even though only one -half of the gage is indicated. The strip of material is made to pass GUARDIAN ELECTRIC between two detector units, one at 1625 West Walnut Street Chicago, Illinois each edge of the strip. Each of these detector units has a standard light I ARGEST LINE OF RELAYS SERVING AMERICAN INDUSTRY source, lens system, and mirror for 66 January 1942 - ELECTRONICS the SECO automatic VOLTAGE REGULATOR

THE MODERN A -C LINE VOLTAGE CONTROL

This improved type regulator consists of a thyratron tube circuit controlling a motor- driven variable voltage transformer. It maintains a constant output vol -age with variations in input voltage or load current.

CORRECTS FOR WIDE RANGE OF INPUT VOLTAGES voltage -standard I 15 volt units, for example, correct for input variations of plus and minus 17.5% of output voltage. HIGH EFFICIENCY -has the high efficiency chardcter- istic of the variable voltage auto -transformer. NO INTERNAL MECHANICAL ADJUSTMENTS - does not use a contact- making voltmeter -no critical relay adjustments. OUTPUT VOLTAGE AND SENSITIVITY ADJUSTABLE over a wide range by means of knobs on front panel. NEGLIGIBLE WAVE -FORM DISTORTION - low exciting current. LOW COST PER KVA. QUICK RESPONSE -time for full range travel is six seconds. OPERATION NOT AFFECTED BY LOAD POWER FACTOR. APPLICATIONS Maintains correct constant voltage for- Electronic Equipment Manufacturing Equipment Electrical Testing Fluorescent Lighting

SEND FOR BULLETIN 163LE

up to 75 KVA-single or three phase. Available for I I5, 230, or 440 -volt circuits in capacities SUPERIOR ELECTRIC CO. 35 HARRISON ST. BRISTOL, CONN. ELECTRONICS January 1942 67 producing a beam of light which is projected from above to the edge of TWO VALUABLE NEW FEATURES the strip, where it is partially interrupted. The portion of the beam which HAVE BEEN is not interrupted is focused by a ADDED TO THIS lens system onto a photoelectric tube located below the strip, and this light - PRESTO RECORDER! sensitive device allows a flow of electric current proportional to the amount of light falling on it. Because the mirror of the optical system is mounted on the movable element of a D'Arsonval type movement, rotation of the instrument element causes the beam of light, which is projected from the source to the mirror, to sweep angularly in a plane vertical to the plane of the material, and at right angles to its direction of travel. Thus, the movement of the galvanometer mirror is capable of projecting a beam of light on the edge of the material, even though its side register should shift within al- lowable limits.

Here is a more versatile recording turntable, a recorder with variable cutting pitch, one that can be quickly adjusted for discs of varying thickness, a machine that will operate "faster" in busy control rooms. It's the new Presto 8 -C recorder with . INDEPENDENT OVERHEAD CUTTING MECHANISM: The cutting mechanism of the 8 -C is rigidly supported at one end by a heavy mounting post 21/4" in diameter. The other end is free of the table so that the alignment is independent of the disc thickness. A thumbscrew above the cutting head carriage adjusts the angle of the cutting needle while cutting for any direct playback or master disc from .030" to 1/4" in thickness. The cutting mechanism swings clear of the table for quick change of discs.

Fig. 1 -Right -hand and left -hand units of the photoelectric width gage

The amount of light falling on the phototube determines the amount of current flowing in the instrument car- rying the mirror on its rotor. The amplifier is so designed that an increase in light striking the phototube reduces the current in the instrument. Under this condition, the rotor of the VARIABLE CUTTING PITCH: The buttress thread feed screw is driven by instrument turns the mirror toward a belt and two step pulleys beneath the table giving accurate cutting the edge of the strip (counterclock- pitch adjustments of 96, 112, 120, 128 or 136 lines an inch. Changing wise for the left -hand instrument, fac- the cutting pitch is a matter of seconds. A hand crank and ratchet on the ing the direction of strip travel, Fig. 1/41 feed screw spirals starting and runout grooves up to apart. 2). By adjusting the sensitivity of Other specifications are identical with the well -known Presto 8 -N the amplifier, a condition is obtained recording turntable described in our complete catalog. Copy on request. where the galvanometer current ro- Cabinets are available for mounting single or dual turntable installa- tates the mirror to a position which tions. If you are planning to improve your recording facilities write allows just enough light to reach the today for price quotations and detailed specifications. phototube to cause the amplifier output current to balance the torque imposed by the hair -spring of the gal-

In Other Cities, Phone . .. ATLANTA, Jock 4372 BOSTON, Bel. 4510 vanometer. CHICAGO, Her. 4240 CLEVELAND, Me. 1565 DALLAS, 37093 DENVER, This condition of equilibrium can PRESTO Ch,4277 DETROIT, Univ. 1 -0180 KANSAS HOLLYWOOD, Hil. 9133 be produced any position RECORDING CORP. CITY, Vic. 4631 MINNEAPOLIS, Atlantic 4216 MONTREAL, Wel. 4218 at of the PHILADELPHIA, Penny.0542 ROCHESTER, Cul. 5548 SAN FRANCIS- edge within the limits of side register, ' 242 WEST 55th ST. N.Y. CO, Yu. 0231 SEATTLE, Sen.2560 WASHINGTON, D.C. , Shop. 4003 with different values of instrument World's Largest Manufacturers of Instantaneous Sound Recording Equipment and Discs current. In fact, stated conversely, different values of instrument current ft« January 1942 ELECTRONICS I llll;l101 l

PROGRESSIVE ENGINEERING characterizes the design of Colum- bia Broadcasting System's new 50 KW shortwave stations, WCBX and WCRC, at Brentwood, L. I., soon to be placed in operation. Facil- ities of the stations are planned for efficient shortwave transmission of programs to Latin America and Europe. Because of present -day conditions, improved reception in these parts of the world of programs from the United States is considered essential.

(Above) CONSTRUCTION DETAILS of the antennas are shown here. Horizontal wires at left near base of pole provide means for tuning the antennas through the medium of variable line shunts.

(Below) ISOLANTITE STRAIN INSULATORS are used also on lead -in wires from antennas to the building which houses the transmitting equipment built by Federal Telegraph Company. Transmitters can be quickly switched from one antenna to another, to maintain most efficient transmission at different times of day.

(Above) 13 DIRECTIONAL ANTENNAS are provided at the new stations, and several of them are of the four -section type shown here. Isolantite* strain insulators are extensively used in the construction of these antennas. These insulators find wide application in the radio and communications fields, because of their high mechanical strength (Below) SPECIAL FITTINGS used on Isolantite strain and and electrical efficiency. other types of Isolantite insulators at the new stations were designed and tested by engineers of Mackay Radio and Telegraph -: tit. Broadcasting System. These fittings *Registered !rode -name for the products 1 f' Company and the Columbia were manufactured by Burndy Engineering Company.

( «LIt ii L"

CI ÍC. it'it t. 1. iH t V flt ISOLANTITE INC. FACTORY: BELLEVILLE, NEW JERSEY SALES OFFICE: 233 BROADWAY, NEW YORK, N. Y.

ELECTRONICS - January 1942 69 NEW SHURE BROADCAST DYNAMIC represent different positions of the edge in space. As the edge moves transversely, the beam will follow the edge in order to maintain the light balance. Thus, because of an accurate relationship between beam position and instrument current, the amount of current is a measurement of the posi- SUPE *CAR D D tion of the edge of the material. How- ever, for measuring width, a right - hand detector is also required, to determine the position in space of the right -hand edge.

CUSP iNSTNUrENT 1

- -NINNOI

LENS -. Soutes

w-rIT ECTION LEES

-LINT SEAM

MEE /

.-- ELSiMONEs GECNEUE EON MoNCuMNENT I IN cuNNpTMIA Pc

irCOLLECTNt

¡ L[MS .,. -rNOTOEL[CTNIc TUEt MOIiT ÿc iqTIWM[MT

LMrLIIEN TO MOW- NANOANO Wide Angle Pick -up -yet LW_ Twice as Unidirectional Fig. 2- Diagram illustrating principle of as t h e C a r d i o i d operation of the photoelectric width gage

The currents of both left- and right - I hand detectors are totalized on one Single Moving -Coil Highly indicating instrument to measure the LW Immune to Mechanical Vibration and Wind Noises width. An increasing current in the totalizing instrument shows an increase in width; and a reduction in current shows a reduction in width. Hence, it \------Improved "Ultra" can be seen that a shifting in side reg- Model 5564 for 35 -50 LW Wide -Range Response ister with constant width of material ohms, Model 556B for from 40 to 10,000 cycles simply adds current to the detector 200 -250 ohms, and Model on one side and subtracts a like amount 556C high impedance . . - of current from the detector on the at only $75.00 list. 'Patented by Shure Brothers other side, with the net result of no change on the indicating instrument. Considering the principal optical axis of the lens system which projects the beam across the edge of the web as Now Available for Immediate Delivery the correct side -register position, an accuracy of plus or minus a inch can The newest, most advanced pick -up of reverberation energy be expected within a zone of I inch microphone available today for and random noise 73 %. Im- shift in side register from this point Broadcast service. The - proved frequency response as- "Super or z inch change in total width dimen- Cardioid" pattern first develop- sures full reproduction of music, sion. For a change in side register up ed by Shure Engineers, together crisp reproduction of speech. to I inch either side of the principal with the patented Shure Uni- The axial polar pattern is sym- optical axis, an accuracy of plus or phase* single -unit construction metrical at all frequencies. It's minus inch can be expected. This makes the big difference. It has the ideal answer for studio and accuracy would also apply to a net the most unidirectional pattern remote microphone problems. change in the 'width dimension of I in the limaçon family. It is twice in. These values are actual and become as unidirectional as the Cardi- Broadcast Engineers: You a decreasing percentage error as the oid, from the standpoint of re- can have the "Super -Cardioid" width of the material increases. ceiving front sounds and reject- for 30 -day free test in your sta- Material as narrow as 6 inches in ing rear sounds, yet has wide - tion without obligation. Write width can be measured and, by stagger- angle front pick -up. Decreases us today. ing the detector heads, it may be possible to reduce this value somewhat. SHURE BROTHERS, 225 W. Huron Street, Chicago, U. S. A. The web should be practically flutter - free at the point of measuring, but a "Aficrophone Headquarters" change in elevation of approximately 2 inches can be tolerated at the point where the web intercepts the beam of light. The plane of the web should be perpendicular to the light beams. 70 ELECTRONICS - January 1942 MAKING CONDENSERS DIRECT READING

AVARIABLE AIR CONDENSER with semi- cast -aluminum frame . . . worm shaft at right circular rotor and stator plates can be made angles to the panel ... have no immediate bear- to have remarkable linearity over about 80 per ing on the direct-reading problem. cent of a half turn. When used with calibration In the Type 722 -D the function of the drum curves or charts, the accuracy obtained is so high and dial are transposed. Twenty -five turns of that for many years manufacturers were dis- the worm produce a half turn of the rotor plates. couraged from attempting to make condensers The dial is divided into 250 divisions; the usable direct reading. portion of the condenser then has 5,000 divi- This phase of condenser development is now sions; one µµf covers 5 divisions on the 1,000 over. Most new condensers have direct -reading µµf condenser. scales calibrated to an accuracy as good as was The stator plate at the right of the stack is formerly obtained with calibration curves. used to make the capacitance per turn exactly The first step in making a condenser direct 50 µµf. Since only two stator supports are used, reading was taken with the now obsolete Type this plate can be tipped to correct for slight 222 (at left of illustration). The worm was cut irregularities in the main stack. As this plate with double threads giving 121/2 turns for 1/2 cannot be warped, a special stator plate, cut out turn of the rotor. The number of plates were in the middle, is used at the left end of the adjusted to make the capacitance increment per stack. This plate increases the capacitance per turn about 100 µµf. Ten turns (or 80 per cent turn at the ends. of the available motion) would then correspond Zero capacitance is altered by bending the to 1,000 µµf. flat plate which extends from the frame. By The scale markings were chosen to indicate means of these various adjustments the large capacitance taken out of the circuit. Adjusting section of this condenser is made direct reading plates were provided to make the capacitance in total capacitance to 414 or 0.1% between per turn exactly 100 µµf. Since the stator plates 100 µµf and 1,000 µµf. A small section is pro- were supported at three points, the stator adjust - vided also. This has one -tenth the capacitance ing plate could be warped to make up for irregu- of the larger. It is adjusted by similar means larities in the main stack. to be direct reading in total capacitance to 0.2 With this construction it was possible to adjust µµf or 0.1% between 25 and 100 µµf. the condenser so that it was direct reading in By appropriately shaping the rotor and stator capacitance difference from the zero mark with plates, these precision condensers can be use in a large number of direct - an accuracy of 1 µµf or 0.1%, whichever was adapted to greater. reading instruments. It is now possible to design The Type 722 Precision Condenser (at right a condenser which can be made to read directly of illustration) was developed as an improve- in almost any one of the many related quanti- ment on the Type 222. Most of the changes ties which the condenser may control in a circuit . . . ball bearings . . . integral -cut worm . . . or an instrument.

CAMBRIDGE GENERAL RADIO COMPANY MASSACHUSETTS ELECTRONICS - January 1942 71 pr, orwoiolltsALA&Ilij The speed of response of system the s s 410 is limited only by the damping of the is * I" ff electrical instruments, and is of the r order of sec. for a full -scale change r*, M. of indication. Care must be exercised to prevent excessive amounts of vibration from being transmitted to the equipment. By an excessive amount of vibration is meant a value sufficient to cause an appreciable movement of the galvanometer element on which the mirror is mounted, or to cause mechanical distortion of the optical system. The ambient conditions under which the equipment must operate deserve careful consideration. Any atmos- bf r. Lloyd Morris, Ass 't Directe- pheric contamination -such as dust, of Research at Galvin Mfg. C scale, lint, dripping water, smoke, or with 205A and 300A s steam -which is either opaque to light or which will cause dispersion, will affect any system responsive to the quantity of light transmitted through a space in which this contamination exists. This is not to be confused with the normal amount of air -borne substances that accumulate on lens surfaces and can be periodically cleaned off to maintain successful op- such eration. Exposure to radiant heat in Important manufacturers such an amount as to elevate the as these temperature of the equipment above 55 C. total temperature require special -hp- consideration for artificial means of DEPEND UPON cooling. INSTRUMENTS in testing for speed and accuracy time and money instruments that For Nail Detector New tests and measurements.measurementts. making p duction wave ana yzer 300A harmonic AUTOMOBILES ARE SHIPPED to South example, the model the indiv for you Africa crated in sturdy boxes built of makes with utmost speed of a complexcompplex wav heavy lumber. The quantities involved, components of Variable selectivity before the start of hostilities, were and accuracy. i stru Ant high frequency measurements. to- large enough and the scarcity of lum- the Galvin Mfg. Corp. Mr. William Hutter. facilitatesabove in service at audio ber in South Africa great enough to Chief Sound Enginee- shown 205A resistance tuned with the model a new justify the reclamation of the automo- of Rockola Mfg. Co. gether oscillators have set These new audio field ith -hp- 205AG oscillator. in both standard of operation h ndh the Mfg. shownor torye testing. The Rockola Company the Brush Development model 205AG and and other well model 200A. These uses the smaller service in the many firms have had excellent known they use -hp- instruments. important jobs for which THESE NEWER, FACTS ABOUT GET THE INSTRUMENTS BETTER LABORATORY be model aout the new o 1 mc. Ask response0 from 10 cps meterbwith frequency

HEWLETT Palo Alto, California 481 Page Mill Road The operation of the nail detector depends upon the motion of pieces of iron through a magnetic field

bile crate lumber for other purposes. One of the difficulties involved was that many large nails were used in the construction of these boxes. Naturally these had to be removed before any other use could be made of the lumber. Brush Development Co. oper- To locate the nails manually was both ator shown with mo r'e1200A slow and inefficient. An automatic method making use of the magnetic properties of the iron nails was indicated. Such a device was designed and 72 January 1942 - ELECTRONICS What's ahead for you Engineers?

Many ofyou who have chosen broadcasting as your life Now the pressure is on again. Resources of Bell Labs work were pretty young at the time of World War I. and Western Electric are developing many new things Let's look back -to see what's ahead. in radio to strengthen our land, sea and air forces. Under wartime pressure, radio research went for- When the present war is over, can you doubt that ward by leaps and bounds. Out of new ideas such as broadcasting will surge ahead as a result of today's those developed by Bell Labs and Western Electric intensified research? for military use came an entire new post -war industry - Look forward with confidence! Today's mobilization your industry of broadcasting. for war is also a mobilization for the peace to fol- Through peacetime years, Bell Labs and Western low. Count on Bell Labs and Western Electric to give Electric kept right on pioneering you new tools to help you make -helping your industry to grow broadcasting finer than ever in -with such major improvements Wester ectric the years ahead! as crystal control, stabilized feed- DISTRIBUTORS: In U. S. A.: Graybar Electric EQUI PPE D FOR Co., New York, N. Y. In Canada and Newfoundland: back, the Doherty circuit, verti- Northern Electric Co., Ltd. In other countries: cal radiators, directional arrays. BETTER BROADCASTING International Standard Electric Corporation.

ELECTRONICS - January 1942 73 constructed by Andrews & Perillo, Inc. of Long Island City, N. Y. The essential feature of the automatic nail detector is a magnetic circuit with an air gap through which the lumber is passed. If any iron is in the lumber, it will change the reluctance, and consequently the flux, of the magnetic circuit as it passes through the air gap. The changing flux induces a voltage in a pickup coil which is amplified sufficiently to operate an alarm or to mark the lumber at the location of the nail. Note that the operation of this system depends upon the motion of the iron through the airgap and not merely its presence in the gap. If the iron should be stationary, the alarm or marking device will not operate. There- fore this is fundamentally a high speed instrument and the normal speed of operation is about 100 feet of lumber per minute. The normal size of the air gap is 2 by 18 inches, but this can be smaller or larger depending on the size of the material to be tested. It is possible to make this opening as large as 6 by 36 inches to accommodate large pieces.

SOLDERING TERMINALS

ON PICKUP CARTRIDGES 35,000 -FT. JUMP FOR SCIENCE

3000 BUSY FINGERS Trained in Precision Workmanship

Because of the many exceedingly small and fragile parts required in the manufacturing of crystal microphones, pickups, cartridges and recording heads, much of this work must be done by hand. Astatic employees, long experienced in the assembling of these products, show amazing skill and accuracy in these operations. Constant supervision and testing provide an additional guarantee of accuracy. No Astatic Crystal Microphone, Pickup or other product ever leaves Astatic's shipping rooms before it has been tested and approved to meet the exacting Arthur H. Barnes, pilot and parachute jumper, gets a last minute check -up standards of performance for which it was intended. Care- from technical aides at a dress re- ful design, engineering and assembly assure the long and hearsal in Chicago where he later satisfactory service of Astatic Crystal Microphones, Pick- made a world record parachute jump of 35,000 feet. He is weighted ups, Cartridges and Recording Heads. Your Radio Parts down with various scientific instru- Jobber will be pleased to demonstrate their efficiency. ments from which he hopes to obtain records as to various conditions encountered by the body in this long jump. Mr. Barnes hoped to prove with the aid of scientists and engineers that properly protected from the elements and supplied with oxygen, there is no limit to the distance a body can fall without ill effects. Among the 113 THE ASIATIC CORPORATION pounds of instruments worn by Barnes \YOUNGSTOWN' In Canada: are a moving picture camera, a radio Licensed Under Brush OHIO Canadian Astatic Ltd. Development Co. Patents transmitter, an altimeter, and an oxygen . AD Toronto, Ontario b tank 74 ELECTRONICS - January 1942 Preferred in Peace, Demanded for Defense!. A7IA MAGNET WIRE

Controlling the brute strength of every tank are the tiny magnet wires in radio- communicating- systems, and other energizing and controlling mechanisms. To insure America's Defense, this wire must be the best that skill and modern methods can produce. When REA makes the wire for these and other requirements of Army, Navy, and the Air Forces, twenty-five years of experience and the most modern facilities in the industry combine to do the job ... to produce exactly what is wanted, to deliver it with greatest possible speed. If exacting specifications call for special wire, REA can "tailor- make" it to fit the job. REA wire ... with maximum uniformity, longer continuous lengths and superior spooling ... is helping to speed up Defense production. If you have a problem relating to wire - procurement, engineering or production -contact REA for quick action!

REA MAGNET WIRE COMPANY, INCORPORATED FORT WAYNE, INDIANA. U. S. A.

I S Y O U R S O N R E Q U E S T . I E D T A T A B L E A C O P Y O F T H E R E A W R A

75 ELECTRONICS - January 1942 IRVINGTON Program of the SCORES AGAIN Thirtieth NEW Anniversary FIBRONIZED KOROSEAL* TUBING Convention Institute of Radio Engineers

January 12, 13, and 14, 1942 Used by many large manufac- Hotel Commodore turers in electronics, instruments, aircraft, electrical appliances and New York, N. Y. power industries. FIBRONIZED KOROSEAL* TUBING'S MONDAY, JANUARY 12 outstanding properties include inside 10:30 A. M. -12:30 P. M. Opening Session and outside smoothness, exceptional Address of Welcome by elasticity, the Convention closer manufacturing toler- Committee Chairman, I. S. Coggeshall. ances. Will enable you to use it in intri- Message of the Retiring President, F. E. cate applications to improve the Terman. product and cut manufacturing costs. Remarks of the Incoming President, A. F. Van Dyck. FIBRONIZED "The Mobilization of Science with Special KOROSEAL* TUBING Reference to Communication", by Dr. F. B. FOR PERFECT PERFORMANCE Jewett. 2:30 P. M. -5:30 P. M. Technical Session Excellent resistance to acids, alkalies, "Half a Year in Commercial Television", by solvents Noran E. Kersta, National Broadcasting Company. Continuous heat resistance at 160° F. "Automatic Radio Relay Systems for Fre- Insulation resistance 90% R.H. 16 hours quencies Above 500 Mc", by J. Ernest at 105° F.- infinity Smith, RCA Communications. "Automatic Frequency Fireproof. Does not support and Phase Control combustion, of Synchronization in Television Receiv- Retains flexibilty after being subjected ers ". by K. R. Wendt and G. I. Fredendall, to 225 F. for approximately 1000 hours RCA Manufacturing Company (Demonstra- tion). (A.S.T.M. Test) "Simultaneous Aural and Panoramic Recep- Tensile strength -2,845 lbs. per sq. in. tion", by Marcel Wallace, Panoramic Dry dielectric strength (.022" wall thick- Radio Corporation (Demonstration). ness) -1050 VPM 8:30 P. M. -10:00 P. M. Technical Session "Color Television", by P. C. Goldmark, J. Wet dielectric strength (.022" N. wall thick- Dyer, E. R. Piore, and J. M. Hollywood, ness) -817 VPM after 24 hours immersion Columbia Broadcasting System (Demon- stration). 10:30 P. M. Inspection Meets or excels all A.S.T.M. specifications. Trip through printing plant of New York Daily News Comes in A.S.T.M. sizes and in a variety of colors. Is also available in transparent shade. TUESDAY, JANUARY 13

The Fibron Division of Irvington Varnish & 10:00 A. M. -12:30 P. M. Technical Session Insulator Co., leaders in the pioneering, "Preparation of Technical Papers for Pub- development and manufacture lication", by B. Dudley, Electronics, Mc- of extruded Graw-Hill Publishing Co. tubing for electrical insulation, invites you "The Use of Vacuum Tubes as Variable to test FIBRONIZED KOROSEAL* TUBING. Impedance Elements ", by H. J. Reich, Uni- versity of Illinois. Submit your specific problems to our "A Wide -Range, Linear, Unambiguous, Elec- Fibron Engineers, Department 106. They tronic Phasemeter", by J. E. Shepherd, will recommend the right tubing, furnish formerly Harvard University. samples and complete test data. "Variable-Frequency Bridge -Stabilized Oscil- lators ", by W. G. Shepherd and R. O. Wise, Bell Telephone Laboratories. *KOROSEAL -a trademarked name 2:30 P. M. -5:00 P. M. Technical Session of B. F. Goodrich Company "Space -Charge Relations in the Magnetron with Plane Electrodes", by E. V. Condon, Westinghouse Electric Manufacturing Com- pany, East Pittsburgh, Pa. "Bioelectric Research Apparatus", PLANTS AT by Harold IRVINGTON, Goldberg, Stromberg- Carlson Telephone NEW JERSEY, JL1 IRVINGTON, N. J. Manufacturing Company. U. S. A. HAMILTON, ONT.,CAN. "The Dynetric Balancing Machine", by H. P. Representatives in 20 Principal Cities Vore, Westinghouse Electric and Manu- liMMENIMIIIMMIMMIIIIIIP facturing Company. 76 January 1942 - ELECTRONICS PHOTRONIC

(SELF-GENERATING) PHOTO CELLS

...IN SHAPES, SIZES AND CHARACTERISTICS TO MEET YOUR SPECIFICATIONS EXACTLY!

Through the development of a new but thoroughly proved manufacturing technique, WESTON, who pioneered in the development of the stable, dry -disc photo-cell can now supply these cells in a wide variety of shapes and sizes including such specialties as multiple cell circuits on a M. IPA, common electrode. This new technique has overcome the many problems and the higher -.114 !!!! costs usually associated with specialty cell design. Furthermore, these cells can be furnished to exactly meet your specifications as to output, resistance, spectral response, etc., regardless of the quantities involved ... and all made to the rigid :`Photronic formulae which produces a cell of the highest output consistent with stability. For complete technical data on WESTON *Photronic Cells, or engineering cooperation, write to Photronic Division, Weston Electrical Instrument Corpora- tion, 618 Frelinghuysen Avenue, Newark, New Jersey. *PHOTRONIC -A registered trade- mark designating the photoelectric cells and photoelectric devices manufactured exclusively by the Weston Electrical Instrument Corporation.

Specialized Test Equipment ... Light DC Laboratory Standards . .. Precision and Measurement and Control Devices ... AC Portables ... Instrument Transformers Exposure Meters... Aircraft Instruments...... AC, and . . . Sensitive Relays DC, Electric Tachometers... Dial Thermometers. Thermo Switchboard and Panel Instruments. WE STON FOR OVER 5a YEARS LEADERS IN ELECTRICAL MEASURING INSTRUMENTS

ELECTRO MICS January 1942 Ionospheric Investigations at Huancays Magnetic Observatory (Peru) with Appli- CUSTOM -MADE APPLICATIONS cations to Wave- Transmission Conditions ", by H. W. Wells, Carnegie Institution of Washington.

WEDNESDAY, JANUARY 14

10:00 A. M. -12:30 P. M. College Session "Modern Techniques in Broadcasting" b Y J. V. L. Hogan, Interstate Broadcasting Co. "Modern Developments in Electronics" by B. J. Thompson, RCA Manufacturing Co. "Demonstration of Facsimile Equipment" by J. Hackenberg, Western Union Telegraph Co. 2:30 P. M. -5:00 P. M. Technical Session "The Fort Monmouth Laboratory of the Signal Corps ", by Major Rex Corput, United States Army. "Note on the Sources of Spurious Radia- tions in the Field of Two Strong Signals" by A. J. Ebel, WILL, University of Illinois 'RCA 10- Kilowatt Frequency -Modulated Transmitter ", by E. S. Winlund and C. S. Perry, RCA Manufacturing Company. 'A Stabilized Frequency- Modulation Sys- OF RESISTORS AND RHEOSTATS tern", by R. C. Pieracci, Collins Radio Company. 7:30 P. M.-10:00 P. M. Technical Session We Are Specialists of Over 'The Absolute Sensitivity of Radio Receiv- ers", by D. O. North, RCA Manufacturing 16 Years Experience Company. 'An Analysis of The Signal -to -Noise Ratio of Ultrahigh Frequency Receivers ", by Ingenuity of design, painstaking care in manufacturing and E. W. Herold, RCA Manufacturing Com- pany. sturdy construction have built our business to the point "A New Direct Crystal -Controlled Oscilla- tor for Ultra -Short Wave Frequencies ", by where more and more new customers call us in to discuss W. P. Mason and I. E. Fair, Bell Tele- phone Laboratories. their requirements, and to work out with them the most "An Ultrahigh Frequency Two -Course Radio Range with Sector Identification ", by efficient and economical means of handling their needs. Andrew Alford and A. G. Kandoian, In- ternational Telephone and Radio Labora- In addition to our regular stock of a full line of vitreous tories. enameled resistors and rheostats, we carry a large stock of RECRUITS LEARN component parts for immediate custom - made jobs for RADIO OPERATION unusual conditions of service.

May we consult with you on your next order?

At Fort Dix, N. J., new selectees who wish to become radio telephone or telegraph operators for service in field maneuvers or in directing artillery fire, HARDWICK, HINDLE Inc. take instruction under Lieut. Phillip Huston, Camden, N. J., and are assimi- Resistors Rheostats Radio Frequency Reactors lated on graduation into army units all over the country. Truck mounted equip- NEWARK, Power Line Chokes N. J., U. S. A. Line Voltage Reducers ment is shown in operation in this Custom -made resistance devices of all types photograph

78 January 19 -12 ELECTRONICS ióx a ured EMERSON PROVES THE VALUE

OF PARKER -KALON QUALITY -CONTROL

"DURING a busy week, we often use more than a million Parker -Kalon Self- tapping Screws ", says Emerson's* engineer. "We've tried others, but always found good reason to prefer Parker -Kalon ... they drive easier, with less torque and less wear on driver bits ... and our punishing `shake' tests show that they stay in tight!" The sure, trouble -free performance of a hundred or a million Parker -Kalon Self- tapping Screws is the result of rigid laboratory control of quality. Every safeguard is taken to protect you against "doubtful screws" ... screws that look all right but some of which fail to work right. Parker -Kalon Quality -Controlled Self- tapping Screws put an end to "slow -ups" ... you can start every P -K Screw quickly and easily, and count on it to hold! Trouble -free performance boosts the time -and -labor savings obtainable with Self -tapping Screws. "Doubtful Screws" rob you of part of the benefits you get by eliminating tapping ... or fumbling with bolts and nuts . . or riveting in hard -to- get -at places ... or inserts in plastics. No matter what material you're assembling - sheet metal, heavy steel, die cast metal or plastics - there's a type of Parker -Kalon Self- tapping Screw - thread -cutting and thread -forming - that will save time and money on the job. Parker - Kalon Corp., 192 -194 Varick Street, New York. * Emerson Radio a Phonograph Corp.

PARKER-KALON P -K QUALITY- CONTROL ELIMINATES "DOUBTFUL SCREWS" This Parker-Kalon Quality -Control Laboratory is without counterpart in the screw industry. Through unequalled testing SRF'TAPPIN6 SCREWS and analytical facilities it exerts rigid control over the quality of every screw produced. Not one detail is overlooked. Parker - Kalon Quality -Control is your complete assurance that every P -K Screw you use - the first or the millionth - is as good as modern science and manufacturing methods can make it. Give the Green light to Defense Assemblies SOLD ONLY THROUGH RECOGNIZED DISTRIBUTORS

ELECTRONICS - January 1942 79 Originally, the radio frequencies used were entirely in the 2 to 4 Mc band. THE ELECTRON ART For the last seven or eight years frequencies in the 30 to 40 Mc band have Forest service radio, analysis of high found increasing favor. This portion of the spectrum represents the best speed actions, an inductively coupled fre- compromise between the desirable characteristics of the ultrahigh frequency quency modulator, wave analysis with such as minimum static, short antennas, circuit efficiencies, and the better the cathode -ray oscilloscope, and the coverage below line of sight obtainable alert receiver are discussed in this with lower frequencies. Radio equipment requirements de- month's review of technical literature velopment, procurement, and maintenance, are briefly discussed. The high frequency and ultrahigh frequency U. S. Forest Service of use: administrative circuits, such as radiophones used by the Service are Communication Facilities between the forest supervisor and dis- also described in some detail. trict ranger officers; fire detection cir- ABOUT 208,000,000 acres of land are cuits, as between fire lookouts and look- under intensive protection against for- out to central fire dispatcher; and fire est fires by the U. S. Forest Service. suppression circuits, as dispatcher to pa- Analyzing High -Speed Action This gigantic task is greatly aided by trolmen, fire crews and fire trucks, con- THE PRINCIPAL METHODS for studying various communications facilities. The tact with foot and aerial scouts, freight- November 1941 issue phenomena too fast for unaided visual of Electrical En- ing planes, communication along the observation gineering carries a report called "The are described in the fire line, base camp contact, with re- October 1941 issue of General Communication Facilities of the U. S. Electric gional equipment depots, and communi- Review. The article is called Forest Service" by A. G. Simson which "Aids cation with the mobile fireweather for - for Analyzing High -Speed Action ", by gives some idea of how the Service cast units. uses communications equipment as E. M. Watson. an Some idea of the organization of the High speed action may be observed effective weapon against forest fires. service for emergencies may be gleaned The backbone of the national by direct visual observation, by means forest from Fig. 1. This shows a radio "net" of still cameras, and by motion picture communication is wire line, either For- which is used on "conflagration" fires, est Service lines or commercial cameras. In each of these methods a cir- which are usually from 50,000 to 75,000 shutter or a stroboscope of some sort cuits. Radio is used where no other acres in extent. The main communica- satisfactory means of communication is used. The shutter method is used tion center will be at staff headquarters where subjects radiate light of them- are available. Nearly all of the radio in the main base camp. From this communication is of an selves, or reflect utility light not used emergency na- point communications service will be to determine exposure time. Exposure ture. It is not considered desirable to established with the regional equip- have both routine administrative time is determined by the shutter. The and ment depot, forest supervisor's head- stroboscopic method is used where fire traffic flow over the same radio quarters, reconnaissance and transport circuits. In time of emergency other light does not materially inter- the ad- planes, fire weather units, and the sec- fere with stroboscopic light. Here the ministrative traffic would have to give tor camps located along the fire line. way to emergency needs which exposure time is determined by the would The sector camps will set up local net- stroboscopic flash. disrupt the normal forest administra- works to communicate with the fire tion. Each method is treated in detail, and line, ground scouts, nearby lookouts, is illustrated with pictures taken by The communication system on a for- and various fire fighting units within est unit falls into three general the means described. Though much classes the sector. literature has been published on the various devices used in this field, no attempt seems to have been made to classify or relate the methods em- Fire Base weather- frequency-m ployed. Engineers will find this article camp -- -- - interesting because it gives a "bird's Additional Frequencies eye view" of the entire subject. on LUitra_bigh frequency "' _ = Forest (regency. III

Equipment Sector Scout and Fire depot camps transport weather Inductively Coupled plane ruck Frequency Modulator Forest frequency fire frequency AN INTERESTING FREQUENCY MODULATOR is described in the October 1941 issue of the Proceedings of the I. R. E. by Sector Packer Bruce E. Montgomery. This device bosses Scouts and spike LooBout camps ,aton allows the engineer to design a frequency modulated oscillator that has more power output and one which will operate on a higher fundamental frequency than conventional modulators in use at present. Control Emergency The fundamental idea of the modu- line lookouts lator is very simple. An inductance, capacitance, and resistance in parallel are inductively coupled to the frequency- controlling circuit of the self- Fig. 1- -Block diagram of the radio net used by the U. S. Forest Service excited oscillator. When the resistance in fighting a forest fire of the "conflagration" class -one whose area is varied, corresponding changes in re- is 50,000 or 75,000 acres and whose perimeter is about 100 to 150 miles actance and resistance are reflected 80 January 1942 - ELECTRONICS SOLVING TEST, RESEARCH and SERVICE PROBLEMS on a Thousand Fronts So general is the use of RCA Electronic Test Equipment in such a wide variety of work that _t would be nearly impossible to name an industry and say "there is no need for RCA Test Equipment here ". This equipment creates its own need -not only by proving its ability to do old jobs better, more accurately than they have ever been done before, but, equally important, by opening new horizons in engineering, testing and servicing on a vast front. Today, of course, practically all RCA Electronic Test Equipment is being supplied for Defense needs. Tomorrow's users, however, will benefit, not only tl-_rough RCA's increased Write for catalog sheets facilities for production, but even more so through the far - on equipment in which reaching experience gained in the application of this equip- you are interested. ment along almost unlimited lines.

o RCA MANUFACTURING CO., INC., CAMDEN, N. J. A SERVICE OF THE RADIO CORPORATION OF AMER CA LIMITED, MONTREAL IN CANADA : RCA VICTOR COMPANY,

ELECTRONICS - January 1942 81 into the oscillator inductance thereby causing frequency variations. In the circuit used, the parallel resistance is the plate circuit of a 6F6 tube. DECADE AMPLIFIER The circuit of the frequency modulator coupled to the oscillator is shown I%w MODEL 220 in Fig. 1. Variations in the a -c plate resistance of the 6F6 tube are ac- centuated by the proper placement of a resistor in the plate circuit. The performance of this circuit is shown in Fig. 2. As the grid voltage is varied there is a marked variation in frequency. The circuit constants of the

MODEL 300 ELECTRONIC Fig. Circuit VOLTMETER 1- diagram of the frequency modulator inductively coupled to a self- excited oscillator operating at 2.5 Mc

MODEL 220 2,465 DECADE AMPLIFIER

2,460

2455 2.0 u NEW ACCESSORY FOR MODEL 300 VOLTMETER 2,450

FOR MEASUREMENT OF VERY LOW A -C VOLTAGES 2,445

2,440 0.5 Decade Amplifier: This is a highly stable amplifier giving accurately 2,4350 standardized gains of lox or 100x over a fre- -10 -15 -20 -250 quency range of 10 to 100,000 cycles. Operated by self -con- E9-Volts tained batteries having a life of over 150 hours. Used with Fig. 2- Variation of oscillator fre- our Model 300 Electronic Voltmeter (as shown in cut) quency and oscillator grid current A -C voltages down to 0.00003 volt (30 microvolts) can be of the circuit shown in Fig. 1 as the modulating grid voltage is varied measured. By means of special circuits the gain is independent within 2% of circuit constants, battery voltages and modulator were chosen for a frequency tubes. Fully described in Bulletin 7. of 2.5 Mc. However, the total variation in frequency could not be used for modulation because this would bring Electronic Voltmeter: A popular instrument for the the highly curved portions of the char- measurement of A -C voltages, 10 to 150,000 cycles, 1 milli- acteristic into use, and excessive distortion would result. The curve volt to 100 volts 1000 10,000 shows (up to and volts with Model that about a l'7-kc variation would be 402 Multipliers). Logarithmic voltage scale and auxiliary available for modulation purposes. This uniform decibel scale. A -C operated. By means of special would give a deviation of plus or minus circuits indications 175 kc at 50 Mc and is considerably are independent of line -voltage, tubes more than can be used in practice. and circuit constants within 3% over entire frequency range. The variation of oscillator grid cur- Several accessories, such as an artificial ear, vibration pickup rent with changing grid voltage is and multipliers also shown. This variation in grid are available. Fully described in Bulletin 6. current is caused by the resistance being coupled into the oscillating cir- MADE BY cuit by the modulator. As this coupled resistance increases, it decreases the amplitude of the oscillations, and thus Ballantine decreases the rectified oscillator grid Laljortilorjes, nc. current. This effect produces amplitude modulation on the frequency - BOONTON, NEW JERSEY modulated output. However, the limit- ELECTRICAL AND ACOUSTICAL INSTRUMENTS ing action of the following frequency multiplier stages will remove this am- 82 January 1942 - ELECTRONICS Defense Saving Pay -Roll Allotment Plan

How big does a company have to be? From three employees on up. Size has nothing to do with it. It works equally well in stores, schools, publishing houses, factories, or banks. This whole idea of pay -roll allotment has been evolved Department. voluntary orkers provide for the future by businessmen in cooperation with the Treasury helps Each organization adopts its own simple, efficient application pay -roll of the idea in accordance with the needs of its own set-up build future buying power helps No chore at all. The system is so simple that A. T. & T. allotment uses exactly the same easy card system that is being used by hundreds having fewer than 25 employees! It is defend America today of companies plan helps simple enough to be handled by a check -mark on a card each pay day. This is no charity plea. It is a sound business proposition that Although this is vitally concerns the present and future welfare of your company, Plenty of help available. your plan when put it into effect, the Treasury Department is ready your employees, and yourself. you and willing to give you all kinds of help. Local civilian com- -war period of readjustment, you may be faced During the post mittees in 48 States are set up to have experienced men work necessity of turning employees out into a with the unpleasant with you just as much as you want them to, and no more. world. But you, as an employer, can do confused and cheerless Truly, about all you have to do is to indicate your willingness to help shape the destinies of your people. something now to get your organization started. We will supply most of the have adopted the Voluntary Pay -roll Scores of business heads necessary material, and no end of help. Allotment Plan as a simple and easy way for every worker in the land to start a systematic and continuous Defense Bond The first step is to take a closer look. Sending in savings program. the coupon in no way obligates you to install the Plan. It will simply give you a chance to scrutinize the available material and It is Many benefits ... present and future. see what other companies are already doing. It will bring you step toward reducing the ranks of the snore than a sensible samples of literature explaining the benefits to employees and It will help spread financial participation in post -war needy. describing the various denominations of Defense Savings Bonds National Defense among all of America's wage earners. that can be purchased through the Plan. The widespread use of this plan will materially retard infla- tion. It will "store" part of our pyramiding national income Sending the coupon does nothing more than signify that you that would otherwise be spent as fast as it's earned, increasing are anxious to do something to help keep your people off relief the demand for our diminishing supply of consumer goods. when defense production sloughs off; something to enable all wage earners to participate in financing Defense; something to overlook the immediate benefit money for And don't ... e,- provide tomorrow's buying power for your prod- defense materials, quickly, continuously, willingly. ucts; something to get money right now for guns Let's do it the American way! America's talent for and tanks and planes and ships. working out emergency problems, democratically, is being France left it to "hit -or -miss" ... and missed. tested today. As always, we will work it out, without pressure Now is the time for you to act! Mail the coupon or coercion ... in that old American way; each businessman or write Treasury Department, Section A, 709 strengthening his own house; not waiting for his neighbor to do Twelfth St. NW., Washington, D. C. it. That custom has, throughout history, enabled America to get things done of its own free will. In emergencies, America doesn't do things FREE - NO OR"LI t We would get there eventually if we "hit -or- miss." rTreasury Department, Section A, just left it to everybody's whim to buy Defense Bonds when they 709 Twelfth St. NW., Washington, D. C. thought of it. But we're a nation of businessmen who understand that the way to get a thing done is to systematize the oper- Please send me the free kit of material being used by ation. That is why so many employers are getting back of this companies that have installed the Voluntary Defense Savings Pay -Roll Allotment Plan. Voluntary Savings Plan. Like most efficient systems, it is amazingly simple. All you Name have to do is offer your employees the convenience of having a fixed sum allotted, from each pay envelope, to the purchase of Position Defense Bonds. The employer holds these funds in a separate bank account, and delivers a Bond to the employee each time Company his allotments accumulate to a sufficient amount. Each employee who chooses to start this savings plan decides Address for himself the denomination of the Bonds to be purchased and the amount to be allotted from his wages each pay day. This space contributed by ELECTRONICS ELECTRONICS - January 1942 83 plitude modulation and leave frequency modulation only at the output frequency. The author points out that though the frequency modulator he describes was designed for 2.5 Mc only, there appears to be no serious limitations to its use on much higher frequencies. The circuit shown in Fig. 1 is capable of delivering more power than can be secured from a reactance tube frequency modulator which normally uses receiving -type tubes. The use of even larger oscillator and modulator tubes in this inductively -coupled system would allow much more power to be delivered to succeeding frequency-multiplying stages. The combination of IN AUTOMAT/C ELECTRIC RELAYS/ higher- frequency operation and in- Automatic creased power output would allow the Electric relays are life that mean genuine economy. design of more compact and economi- world- famous for quality. Tested The complete Automatic Electric cal transmitting equipment by elimin- by time through years of exacting relay line includes units for every ating frequency multiplying stages. use . . . constantly improved by operating condition. All are char- endless laboratory tests ... backed acterized by positive action and de- by the "know how" gained from 50 pendability -for which you pay no years of specialized manufacturing premium. experience -these relays give you Send for your free copy of our Wave Analysis by the superior performance and long comprehensive relay catalog. Cathode -ray Oscilloscope

AMERICAN AUTOMATIC ELECTRIC SALES COMPANY COMPLEX PERIODIC FUNCTIONS, when transformed into corresponding voltage 1033 W. Van Buren Street, Chicago waves, may be analyzed with the use of the cathode -ray oscilloscope. How AUTOMATIC 7 this may be done is explained in an R E L A Y M A K E R S S I N C E 18 9 8 article called "A Cathode -Ray Method of Wave Analysis" by Vincent O. John- son which appears in the December 1941 issue of Electrical Engineering. If the complex voltage wave is impressed across the horizontal plates of SLIGHT a cathode -ray tube, and a pure sinusoidal voltage across the vertical plates, and if the frequency of the latter volt- BLADE age bears an integral relation to the fundamental frequency of the complex wave. a Lissajous figure appears on FLEXURE the screen. The area of this figure is directly related to the coefficients of the MEANS Fourier series of the wave. The complex wave may be represented by f(B) where

f (B) = Ao +AI sin B +Bt cos 0 + A2 sin 20 + B2 cos 20 + ...A. sin n0 +B. cos n0 +.. (1) The sinusoidal wave which is impressed across the vertical plates is repre- TO sented by g(9), where g(B) = -K cos k (B + ak) (2) The function g(0) has a frequency k 541CAAC-r S!Y/iCH times the frequency of the fundamental k The unique design of the ACROSNAP SWITCH with its rolling spring of f(0). If is an integer to snap a Lissajous the blade from one position to the other permits actuation with a very slight then figure will appear on flexure of the blade. the screen. The amplitude of g(9) Available with all ordi- is K, and the angle ak is the phase nary types of actuation - Since metal fatigue is governed by the relation angle between g(0) and the cosine leaf, spring plunger, of the etc. unit stress to the elastic limit of the material it follows term of the kth harmonic of f (B). that this minimum flexure means exceptional long life for ACROSNAP SWITCHES. The area of the Lissajous figure Sk calculated from the two expressions is: Write for complete information advising purposes for Sk = (Ak cos kak Bk sin kak) which switches are required. kKr + (3) Now if the phase angle ak were al- The Switch lowed to change to a new value, say ßk, with an the area of the figure would change to Engineered ACRO ELECTRIC CO. a new value S'k. This area can be ex- Principle 3145 Fulton Rd. Cleveland. Ohio pressed similarly as i k (Ak S'k = Ífa cos kßk + Bk sin kßk) (4) 81 January 1942 - ELECTRONICS Combining these last two equations together we get: JONES Sk sin kßk Sk' sin kak A= - (5) BARRIER STRIPS kKr sin k (ßk - «k) CAL THE INSULATORIEI) SOLVE MOST TERMINAL Sk' cos kak Sk cos kßk BL - (6) PROBLEMS kKr sin k (ßk - ak) The constant term A. in Eq. (1) is relatively unimportant, and may readily be determined by means of a d-c meas- an ours cin uring instrument. The procedure is relatively simple. the NEW PLANT of The frequency of the oscillator must coincide with the frequency of the com- Mycalex Corporation of America plex wave. When the frequencies are synchronized a Lissajous figure will appear on the screen of the cathode - ray oscilloscope. This figure is photo- EXCLUSIVE graphed. Then the phase angle between the two waves is varied and an- A compact, sturdy terminal strip with other photograph is taken. A calibra- AMERICAN Bakelite Barriers that provide maxi- tion picture is taken also. This figure mum metal to metal spacing and pre- is produced when two sine waves of a vent direct shorts from frayed wires impressed LICENSEES at terminals. known phase difference are on the horizontal and vertical plates 6 SIZES respectively. The distance of the peak cover every requirement. From 3/4" from the vertical axis is proportional under all British patents* wide and 13/32" high with 5-40 screws to the phase difference angle. By re- to 21/2" wide and I /8" high with ferring to this calibration figure kak MYCALEX -the low -loss electrical insulat- lit"-28 screws. ing material made of a combination of and kßk are determined. The areas of electrical glass Jones Barrier Strips will improve as the Lissajous figures are determined finest quality mica and - well as simplify your electrical intra- now comes to you from our new, large connecting problems. Write today for by a planimeter. plant in Clifton, New Jersey. Finest equip- catalog and prices. ment and capable staff, supervised by skilled engineers, assures careful, prompt machining of this superior dielectric to HOWARD B. JONES your most exacting needs. Send us your blueprints. Let us quote on machined 2300 WABANSIA AVENUE, Mycalex, or on Mycalex sheets and rods. CHICAGO ILLINOIS FREE BOOKLET: Send today for 12 -page illustrated booklet with full descriptions of Mycalex uses.

CAN MYCALEX BE MACHINED TO CLOSE TOLERANCES? T Mycalex can be cut, drilled, tap- ped, machined, milled, ground eó and polished to close limits. Does not warp under heat due to its very low thermal coefficient of expansion. Impervious to water, oil and gas. And its great mechanical strength is outstanding among insulators.

Into Lingo designing has gone the finest engineering skill and modern antenna en- Plotting the Lissajous figure for the gineering. The re- fundamental sine component of f(1 )) sult- "plus" perform- at the positive peak ance combined with with t?o low installation and maintenance costs. Now if the scales for all the figures s<.i are the same Ak and Bk can be calculated from Eqs. (5) and (6) in inches. 199 ft. (above roof) Each area may be converted by means Radiator at WIBM, a Jackson, Mich. An- of its scale constant to hypothetical other example of unit such as square volts or square am- Lingo versatility to peres. Then K, the assumed constant meet every station need. can be converted to the correct units, and the value of Ak is derived in those units. If K is not constant, Eqs. (5) and (6) must be altered as follows: Examples of Machined .ityeal,,t (Sk/ K) sin kßk- (Sk / K') sin kak Ak kir sin k (ßk - ak) (7) Mycalex Corporation of America Sales Headquarters: Factory: (Sk 1K1K') sin kak- (Sk/ K) cos kßk 7 East 42nd St., 60 Clifton Blvd., Bk (8) N. Y. Clifton, N. J. kir sin k (ßk - ak) New York, Mycalex is welt -known and highly -regarded by the The scale constant may be deter- world's leading engineers in the fields of radio, telephony, railroading, mining, electric signs, elevators, X -ray equip- RADIATORS mined by taking a picture of a pure ment, aviation and others. JOHN E LINGO & SON INC CAMDEN N. J. sine wave of known amplitude at the ELECTRONICS - January 1942 85 same time the other pictures are being taken. To vary the phase difference angle the frequency of the sine -wave generator is made slightly higher than that of the harmonic. The figure is stopped by synchronizing the two waves. If the peak of the figure is stopped before it pl reaches a point midway between the upper right hand corner and the midpoint of the screen the angle will be CERAMIC between 0 and 90 degrees. If it is stopped between the midpoint and the upper left hand corner, the angle will be between 90 and 180 degrees. It is RESISTORS good practice to make kak about 45 degrees, and kßr about 135 degrees. Deri- vations, further discussion of procedure, and experimental results are also Finding the right resistor covered. for a specific application is A Precision Crystal likely to be no easy problem. Secondary Because the solution so often is found in Globar Brand FREQUENCY STANDARD Ceramic Resistors we urge Receiver Control by THAT HAS SEEN you to acquaint yourself with "Designed for Application" the distinctive qualities of Transmitted Signal A preoleton frequency standard capable of these versatile resistors. being adjusted to WWV or some other The handy chart below shows A NEW SERVICE IN BROADCASTING is de- primary standard and putting out uniformly accurate calibrating signals with le. 21, lee, types available, together with scribed in the October 1941 issue of 1000 KC intervals. Uses the new GENERAL their characteristics. ELECTRIC No. l3A 1000 KC crystal having the RCA Review. The author, Harmon a frequency temperature coefficient of less B. Deal, in an article called "Receiver than one cycle /Mc /C'. The crystal is sealed in Helium in a standard metal tube envelope. TYPE A I CX Control by Transmitted Signal -`Alert' The self -contained AC power supply has Receiver," VR110 -30 voltage regulator tube. DIAMETER tells how a broadcasting In addition to oscillator. multivibratere, MIN. 1/16" 1/16" 1/16" station may turn on all receivers and harmonic amplifier. a built -in mixer MAX. 1" 1" 1" with phone jack and gain control en panel within range which are equipped with Is incorporated. LENGTH an attachment receiving device, and MIN. 14" 1/4" 1/4" then, at the end of an announcement, MAX. le" IS" 16" turn them off. The plan is feasible on WATT the sound broadcast band or the ultra- RATING' high frequency band. MIN. 1 /4w. 1 /4w. 1/4w. MAX. 14w. 34w. 150w. Use of the facility would be limited

RESISTANCE to important news flashes because per in. of abuse of this privilege would soon re- length sult in a loss of listeners who would WITHOUT MIN. 25 ohms S ohms 1 ohm the device. The cost of such MAX. 15 mag. 15 meg. 1000 disconnect -deedless Blows ohms equipment at the transmitting end is NORMAL negligible since the equipment re- Unusual efficiency is obtained in this small RATING quired is merely a receiving -tube oscil- fuse with o high time log. p fing need- w. sq. in. of lator. The cost of the receiving attach- less blows. and fuse expense radiating 1 1 2 -1/2 ,.'f___ ment is estimated at about ten to twenty dollars, even in small quantities. A block diagram of the system is By artificial cooling these ratings may be increased substantially. shown in Fig. 1. The transmitter LITTE LFIJSES Characteristic coefficient: sends out a 36 -cps modulating fre- t...,, A {usE un. Typ At Commercial straight line quency to turn on the "alert receiver ". are especially designed Voltage and Temperature This is picked up by the receiver, and to protect small motors, Typ It Negative Voltage magnets, solenoids, and Negative Temperature causes certain work circuits to turn on RES, STOP TO ioaalSN other equipment Typ at commercial straight line the receiver. When the announcement IbNEATItlA havirg Voltage and Temperature is completed a 24 -cps carrier modulat- SPRING high inductive and ca- Twwlaalsa All types: Sdetalired ends pacitative Also with or without wire lead. surges. On overloads "A" the dependable fuse for separates In 3111 "B" On short circuits "A" melts. Spring action intermittent duty circuits, prevents rryntalllu In addition to these standard Lion o repeated vibrators, control circuits, heating rL ii cooling items, special resistors can be etc., where f r e q u e n t made to meet definite specifi- cycles would soon crystal- cations both as to shape and lize or break a simple fuse element. Slo -Blo characteristics. Ask for Bul- blows but holds awhile. letin R and give us details of your requirements. FUSE MOUNTINGS Globar Division Littlefuse covers the field in fuse mountings for small applications and instruments as well THE CARBORUNDUM CO. as heavy duty. Many types are standard and stocked. Special types de- NIAGARA FALLS, N. Y. signed. Write for catalog.

Carborundum and (:lobar are No. 1056. For 3 AG fuses. trade -mark s of and indic:,[, manufactura by The Carborundum C pang. Panel type mounting black

bakelite base. I S/gal /2:

Fig. 1 Block diagram of the trans- LITTELF1111E INC. d mitter- controlled receiving system 4755 RAVENSWOOD AVE. CHICAGO. ILL. 86 January 1942 - ELECTRONICS ing frequency is transmitted, and this causes the work circuits to turn off the receiver. The circuit of the control is shown in Fig. 2. The work circuits are tuned -reed relays. The low frequencies are used because they can be used at the same time that ordinary broadcast frequencies are used without interference. To insure absence of interference, a low pass filter is incorporated in the circuit which cuts out all frequencies above 45 cps. As is shown in the block diagram, the control unit can be used to light a warning light or ring a warning bell just before the announcement. The power consumption of the device in Fig. 2 is 28 watts from the 110 -volt power supply. It is pointed out that since the original model was built, several smaller multi- purpose tubes which are now available TRANSMITTER- RECEIVER for 2v METERS can decrease the size and power re- for either fixed station or mobile quirements of the control unit. A compact, efficient unit, designed operation. Transmitter and receiver sections are completely separated. The 5 inch PM speaker is self-contained. Single interconnected switch permits use of a common antenna for both transmitter and receiver. The TR -4 requires a 6 volt battery or 110 volt, 60 cycle AC power supply. Receiver radiation is necessarily reduced to a minimum.

FREQUENCY: 112 to 116 MC. RANGE: Varying from 5 to 75 miles, depending upon terrain. Contacts up to 150 miles have been completed in field tests. TUBES USED. One each of Hytron HY -615, Hytron HY -75, 7F7, 6V6 or 6L6. MICROPHONE: Any good single button microphone.

MOD TR Overall size 9" x 8" x -4 less tubes and power supply, list price $6511°

LF. Avc Low pass Volume 8 WEST 18 STREETNEW YORK, N. Y fitter control cut -of l r --Y-_ -- 45 Cps. 2m 0.05 \ 2nd 1 Ìdetector To alert receiver power supply CONSTANT VOLTAGE demands of 2meg is the answer to the precision and INDUSTRY for DEFENSE í00,00o SCIENCE L j 'G meg 15 v. power line 5 mfd Audio

Every COMMUNICATIONS system every I - -- Double acting, locking relay LA-C Outlet for controlled set, bell, light, etc electrical INSTRUMENT employed in the production of materials of war needs VOLTAGE protection against Fig. Simplified circuit diagram CONSTANT 2- line surges and fluctuating voltage levels of the alert receiver caused by overloaded power lines. Sola CONSTANT VOLTAGE TRANSFORMERS A model built for operation on broad- will deliver a perfectly stabilized output cast band was given laboratory tests, voltage, even though line voltages vary as much as 30%. No moving parts. Instan- and then modified for operation in the against in the field taneous in action. Self- protecting 50 -Mc band. It was tested overload or short circuit. for several months, with the receiving unit located at various places from 1 Ask for Bulletin DCV -74 to 45 miles from the transmitter. Re- sults were satisfactory in every case. SOLA ELECTRIC COMPANY The author believes that this method provides a useful and appealing possibility for facilitating communication of vital news to Civilian Defense or- TP.Af1SF0RPtEP.S ganizations. He also discusses further design considerations of the receiver unit, control- frequency, source, and ILL. the selective unit (the tuned -reed 2525 CLYBOURN AVE., CHICAGO, system) . ELECTRONICS - January 1942 87 Rhodium Contacts NOIN MORE THAN EVER c 4L1a PRECIOUS METALS, which are compari- ATTENTION COUNTS tively inert chemically, have long been used for various types of contacts in electrical switching equipment. A For Extra Quality newcomer to the family of contact materials is rhodium whose physical properties are shown in the table. E. H. BRYANT Electric Laister discusses the use of this metal as a non -corroding contact surface in "Rhodium Contacts ", an article USES appear- WILCO ing in the November 1941 Electronic Engineering. The design of flexible and easily ELECTB ¡CAL handled equipment usually involves a great deal of switching. Many of these switches carry only small r -f and a -f CONTACTS currents with no d -c potential difference across them to assist in breaking down Bryant Electric wanted to make the world's best flatiron any oxide or tarnish film that may form plug. To provide the absolute maximum degree of during idle periods. Since any changes dependable operation and trouble -free service, this in the current passing through the quality minded company decided on Wilco silver faced closed contacts is usually amplified base metal for the finger- contacts of this deluxe plug. many thousands of times by the following amplifiers any unstable contact will As a substitute for copper in certain industrial appli- result in the output cations, being unreliable, investigate Wilco silver clad steel. A permanent noisy, and possibly failing completely. bond of fine silver and steel, this material has an elec- Where r -f currents only are to be trical conductivity car- approximately equal to 70-30 bronze ried it is standard practice to use combines some the corrosion resistance of pure silver with contact material which is stable in it- the stiffness of steel. Write for new descriptive folder. self. This is usually some form of precious metal, gold -silver and gold- silver- platinum alloys being the most popular. The H. A.WILSON CO. Physical Properties of Rhodium 105 CHESTNUT ST., NEWARK, N. J. Branches. Chicago and Detroit Atomic Weight 102.91 Specific Gravity 12.44 Specific Resistance 4.90 x 10' ohms per cm cube Melting Point 1907° C Coefficient of Linear Expansion 8.5 x 10-" Color Silvery -white

Where absolute reliability under adverse conditions is required, rhodium, one of the platinum group metals, is finding GENERAL CABINET RACKS wide and successful application. It is hard, actually file-resistant, and Featuring Beauty, Durability and Economy, has remarkable wearing properties. It these Streamline Cabinet Racks afford the is more chemically inert than platinum, BEST in enclosures for an endless variety being completely unattacked at ordi- of industrial electronic installations. The nary temperatures five cabinets made in this series accom- even by boiling modate 19" rack panels in heights from aqua regia. Oxidation in air does 8%" to 35 ". not take place below 600 to 800 degrees Centigrade. Though difficult to Callon our Sheet Metal Department for estimates on your special work, rhodium may be deposited elec- requirements. We make custom - trolytically with ease. It is quite ex- built cabinets, panels and punched pensive, 0.001 inch deposit costing chassis for many types of co,,, nercial applications. about $2.50 per square inch. This thickness is sufficient for r -f contact surfaces even under the most drastic conditions. It is possible to limit the deposit to quite small areas, and for anything over 0.001 -inch thickness, this is usu- BUD precision -built midget condensers are made in many ally done. It is common types and capacities for a variety of commercial requirements. practice to They feature Alsimag 196 insulation, positive wiping rotor plate an area of less than 1's square contact, electro- soldered rotor and stator assemblies, bright inch so that this expensive metal ap- cadmium plated finish, and rugged mechanical construction. pears only where it is needed. For We will be pleased to furnish estimates on your requirements. thicknesses less than 0.0002 -inch the best and closest grained deposits are obtained on silver which is used as a base metal or as a preliminary electro- $ITP BUD RADIO, INC. deposit on the surface to be plated. CLEVELAND, OHIO Above this thickness the metal is plated directly. 88 January 1942 - ELECTRONICS CAA's Part in Instrumentation EICOR THE CIVIL AERONAUTICS ADMINISTRA- do you TION has been outstanding in develop- "what ing new instruments to increase the f safety of aircraft. Some of the instru- re4require ment developments in which the CAA DY N played a large part are reviewed in an 2kt article entitled "The CAA and Indus- ?" try Cooperate to Develop Instrumen- Precision tation" by C. I. Stanton which appears in October 1941 issue of Instru- 4./xt Unbelievable accuracy, car- the ried into seemingly unim- ments. portant parts, makes it pos- An interesting development of the sible for Eicor Dynamotors CAA engineers was the dual automatic to pile up performance radio direction finder. The instrument records of five to ten times is actually two radio direction finders more operating life. interconnected, with their needles in- Such accuracy is accom- dicating on the same azimuth scale. plished by proper tooling- The needle of each receiver points to C0a)u the use of precision fixtures, the station to which it is tuned. When jigs, and gauges-with ade- a station ahead and one to the rear quate grinding and balanc- are tuned in, the pilot can fly along a ing equipment -and above straight line between the stations by all, keen -eyed inspection. In the right or left every Eicor Dynamotor, moving his plane to such important details are until the needles form a straight line. a part of the "specs." This device was first installed in the CAA's laboratory plane and is now commercially manufactured, and being installed by the airlines. The CAA also originated specifications for a new ultrahigh frequency radio receiver which the airlines are now purchasing for use on runs where the CAA has installed u -h -f radio ranges and landing systems. The re- IIgOR ceiver is equipped with push buttons 1941 has been one 33 fre- EICOR,Inc.,1050 W. Adams St.,Chicago, U. S. A. which can select separate of the best years in Halli- Export: Ad Auaemo. 89 Brood St.. Ne- York quencies between 110 and 132 Mc. It can receive u -h -f course signals of the crafters existence. We are CAA radio range stations and instru- grateful for the host of HEADQUARTERS ment landing localizers, as well as voice instructions from airport traffic new friends such receiv- FOR RELAYS control towers. ers as the SX -28 has made More than thirty years of concentrating for us. in the designing and manufacturing of signalling and control equipment by HUNT VIA AIR WAVES Autocall Company has won for its de- SPY As the year came to a vices and systems a decided preference. close, we were a little A broad line of production items, as well as special units to customer's own proud that we had been specifications, are available. able to fulfill the demand such equipment had en- joyed. 1942 will see us keeping up with our ever- increas- ing National Defense JACK TYPE REDJ -1 commitments and still Contacts positioned by momentary elec- supply radio communica- trical operation of coil and mechanically maintained by armature. One of tions equipment to our several Jack Type Relays in the Autocall line. old friends. Send for Free Catalog William E. Downey, supervisor of the The AUTOCALL Co. South Pacific Monitor Area, and Rob- Zls-../ly 39iew... SHELBY, OHIO ert Powell. operator, at the receiving ,r5ol ssesolowslowel equipment at Santa Ana, Calif., used ieh g9 a-umúes AUTOCALL COMPANY for radio monitoring. At the Santa Ana Shelby. Ohio obligation, lease station there are 15 radio engineers and Without your new send a on signalling, technicians working day and night No. it-2, catalog equipment. control devices and shifts for monitoring programs originat- .. ing in the United States or in foreign +he LaIicraLers co. Name countries. The Santa Ana station is CHICAGO, U. S. A. Address ,.,,,.State...... , . . one of the eleven primary national de- City stst111l fense monitoring stations but there are Est - - - more than 80 secondary stations ELECTRONICS - January 1942 89 Instrument landing systems operating on ultrahigh frequencies are now being installed at a number of airports by the CAA. One simple dial enables the pilot to see at a glance whether he is taking the proper course for HANG landing even though the airport may TOGETHER be enveloped in fog. A brief explanation of the operation of this system is given. Another interesting development is automatic monitors for low frequency OR . radio ranges and fan markers. This equipment is designed to operate when the range signal deviates from the true course. It gives a warning to the pilot, and sets off a siren and lights a red light in the range station and the air- Swift course of changing world conditions make it vital line dispatcher's office. The siren may be turned off, but the red light remains that we all gear ourselves toward one objective . . . on until the range signal returns to true course. Another monitor acts VICTORY -as quickly as possible. Kenyon is proud of similarly when the fan marker signal the reaches a dangerously low volume. privilege to be a small part of the road toward that Instruments developed by the CAA to measure flutter and vibration char- objective -and come what may we pledge ourselves . . . acteristics of aircraft are now being and our company . . . to hang together -that there given ground and flight tests at the Indianapolis experiment station of the may be no "OR ELSE . . ." CAA. Other devices which are occupy- ing the attention of CAA technical men include a stall warning indicator, an automatic instrument log using KENYON TRANSFORMER CO., Inc. infrared film, and equipment for field 840 BARRY STREET NEW YORK. N. Y. inspection of aircraft fabric. A broad

F I E project aimed development O F C I at the of S IN P R N C I P A L C I T I E S

Cleveland . . 3292 Cedarbrook Rd. Seattle 2605 Second Ave. -New Orleans 611 Cited SI. moderately priced dependable instru- Chicago . . 21 E. Van Buren Sr. Las . . Angeles 2412 7th Sr. . W. Lulr Florida Kansas Olr, Me. . . 2001 Grand Ave. Dallas . . . P. O. Boa 1116. ments for the private pilot is being Sta. A Archmond. Va. . . 7106 Edgeweed Ave. studied.

Sound Simplicity NATIONAL DEFENSE AT DUKE UNIVERSITY ... Is a Basic Characteristic of Mu- Switch

That's why design engineers prefer this compact switch for applications that require sure performance. They appreciate the extra strength and dependability provided by its freedom from complex lever systems, compoundings and multiplicity of parts. And they recognize the essentially correct engineering of its one -piece spring snap This Simple Switch . . e handles 15 amperes non - action and its reverse, cross-center move- inductive load at 115 volts ment. A.C. or 1/2 H.P. at voltages up to 460 R.C. under operat- A free sample Mu- Switch, cut to ing pressure as low as 4 away reveal ounces with movement dif- its basic simplicity of design and construc- ferential of only 1 /1000." tion, will gladly be sent on request. MU-SWITCH CORP. CANTON MASSACHUSETTS U. S. A.

MU- SWITCH CORP. Dept. 51 Two members of the staff of Duke Uni- Canton, Massachusetts versity, graduates of technical schools Gentlemen: Please send me your new catalog of precision, close- movement, quick- action several years ago, who are switches. members of a class which recently completed the first national defense course in com- NAME 9'I1'I,I; 11\1PAN1 munication offered by Duke's College of Engineering in cooperation with the U. S. NO. STREET C1T1 STATE Office of Education at Durham N. C. 90 January 1942 - ELECTRONICS New Directional Microphone

CONTINUED FROM PAGE 33

/00 /000 /4000 Frequency-Cycles per Second.

Fig. 8- Frequency response curve of the super -cardioid microphone for an incidence angle of zero degress and with the microphone one foot from the sound source compared in function with the pressure P,, and voltage E. represents sure (circular) component of a two - the pressure P.,. The two voltages unit unidirectional microphone. It should be equal in magnitude and is apparent, therefore, that by sur- displaced in phase through an angle rounding a moving -coil element with proportional to frequency. This de- will be an appropriate phase shifting net- sign objective is achieved by deter- work, an effect is produced which is mining the values of the electrical equivalent to that obtained by com- circuit components for the desired 1 bining a velocity microphone with a performance, and then translating CO o J o pressure microphone. A properly these values into the acoustical ele- designed phase shifting network is ments in the microphone structure. the heart of the uniphase unidirec- The phase shift and relative mag- CARBONYL tional microphone. nitudes of pressures within the A discussion of this nature would super -cardioid microphone unit il- not be complete without a brief men- lustrated in Fig. 5, are shown in IRON tion of the principles of acoustical Fig. 7. network design. Acoustical network The phase shift angle increases analysis is carried out by the use of directly with the frequency. There- POWDER equivalent electrical circuits. The fore, the net pressure difference be- diaphragm sides also in- equivalent circuit theory assumes tween the . . and its use in many that sound pressure is equivalent to creases with the frequency. How- original and startling voltage, and that velocity of the air ever, the coil is suspended in such developments of the high volume is equivalent to electrical a manner that its mechanical im- frequency radio field. current. The corresponding circuit pedance rises directly with the fre- equivalents are as follows: Acous- quency within practically all of the tical mass (inertance) is equivalent audio frequency spectrum. The ve- FOR INFORMATION ADDRESS to inductance, acoustical capacitance locity of the coil is, therefore, inde- THE MANUFACTURER (compliance) is treated as electrical pendent of frequency and a flat fre- capacitance, and acoustical resis- quency response results. GENERAL tance is represented by electrical resistance.' Referring again to Fig. Performance ANILINE WORKS 5, the slit S is represented by a series 435 Hudson Street, N.Y.C. R, and inductance L, in Frequency response of the new resistance OR THE DISTRIBUTOR Fig. 6. The volumes under the dia- super -cardioid microphone is shown V,, within the magnet, in Fig. 8 for 0 deg. incidence at one phragm, and SOLVENTS V2, are représented as condensers foot from sound source. Polar pat- ADVANCE acoustical screen A terns are shown in Fig. 9, for ran- C, and C. The & CHEMICAL is also represented as a series resis- dom noise frequency bands of 100 to tance R2 and inductance L2. The 400, 400 to 1600, and 1600 to 6400 CORPORATION equivalent electrical circuit of the cps, indicating that the directional 245 Fifth Avenue, N. Y. C. acoustical network is shown in Fig. properties are alike at all fre- 6. Voltage E, represents the pres- quencies. ELECTRONICS - January 1942 91 The new unit is doubly wind screened, and in common with other moving coil microphones, is notably free from wind noises. This en- hances its value in broadcasting from outdoor locations where wind- age pickup may constitute a problem. The super -cardioid pattern provides an easy means of eliminating undesired noises by proper microphone orientation. Because of the inherent sturdiness of the moving -coil structure, the new microphone is well adapted for remote broadcasting as well as studio work.

Appendix Random efficiency (sometimes -IptittiL4St called directional efficiency) of a Demands directional microphone may be de- COMELP-OSIITIION fined as the ratio of power delivered Premax Antennas into the amplifier t EMENT (due to a random For defense and communications serv- sound field incident from all direc- ice, Premax Antennas, strong yet CLAROSTAT tions with equal intensity and ran- light -weight and fully adjustable, dom phase distribution) to the power meet the needs for ship -to- shore, ma- There's rine, mobile, police and other uses. * an unique museum that would have been delivered un- Send for special Bulletin showing maintained by Clarostat engi- der the same conditions by a micro- telescoping Antennas and Mountings. neers-a collection of just about phone with equal sensitivity in all every type of volume control directions. The random efficiency of 1°remax ever placed on the market, plus microphone Pro dud's several times a with a response sym- as many Claro- metrical Division Chisholm -Ryder Co., Inc. stat experimental models. It's about the normal axis is a given by:3 4214 Highland Ave., Niagara Falls, N. Y. priceless collection. Tens of thousands of dollars went into ( l Clarostat models alone. n = f Alf (B) }2sin O dB (1) 2 »J Out of it all has come the pres- where f(9) expresses the directional ent Clarostat Series M midget sensitivity of the microphone for AC RELAY composition -element control. Re- sounds arriving from angle 9 in finements such as the perfected terms of percentage of 0 deg. inci- resistive coating on bakelite dence response. IT'S AVAILABLE ring support, split -finger contact What might be called the front ... of special alloy, refined lubri- random efficiency of a microphone cant for smooth non -binding TODAY FROM STOCK ro- rl,, that is, the random efficiency tation, foolproof - soldering lug based terminals, etc., have been intro- on sounds arriving from the duced one by one until you are front hemisphere, is obtained by in- now offered the ultimate in the tegration from 0 to a/2; likewise the MERCURY TO MERCURY BREAK volume control art to date. Check rear random efficiency of a micro- MAINTENANCE FREE -DUST PROOF this statement by your own corn - phone r,r, based on sounds arriving This accurate unit has parative tests. from the rear hemisphere, is ob- been tested to 10 mil- tained by integration from n/2 to n. In lion operations without * Send Your Specs... . a microphone having a directional pattern in the form of a a failure. Available up Our production capacity is now geared Limaçon, to 30 amps. or one to meet virtually any requirements. Any resistance values, tapers, taps, shafts, f(B) _ (1 k) k cos B (2) horse power rating. It combinations. switches. Submit your re- where k is a fraction representing will operate within 45 quirements. Samples and quotations to responsible parties. the contribution of the cosine unit degrees of vertical.

to the total output. The values for II, Bulletin B gives full de- rl,, and rl, are given by substitution tails; write for it today. C LA RO STAT of Eq. (2) into Eq. (1), and inte- MAN UF.>/'Tt'ItnN/: grating from 0 to n, 0 to n /2, and Inrorporald CO. CUROSiAI, n/2 to n respectively. Performing H -B ELECTRIC CO., INC. 285 North Sixth SI. these integrations, the following re- Manufacturers of Electrical Devices `z7 Brooklyn. N. Y. lations are obtained: ©O 2500 NO. BROAD ST., PHILADELPHIA, PA. ,l = 1 - 2k -(- 4/3 lc' (3) 92 January 1942 - ELECTRONICS 1 77, = - k/2 + 1/6 k2 (4)

nr = 2 - 3/2 k + 7/6 k2 (5) The unidirectional index of a microphone has been taken as a ratio of ,q, to .

1 - k/2 + 1/6 k2 2 THESE widely used Resistors are favored U - 1 because of their noiseless operation and -3/2 k + 7/6 k2 durability and because they retain their 2 values and characteristics under extremes A plot of the function U (Fig. 2) of temperature, humidity and climatic changes. shows that the maximum unidirec- TYPE 65X tional ratio of 14 to 1 is obtained Actual size available in when k = 0.63. The pattern cor- Other types STANDARD RANGE lower values responding to this maximum, f (0) the 1000 ohms to 10 megohms. 0.37 + 0.63 (cos 0) has been called a super -cardioid. Substitut- BULLETIN NOISE TESTED RESISTOR 37 , ing k = 0.63 into Eq. (3), the super - FULL DET At slight additional cost, resistors in the cardioid pattern is found to have GIVESof the differ- Standard Range are supplied with eacl- resis- It shows illustrations Molded the following S. White tor noise tested to standard: a random efficiency of 27 percent. types of S. about ent gives details "For the complete audio frequency and etc. A Resistors dimensions, range, resistors shall have less noise construction, will be mailed than corresponds to a change of re- with Price List, copy, of 1 in 1,000,000." REFERENCES Write for it-today. sistance part on request. J. Weinberger, H. F. Olson and F. Massa, Uni -Directional Ribbon Micro - HIGH VALUES phone, Jour. Acous. Soc. Am., Vol. 5, No. 2, v. 139 (1933). 15 to 1,000,000 megohms. Benjamin Baumzweiger, Graphical De- termination of Random Efficiency of Microphones, Jour. Acous. Soc. of Am., Vol. 11. No. 4, p. 477 (1940). Ralph P. Glover, A Review of Cardioid S. S. WHITE type Uni- Directional Microphones, Jour. The S. S. White Dental Mfg. Co. Acons. Soc. Am., Vol. 11, No. 3, p. 296 (1940). INDUSTRIAL DIVISION R. N. Marshall and W. R. Harry, New Department R, 10 East 48th St., New York, N. Y. Microphone Providing Uniform Direc- tivity over an Extended Frequency Range, Jour. Acons. Soc. Am., Vol. 12. No. 4, v. 481 (1941). Benjamin Baumzweiger, A New Uni- directional Microphone, New Products Section, ELECTRONICS, p. 62, February, 1939. For a rigorous mathematical analysis of ALLIED the Uniphase, see B. B. Bauer, Uniphase Unidirectional Microphones, Jour. Acous. Soc. of Am., Vol. 13, No. 1, p. 41 (1941). Standards on Electroacoustics. Institute GLASS of Radio Engineers, p. 13 (1938).

Fig. 9- Horizontal polar patterns BASE for several frequency bands. Note the similarity of the directional patterns at the different frequencies RECORDING DISCS

I F you have not been using or have not yet tried Allied's New Glass superior qual- I . Base Discs, a trial will convince you of their merits and ity-at no premium in the cost to you. We invite you to try this disc - that is how we obtain new customers. We feel certain that you will re- order -that is how we build sales volume-from satisfied users. Your telephone call, letter, wire or cable will receive our prompt and courteous attention.

ALSO AVAILABLE recoating ser- PROMPT DELIVERY direct from the manufac- vice for your old aluminum discs. turer - fo any part of the United States, Delivery in one week. Details on Canada, South America and to some foreign request. countries. ALLIED RECORDING PRODUCTS CO. /00 -400 C PS. 400-/6O0 C.PS 21 -09 43rd Ave., Long Island City, N. Y. - -- /600-6400 0P5 . (Rar.dom 'noise source.) Phone: STillwell 4 -2318 Cable: Allrecord New York

ELECTRONICS - January 1942 TUBE S Another DuMont Characteristics of cathode -ray and television picture tubes are presented this "First"... month in addition to the new receiving tube types registered by the RMA Data Giant- Screen Bureau during November 1941 CATHODE -RAY Tube Registry Type 14S7 (GL) New tube types registered by the RMA TRIODE -HEPTODE converter, remote cut- OSCILLOGRAPH Data Bureau during November 1941 off, heater type, T -9 integral glass envelope -base, seated height 2/ inches Type 7W7 (GL) (max), 8 -pin lock -in base. PENTODE voltage amplifier, sharp cutoff, heater type, T -9 integral glass envelope base, seated height 2/ inches (max), 8 -pin lock -in base. RATINGS Ef = 7.0 v If = 0.48 amp Eh = 300 v (max) E,2 = 150 v (max) TYPICAL OPERATION Ef = 6.3 v I r = 0.45 amp Ea = -2 .2 v (cathode TYPICAL OPERATION resistor = 160 ohms) Ef = 12.6 v Ie =10ma If = 0.150 amp I2 =3.9ma Eb (heptode) = 250 v g- = 5500 µmhos Ea (triode) = 250 v r,, = 0.3 megohm Ls, 4 = 100 v E., (for cathode Triode Grid Resistor = 50,000 current cutoff) ohms -6v rp (heptode) = 1.25 megohm Ci = 9.5 µµf (approx) C., = 7.0 µµf I, (triode) = 0.4 ma Cop = 0.0025 µµf lb (heptode) = 1.8 ma (max) Ie (triode) = 5.0 ma Basing 8BJ -L-5 7.2,4 =3.0ma Total Cathode Current = 10.2 ma Type 14W7 (GL) g, (heptode, E,4 = - 2 v) _ 525 mhos }r Designed particularly for 1ec;ure -room PENTODE voltage amplifier, sharp cut- g (heptode, E.4 = - 21 v) = 2 µmhos and demonstration purposes, this new off, heater type, T -9 integral glass en- DuMont Type 233 Cathode -Ray Oscillo- velope base, seated height 2/ inches, S- TRIODE SECTION ONLY graph provides huge oscillograms on its pin lock -in base. Ef = 12.6 v 20 -inch high- intensity screen. Also in- If = 0.150 amp valuable for RATINGS Eb = 100 v (max) critical laboratory investi- E =ov gations. Ef = 14 V Ib =6.5ma If= 0.24 amp r, = These features, among many others, war- Ee = 300 v (max) 11,000 ohms E,2 = 150 v (max) p- = 1650 µmhos rant your attention: Accelerating po- µ = 18 tenial of 6000 volts; deflection TYPICAL amplifier OPERATION DIRECT INTERELEC- response flat from 75 kc. to less than 1 TRODE CAPACITANCES c.p.s.; Ef =12.6v phase inverters and push -pull If = 0.225 amp Heptode Grid 1 to Heptode amplifiers provide symmetric deflection Ea = 300 IT Plate = 0.02 µµf (max) with single ended input; d.c. positioning E.2 = 150 v Heptode Grid 1 to Triode Plate voltages Ea = - 2.2 v (cathode = 0.10 µµf (max) insure instantaneous image lo- resistor = 160 Heptode Grid 1 to Triode Grid caiion; Z -axis amplifier, enabling accu- ohms) 1 and Heptode Grid 3 = 0.35 rate determination of time intervals dur- 1a =10ma µµ (max) I,2 = 3.9 ma Triode Grid to Triode Plate = ing sweep of trace, essentially uniform g,. = 5800 ',mhos 1.0 µµf in response from 10 to 750,000 c.p.s. rp = 0.3 megohm Signal Input = 5.0 µµf Ea (for cathode current Oscillator Output = 3.5 µµf Sturdy metal cabinet. Rubber -tired lock- cutoff) = -6 v Mixer Output = 8.0 µµf ing casters. Gray wrinkle finish. 60" C,, = 9.5 µµf Basing 8BL -L-7 h. x c.,, = 7.0 µµf 28" w. x 36" d. 325 lbs. 60 -cycle Cpp = 0.0025 µµf (max) 115 v. 350 watts. Basing 8BJ -L -5 * Write for Literature . Type 6C5GT /G Type 6J5GT /G TRIODE, heater type, T -9 glass envelope, TRIODE, heater type, T -9 glass envelope, seated height 21 inches (max), 6 -pin seated height 2i inches, 6 -pin small small octal base. octal base. Ef = 6.3 v Ef =6.3v If = 0.3 amp If= 0.3 amp Eb =250V Eb = 250 v E, = - 8 v E, = -8 v ALLEN lb =8ma Ib =9.0ma B. DU, MONT g- = 2000 µmho= o- = 2600 mhos -re = 10,000 ohms Kp = 7700 ohms LABORATORIES, Inc.''' -° µ 20 x,; = = 20 C,k = 4.4 µµf Ci, = 4.2 µµf Passaic * New Jersey Cps =12µµf Co.e = 5.0 µµf Cop = 2.2 µµf Cable Address: Wespexfin, New Yo, k Cop = 3.8µµf Basing 6Q -1 -1 Basing 6Q-1 -0 94 January 1942 - ELECTRONICS. Type 7S7 (GL) FERRANTI THE basing of the type 7S7 tube as given in the July 1941 issue of ELEC- PRODUCTS TRONICS was 8AR -L -7. This has been ON modified to include the addition of a Transformers for every fifth grid connected to the cathode and SPECIAL TRANSFORMERS electronic, sound, com- hence to pin No. 7. The new basing munication, industrial, is 8BL -L -7. The characteristics and the new basing diagram of the type If you have a defense order and laboratory use - 7S7 are reproduced below. and need QUALITY trans- miniature aero transformers FAST . . . you can formers for aircraft and TRIODE -HEXODE converter, remote cutoff, them from Ferranti. That's the whole heater type, T -9 integral glass envelope - get portable work - high base, seated height 2t inches (max), story. Large or Small orders. Standard power plate and fila- 8 -pin lock -in base. or Special. ment transformers - fil- TYPICAL OPERATION ters, equalizers, modu- (I) 60 YEARS EXPERIENCE Es = 6.3 v etc. In = 0.30 amp (2) UNMATCHED PRESTIGE lation sets, rectifiers, Eb(hexode) = 250 v electrostatic voltme- Es(triode) = 250 v (3) EXPERIENCED ENGI- - Ec2, 1 = 100 y NEERING ters, portable voltmeters, Triode Grid Resistor = 50,000 ohms (4) ADEQUATE EQUIPMENT cmmeters, phase rota- rp(hexode) = 2 megohms (approx) (5) THE ECONOMY INHER- tion indicators, special L(triode) = 0.4 ma ENT IN QUALITY PROD- Ib(hexode) = 1.7 ma UCTS testing equipment, and /b(triode) = 5.0 ma Ia,1 =2.2ma numerous other instru- Total Cathode Current = 9.3 ma rnents. u(hexode, Ers = - 2v) = 600 µmhos g.(hexode, Er, = - 21 y) = 2 Wr:te to Ferranti for a quick solution mhos to your transformer problems. TRIODE SECTION ONLY En = 6.3 y ELECTRIC Eb = 100 y (max) E. =0v Is = 7.0 ma INCORPORATED r = 10500 ohms 9m = 1700 µmhos DIRECT INTERELECTRODE CAPACITANCES R..C. A. BUILDING, NEW YORK, N.Y. Hexode Grid 1 to Hexode 8BL Plate = 0.04 µµf Hexode Grid 1 to Triode Plate = 0.10 µµf Hexode Grid 1 to Triode Grid 1 and Hexode Grid 3 = 0.35 µµf Triode Grid 1 to Triode Plate = 1.0 µµf Signal Input = 5.5 µµf Oscillator Output = 3.5 µµf Oscillator Input = 6.0 µµf Mixer Output = 9.0 µµf Basing 8BL -L-7

ARMY REPAIRS

ICRODHONES

Model 202 A modern CARBON microphone designed especially for Model 202 -5, Sin- Police, Aircraft and Military communication. Every gle button, list price $14.00 tested development has been included. The head is a Model 202 -D, Dou- separate unit suspended on cork. The concave button ble button, list price $16.50 allows operation in any position. Every model is spray - an extra lead It is the job of the Royal Army Ord- proofed. The "press -to- talk" switch includes for relay operation. Switch has a double spring return, is non sticking and positive in action. nance Corps to keep the wheels of the Six feet of rubber covered shielded cable. Speech is clean, crisp and blast -proof even when army well oiled and running smoothly. the user's lips are touching the grille. At the central Ordnance Depot of South- Operating Characteristics east England, and its many sub depots, Voltage source: 41/26 Current: 5 -10 milliamperes Output: -10 DB. Frequency may be found all types of war materiel response: 60 -5,000 cycles, rising with frequency, peaking through speech range Weight ready for issue to the fighting forces. 11 ounces. At this depot, stores are refurbished and made like new and nothing is ELECTRO -VOICE MFG. CO., Inc. wasted. The burned out equipment on BEND, INDIANA the left will be repaired to match its 1239 SOUTH BEND AVENUE, SOUTH shining counterpart on the right Export Division: 100 Varick St., New York, N. Y.- Cables: "Arlab" ELECTRONICS - January 1942 95 1WIT' Type 6F6GT /G JACKSON PENTODE power amplifier, heater type, ® T -9 glass envelope, seated height 2Z Resistance -Capacity Tuned ATR inches, 7 -pin octal base. Er =ó.3v. If = 0.7 amp * AUDIO OSCILLATOR VIBRATORS Iib =250V F, z =250v Ea= -16.5v I b (zero signal) = 34 ma DEFENSE!!" la (zero signal) = 6.5 ma "for ry = 80,000 ohms m = 2500 ',mhos RI = 7000 ohms Po = 3.2 watts (8 %) Basing 7S -0 -0

Cathode -Ray Tubes

Type 2501A3 Here is a tried, proven and accepted DuMont Audio Oscillator whose brilliant performance sets it apart from other makes. CATHODE -RAY tube; medium- persis- Audio Frequency voltage is developed at its Fundamental Frequency-by the Re- tance, green fluorescent screen; elec- sistance- Capacity Tuned Principle. This is trostatic focus and deflection; usual ap- not a "beat frequency" oscillator and plication-oscillographic; diameter, 3 contains no R.F. circuits. Operation is vastly simplified. Characteristic faults of inches; 7 -pin base. old style methods are eliminated. Glass EI = 2.5 v enclosed direct reading dial is accurate to Ir = 2.1 amps within 3% or one cycle. Many other out- E (anode 1) = 500 v (max) standing features. Price $88.50. E (anode 2) = 1500 v (max) PROVEN UNITS E (grid) for cutoff = - 80 v Write for Deflection Factor descriptive literature of the Dt - Ds = 100 v (d.c.)/kilovolt-inch THE JACKSON ELECTRICAL Da - D4 = 100 V (d.c.) /kilo- HIGHEST QUALITY volt -inch * INSTRUMENT COMPANY Engineered to perfection, ATR Vibrators 2501A3 -C3 123 Wayne Avenue Dayton, Ohio set high standards of performance and construction. Available for any operating input voltage from 6 volts DC to 220 volts DC in a wide variety of designs for practically any application. Type 2501C3

In addition to the most complete DuMont WIRE & RIBBON line of vibrators, ATR offers a very For - extensive line of Inverters and CATHODE -RAY Direct Heated other Vibrator- Operated Power Sup- tube; short -persistance, plies for changing one DC voltage blue fluorescent screen; electrostatic ELECTRON EMITTERS to another DC voltage or to invert DC to AC. focus and deflection; usual application -oscillographic, diameter 3 inches, 7- in VACUUM TUBES pin base. EI =2.5v If=2.1amps E (anode 1) = 500 v (max) ATR vibrators, the heart of vibrator - E (anode 2) = 1500 v (max) In a complete range of sizes operated power supplies, are proven E (grid) for cutoff = 80 v Deflection - units of the highest quality, Factor and alloys for Transmitting, engineered D, - Da = 100 v (d.c.) /kilo- to perfection. They are backed by volt -inch Receiving, Battery and Hear- more than ten years vibrator Da - D4 = 100 v (d.c.) /kilo- of design volt-inch ing -Aid Tubes and research, development and manu- ... facturing -AIR pioneered in the 2501A3-C3 vibrator field. American Television & elted and worked under Radio Co. has consistently devoted its efforts and energies to the perfection close supervision to assure and production of vibrators and asso- Type 2511A5 maximum emissivity, uni- ciated equipment, and today, after formity and the highest ten years of painstaking, persistent and DuMont diligent work resulting in steady de- tensile strength . . . velopment and progress, is considered CATHODE -RAY tube; medium- persis- the World's leader in its field. tance, All ATR green fluorescent screen; elec- WIRES drawn to .0005" diam. Products incorporate only the best ma- trostatic focus and deflection; usual terials and workmanship and are care- application -oscillographic, balanced RIBBON rolled to .0001" diem. fully manufactured under rigid engi- deflection and television, diameter 5 neering inspections and tests, making inches, 11 -pin magnai base. SPECIAL ALLOYS made to meet them the finest that can be built. Er = 6.3 v Ir =0.8amp individual specifications ... E (anode 1) = 600 v (max) E (anode 2) = 2000 v Max) For Additional Information E (intensifier) = 6000 v (max) Address ATR Vibrator Division of E (grid) for cutoff = - 50 v Deflection Factor Dt - Ds = 28 v (d.c.) /kilo- AMERICAN TELEVISION & RADIO CO. volt -inch D3 - Da = 25 v ST. PAUL, MINN., U.S.A. volt -inch 2511A5-B5-05-D5 96 ELECTRONICS - January 1942 Type 2507B5 * * DuMont

CATHODE -RAY tube ; long -persistance, green fluorescent screen; electrostatic focus and deflection; usual application -oscillographic and high voltage; diameter 5 inches, 5 -pin base.

Ef =2.5v * If = 2.1 amps * E (anode 1) = 1000 v (max) E (anode 2) = 3000 v (max) E (grid) for cutoff = - 120 v Deflection Factor Di - D2 = 55 v (d.c.)/kilovolt-inch Ds - D4 = 50 v (d.c.)/kilovolt-inch 2507Á5-B5 -05

* Type 2507C5 DuMont CATHODE -RAY tube; short -persistance, blue fluorescent screen; electrostatic focus and deflection; usual application Permopivots tor precision instruments in air - planes have already been tested and proved -oscillographic and high voltage; di- superior. They are tipped with Permometal -a ameter 5 inches; 5 -pin base. non -corrosive, smooth wear -resisting, non -magnetic * precious metals alloy with a low coefficient of friction. Ef = 2.5 v Aviation instrument pivots and contacts, phono- If = 2.1 amps graph needles, long life fountain pen tips-are E (anode 1) = 1000 v (max) of these remark- E (anode 2) = 3000 v (max) just a few of the countless uses E (grid) for cutoff = - 120 v able alloys. Deflection Factor Write for detailed data. Di - Ds = 55 v (d.c.)/kilovolt-inch PERMO PRODUCTS CORP. Ds D4 =150 v (d.c.)/kilo- Itt. - 6427 Ravenswood . \.e. Chicago. volt-inch MANUFACTCItI'.( \IETAI.I.I.1WGI'l'.&. 2507Á5 -B5 -05 * 197103577' /7/. *

Type 2509A5 DuMont For DEVELOPMENT ENGINEERS CATHODE -RAY tube; medium- persis- tance, green fluorescent screen; elec- Who Want PROMPT DELIVERY trostatic focus and deflection; usual application-oscillographic and balanced TRANSFORMERS deflection; diameter 5 inches, 7 -pin of base. The transformers you buy from us meet your three Ef =2.5v chief requirements. I- Highest quality in mate- If= 2.1 amps E (anode 1) = 500 v (max) rials and workmanship; 2- Proved Designs that give E (anode 2) = 1500 v (max) E (grid) for cutoff = - 80 v dependable performance; 3- Promp#ness of de- Deflection Factor Di - Ds = 60 v (d.c.)/kilo- livery, to enable you to beat your own time limita- volt-inch D, - D4 = 60 v (d.c.)/kilo- tions. volt-inch 25O9Á5 -05 Our wide experience with a variety of designs, serving the most exacting buyers in both the audio and power field gears us to this type of service. The Type 2509C5 companies we serve testify to the top quality of our product. Our engineers will be glad to help DuMont you solve your particular transformer problems. CATHODE -RAY tube; short-persistance, blue fluorescent screen; electrostatic WRITE THE HEADQUARTERS FOR focus and deflection; usual application -oscillographic and balanced deflec- AMERICA'S TRANSFORMER PROBLEMS tion; diameter 5 inches; 7 -pin base. Suppliers to manufacturers demanding highest quality Ef =2.5v If = 2.1 amps E (anode 1) = 500 Jr max) E (anode 2) = 1500 v max) TRANSFORMER CO. E (grid) for cutoff = - 80 v NEW YORK Deflection Factor Sales Department Ih - Ds = 60 v (d.c.)/kilovolt-inch) 480 LEXINGTON AVE. NEW YORK, N. Y. Da - D4 = 60 v (d.c.)/kilovolt-inch 2509A5 -05 ELECTRONICS - January 1942 97 30-40 Mc Receiver (Continued from page 25) first a -f tube. Operating Electrical under a and Industrial no- carrier condition the grid of the la°ra toru first audio tube is biased beyond cut- CISION off, thus effectively silencing the audio output of the receiver. A small , m negative shift in a -v -c voltage pro- q p duces approximately a 40 times shift çsI at the plate of the d -c squelch amplifier in the positive direction. A portion of this shift is applied to the grid return of the 7C6 audio tube. The shift is limited by the diode to a value which permits only a very small grid current to flow and the first audio tube operates as if the 10 The "PRECISION" catalog No. 42 -E describes more than 40 radio megohm grid -leak were returned to and industrial electrical test equipment models . . . Tube Testers, Combination Tube and the cathode. The sensitivity of the Set Testers, AC -DC Multi -range Testers, Vacuum Tube Multi -range Testers, Signal squelch circuit is such that the audio Generators, Circuit Testers, etc. While the greater proportion of these instruments are for industrials, labora- channel may be held inoperative with tories and governmental agencies, serving to expand our war effort, a fair per- no signal, and be entirely opened by a centage is still available, commercially, through leading radio parts distributors. signal of less than 1µv, or if set to *ADDITIONAL PRECISION MANUFACTURING FACILITIES are now available for the production of national defense orders, to specification. Principals reject signals below three micro- interested are Invited to contact our factory directly. volts the circuit may be entirely opened with an input of 3.5 µv. Due to the protection afforded the a -v -c MUM úïß 52 circuit by the noise silencer, the /NDUSTR/AL LABORATORY ;RAD/O TELEV/S/ON squelch circuit remains relatively insensitive to ignition noise. PRECISION APPARATUS COMPANY 647 KENT AVENUE BROOKLYN. N. Y. Export Division: 458 Broadway, New York City, U.S.A. Cable Address: Morhanex Low -pass Output Filter The inclusion of a simple low-pass output filter, having a cutoff fre- STABILIZED A. C. VOLTAGE quency of 5,000 cps, increased the usable sensitivity of this receiver by UP TO 25 KVA a factor of two to one. This result is reasonable when it is considered that the random noise output of a wide band receiver does not cut off at 3 to 5 kc as in the case of the Varying Input Voltage Constant Output Voltage more conventional narrow band unit, 95 -130 VOLTS 115 VOLTS ±`'c but extends to possibly 25 kc before being appreciably attenuated by the selectivity of the i -f amplifier. The importance of this high frequency noise output is greatly increased by INSTANTANEOUS ACTION NO MOVING PARTS the rising impedence characteristics of the usual output transformer - When a precision electrical device or a critical process is powered from speaker combination. Inclusion of this type of filter serves to minimize an AC line, a Raytheon Voltage Stabilizer will permanently eliminate one of the principle disadvantages all of the detrimental effects caused by AC line voltage fluctuations. inherent in broad i band -f ampli- Made for all commercial voltages and frequencies, single or three phase. fier receivers. Raytheon's twelve years of experience in successfully applying the Power Requirements Stabilizer to hundreds It is usually desirable to hold the of perplexing voltage fluctuation problems is at power consumption of a mobile re- your service. It will pay you to take advantage of our engineering skill. ceiver to a minimum without sacri- ficing performance. The type KU -R Write for Bulletin DL48 -71 JE describing Raytheon Stabilizers. receiver draws 5 amps. from a 6 -volt battery, which is moderate when it RAYTHEON MANUFACTURING CO. is considered that twelve tubes are Willow employed. Power savings not corn- loo Street, WALTHAM, Massachusetts

98 ELECTRONICS - January 1942 mon in usual practice were effected by the following points. 1. The power consumed by the B supply will be roughly proportional RADIO PARTS to the square of the B supply volt- and age. The item which usually dic- ELECTRONIC EQUIPMENT tates the required B voltage is the for DEFENSE! required audio output. By mounting the loud speaker separately, at approximately ear level, intelligibility GREATEST STOCK EVER IN RADIO HISTORY! is greatly increased and much less audio output is required. An output CONDENSERS RESISTORS TUBES METERS TRANS- of 500 mw used in this manner ap- FORMER; PLUGS JACKS pears to be adequate and is readily SWITCHES RELAYS, etc. obtained with a plate voltage of 150. 2. The use of sharp cutoff r -f and IM MEDIAE DELIVERY 021 i -f amplifier tubes as previously dis- ON ALL STANDARD PRODUCTS! cussed accounts for further saving. A Complete Source of Supply for 3. Tubes having 0.15 amp. heaters ENGINEERS LABORATORIES in MICA INDUSTRIAL ORGANIZATIONS in place of 0.3 amp. heaters are used MANUFACTURERS AIRPORTS BROADCAST STUDIOS COLLEGES wherever suitable tubes of this type MARY U. S. GOVERNMENT CAPACITORS AGENCIES are available. Write. vire or phone us on your A slight sacrifice in primary most urgent requirements. power consumption was made in the Climaxing an outstanding selec- FREE 416 PAGE CATALOG selection of a rectifier in - - tube type tion of mica receiving and trans- Address Dept. EJ on your firm letterhead. place of a self rectifying vibrator. NEW YORK'S OLDEST mitting condensers from tiny It was felt that this was more than - RAC 10 SUPPLY HOUSE "postage-stamp" molded -in -bake- - Telephone BArclay-7-1840 - offset by elimination of an occasional complication arising from the va- lite condensers to extra- heavy- riety of battery polarities encoun- duty micas -Aerovox offers its 'RADIO CO. stack -mounting mica capacitors 212 FULTON ST, tered. NEW YORK, N. Y Space for power components was as standard items. Heretofore reduced and added simplicity ef- made only to order, these capa- fected by the use of a resistor - citors are now generally avail- DEFENSE REQUIREMENTS capacitor filter in place of the usual able. And that fact is amply re- iron core choke arrangement. The flected in lowered prices. drop in the filter resistor is used as ELECTRICAL bias for the audio power-output tube. Since compact arrange- STACK -MOUNTING the MICAS Type 1940: ment of all circuits in this receiver mid. 8" dia. x 10" 35,000 v, to tall .00001 COIL WINDINGS necessitates complete isolation filter- .01 mid. 15,000 . dia. Type 19 3 x 212., ing these added filters are, where 3,000 6.0004 tail. v. . v, to .02 mid. & TRANSFORMERS necessary, designed to augment the 1960: Type 41/4 dia. x simple basic power filter. vmfd' 15,000 3" tall. Designed to meet specific require- 1,000 v, to .25 mid It should be noted that even Type 1970: ments or to your specification. .00001 5-V" dia. though the vibrator power supply is 1.970 20.000 x 4" tall. 1,000 v, v- to .5 mld. an integral part of the receiver unit, Type COIL WINDINGS 1980: 5 -3/4" din. only the most conventional r -f filter- td. 35,000 x 5.34" tall. ELECTROMAGNETS 5.000 v v, to .05 mid. SOLENOIDS ing is required for noise -free power COIL ASSEMBLIES supply operation. The noise silencer serves to remove the vibrator inter- PAPER INTER -LAYER SECTION ference which, by radiation or other- Write for DATA .. . BOBBIN WOUND wise, may escape suppression in the Catalog sheets on stack -mounting micas FORM WOUND -f filter. This reliance and other extra- heavy -duty capacitors not power supply r listed in our general radio catalog. sent on the noise silencing circuit to to professional radio workers writing on Equipped for vacuum and Ares - cover an additional function results business stationery. And for your con- sure impregnation-varnish or venience, individual items can be ordered in a saving in space and greater through local Aerovox jobbers. compound. freedom in mechanical layout.

An experienced organization at Editor's note.- Regarding this method of your service prepared to assist in indicating sensitivity, the authors state, "an uuntudulated 1 µr signal is fed into the design or cooperate on problems. receiver and the noise output measured. Then the input is modulated 30 percent and a DINION COIL COMPANY second reading taken. This reading will NEW BEDFORD, MASS., U S. A. he approximately 3 times the first. Now the P.O. BOX D CALEDONIA, N. Y. input is increased to 1.4 µv and the two In Canada: AEROVOX CANADA LTD., Hamilton, Ont. readings taken again. The §e readings will be EXPORT: 100 Varick St., N. Y., Cable 'ARLAB' 4 times the first set." ELECTRONICS - January 1942 99 New DCB Set -up NEWS OF THE INDUSTRY for Communications In a move to coordinate handling of Year -end summary strategic materials and metals for the by Institute of Radio communications industry, the Defense Engineers shows that 1941 was another Communications Board and OPM have outlined their respective responsibil- banner year with 14 million radio receiv- ities. OPM establishes a Communica- tions Branch and is to have all re- ers made. Government services need sponsibility for implementing and proc- men ; allocation essing the policies recommended by the of funds to Signal Corps DCB. Two, at least, of the new key officials involved in the new setup have Military Needs Radio Men were low- priced table-model sets. Al- communications backgrounds. Leighten though much of the productive capacity H. Peebles is be BOTH ARMY AND slated to appointed as NAVY are clamoring which made such manufacturing pos- the head of the new Communications for experienced radio personnel. For sible will be shifted to other lines dur- some time the Navy has Branch. He is an engineer with ex- been enlisting ing 1942, the evidence paints to the perience with recruits to operate and maintain the General Electric and J. tremendous productive capacity that is G. White, with whom he supervised important aircraft locater used so suc- the available for making any sort of radio construction of the high -power long - cessfully in Great Britain. Here it is equipment which can be produced on a known as the Radar, and for military wave radio stations operating at Bel- production line. The detailed break- mar New reasons, its principle of operation is not and Brunswick, N. J., down of the year's production will be Hawaii, Chatham and Marion, Mass., divulged. Men trained in its use, how- found in the table below. ever, are assured of an interesting and and Bolinas and Marshall, Calif. Dur- Comparison of 1941 output with that ing NRA he was deputy Administrator useful occupation in the defense effort. of other years is given in the following At the moment 5000 men are needed table: in charge of the telephone and tele- for the Radar. These must be high graph codes. school graduates, and must either be or Year Number of receivers One of the liason officers between have been experienced amateur opera- 1941 13,800,000 OPM and DCR will be George J. Demp- tors or be experienced radio service 1940 11,831,000 sey, with the FCC since 1935 in commen. Upon enlistment in the United 1939 10,760,000 mon carrier division. Mr. Dempsey States Navy Reserve as Class V -6 with 1938 7,142,000 has had long experience in the Bell rank of Radiomen, Second Class, base 1937 8,065,000 System, with the Signal Corps and in pay $72 per month, the men will un- 1936 8,248,000 telephone regulation in the Interstate dergo extensive training before assign- 1935 6,026,000 Commerce Commission. Two other ment. 1934 4,556,000 DCB engineers are yet to be appointed. In the anual report of the Chief of 1933 4,157,000 All three will report to E. K. Jett, Naval Operations, Admiral Harald R. 1932 2,444,000 Chief Engineer, FCC, and to Mr. Stark this month stated that of the 1931 3,594,000 Peebles. 903 officers in the Naval Reserve, 653 1930 3,838,000 are now on active duty and of approxi- Prior to 1930 15,000,000 mately 7,000 enlisted men, 5,277 are now in active service. Signal Corps, too, is looking for qualified radio amateurs between ages of 18 and 35, unmarried and in good physical condition. BROADCAST RECEIVER PRODUCTION FOR 1941 Other amateurs who are dis- ESTIMATED FROM FIRST NINE MONTHS OF YEAR qualified by age, dependents or minor physical disabilities are needed to serve Retail Average % of % of in a civilian capacity in Army radio No. of Dollar List Unit Dollar stations, thus releasing enlisted per- Type Units Volume Price Volume Volume sonnel for active military duties. Licensed radio amateurs had another Radio Receivers . 6,100,000 $108,000,000 $17.70 44.3% 24.65% opportunity to serve their country table models when Federal Security Administrator Radio Paul V. McNutt called upon Receivers, 640,000 46,500,000 72.70 4.64 10.60 them to consoles apply at State employment offices for free training in marine radioteleg- Portable raphy. Some 1,500 new radio operators Sets 1,660,000 42,800,000 25.70 12.05 9.76 will be needed during the next two Automobile Sets years to man ships now being built 3,040,000 111,000,000 36.50 22.10 25.30 for the merchant marine. Farm Battery Sets 790,000 20,900,000 26.40 5.74 4.77 Radio -Phono Comb. Record Production of table models 1548,000 21,600,000 39.40 3.98 4.93 Broadcast Receivers console 416,000 61,800,000 148.00 3.02 14.10 THE YEAR 1941 just closed, set another Radio -Phono -recorder 53,000 7,100,000 134.00 .38 1.62 record for annual receiver production, topping the record -breaking figure of Record players 186,000 4,750,000 25.50 1.35 1.08 last year by some 2 million units. Ac- cording to a year -end summary of pro- Chassis without 330,000 13,700,000 41.50 2.39 3.13 duction made by the Institute of Radio cabinets Engineers 14 million receivers for re- FM adapters 9,000 360,000 40.00 .06 .08 ception of broadcast signals were manufactured. The majority of these TOTAL: 13,772,000 $438,510,000 $31.80 100. 100. 100 January 1942 - ELECTRONICS DCB Rules on Alien Visitors Brigadier General Albert Brown of the General Staff. Procedures necessary when aliens wish Navy has also presented proposals to visit plants in which communications for additional funds for communication materials are either manufacturered equipment on commercial ships, for di- or used have been laid down by the rection finding and locating ships by DCB. Permission must be obtained radio beams and for fleet training from the War or Navy Departments equipment. or from the Office of Scientific Re- The first meeting of the Civilian search and Development according as Technical Advisory Board of the Chief to the nature of the work going on in Signal Officer of the Army occurred the plant concerned. Permission is on December 1. At that time Major granted after inspection of papers of General Dawson Olmstead stated that the aliens desiring entry to plants. with the first two supplemental ap- Papers required are representations propriations, the Signal Corps had been from high diplomatic officials of the granted over one and one -quarter bil- alien's country, showing the reason for lion dollars for expenditure. At the the visit, what the visitor desires to see time of this meeting the Signal Corps and what use is to be put to the infor- had approximately 3,800 officers, 40,- mation secured. These documents are 275 enlisted men and 10,000 civilian to be forwarded to DCB together with employees with an additional 1,128 of- statements from the company involved. ficers and 26,205 enlisted men author- ized in pending legislation. New Funds for Cone mutt ieations SIGNAL CORPS AWARDS Contracts awarded ($50,000 and over A FUND OF $239,000,000 for the Signal for radio apparatus since December 1. Corps was approved by the House Ap- propriations Committee December 3 Concern Receiving in the Third Supplemental National Award Item Amount Defense Appropriation Bill. This money RCA Mfg. Co. Radio $947,389 would be used for the needed equip- equipment ment for 8 aircraft warning regiments, Hammarlund Mfg. Receivers 49,243 8 aircraft warning battalions and other Co. units. This is in addition to appropria- Bendix Radio Div. Radio parts 695,302 tions previously secured. One objective Belmont Radio Receivers 74,261 of these new funds would be to expand Corp. and parts the aircraft warning units by 765 of- Amperex Elec- Tubes 553,250 ficers and 16,750 enlisted men. About tronic Pro. $3,000,000 is needed for new radio Westinghouse Tubes 580,000 manufacturing facilities, according to E & M Co.

1941 Broadcast Receiver Production Whether it be a 315 -pound 13,772,000 Units - $438,510,000 Retail Dollar Volume Battery Charger (220 AC, 3 phase, 60 cycle) for use in Railway Cars ... or a 7-ounce Auxiliary Box (110 AC, 400 Cycle) for operating an Aircraft Fluorescent Lamp Consoles ... you'll find the right answers Portable Sets 640,000 to your electrical problems at 1,660,000 ' s 72.70 Electronic Laboratories. $ 25.70 For, Electronic maintains a specialized engineering service ... highly trained, thoroughly experienced, amazingly resourceful ... - Auto Sets - Table Models working daily kith America's 3,040,000 = 6,100,000 units key defense- producing companies and important civilian sup- $ 36.50 Average list price $ 17.70 ply manufacturers. Electronic's full facilities are always at your disposal. For further information, address: ,9 / ?O,

INDIANAPOLIS, INDIANA

ELECTRO\ICS -- January 19 -12 grid control; mercury rectifiers-cur - rent wave form and plate current; high NEW PRODUCTS vacuum rectifiers -current wave form, and plate current; high vacuum control tubes -wave form, plate current, Month after month, manufacturers de- and grid control; full -wave rectifiers (2 plate) -wave form and plate cur- velop new materials, new components, rent on each half, individually. The instrument is provided with ad- new measuring equipment; issue new justments for intensity, horizontal and technical bulletins, new catalogs. Each vertical amplitude, and focus for the oscilloscope. It is housed in a black month descriptions of these new items crackle -finish box and has a sloping control board. The unit which comes will be found here with a 6 ft. cord is semi -portable and its construction lends itself to shop and laboratory checking of tubes. It High -Gain Antenna losses which may occur through appli- operates on 110 to 120 volts, 60 cps. cation of loading introduced within A NEW TYPE OF ANTENNA, known as the transmitter itself to compensate High -Gain, has been announced by Jef- for lack of antenna length. Blackout-Panel Oscillograph ferson- Travis Radio Mfg. Corp., 380 While greatest operating efficiency ALLEN B. Second Avenue, New York, DUMONT LABORATORIES, INC., N. Y. The with the antenna is experienced when Passaic, N. J., announce unit provides improvement in a new black- trans- it is tuned to a single frequency, im- out -panel Type 208 oscillograph which mitter range and receiver performance provement is also evident on adjacent frequencies within a narrow band, as for example 2100 kc to 2800 kc in the marine frequency range. Dead spots and directional effect are reduced and coverage is increased. Receiver operation is also improved, since the antenna is tuned, and signal to noise ratio is increased. Checker for Industrial Tubes A SELF-CONTAINED TUBE CHECKER (known as Universal) for industrial type electron tubes has been announced by Weltronic Corporation, East Outer Drive, Detroit, Mich. The instrument is provided with seven sockets and may be used to check many well -known make and type of industrial tubes, except ignitrons. Special tubes may be checked through the use of socket adapters. Vacuum tubes can be checked with a milliammeter, which is provided. The checker provides, through a one- inch cathode -ray tube, a visual analy- when used in conjunction with radio sis of plate current. communication equipment on all types Checks which can be made on the can be used under adverse lighting con- of military and commercial mobile Universal include: Thyratrons -wave ditions or in total darkness when neces- vehicles and on boats. The manufac- form, break -down point in cycle, and sary. The specially processed steel turer states that its advantages are panel is treated with a non -radioactive that it permits a shorter or lower an- luminous paint that retains its maxi- tenna to be used without loss of oper- mum luminosity for several minutes ating efficiency, and it provides greater after exposure to ordinary light, and efficiency when it is the same height or can be observed for an hour or more length as would be a conventional type after that. The glow is of the same antenna. color and intensity as the standard The basic element of the antenna is medium persistence screen of the cath- its tuning coil assembly, which con- ode -ray tube used. The black -out panel sists of a weatherproof high Q coil en- is an optional feature in Type 208 closed in a metal shield. This is sur- oscillograph. mounted by a short whip. Flexibility of mounting is provided by a base stud, Multiplier Transformer by means of which the tuning coil assembly can be supported on a tubing A POWER TRANSFORMER designed for use or pipe of appropriate length. The as- with the RCA 931 electron multiplier sembly may also be supported on a tube by The Kenyon Transformer Co., base insulator and wire used in place of Inc., of 840 Barry St., Bronx, New the whip as the "radiator" portion of York, is known as type T -211. Primary the antenna. handles 0/105/115/125 volts at 60 cps. The tuning coil assembly provides an High voltage secondary delivers from accurate means of matching the trans- 100 to 1000 volts r.m.s. in steps of 100 mitter to the antenna at the operating volts at 10 ma. Low voltage secondary frequency. This resonant antenna supplies 2.5 volts at 1.75 amperes. Case tends to eliminate extensive power is Kenyon's standard 4A. 102 January 1942 - ELECTRONICS Adjustable Resistor Contact MICO POWER WIRE WOUNu RESISTORS of the adjustable variety above 25 watts, made by the International Resistance ENGRAVER Co. of 401 N. Broad St., Philadelphia, Pa., are now made with new contact bands designed to prevent breakage of wire by excess tightening and also to resist contact corrosion. Silver contact buttons are mounted on heat -resistant stainless steel springs spot -welded to the bands in such a manner that button pressure on the wire remains constant regardless of clamp tightening. The new bands may, if desired, be obtained separately in k, 2 and 1i -inch diameters.

For lettering panels of steel, aluminum, brass, or bakelite, or for marking finished apparatus. Cone Speaker Projectors

A sturdy machine for routine production A COMPLETELY NEW LINE of radial cone as well as occasional engraving. speaker projectors designed for uni- Attachments increase its versatility to form sound projection in all directions include large work on flat or curved surfaces. has been made available by University Excellent engraving can be produced by Laboratories, 195 Chrystie Street, New an inexperienced operator. York, N. Y. The model RBP radial projectors have pleasing appearance Catalogue on request and compact construction of the flat Prompt Delivery production; Priced from $115 with type UB- CONTRACTING speeds -everyone knows that. And, if you use transformers as an accessory or part of your product then by all means find out how Mico Instrument Co. Acme cooperation can help speed your production, give you a better product and 2m ARROW STREET probably show you savings in cost. CAMBRIDGE, MASS. ENGINEERING Transformer design is a spe- trans- SERVICE cialist's job. Acme former engineers are experts who can help you proportion the various ceiling type speakers and good tone transformer design factors into a unit to exactly meet the efficiency and performance quality. An "infinite baffle" sealed required. No need to burden yourself with acoustic chamber gives added bass re- the problem of transformer design. Just call sponse. Other features are: a flat top for an Acme engineer. design which is suitable for ceiling or DIES -TOOLS Acme has on hand, ready the single suspension mounting, the unit FIXTURES for immediate use, is waterproofed for outdoor use, it is necessary dies, fixtures and tools to produce transformers in a wide of all steel construction with "floating range of characteristics, designs and mount- rubber" speaker mounting and "non ings. Time delay and high costs for tools resonant" rubber rims. The instru- are eliminated if you can use Acme facilities. ment is especially useful for music re- were production in factories. It is available PRODUCTION Acme's three plants FACILITIES built exclusively for trans- for 12 and 8 inch cone speakers. former production. Com- pletely equipped with up -to- the -minute production equipment. Specially trained expert A Dependable craftsmen know how to make transformers better. These facilities are at your service. Armored Power Rheostat MINIATURE Can You Control Your Testing TO WITHSTAND exceptionally hard us- from 0 to 135 volts FREQUENCY METER age, particularly where units must be Voltage FOR POWER FREQUENCIES BE- exposed, an armored type power rheo- - 25 and in TWEEN 15 AND 500 CYCLES PER stat rated at watts available Every laboratory and most standard resistance values of from 1 lines of elec- SECOND production to 5000 ohms is made by Clarostat Mfg. tronic devices need an variable voltage Frahm Frequency Meters indicate by Co., Inc., 285 -7 N. 6th St., Brooklyn, adequate tester. The Acme Voltrol the resonant vibration of accurately N. Y. Mounted in a perforated metal provides all the features tuned steel reeds, which hold their orig- housing, the rheostat has flat lug you want. Built in panel inal calibration for a very long time. the of its casing, and portable styles. Write terminals at rear Acme Voltrol Bulletin. Simple. Rugged. Unaffected by wave while the front face has an ear or lock- for form or by ordinary voltage and tem- pin which in a hole in- perature changes. Wide range portable ing engages or and switchboard types also available. dentation in the panel or mounting surface, preventing the entire unit from The Acme Electric & Mfg. Co. Write for Bulletin 1695 -E turning when single -hole mounted. 31 Water St. Cuba, New York Winding is imbedded in an inorganic JAMES G BIDDLE CO. cement over an insulated metal core in I ELECTRICAL INSTRUMENTS such a way that maximum heat dis- 1211-13 Aeai STREET PHILADELPHIA. PA. sipation occurs even when just a portion of the winding is in use. ELECTRONICS - January 1942 103 Voltage Regulator THYRATRON TUBE CIRCUIT CONTROL of a motor- driven variable voltage auto - transformer is the operating principle used in a new line of "Seco" automatic voltage regulators manufactured by Superior Electric Company of 34 Har- rison St., Bristol, Conn. Regulators are available for use on 115, 230, or 440 volt circuits in capacities up to 75 kva., are designed to maintain a constant output voltage with variations in input voltage or load. Output voltage and sensitivity are adjustable over a wide range by means of controls on the front panel and regulators have the high efficiency and low exciting current char- Take no chances on relays for defense prod - THE NEW G -M RELAY TYPE "J" acteristics inherent with the variable ucts-or for regular products. There is no sub- voltage auto -transformer. Response is stitute for quality. 'Che Type "J" Relay is small, a full time compact, with extra power for rapid, with range travel of 6 seconds. Operation is not affected The new Type "J" Relay is designed to sur- such small size. 2 Pole or 3 Pole. Contacts have self- clean- by changes in power factor of load, nor pass. Engineered to meet severe require- ing "wiping" action. Relay does the regulator itself affect the ments, it designed to meet aircraft re- provides an even greater operating quirements as to humidity, power factor or waveform of the sys- margin for normal uses. temperature, and vibration tem to which it is attached. tests. Write for Bulletin No. 612

Miniature Terminal Bushings DEPEND ON .. . A NEW LINE OF MINIATURE terminal bushings, suitable for transformers, 00 condensers, and similar applications in the radio and electrical industries, has G-sf LABORATORIES INC. been placed on the market by Isolan- tite Inc., 233 Broadway, New York, 4313 NORTH KNOX AVE. CHICAGO, U. S.A. N. Y.

WIRE WODUD RESISTORS are more E1(!URATE and DEPEIIDABLE

Instrument Resistors Company produce and deliver better Wire Wound Resistors - faster.

The many advantages of Special Coils and Wire Wound Resistors by Instrument Resistors Co., frequently can be had at less expense than the units you now are using. Catalog upon request. (IIIIISTRUMERT RESISTORS (O., Little Falls, h. J. on, 0i Bushings are supplied complete with hard copper tinned terminals and 5;1, 0,07, nickel -plated copper flanges. Flanges may be spun or eyeleted into is -inch TAYLOR or thinner metal panels and cases, ac- LAMINATED PLASTICS cording to the manufacturer. Ter- minals are slotted to accommodate leads, Vulcanized Fibre Phenol Fibre or leads may be soldered into center eyelets of terminals if desired. Insula- SHEETS, RODS, TUBES, FABRICATED PARTS tor bodies are of glazed Isolantite. Bushings are supplied in two terminal TAYLOR FIBRE COMPANY lengths and two insulator lengths, mak- Norristown, Pennsylvania ing a total of four combinations. Full ilk details of construction are given in Bulletin No. 104 -A, available from the manufacturer. 104 January 1942 - ELECTRONICS U -H -F Transmitting Capacitor ENGINEERED and designed for use in ultrahigh- frequency radio transmit- Bliley ters, television and FM transmitters, ITS as well as in miscellaneous applications in the u -h -f range, a new Type CRYSTAL. 1860 transmitting capacitor is available from Aerovox Corporation of New Bedford, Mass. In such applications

BLILEY precision -made Crystal Units are supplied for all frequencies from 20Kc. to 30Mc. Catelog G -12 contains .complete information. this capacitor is adaptable for use as a fixed tuning capacitor, for by- passing, BLILEY ELECTRIC COMPANY blocking, coupling and neutralizing, and UNION STATION BUILDING ERIE, PA. as an antenna series capacitor. Losses are low because of a highly refined sul- phur compound utilized as the dielectric, by the elimination of corona and by design and construction. The case \\ is grounded and a single high- tension mica -insulated brass terminal is used. The aluminum case measures approxi- o6an. ic mately 2x2¡ inches, and is provided with a mounting base with 2 holes for 10 -32 screws. The capacitor is avail- is used as a cathode n Mercury Vapor able in .00001 and .000025 µf in 10,000 volts and .00005 µf in 5,000 volts. Rectifiers meeting the specifications of the U. S. Navy.

Universal Bridge ( WILBUR B. DRIVER CO. NEW INSTRUMENT by Shallcross Mfg. NEWARK, NEW JERSEY Co. of Collingdale, Penna., is a combination Wheatstone and Kelvin bridge, model 638 -1. It has an effective measurement range from as low as 0.0001 ohm to as high as 11,000,000 ohms and, by using a source of current of considerable capacity such as the single PERMANENT MAGNE?! cell of a storage battery, will detect ALL SHAPES - ALL SIZES and measure as low as 0.00001 ohm. FOR ALL PURPOSES The rheostat arm consists of four de- cades, variable in 1 ohm increments. Stamped, Formed, and Cast; Chrome, Tung- Ratio arm has two sets of multipliers, sten Cobalt and ALNICO ** (cast or sin- one set designated W for use in tered) under G. E. license. Wheatstone bridge measurements, the other designated K for use with the THOMAS & SKINNER Kelvin measurement method. Built -in STEEL PRODUCTS COMPANY galvanometer having a deflection of 1 1115 E. 23rd STREET INDIANAPOLIS, INDIANA mm microampere is an integral part Laminations Transformers Tools of the set. Instrument is furnished for Radio - complete with all binding posts neces- Dies - Heat Treat ng - Stampings sary for connection of resistances to be measured and batteries. 40 YEARS EXPERIENCE

ELECTRONICS January 1942 To Serve Well the Metal Duplicating System Microphotometer Professional Radioman SMALL METAL PARTS may be made in A RAPID AND CONVENIENT METHOD for limited quantities without dies with Di- analyzing spectrographic plates or Acro benders, brakes and shears. films in research and industrial labor- These precision machines are accurate atories is provided by a new recording to 0.001 inches. microphotometer announced by Leeds & The illustration shows three typical Northrup Company, 4934 Stenton Ave., steps in this process. First, the man at Philadelphia, Pa. Plates or films are me- the right is cutting strips from a stock chanically scanned by a motor -driven sheet to the required size with the scanning unit and the relative positions shear. Second, the operator in the and densities of spectrum lines are center is forming a channel from the automatically recorded by an L &N accurately sized strip with the brake. Speedomax recorder. Pen and ink records of standard and test spectro- grams are drawn at high speed on one chart. Designed to accommodate plates or films as large as 4 inches high by 10 inches wide, the scanning unit includes on a heavy cast base an optical system, a plate stage, a drive mechanism for the plate stage, an a -c operated amplifier and all necessary controls. A Self- Defense Conductivity Cell Program ELECTROLYTE CONDUCTIVITY may be Third, the man at the left is putting a accurately determined through the use bend on each end of the channel with of a new fill -type conductivity cell the bender. with a constant of approximately 15, that began in 1927 All three machines are adapted for made available by Industrial Instru- either right or left hand operation. ments, Inc., 156 Culver Ave., Jersey They are available from O'Neil -Irwin For 15 years CREI has helped City, N. J. Known as type CEL -3, the Manufacturing Company, located at cell is of resistance glass construction equip engineers with the tech- 321 8th Avenue South, Minneapolis, with platinum electrodes. It is used nical ability to advance to Minn. by placing the electrolyte in the body of better positions the cell proper, connecting to the conductivity bridge by means of mercury Important to ambitious men, before, dur- Molded Magnetic Cores placed in the connecting bulbs on each ing and long after any temporary emergency, end, with connecting wires dipping is a planned program of study that enables them to step ahead into better positions with DESIGNED FOR ELECTRICAL, radio and into mercury pools. A thermometer, increased pay. This is a "self- defense" pro- high frequency use are new molded supplied, may be inserted in the elec- gram for advancement that provides a secure future and lasting career. magnetic cores offered by The Ferro - trolyte for temperature readings. cart Corp. of America, Hastings -On-

CREI was founded for that purpose . .. to Hudson, N. Y. Typical cores include enable alert professional radiomen to acquire small pot types 0.485 inches outside the necessary ability through modern technical training, which enables them to go after diameter by 0.400 inside diameter and the better engineering positions -and get 0.215 high. Center core is 0.158 inch Fine Adjustment Rheostats them. in diameter and 0,125 inch high. When REX RHEOSTAT COMPANY, 37 West 20th Since 1927, CREI has been training radio- the two are placed together a com- Street, New York, N. Y., announce men and providing them with such a planned pletely inclosed winding space is pro- Fine Adjustment rheostats which en- "Self- defense" program. Our successful 0.250 0.120 record during these 15 years is created vided, inch long and inch able any value of the current or voltage by the accomplishments of our graduates. high, may, for example, be used in the to be set as closely as possible within Hundreds of unsolicited letters in our gain 455 kc i -f files testify to the fact that CREI train- construction of high the controlling range of the rheostat. ing has been helpful in gaining better transformers of small size such as The smallest possible adjustment is positions at higher pay in minimum time. those employed in camera -type port- Few other educational institutions have so from one turn of the resistance winding fully gained the respect and confidence of able radios. Closed pots with movable to the next, whether performed by the men of the radio industry. CREI center screw cores are also being pro- courses have PROVEN their worth -they hand or through means of a vernier are recognized by employees and employers duced. drive or similar device. The degree of alike as the finest possible instructions at the lowest possible cost. Ask any radio resulting variation depends upon the engineer! ohmic value of this one turn of the Concentric Disc Resistors winding in relation to the ohmic value Why not investigate what CREI spare of the whole circuit. As more resistance time training in Practical Radio Engi- CONCENTRIC DISC RESISTORS, now being of the rheostat is placed in the circuit, neering can do for you or your asso- supplied by International Resistance the finer the adjustment of the current ciates? Let us send our interesting Company, 401 North Broad Street, becomes, and vice versa. This effect booklet together with personal rec- Pa., designed for en- almost the ommendations for your advancement Philadelphia, are can be achieved over entire in radio through a planned program gineers faced with the problem of get- regulating range of the rheostat. Two of technical training. ting pure resistance loading of low windings are arranged on the same power concentric transmission lines. tube; the wire of one winding for The resistors are available in a variety these rheostats has about five times CAPITOL RADIO of sizes and resistance values. They the cross section area of the other wind- ENGINEERING INSTITUTE have a minimum of inductance and ing serving for coarse adjustment. should prove useful in E. H. Rietzke, President capacity and Through this method each turn of the h -f measurement circuits, signal gen- coarse adjustment is divided into ap- Dept. E -1, 3224 - 16th St., N.W. erating equipment and u -h -f devices proximately five equal steps at the fine Washington, D. C. now under development. adjustment.

106 January 1942-ELECTRONICS Fullwave Variable ried through the skirt to the insulated, gas- sealed and weather- protected junc- CREW Transformer tion between the two furnished as part of the LATEST ADDITION to the line of "Vari- setup. Maximum radiated pow- tran" variable voltage transformers er in the ground plane plus simplicity made by United Transformer Corp. of and neatness of radiator installation are noted The 150 Varick St., New York, is a full - features. antennas are wave type designed for use with low suitable for either transmission or re- voltage rectifiers such as those em- ception. ployed in plating processes, battery FOR TRIPLETT CUSTOMERS ONLY charging and other similar applications. The new device obviates the Long before the state of emergency necessity for a separate step -down Flashlight Battery was proclaimed, the Triplett Company transformer in such cases, since it has was getting ready to do its part in build- an insulated secondary provided with A FLASHLIGHT BATTERY which can be two contact arms moving in opposite recharged is available from Ideal Com- ing our national security. We knew that directions each side of the center tap. mutator Dresser Company, 1273 Park we must meet important new responsi- Avenue, Sycamore, Ill. Its main ad- bilities. At the same time, we felt keenly vantages are 1,000 hours or more of bright light with proper care; occa- our continuing obligations to our cus- Lumarith Protectoid Tubing sional charging at convenient periods tomers -old friends with whom we have and the addition of distilled water is all TUBING USEFUL TO THE in- had happy business relations through A electrical the care required; by extensive re- dustry has been developed by Precision search, spillage and creeping corrosion many years. Paper Tube Company, 2033 West have been eliminated; it is easy to add We doubled -then tripled -our out- Charleston Street, Chicago, Ill., it is the distilled water; special light bulbs announced by Celluloid Corporation with lower voltage rating are used to put to fill the needs of our old accounts. New York, N. (180 Madison Avenue, give a more piercing light (both screw We added to our production facilities Y.) manufacturers of the cellulose ace- base and flanged fixed focus lamps are tate (Lumarith Protectoid is the trade . . . hired many more men . . . are available) ; a -c chargers a variety in making with name of the product) used of voltages and frequencies, d-c working extra shifts at time -and -a -half. the tubing. Spiral wound Lumarith chargers and automobile charger clips All this has not been enough. have Protectoid is available in round, oval make recharging convenient. We been called on to produce more and more for national defense. We are proud of the job we are doing to help meet the Electronic Motor Control emergency, but it is difficult not to be to serve DESCRIBED IN BULLETIN No. GED -927A, able our old friends equally as available from General Electric Com- well. In the face of these conditions, the pany, Schenectady, N. Y., is a new Triplett Company has adopted these pol- electronic control system known as icies Thy- mo -trol. The system employs elec- "for the duration." tron tubes to convert alternating cur- First: We will continue to serve you by our service to our mutual responsibility the national emergency. - and square shapes, is produced from 116 Second: We will inch to 3 inch (inside diameter) in continue to do everything we can to fill orders from varying wall thicknesses, and in con- our regular customers, even tinuous lengths that can be cut to re- though some deliveries may be quired sizes as it emerges from the temporarily delayed. No busi- winder. Besides clear transparent, the ness from new accounts has tubing is also available with a paper been nor will be accepted un- or fiber base with an outside layer of til after our old friends have Lumarith Protectoid. The electrical been served, except where pri- properties of this new acetate make it orities make it impossible to useful for cores for speaker field coils, do so. in bobbins, for random wound ignition Third: Our engineering and research coils, spaghetti insulation for wire, pro- departments will continue to tection for especially delicate metal work on the development of such as micrometer handles, etc. superior equipment and im- parts proved methods to serve you still better when we can re- sume normal operations. Coaxial Vertical Antenna The present emergency is incidental HALF -WAVE VERTICAL ANTENNA Cut to and as we work towards the future, we specification for ultrahigh frequencies will do our best to continue to merit between 30 and 200 Mc., for use with your confidence and loyalty. concentric transmission lines and re- rent to controlled direct current thus quiring no matching network or tuning providing variable armature and field are now available from the Wunderlich voltages for operating a d -c motor. The Radio Company, 1337 Fargo Ave., Chi- system not only provides stepless, wide - ,22°.? cago. Radiators consist of a /-wave range speed control, but also performs President "whip" constituting the upper section, additional functions of starting, ac- insulated from a i -wave "skirt" con- celerating, protecting and stopping. The Triplett Electrical Instrument Company stituting the lower section, with a short Standard units are designed to cover Manufacturers of section of I -inch concentric f'eder car- motor sizes up to 5 hp at 230 volts. Precision Electrical Instruments ELECTRONICS - January 1942 107 Carbon Resistors

THE KEYSTONE CARBON COMPANY, 1935 for State Street, St. Marys, Pa. announce that its line of negative temperature RESEARCH coefficient resistors are now available with metal coatings for making electrical connections, instead of the DESIGN moulded -in wires previously available. PRODUCTION Magnetic Oscilloscope A MAGNETIC OSCILLOSCOPE, which is a new peak- reading portable instrument, has been announced by General Elec- tric Company, Schenectady, N. Y. The USE instrument was developed primarily for use in resistance welding, but it may be applied as a supplement to other instruments used in trouble shoot- FERRIS ing and in making installation adjust - ment, and can be used in checking op- INSTRUMENTS eration of electronic controls, voltage MICROVOLTERS' regulation measurements, current measurements made with pointer-stop STANDARD SIGNAL GENERATORS instruments, etc. ULTRA HIGH FREQUENCY SIGNAL GENERATORS CRYSTAL CONTROLLED SIGNAL GENERATORS RADIO NOISE METERS Write for new catalog E -4; illustrates and gives complete details and specifications for the complete line of Ferris instruments. FERRIS INSTRUMENT CORPORATION BOONTON Telephone Boonton 8 -0781 NEW JERSEY 'Reg. U. S. Pat. Office

FAMOUS The oscilloscope has a high -speed re- for years .... sponse to both current and voltage, for their uniform accuracy made possible by the use of a per- and great strength . . manent- magnet type of oscillograph for the unique self -locking Magnitude, symmetry, feature on the "Unbrako' galvanometer. Hollow Set Screw with the and uniformity of current wave are re- Knurled Points ... for the the length, position, Socket Head Cap Screw vealed quickly by with the Knurled Head and uniformity of a horizontal trace REG U.S_ Par. op FICE that gears right to the on the ground -glass viewing fingers and saves assem- of light A narrow light beam from an SCREW bling time. screen. "Unbrako" Products are internal lamp impinges upon the tiny PRODUCTS available in a complete range of sizes from num- galvanometer mirror, the movements ber 4 up. For free samples of which are reflected to the viewing and literature, write today. screen. The instrument requires no KNURLING of S o c k e t STANDARD PRESSED STEEL CO. Screws originated with reset time. A quick change from poten- Bo: 596. JENKINTOWN. PENNA. "UNBRAKO" years ago. tial to current measurement is accomplished by turning a switch on the front of the box. The instrument is almost entirely free from magnetic NO ENGINEER field interference. whose work takes him into the field of sensitive electrical Mass Spectrometer devices can say- today -that he is thoroughly grounded EXHIBITED RECENTLY at the Exposition unless he "knows his electronics." of Chemical Industries was a new port- Because electronic circuits more and more are getting able mass spectrometer for gas analysis and continuous process control into industrial work as an automatic hand, an automatic work. This is a new product of West- eye, a new means of generating heat, etc., etc., they have inghouse Electric and Mfg. Co., East become the background for a new cycle of industrial Pittsburgh, Pa. Essentially a high vacuum tube in which the gas to be progress. studied is admitted under a pressure of Are you trying to get along without ELECTRONICS? 10-' mm of mercury and ionized by an Better subscribe today! electron beam, the spectrometer is capable of measuring as little as 0.001 percent oxygen in nitrogen. 108 January 1942 - ELECTRONICS Literature Ifyour need for instruments is essential enough Radio Noise Suppressors. Catalog 12 -F describes "EIim -O -Stat "radio noise suppressors manufactured by Solar Mfg. to give you the right to buy, Company, Bayonne, N. J. Three different types of suppressors are de- it is enough to rate scribed: Types R are for use with re- essential ceivers and also with appliances; Types A are for use with appliances only; the best. and the others are miscellaneous types.

Selenium Rectifiers. A 16 -page book- To those who have searched let available from International Tele- phone & Radio Mfg. Company (67 out the facts, best means Broad Street, New York, N. Y.) is devoted to selenium rectifiers for use where direct current is required from Simpson! an a-c source, from milliwatts to kilo- watts. SIMPSON ELECTRIC COMPANY Capacitor Analyzers. Six different 5212 Kinzie St., Chicago, Ill. types of capacitor analyzers are described in Catalog 12 -G available from Solar Mfg. Company, Bayonne, N. J. Some replacement parts and optional accessories for analyzers are also listed.

Aircraft Receiver. Available from RCA Manufacturing Company, Camden, N. J. is a bulletin which describes Model AVR -100 beacon and broadcast band receiver, and Model AVP. -101 beacon band receiver. Both receivers are for light planes. e New York's Largest Available Stock of Transformer Case Specs. A new folder prepared by Acme Electric of Cuba, N. Y., contains line- drawings showing RADIO and ELECTRONIC EQUIPMENT the physical sizes, shapes and mounting arrangements of transformer cases At Our NEW ADDRESS recommended by this firm to manufacturers ordering special units for radio, television, control, industrial and 85 CORTLANDT STREET other applications. FOR BETTER SERVICE fo our Visit our new, modern home patrons, under present condi- and see the very latest innova- Ceramic Insulation. American Lava Corporation, Chattanooga, Tenn., have tions, we have consolidated our tions in radio merchandising. available a reprint which contains large stocks of radio parts and See for yourself the tremen- previously unpublished material on the equipment from our two New dous stock under one roof. And electrical properties of high frequency York Stores into one huge new be convinced that here is your ceramics. This material has been re- shop at 85 Cortlandf Street- most dependable service of printed from Electronic Engineering, 12,000 square febt on one supply in the radio field. a British publicatien. great floor. This move will enable us to furnish prompt and For your convenience we are Radio Tube Handbook. National Un- complete deliveries of essen- maintaining an uptown store ion Radio Corp., 1181 McCarter High- tial merchandise, and at the for radio sets, phonographs way, Newark, N. J., have issued a new same time enable us to coop- and records only at 70 West radio tube handbook which supplements erate in the National Effort 45th Street under the manage- their engineering data book. It costs most effectively. ment of Jack Haizen. ten cents, and contains information on over 600 tube types. Make Terminal your headquarters for everything in radio.

Erratum. It was announced in the November issue that a new catalog on precision metal shielded wire was avail- TERMINAL RADIO CORP. M1110111" able from Precision Tools Company. This should have read Precision Tube 85 CORTLANDT ST. NEW YORK CITY Company, 3824 Terrace Street, Phila- TELEPHONE: WOrth 2 -4416 delphia, Pa. ELECTRONICS - January 1942 109 Common Misapplications (Continued from page 46) PROFESSIONAL 3. A decrease in arc -back rate is be negative with respect to the often found after a period of "sea- cathode. SERVICES soning" or operation. One example of this is shown in The first two affect the building - Fig. 2 -a, where the grid potential up of the incipient arc -back to a is alternating and the firing point I Rates on Application) stable form and the third indicates is determined by shifting the phase the removal of the causes or patches. of the grid potential with respect to The above rather sketchily out- the anode potential. lined theory again shows how the It will be noticed that when the peak inverse voltage may not be the tube is caused to fire late, the grid F. ALEXANDER, E. E. only factor defining the difficulty of potential may be positive and thus High Vacuum Laboratory, Special Lamps and a duty imposed on a given tube. A Tubes, Rare Gases, Fluorescence, Special Glass be producing ionization in the tube Apparatuses, Quartz, Pyrex, etc. Metal to Glass rating to cover this phenomonon has at the very time when the tube Seals, Graded Seals, Quartz to Pyrex or Soft not as yet been glass, Consulting. devised. It would should be deionized, and, in a con- 115 West 23d St., New York have to define and limit the rate of dition to withstand reverse voltage. rise and the magnitude of the cur- This increases the probability of rent which the circuit can deliver occurance of arc -back, especially on JOHN C. BATCHELOR to an arc -back. INDUSTRIAL PHYSICISTS -ENGINEERS the high voltage circuits. A con- Preparation and Supervision of Research Since these quantities are not ventional method of preventing arc - Programs to develop and improve products and applications for postwar manu- directly connected with any of the back is to employ a large enough facture and marketing. functions the tube performs when value of grid resistance to limit the 100 E. 42nd Street New York City operating properly, they are difficult amount of ionization on positive grid to define by a tube rating. swings. This is far from a satisfac- The problem INTERNATIONAL ELECTRONICS, INC. is usually solved by tory method, however, and usually Special Instruments, Equipment and Methods to making the rating tests in the type control gauging, welding, heating, communications, results in the use of much higher signaling, safety, inspection. color and testing. of service in which the tube finds grid resistance than would Quality control and cost reduction for mechanical, normally electrical, metallurgical and chemical industries. its most popular use. For this rea- be necessary. Rockefeller Center New York City son, is Telephone CIrcle 6-8494 it desirable for the intended Another method is to connect a user of the tube in an unconventional copper oxide rectifier in the circuit circuit to confer with the tube manu- HAROLD J. McCREARY as shown in Fig. 3. This prevents Mem. A.I.E.E. & W.S.E. facturer before making a final choice the grid going positive with respect Consulting Engineer Laboratory Facilities of a tube. to the cathode, but at the same time Research Electronics Development Television permits the use of a grid swing of Design Radio Influence of Grid Circuit on Factory Practice Railroads Signaling high magnitude. The result is more Patent Studies Telephony Thyratron Stability 105 W. Adams St. Phone STate 4003 Chicago. III. precise control. There have been a number of ap- The best way to prevent arc -backs JOSEPH RAZEK, PH.D. plications where trouble due to due to ionization from positive grid Consulting Physicist erratic thyratron operation has been current is to use a peaked wave Electrical and Mechanical Engineering Problems Instruments and Control Devices Electronics reported. In a large percentage of transformer which makes the grid Specialist in Colorimetry, Spectophotometry and Industrial Color Control cases, especially where extremely potential positive for only a small Laboratory and Shop Facilities low grid 430 Greenview Lane Llanerch, Pa. power was not a factor, fraction of a cycle. This potential very reliable operation has been should preferably be superimposed secured simply by alteration of cir- on a fixed negative d -c bias. In this J. ALBERT STOBBE cuits or circuit constants. case, conditions are as shown in Fig. Consultant for establishing new enter- Very often, too high a positive 2 -b. Here the grid potential is posi- prises and evaluating or improving existing manufacturing, scientific or mer- potential is applied to the grid of a tive only when the tube is passing chandising situations. thyratron. The ratings usually call current and no grid produced ioniza- 03 Wall Street New York City for maximum grid potentials of tion is present in the tube when the about 12 volts. This is intended to anode is negative. prevent the grid assuming the role Certain circuits, especially those CONSULT of an anode and drawing currents employing high values of grid re- from the cathode. In THESE small size sistance show a lack of stability. An tubes, this additional current may explanation of one of the common SPECIALISTS: be an appreciable percentage of the causes of instability follows: total cathode current resulting in In Fig. 4 -a a circuit is Let them save your time thyratron cathode overloading. Another effect shown ; Fig. 4 -b shows schematically by bringing their broad is that of increased grid temperature the equivalent grid to anode capacity experience in their spe- which may result in loss of control. Cp, and the grid to cathode capacity ciality to bear on your The most serious effect, however is C,,. In parallel with C5, is the bias- problems. that it permits ionization within the ing voltage E,. In series with the tube at a time when the anode may grid resistor R,. If the anode cath- 110 January 1942 - ELECTRONICS ode voltage E, should increase with tion, is desirable from the stand- NOW a steep wave front, the voltage e, point of more complete utilization of the grid tends also to increase. of the complete cathode surface. This tendency is opposed by the bat- This results in increased life, es- a really high -powered tery voltage. If the resistance in the pecially with d -c anode supply. For grid circuit is too high the effect of a -c anode supply, an approximate RADIO the battery is minimized and the quarter -phase relationship between grid voltage may momentarily rise anode and cathode supplies is the to a high enough value to cause ideal. In practice, this is seldom ENGINEERING breakdown. used, except for comparatively large The obvious cure is to reduce the tubes. LIBRARY value of grid resistance to a mini- At times, an attempt is made to mum consistent with the published operate a thyratron at characteris- grid current rating. Such a cure is tic values of anode potential requir- applicable, however, only in the fol- ing very low values of grid bias. lowing types of application : (1) Study of Fig. 5 will show that with where limitations in grid driving a tube using a directly heated cath- power do not dictate the value of ode and centertap return, it is never grid resistance, and (2) where means advisable to operate with a negative Note: are used to prevent high positive grid bias which is less than 0.7 E,. The Library comprises 5, it will be seen that as a selection of books grid swings. From Fig. culled from leading low value of grid soon as the bias voltage is reduced McGraw -Hill publica- In addition to a tions in the radio resistance, a condenser should be to a value less than half the peak field. connected between grid and cathode. cathode potential, the grid circuit This condenser serves to by -pass acts like miniature full -wave recti- especially selected by radio specialists of transient grid currents. The value fier. McGraw -Hill publications of capacity employed should be as When the filament phase is such to give most complete, dependable coverage of facts needed by all whose melds large as possible, the exact capacity that the end a is positive with respect are rounded on radio fundamentals being determined by the particular to the center tap o current flows available at a special price and terms circuit requirements. through R, in the direction shown. While these suggestions to im- When the end b is positive, the cur- These books cover circuit phenomena, tube R, in the theory, networks, measurements, and other prove stability are not possible in rent flows again through subjects -give specialized treatments of all The result is a full fields of practical design and application. They certain applications, there are a same direction. are books of recognized position in the litera- current flowing in the ture -books you will refer to and be referred large number of installations where wave rectified to often. If you are a practical designer, re- resistance which biases the grid searcher or engineer in any field based on radio, more than sufficient grid power is grid you want these books for the help they give in negatively thus requiring the addi- hundreds of problems throughout the whole available, and the operating fre- field of radio engineering. quency is low enough to allow the tion of more positive bias. The mag- use of a large value of grid by -pass nitude of this bias depends on the 5 volumes, 3559 pages, 2558 illustrations capacity. potentials involved, the value of grid Eastman's FUNDAMENTALS OF VACUUM TUBES, 2nd edition values of resistance, and the emissivity of the Where extremely high Terman's RADIO ENGINEERING, 2nd grid resistance are necessary and cathode, especially near the end sec- edition no by-pass capacity is permissible, tions. The result of the developed Everitt's COMMUNICATION ENGI- the use of a shield grid thyratron grid potential is a flattening out of NEERING, 2nd edition is suggested. the characteristic curve at values of Hund's HIGH FREQUENCY MEASURE- value of 0.7 MENTS bias less than the critical Henney's RADIO ENGINEERING HAND- Influence of Cathode Return E, described. The nature of the effect BOOK, 3rd edition of charac- Circuits (Direct Heated Cathodes) is to make this portion the SPECIAL LOW PRICE EASY TERMS teristic curve, (i. e., the flat portion) Special price under thin offer lees than cost of books bought separately. In addition, you The grid biasing effect due to the unstable. Furthermore, individual have the privilege of paying in easy install- is ments beginning with $3.00 in 10 days after cathode potential often overlooked tubes may vary considerably in bias receipt of books, and $3.00 monthly thereafter. in the application of a thyratron. Already these books are recognized as standard characteristic and starting potential, works that You are bound to require sooner or This effect may be demonstrated by later. Take advantage of these convenient at values below this critical value. terms to add them to your library now. the following experiment. Consider FOR 10 DAYS EXAMINATION SEND THIS first, the effect produced by the Influence of Cathode Return Cir- + ON- APPROVAL COUPON' cathode potential with the anode cuits (Indirect Heated Cathodes) and grid returned to one side of the MoGraw -Hill Book Co., 330 W. 42nd St., N. Y. Send me Radio Engineering Library for 10 days' cathode. Assume the anode phase Tubes employing indirectly heated examination on approval. In 10 days I will send $3,00 plus few cents postage, and $3.00 monthly till of a cathodes should have the anode and $24 is paid, or return books postpaid. (We pay and filament phase given polar- postage on orders accompanied by remittance of ity. A certain value of critical grid grid returns made directly to the first installment.) bias is determined. Now, if the cathode. This statement seems al- Name cathode phase is reversed, the bias most superfluous, yet it is surprising Address value changes by a value approxi- how many instances have occurred City and State mately equal to the cathode poten- where the effects of improper re- Position tial. Connection to the center tap turns were either not known or dis- Company L 1 -42 in U.S. and Canada only.) minimizes this effect, and, in addi- regarded. (Books sent on approval ELECTRONICS - January 1942 111

The most common practice in in- to the cathode. 4. Don't subject the bulb or con- directly heated cathode design is to Practically all gaseous conduction nection to strain. Use flexible con- connect one side of the heater in- tubes employ glass in one form or nectors and holders. ternally to the cathode. If the cath- another. The use of glass does not 5. Don't operate a newly installed ode returns are made to the opposite necessarily greatly impair the abil- hot cathode mercury tube heater until the leg or to the transformer ity of a device employing such ma- mercury has been driven from centertap, the the following effects may terial from withstanding shock. upper section by cathode heating. be experienced: Precautions must be exercised to 6. Always operate a mercury - 1. Change in bias potential by as prevent subjecting the glass parts filled tube base down. ± much as, 1.4 E,. This change is to undue shock or strain. 7. If the tube temperature is not apparent when the phase of either controlled, permit a free circulation the anode or cathode is altered. The Incorrect Mechanical of air around the tube. effect is largest when the return is The impression, which may be left made to Design of Equipment the free heater leg. after reading this paper, is that 2. When Common the grid bias is reduced sense is probably the best electronic tubes are unreliable, to a value less guide in installing than 1.4 Ef, high grid tubes, yet there cranky and difficult to apply. How- current have been may occur as the grid actu- a number of cases where ever, the real purpose of the paper ally assumes even that was disregarded. a positive potential with is to show that with the proper con- respect to the A list of don'ts will be cathode. given as a sideration of the many factors in- 3. Possibility guide of heater burnout, to insure against loss of tubes volved in applying an electronic especially through mechanical in multitube circuits of difficulties. tube, excellent tube life and satis- large capacity. The anode current, 1. Don't mount the tube and socket factory performance can be obtained. especially during surges having a without cushioning if the tube is It is felt that a good many equip- steep wave front, tends to flow subjected to shock or vibration. ment designers and users, have not through the heater'to return to the 2. Don't clamp the base of the tube considered all of the factors which cathode. This current may add to unless it is clamped at a point near make for good tube life and depend- the normal heater current to such a the bottom of the base. Use a mini- ability. The hope is expressed, that degree that the additional tempera- mum of clamping pressure. bringing definite examples of im- ture resulting causes burnout. 3. Don't allow extremely hot or proper application to the fore, may The cure for these troubles is to cold substances to come in contact result in a general improvement of connect the grid and anode returns with glass parts. tube performance in the field.

Wanted Transmitting Tube Engineer SEARCHLIGHT SECTION Classified Advertisinp) A REAL OPPORTUNITY EMPLBOYMENT A man with these qualifications: IN : ,sOPPORTUNITIES1e : U:EQUIPMENTOR RESALE Complete knowledge of all phases UNDISPLAYED RATES- DISPLAYED of advanced 10 CENTS a Woap. MINIMUM CHARGE $2.00- Individual Spaces engineering with border rules for -re- Positions Wanted (full or part time salaried prominent search design methods employment display of advertisements. - - - only) lh the above rates The advertising rate is $6.00 per inch for payable on all types of transmitting and in advance, all advertising appearing on other than Boo Numbers-Care of publication New a contract basis. Contract rates quoted electronic radio tubes. York, Chicago or San Francisco offices on request. count as 10 words. An advertising inch is measured rk" ver- Send in your qualifications. Discount of 10 % if full payment is made tically on a column columns We in advance for 4 consecutive insertions. inches -3 -30 want one of the best men in the in- to a page. dustry for a permanent position with a great opportunity. All cor- HIGH respondence will be treated confi- GRADE USED DEPENDABLE dentially. ELECTRON TUBE MACHINERY Used Huge Stock of Every Type and Variety ELECTRONIC TUBE EQUIPMENT KAHLE ENGINEERING CORPORATION Complete line of used equipment for the manufac- TAYLOR TUBES, INC. ture of Radio Tubes, Neon Tubes, Incandescent Specialists in Equipment for the manufacture of Lamps, etc. Write for Bulletin showing 25 to 75% 2341 Wabansia Ave. Chicago, III. Neon Tubes, Radio Tubes, Incandescent Lamps, Photo Cells, X-ray Tubes, etc. CALCITE TUNGSTEN CORPORATION 900 DeMott St., North Bergen, N. J. formerly Eisler Electric Corp. 534 39th Street, Union City, N. I. POSITIONS VACANT POSITIONS WANTED BEST QUALITY, ELECTRONIC ENGINEER young man under POSITION WANTED: Young married man. USED 35 as research and design engineer with B.S. in Physics and Engineering; Harvard ELECTRON TUBE MACHINERY Vacuum Tube hearing aid company, M.S. Communication Engineering. Undergrad- must be uate experience includes physics Equipment for the manufacture of all kinds of graduated EE with some electronic and acous- laboratory electron tical experience desirable. Unusual oppor- assistantship, foremanship of electrical instru- tubes, radio tubes, incandescent lamps, tunity to progress with ments room of well known radio company. neon tubes, photo electric cells, X-ray tubes, etc. company. Compen- Development engineer on ultra high frequency sation secondary to proveable ability. Give project. age, complete education, experience and tele- Now Physics Instructor at Antioch AMERICAN ELECTRICAL SALES CO., INC. phone number. College until February 7, 1942. Available then. 65 -67 East Present staff know of this Address Box 133, Yellow 8th St. New York, N. Y. opening. Apply in complete confidence. P -296, Springs, Ohio. 6,1 Electronics 330 W. 42nd St., New York, N. Y. MAN 37 with 11 years experience in Sound and Radio engineering desires change in position. New England or New York City district only. PW -308, Electronics, 330 W. NEW "SEARCHLIGHT" ADVERTISEMENTS 42nd St., New York, N. Y. RADIO ENGINEERS wanted for development received by January 26th appear in the and design of radio transmitter components February issue, subject to space limitations. and directional antenna equipment. WANTED Trans- Address copy to the mitter experience desirable although not neces- ANYTHING within reason that is wanted in sary. Permanent positions. Describe educa- the field served by Electronics can be quickly Departmental Staff tion, experience, Aptitudes and state salary de- located through bringing it to the attention of ELECTRONICS sired. Recent photo requested. E. F. John- thousands of men whose interest is assured 330 West 42nd St., New York City son Company, Waseca, Minnesota. because this is the business paper they read. 112 January 1942 - ELECTRONICS /,/ v0/Az NEON ÄM PILOT -LIGHT

t u qhnpu,l l 1 m q nq 01 II q ' RECEPTACLES I. designed especially 14ICFiIIIIRIT H'IG1IIilEIIIIIIhiIFìIIIIIE;ICITdR;,10Nlll,lh;sl111l Three different units for use with G.E. Neon Glow Lamps, types S14, G10 and T41/2. All for single hole mounting. . panel . S G1OP Unii Overall Dia. 2" Overall Depth Behind Panel z#7/07 13/4"

Uses I or IYo" Watt Lamp on 120 V. I Watt Lamp on 220 V.

Secure IT BENDS EVERYTHING! Catalogue It's the "DI -ACRO" Bender No. 1, which together with "DI -ACRO" Brake and Shear turn out small Distributed Nationally By quantities of metal parts in a hurry -"Metal Dupli- cating without Dies'. GRAYBAR ELECTRIC CO. "DI -ACRO" Bender works wonders with Angles - H. R. KIRKLAND CO. MORRISTOWN, N. J. - Channel -Bod -Round or Square Tube -Round, Half TOP VIEW Round, Square or Flat Wire and Strip Stock. TWO - WAY OPERATION -right or left. Its a money saving die substitute. 1 Write for Catalog INSURANCE "Metal Duplicating SIDE VIEW °DIE accua '1x TOM Without Dies" Your money buys more at t/1 ona Terminal, It buys insurance 321 8th Ave. S., -insurance that you get the O'NEIL -IRWIN MFG. CO. Minneapolis, Minn. eISfc MACV'N' maximum in value and service, for Terminal is a reliable source of supply! We manufacture a complete line of equipment SPOT WELDERS. electric, from t/4 to 500 KVA AC ARC TERMINAL RADIO CORP. TRANSFORMERS, special and standard types WELDERS INCANDESCENT LAMP manufacturing equipment From 100 to 2 Stores in New York City FLUORESCENT TUBE MAKING EQUIPMENT 400 Amps. ELECTRONIC EQUII'bIENT, vacuum pumps. etc. 68 WEST 45TH STREET WET GLASS slicing and cutting machines for laboratory use BO CORTLANDT STREET GENERAL GLASS working machines and burners COLLEGE GLASS wo king units for students and laboratory Phone VAnderbilt 6-5050 EISLER ENGINEERING CO. e 751 So. 13th St. (near Avon A e.) Newark, New Jersey

RADIO LAB'S, Inc. HM Manufacturers of IECTROVitreous Enaneled HARVEY Radio Transmitters SOUND SYSTEMS RESISTORS for A complete range, from 1 to 200 ELECTRONIC APPARATUS W. wound with highest grade re. NATIONAL DEFENSE distance wire. Tolerances plus or Ave., Cambridge, Mass. require minus 5% (closer tolerances, if 447 Concord the finest loudspeakers needed). Specify Wound on low loss ceramic cores. UNIVERSITY REFLEX Mounting legs furnished when re- The only complete loua. quested. speaker line which solves SEND FOR SAMPLES ALL Give complete data regarding e Defense Sound Problems sistnce, maximum current, volt- University Laboratories age drop required and mounting 195 Chrystie St.. N. Y. C. space available.

MICROMETER We welcome your inquiries for FINE RIBBONS for FREQUENCY checking LUMINESCENT MATERIALS of Tungsten and Molybdencsooa transm itters, Molybdenum in widths .006" to 1" METER 1.5 to 56 mc., Fluorescent and Phosphorescent Chemi- in thickness to .0005" 0.01 per cent. Tungsten Ribbon to specification cals for Lamp and Allied Industries LAMPKIN LABORATORIES W. CROSS Bradenton, Fla., U. S. A. GENERAL LUMINESCENT CORP. 15 Beekman St. New York 732 S. Federal St. Chicago, III. CRYSTALS by 11II oOW 1s3 RADIO The Hipower Crystal Company, one of AND America's oldest and largest manufac- SIGNAL & INDICATOR turers of precision crystal units, is able to offer the broadcaster and manufac PILOT LIGHTS ELECTRICAL turer attractive prices because of their TEST EQUIPMENT.., large production and the exclusive for all electrical des ices. Hipower grinding process. Whatever AND your crystal need may be, Hipower WRITE FOR CATALOGUE RADoo PARTS can supply it. Write today for full showing a complete line of L'ES IN STUCIt information. assemblies for all purposes,..` HIPOWER CRYSTAL CO. HARVEY RADIO CO. SIGNAL INDICATOR Corp. Conveniently located at Times Square Sales Division -205 W. Wacker Drive, Chicago 140 CEDAR ST. NEW YORK, N. Y. 103 W. 43 ST. NEW YORK, N. Y. Factory-2035 Charleston Street, Chicago, III. ELECTRONICS - January 1942 113 INDEX TO ADVERTISERS

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Abbott Instrument. Inc 87 Lampkin Laboratories 113 Acme Electric & Mfg. Co 103 Lapp Insulator Co 5 Acro Electric Co 84 Lectrohm, Inc. 113 Advance Solvents & Chemical Corp 91 Lingo & Son, Inc., John E 85 Aerovox Corp 99 Littelfuse, Inc 86 Allied Recording Products Co 93 American Lava Corp 55 American Television & Radio Co 96 M American Transformer Co 13 Astatic Corp. 74 Mallory & Co., Inc., P. R 20 Audak Co. 114 McGraw -Hill Book Co., Inc 111 Autocall Co. 89 Mico Instrument Co 103 Automatic Electric Co 84 Millen Mfg. Co., Inc., James 86 Mu- Switch Corp. 90 B Mycalex Corporation of America 85 Ballantine Laboratories, Inc 82 N Biddle Co., James G 103 AUDAX Bliley Electric Co 105 New York Transformer Co 97 Brand & Co., William 57 Bud Radio, Inc 88 "RELAYED -FLUX" o C Ohmite Mfg. Co 7 Microdyne Callite Tungsten Corp 54 O'Neil -Irwin Mfg. Co 113 Cannon Electric Development Co 19 "The Standard 6g Which Others Capitol Radio Engineering Institute 106 Are Judged and Valued" Carborundum Co. 86 P Centralab Div. Globe- Union, Inc 2 Chicago Transformer Corp 60 Parker -Kalon Corp. 79 Cinch Manufacturing Corp 49 Permo Products, Inc 97 "ASTONISHINGLY Clarastat Mfg. Co 92 Precision Apparatus Co 98 REAL- Clare & Co., C. P 16 Premax Products 92 ISTIC" say leading musi- Cohn, Sigmund 96 Presto Recording Corp 68 cians. "EASILY Collins Radio Co - 61 - TOPS" Cornell -Dubilier Electric Corp 11 say leading technicians. Cross, H. 113 R R -B -M Mfg. Co 18 D RCA Mfg. Co 81, Back Cover The "RELAYED- Radio Corporation of America 15 FLUX" principle Daven Inside makes possible a moving Co Back Cover Raytheon Mfg. Co 98 system Dinion Coil Co 99 Rea Magnet Wire Co 75 far beyond anything yet devised - Driver Co., Wilbur B 105 . capable of reproducing all the DuMont Labs., Allen B 94 fine detail engraved at the original Dunn, Inc., Struthers 8 recording MICRODYNE bears - E Shure Brothers 70 out the contention of scientists that Signal Indicator Corp 113 high -fidelity is possible only with a Eicor, Inc. Simpson Electric Co 109 89 Sola Electric Moving- Inductor system. Eisler Engineering Co 113 Co 87 Eitel- McCullough, Inc 63 Solar Manufacturing Corporation 113 Electronic Laboratories, Inc 101 Sprague Specialties Co 56 Stackpole Carbon Co Flat to over 10,000 cycles Electro-Voice Mfg. Co., Inc 95 58 Erie Resistor Corp 4 Standard Pressed Steel Co 108 Standard Transformer Corp 52 Vibratory momentum ex- Sun Radio Co 99 tremely low F Superior Electric Co 67 Superior Tube Co 12 Absence of distortion Ferranti Electric, Inc 95 Synthane Corp. 51 Ferris Instrument Corp 108 nigh stylus compliance Formica Insulation Co 17 Low T Point -pressure G Complete with special Taylor Fibre Co 104 arm General Aniline Works 91 Terminal Radio Corp 109, 113 Thomas & Skinner With General Electric Co 9 14, 59 Steel Products Co.... 105 or without jewel Point, the General Luminescent Corp 113 Thordarson Electric Mfg. Co 64 sharp, clean -cut fat simile repro- General Radio Co 71 Triplett Electrical Instrument Co 107 duction of MICRODYNE regard- G -M Laboratories, Inc 104 - Guardian Electric Mfg. Co less of climatic conditions-is a 66 U marvel to all who have put it to the -H only test that really counts . United Transformer Co....Inside Front Cover University Laboratories 113 the EAR test. Hallicrafters Co. 89 Hammerlund Mfg. Co., Inc 6 Hardwick Hindle, Inc 78 Harvey Radio Inc w Pickup Co., 113 List Prices Harvey Radio Laboratories, Inc 113 Western Electric Co 73 H -B Electric Co 92 Weston Electrical Instrument Corp 77 1111.50 to *198.00 Heintz & Kaufman, Ltd 65 White Dental Mfg. Co., S. S 93 Hewlett- Packard Co. 72 Wilson Co., H. A 88 HIGH FIDELITY CUITEIt9 Hipower Crystal Co 113 Hygrade Sylvania Corp 10 List to $150.00 I WITH OUR COMPLIMENTS Professional Services 110 Instrument Resistors, Inc 104 A copy of "PICK -UP- FACTS" is yours International Resistance Co 53 Irvington Varnish & Insulator Co 76 for the asking. It answers many ques- Isolantite, Inc. 69 tions concerning record reproduction. J SEARCHLIGHT SECTION Jackson Electrical Instrument Co 96 ( Classified Advertising) AUDAH COMPANY Jones, Howard B 85 500 Fifth Avenue New York City EMPLOYMENT 112 K USED EQUIPMENT FOR SALE "Creators of High Grade Electrical American Electric Sales Co., 112 Kenyon Transformer Corp 90 Inc and Acoustical Apparatus Since 1915" Keuffel & Esser Co 3 Callite Tungsten Corp 112 Kirkland Co., H. R 113 Kahle Engineering Corp 112 114 January 1942 - ELECTRONICS AVEN OUTP T POWER METERS

OP-182

Convenient meter reading is provided' in this compact, space -saving OP -182 Outpu+ Power Meter. It is admirabl suited for many power and impedanc measurements, such as determining echo power delivered by an audio system to given load. characteristic impedance load variation effect on an A.C. sourc Terminal impedance remains essentially resistive over the audio frequency range of 30 to 10,000 cps. Impedances from 2.5 to 20.000 ohms in 40 convenient steps or available. The indicating meter is calibrated fro 0 to 50 mw., and from 0 to 17 db. Zero level at 1 mw. Four ronges of full scale readings from 5 mw. to 5 watts, and from --10 to -+37 db. are provided by the meter multiplier. Accuracy within 5% at midscale.

OP-961 A rugged, handy Output Power Meter for accurate measurements of audio signal systems havieg a maximum power output up to 50 watts. IReliable reedin ;s of power at impedances from 2.5 to 20.000 ohms are guaranteed by o meter multiplier aet.vorc of constant imf edance. in eem- binction with o carefully desk ned impedaece ncaw a w w changing eetworó that remains essentially resis -ive w MO MAN throughout virtually the entire audio range. Power ranges :over from 0.1 mw. to 50 watts in steps of 0.1 mw. indicating meter is calibrated from 0 to SI mw., and from 0 to 17 db., wit, a 1 "w. zero lsveL A 20 -step multiplier extends the meter pcwer reading from 0.1x to 1,000x scale value. and tie cb. reading in steas of 2 db., From -IO to +1'0 db., with full scale at 47 db, Accurate within 2% at midscale. Expanded DAVEN production facilities are now available for t ie construction of specialized equi]ment to specification.

158 SUMMIT STREET NEWARK, NEW JERSEY From the Earth to the Moon -that's the i distance that the 80,000,000 metal tubes manufactured since 1935 would reach, placed fi'teen feet apart!

Proved by ACCEPTANCE ...Proved by PERFORMANCE! 44 [L°19means MODERN!

ACCEPTANCE! In a little over six ears, the total! 12 REASONS WHY more than 80,000,000 -yes, 80mi1 /ion- PERFORMANCE -arid performance alone ItCA Metal Receiving Tubes have been METAL Tubes are BETTER Tubes! -is the cause of such leadership. Metal used by the Industry in over 300 elec- ( .,I I le self cli, i,rll tubes permit the designer to turn out I,ri.Iu,r Flexdnl,ls in Design tronic applications. And today, RCA is better equipment ... more efficient, more I; rra ter Precision and IIniformi1y turning out more metal tubes than eve, Lower Lnterelectrode Capacita cers dependable! For six years, the majority before -for 1941 production outstripped \u Envelope Emission Troubles Freedom Placement on Chassis of important receiving -tube AGI BROADCAST of all previous records! COMER Higher Getter Efficiency improvements has appeared Simple, Efficient Grounding ACCEPTANCE! Of the six largest -selling first in metal types - and Single -coded Construction receiving tube types throughout the en- many advantages still ap- Large Pin -Contact Area Flan In timnan. Lower Socket Costs tire Industry ... four are metal types- pear only in metal types! ro tinny More Rugged Construction

RCA Manufacturing Company, Inc., Camden, New Jersey A Service of the Radio Corporation of America In Canada: RCA Victor Company, Ltd., Montreal