PL41010 Eactronics

PL41010 EaCTRONICS

LECTRONIC KISSMETER

EE ELECTRONICS SECTION

r"" 2 Mallory Mk1getrol

TThe . Replacement .. 15 Control fi rst. 16 Line

Quietest and Smoothest ... by Test ! THE SIZE IS NEW THE SWITCH IS NEW I Inn. in te' diameter, it easily services the increasingly No chance of failure -it's Mallory engineered and Mallory pa,pnlar small sets where ordinary controls will not fit. manufactured. Pushes on -stays on -and uy,rks.

THE DESIGN IS NEW THE ELEMENT IS NEW Brand nr.. shaft le .I. saves valuable time in installation- More accurate oser -all resistance, smoother tapers, ample reduces inventor. -i nee one shaft lits all knobs. power dissipa

THE CONSTRUCTION IS NEW THE CONTACT IS . . . . NEW Extra quiet metal -metal -no -to contact between shaft Laboratory tests prove that the Mallory Midgetrol is the and cover or bushing. Special Mallory contact material. quietest control on the market.

THE SHAFT IS NEW THE TERMINAL IS . . . . NEW L nique -Iwo simple Igor all tittiut type knobs. No need tt on t break -twist enn§ all you want in close working for extra controls for difTemnl space. twat' fr panel to avoid shorting.

THE EXTENSION IS . . . . NEW THE SUSPENSION IS . . . NEW I.as. lo appl. Nith self -tapping Supplementary sirens. Two- point insures even contact pressure at all points of shafts available for installations wtni,li require them. rota . Larger bushing area -added support -no wobble.

Side snips neatly cot U-dip furnished to slide Lae half the U-dip to Spring steel clip in- Extension shafts with shaft to length desired. over end of shaft holds hold push-on tvpeknobs. eluded for use with two self-tap //ping screws set-screw knobs. knurled knobs. available n'lattn needed. It's the NEW Standard in Carbon (Controls. See your Mallory distributor.

a co tnc MALLOR CAPACITORS CONTROLS VIBRATORS SWITCHES RESISTORS RECTIFIERS VIBRAPACK' POWER SUPPLIES FILTERS R.a. U. S. Pat. Os. APPROVED PRECISION PRODUCTS P. R. MALLORY & CO., Inc., INDIANAPOLIS 6, INDIANA 3

I WILL SHOW YOU HOW TO START A RADIO SERVICE BUSINESS F,/f, 'c °' WITHOUT spa"ri nne CAPITAL

J. E. SMITH, President National Radio Institute LEARN RADI:':

t.; pArt or your ..raining you build this complete, powerful Radio Receiver that brings in KITS of local and distant stations. with BIG N. R. I. gives you ALI. the Radio parts . . . speaker, You Build This tubes. chassis, transformer, YOU sockets, loop antenna, etc. parts I SEND Radio Manu- Let me show you how you can Radio. Broadcasting, DER RADIO Radio Repairing. Public name Your own days . Your own factoring, Address Work, etc. And think of hours . as your own boss in your business. even greater opportunities in and Many Other Circuits own money- making Radio Electronics. I've trained hundreds of men to earn growing .v gold incomes in their own shops ... YOU PRACTICE with Gel Actual Lesson and Book Free this A. M. Signal men with no previous experience I Onerator, Pro- . and I can do the same for you. Art Nt \\" Sold fur my special tides amplitude. My unique train -at-home method DOUBLE i'Iti.E OFFER. Get actual ni ndniated makes learning easy. 1 send you lesson, "GET'T'ING ACQUAINTED YOU BUILD .this Tester that sig1lais for . manyny tests. BIG KITS of Radio farts. You get W'ITIi RECEIVER SERVICING," al.- you EARN EXThelpsRA MONEY fixing practical Radio experience building. sohttely free. Discloses short -enta used inhbors' Radios, in apure testing and experimenting with Ra- by Radio repair men to check and repair dio Circuits. You keep these valu- R111110 8. Over 80 pictures and diagrams! able kits to use in your own Radio Send now and also get my 64 -liage book, I Trained These Men business. "BOW TO BE A SUCCESS IN RADIO - TELEVISION - ELECTRON- GOOD JOB IN Make EXTRA Money In Spare Time ICS." See how quickly, easily you can started. Rut seed NOW! J. E. RADIO STATION YOU PRACTICE The day enroll, I send you get you II. President. Dept, 8J X, National "Am Bmadeast i.nr EXTRA MONEY booklets. Use your SMIIT Radia Institute, Pun «r Hoar oeer for St a t i;.t nR know -how to make EXTRA MONEY t W'aslt- K It (/ P. Fuud:unen- runip- fixing neighbors' Radios in spare Srnrh Radio Srhool. of Radio lut roui :ngen: 9. In C. tals ureut 111111 while From here it's in N. It. I. training lia; pana time learning. a short step to your own Radio shop ,; "- .IKltltï G. CIiLLET'r. 1 su.a. .... ,.I.,i.h. I, -., l'ali!uract. or a good-pay job in Radio ..ad Television industries. HAS OWN N. R.I. Traieed Mee Face Bright Future RADIO BUSINESS YCU BULO Think of money- making oppor- '., tunies in Police, Aviation. Marine Good for Both -FREE EXTRA CASI-I ACTUAL IN SPARE TI1stE MR. I. E. SMITH. President, Dept. 81X 1trued LESSON NATIONAL RADIO INSTITUTE, Washington 9, D. C. toue raJ,.t, t. : A for my s1ecinl I111UItL6 Mail nie FREE S mille Lesson and 64 -page book. t l".1 I I I 1 lt { t ai h- DO crt .e I. tins. 1 t No salesman will call. Please write plitinly.I T 1 I 'll 1 tti'l'tl Ril LlYl'It xc,, r.,. \ It free. in. I;e trau,.uu L,p'. u n in cho-k Age

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SEPTEMBER, 1948

1 4 Hugo Gernsback, Editor -in -Chief Fred Shunaman, Managing Editor 1[ M. Harvey Gernsback, Consulting Editor AtIII0 Robert F. Scott, W2PWG, Technical Editor R. H. Dorf, W2QMI, Associate Editor I. Queen, W2OUX, Editorial Associate CRAFT Angie Pascale, Production Manager Elmer Fuller, Shortwave Editor RADIO - Wm. Lyon McLaughlin, 1:1.1:1:TINN1/:8 Tech. Illustration Director

Incoreerat nn G. Aliquo, Circulation Manager SNORT WAVE CRAFT. TrLEVISION NEWSr John J. Lamson, Advertising Director ReOIO 6. T LrVISION

rTrn,le.n..,k ,a:. .,.I I . . r l':,., .l I.n.. Alfred Stern, Promotion Manager Contents September 1948 Editorial (Page 21) Soviet Radio Le"d.Tcrpedo by Hugo Gernsback 21 Electronics (Pages 22 -29) Kiss Meter -Electronic Osculat on Indicator (Cover Feature)... by Lyman E. Greenlee 22 Eclipse of the Radio Tube 24 The Crystal Detector, Part Ill by Jordan McQuay 26 Electronics in Medicine by Eugene J. Thompson 28 Television (Pages 30 -33) Video Alignment by Robert N. Vendeland 30 French Television Progress is Rapid by P. Hemardinquer 33 Servicing (Pages 34 -38) Radio Set and Service Review (Ward's Airline Models 74BR.2003A and 84BR- 1515A) 34 Regulating Voltage with VR Tubes by Richard L. Parmenter 36 Pepping Up Midgets by K. E. Stewart 38 Foreign News (Page 39) European Report Major Ralph W. Hallows 39 Audio (Pages 40 -43) Modern Phono Oscillators.... by Richard L. Parmenter 40 Two Channels for Hi -Fi by P. Hemardinquer 40 Instantaneous Interco. .... by Harold R. Newell 41 Three Bug -Free Amp'iiicr...... by John W. Straede 42 Test Instruments (Panes !S -:_) The A.C. Amme'rr S..ves testing Time. by John Melicharek 45 Tester Has New Features.... by V. A. Jeannot 46 Bridge Measures L -C -R by Rufus P. Turner 50 Amateur (Pages 54 -63) Four -Band Converter Has Crystal C'ntrrl. by Herbert S. Brier, W9EGQ Modifying the R- 44(ARR -5 oy L. W. May, Jr., W5AJG Relay- Controlled Ham Rig... by Richard H. Dori, W2QMI Construction (Pages 78 -81) Neon Lamp as Phototube by Robert Jonquet 78 Small -Space Metal Locator. by John Haynes 79

Communications T.R F . by T. W. Dresser 80 FM (Pages 87 -93) FM Station List 87 This year, as in every year since Departments 1939, more radio men will buy The Radio Month 10 Technotes ... . 73 more Radio Business.. 16 Try This One 74 Sealdtite* capacitors than People 64 Radio -Electronic Circuits...... 82 any other molded paper capacitors. New Device- 66 Miscellany 85 New Patents 63 Book Reviews 94 Molded paper tubulars are indis- Question Box 70 Communications 97 putably the best for moisture re- RADIO- CRAFT, 1948, Stpttmker. Volume XIX, No. 12. l'ublinhrd r wW,ly on OW 9:111 of Imih prrredin.t dIA° sistance and long life. All- Purpose I.. , Ì ,.t If -,.,.. t.. ,.. I, , 11 -., i.ri .1.... I' I (1 Suety, l'inlay., Ipllia 39. l'a. }:nle,e.I us seismal. el,.. a1 ,allrl11 l'.rl 4)l,.', Sp, , Nias 11.14'1 \4't of March 3, 1s :3 Apl.ir01.1mr trni.(rr Io Pila -Temp molded drlphl l' a time . Hi Sealdtites are the RA DCRAFT PUBLICATIONS, INC. llugn Relish irk, Pres.; M. Malley Gen.nbark, Vire- Ires.; G. :lion°, Ser'y. fortin. l',n,), i: W, 191$. L) Itadr,at 1'04 ions. lue. Text and illustrations most not be reproduced without best molded tubulars. Once you

EDITORIAL, ADVERTISING AND CIRCULATION OFFICES. 24 VVrsr Broadway. New York 7. N. Y. Tel. BE.ctor try them, you'll always buy them! eau. BRANCH ADVER, (SING OFFICES: Chicago: us W. W ,,hiuglon snrrt. 'trlrphaæ Randolph 78uá. Detroit: lt,.nu 1..2 l.rao:l,n, laoc.. _.,7o \ \est (:Laud Itn,l. Telephone Madison 7(1217. Los An- geles: Ralph W. Il :uiir,r, nun Souda hill St., Tel. Tucker 1793. San Francisco: Ralph W. Marker. 552 Market St., Tel. I:upheld 1.91x1. Get your catalog without delay! SUBSCRIPTION RATES: In U. S. and Canada. In U. S. possessions, Mexico, Routh and Comm] American min- ims, £:;.lu: 5.n. nn na st.110 for duce I.. .' yrara. Singly comas 20r. All tdher f i , Ir r unrins $L:,u a yea (ui . on SOLAR SALES $5.11° t.0 51 I. tue III,, v4''1,. . \lI.sI ,.nc m, m.lb for of CAPACITOR CORP. chain,. :.Id rear. Wh i, ordering ' ch :ul Re. Ideate funista n add rrss sleorii i pIa inn hog a eey t s-Iapper. All communications about subteripilons should be NORTH BERGEN, NEW JERSEY addressed to the circulation Manager, RADIO- CRAFT. 25 West Broadway, New York 7, N. Y. FOREIGN AGENTS: Great Britain: Ana. Publishing and Uisl vibe iug Cu.. Ltd.. 18 Bride Lane. Fleet St.. L011- don E.C.I. Australia: \Irl :ill's .\:alley. 179 Elizabeth Suret. Steil,ul1,11'. France: Ittentaois. Avenue d4' Pupe a. SEALDTITE MEANS LONGER LIFE Paris 2e. Holland: la, b 'rlilrrtr l a,o,tcr,ls, hr. Dieef 124 Ilr;mstrdr. G : International Book & Ness's Agroy. 17 Amerikis Stteet, Athens. So. Africa: Central Nrws Agency. Ltd., l'or. Ilissik & Commissioner Sis.. Jnhannesl.,.,.:: 112 Long SIII'rl. Coo 10.11: 3h11 with Si r, t. Durban. Natal. Universal Mink .\gene)'. Ill Harrison Street. Jul,.. burg. Middle East: ilei.mal zky Middle last Agency. Jaffa flouai Jerusalem. India: Susil Gupta (Mistrir. Co., :U mita Bazar l'ari ika 1.1.. 11 Ananda Chaur :Jee lane. C'alrnua.

MEMBER ABC PAID AUDIT CIRCULATION 6 MONTHS TO DEC. 31, 1947- 102,688. (Publishers Statement) OF CIRCULATION PRINTED FOR SEPTEMBER ISSUE - 150.000 RADIO -CRAFT for s r

Radio Servicemen: Here is the Industry's Newest, Practical Course in eision fiN

i by the Famed Backed CREI Facilities of * Your Future! Safeguard Money Earn morem Expanding Iiiin the Field Servicing

ö_

CREI -long known as one of the nation's outstanding knowledge of TV fundamentals, lessons in technical schools-now offers good radio servicemen a practical basic radio mathematics, meters, lenses and home study course in Television and FM Servicing. It is based mirrors, inductive coupling and condensers on the assumption that you are a practicing radio repairman ultra -high frequencies, practical with sense enough to know that if you don't learn FM and at applica- Television, you might as well close up in a year or two. tions of resonant circuits, TV tubes, FM The shop without qualified FM and TV repairmen will soon receiver alignment, TV antennas, picture be as obsolete as a blacksmith shop ... because approximately synchronization, TV receivers, TV trouble- 800,000 television sets will be produced in 1948 alone . shooting -and much more. because there will be 4,000,000 more radios with FM by the end of this year ... because the repair business will go to CREI is an accredited technical school with 21 the men with ability to do a scientific servicing job on any years experience teaching radio engineers and tech -r: kind of set. nicians, both in home study and residence school : :I

CREI developed this course at the request of several nation- work. Hundreds of practical engineers with key '' :1

ally known manufacturers and distributors who recognized the positions in industry, radio, and TV stations owe j

lack of qualified servicemen to handle TV and FM installations their successful training to CREI. More than two . and servicing. After careful preparation CREI has created this years of preparation have gone into this FM & TV special servicing course. It has been tested -and proved in the servicing course. Backed by one of America's fore- field. It is as practical as we can make it. It enables you to most technical institutes, it is designed for one put the knowledge you gain from each lesson to work imme- purpose only: to help a good radioman become a .`j diately. It won't make you rich overnight. It won't make a ggood FM-TV serviceman. The course is practica /,.the';:' television engineer out of you in "ten easy lessons". You cost is popular. Get complete details by filling in and.1 4 don't get a "free television set with your first lesson " -or your mailing this coupon. last. But here's what you do get: a systematic method method of FM and TV installation and maintenance, MAIL CAPITOL RADIO ENGINEERING INSTITUTE Radio Service Division of TODAY 11th Park Neal, N. w., kept SNE, Itashioltss 10 I. C. Gentlemen : Please send me complete details of your new home study course in Television and FM Servicing. I am attaching CAPITOL RADIO a brief resume of my experience, education and present position. tNGINEERING INSTITUTE NAME An Accredited Technical Institute STREET ti Dept. 598, 16th & Park Rd., N. W., Washington 10, D. C. CITY__ ZONE STATE -_. I AM ENTITLED TO TRAINING UNDER G. I. SILL. Branch Offices: New York (7) 1 70 (roadway San Francisco 121 760 Market St. SEPTEMBER, 1948 li Optev AIR HING Sziíeue«ce could Build this Matchless WIRE ECORDER PHONO - COMBINATION

AIR KING Portable WIRE RECORDER Model A -750 -1

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a . Let NATIONAL SCHOOLS, of Los Angeles, practical Technical Resident Trade School for almost 50 years, You race.ve all parts, in- uudinq -noes, for build- you for today's unlimited opportunities in Radio ing this fi-e, modern train Superheterodyne Reciv- er. This and other valuable standard equipment becomes your property. ;,°t,Ñ tell r°` I 4 ``-0` u Arc Good Jobs Await the Trained Radio Technician Lessons and You are needed in the great, modern Radio, Television and Elec- tronics industry! Trained Radio technicians are in constant and Instruction growing demand at excellent pay -in Broadcasting, Communica- Material Are Up-to-date, Practical, Interesting. tions, Television, Radar, Research Laboratories, Home Radio Schools Shop' Method Home Study Service, etc. National Master National Method Home Training gives you course, with newly added lessons and equipment, can train you Schools Master Shop home, exciting basic and advanced instruction in all phases of Radio, Television in your spare time, right in your own for these to by nu- has been proved by the remarkable and Electronics. Each lesson is made easy understand opportunities. Our method All material has of National Schools- trained men all over the world. merous illustrations and diagrams. instruction success been developed and tested in our own shops and laboratories, under the supervision of our own engineers and instructors. A You Learn by Building Equipment with free sample lesson is yours upon request -use the coupon below. Standard Radio Parts We Send You Here's lust Few of the Interesting Fade Both Home Study and you Learn with the Your National Schools Course includes Resident Training not only basic theory, but practical FREE MANUAL Offered training as well-you learn by doing. We send you complete standard equip- I. Routine for diagnosing Radio Troubles. ment of professional quality for building various experimental and test 2. Preliminary inspection of Receivers. units. You advance step by step until 3. How to Test and Measure Voltages. APPROVED FOR you are able to build the modern superheterodyne receiver shown above, 4. How to Test Speaker in Audio Stages. VETERANS which is yours to keep and enjoy. You 5. How to Trace the Circuit and Prepare Skele- perform more than 100 experiments ton Diagram. build many types of circuits, signal- generator, low power radio transmit- 6. Complete Reference Table for Quickly Lo- ter. audio oscillator, and other units. cating Receiver Troubles. Check Coupon Below The Free Books shown above tell you more about it -send for them today! NATIONAL SCHOOLS 'rTr tW:, Now ! NEW PROFESSIONAL MULTITESTER 105 ANGELES 37, CALIFORNIA EST 1905 INCLUDED! MAIL OPPORTUNITY COUPON FOR QUICK ACTION

This versatile testing instrument is portable National plurals. D.pt RC -9 and complete with test leads and batteries. 45510 S. Figuerua. L9, Angeles 37. Calif Simple to operate. accurate and dependable. You will be able to quickly locate troubli a and adjust the most delicate circuits. You can use the Multitester at home or on service calls. It is designed to measure AC and DC volts, current, resistance and decibels. You will be proud to own and use this valuable professional instrument. Slrl.l;r:..

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IALPETH

NEW WORD ON

TELEPHONE CABLES

Lead makes an excellent sheath for telephone cables - sixty years and thousands of miles in service have well proven that. But lead is useful in other ways -storage batteries and paint, to name only two. So the telephone industry shares the limited available supply with other claimants. Before the war when there was no lead shortage, Bell Laboratories en- ginccrs sought to develop better and cheaper cable sheaths. An ideal sheath is strong, flexible, moisture - proof, durable and must meet specific electrical requirements. No single material had all those virtues, so thoughts turned to a composite shcath,each element of which should make a specific contribution to the whole. Various materials and combinations were studied. Desirable combinations that satisfactorily met the laboratory tests were made up in experimental lengths, and spent the war years hung on pole lines and buried in the ground. After the war, v with an unparalleled demand for cable and with lead in short supply, selection was made of a strong composite sheath of ALuminum and PolyETHylene. Now Western Elec- tric is meeting a part of the Bell System's needs with "ALPETH" sheathed cable. BELL TELEPHONE LAH0110011IES ..` Meeting emergencies- whether iti° they be storm, flood or shortage of materials - is a Bell System job in which the Laboratories are proud to EXPLORING AND INVENTING, DEVISING AND PERFECTING FOR take part. CONTINUED IMPROVEMENTS AND ECONOMIES IN TELEPHONE SERVICE.

RADIO -CRAFT for 9

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TELEVISION TECHNIQUES were the roller and the stylus, transmitting used last month by Northwestern Uni- current through the paper, causes the 2 out of 3 versity_ to instruct doctors and medical transmitted writing to appear. students in operative methods. The The machine, developed less than a broadcasts, described by the university year ago by Garvice H. Ridings, is ex- as the largest medical classroom in the pected to cut time required for message Need It! world, had an estimated audience of transmission between New York and 7,000. San Francisco to 10 minutes. ESPEY Four image orthicons were set up in // the Passavant Memorial Hospital in ULTRASONIC diagnosis and treat- 7kc Clrnt- JNilt Ch.;, Chicago, two above each of the two ment of cancer was demonstrated last operating tables. Every detail of the month by Drs. J. F. Herrick and E. J. operations was clearly picked up and Blades of the Mayo Foundation Insti- reproduced on the screens of receivers tute of Experimental Medicine. on the Navy Pier and throughout the Supersonics, generated by crystals campus in classrooms. John K. West of and transmitted to the body through RCA, which made the technical arrange- paths of oil or water, travel in a sharp- ments, said the setup was the largest ly focused beam. The beam is reflected temporary TV installation ever made. by any part of the body it hits, and During the operations, the surgeon in where there is a cancer the character charge commented on each of the steps of the reflection or echo is abnormal. he took. Before the operations, he lec- After the cancer is detected it may be tured on the case history. treated by the same type of ultrasonic The television technique has the same beam, though with increased intensity. effect as the instructional operating The beam, directed against the cancer, theatre but it gives each student a much shakes it to pieces, the a destroying tis- According to recent closer view and enables an almost in- sues cell by cell. survey, over 18 million finite number of observers to watch at The Mayo experiments have so far the same time. been only on animals. Other types of consoles were built knifeless surgery using ultrasonics are A FACSIMILE machine designed to also under investigation. before '44 increase the speed of telegraph service was announced last month by Western for radio tech- That's right! The newest are four years old, MINIMUM WAGES Union. The machine, 10 x 11 x 7 inches, nicians are established in a new order and there are more than II million of will be installed first in the offices of them that ten years the 18 passed by the government of the Can- are old. Of customers who handle five to twenty million owners, 51 %, or over 9 million adian province of British Columbia. The LIKE their cabinets -in spite of the fact messages per day. order, which went into effect June 1, that the vast majority of receivers are The sender of a message writes his defines the qualifications and the work hopelessly obsolete, lacking such present - text in longhand or by typewriter on a of a radio technician and raises his min- day essentials as FM. sheet of sensitized paper. The message imum pay from the unskilled -labor rate Furthermore, over 90% of the console is placed on a roller, in contact with of 54 cents per hour to 80 cents. The owners WANT FM, but less than 6% HAVE which is a stylus. As the roller turns, order also regulates the number of it. What a replacement market! current through the paper varies ac- working hours and overtime pay. It was to fill this tremendous need that cording to the written or typed marks. The order was promulgated as a re- ESPEY designed its line of top -quality cus- The machine automatically becomes a sult of the work of the Associated Radio tom -built chassis, supplied complete and ready to operate in your customers' cabi- receiver when the central office signals Technicians of British Columbia, an or- nets. that a message is on hand. A blank ganization of radio repair, installation, sheet of sensitized is on and design For further details about the ESPEY re- paper placed technicians. placement chassis, and the opportunities in the replacement industry, we urge you to write today to Dept. C -7.

628 EAST 72 sTRLaT+N2w TORK.2t.N:

SUPER -MITE RADIO SUPER -MITE FEATURES! PACKS AMAZING World's most powerful min- POWER! iature radio. Uses War -Born midget Celectronic tubes. $399 oast -wide reception obtained. Powered by midget hear- Ina -aid battery. Picture diagram for radio beginners. Brilliant red chassis. chrome and black dial, streamlined bakelite knobs. Complete kit ready to wire as shown Only $3.99 Post Pall. Tubes 95c each. This high quality set not available elsewhere at 10 times this price! ELECTRONIC RESEARCH LABS. 1216 Park Row Bldg., Dept. RC, New York City 7 New Western Union facsimile machine brings the telegraph office to the executive's desk. RADIO -CRAFT for The Radio Month SPECIAL PERMITS for AM broad- put of a standard nerve stimulator from cast stations to operate beyond their zero to about three volts at the respira- regular daily sign -off times were abol- tory rate. You Caaffath these ished by the FCC last month. Limited- In using the device, the physician P Cd Pales/ stations have been applying for makes a small incision in the patient's y !/ y % f time chest and attaches a silver electrode to / and receiving these "special temporary authorizations" for several years to per- the phrenic nerve. The patient will then Transformer Scoops! mit them to broadcast programs which breathe at a rate which can be governed Traunformers listed are full- limited by adjusting the instrument. The stimu- shell type. upright mount- would not fit into their ing. Color coded leads. schedules. lator is expected to be useful not only Brand newt Quantities are The authorizations defeated the pur- for polio victims but also for those suf- limited-so order now! MA -2515 -Power Trans- pose for which the stations' broadcast fering from poisoning and electric former 850 VCT, 200 MA: limited prevent nighttime shock. It may also replace the respirator 5V, :i:t: and 6.3V, 5A. 455' time was -to x 4' x 3 3,'. Regular list interference with others on the same used to resuscitate drowning people. 612.75. Now only. $4.55 ea. frequency. The situation is particularly MA- 2523 -Driver Trans- former 61,6 to PP 61.6, Class bad now that the number of AM sta- FIRST 3 -WAY TELECAST was made A112. Rated 40 MA. Pri- mary current. 3 x 2i5' x 3'. A $3.75 value. Mid- tions on the air is so great. by NBC last July. The broadcast, held se. in connection with the Democratic con- America's value price 51.68 MA- 2521 -Filament Transformer 115 V. 8 -cycle THE IRON LUNG may be replaced by vention, featured James W. Girard, for- primary. 6.3V, 3A secondary, 3' z 255' x 254 a new electronic instrument which was mer U. S. ambassador to Germany, who $1.49 se. shown last month at the first interna- was in New York, Clinton Anderson, tional poliomyelitis conference in New Secretary of Agriculture, in Philadel- Amazing FM Antenna York. The instrument, called an elec- phia, and David A. Morse, acting Secre- Model A -100 for use indoors --eliminates trouble of erecting outside antenna. Tunee 88 -1118 MC band tronic stimulator, operates on batteries tary of Labor, in Washington. The with excellent signal gain. May be mounted on wall or out of sight under rug. Complete with twin lead - and is small enough to be carried any- voices of all three were heard simul- in cable: merely connect to receiver antenna posts. A motor and series of cams at- taneously and the picture of each ap- Brand new In original factory cartons.ShIppIng wt. where. 1 lb $1.45 sa. tached to a variable resistor vary the peared as he spoke during the informal 2-millisecond, 40 -per- second pulse out- conversation. To make the broadcast possible, video CONVERTERS! These farnous -make converters have never before signals from Philadelphia were sent to been offered at these low prices! All are brand new, complete. ready for Immediate installation and TO OUR READERS New York via the Philco microwave operation. Quantities are limited: get your order relay and the Washington signals were in NOW! YOU have now before you the first transmitted to New York on the north- completely revamped and im- 32-Volt DC to 115-Volt, 60-Cycle bound co -axial cable. These, together Model 1112. Rated 100 watts. Gray wrinkle -finish proved copy of the "new look" with the signals originating in New metal cabinet with ventilating louvres and bumper RADIO- CRAFT. The entire issue is now feet: measures 6y'x855'x4. Has outlet receptacle, York, were all available at the New line cord and plug. Circuit Is fused for overloads. printed on a super -calendered paper On-off switch. A sturdy, dependable unit for many master switching panel. All that applications. Shipping weight 15 lbs $17.55 g. stock; the magazine has been in- York -2 100 pages; color has been was necessary each time a new voice Model 2115e. Dual output for operation of both creased to radio and appliances; rated 100 watts. Streamlined added throughout many pages; and spoke was to throw the proper switch metal ease with smooth brown finish and chrome carrying handle. Complete with line cord. plug and the magazine has now been coin- to send the speaker's picture to the New overload fuse. On-off switch. Especially good for = pletely departmentalized, omitting farm use. Measures 6'x855'3814; shipping weight York transmitter (WNBT) and through 15 lbs. Regular $80 list 522.55 all continuations. This is only a the south -bound co -axial cable to the will be Modal 145. Heavy duty converter with battery start! Further improvements other stations of the network. An inter- cable and clamps. Ventilated cabinet with wrinkle made continuously. gray finish: bumper feet. On -off switch, two outlet esting point is that video originating in receptacles. Rated 350 watts. Measures 954'x1534 We hope that you will be pleased Philadelphia and Washington was sent 17'. Shipping weight 55 lbs $51.51 with your magazine -your com- to local in those cities only ments will be appreciated by receivers 115-Volt AC to 12-Volt DC after passing up to New York for Medal 2752. For operation of 12 -volt DC equipment and for trickle charge of batteries. Rated 120 THE PUBLISHERS switching and then back again via the watts. Trim metal cabinet with ventilating louvres and bumper feet: smooth gray finish. Fused for III'. network Line cord. on -off switch. 83.5.x8W 5 11 1lllllillllllllllll11 1111IIIIIIIIIIIIIIIIIIII:II:IW! IIIIIIIIL' 11IIIIIIIIIIIIIII1111IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII a regular cable. overloads. plug. x854'; shipping weight 22 Iba. Regular $39.95 list. 525.55 115-Volt DCto 115-Volt, 60-Cycle Model 267. Small unit for operation of docks and other small motors. listed ` watts. Measures only 9'x2'': shipping weight 3 lbs. Enclosed in smooth gray metal case. Ices line cord and outlet receptacle. Regular 916.05 list. 95.95 12 -Volt DC to 115 -Volt, 60 -Cycle Model 2774. Compact unit measures only 7'z5'z Rated 12 watts; fused for overloads. Smooth gray-finish metal case with mounting brackets. Regular $49.95 list $17.95 TERRIFIC SAVINGS ON CERAMIC GRID CAPS 3.. clasp to fit 807, 2X2 and other popular tubes. Made by a famous manufacturer. Itegu- lar21c. ( :et your share while they last at this sensational low price. MA -2234, 6 for 79c Order from this Ad Quantities on above -listed items are strictly limited You must act fast to make sure you get what you want. Send 25% deposit. Pay balance plus postage on delivery. (let your name and address on Mid- America's select mailing list to receive monthly bargain bulletins that give you first crack at the latest, greatest. money -saving buys in radio parts electronic equipment, tubes. etc. Send orders and mailing list data to Desk RC-98.

Dr. James L Wh ttenberger and S. J. Sarnoff with their electronic nerve stimulator. SEPTEMBER, 1948 1; 'l'Iir.e I::IIIiII 4Noutli

TV REALLOCATIONS will have a profound effect on broadcasters and re- MORE TUBES and PARTS ceiver owners, said John A. Willoughby, MORE and acting FCC chief engineer last month. SENCO! Emphasizing the fact that he was speak- ARE ,BOUGHT FROM ing only for himself and not on behalf of ...... ,,,,,,,, ,\\\\\ `\\\ \\\ 1 the commission, Mr. Willoughby said the lower end of HERE'S WHY . . . Our policy of quantity buying, low overhead, cash sales, the present television direct merchandising -eliminating all unnecessay expenses that add to your price - band (channels 1 -6) may be wiped out enables us to pass along large saving.. Io you. Each and every item we advertise has in two years, to make way for fixed and been carefully priced and is offered to you at an nhsolhte minimum cost. Take ad. mobile services which require the space. \ vantage of these savings now! Channels 7 -13 will be used for TV for perhaps 10 years. in Mr. Willoughby's \ THOUSANDS OF TUBES! LOOK AT THESE ITEMS! opinion, but only for "low-definition" ALL BRAND NEW! Heavy Duty SPEAKERS transmission. The area above 500 Inc Top quality. iirrc,eie o -bu dI sueak. will be used for high -definition black - Individually Cartoned! ers at absolute minimum cost. P.51. and -white and color transmission, which R. M.A. Guarantee s Alnico V ea. 99e may Come in two years. :r P.51.- 1.17 oz Lots of Lots of Alnico V 31.15 According to Mr. Willoughby, a tele- 10 10 1- P.M. I ox Tyne Each Each Type Euh Each AInlro y 9c vision station starting operation on a 4- x P.M. Speaker 1.989 0Z4 69e 59c 6V6GT'G 45c 39e 6' low P.51.- I oz -frequency channel in the next two IA3 45 39 6X5GT G 49 39 á 43 -i Alnico 1- 990 59 49 7A4 53 Fears is faced with possible IASGT /G P.31. -1.47 oz Alnico V 1.15 loss of its IA76T /O 55 45 747 59 49 ' 6' P.M. 2.15 oz Alnteo V 1.55 transmitter and antenna investment. 1H5GT /13 4499 7B6 44 35 1'.51. 2.15 It 49 41 8' ox Alnlro V 2.75 59 7F7 1'.51. u.s oz 7N7 49 44 s- Alnico V 3.69 follows that receiver owners would also I LA4 49 39 III P.M. -ITN oz Alnlro V 1.39 1LM4 69 59 7X7 1 1'.51. -3.2 oz Alnico V 4.95 take some loss, even if only that re- 1 LN5 69 59 7Y4 FMI 44 35 Pr P.M. -6.$ 'e. -\Intro V 5.95 I N5GT/G 59 49 44 35 quired to purchase IS- l'.31. - -21 oz Alnlr» 3 with BVn P.P. conversion units. I 2A6 29 25 55 49 Output 37.95 complete 59 55 12A8GT 35 28 FCC hearings on the TV allocation 185 8' Dynamic ONO Mmes field with 6TG l' l'. 114 69 55 12AT6 50 45 Output 12AT7 69 59 3.95 complete problem will begin September 20. 1T5GT 59 49 12' Dynamic 6811 dune 12BA6 50 45 field wills 6V.: 1'. I'. 1U 36 30 Output 6.95 complete 45 39 1213E6 50 45 IV I2' Dynamic 1000 ohms Betel 5.95 54 43 12F5GT 35 27 RAILROAD s e r v i c e RÁ5 45 35 12H6 39 34 TELEPHONE 2M 49 39 121501 25 19 Famous VOLUME CONTROLS will be inaugurated soon on the 436 -mile 2X2/879 35 121707 45 39 run between New York and Buffalo, Nationally advertised brand. Fred H. Baird, general COMPARE OUR PRICES! An excellent buy: passenger agent 39 12K7GT 45 39 All Brand New. of the New York Central announced last 3C5GT 5 49 12K 8Y 35 25 384 55 45 12070T 45 39 month. This is the longest distance over 79 69 125A7GT/6 40 32 10.0110 ohms V.C. with switch. 3' shaft 3V4 oluns 3' shaft which such a service 5U4G 50 40 125C7 1634 49 39 2,0110 V.C. with ::each, has been planned 125F7 35 32 511.010 ohms V.C. with switch. r shaft SW4GT/G 39 34 ohm, switch. shaft to date. It is the first installation to be 5X40 39 35 1221G7 43 37 1n0.000 V.l'. with 3' 250.11011 ohms switch. Y shaft -Tapped 5Y3G 42 37 12817GT 55 49 V.1'. with operated on 51111.000 w91h t- the frequencies assigned for 40 33 128K7G7 G 45 35 hms V.C. ssTItrh. shaft -Tapped r\ L7 49 1 me¢ Inns V.C. with .. Pi h. a shaft -'yapped general highway 5Y40T/G 39 32 12 mobile radio use in the 2 meg ohms V.P. with s'i 3 shaft- 'I'apprd 5Z3 49 39 12807GT, G 40 32 30- 44 -me band. 524 59 49 128137 35 32 only Lech 6A7 50 45 14A7 65 55 44c Transmissions will be between the 6A8GT 49 39 14B6 59 49 6AB7/1853 53 4e 24A 49 39 train. which will use a special type of 69 59 6AC 5 69 9 POWER TRANSFORMERS 6AC7 1852 65 60 25A6 antenna, and nine Bell System fixed sta- 6AG7 6AK7 89 79 25L6 T, G 49 39 49 45 tions spotted along the right of way. 6A K5 74 69 2525 All fully shielded. flush mount. f Quality construction at sensationally FM will he employed. Passengers will DELIVERY! I-, IMMEDIATE low prices. be able to make a telephone call from 6B7 55 49 252667 45 39 61366 79 69 26 45 32 the train at any time during the jour- 49 44 61316 69 59 27 100 mil -0.3T @ 3 amps -SV @ 2 amps $2.95 ney. 6C4 29 25 32L7GT 52 4a 750V- C.T 42 32 6C5GT 40 35 35 5I 150 mil -6.::V @ 4 amps -5V Or 3 amps Plans are made to extend the service 6C5MG 89 79 35L6GT G 39 730V C.T 339 40 over 6C6 45 32 35W4 ü 200 cal 3.3 :nnn..3v w 3 the remaining 525 miles between 40 ma ..3w 6C8G 37 29 351'4 43 amps 11155- C.T. 4.45 6D6 49 45 35Z3 44 35 Buffalo and Chicago as soon as more 6F5 55 45 35Z5GT/G 43 39 fixed stations are ready. 6F6GT 45 39 36 35 29 Milwaukee AUTOMATIC 6F7, VT70 49 39 39/44 25 19 45 614667 G 45 39 41 49 RECORD CHANGER 41 61567 G 45 39 42 ELECTROCUTION of Mrs. Harold E. 616 59 49 43 5457 47 ONLY Wiseman of Youngstown, Ohio, oc- 617G T 42 38 45 49 39 6K6GT/G 45 39 452567 59 49 curred last month when a radio she had 6K7G 50 41 39 6K7GT/G 49 39 47 $13.95 placed on the edge of the bathtub fell 49 50AS eó 55 6K8G 55 Complete with into the bathtub. Death was swift and Astatie 1.82 OUR PRICES! Crystal Cartrldie. sure. COMPARE Mounting Springs 6L6G 79 69 50135 42 32 and Full Instruc- This is the third such death reported 59 49 50 L6G T 50 45 6P5GT 45 tions, in RADIO -CRAFT in 47 39 50Y6GT 50 three months; many 6E1767 45 6R7 55 45 56 55 more have been unreported. 6R7GT 59 49 57 45 39 Amazing CARTRIDGE Value 49 39 58 45 39 Every 6SA7 29 radio man realizes the great 44 37 7IA 39 Fresh stock of brand new 68A7GT/G 39 55 45 75 50 cartridges. Order now to risk taken by any person who places a 6S B7 45 o5. 39 34 76 49 be ore you get all you 6S07GT 27 radio within 65F5 49 39 77 35 need. reach of the bathtub or 44 39 78 49 39 6SG7 40 38 $1.49 sink. It is up to radio men to warn their 6SH7GT 32 80 1.70 Astaue Crystal Cartridge 66176 ü 37 83V 79 69 friends and customers that the mixture 49 39 84 624 49 39 N7 wehster Crystal Cartridge 1.49 6SK7GT, G 45 49 47 65 49 of radio and water may be 6SL7GT 25 2.95 even more 6SN7GT 49 47 99V 35 t. , ,. N.f.i. 63Q7GT/G 44 37 99X 35 25 dangerous than gasoline and alcohol. 76 6SO1 49 39 117Z6GT, G 89 89 6U6 49 39 1828 99 39 29 WALKIE- TALKIES were used by 100 6U7G 35 25 1231 PLACE YOUR ORDER NOW! 39 29 61/ 56 59 49 1644 student surveyors of Rensselaer Poly- P technic Institute in a 3 -week field study MINIMUM ORDER 31.00 concluded last month in the Poultney, WHEN ORDERING - Send 25'. deposit for all Vt., region. As the field men read their C.O.D. Shipments. In- clude sufficient instruments they reported the findings excess will be refunded. by radio directly to the central office at Orders without postage will be shipped express Green Mountain Junior College. As a collect. All prices F.U.M. 73 West Broadway, New York 7, N. Y. New York Cit7- result, tabulation and mapping kept TELEPHONE BEEKMAN 3 -6498 pace with field work. RADIO -CRAFT for 1.3 t toe Do you Q Make Good Money? Q Have a Real Job? ® Build for Future Security Have Your Own Business TNENget the facts about OUR GREATEST OFFER IN 17 YEARS ... to help you learn TELEVISION.. RADIO.. ELECTRONICS IN YOUR OWN HOME Yours to Build and KEEP! Here's good news...big news...our BIGGEST NEWS in 17 years. Now you get and keep many shipments of Radio -Electronic parts ... work over 200 "Learn - By- Doing" Experiments... build and keep a quality 6 -tube "Super" Receiver with Magic Tuning Eye... Using the many shipments of bearing build and keep a commercial -type, jewel- parts and assemblies (left), you Multi -Meter . .. use fascinating, instructive HOME MOVIES to help you grasp important points faster build and keep this 6 -tube easier ... get real Employment Service. "Superhet" Receiver and jewel - (above) Mail coupon below. Get the complete story. bearing Multi -Meter to See how we do BOTH -(1) Prepare, then (2) Help you give you practical experience get started in America's thrilling Radio- Television- AT HOME in ASSEMBLY...WIRING Electronic field. .. SOLDERING ... TESTING .. . TROUBLE SHOOTING!

LEARN FASTER . . . EASIER w - M' ,t' RIGHT: You receive the loan C+ IORg of a 16mm. Motion Picture . Projector and many reels of F- equipment CTSI e 8 iflall of-his "Learn -By- Seeing" film to "KEEP DOING".IE. ..You speed your of .* 200'íLEARN-BY- - - understanding . ` important points.You get this remarkably effective train- ins aid ONLY from D.T.I. _ ' t f. , .TRAIN IN CHICAGO LABS Nip we im If you prefer, you can get DeForest's Training, Inc. M/ all of your training in our , 2533 N. Ashland Ave., Dept. RC -E9MAI TOD modern, well- equipped Chicago 14, Illinois Ar g Chicago Laboratories. Write for all the details , Send me complete details showing how I may make my start there is no obligation. in Radio -Electronics -Television. No obligation. . Name Age DeFOREST'S TRAINING, INC. IlAddress Apt CHICAGO, ILLINOIS llCity __ Zone State Associated with DeVry Corporation, If under 16, check here It a discharged veteran of Builders of Electronic and Movie Equipment for special information. World War It, Check here.

SEPTEMBER, 1948 INDICATOR SCOPE GLIDE PATH RECEIVER I D -41 /APQ -13 C -1 GYRO About diameter R r by 15" deep. Contains I -5F P7. 89 ARN 5 A I -6A K5 tube. 5 Grain of Wheat 3 V. pilot lights, C magnetic deflection yoke. Formerly used for blind landing but adaptable to Part of the -I Auto Pilot which is sold separate and condensers, may be used resistors. potentiometers, sockets .. $6. many other use such as receiver for new or to conduct many interesting and amusing e P 95 police peri ments. Operates from 24 citizen's band. s Band of operation 326-335 MC on V. DC or ay be operated any of three pre -determined crystal controlled fre- for short periods on 110 V. AC. Gyro will run for approx. 15 minutes after actuating. quencies. Contains eleven tubes. 6 relays and other Size -approx. 8" WILLARD LEAD ACID CELLS valuable parts. For 24 V. DC operation. oSize B'2" x 8'2 ". PRICE x $8.50 Price e as s. Price, complete shown $6.45

MARKER -BEACON RECEIVER Can be adapted to radio controlled devices. Was used by pilots to flash a signal lamp on aircraft Instrument panel when in range of a beacontrans- mitter. Responds to modulated signals over variable range of 62 to 80 Mc. Tube plates and filaments operate directly from 24 V. DC. Can be adapted for radio con- of experimental trol ap- 6 V. I New) paratus opening garage (Dry -charged) $3.00 doors. etc. Circuit diagram and parts list in- 6 V. I In metal carrying case) (Add cluded on either model specific 1.265) shown below: $4.00 357 BC- -- contains I 2C8 BC -966 -A IFF and 12SD7 tubes and Approximately sensitive relay (size 2 meter frequency operation. 14 tubes. 350 HRU IDC) V. DC dynamotor 12 V. DC input. Contains voltage regu- 5'3( a $2.95 lators other One parts. Worth more POWER . . . sr andth manyprice asked $4 5 V SUPPLY BC - 1033 - contains é 6SH7. 6SL7 and I2SN7 24.2ám V. t o:, 70 p. 2000 tubes, sensitive relay (size 53a" watts gasoline x $3. engine genera- e x 3'4 "). 50 5 tor with electric starter. Power supply which can be OXYGEN used to operate 24.28 TANKS start airplane gines. charge batteries, as e welding machine. lighting system. for amateur radio station. 21' 2" Aviators oxygen 17'2" a 24 ")e ". Wgt. 115 lbs. breathing bot- tles. Non - shat- ARC terable. Choice BC- 1155 -A -4 TRANSMITTER & REC. of two types. SYNCHRONIZER (A) Withstands lbs. tires- Another invaluable unit for the Television and VHF ex - 2000 perimenter. Contains 19 Mc. IF strip using 5- WE717A Lobes. A total of 24 tubes included, consisting of 6- INCLUDING (B) Withstands W E717A's. 2 -6SL7GT's. 2- 6AC7's. 5- 6SN7GT's. 2- 6N7GT's. 2- 6L6's. 6V6GT, 6AG7's. I--6AC7. I CASE 500 lbs. pres- I- 2- sure. and I -6H 6GT. Other parts included are 6 pots, n Amphenol 831 R chassis connectors and numerousmerous c densers, resistors, and transformers. Weight $17.75 $19.95 CHOICE 22 lbs. Size 21 "L x II'2 "W a 732-H. PRICE $4.95 ea.

A B .

Operates on any of its 4 predetermined crystal con- APN -1 RADIO ALTIMETER trolled frequencies in the range of 140 MC. Com- plete with tubes, remote control. junction box. shock mounting base and I ecting plugs. This unit ideal for amateur UHF or mobile telephone. Op- erates from self -contained 24 V. DC dynamotor.

SN -7C /APQ -13 Sensational offer for Television engineers. Contains 19 A complete 460 Mc. radio receiver and transmitter Mc. IF strip containing 5-W E717A tubes. Other HF which can be converted for ham or commercial use. strips containing 2- 6AK5's, 3 -O$L7GT's, I -W E7 I 7A. Tubes used and included: 4- I2SH7. 3- 12517, 2- 4-6SN7GT's. 2- 6N7's, 2 -6L6's, 1-6H 6. 3 -OAC7's., 2-6A G 7's. I-6V6. A of 26 tubes. Other 6H6, I- VR150, 2 -955, 2 -9004. Other components total parts -B such as relays, 24 V. dynamotor. transformers, pots, such as DP DT relay. 7 pots. 12 Am phenol 8318 chassis T -17 CARBON condensers. etc. make this a buy on which you can- connectors. and numerous condensers. toggle switches. not to wrong. Complete as shown in $ RF hokes. v iable condensers. and transformers. MICROPHONES Weight approx. 255 aluminum r case 18" X 7" X 714 ". `PO 7J lbs. Size 20"L x Il' 2'W $19.50 x 7?4"H. PRICE (Handmike) (New) $1.35

Unless Otherwise Stated, All of This Equipment Is Sold As Used CASH REQUIRED 130 W. New York St. WITH ALL ORDERS Indianapolis 4, Ind. Orders Shipped F.O.B. Collect RADIO -CRAFT for Jobs worth Which $3000 to $7500 Better Pay are opening up Greater Security Do You right now for A Nice Home FCC Licensed Want? Happy Vacations Radiomen A New Car and Travel How to Pass Commercial 'F C C Radio Operator LICENSE EXAMS GET YOUR F C C TICKET I can train you to pass your FCC License Exams in a fete short weeks IN A FEW SHORT WEEKS if you'yc had any practical radio ex- Get your licei ,artily and quickly perience - amateur, Army, Navy, and be ready for the $30011 to radio servicing or other. ItI time - $7500 jobs that are open to ticket NEW WORLD proven training plan can help put holders. CIRE training is the only 1a OF ELECTRONICS you, too, on the road to success - planned course of coaching and Natal Let me send you FREE the entire story training that leads directly to an Just fill out the coupon and retail it. I will FCC license. send von, free of charge. a copy of "How to Pas. FCC License Exams." plus a IT'S EASY WITH CIRE sample FCC -type Exam and Catalog A, describing opportunities for you in Radio- COACHING AND Elect rook,. TRAINING Elm. II. GUILFORD. Vice- President. Your FCC ticket is recognized in all radio fields as proof of your technical ability. Employers often give preference to license holders, even though a license is not required for the job. Hold an CLEVELAND INSTITUTE OF RADIO ELECTRONICS FCC "ticket" and the job is yours! RC -9 Terminal Tower, Cleveland 13, Ohio

km how I r l'l'1' tlrkel short t eeks. ud t cover lfor t. Iti.E (,,klrt, 'Alm to Ids, FIT 1.ie,nse Etamild ions" (does rut exam; dr to what these t mineur License,. as Nell as sample FCC -type canin and Catalog A. Olin.; Look students say: ,,,w uudt ies in Radio -Electronics "'l'h :inks to thin n , 111 w have a cary good jI]b it :I local poker plant's test department. I couldn't have obtained this job without the math and basic electrical theories in the first part of Section I of this course." Stud. No. 289.tN12 NAME "I have been working for Police Radio Station \VIFS in Asheville for five months since getting my second -class ticket." Stud. No. 2858N12 ADDRESS "You may be interested to know that I am employed at the local broadcast station, win re I am a transmitter operator. I took and passed the FCC examinations last February." Stud. No. 2754N12 1'ITY ZONE STATE CLEVELAND INSTITUTE OF RADIO ELECTRONICS D Veterans check for enrollment Information under G.I. Hill. NO OBLIGATION -NO SALESMEN. RC -9 Terminal Tower Cleveland 13, Ohio Approved frr Training under "G. I. Bill of Rjghts" SEPTEMBER. 1948 Radio 1i1isii1css

VIDEO AUDIENCE SURVEYED TELEVISION HELPS TAVERNS WarSurplusBargains Stanley H. Manson, advertising man- Bell Television, Inc., which rents sets ager of Stromberg- Carlson, revealed in to tavern owners, recently made a sur- a recent survey that 72', of the leisure vey in the New York Metropolitan area time which television owners now spend to measure results in this field. viewing their television sets was for- To the question, "Do you believe all merly spent listening to radio. By way bars will eventually have television of comparison, a recent survey of Foote, sets ?" 64% said yes, 19% said no and Cone and Belding, advertising agency, 17', were undecided. Fifty -seven per- shows that three -fourths of the televi- cent stated that television increased sion set owners interviewed are spend- business profit from 10% to 60 %, aver- ing more evenings at home. Slightly aging 165; ; 34% reported no change in more than half are going to the movies business; 9 "; noted a decrease. less often, although formerly they were Of all tavern owners interviewed, confirmed and in host cases very heavy 67% had television receivers. Of that movie -goers. group 70'; owned the sets while 30% Age of the television set did not ap- rented them. pear to have any relationship to reported in movie -going IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII - AN /PRS -1 MINE DETECTOR changes habits, which tends to discount the theory that televi- SPECIAL The detector is designed to detect metals. = AUDIO -SOUND ISSUE _ uniform:1,es crocks. tree-n,olsi and may be used sion's effect on evenings -out will dimin- to .lo.o t metal buried in logs, to locate cables. The October number will be a special sewer tile and etc. It widely used by ish as the novelty of the new set wears tits -:. miners. prospectors. plumbers. Audio -Sound issue. Articles on public treasurerrn mice off. = u.rtable _ device Used in the detection f both = address systems, noise reduction. bi- al:ir and n :allic by oral tear) and visual In the Stromberg- Carlson survey eye) means. These are brand i outfits, m = neural audio systems. electronic organs. nete with ins in inn book and spare tubes. Shipped in oriubml osuntas moisture-proof 60% were somewhat disappointed with = amplifiers. pickups and other audio- etiotainee. The set of the detector head with their sets (mainly poor programming), = sound equipment and accessories will ru f e for i metera housing and %r ruterusower section nor re,lsiu . trod. amplifier assembly, 82 judged the video picture image = feature this issue. Reserve your copy at rag nal s ,ciao bag to carry equipment while na woodenooden for "very good," 99% said they would buy a = your newsstand NOW! i or g complete unit when not In u set again, 35% are interested in buying weight. 145 lbs. Weight in operation 111111111111iiiiii1iii II IIIIIIIIIIIIIIIIIIIIIIIIIIr o n1S>hippings a second receiver, and 84% of all income natbNoa n nott included but wea c ai' supply them for SS.SO set. groups expressed a desire to own a tele- VIDEO TUBE PRODUCTION Price, brand new $14.95 vision set. Sylvania Electric Products, Inc., has Although 73'; now own table model entered a new financing program to aid MG -149F sets and 27' consoles, 51% of those in- in the expansion of cathode ray facil- INVERTER terviewed now want a console with all ities. "The rate at which television is services, and while 86% of the owners I Holt or -Cabot expanding makes it evident that more Elect. Co.) had receivers with 10 -inch tubes or Input 24 facilities will be urgently needed to meet V. DC smaller, 48% said they would insist on the demand," 36 amps. said Don G. Mitchell, Output a larger tube in their next set, with the president. I 15 V. 12- and 15 -inch most popular. Prices 400 eV. At the present time, in excess of 95% AC. 50.1 non -owners would be willing to pay is V. A. of cathode ray tube production is for O utpot considerably lower than the price range at 90% new television sets. Each set, however, satisfactory to owners. Thirty -five per constitutes a cent of non -owners future replacement mar- $12.50 said $400 or less, an- ket. This is just beginning develop other 35% said $400 -$600 to and 30% over and will grow as more sets come into 24V -L -3 50 AMP $600. The study also indicated that in use. 75% of Sylvania's expansion plans will be LEECE NEVILLE AIRCRAFT the cases the man of the house geared to both the new and the replace- GENERATOR made the purchase decision, a high per- ment markets." centage compared to the sale of radio combinations. Another interesting survey was made recently by Newell -Emmett Company, BUYING Of TV SETS INCREASES advertising agency. " Videotown- USA," An increase of 374 in the ownership a test television community has been se- of television sets from May 1 to June 15 lected to analyze the present television has been reported by Dr. George A. market and watch the growth of televi- Gallup's Audience Research, Inc. This sion over a period of time. Sets pur- represents approximately 354,000 sets. For Heavy Duty Work chased in Videotown, located on the From the same source it was learned 24 V L -3 -50 Amp -Levee Neville aircraft gen- fringe of New York's television area, erator for heavy duly is ork. Can lie nerd non auto- that an additional 5,400,000 families mobile, ate., for that 74V rig. tt-ei1 ht 24 lbs seem to be following the national aver- would be in the market for sets priced diameter-1r long Ia'- di to.. $17.50 1- length shalt. Brand new. age. The survey shows television owner- around $200, compared with a potential BC.133D LOCALIZER RECEIVER ship is in the middle -socio- economic market of 2,000,000 for sets at $400, the group. Nearly two out of three sets are average current price. It was estimated erase. in i i the Co ntrail. , Irtuto lit b r i lsl_n middle level. The actual break- that 1,000,000 additional families will Contains 10 tubes. Ihlee of nhlrh ale WE-717'.1 ' wn -anti crystal.. Ideal receiver for rouversInn shows that 60% of the sets are purchase sets within the next year, and 144 i h am I:and or mobile telephone hands in the middle class; 26% in the upper For 241 V. Dr 'petalinn. Size 141/2" a 7" c that the entire television area now cov- Pries with dynamotor $5.95 and 14'ír in the lower. These figures ers more than 11,000,000 families. Price without dynaina'w 54.95 compare closely with a survey made by television station WPIX in New York MIN TERMS: CASH WITH ORDER City recently. The percentage of home sets is in- RADIO FAMILIES INCREASE AMERICAN creasing rapidly. During the first half The Broadcast Measurement Bureau SURPLUS of 1947 41% were commercial installa- reports 37,623,000 United States fam- tions. By the second half it dropped to ilies now own one or more radio sets in PRODUCTS CO. 26 %. The first three months of 1948 good working order. This represents 537 N. CAPITOL AVE. home percentage increased to 91r/r and 94.2% of the total families and com- the commercial installations dropped pares with INDIANAPOLIS. IND. to 33,998,000 ownership, or 9 %. 90.4 %, in 1946. RADIO -CRAFT for 17

... MAKE THE SERVICE DEALER HAPPY ... Whether a replacement job calls for miniatures, standard tubes or the famous Lock -Ins, you can install Sylvania Tubes with complete confi dence.You know they'll give the kind of performance that builds good will among your customers! And... don't fail to cash in on Sylvania's national advertising. Make full use of the Radio Serviceman's decal -your decal - featured in every single one of Sylvania's national acts! ... BECAUSE THEY KEEP SET -OWNERS HAPPY!

DISPLAY THE DECAL THAT BRINGS CUSTOMERS Sylvania Electric Podr.cts Inc. Radio Tube Division TO YOU! Advertising Dept., Room R -1309 Emporium, Pa. Gentlemen: Please send, FREE, the following quantities of the Sylvania Serviceman's decals: SYIJVN IA 8 -inch sise 12 -inch decals Name Company ELEGIR! C Street Address City Zone # Radio Tobe I)irisi.,, r. Emporium. Pa: State MAKERS OF RADIO TUBES: CATHODE RAY TUBES; ELECTRONIC DEVICES: FLUORESCENT LAMPS, FIXTURES, WIRING DEVICES; ELECTRIC LIGHT BULBS L SEPTEMBER, 1948 War Surplus Bargains Sold As Used Unless Otherwise Specified! MN/

C -1 AUTO PILOT C -1 AUTO PILOT AMPLIFIER i CONTROL BOX Used to control operation of servo unit in response to signals received from gyro Used for aligning control of unit and control unit. The complete am- C -I Auto Pilot or use for

plifier includes one rect. 7Y4, 3 -7F7's parts, etc. Contains many

for amplification and control, 3 -7N7's useful pots., toggle switches,

plugs, etc. Size, I i x a for signal discrimination, I power trans- " 6" former, 6 relays, 4 control pots, chokes, 41/2 ", PRICE condensers, etc. Convert for use on radio controlled models, doors, etc. Operates $3.75 from 24 V. DC. Size, 91/4" x 61/4" x 75/er,

ROTATOR AIR MOTOR COMPRESSOR FOR YOUR Made by Cornelius Mfg. Co. BEAM Will pump pressure up to

ANTENNA 1500 lbs. per sq. in. 3 -stage type- air -cooled, powered by a 24 V. DC motor. Ideal in 1495 shop for use with airgun, small paint sprayer, and numerous As pictured on left other applications. Small, compact, 21 -32 V. AC or DC operated. Reversible- -only 3 wires rcgt'iled. APpro ximatel. a1 precision - built itI'M. 7056 to 1 year reduction (no free swing,. Powerful motor. Huge.' l'rer,,iun pear train, and sturdy thrust ben r.og will support and turn ally ha. Only '12" beam. Weather -proof housing. Motors are easily converted into an F'lt ¡KIM COW or I Conversion data included. Motor with antenna nu/tinting plates welded Id" 66.110 Selsyn transformer for Selsyn indicators, 110 V. AC input, 25 V. AC /allow Tra n stn rmer tar beans motor, 110 V. A('' input, 2 -12 v. Secondary ss r Itatirg II amps >1.'.-

2 -METER BEAM ANTENNA Portable or fixed, manually operated or can he used with beam motor, fur use in 13.1 -17,6 Mr. band. Easily adapted fur ham or experimental use. Contains tuning unit wh ieh matches ou 1pul of transmitter to antenna. 18' steel mast with brass tube containing t - cable and fitting- inside steel mast IOD colon, "H" frame fro T -26 APT -2 RADAR holding dipoles, 3 sets t 1 per sett dipole rods. TRANSMITTER compensator or sense stntennn for "H" tram.. Contains tunable VHF circuit using 2 -IAN CTL 2 steel truncated runes used as antenna soup., 713A's or 368AS tubes. Other tubes are: 2 -5 RAG V's. and feed- through, 360 degrees bearing indicator. I -2X2. 1 -807. I -6AG7. 2 -6AC7's. and I -631 A. and -wheel for rotating. Other parts such as 24 V. DC motor and blower. HV. hand condensers and transformers. terminal strips and Am- Brand new packed in -ix boxes, total weight phenci connectors, knobs. fuse holders. etc.. make this approx. 600 Ile,. Limited quantity and in much unit invaluable tor parts alone. Weight approx. 45 lbs. Size 21-1. s 1012-W x 7', "H. tscmand. Place order now. in metal case. $9.75

PRICE $79.50

TURBO AMPLIFIER Used for wets- shipped comp:13 e with the fallowing tubes: ti 2 C5's 7 l' t PP- 2 'APQ -5 POWER UNIT 7 F7 400 cycle. 115 V. Contains 10 tubes as follows 2- 5U4G's. 1- 6X5GT. 4-6V6G's. 1-6S L7 GT. 2 -V R150- Price $1.75 ea. 30's and numerous condensers. transformers and sisters. Weight 17 lbs. Sire 21 "L X 513 "W x Telephone LINCOLN 8328 733 "H. PRICE 'V$5.75

TERMS: CASH WITH ORDER ARGON INCANDESCENT LAMP MICRO SWITCHES 2 watt pear sha see with regular AC type sere, ^sucked 10 AMERICAN SURPLUS hase. New per ea,tin. SI' i./.pc normally closed. 25c each Price per carton PRODUCTS CO. $2.35 537 N. CAPITOL AVE. ALL PRICES F.O.B. INDIANAPOLIS INDIANAPOLIS. IND. RADIO -CRAFT f,or 19

NEW SERIES 16 SUPER DE LUXE Or AM -FM CHASSIS

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Here is the last word in radio engineering ... a powerful, world - ranging, magnificently -toned radio that r is unsurpassed for performance, selectivity, sensitivity, and advanced engineering features. Uses these latest -type tubes, rectifier and tuning indicator: three 7A7, three 7A4. two 7C5, one 7A6, one 7Q7. one 6BA6, one 6BE6, one 6C4, one 6AL5, one 5U4, one 6U5. Comes corn- plete with satin stripe copper finish front panel attached, Magna - Tenna Loop Aerial and giant 141/2' Electro- Dynamic Panasonic Speaker. Requires only a few minutes to install, plug in and play. LOW FACTORY PRICES ... EASY TERMS ... 30 DAYS TRIAL. Send TODAY for FREE 1949 Midwest Radio Catalog of separate Chassis and beautiful Console and Table models. OUTSTANDING A Complete Line of FINE RADIOS and RADIO - FEATURES in SEPARATE Including the PHONOGRAPHS ... Available Exclusive Midwest CHASSIS Like the POWERFUL SERIES 16 AM -FM FLASH- O -MATIC Model above or in COMPLETE CONSOLES like this... Volume and Band Indication Beautiful TELEVISION Audio Switch -Over

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RECORD CHANGER ...Plus NO -DRIFT FM A Magnificent musical instrument and and many other features a masterpiece of cabinet design - the finest Midwest Radio in 29 years of manufacture. Offers world- ranging radio reception and newest automatic Intermix Record Changing Phonograph. Uses Series 16 Super DeLuxe AM -FM Chassis. Giant 14%" Panasonic Speak- er; TriMagnadyne Coil System; Built - FILL IN COUPON AND MAIL TODAY OR JUST In Loop Antenna. Other luxurious con - SEND NAME AND ADDRESS ON Is POSTCARD sole and table model cabinets available with Series 16, 12, and 8 chassis on MIDWEST RADIO & TELEVISION CORP. Easy Terms and 30 Days Free Trial. Dept.381,90Y Broadway, Cincinnati 2, Ohlo BUY DIRECT FROM FACTORY and SAVE! Please send m your new FREE 1949 Catalog., NAME

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Dept. 381 909 Broadway, CINCINNATI 2, OHIO CITY ZONE _. STATE V d SEPTEMBER. 1948 20

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Yes, its better for you and your business to buy where this banner is displayed because the SPRAGUE BANNER identifies a Dis- tributor who agrees that "It's foolish to play penny-ante when your business is at stake!" Your Sprague Distributor is a successful business man. He knows the parts business intimately -and he knows that to really build a bigger, more successful service business, you should use only the best replacement parts. That's why he features Sprague SPRAGUE EL SELF- MOUNTING MIDGET CAN CAPACITORS Capacitors and *Koolohm Resistors. His business dePaends on No other Dry Electrolytic gives so much de- your success and he wants you to remember that YOUR REPU- pendability in so small a space! Tinned, Twist -Prong Tabs for easy soldering; quick, TATION AND YOUR CUSTOMERS ARE TOO VALUABLE universal self -mounting. SAVES TIME - SPEEDS RELIABLE SERVICE! TO RISK FOR THE FEW PENNIES "SAVED" BY BUYING INFERIOR OR UNKNOWN "BARGAINS "!

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I OOLONM CAPACITORS RESISTORS SPRAGUE T M Rrc u sr,i on SPRAGUE PRODUCTS CO., North Adams, Mass. (JOBBING AND DISTRIBUTING ORGANIZATION FOR THE PRODUCTS OF THE SPRAGUE ELECTRIC COMPANY) RADIO -CRAFT for Editorial 21 SOVIET RADIO LAND -TORPEDO

v4 novel radio- telenleclíanic war means .. .

By HUGO GERNSBACK

DURING World War II the Russians employed a fled and passed on to a system of three accurately tuned unique type of radio land mine which was used relays. Only when the three exactly registering pulses extensively against the Germans. Very little about open a special cipher circuit is it possible to operate the it has been published up to now. We are indebted to the detonator, which then explodes the mine or mines. French periodical La Nature, from which the writer has The transmitters used were standard abstracted Russian types. the following highly informative account: In order to explode the F10 mines, these transmitters Up to a few years ago it was common practice to stop had to send out special low- frequency impulses. The sig- advancing enemy troops by blowing up buildings and nals were sent four seconds apart. fortifications by means of time bombs. The French The F10 wreaked tremendous havoc population well remembers the terrible explosions which against the Wehr- macht. This continued for quite a while until by accident took place regularly several days after the Nazis evacu- three installations were found intact. Now there began ated French cities. No sooner did the city go back to a technical war against the Russians. It was soon its routine life than public buildings began to blow up, found that by using special amplifiers the clockwork could be terrorizing the population. These explosions in most heard up to about 20 feet, whereas without cases were set off by clockwork or by the well -known amplifiers it could only be heard about 1 foot away. Detection means of slow working acids which corrode metal work, dia- however, was exceedingly difficult and nerve- phragms to activate the explosive charge. racking for the Germans, who knew that at any instant a Rus- A much more up-to -date means was used by the Rus- sian commandotransmitter might start transmitting sians beginning in 1942, with their radio mines, type and blow up F10 in their faces. F10. Even after F10 had been located, it was absolutely F10 is a square metal housing which contains a radio necessary to act with lightning rapidity, as in any receiver to which is attached an antenna 100 long. ft. given moment whole blocks could be blown up by Connected to or the the receiver are one more mines. distant Russian commandoradio transmitters. The an- A Russian model known as BIS could explode 36 mines tenna had to be located quickly so it could be cut as close simultaneously. These mines were electrically connected to the receiver as possible in order to reduce the sensi- with each other. The various mines are placed about 50 tivity of the buried receiver. Then the batteries had to yards distant from the commandoreceiver F10. By be disconnected, the clock mechanism put out of order, using an auxiliary amplifier type, BEREDO, it is pos- and the special mechanical delay detonator made harm- sible to separate the mines a great deal farther. less. Naturally, only specialists could do this tremendous- The receiver is housed in a waterproof rubber sack ly difficult work. to keep out moisture, rain, etc. The whole is buried to The Germans evolved many countermeasures, but a depth of about 10 feet. The mines themselves can be finally the following proved effective. Using 20 different placed in the ground or under walls, into foundations, receivers the Intelligence Service tried continuously to etc. intercept the special signals. Using two special 100 - The antenna is camouflaged carefully somewhere watt transmitters operating continuously, the Nazis along the wall. F10 is equipped with an ingenious me- began sending out counter signals on exactly the same chanical device. If technical trouble develops and the frequency. Two reserve transmitters also of 100 watts . mines should not function, the entire radio receiver is stood ready to take over in case the first two should be destroyed so it cannot fall into enemy hands. put out of commission. Further, a 11/2 kw transmitter The installation uses a 12 volt storage battery for stood by in order to blank out the Russian signals with "A" current and a 90 volt "B" battery. Using a special powerful counter transmitters. This Störsignal (counter clockwork, the receiver is put into operation every five signal) was transmitted as long as the Russian trans- minutes, but only for 10 to 15 seconds. This safeguards mitter was on the air. The Russians countered the Nazi the installation in many ways and conserves batteries. means by increasing their transmission power over Thus, it is possible to operate the F10 for as long as 40 11/2 kw to blank out the Germans in turn. days after it has been installed. In practice, however, the Germans-usually being The distant transmitter sends out a series of pre- nearer to the buried receivers-were able to come out on cisely defined signals. At the receiver they are ampli- top in this interesting radio battle. SEPTEMBER, 1945 Electronics

..+¡,r'i %j; S ::,: ;.:,. '. :.-.t-:::- r.::a.tr,ti±=.t: i(tr,.J-::::¡Siii.-j.l::%?; ; ..r:r..+::) :sr 1t,¡' +; ¡:i;i:i!rtY fF¡ =:}-.. ii.r; ..,. :%::%ts`'Y.i:j: ,t:.vj.;C.....p.. i: y .4<¡-...4.--.1-.%:", _ Zti...;.... 1-. ..: : :i ' ':L«Jÿÿ:V' 'S,A ::.: ... %'jr ,. j '.r J`; i? rtJ. íJ:.'S :! ' r : ... r;r..r S nV1nÌ.rf :. : ~ ' :.... : J .

zr,$'--'er.;.-:%y.l -. :ñ: -. s .

.: Electronic :^4k!. +' Osculation Indicator

Y C- By LYMAN E. GREENLEE

e!}-Tl < +t aJ A11 -yy-. ,'7T,lrja j ,-M~.fS%` '-¡` ..: -'t'.. _rs-,:- ' .-i..;;. .Li 'f i:rR.:S":ri 'R .. : THE Kiss Meter is a scientific in- 400 -cycle current for making the im- The power supply uses a 7Y4 con- stument designed to measure oscil- pedance measurements. A small push - nected as a half -wave rectifier and a lation reaction. With it you can tell pull output transformer was used, with small power transformer from a midget whether blondes have more resist- the 6J5 cathode connected to the center radio. If a center- tapped transformer is ance than brunettes or redheads. An tap of the secondary. No capacitor was used, half the secondary winding may be adept Lothario can probably find this necessary across the secondary winding disregarded. Since there was no sepa- out without the aids of science, but the with the particular transformer used, rate filament winding for the rectifier on meter gives us a good insight into bio- but some transformers may require the power transformer used in the logical electronics. about .005 pf. The output is taken from model, all the tubes were operated from The meter measures the a.c. imped- the voice -coil winding. This keeps the the same 6.3 -volt secondary; but, if a ance of the human body at a frequency voltage low enough so that little or no separate winding is available for the of about 400 cycles. Two electrodes shock can be felt. Some transformers rectifier, it should be used to avoid ex- formed of spring brass or copper are may not work successfully in this cir- cessive voltage between heaters and shaped to fit the wrists of the two per- cuit. In case of difficulty try another cathodes of the other tubes. Note that sons undergoing the test. The electrodes transformer. the output from the power supply is con. are connected to the meter terminals. The applied a.c. voltage is very small, and this reduces the possibility of a dis. agreeable shock to the experimenters. Actually there is little or no sensation to be felt, although a very sensitive person will usually imagine that there is a slight tingling effect. A vacuum -tube voltmeter is required for adequate sensitivity. A balanced bridge circuit was chosen to insure stability. A large cabinet happened to be on hand. Its use makes the instrum nt look impressive, but there would be plenty of room in a smaller case. As Fig. 2 indicates two 6J5's are used in a bridge circuit with a 0 -200 or 0 -500 microammeter to form a stable, highly sensitive vacuum -tube voltmeter. If a 0- 500 -iza meter is used, the 1,500 -ohm shunt will not be needed. A special scale (shown in Fig. 1) was drawn for the meter on white bristol board and colored to represent six degrees of osculatory intensity: 1 white, 2 blue, 3 green, 4 yel- low, 5 orange, and 6 red. This covers the whole emotional range from "frigid" to "torrid." A third 6J5 is used to generate the Under- chassis view of the Kiss Meter. Sensitivity control is at back, zero on chassis. RADIO -CRAFT for ßlectromics I 23

BIOLOGICAL ELECTRONICS By HUGO GERNSBACK WHEN the accompanying article not been investigated too seriously. pected, pressure affects the resist- by Mr. Greenlee was first re- Dr. G. W. Crile has demonstrated ance. So does lipstick, which some- ceived, it was thought that its publi- that the human life stream is con- times increases the electrical resist- cation might strike some individuals tinuously discharging electrical po- ance, depending on the type used. as too fanciful. But, biological elec- tential. It is a fact that many parts Moisture, of course, lowers the re- tronics being something rather new, of the human animal are actively af- sistance a great deal, the degree de- I believe it deserves a great deal fected by galvanotropisnl- response pending upon the nature of the more publicity. There is much to be of living things to electric stimuli. moisture. If the lips are moistened learned about the effect of disease on It has been shown experimentally with the tongue, the resistance varies the human anatomy, and it is quite that during the act of kissing there greatly with the state of health of possible that in the future we may is an actual exchange of electrical the individual as well as with what j investigate many diseases and ill- potential as well. Although only a foods had been ingested. Thus, for nesses by means of electronics. weak current, it exists nevertheless. instance, the lip response of an in- Karl Friedrich Burdach, German Some years ago the writer did dividual was measured before and physiologist and biologist, probably some research work along these lines after drinking lemonade. After was the first scientist to investigate and the following were noted: drinking this acidulous liquid, the human osculation. He defined it as a To begin with, lips are covered resistance of the lip skin fell almost "Galvanic contact between a positive- with a mucoid membranous skin. This to the lowest point. ly and negatively electrified body: it very sensitive skin is subject to many It was also found that emotions increases sexual polarity and per- and varied influences. In different greatly affect electrical resistance meates the entire body." individuals and in different races, of the human lip skin. Thus, fright Since this early pronouncement, for instance, the thickness varies a -as is well known -dries up mucoid nearly 100 years ago, other scientists great deal. Speaking generally, the skin, and under this influence the have preoccupied themselves with the male lip has somewhat thicker skin resistance went up enormously. We subject, particularly on the basis of than the female. Age changes the all know from experience that during sexual selection. The propagation of thickness and consistency of this great emotional stress, such as fright, the human race depends upon many skin a great deal. Repeated measure- shock, etc., most individuals auto- factors; and many of our senses are ments with an electrical potential matically lick their parched lips, involved in this selection, be they have shown that the electrical re- which have become almost completely visual, oral, or tactile. Osculation is sponse of the lip skin varies over a dry with an accompanying increase one of these, and up to now it has wide range. Thus, as might be ex- of electrical resistance.

nected to a voltage divider to supply FILS about 150 volts positive plate potential, M7VAC and 80 volts negative bias. No filter, T` 1AA other than the single 8 -µf electrolytic s 7Y4 270K 5 6J5(3) capacitor and the two 2 -µf electrolytics, MIDGET +70V 25K/2* 10K %2W POWER TRANS is required. Larger capacitors can be C.005/500 used, but they are not necessary. H1 +1001 A 1- megohm potentiometer shunted 450V +150 20K/IOW 105/104 25K/2w 5K O with a 250,000 -ohm resistor controls the ww but a 200,000 -ohm po- ww WW OUTPUT TO ARIA ELECT input sensitivity, a0V 1.55' .5.200V may be used without the re- SEE TEXT tentiometer 2/300V SOV 0200pA sistor. The 5,000 -ohm zero -adjustment 0-SOquA potentiometer should be wire- wound. e00V 7.55 Fig. 2 shows two .005 -pf capacitors A OSC +70V iI connected across the input of the power $ 1005 25K/2W transformer and grounded to the chas- connected sis. A single .005 -pf capacitor i OUTPUT TRANS directly across the line may also be tried.. The meter is very sensitive and has a With some transformers, the oscillator plate may need bypassing to ground. tendency to respond to any 60 -cycle a.c. Fig. 2- Schematic. voltage introduced between the chassis and either side of the power line. In adjust the zero point of the meter with resistors, etc. For such purposes a some cases it may be necessary to re- the arm electrodes disconnected. The 1- multi -scale instrument would perhaps verse the a.c. line plug or have the users megohm potentiometer is used to set the be desirable. The author has not tried stand on rubber matting. sensitivity so that the meter reads full - to adapt the instrument to the service The photographs show the wiring and scale with the arm electrodes shorted to- bench, but the idea is attractive. placement of parts. The correct voltages gether. These are the only two adjust- at various points in the circuit are indi- ments required and they will rarely need cated in Fig. 2. These voltages were all to be altered, as the instrument is very measured from chassis using a 1,000 - stable in operation. ohms- per -volt meter. If correct voltages To insure adequate contact with the do not appear, vary the resistors in the experimenter's wrist, it is a good idea to voltage -divider circuit until voltages are dampen the spring contactors with a lit- correct. It may be necessary to insert tle salt water. Small wads of cotton an additional resistor in series with the soaked with salt water or vinegar can 20,000 -ohm bleeder to cut the plate volt- be inserted between wrist and wrist- age at this point to 150. bands for better contact, if necessary. The two controls that require adjust- The instrument was constructed for a ment are mounted, one at the rear and specialized purpose, but the circuit one on the top of the chassis, to pre- might find much wider use. It is an a.c. vent tampering with the calibration. impedance meter, which could easily be The 5,000 -ohm potentiometer is used to used to check inductors and capacitors, The chassis is much smaller than the cabinet. SEPTEMBER, 1948 rr1'i111s11l 111'-j,¡1`l'111í111111111 1'l'y`i ill 1/s1'Illi1i1's and amplifies

THE beginning of the end of an era contacts and the germanium crystal can 10 megacycles is the present upper limit. in radio -the era of the vacuum be clearly seen. The second limitation is the amount tube-was heralded on June 30 The implications of this development, of power which can be developed in the when the Bell Telephone Labora- once it emerges from the laboratory and units. This is 50 milliwatts. However, tories demonstrated a simple, revolu- is placed in commercial channels, are the maximum frequency and power tionary replacement for the vacuum staggering. No longer will it be neces- limits of the transistor have not yet tube. sary to supply power -whether it be by been explored and it is quite probable Although still only a laboratory de- batteries or filament heating transform - that with the knowledge gained from velopment, this device, known as a tran- ers-to heat an electron- emitting cath- more experience in their use and manu- sistor, will do everything that the con- ode to incandescence. The transistor re- facture, both figures will be raised. ventional vacuum tube can do, i.e.: quires only two low -voltage, low- current A table model radio broadcast receiv- amplify and oscillate. Yet, it consists bias -voltage sources to operate as an er using no vacuum tubes was demon- of nothing more than a tiny piece of amplifier or oscillator. Lighter and strated. This receiver was a modification germanium crystal (similar to the smaller pocket radio sets will be one of of a commercial vacuum -tube receiver. 1N34) soldered to a metal base with obvious results. Cheaper receivers will purchased in the open market. two phosphor bronze or tungsten points be possible because of the elimination of Another tubeless set -the equivalent spaced only .002 inch apart making con- heater and filament circuits. of a line -operated 10 -tube conventional tact with the top surface. The whole is The first transistors have voltage broadcast superheterodyne receiver - inclosed in a metal cylinder less than an gains of approximately 10, roughly the was also demonstrated. inch long (see Fig. 1). The device oper- equivalent of a medium -mu triode. In another demonstration a two -stage ates at normal room temperatures, and There are two limitations on the use video amplifier incorporating two tran- -unlike the vacuum tube -requires no of the transistor at the present state of sistors was connected in series with the cathode heating or vacuum. its development. video line to a television receiver moni- A cross- sectional view of the device The first is the maximum frequency tor to illustrate the low- distortion wide - is shown in Fig. 2. The two hair -thin at which it will operate satisfactorily. range amplification of the device. Fig. 3 shows a complete plug -in audio oscillator unit. The unit contains a transistor, a transformer, two condensers, and two resistors. The four -prong tube base of this unit connects to the necessary batteries and to a loudspeaker. This unit performed exactly the same as a vacuum -tube audio oscillator. Transistor circuits As far as circuit applications are concerned, the transistor may be compared to the conventional vacuum tube triode.

Fig. I -This photograph shows how small the amplifying unit is. The crystal and the two contacts are enclosed within a tiny cylinder. Electronics 25

In fact, the transistor is defined as a semiconductor triode. Fig. 4 is a simplified schematic diagram of a typical amplifying circuit using a transistor. The circuit looks very similar to a conventional triode circuit, if the emitter contact is considered as the control grid and the collector contact as the plate, with the semi -conductor base as the cathode. Unlike the vacuum tube, however, the emitter contact is biased with a small positive voltage (1 volt) while the col-

SIGNAL SOURCE_r _ LOAD EMITTER OLLECTOR I

I.V I 45,1 the emitter and the collector is about TRANS 15705 spacing de- + .002 inch. Increasing the creases amplification. The "area of in- Fig. 4 -This is basic transistor amplifier. teraction" extends out to a distance of point. Fig. 3- Transistor plugs into a tube socket. about .01 inch from the emitter lector (or output) contact is supplied If the negative collector bias is made with a negative potential of approx- large enough to make the collector cur- imately 45 volts. fact that electrons in a semi -conductor rent equal to, or larger than the emitter Another fundamental difference is can carry current in two distinctly dif- current, the polarity of the collector bias that the input impedance of the tran- ferent ways. This is because most of the will attract the holes flowing from the sistor is low, ranging from 200 to 1,000 electrons in a semi -conductor do not con- emitter (Fig. 6 -b). Then a large part of ohms. Output impedance ranges from tribute to carrying the current at all. the emitter current flows to (and enters) 10,000 to 100,000 ohms. Thus, the tran- Instead they are held in fixed positions the collector. While the collector has a sistor can be matched to a high imped- and act as a rigid cement to bind to- high impedance to the flow of electrons ance load. Because of the low input im- gether the atoms in a solid. Only if one into the crystal semi -conductor, there is pedance it will be necessary to use spe- of these electrons gets out of place, or little opposition to the flow of the holes cial input circuit arrangements. if another electron is introduced in one into the collector point. If the emitter Gain can be varied by varying the current is varied by feeding in an a.c. amount of bias applied to the emitter signal, the collector current varies cor- contact, much as gain in a triode can be respondingly. The flow of holes from the varied by changing the grid bias. emitter to the collector may alter the The transistor can be used in any type normal current flow from the crystal of oscillator circuit where a vacuum base to the collector in such a way that tube triode can be used. Fig. 5 shows one + - oscillator circuit. + EMITTER Fig. 5- Transistor replaces oscillato tube. Transistor development The transistor is the outgrowth of ex- of a number of ways, can current be periments and theoretical studies of carried. If, on the other hand, one of the BASE semi -conductor phenomena by Dr. Wil- electrons normally present in the cement a b liam Shockley of the Bell Telephone is removed, then the "hole" left behind Fig. 6 -This shows how transistor amplifies. Laboratories, assisted by Drs. Walter it can move like a bubble in a liquid and thus carry current. the change in collector current will ac- Brattain and John Bardeen. in In critically examining the implica- Fig. 6 -a represents a cross -section tually be larger than the change tions of the prevailing theory of electri- of a germanium crystal with a positive emitter current; in effect, amplification. a point contact cal conduction in semi -conductors, Dr. voltage applied through Historical background Shockley was able to predict that it (the emitter). a O. Lossev, should be possible to control the meager The current flow under this condition In 1923 Russian, V. supply of electrons inside a semi-con- does not fan out from the emitter con- claimed to have successfully caused a ductor by influencing them with an elec- tact point through the body of the crys- crystal detector to oscillate and amplify. tric field imposed from the outside with- tal material to the base, but instead An account was published in the Sep- out actually contacting the material. spreads out widely over the surface of tember, 1924, issue of one of Hugo Realizing the practical implications of the crystal somewhat like water spreads Gernsback's former radio publications. such a possibility he devised some ex- out on top of a non -porous surface such Unlike the transistor, this arrangement periments to test his hypothesis but was as glass. This current flow across the (called the crystodyne) made use of a unable to secure positive results. The surface is carried by the holes. 2- contact crystal detector and relied electrons seemed to get trapped in the The amplification process can be un- on special circuits to get the desired re- surface of the material and did not be- derstood in terms of the discovery that sults. Results were poor. have just as anticipated. the emitter point is surrounded by an In the early part of this century Dr. This part of the problem was tackled "area of interaction." Within this area Greenleaf W. Pickard produced oscilla- on a theoretical basis by Dr. Bardeen. the electronic structure of the semi-con- tions with a crystal detector circuit. He developed a theory of what hap- ductor is modified by the input current. The circuit, however, was impractical. pened at the surface which was able to Now, if the output point (the collector) Pickard said: explain satisfactorily many of the ob- is placed in this area and a negative "Any contact which doesn't obey served facts and which led to further bias applied to it the output current can Ohm's law can be used to produce oscil- experiments carried out in collaboration be controlled by the input current. This lations. A crystal rectifier can also be with Dr. Brattain. In the course of these control of output current by input cur- made to amplify- although the simple experiments they invented transistors. rent is the basic mechanism of amplifi- contact must be changed to something Transistor action depends upon the cation. The optimum spacing between more complex." SEPTEMBER. 1948 26 Electronics TheI'll Crystal Detector Part III -Modern crystal cartridges

By JORDAN McQUAY

THE technique of high -frequency metal conductor and the semiconductor. For all of these functions, where the rectification with crystals or min- The barrier permits a flow of electrons operating frequencies are on the order erals is almost as old as radio itself. from the semiconductor to the metal of 1,000 to 25,000 mc, only silicon in crys- Beginning in 1902, Pickard and wire, but prevents electron flow in the talline form is a satisfactory semicon- other pioneers developed the crystal de- opposite direction'. ductor. tector which, until supplanted by the This rectifying action is made pos- Silicon is a nonmetallic element, with more efficient vacuum tube', was the sible by the inclusion of a small per- a melting point of about 2,600 degrees F. chief means of radio reception. Decades centage of certain impurities, sometimes Although it is one of the most abundant later, modernized and improved crystal known as doping ingredients, in the elements, it is never found free in na- basic, bulk material, silicon or germani- ture. The pure crystalline form, ob- TUNGSTEN WIRE um. Conduction depends upon impurities tained by chemical reduction, is a sil- on the order of 0.1%. By rigid control very, brittle substance in the form of of these impurities, the characteristics globules or 6 -sided pyramids. Pure sili- of a contact rectifier can be altered to con crystal, however, is not suitable as satisfy any electrical requirement '. `. a semiconductor. Besides bettering the performance of ex- A crystalline form is first obtained at XTAL isting types of rectifier cartridges, 'm- a high temperature from silicon tetra- ANODE chloride. The silicon crystals are then melted in a vacuum, and this melt CATNODE' 10 iiiiiiiiUiii to IIMIlliliIliII small impurities are added, according to my NMI the intended use of the finished product. Fig. I- Construction of the crystal rectifier. 25 11sisiss/MEE For microwave mixing or frequency conversion, aluminum, beryllium, sole MIMI and rectifiers returned to become the CURRENT IN MILLIAMPERES Il boron are added. For video detection, method of frequency conversion for nickel and germanium, with extremely 20 11 microwave superheterodynes'. So suc- small amounts of bismuth, calcium, and cessful were these rectifier cartridges cobalt, are mixed with the bulk silicon. that other types were soon developed for have IS 'l11 After the impurities been added, radio and other rectifying purposes at si si s s si si the substance is cooled and sawed into audio frequencies as well as at power Fig. 2- Front -to -back 1 sections about 1 mm thick. Both sides frequencies. voltage - current ratio MUM.. of a standard german- 16 of each section are fairly well smoothed, All modern crystal cartridges are es- rl ium crystal detector. but one side is finished and polished. sentially point -contact rectifiers (Fig. ioIMEW MEE. Next, the contact surface is given an 1) having a small -area contact between 11/sisiM oxidizing heat treatment'. Each slab is a wire of tungsten or similar metal and S heated for several hours until a blue a semiconductor of either silicon or ger- iilïiiiiiiii color appears, indicating the formation manium. IIIE of a thin oxide layer. During this oxi- Semiconductors constitute a special dizing period, various impurities in the class of materials between conducting i'i -YT, r I I I I I _ .5 L silicon diffuse into the adhering silica NEG. APPLIED VOLTAGE 2 I.POS APPLIED VOLTAGE and nonconducting solids. They have a high electrical resistance, between that proved methods of doping semiconduc- of metals and insulators, and are much tors have led to many different crystal more sensitive to the presence of im- types for various circuit applications. purities than are metals. See Tables 1, 2, and 3. If small amounts of certain impurities are added to either silicon or ger- Silicon rectifiers manium, the resulting material can be A majority of the modern types of made to function nonlinearly (not in ac- crystal cartridges (Fig. 3) developed cordance with Ohm's law) when placed during and since the war are for use in contact with a suitable conductor of as mixers or frequency converters in fine wire. The nonlinear characteristic microwave superheterodyne receivers. is decidedly polarized, as shown in Fig. (See Table 1.) Also, numerous types of 2. This curve reveals an important rectifiers known as video detectors have characteristic: the back -to -front ratio been developed for direct demodulation determined by the resistance of the rec- of microwave signals, without the use and back directions. of a superheterodyne tifier in the front circuit. (See Table Typical crystal for converter stage. Rectification takes place across a po- 2.) And one type of crystal cartridge, Fig. 3- tential barrier produced at the contact the 1N22, is an instrument rectifier for film, decreasng the amount of impuri- point of the semiconductor, due to the microwave test and measuring equip- ties on the surface of the silicon. The difference in functioning between the ment. oxide layer is removed by a solution of RADIO -CRAFT for Electronics I27 dilute hydrofluoric acid. The underlying manium crystal cartridges are far more For efficient low- frequency rectifica- layer of silicon is exposed and remains efficient for that purpose. tion with high inverse voltages, anti- intact, as the acid does not readily at- mony and tin, with extremely small tack the silicon. Any decrease in the im- Germanium crystals amounts of calcium, nickel, and stron- purity content of a semiconductor in- The need for crystal rectification at tium, are added to the bulk germanium. creases its resistance. Thus, the silicon lower frequencies and at higher power These combined impurities total less surface has a higher resistance than led to the development of the germanium than 0.1g . of the whole. before the oxidizing treatment. The pigtail cartridges. After melting and cooling, the sub- characteristics of a silicon rectifier are Existing types of germanium recti- stance forms diamond -shaped crystals. governed by the resistance of the semi- fiers can be operated at any frequency The ingot is sawed into wafers about conductor, the area of contact, and the up to about 250 me with a maximum 0.6 mm thick. Each wafer is polished on degree of surface oxidation. back voltage of 200 and a safe maximum one surface, and then cut into four In general, silicon rectifiers are con- forward current of 150 ma. (See Table squares, 3 mm on a side. Next a crystal fined to very -low -power circuits, usually 3.) Improved types now under develop- wafer is silver -soldered to one wire of on the order of 1 watt or less. ment will withstand inverse voltages up the cartridge, and placed in contact with Although silicon could be treated for to 250. a tungsten or platinum point. The iso- use at much lower frequencies, ger- The tiny cartridges are used as sec- lantite cartridge is wax -filled to main- ond detectors and d.c. restorers in tele- tain correct adjustment and make the vision receivers, modulators and de- unit moisture -proof and shock -proof. TABLE 1 It is reasonable to believe that within SILICON RECTIFIER CARTRIDGES modulators, voltage regulators, discrim- inators in FM circuits, volume limiters, a few years there will be sufficient types (for frequency conversion in microwave of germanium rectifiers to supplant all superheterodynes varistors, meter rectifiers, noise si- lencers, and in other applications. vacuum -tube diodes, with a consequent saving in cost, weight, volume, and fila- ás A matched unit, known as the 1N35 EiEû t9 d3 t- duo -diode, consists of two almost iden- ment power consumption. I-E t; d3 óá at d: tical germanium rectifiers in a single References E two diodes are 1. The Crystal Detector by Jordan Mc- ÿg vi so áó >á m á mounting (Fig. 4). The F. om zrX IT, ZZ <: i= matched for values of forward and back Quay, RADIO -CRAFT, July, 1948. 2. The of Crystal Rectifiers by 1N21 3,000 Low 8.5 4.0 0.4 1.0 resistance (within 10'at 1 volt), and Return are particularly desirable where full - Jordan McQuay, RAino-CRAFT, Aug., Medium - 1N21A 3,000 Low 7.5 3.0 0.4 1.0 wave rectification is required in a bal- 1948. anced circuit. 3. Theory of VHF' Rectification by Sili- IN21B 3,000 Medium 6.5 2.0 0.5 1.0 The highly polarized, nonlinear char- con Crystals by H. A. Bethe, Rad. Medium - acteristics of all these crystal diodes are Lab. Report 43 -11, MIT, 1943. IN21C 3,000 High 5.5 1.5 0.5 1.0 due essentially to the use of germanium 4. The High- Voltage Germanium Recti- 1N23 10,000 Low 10.0 10.0 0.1 1.0 (with certain impurities) as a semi- fier by S. Benzer, NDRC Report 14- 342, Purdue, 1944. Medium - conductor in contact with a sharp tung- 1N23A 10.000 Low 8.0 8.0 0.1 1.0 sten or platinum wire'. 5. Development of Silicon Crystal Recti- fiers Receivers by J. H. Scaff, 1N23B 10,000 Medium 6.5 6.5 0.1 1.0 Germanium is a rare metallic element for which is silver-white, lustrous, hard, and R. S. Ohl, Bell Sys. Tech. Jour., Jan., 1N24 25,000 Low 14 4.0 0.2 0.5 brittle, with a melting point of about 1947. IN25 1,000 High 8.0 2.5 7.0 20.0 1,755 degrees F. In the electrochemical 6. The Germanium Crystal Diode by privately publ., Syl- 1N26 25,000 Medium 8.5 2.5 0.1 1.0 series of elements, germanium (No. 28) E. C. Cornelius, is considerably more electropositive than vania, 1946. 1N28 3,000 High 7.5 2.5 0.4 1.0 silicon (No. 45) ; however, the properties of the two are very similar. Other Bibliography TABLE 2 Never found free in nature, ger- Radar Engineering by Fink, McGraw - SILICON RECTIFIER CARTRIDGES manium occurs in many sulphide ores, Hill, 1947. (for video detection) usually in the form of germanium diox- Low Level Crystal Detectors by Ber- ide. The amorphous metal is obtained by inger, Rad Lab Report, 61 -15, MIT, E E g,E then 1943. E chemical reduction. Impurities are É GóE óE c added to improve the quality of the ger- Crystal Rectifiers by Torrey, Whit - E E E$e E$e E as a semiconductor. mer, McGraw -Hill, 1948. 1, cB manium it 9p 490 és.70 F. C.C..e V.:11". r'>4 x5:4 îá7_1- IN27 3,000 500 0 4,000 S 1N29 1.000 500 6,500 24.000 500 1N30 10,000 500 7,000 21.000 5 1N31 10.000 500 6,000 24,000 5 1N32 3.000 500 5.000 29.000 5 1N33 3.000 500 2,000 10,000 100

TABLE 3 GERMANIUM RECT FIER CARTRIDGES (for diode applications)

C L t E E é úé > ; SóOtt,á ;m á Is. á 1ê F ú.a î.5> .e' E a E îv F 1N34 0 - 200 + 60 22.5 60 100 1N35 Conciata of mounted pa r of matched 1N34'e for duo-diode applications.

1N38 I 100 22.5 150 500 0-250+ Fig. 4 -These two matched detector cartridges are used in discriminator circuits. 1ti39 O - 20 200 15.0 150 100 SEPTEMBER, 1948 28' Electronics

Electronics in Medicine

Part II-- Phonocardiography -c- iag- nostic use of sound amplification

The Sanborn Cardiette, a typical phonocardiograph By EUGENE J. THOMPSON

AN electrocardiogram is a completely, the leakage of blood in the shows him which valves are not closing graphic record of the voltages wrong direction through the heart out- completely. created by the pulsing of the lets produces several typical noises. The A typical phonocardiograph is pic- heart. (See RADIO -CRAFT, most common is the murmur. tured above. This instrument, like most March, 1948.) The source of these po- phonocardiographs, makes simultaneous tentials is the regularly timed nerve The phonocardiograph electrocardiograms on the same tape. impulses, each section of tissue through The sounds which help the physician The main part of the instrument is a which an impulse passes becoming mo- to diagnose heart diseases may be very standard high -gain, battery- operated mentarily electronegative with respect faint, and they can cover a fairly wide amplifier, shown in Fig. 2. Its output is to the rest of the body tissue. Because frequency range. The acoustical stetho- fed to a moving -coil, optical galvano- these impulses cause the heart to con- scope has a limited frequency range, and meter, which produces a photographic tract and expand, measurements of their it is not efficient for very low -level record on the moving light- sensitive frequency and amplitude are a good in- sounds. Therefore, a special microphone tape. In some other models, the output dication of heart action. and audio amplifier are used. Known as audio voltage operates an electromag- the phonocardiograph, the instrument netic recording lever to which a pen is MURMUR MURMUR MURMUR MURMUR not only enables the physician to hear attached. The technical aspects of elec- the amplified heart sounds, but also trocardiograph amplifiers, of which Fig. makes a permanent record of them on 3 is an example, were discussed in paper tape. RADIO -CRAFT last March. SYSTOLE DIASTOLE SYSTOLE DIASTOLE A section of this tape appears in Fig. The frequency response of the whole Fig. I -Trace produced by phonocardiograph. 1. The wavy line is a picture of the heart system is very important in determining sounds, and it represents much the same what type of record will be obtained on Electrocardiographs, which measure thing as an oscillograph trace would. It the tape. The amplifier and the record- and make tape records of the heart po- shows the heart sounds during the sys- ing mechanism are essentially flat. The tentials, have their limitations. For in- tole or dilation of the heart, during microphone used is a high -quality crys- stance, the valves at the outlets of each which it fills with blood, and then during tal type with a very- wide -range re- of the four chambers of the heart act the diastole or contraction, when it sponse. Especially built for phonocardio- to allow blood to flow in one direction empties. On this tape, the sound picture graphs, the case is conveniently shaped only -either into the heart or out of it, indicates that the murmur is most pro- for the purpose. depending on the function of the par- nounced during the diastole. Since the A typical microphone is shown in Fig. ticular outlet. Like the one -way valves physician knows which set of valves 4. Notice that an acoustic bell is at- in a water pump, they are made to open ought to be closed during each move- tached to it. When the physician places and close by the force of the fluid, not ment of the heart, the diastolic murmur this against the patient's chest, all out- by any independent muscular action. The opening and closing of these valves will not have any important connection IMEG .005 .0003 I -I /4V with the XTAL MIKE .- BIAS CELLS heart potentials, and the elec- .0005 2ME trocardiograph will not show their func- A---é IMEG }DA}, 0 T., IMEG yI IM G I MEG tioning. JACK . 1.0001 'rÁ001 2MEG The movements of the valves can be detected by the sounds they make, and f t for many years physicians depended on 90V . -1 Isv their stethoscopes to hear them. The +fir `. ----t normal ¿,r I2DT ° valve motion produces two or T+ 0 4 ,, three characteristic sounds. When the ON -OFF SW ON VC valves become diseased and do not close Fig. 2 -The amplifier is powered by battery, thus eliminating all possibility of hum. RADIO -CRAFT for Electronics 129

IQS-G3 ture of this method of recording pulst IHS-G3 beats is that, not only their frequency I I El .0005 are registered, but also .0005 3/ 1 and amplitude r1 - their wave form, which is of considerable diagnostic value. 10 0 33 iuEG 7 Another method of recording pulse IOOK 2sIEG beats uses a photoelectric tube. The technique, which is used for many other pur- .55* poses as well, is known as photoelectric iii plethysmography. j Fig. G shows how this method is used. A light source shining through a thin part of the body (an ear lobe is used WI TER A +3V 112 TER 2 MO 40 IN N7TER NITER N 3TER 145 TER N6TER Pell TER here) illuminates a phototube. Spurts of +90V CARDIOSCOPE JACK B blood pass blood vessels SENSITIVIT through the each CONT A BGTaEp 3NEG IOOK time the heart beats. The blood, coming OILY between light source and phototube, Fig. 3- Standard electrocardiograph amplifier uses very low frequency coupling components. makes the ear lobe more opaque. During the pauses between beats, blood does not side noises are excluded so that the tape hold of human hearing. flow and the lobe becomes more trans- record is an accurate indication of heart The logarithmic response offers the lucent. The light reaching the phototube sounds only. The size and shape of the very important advantage of closely ap- depends on the translucency of the lobe, bell affect the frequency response of the proximating human hearing, which is so it varies in step with the heart beats microphone. Increasing the size shifts logarithmic. This is important in analyz- and blood spurts. The varying output of emphasis to the lower frequencies; de- ing records, because an abnormal sound the photoelectric -tube circuit is fed to creasing it gives a peak in the high which has, say, twice the amplitude of an amplifier and a wavy-line tape record range. High -frequency output can also a normal sound on the visual record, is made. The amplifier used with this be improved by stretching the patient's will actually sound twice as loud with a device must have very good low -fre- skin and increasing the pressure with stethoscope. microphone is held to the When heart sounds are being record- J 4; which the u chest. A number of different -size bells ed, the physician usually listens with a LIGHT li l: is usually supplied with each instrument stethoscope at the same time. In some SOURCE. so the physician can select the one which apparatus such as the instrument in accentuates the sounds he particularly Fig. 3, provision is made for plugging in a set of headphones which are acous- wants to hear and record. PHOTOELECTRIC Microphones can be designed to re- tically compensated to permit the exam- 'CELL spond to sound in two ways, linearly or iner to hear a true reproduction of the logarithmically. If the response is linear, amplified sounds, as recorded. the output of the microphone for a sound Fig. 5 shows the special equipment which has an intensity (expressed, for used in recording pulse beats. The small example, in dynes /cm') 100 times great- cup A is held against the skin over an er than another sound will be 100 times artery by suction created by the rubber EAR LOBE output the lower bulb B or by manual pressure. The flat greater than the for Fig. Equipment for attachment to the ear. sound. However, if the response is loga- disc C, connected by a rubber tube to the 6- P 4O TOT UBE rithmic, the microphone output for the cup, contains a pressure -operated piezo- GRID louder sound will be equal to only twice electric crystal. With each pulse beat, the output for the weaker sound (log the skin moves outward. This produces I MEG 10 =1; log 100 =2). a small compression of the air in the Each of these two types of response rubber tube and in the crystal chamber. 1TK +III NV -y.GNG has its advantages and disadvantages. The distortion of the crystal caused by Fig. 7-Adapter for R -C coupled amplifier. The linear type of response is useful for the air pressure produces a small volt- detecting sounds of low intensity and age which is passed through the cable quency response, so direct -coupled cir- for distinguishing between sounds of and cylinder D, which contains a small cuits are often used. With R- C- coupled relatively slight differences in intensity. shunt time-constant capacitor, to an amplifiers an adapter circuit must be Often a microphone of this type is of audio amplifier. A recorder connected to used, as shown in Fig. 7. Polarizing value in detecting very early valvular the amplifier output makes tape records voltage is available in direct -coupled abnormalities which are below the thres- of the pulse beats. An interesting fea- amplifiers, so no adapter is necessary

Photograph Cou rtcsy The Sanborn Co.. Comb, age. Mass. Fig. S- Equipment for recording pulse beats. Fig. 4- Example of a heart -sound microphone. A- Vacuum -type applicator cup; B- Rubber These are high -class crystal types and may bulb to produce vacuum; C- Piero- electric have straight or logarithmic output curves. A microphone; D -cord. removable connector.

SEPTEMBER, 1948 Television "I IT

Instruments set up properly to align a television receiver. Alignment By ROBERT N. VENDELAND

No wide -awake radio serviceman the radio man has tried a visual align- quency, the i.f. -stage output increases can deny that FM and television ment, he'll not consider any other to a maximum at 23 me and then drops have caused a revolution in serv- method. off to a dip at 25 mc. At 27 mc there is ice techniques. Wide-band, high - The television channel allotted to a another maximum and then a drop to frequency amplifiers necessary in tele- single station is 6 mc wide, almost six zero at 30 mc. vision circuits are converting screw - times as wide as the entire standard In aligning a TV i.f., it might seem turners into either well- equipped radio- broadcast band. As a result, all the a simple matter to set the signal genera- men or ex- radiomen. tricks used to obtain high -gain, selective, tor to 23 mc and tune for a given output, Correct alignment of a television or broadcast -band amplifiers must be re- then turn to 27 me and tune for the FM receiver is difficult and sometimes versed to get video amplifiers to respond same output, with one check for a dip impossible without visual alignment to the frequency range necessary for at 25 mc. This may work if the set is equipment. If there is no real trouble in reproduction of a high -quality picture. not out of alignment, but usually a video the set, and all it needs is trimming up, The obvious solution to the problem of i.f. stage employs capacitive overcoup- it may be possible to use an AM signal wide -band amplifier adjustment is visual ling and adjusting one peak for a maxi- generator and a good indicator. But once alignment. mum affects the frequency of the other Television Instructor Fig. 1 shows a typical response curve peak. If you seesawed back and forth National Radio School, Cleveland for the i.f. amplifier of an AM broadcast trying to get the proper response, you set. As the unmodulated signal- genera- would soon lose patience. tor output frequency rises toward 456 The visual alignment technique seems kc, the output of the stage increases. It to be the only solution. Most servicemen reaches a maximum at 456 kc and then are familiar with oscilloscopes: they tapers off as the frequency increases have had one on the bench for years still more. The curve shows just where and brag about not having had to use the output of the stage is maximum. To the blasted thing once. The 'scope is the line up the receiver, the signal generator business end of visual alignment, and is set at 456 kc and the trimmers are you'll have to splice the line cord back adjusted for maximum output -meter where it was before you borrowed it for reading. the electric fan. In a television receiver, a typical i.f. In visual alignment, a sweep signal response curve might look like the one generator is necessary. This presents to shown in Fig. 2. This is plotted in the the receiver a signal which varies in same way as the curve in Fig. 1. As the frequency from 20 to 30 mc at a 60-cycle Fig. I -A standard AM i.f. response curve. signal -generator output increases in fre- rate. In other words, a 60 -cycle sine RADIO -CRAFT for +wwNwl.sA+k . . Television I31 wave modulates the FM oscillator of the would be difficult to see the ratio be- grounding of all equipment is essential. signal generator so that at one instant tween the peaks of the curve, point C, A common ground in the form of a the frequency output is 20 me and an and the point of zero response at 20 metal plate or a heavy grounding bus is instant later it is 21 mc, until finally the and 30 mc. On the other hand, if the absolutely necessary. If touching any output increases in frequency to 30 mc. sweep width is too great-say 50 mc- piece of equipment changes the sweep When 30 mc is reached, the signal fre- the response curve would be only a small pattern, the grounding is not adequate. quency starts back toward 20 mc. Out- hill on a long line across the 'scope Manufacturer's directions for each re- put at each frequency is maintained at screen as shown in Fig. 5. ceiver being aligned should be followed the same amplitude level. For an FM low -i.f. amplifier align- to the letter, since the correct order for To use the generator and oscilloscope ment, a generator with a sweep width of alignment will differ from receiver to for aligning the video i.f. stages, the approximately 450 kc is sufficient. For receiver. output of the sweep generator is first television alignment, the sweep width The block diagram (Fig. 6) shows the connected to the input of the last picture must be at least 10 mc, and the center Hickok 610 signal generator. Notice the i.f. Fig. 3 is a block diagram of part of frequency of the sweep should be ad- FM generator in the upper left corner. of a typical television receiver. C is the justable from about 5 mc to the top of The center frequency this oscillator point where the oscillator output is first the television channels (around 215 mc). is variable from 75 to 115 mc. The 75 -mc connected. After the two basic pieces of equip- fixed oscillator shown below it is The 60 -cycle voltage which frequency ment- 'scope and sweep generator -are switched in and out of operation by the modulates the FM oscillator in the gen- properly selected, a marker generator is range selector on the instrument. The erator is connected also to the horizontal necessary. When using the Hickok 610 outputs of the two generators are com- plates of the oscilloscope. This causes sweep generator which will be discussed bined in the mixer shown. By using the the electron beam to pass back and forth in this article, no marker generator is actual frequency, the sum and difference horizontally 60 times per second. The required since the instrument has a frequencies, and the first harmonic of vertical plates of the 'scope are con- built -in marker. The function of the nected to the output of the video detec- marker generator is to place a mark of tor. some type on the sweep pattern so that Let us assume at first that the i.f. you can tell the exact frequency repre- system of this particular receiver is sented by any point on the 'scope pat- properly adjusted so that Fig. 2 repre- tern. sents the response of the i.f. system at The marker generator is usually an each frequency shown. At the beginning extremely accurate signal generator. It of the sweep, the oscillator frequency puts out an r.f. signal which mixes with is 20 mc. Since the i.f. response at this the sweep signal and places a pip, as frequency is very low, the rectified r.f. shown in Fig. 2, on the response curve. appearing at the detector will be low. Reading the dial setting on the marker When the oscillator frequency reaches generator tells you the exact frequency 23 mc, which is one of the peaks in the of the pip. i.f. response, rectified output of the de- Several precautions must be taken or tector will be high. At each remaining false results may waste time. For visual frequency, detector output will corre- alignment at high frequencies, the Fig. 2 -I.f. re ponse of television receiver. spond to the i.f. response. TO PIA AMPI.. Since we have the 'scope connected TO ANT OSC. I across the load, the electron beam is c e A moving up and down with the changes in load voltage; and if we can move the RF AMR ---I MIXER I- SOUND 1 PIX IF -H SOUND TRAP PIA IF PIA IF I PIA DET. FI-- beam left and right in exact step with the changing sweep generator output, E F TO AUDIO TRANS. we'll have drawn our response curve. IF DISCRIM. SOUND IF II SOUND OR LIM. This is exactly what is done, since the sine -wave voltage that is used to change Fig. 3- Instruments are connected to the televiser at points lettered in the diagram. the FM oscillator frequency is introduced into the horizontal plates of the e

'scope. 1

As the sine wave sweeps to increase I DET. LOAD the frequency, it also moves the electron I 1 1 I J Ì7 beam in the 'scope to the right, and the HOW THE SWEEP response curve is drawn exactly as it HOW THIS STAGE GEN.OUTP TIS L-- - looks in books. PASSES FRED ATTENUATED BY'8' text OUTPUT DET Fig. 4 gives a complete graphical picture of the whole operation. Obviously, a good 'scope is necessary for successful visual alignment. The sweep signal generator should be designed for a sweep -width range that will 20 23 25 27 30 20 show more than the entire response SHEEP GEN. OUTPUT curve. For making a television alignment the sweep generator should have at least a 10 -mc sweep, for all band widths extend somewhat beyond the 6 i I IlIllillIll mc of a television channel and the trace must taper to a reference line. Fig. 2 EO MC --> shows the trace tapering off to zero at I FM DRIVER? SIGNAL 20 and 30 mc, a good giving picture of I the relative amplitudes on a 'scope pattern. If, for example, the generator I sweeps a trace as shown in Fig. 2, but L only extends from 22 to 28 mc, the curve SIG. GEN. 'SCOPE would show only from A to B, and it Fig. 4 -Shows path of test and synchronizing signals through he set and oscilloscope. SEPTEMBER, 1948 Tclevlairi 32 I

each oscillator, the range of the genera- is employed, the horizontal -sweep volt- erator or similar units give better re- tor can be extended from zero to 240 mc. age from the generator must be used. sults. The 505 'scope has a built -in FM The mixer output is fed to a cathode The internal marker of the model 610 sweep that is excellent for lower -fre- follower and an attenuator. The other will check the frequency of each point quency work. features of the generator shown on the on the trace. This built -in, variable -fre- In aligning a sound channel visually, block diagram will be discussed as they quency oscillator has a dial with ex- the discriminator or ratio detector is are used in the alignment of the typical tremely accurate calibration from 20 to aligned first. The curve is adjusted to television receiver of Fig. 3. 30 mc, the range of most television i.f. show a response like that in Fig. 8. The oscilloscope is connected across channels. The dial is calibrated in tenths Marker frequencies are injected in the of a megacycle to eliminate all guess- same manner as for picture -channel work. The amplitude of the marker sig- alignment. If an extremely accurate nal is variable, but always use the mini- marker is desired, the built -in Pierce mum necessary output. Too large a crystal oscillator of the 610 generator marker amplitude will distort the re- may be employed. This oscillator may be sponse curve. modulated or unmodulated and is in- Occasionally, the i.f. amplifiers will jected in the same manner as the vari- pick up stray oscillation and several able oscillator. markers may appear on the trace. To To align for the pattern of Fig. 8, the aid in identifying the proper marker, sweep generator is inserted at the sec- the 610 has provision for stopping oscil- ond sound i.f. or limiter grid (point E lation of the marker oscillator and using in Fig. 3), and the 'scope is connected the tank circuit as a wave trap in the to the discriminator load (point F). sweep output. This will put an absorp- After the discriminator response curve tion dip in the response pattern as is obtained with markers at the correct Fig. Result of using too a 5- wide sweep. shown in Fig. 2. Some servicemen prefer points, the generator output is moved the detector load, this to the pip and use it in all cases. back stage by stage, always giving a point A in Fig. 3. larger discriminator Several features of the Hickok 505 After the before response curve on stage the detector is the 'scope. To 'scope adapt it particularly to visual aligned, manufacturer's directions usu- bring the over -amplified alignment. Its input amplifier has a ally specify the picture back within the bounds of the connecting sweep gener- 'scope screen, decrease generator output. response up to 1 mc. extremely It is sen- ator to point D of Fig. 3, the grid of the This makes sitive, and its input can be fed through first picture i.f. amplifier. The 'scope sure that no saturation of the stage under alignment is occurring. an internal demodulator for observing lead is left at the detector grid. The sweep patterns before the detector of before Correct tuning for i.f. amplifiers is trap just point C is aligned. This obtained when the discriminator the set -at point B, for example. The usually is an adjacent -channel used re- trap sponse is at a maximum and shows no 60/MAC distortion. OUTPUT After both and 6J6 FM GEN. MIXER picture sound i.f. am- 6J6 ATTE NUATOR plifiers have been adjusted, the oscilla- MARNER OUTPUT j_ SWITCHED IN AND OUT ST RANGE SWITCH tor for each channel may be tuned. This 1 is of particular importance on push- MARKER PHASING button or turret -tuned sets where each 75 MC FIXED OSC.6AR6 6 %5 POWER Ius MDD.I- %TAL SECTION VAR.sECTION 1 channel has its private tuning arrangement. Crystals whose harmonics fall on Fig. 6 -Block diagram of Hickok 610 generator used in the alignment method described here. the desired channel's sound frequency may be used to set up each television 'scope also has its own 60 -cycle sweep to eliminate the sound from a lower station. These be with provisions for phasing the retrace channel. Correct adjustment is made crystals may obtained for the sound carrier of any or for blanking it out. when the trap frequency shows a mini- frequency of the 13 channels. For the beginning of the alignment, mum on the indicator. Shut off the sweep the sweep generator is fed into the grid and use the marker generator as a of the last picture i.f. amplifier, point C source for the trap frequency. For a in Fig. 3. The center frequency is set for better indication on the 'scope, the built - the middle of the picture i.f. channel, in, 400 -cycle modulator shown in Fig. 6 and the sweep is adjusted in width until can be turned on. Tune the trap for the entire response is visible on the minimum amplitude. 'scope screen. Turning on the sweep causes the next The set manufacturer's data will gen- response pattern to appear on the 'scope. erally show a picture of the desired re- This procedure is repeated stage by sponse at each stage. The slug adjust- stage until the antenna input is reached. ments in the cans are tuned until the During the earlier part of the align- 'scope picture looks like the manufac- ment, the manufacturer may have ad- turer's response chart for that stage. vised disabling the oscillator. When the At first it will probably appear like the signal is fed to the antenna terminals, one shown in Fig. 7, with the main trace the oscillator should be connected. The Fig. 7-Trace and retrace curves not phased. and the retrace out of phase. When the response curve of the whole set will 505 or 195 'scope is used as the indi- appear on the 'scope screen. cator, the 60 -cycle horizontal -sweep volt- Before the oscillator is tuned, the age need not be taken from the sweep sound channel is usually aligned. Since generator. These 'scopes have internal the sound channel is an FM receiver, it 60 -cycle sweeps with provisions for can be adjusted just like any separate phasing the forward trace and the re- FM radio. The only difference is that trace so they will coincide to look like in most cases the sound channel of a Fig. 2. The 505 'scope has a return -trace TV set has a 20- to 30 -mc i.f., while an eliminator so that the retrace can be FM receiver i.f. is usually in the 10 -mc blanked out entirely, with no need for range. For visual alignment of tele- phasing. However, the 610 generator vision FM circuits, the model 610 sweep has a phasing network built into it so generator is ideal; but for FM receivers, that the main trace and the retrace can the lower -frequency sweeps of the be made to coincide on any 'scope. If this Hickok model 288X FM -AM signal gen- Rg. 8-Standard curve of FM discriminator RADIO -CRAFT fo, b :7k,; , Television

Frgnch Television Progress is RapiJ

By P. HEMARDINQUER*

HE.nulnber of television receivers beam is at an angle to the perpendicular in France is still very small -it of the screen. This makes necessary a does not exceed a few thousand. correction of the sweep to avoid distor- This is so, first, because there is tion. A parabolic sweep of the same fre- Fig. l -Dual theater -type TV projectors. only one television broadcast station in quency as the original transmission is France; and second, because of the very utilized for this correction. high price of television receivers. Pro- The double high -frequency receiver is grams are not particularly exciting, and of the t.r.f. type. It transmits amplified the station is on the air not more than signals at the carrier frequency of 46 me one hour daily. to the detector and video amplifier This limited program schedule -due stages in the sealed and insulated case to budget economics of the French gov- through an insulated coupling system ernment -does not prevent the engi- sealed in a vacuum tube, as illustrated neers of France from continuing their in Fig. 3. research, and some remarkable results It is usually convenient to connect the have already been obtained. American fluorescent screen and an anode of a technicians declared that the 1,000 -line television tube to ground. The cathode transmissions they saw were better than and video amplifier are therefore at a American television. high voltage, approximately 70,000 volts Projection television is also being from ground. These elements are in a studied, and in the near future a double case mounted on insulators within the television projector (analogous to the body of the projector. (See Fig. 4.) Fig. 2- Optical system of the projectors. double motion -picture projector) will be In view of the great acceleration of installed in a Paris movie house to tele- the electron beam, and the consequent vise both films and news items. difficulty of deviating the electrons, the The new projector consists of a tele- sweep amplifiers have to be particularly vision receiver, the projection equipment powerful. itself, a control panel, and a power sup- The equipment will shortly be put into ply. operation to demonstrate to the Parisian To maintain uninterrupted projection public the practical possibilities of under all circumstances, the installation large -screen projection in theaters. It is is made in duplicate. Two complete sets being developed by the Compagnie pour of equipment are ready to operate at all la Fabrication. des Compteurs, under the times; if one should stop, the other can direction of the great French television (See be swung into immediate action. technician, Barthelemy. Fig. 3 -The insulated r.f. coupling syst,,rn. Fig. 1.) A special cathode -ray tube of high power is used for projection. It is shown with its optical system in Fig. 2. The accelerating voltage can be regulated between 60 and 80 kilovolts. The electronic beam has an intensity of 2 ma maximum and an average of 0.5 ma. The tubes are very powerful -the dimensions of the primary image to be projected are 12 x 16 cm (about 4.7 x 6.3 inches) and the diameter of the luminous spot is only 0.25 mm. The screen is of the directive type, having either a powdered- aluminum- covered flat surface, or a slightly concave surface covered with little plates of stamped aluminum to form a concave mirror. This assures a good concentra- tion of reflected light along the vertical plane, while maintaining sufficient horizontal diffusion. The gain obtained, as compared with a white, perfectly- diffus- ing screen, is 4.25. The objective lens used has an aper- ture of f 1.9. The brilliance of the projected images is about equivalent to that f a standard motion picture. As can be seen in Fig. 2, the electron °Consulting Engineer, Grenoble, France Fig. 4 -Side view of the projector with cover removed to show arrangement of the components. SEPTEMBER. 1948 31 Servicing

Fig. I -The dial pointer is on the ring in front of the speaker. Fig. 2 -Arrow points to plate containing four printed capacitors. Radio Set and Service Review Ward's Airline Models 7lltlI- 2003:I and 11lllllf -I ilLI

RESTRINGING receiver dial drive dial gear mounted around the circum- thin ceramic plate 1 -inch long and 1 mechanisms quickly and correctly ference of the speaker. A 1A -inch metal inch wide. This unit is indicated by the has meant headaches and loss in pointer fastened to this ring or gear is arrow on Fig. 2. time and profits to radio service visible through a slot under the cali- The Model 74BR- 2003A, Figs. 4, 5 and technicians for years. All too frequently, brated scale on the front of the cabinet. 0 uses a new type of slide -rule con- manufacturers fail to supply dial string- Six and one quarter turns of the control struction for dial drive. The pointer is ing data in their servicing information. shaft are required to tune across the fastened to a strip of spring brass with Even when dial stringing guides are band. serrations on one edge (like a hacksaw available, the average technician finds it The end of the tuning shaft project- blade) to engage the teeth of a small almost impossible to replace the dial ing under the chassis is threaded and gear on the tuning control. The strip string without four hands, Scotch tape moves the tuning slugs or cores in the slides in the channel of a flat guide very and an assortment of hooks, needles and antenna and oscillator coil forms as it much like the cross section of a flat cur- other gadgets. turns. The back cover of the set is a tain rod. The saw -tooth serrations are This problem has been eliminated in sheet of metal -backed cardboard used as visible on the metal strip in the close up the Model 84BR -1515A and 74BR -2003A an antenna for local reception. A Fahne- view at left of Fig. 4. Airline receivers developed by the Bel- stock clip fastened to, but insulated This set was designed as a radio - mont Radio Corporation for Montgom- from, the cover provides capacitive phonograph combination. Its circuit, ery Ward. The former model is shown coupling to an outside antenna. Fig. fi is similar to the circuit of the S. in Figs. 1 and 2. This is a 4- tube -plus- An interesting innovation in receiver 84BR -1515A in Fig. This set uses a rectifier a.c. -d.c. broadcast set with per- construction is the use of printed cir- loop antenna mounted in the cabinet and meability tuning. The tuning control cuits. The coupling and bypass capaci- connected to the chassis through a shaft, on the right in the photographs, tors enclosed in broken lines between socket and plug connector. Speaker and has a small gear linking it to the 5 -inch the 12AT6 and 50B5, Fig. 3, are on a phonno pickup connect to the chassis through co -axial type connectors.

SPKR When the chassis is in the s:t it is 3 EXT ANT 12BE6 12BA6 12AT6 220 r .óos 1 50B5 inches high over -al!. This snakes it pos- t .0001 sible to install it in a cabinet just a few I inches higher than the over -all depth of its record player or changer.

1 2 The electrical specifications of these 411TI AVC sets are given below. Sensitivity meas- B+ MAr470A 1 ISO urements are based on 50 milliwatts output. This may be pleasured by discon- voice .v necting the coil and replacing it I J .00022 40 I with a 3.2 -ohm. 5 -watt resistor. A level L -kH of 0.4 volts a.c. across the resistor is 4'.011 sis 27 equivalent to 50 ntilliwatts.

Model 7 11111-20.3 A 5 35W4 Power -n,V.ly - 105 to 12:. volt- .,.a. or 41.e.. 65 Nvitl -. Fig. 3 -This standard circuit uses four printed Frequency rams, i:i.l to ],;211 I:r. Intcrme,Ifula capacitors- enclosed by broken lines on the 1206 128E6 121146 5085 5W Selectivity -At .inu diagram -and permeability -tuned intermediate 7 J 4 J 4 ) 4 3 4 3 6 1 AC. .os Sc

RADIO-CRAFT f o r Ilervichm I35

Fig. 4 (Right- Bottom view of the 74BR- 2003A shows the flexible -rule dial drive system. An enlarged view of the dial drive is shown above.

Power output -0.75 watt undistorted, 1 watt maximum. Loudspeaker -4 x 6 -inch oval PM with 3.2-ohm voice-coil impedance. Tube complement -12Bó6 converter, 12ßA6 i.f. amplifier; 12AT6 detector; a.v.c.; and a.f. amplifier, 50B5 power amplifier and 35W4 rectifier. Automatic record changer. Model 84BR -1515A Power supply -105 to 125 volta a.c. or d.c., 35 watts. Frequency range -535 to 1620 kc. Intermediate frequency -455 kc. Selectivity -At 1.000 kc, 55 kc at 1,000 times down. Sensitivity-20 microvolts average for 50 milli - watts output. Power output-0.7 watt undistorted. 1 watt maximum. Loudspeaker -4 -inch PM, 3.2-ohm voice coil impedance. Tube complement -12BE6 converter, 1213A6 i.f. amplifier, 12AT6 detector; a.v.c. and a.t. amplifier, SUBS power amplifier and 35W rectifier. Alignment procedure The signal generator used for aligning these sets should be modulated 30 percent with a 400 -cycle a.f. signal. The a.f. signal must be available for a.f. measurements. Alignment data for the Fig. 5-This view shows the bottom and rear of the chassis used in the Model 74BR- 2003A. 84BR -1515A and 74BR -2003A will be found in Tables I and II respectively. good. If C3 requires considerable adjust- are badly out of alignment or the set When checking tracking of either set at ment, readjust the setting of the an- fails to track properly, turn the tuning 1400 kc, screw the antenna core in or tenna core. Make these two adjustments control until the bracket holding the out for maximum volume. Retune the several times until C3 does not have to slugs is against the front of the chassis. set to 1620 kc and check C3. If no appre- be readjusted at 1620 kc. Adjust both tuning slugs so they pro- ciable change is needed the tracking is If the tuning slugs of the 74BR -2003A trude 1 9/32 inch out of the base of the

LOOP 12BE6 rr ,-20,.q i2BA6 -,rz i3-oa¢ " -I I2AT6 DET AVC AUDIO 5áB5 CONV5 I AMP 5- OUT 5 1r tte 11 .01 1( nQ 6I -I l Ì°,SI ll 1 35W4 \ laoaar PILOT IR VAC .001 f 75Yµí' 1 A J 5 I T C6 2560K 2 REGT SW r1 i -MM -1H 22K ,56 .- Wv-o.00022 ANT 147avr- 3.34E0 25 // ( fe.5n 14n PHONO IN 560K 1.5n TONE 1.26 ue z3Pe s 1 I Ti 1 * Vc .306 IMEG 20 40 IJ S2 -v- PHONO MOIOIt .00022 .09 L3 33 5085 12BA6 126E6 12IIT6 PHONO RCVR

4 3 4 3 4 3 4 3 _,000e2 270K .641E0 .03Ì 1211240K

Fig. 6- Special oscillator coils simplify tracking in the 74BR -2003A The chassis is 3 inches high, 153/6 inches long and 61/2 inches deep. SEPTEMBER, 1948 $ervicieg 361 tuning assembly. If trouble is had with TABLE I the 84BR- 1515A, adjust the slugs to the 84BR -1515A positions shown in Fig. 7. in SIGNAL GENERATOR The i.f. transformers these sets are Input For Coupling Connection Ground Tuner Adjust For 50- Milliwatt Frequency Capacitor to Radio Connection Setting Maximum Output Output Iron cores all Cores in output 455 kc .1 if 12BE6, Pin 7 12AT6, Pin 2 the way out and input i.f. cans 45 microvolts Iron cores all Oscillator trimmer 1620 kc .1 µf 12BE6, Pin 7 12AT6, Pin 2 the way out CS

2 µµf (max. External 1620 kc capacity) antenna clip 12AT6, Pin 2 1620 kc Antenna trimmer C3 20 microvolts 2 µµf Adjust position of (max. External ant. core by screwing 1400 kc capacity) antenna clip 12AT6, Pin 2 1400 kc in or out 20 microvolts

400 cycles .1 µf 12AT6, Pin 1 12AT6, Pin 2 .03 volt

TABLE II 74BR -2003A

Rg. 7- Permeability tuner of the 84BR- I515A. SIGNAL GENERATOR Input For TOP VIEW SEC. CORE TOP VIEW PRI. CORE Coupling Connection Ground Tuner Adjust For 50- Milliwatt PRI - SEC Frequency Capacitor to Radio Connection Setting Maximum Output Output Arl' Iron cores all t I Trimmers on output 7 I I 3/32 455 kc .1 µf 12BE6, Pin 12AT6, Pin 2 the way out and input i.f. cans 28 microvolts PRI.WINDI NG I OM Iron cores all Oscillator trimmer 4 1620 kc .1 µf 1213E6, Pin 7 12AT6, Pin 2 the way out CS al-js COIL FORu- 111RO¡¡D External Iron cores all Shunt ow. coil ALIGNMENT TOOLS 535 kc 200 µµf antenna clip 12AT6, Pin 2 the way in L3 11 APPROIf microvolts SEC.WINDING External SCREW TYPE CRIMP IN 1620 kc 200 µµf antenna clip 12AT6, Pin 2 1620 kc Antenna trimmer C3 8 microvolts SILVER MICA TUBING CAPACITOR Adjust position of External ant. core by screwing 1400 kc 200 µµf antenna clip 12AT6, Pin 2 1400 le in or out 8 microvolts CROSS SECTION OF I F 400 cycles .1 12AT6, 1 12AT6, 2 Fig. 8 -Cross -see ion of the i.f. transformers. IAf Pin Pin .03 v It of novel construction. The primary and secondary windings are on the same core to pass through for adjusting the secon- through the center of the primary tool. with all tuning adjustments made from dary core. The primary and secondary Two resonant peaks will be noticed the top. A cross- section drawing of these tuning tools are A and B shown at the when adjusting the i.f. transformers. Be transformers is shown in Fig. 8. The upper right in Fig. 8. Both are made sure that the primary core is above its core of the primary winding has a hole from fiber or other insulating material. coil and the secondary core is below its through its center to allow a special tool In use, the secondary tool passes coil.

Regulating Voltage With VR Tubes

Amateur and constructor will find them valuable in a number of applications

By RICHARD L. PARMENTER

IN the modern ham station the need receiver to be thrown "off- tune" by vari- conditions a large number of positively for stabilized voltages in various elec- ations in plate voltage caused by line charged ions and negatively charged tronic circuits is becoming more and voltage fluctuations. They are practi- electrons are produced. The breakdown more apparent. When the circuit re- cally indispensable to the more experi- point is determined by the amount of quiring voltage regulation draws a rela- enced builder who has need for stable tively small current, gaseous type regu- voltages in frequency meters, variable - RS lator tubes carry out this function very frequency oscillators, and local oscilla- well. They are economical and simple to tors of v.h.f. receivers. Since these tubes SUPPLY OLTAGE 1 T e LOAD REGULATED POTENTIAL install, requiring only the tube and maintain a relatively constant voltage socket and one or two resistors. Since across a varying load and stabilize a they present few difficulties to the user, varying supply voltage across a constant these tubes should be used more than load, their many uses are apparent. Fig. I -This is the bask regulator circuit. they have been in the past. This descrip- When a voltage of correct potential is tion of some of the uses for VR tubes is placed between two terminals in air or voltage together with the amount of gas a reminder that such a useful little gad- any other gas, the gas will break down in the tube and also its pressure. It is get is available to the radio builder. suddenly and act as a reasonably good fairly easy to understand that the less The VR tube will be a big help to the conductor of electric current. This dense the atmosphere inside the tube, beginner who has built a regenerative breakdown is because a high enough the less difficulty the electrons will have detector receiver and who has been dis- voltage actually tears electrons from in their progress from cathode to plate. concerted by the tendency of this type the molecules of the gas and under these Under reduced pressure the ionization RADIO -CRAFT for ierrichas 37 voltage -the voltage at which the tube tube being used. Use Ohm's law to deter- by noting if the tube "starts" when volt- will conduct -may be reduced. The oper- mine the value of resistor RS, after the age is applied. If no glow appears ation of neon tubes, mercury vapor tubes supply voltage has been measured. In around the electrodes of the tube, either and gaseous regulator tubes is based on the following formula, the necessary the supply is not high enough or the this fact. The starting voltage of regu- series resistance RS is equal to the volt- value of resistor RS is too high. Insert lator tubes is about 30% higher than the age to be dropped across the resistor a 0 -50 ma d.c. millimeter at X in Fig. 1 rated voltage of the tube. Once the gas divided by the current which is to pass and adjust RS until 20 to 25 ma flows in has become ionized voltage changes at through it. Thus the circuit. Since this current will drop the plate of the tube result in changes Es - Er with increased load, it is better to set RS the no -load current somewhat higher UN REGULATED VOLTAGE - than would normally be assumed. Even REGULATED VOLTAGE-NI I { RS A as high as 30 ma is desirable in some where cases. detector circuit Fig. RS is the value of limiting resistor The regenerative 3 uses an OD3 /VR150 for regulating -- REGULATED VOLTAGE-LO Es is the supply voltage for vari- is the regulated voltage (tube rating) the d.c. voltage to compensate Er voltage. An electron - of ations in line I is the maximum rated current the is shown but others tube in amperes. Usually about .03 coupled detector COMMON amp. could be used if preferable. To provide Fig. 2 -Two tubes give two regulated outputs. screen and plate voltage regulation, use The voltage Es-Er is the amount that the same setup as in the v.f.o. cir- in the amount of current it passes. This is lost by IR drop across resistor RS. cuit, Fig. 4. In this diagram, both screen condition exists until the potential at If two or more VR tubes are connect- and plate voltages are regulated for var- the plate is reduced to a certain critical ed in series, then two regulated poten- iations in load. This is desirable in a value when the tube will revert to its tials may be obtained as shown in Fig. 2. variable -frequency oscillator since some original state of passing practically no The value of the limiting resistor in this variation in load and output will be current. case would be determined in the same noted when tuning across its frequency In the case of all VR tubes -when manner as before but the total value of range. Regulated voltages are necessary ionized -the change of current through regulated voltage (add ratings of the in this type of oscillator to maintain the tube due to variations in potential good frequency stability and reset ac- results in a certain constant potential curacy. across the tube. In this respect the tube Fig. 5 shows a grid -dip oscillator used is acting like a constantly varying re- widely for determining frequency of sistor which has a lower value if the resonant circuits in transmitters and re- potential is high and a higher value if ceivers. It works on the principle that if the voltage is low. In this way, the effec- power is absorbed from an oscillating tive IR drop across the tube is kept at a circuit (by another resonant circuit in constant value. This constant IR drop is this case) the current flowing in the grid applied across the load, which thus re- circuit will decrease sharply. In other ceives a practically unvarying supply. words if a tuned circuit of the same fre- The basic circuit for the use of VR quency as the tuned circuit of the oscil- tubes is shown in Fig. 1. The supply Fig. 4-VR tube adds to v.f.o.'s stability. lator is brought near it, the point of voltage must be approximately 30% will be would be used Er. By resonance of the unknown circuit greater than the voltage that is desired. tubes used) for in rectified connecting two or more tubes in series indicated by a sharp dip the grid current. Unknown L -C combina- RFC it is possible to obtain a wide range of voltages suitable for various uses. Re- tions may be calibrated by this means. +I% Since grid -dip oscillators are calibrated LOAD RESISTOR member, amount however, that the total good of current can be drawn from the with the best standards available, that is to bottom tube, Fig. 2, of the series string plate voltage regulation desirable is limited because the upper tubes must maintain their accuracy to the highest degree. The VR tube fits into the re- REGEN CONI 1 VR TUBE carry all the current in the circuit. The upper tube or the one that is nearest the quirements very nicely. In fact, the only- other way to obtain satisfactory opera- Fig. 3 -A stabilized regenerative detector. B -plus would have to carry its own current (10 to 30 ma) plus the current of tion is to use a battery supply. This is because a higher potential must the lower tubes, plus the current that is These few illustrations of the various be applied to the tube to ionize it. As drawn off for the load. In other words, uses of VR tubes should indicate to the soon as the tube is conducting the output the current that is available for the load radio builder or experimenter many voltage drops to the rated value of the must necessarily be quite small, perhaps other possibilities for their effective use. tube. In the OD3 /VR150 a starting po- 10 ma or less, in order to leave enough In almost all radio or electronic equip- tential of about 185 volts is desirable for the voltage regulating function of ment there is often a compromise be- for good regulation. The series resistor the tubes. This is one of the limitations tween accuracy and cost of equipment. RS is of correct value to hold the current of VR tubes but this may be partially The performance of many pieces of through the tube to a value of some- offset by designing the load so little cur- equipment can be improved through where between 15 to 20 milliamperes for rent is required for it. Along the same good voltage regulation. Since the cost normal operation, depending upon the line of thought of course, is the fact of voltage regulation is low, this is an application. If the total potential avail- that quite often the circuit design may excellent means of improving the accur- able from the power supply closely ap- be such that 150 volts maximum is suffi- acy of test equipment. proaches the voltage rating of the tube, cient for the regulated section. the regulation will be poor and will be Typical VR -tube applications are effective only over a limited range. In shown in Figs. 3, 4 and 5. Since these other words it is desirable to have the are merely representative circuits, exact OD3 /VR ISO tube conducting a considerable amount values for the various components are of current to start with so that a greater not given. Fig. 1 is the basic circuit and range may be covered by its variable the general design procedure has been resistor characteristics. If the resistor given for it. The same principles apply RS is less than 3.000 ohms to make to the any circuit using VR tubes. The re- R+200V APPROX tube draw about 20 ma, then the supply sistor RS would be determined mathe- voltage is too low for the particular VR matically and checked for correct value Fig. 5-Grid -dip meter accuracy is improved. SEPTEMBER, 1948 381 lierriciag

Pepping Up Midgets

By K. E. STEWART A.c. -d.c. midgets often offer many opportunities for improvement.

SOME midget a.c. -d.c. receivers do Feed -back can often be eliminated by shown in the figure should be re- not have sufficient sensitivity for properly dressing the i.f. transformer duced to prevent too great an in- use in remote areas where signals leads or by removing some of the excess crease in the a.v.c. time constant. The are weak. Often a repairman in a wire. Substituting metal tubes for glass time constant in seconds is the product vicinity where there are fairly good sig- ones will sometimes eliminate the of C in pf and R in megohms. The time nals will find a midget receiver which trouble when tube shields fail. constant in Fig. 2 is 0.15 second. There- seems to test o.k. in every respect except The output stage in many modern fore, if the capacitor becomes 0.1 µf, the that it doesn't have enough volume. Al- midgets does not have a cathode bypass resistor must be 1.5 megohms to hold the though installing an outside antenna capacitor. The omission of this capacitor time constant to 0.15 second. However, will usually improve reception in both introduces some negative feedback into in most cases, a 2.2- megohm resistor will these cases, such an antenna is not al- the stage, reducing hum and increasing give more output, and the increase in ways convenient. stability. The bass response and the gen- the time constant will not be noticed. One common fault in midget receivers eral output can be increased by the in- It is important in changing the filter is too many turns of wire in the tuned stallation of a 10- to 25 -µf bypass. circuit of the a.v.c. to avoid loading the loop antenna. The technician may find, Usually receiver output can be sub- audio output of the detector to any ap- in trying to peak the antenna trimmer stantially increased by a comparatively preciable degree. Effectively, the resis- around 1500 kc, that the output in- small addition to the B- supply voltage. tor and the capacitor are in series across creases as the trimmer capacitance is the audio load. The 0.1- sf capacitor, if reduced. Often the capacitance cannot CONK IF AMP placed across the audio load, would con- be reduced enough to hit the resonance stitute practically a short circuit. The AYC peak. Removing 1 to 3 turns of wire w. a series resistor prevents this and there- .0s 3 MEG from the loop will correct this condition. '., fore must be kept fairly high in value. The turns should be removed from the Fig. 2- Typical a.v.c. circuit in midget set. In a few stubborn cases it is worth inside of the loop. Only one turn should while to reduce the a.v.c. voltage to get be removed at a time. Check with the A typical filter circuit used in these more gain in the receiver. A practical antenna trimmer after removing each receivers is shown in Fig. 1 -a. The filter way to do this is shown in Fig. 3. A turn. The removal of more wire than resistor has a value of 1,500 ohms. If 470,000 -ohm resistor is connected be- necessary to provide peaking will reduce the value of this resistor can be reduced, tween the load end of the a.v.c. line and the sensitivity of the set. the IR drop will also be reduced, result- ground. This value is usually best for ing in a higher voltage output. Fig. 1 -b the proper compromise between added RECT shows how this resistance can be de- gain and reduced a.v.c. action. creased to 1,000 ohms without impairing I.SMRECT 250 750750 tttt y- filtering. (See also "We Learn the Hard CONY IF AMP a40-20 T¿0 ,ll,2p Way," RADIO- CRAFT, Jan., 1944.) The 1,500 -ohm resistor is replaced with two AYC

resistors, one of 250 ohms and the other 470K Fig. I -How to decrease filter resistance. I of 750 ohms. A 20- sf, 150 -volt capacitor Another common fault among midgets is also added. The ripple voltage with Fig. 3 -How the a.v.c. voltage can be reduced. is the tendency to go into oscillation this circuit is usually lower than it was when tuned to the low- frequency end of originally, and output goes up consider- Most of these methods are of course the dial if the i.f. trimmers are peaked. ably. contrary to the manufacturer's design On checking the alignment of these re- In most midgets the a.v.c. filtering cir- of the receiver. They are recommended ceivers it is sometimes found that the cuit consists merely of one resistor and only as a last resort after the set has i.f. transformers have been slightly one capacitor, with no isolating net- been thoroughly checked for ordinary stagger -tuned to prevent oscillation, works for the various controlled stages. faults. The manufacturer generally ex- with, of course, a resultant loss of sensi- Fig. 2 shows a typical circuit. Some- pends more time and labor in engineer- tivity. If the feedback producing oscil- times a noticeable increase in volume ing his receiver than you will be able to, lations is removed, the i.f. transformers will result from replacing the .05 -µf and it is bad business to redesign a cir- can be peaked, giving a marked increase capacitor with 0.1 itf unit. cuit while overlooking faults which may in selectivity as well as sensitivity. The 3- megohm isolating resistor continue to get worse. RADIO -CRAFT for Foreign News I39 European Report By Major Ralph W. Hallows RADIO-CRAFT LONDON CORRESPONDENT

battery point over the relative merits French televisers of AM and FM for v.h.f. high -fidelity At the recent Foire de Paris (Paris broadcasting. Almost any place where Fair) an unexpectedly large number of radio hams gather you will find such French -made televisers was on display. you begin to heated arguments that No less than 23 makers exhibited them wonder when the shooting will start. and the number of different types was The AM fans maintain that the method considerable. Till recently few televis- of their choice can do anything that TELEVISION protest that ers have been available in France with can be done by FM. They cathode -ray tubes of larger than 7 to 9 is now going FM means receivers of a more elab- inches there weren't very many ahead rapidly and cheap -and orate and expensive type that of those. At the Fair there were 11 dif- in France. At do to FM sets can never justice this ferent sets with 12 -inch tubes and three the moment the type of broadcasting. Frequency drift, type, with screens only transmitter cheap receiv- of the projection they say, would damn the ranging from 16 x 12 to 22 x 16 inches. is installed in the Eiffel Tower in Paris; er and the difficulty of tuning such a were but relays Lille and Lyons None of the projection types at are now set would result in further damning on priced, so they can't be regarded as pro- under construction and are expected to the part of its owner. models. others, prices be in operation before long. duction Of the Other re- On the other hand the FM support- $260 for a 10 -tube table - laying stations be ranged from are to built at Bor- ers (of whom I am most emphatically model giving vision only and with a deaux, Toulouse and Marseilles. It has no one with more one, provided that 9 -inch screen to $920 for a 25 -tube con- been decided that the present 455 -line than about my 190 pounds of weight shall sole with a 12 -inch screen and incor- system be maintained for at looks like getting nasty) hold that FM radio receiver. French de- least 10 years to insure re- porating a purchasers of gives by far the better all- around signers as a whole seem to favor four televisers against having their sets sults; that it is much superior in elimi- knobs, was made obsolete kind main control though there overnight by changes in nating man -made static (the only one model with only two. Others had television standards. At ; the same time an that matters much at such frequencies) five to It seem as if 819 -line service is from eight. didn't being developed to that it is a disgrace to designers in would -be buyers would have long to work side by side with the other. The these days for even a cheap set to suf- Eiffel Tower station wait for delivery. Seven manufacturers already has two fer from frequency drift; and that both guaranteed to supply at once; others 819 -line outfits, including orthicon -type alignment and tuning can be made per- cameras, which being mainly offered delivery in one to three are used for ex- fectly simple. Who will win the battle? weeks. And, believe it or not, that's pret- perimental transmissions. Several im- Clothing is strictly rationed and laun- portant demonstrations ty good going in Europe nowadays. If have been given dries play havoc with what we have; my doesn't soon let me have the with complete success. The same pro- if was the tailor but I'd bet my shirt -even it suit of clothes I ordered six months ago, gram was sent simultaneously 455 - by last one I had -on FM. I'll be going about in a blanket! line and 819 -line transmitters. At the receiving end corresponding televisers Stable discriminator were arranged side by side so the au- Talking of FM alignment leads me to Wired wireless dience could make direct comparisons mention a remarkably stable discrimi- I'm not sure whether there are radio between the high- standard and defini- nator circuit (shown below) described program relay services in American tion systems. During these demonstra- recently by Thomas Roddam in Wire- towns and villages. By program relay tions a series of linens, cretonnes and less World. Roddam is one of our most services, I mean systems in which a com- other cloths in a variety of intricate brilliant young radiomen, and anything pany runs an elaborate receiving sta- designs and colors were placed in front tion in or just outside a built -up area of the cameras. A friend who saw one 6AK5 6AL5 and supplies subscribers, connected by of the shows tells me that reception of LIMITER D15CRIM wires to a central exchange, with a patterns such fine black 70v as and white IOK 5 4DÚµ} choice of two or more programs. Wired checks was startlingly good. "I hadn't a wireless is used a great deal here. Sub- notion that television could do such 6 scribers pay 35 to 40 cents a week and things," said he! Another interesting INPUT the relay company provides and main- item was the projection on to a 12 x 10 tains the simple gear needed in their feet screen of a film made from 819 -line homes. The are the sub- .01 advantages that o television images. 100 scriber gets trouble -free and interfer- You must know about the system in- ence -free reception of good quality at vented a good many years ago, which he writes about 's worth studying. His all times and in all conditions. The allows movie film to be exposed, de- discriminator circuit is shown in the ac- British Post Office, which also runs the veloped, fixed and passed through a pro- companying diagram. It is not, as he country's telephone system, has been jector in well under 30 seconds. It may says, very efficient; it needs a high in- engaged for some time in developing a be that a combination of this system put and delivers a low output; but it system of relaying radio programs to with 819 -line (or, perhaps, one thou- does stay put. It requires a 150 kc in- telephone subscribers. When he wants sand- and -something -else line) televi- termediate frequency, though that radio the subscriber calls the exchange sion will provide the quickest short -cut raises no great difficulty. The point and asks for the program of his choice. to big -screen television- though I can't about it, as the author says, is that it He then turns a switch which cuts out and won't believe that it's anything like goes on working indefinitely and just his telephone and brings in an amplifier a final solution of the problem. can't go wrong. All the constants are and loudspeaker. Should there be a tele- given in the diagram so that readers phone call for him, he receives a warn- AM versus FM who care to experiment with the circuit ing from the loudspeaker. He then turns In Britain the experts are getting can make it up and see for themselves the switch to the telephone position and heated up almost to the assault -and- what sort of goods it delivers. takes the call. SEPTEMBER, 1948 a11ni. Modern Phono Oscillators By RICHARD L. PARMENTER

CONSISTING of few parts and used for the rectifier. A tube rectifier aluminum. A piece 4 x 41/_ inches was only one tube, this little phono such as a 35W4 could have been used bent, resulting in a simple L- shaped oscillator will enable the user to but the writer believes that the selenium Ease. Cookie sheets make good stock for play records through any broad- type is a better performer over a long this. This is ample to house the parts cast radio with no external connections. period of time. Also, the output vo tage although, as Fig. 2 shows, they are corn- is somewhat higher, resulting in sli'htly SW power is an 12BE8 20-50 greater output. This advan- 50µ0f U1v SEL MCI 75YA tage since only a short piece of wire AC need be used for the antenna. 15 inches 1-4500f of wire gave satisfactory results when 00025 7i placed inside the changer cabinet. The 12BEG oscillates at some fre-

00 quency in the broadcast band. Modula- tion is applied to the No. 3 grid (see Fig. 1.) The output of the average crys- 00V 700n/20e tal pickup is enough to modulate the r.f. output. The frequency of the oscillator Fig. Schematic of the l -tube oscillator. I- is determined by the coil L, the 250 -ttuf Its small size, only 4s2 inches long by mica capacitor and its padder. a 7-45 - Fig. 2 -Parts have to be fitted in carefully. 31/2 inches high and 2,2 inches deep, oaf mica variable. The latter should be enables it to be installed in almost any installed so that it is available for ad- pactly fitted in. The rectifier is mounted record -changer cabinet in some The coil consists of approxi- unused justment. L on top of the chassis (Fig. 3) to allow corner. is 32 enamelled It simple to construct and mately 90 turns of No. for cooling, since this unit dissipates after the initial on a inch Bakelite adjustment of tuning wire %- -diameter some heat. The coil and tube are also to a good spot in the broadcast band it form. Tap the coil about 33 turns from mounted on top. The 7 -45 µµf padder need not be bothered the with again. grid end. condenser is located on the front panel A 75- or 100 -ma selenium rectifier is The chassis used was made from light to allow for adjustment. Two banana jacks are used for phono pickup connections. These are mounted on the front as well as the on -off switch. Two Channels For Hi -Fi The wiring of the oscillator is simple. Keep the line and filament wiring away By P. HEMARDINQUER from the circuits of grids 1 and 3 of the tube to minimize hum pickup. Be USING a two -channel amplifier -one output, a separate speaker is used for sure to observe the correct polarity of channel for the treble and the other each. The bass speaker is 10 inches in the selenium rectifier. for the bass -is one way to obtain a diameter and the treble unit 4 inches. To set the oscillator in the broadcast more lifelike sound quality. The dia- The input from the phonograph or band. first locate the signal. This will gram of such an amplifier is shown. It receiver is fed through a 0.1 -uf capaci- be heard in the receiver as a whistle was developed in France. Instead of tor to the bass channel and through a or a rushing sound when no record is mixing the two channels together in the .001 -uf capacitor to the treble channel. being played. It should be somewhere The feedback network in the bass -chan- on the low- frequency half of the band nel 6F6 (the resistor and capacitor be- with the components used. If the builder tween plate and grid) and the capacitor finds that sonic other portion of the band across the transformer primary help would he better at his location, decrease to discriminate against highs. The small the size of the 250 -ltttf mica condenser coupling capacitors in the treble channel to 200 lgtf or even less. Now pick a spot discriminate against lows. on the band where there are no strong The fields of the two speakers are of stations. By adjusting the padder con- the same resistance in this receiver and denser tune the oscillator to this spot. are connected in parallel as the filter It may be easier to locate the signal TREBLE choke. from the oscillator by playing a record. .001 ..1%a Tonal balance is adjusted by varying the input potentiometers for both channels. (Note -It is very likely that special conditions in France have influenced the design of this amplifier. An American constructor would be likely to use at least a 12 -inch speaker for the bass. and would probably substitute a 6F5 or the Ills triode section of one of the 6Q- series of AC tubes for the near -obsolete 6K5. A push - pull output stage would probably be de- .005 EACH sirable in the bass channel, if not in both. Reversing voice coil connections to one of the speakers will vary the angle of distribution of the high frequencies. -Editor) Fig. 3- Rectifier is mounted above chessis. RADIO -CRAFT for AIIIIio Instantaneous Intercom Selenium rectifier and battery

By HAROLD R. NEWELL tithes eliminate the II'arlil-llp time

THIS intercom is suitable for home, ( LISTEN VASTER PM I I, T2- UNIV.PLATE TO VOICE COIL TRANS office location where the e or any TALK OF noise level is not too high. The cir- rREMOTE PM,

I cuit provides for one master and 72 MI one remote but can be adapted for sev- o' remotes. Each station can call the I la ISS 3Q4 3S4 eral .003 other. I I I P85wH4 CHASSIS 2/6 2/6 The power is normally turned off. In- L___ .003 stant starting is possible because of the -' selenium rectifier and miniature instant - II§ T 2508 3 heating battery -type tubes. There is no IOMEO

standby current and the tubes are being IOC, used only when actually needed. 25V The tube lineup includes a 1S5 as first audio amplifier driving a push -pull out- R 2.58nOw put stage using a 3S4 and 3Q4. These 100 MA SE .RECT + two different tubes are used because Ground symbols in d agram indicate common IITVAC I00/2w they match the bias obtainable from return -no part of the circuit is earthed. CI 1.58 (2 the filament circuit. Although they have 40 T` 35OV"1.20 somewhat different load ratings, they ments. It is bypassed with the 100 -µf work very well together and provide am- section of the condenser block, which Although useful in getting the mas- ple output. includes Cl, C2, and C3. ter's attention this hum may be elimi- The method of obtaining the phase - The talk -listen switch is a 3 -pole, 3- nated by using a four -wire cable, with inverted signal for the 3S4 is the same position positive- acting rotary. The first a separate power- return lead. as used in several commercial receivers. position of the switch is OFF. The re- Note that the circuit ground is sepa- A resistor is inserted in series with the mote speaker is connected as a micro- rated from the chassis by a 0.1 -µf capac- screen of the 3Q4 and the signal de- phone. When the remote power button itor. Though not necessary electrically, veloped across it is passed to the 3S4 is pressed, the amplifier is turned on this helps prevent shock and is common through a blocking condenser. and the remote can call the master. In practice with transformerless power An aluminum chassis 41/2 x 4% x 1% the second position the master may lis- supplies. To make the unit absolutely inches is used for the master station. ten. In the third, the master may talk. safe, the amplifier should be enclosed in On this are mounted a 4 -inch speaker, The master and remote units are con- a wooden cabinet and all external cables the three tube sockets, two transform- nected with a three -wire cable. One wire and leads should be well insulated. ers, volume control, switch, and filter - is the circuit ground, the second for the The author has not found much use capacitor can. The volume control and voice coil and the third for the power for the volume control ; the gain is about the switch are mounted on a bracket at button. When the power button is right as is. If desired, it may be elimi- the side of the chassis. The selenium pressed to call the master, some hum is nated. rectifier is mounted below the chassis. produced because the ground wire is Some adjustment of R may be neces- A 2,500 -ohm 10 -watt resistor is used common to both the audio and a.c. power sary to obtain correct voltages at the to drop the voltage for the tube fila- circuits. tube filaments.

UNOBTRUSIVE HEARING AID One of the reasons many hard -of- hearing people refuse to wear hearing aids is an objection to their conspicuous- ness. This problem has been largely overcome in recent years by placing the r amplifier, microphone, and batteries in one small case which can be hidden in a pocket. However, the earphone is usually quite visible. A new type of receiver developed by the Maico Company reduces the visibility of the earphone almost to zero. In- stead of plugging the phone directly into the ear, it is pinned to the inside of a man's collar or concealed in some part Secreteer compared in size with finger ring. of a woman's clothing or hair. A small chain is attached to it for this purpose. through the lucite tube the quality of (See photograph.) the sound appears to be unaffected. Lis- A thin lucite tube fastened to the re- tening tests on the Secreteer have ceiver conducts the sound to a moulded of flesh -colored plastic but also because proved it very satisfactory. plastic insert shaped to fit inside the it is exactly shaped to the contours of The amplifier measures about 4% x ear. The insert is almost invisible when the ear. 2% inches. The batteries and micro- it is in place, not only because it is made Despite the acoustical transmission phone are in the same white plastic case. SEPTEMBER, 1948 Audio Three Bug -Free Amplifiers

The author presents circuits and data By JOHN W. STRAEDE* for three straightforward amplifiers

N this article descriptions of three most entirely unaffected by changes in acts to a certain extent as a bass - straightforward bug -free amplifiers plate voltage. booster. are given. Their circuits are compar- The pilot lamp connected across the A conventional high -cut tone control atively simple and do not include un- voice coil winding of the speaker trans- is connected between the plate of the necessary parts. They deliver 9, 13 and former gives a small amount of auto- second tube and ground. 20 watts respectively. matic volume expansion but its real use A 47,000 -ohm suppressor resistor is The tubes used in the amplifier of is to act as an output-level indicator. connected directly in series with the Figs. 1 and 2 are a couple - of voltage Another 6 -volt 0.3 -amp lamp is con- 6L6 -G control grid to make the sound amplifying pentodes in followed cascade nected in the negative side of the high - more tolerable when momentary over- by a 6L6 -G developing 9 watts. The rec- voltage supply to prevent damage to the loads occur. tifier is 5Y3 -G 5V4 either a or -G depend- power transformer if an electrolytic con- To eliminate the bass boost, reduce C ing upon the voltage of the transformer denser should to .01 -ltf and increase secondary. break down. The pilot the suppressor If the high -voltage winding light may have to be omitted if a 5V4 -G resistor R to 270,000 ohms. gives about volts per 375 side a 5Y3 -G or other low- impedance rectifier is used, The sixth pin (or an 80) can be used. If the voltage of each tube socket (ex- because switching the set on and off cept the rectifier) is is lower, around 300 per side, the more used as a tie point. when hot may cause the lamp to blow It is definitely not advisable to have efficient 5V4 -G must be used to provide out. a sufficiently high d.c. output. As an parts rigidly mounted -a little slack in One feature not at first noticeable is wiring gives alternative to the 5V4 -G, a metal the elasticity and minimizes 5Z4 the way in which the circuit is designed the chances for resistors and condensers can be employed. give Parallel mixers to a good frequency response. Al- to break down. are used with 270,000 - though there are small plate bypass con- ohm isolating resistors between vol- the densers to r move any r.f. that may be Six tubes, thirteen watts ume controls and the control grid of the picked second tube. up, the plate load resistors are The second amplifier (Figs. 3 and 4) smaller than usual, resulting in an is quite Unusual points in the excel- orthodox, bearing some simi- circuit are the lent high -frequency response. larity to use of grid leak on Bass re- the smaller job in the use of bias the first 6J7, sponse is also good because the decoup- shorting lack of a filter choke, use of volume jacks, high -cut tone control and a - ling network for the 6L6 -G bias supply lack of a expander lamp and a lamp as fuse. filter choke. Advantages of grid leak bias are the saving of a cathode resistor and a by- 1 1.01 AITVAOK TONE CONI pass condenser and lower hum level (be- .°5C 6L6-G cause cathode is grounded.) 3 No filter choke is necessary for ordinary PA use, because a beam tetrode or pentode output valve has a high plate resistance and the plate current is al- Lecturer in electronics and electro.acoustica, Melbourne Technical College, Australia. 226 +365V Fig. I (right)- Schematic of the 9 -waft unit. Fig. 2 (below) -Sockets are for speaker plugs. 20/450V

5V4-G/5Y3-G

CAT H.IN 5V4 ONLY

SW 1 s l IITV AC A pair of 6V6 -G beam tetrodes is used in class AB1. The operating conditions are such as to provide negative regulation (the total current drawn decreases at full volume). Floating paraphase phase inversion is used -a system which gives an automatic near -balance. This system cannot give perfect balance, for if each 6V6 -G grid had an equal signal, there would be no signal to drive the phase -inverter grid. The common cathode resistor helps to bring the system nearer to perfect balance -these resistors have such an effect that if the 150,000 -ohm resistor is shorted the drop in volume is negligible. RADIO -CRAFT for Audio

A 20 percent change in value has no per- .005 IMEG TONEC0NT 6V6-G(2) ceptible effect. Most critical value is that LL_.1_.PNONO 11_ .n3 250K 3.961E6-SEE TEXT +330V of the 6,500 -ohm dropping resistor for 3 NW- 6U7 -G 3 J the 6V6 -G screens. If no wire-wound 2105 resistor is available three 20,000 -ohm, MIKE .01 270K 1.02 00K 1 be connected 2705 -watt carbon resistors can a 410K 5005 r/ in parallel. Although a 3.9- megohm resistor is IOMEG shown as an inverse feedback device, this is seldom used, as the presence of inverse feedback is apt to cause a rise in hum level when the output tubes do not have a well- filtered supply. (Feed- 6J7-GC2) .05 p0K back from the voice coil is less likely to .1 produce a higher hum level but it is not 47K 20/600 easily applied in this circuit). W +265V YN ttZ Decoupling is used for every stage. zoi50av 6.5K/3W The filtering is comparatively poor for the output stage but is better for each 700V CT, 6 5Y3-G preceding stage. The very best of filter- 6.3V 60MÁ ing is necessary for the first tube be- 2 5v 1 tu 06000. cause it is followed by a gain of some- SW

thing like 2,000. 111VAC

Five tubes, twenty watts Fig. 3 (above( -The 6 -tube, 13 -watt amplifier. This five -tube amplifier has a peculiar Fig. 4 (left- Chassis layout of this unit. layout as Fig. 5 indicates. The power - itf a bass is from condenser in series, provides pack section spaced well away the feedback at low the four amplifying tubes. This is to boost by reducing allow in with plenty of mon coupling at high frequencies. This frequencies. it to fit a case of the from 6SC7 grid to 6L6 -G room in the center for a heavy -duty PM allows more effective operation The gain - is 800 so feedback volt- speaker. As in amplifiers, high- frequency tone control. The plate anode about the the previous is by voltage dividers -leak is microphone to -plate feedback circuit is connected as age reduced two grid bias used for the of 3.9- megohm and 47; preamplifier, but unlike the others, a a low- frequency tone control. -one consisting 000 -ohm resistors, and the other consist- filter choke is included so plenty of nega- In the other feedback circuit there are two condensers. One of 500 Rif shunts ing of a 1- megohm resistor and the 270; tive feedback can be used without exces- resistors of the two sive hum. The schematic appears in some signal to ground to reduce the 000 -ohm isolating feedback at high frequencies and thus volume controls. Fig. 6. because of There are two negative feedback cir- provide a high- frequency boost. The .001- If the amplifier is unstable cuits. One is from an output tube plate 6J7 BASS !MEG 6L6-G (23 to a 6SC7 plate. The other comes from 01 TBEBL the other 6L6 -G plate to the 6SC7 input 270K 500K .02 Loot grid, helping to compensate for lack of MIKE 01 10K 5 2505 .002 .05 of Ht--! coupling between halves the output Q 270KY transformer primary. 0011 Al 10Kn inversion is used and the CT Paraphase 3.314E6 .i 1 6SC7 works very well. Formerly a 6N7 5.65 was used, resulting in lower gain. 1li

The cathode of the phase inverter is 27011 2701( bypassed for high frequencies with a --t .05 -µf condenser so that there is no corn- .02 100K 250K 2,705 3.9MEG PN0N0 f WM hum. Fig. 5 (below( -Parts placement reduces 350V 47K 170005 4.75 20/450V Fig. 6 (right(-Amplifier output is 20 watts. { 270K 4450 -3.35 1. 6.3 730v CT 60/5Y3 I00MA .._41_113 tZ

SW pn. ISV 4.:1ji,oi' 117V AC

too much gain or due to phase changes in the feedback circuit, it may be necessary to reduce the size of the 47,000 -ohm resistor or to increase the 1- megohm resistor to around 4 megohms. Two features not found in either of the other amplifiers are the use of an r.f. suppressor, a 10,000 ohm resistor in series with the grid of the 6J7 -G, and the application of a positive voltage to the heaters of the tubes to reduce heater emission, a common cause of hum. This amplifier is very suitable for recording. SEPTEMBER, 1948 44

The next time you hear voices tJSTN I

IT MAY BE your conscience speaking. It may be saying: "Save some of that money. mister. Your future depends on it!" Listen closely next time. Those are words of wis- dom. Your future -and that of your family -does c depend on the money you put aside in savings. c If you can hear that voice speaking clearly, do this: c

Start now on the road to automatic saving by c signing up on your company's Payroll Savings Plan for the purchase of U.S. Savings Bonds. There's no better, no surer way to save money. Surer because it's automatic ... better because it pays you back four dollars for every three you invest. Do it now. If you can't join the Payroll Savings Plan, tell your banker to enroll you in the Bond - A -Month Plan that enables you to purchase a bond a month through your checking account. Remember - better save than sorry!

Automatic saving is sure saving V$.Svinqs bonds

Contributed by this magazine in cooperation with the Magazine Publishers of America as a public service

RADIO -CRAFT for Test Instruments

The A. C. Ammeter Saves Testing Time

By JOHN MELICHAREK

FEW radio technicians realize the ceiver that is working properly. Remov- amount of time and labor that can ing the rectifier tube chops the reading be saved by using an a.c. ammeter to 45 watts (.38 amperes). Pull out the in radio servicing. A.c. ammeter power amplifier tube and the reading ranges are seldom included in multi - drops to 55 watts. A burned -out output testers; however, it will be worth your transformer or burned -out field coil The ammeter mounted in the back of the bench. while to purchase a 0- 1- ampere a.c. drops the consumption to 60 or 50 watts. meter for your shop. If you use it intel- Five -watt drops are easily seen on the ceiver, when first turned on, draws only ligently, you can often save hours that meter. Drops of 15, 20 and 30 watts can about one half of its rated current; the would otherwise be spent in tracking easily be diagnosed with just a little current begins to increase as the tubes down false clues. I use one to check experience. If the drop were only 5 or reach operating temperature. every set that comes into my shop. 6 watts, you would not need to check or A 40 -watt a.c. -d.c. receiver draws only I have a 7 -inch 1- ampere meter in suspect the speaker field, choke coil or 22 watts when it is first turned on. The series with one side of the power recep- rectifier tube. current begins to rise as the tubes heat tacle to which I connect all sets for their Like other test instruments, the meter up, and if nothing is shorted, the needle initial testing. Most sets have the nor- will not show you everything. A 6K7 will stop around the 40 -watt mark. If it mal power consumption, in watts, tube with an open heater will cause should continue beyond the 40 -watt marked on a plate or tag on the chassis about a 5 -watt drop; but an open plate mark a short is indicated and the power or cabinet. I convert this wattage rating or screen supply will not show on the should be cut off immediately. Almost to amperes (I -W /E) and compare it meter. It takes at least 20 ma at 100 any short in the filter section will cause with the reading on the meter. When the volts to give a good indication. the 40 -watt receiver to draw 100 watts. reading is higher or lower than normal, If the radio has a high -current short This shows why a rectifier tube can burn it can be used as an indication of pos- the meter immediately shows it. Shorted out or go bad in a few minutes. sible sources of trouble. filters and bypass condensers are the The important point is to watch the Two troubles are common in radio re- two main offenders. Readings will be meter needle with one hand on the ceivers. A component burns out or opens from 80 to 200 watts. Shorted filter con- power switch. Be ready to cut off the or develops a short. Your servicing job densers show up almost instantly, while power if the needle goes beyond its becomes much simpler when you know shorted plate and screen bypass con- mark for a normal set. The needle may which of these conditions exists. The densers do not show up until the filters take from 10 to 30 seconds to come to facts are clearly defined for you by the are charged. rest. A longer period may be caused by a.c. ammeter. Just plug in the receiver, When servicing a.c. -d.c. receivers, the high resistance in the filament string turn on the power and read the trouble ammeter shows the continuity of the or poor rectifier tubes. If the rectifier on the meter. filament string and the current drawn is bad (not burned out) the needle will To clarify this, consider a 75 -watt re- while the set is heating up. An a.c. re- not move off its starting point -a sure indication of what is wrong. The meter shown in the picture is a G.I. souvenir that I brought back from Germany. It is a French 1- ampere meter, with a 7 -inch scale. A meter this size is preferred because the divisions will be around 3 times larger than for a 4 -inch meter. It can easily be read from a distance. Still, I would settle for a 2 -inch meter rather than none at all. The most important feature of the meter is its range. 1 ampere is about equal to 115 watts. This will take care of most receivers up to 12 tubes (less phono motor). A 2- or 3- ampere meter will not be sensitive enough, unless you are servicing electronic equipment which draws 1.5 amperes or more. Many radios develop serious shorts which will cause 2 or 3 amperes to be I' l' i : drawn in some cases even more. Always protect your with .4upllrxrrvl by E. R. Donohue, Walla M'alla. 1Vaah. instrument the proper fuse; for a 1- ampere meter, use a 1- Steps in the education of a Radio Man. ampere fuse. SEPTEMBER, 1948 46 Test Instruments This instruiiten t has a novel eon- denser checker plus signal genera e or-tracer & multimeter

By V. A. JEANNOT

This small test instrument is ideal for outside service calls. All parts fit into the case. Versatile Tester Has New Features

THIS is an ideal test instrument for with a 150 -turn primary of No. 24 used to cover the i.f. and broadcast' experimenters and for radio serv- enamel wire. This is covered with a ranges with a small 365 -ttttf variable icemen to use on outside servicing layer of Scotch tape and the remaining condenser. The low -frequency coil has calls. It is a combination test oscil- space filled with as many turns as pos- 500 turns of No. 30 enamel wire scram- lator, signal tracer, condenser tester, sible of No. 30 enamel wire. The relay ble -wound on a % -inch form and the multimeter and continuity and polarity contacts are wired so the unit will work broadcast coil 60 turns of No. 28 enamel tester. It is inexpensive and can be built as a vibrator or buzzer. When the push- wire on a 3/4-inch form. Both coils are into a case 7',z x 5 x 3 inches. A case button switch S4 (marked TCS on the center -tapped. The low -frequency coil this size includes ample space for a few front panel) is pressed, a high -voltage may be the secondary of an i.f. trans- replacement condensers, resistors, fuses high -frequency current is developed in former designed to work into a full - and other essential accessories. the secondary of the vibrator- transform- wave detector. This coil is mounted in- The condenser tester (for testing er. The secondary is connected to pin side one end of the large coil form. Coils paper and mica condensers for shorts) jacks marked T -C through S5B when are selected by a d.p.d.t. switch, S3. is novel. The basic circuit is shown in it is in position 11. The 1S5 is also used in the signal Fig. 1. The condenser is placed in a tracer circuit; when using the oscillator high -frequency high- voltage circuit in Test Oscillator S2, a d.p.d.t. switch, should be in the series with a neon lamp. One electrode The test oscillator or signal generator Osc position. Filament voltage is turned of the lamp glows as the condenser is a Hartley oscillator using the pentode on with SI in the A.C. VOL position. charges and the other glows as it dis- section of a 1S5. This is shown on the B- voltage, from a hearing- aid -type B- charges. This action is so rapid that complete diagram, Fig. 2. Two coils are battery, is applied through a switch on both elements appear to glow at the the r.f. output control. Output is ob- same time. If the condenser is shorted, 1.5v ¡ 1.5v S4 tained through an open- circuit jack on only one plate will glow. several -+ - + (Carry I IéTR the panel. A shielded output cable car- good condensers in the spare parts com- T 558 II ries the signal to external circuits. The partment and shunt them across con- I/ W NEON p shield is as a II used common return. No densers suspected to be open.) modulator is used. The values of the The high- frequency voltage for the grid leak and condenser -1 megohm and test is developed in a vibrator trans- .001 id-are selected to cause audio former made from a small relay. The MEG blocking or squegging at an audio rate original coil is removed and replaced Fig. I -The condenser checker is unusual. (Continued on page 48) RADIO -CRAFT for 47

GUARANTEED QUALITY AN ACCURATE POCKET SIZE TUBULAR CONDENSERS An example of the value we offer, the VOLT -OHM MILLIAMETER 20/20 150 V condenser listed below (made us by a famous VOLT) for nationally (SENSITIVITY: 1000 OHMS PER manufacturer) lists at $1.30, our selling price is only 26c. FEATURES ' PER HUNDRED * Compact -measures 344" x 5T.í" x 2%". .001 600V $3.95 * Uses latest design 2' accurate 1 Mil. - D'Arsunval type meter. . 002 - 600V 3.95 * Same zero adjustment holds for both resistance ranges. It is nut necessary to . 003 600V 4.40 re- - readjust when switching from one sistance range to another. This is an .005 600V 4.40 be- - important time -saving feature never price 4.40 fore included in a V.O.M. in this .006 - 600V range. .01 600V 4.40 * Housed in round- cornered, molded case. - * Beautiful black etched panel. Depressed . 02 600V 4.95 letters filled with permanent white, in- - sures long -life even with constant use. .03 - 600V 4.95 600V 4.95 SPECIFICATIONS .05 - . 1 600V 7.20 6 VOLTAGE RANGES: - A.C. 0- 15.30.. 150. 300: 1500 3000 VOLTS EACH 6 D.C. VOLTAGE RANGES: 750, 1500 VOLTS .12 0.7.5. 15 75,150 .25 - 600V 4 D.C. CURRENT RANGES: . 5 600V .17 0.1.5 15 150 MA 0 -1.5 AMPS. - 25V .14 2 RESISTANCE RANGES: 5 - 0.500 OHMS 0 -1 MEGOHM 10 - 25V .16 The Model 770 comes complete with 25 25V .18 NET - self-contained batteries, test leads and all operating instructions. '13'"' 10 - 50V .22 100 - 25V .29 16 - 150V .18 20 - 150V .24 RADIO TUBES - SI ; NDARD BRANDS - BULK 20/20 - 150V .26 All brand new, car supplied free with each tube 30 - 150V .28 40/20/20- 150V -25V .44 OZ4 ....$ .65 6H6GT . .49 12SF5(:T .49 24A .... .54 1A5GT . .59 6J5GT .49 12SF7GT .69 26 .49 40/40/20- 150V -25V .44 lA7GT . .59 6J6 .85 12SJ7GT .49 27 .54 50/30 - 150V .44 1H5GT . .59 6J7GT .. .55 12SK7GT .49 35/51 .59 4 450V .24 1N5GT . .59 6K6GT . .49 12SQ7GT .49 36 .74 - n.A4 ... .95 6K7GT . .55 12SR7GT .49 37 .49 8 - 450V .27 11.A6 ... .95 6L6(: . . . .95 14 A 7 ... .69 :38 .59 16 450V .36 . - 39/44 1134 ... .95 6Q7GT .55 1466 ... .69 .54 16/16 450V .59 1LC6 ... .95 6SA7GT. .49 14Q7 ... .69 41 .59 - 11,1)5 ... .95 6SC7 . . .55 25A6G . 1.15 42 .69 20 - 450V )39 11,E:3 ... .95 6SF5GT. .59 25L6(.T . .59 43 .59 30 450V .47 1LH4 ... .95 6SH7 ... .55 25Z5 . .55 45 .59 - . 40 450V .59 1LN5 ... .95 6SJ7GT .49 25Z6GT . .47 46 .74 - 1Q5GT .. .95 6SK7GT. .49 32L7GT . .95 47 .74 80 - 450V .97 1R5 .... .79 6SL7GT. .74 35A5 ... .65 49 .95 .005 1700V .13 1S4 .... .69 6SN7GT. .59 35B5 .65 50 .95 - 1S5 .... .65 6SQ7GT. .49 35I (1' ...55 53 .74 .008 - 1700V .15 1T4 .... .65 6V6GT . .69 :5W4 ... .45 55 .71 .01 1700V .17 6X5GT . .65 56 .59 - 3Q4 .... .69 35Y4 ... .69 .02 1700V .19 3Q5 .... .69 7A8GT . .79 35Z3 .84 57 .65 - .74 3S4 .... .69 7B7GT . .79 35Z5GT . .45 `8 .05 - 1700V .21 5U4G ... .59 7C5 .... .79 50A5 ... .85 !15 .05 2500V .58 5V4G ... .85 7C6 .... .79 50135 .55 71A .74 -

. .... 75 .59 .1 2500V .64 5Y3GT .42 7F7 .79 50L6GT . .55 - 5Y4GT . .55 7Y4 .79 50Y6GT. .74 76 .49 .25 - 2500V .86 6A7 .59 12A8GT. .75 70L7GT . .95 77 .49 . . .49 .05 3000V .69 6ARGT . .59 12AT6 .49 117L7GT 1.15 78 - 6AC7 ... .85 12AU6 .. .75 117P7GT 1.15 79 .85 .003 - 5000V .57 6AK5 ... .75 12BA6 .. .49 117Z3 .95 80 .42 .005 5000V .62 6:CL5 ... .85 1213E6 .. .49 117Z6GT .95 81 1.55 - .01 5000V .74 6C4 .... .42 12J5GT . .49 82 1.15 - 6C6 .... .49 12J7GT . .69 TELEVISION 83 .64 .0005 7500V .58 Kinescopes 84 - 6D6 .49 12K7GT. .74 .69 .003 7500V .67 6F5GT . . .49 12Q7GT. .74 7 E P4 ...17.40 85 .. .59 -

6F6GT . . .49 12SA7GT .49 10ßP4 ..34.50 89 .69 .0005 -10000V .64

BROOKS RADIO DIST. CORP., 80 VESEY ST., Dept. A) NEW YORK 7, N. Y.

SEPTEMBER, 1 91 8 Test Instruments 48 I

(Continued from page 46) full scale. We then shunted the meter meter scale. Ranges, selected with S5, The modulation note is about 250 cycles. terminals with short lengths of copper are 0 -50- 250 -1,000 volts d.c., 0 -50 -1,000 The meter we used has a 500 -µa or manganin wire until the meter read volts a.c., 0 -5 -50 -250 ma d.c., and 0 -150; (0.5 -ma) movement. We removed its half scale. The resistance of the shunt 000 ohms. scale and replaced it with a multitester was measured with a borrowed ohm- Alternating voltages are measured by scale of the type available from well - meter. The resistance of the shunt is using the meter in conjunction with the stocked radio parts stores and mail -or- equal to the resistance of the meter. diode of the 1S5 when S1 is on A.C. VOL. der houses. The internal resistance of With the meter resistance known, shunts One section supplies 1.5 volts for the the meter was unknown so it was de- for the various ranges were computed filament from one of the penlite cells termined by experiment. from the formula: and the other connects the diode to the The meter was connected in series meter through shunts R »Muni= R,,, /N -1 and multipliers. with a 1%-volt battery and a 5,000 -ohm The unmarked shunts and múlti- wire -wound potentiometer. The resist- where R,, is the meter resistance and N pliers are selected according to the ance was reduced until the meter read is the factor by which the basic meter meter used. Series multipliers are metal- range is to be multiplied. The basic lized resistors and shunts are hand - ¡- SIG TRACER PROBE range is 500 µa so the multiplication wound to the proper values on small factors (N) are 10, 100, and 500 for the bakelite strips. 1-5MEG 5 -, 50 -, and 250 -ma ranges respectively. When measuring resistances, the 500µA Voltage multipliers are designed to meter is connected as a series -type ohm- ACV limit the current to the basic range of meter consisting of the meter, a 1,000- OS5TC the meter when full -range voltage is ap- ohm rheostat (zero -ohms adjuster) and Wrf plied. The resistance is equal to the volt - the 2 penlite cells in series. Resistances Ioo..-- 7e R}Fa, MEG 12e 110 age range divided by full -scale current up to 150,000 ohms can be measured. S2 (.0005 ampere). Be sure to subtract the To test condensers, set S5 on position SSA meter resistance from the resultant. 11, plug prods into jacks marked T -C and close pushbutton switch S4. Signal Tracer Continuity tests are made with S5 on 500K 4 As a signal tracer, apply plate and position 12, SI on D.C.V. /OHMS and filament voltages 2 MEG ISS and throw S2 to ST. This connects of the grid the tube to the ISS probe and the plate to B -plus through 500 u ACV. a single earphone unit. The phone is by-

D02rIN PHONE JPHONE 2 passed with a .002 -µf capacitor mounted S 5 in its case. The probe is made from a B BATT 270 30-33V + -seioN/N- phone plug. The metal tip is cut off close tc the end of the barrel and replaced 9 10 II 12 - p1 IF., with a long brass S5 A SW IN RF screw that has been RFK 55 B CONT filed 15v OUT to a sharp point. This screw is t CONI insulated from the metal end of the bar- VIII TRANS .001 = rel. A .0001 -µf ceramic condenser and a SEE TEXT 4- or 5- megohm resistor are mounted in- 3V BULB side the barrel of the probe. The shield IOOK 500K 1 RI OUTPUT JACK" T of the r.f. is IK /W W /OHMS ADJ T /.91) C 114 OHMS ADJ cable a ground connection OHMS/VOLTS/MA LIGIIT,VOLTS, CONO TEST between the tester and the set. SSA t SSD GANGED MA, OHMS A break-down diag am of the multitester unit. Multitester Fig. 2 -The complete diagram of the fester. prods plugged into the multimeter jacks. SI is "up" for a.c. volts, oscillator and signal The multitester section is constructed This places a 3 -volt flashlight bulb in tracer and "down" for d.c. volts and ohms. around a 0.5 -ma d.c. meter with a multi- series with the prods and the penlite cells. This section is useful in repairing shorted variable condensers. When the tester is set for condenser tests, it can be used as a polarity indicator by connecting prods to the external d.c. voltage and noting which electrode of the neon lamp glows when the positive prod is connected to a known positive voltage. Both plates glow on a.c. When testing for polarity of an external voltage do not press S4. Wiring the range switch, S5, is perhaps the most difficult operation in the construction of the tester. This is simplified by wiring each deck separately. Functions for the various positions are: Position Function 1. OFF 2. 50 v.d.c. 3. 250 v.d.c. 4. 1000 v.d.c. 5. 50 v.a.c. 6. 1000 v.a.c. 7. OHMS 8. 5 ma d.c. 9. 50 ma d.c. 10. 250 ma d.c. 11. Condenser Test (TC) Rear view of the fester. Note the vibrator below and to the right of the wafer switch. 12 Continuity (L) RADIO -CRAFT for -19

MONEY BACK GUARANTEE - We believe units offered for sale by mail order should be sold check the design, and value u only on a "Money- Back -If- Not -Satisfied" basis. We carefully calibration of all items advertised by us and unhesitatingly offer all merchandise subject to a return for credit or refund. You, the customer, are the sole judge as to value of the item or items you have purchased.

THE NEW MODEL 670 The New Model 770 - An Accurate Pocket -Size SUPER METER VOLT -OHM MILLIAMMETER (Sensitivity: 1000 ohms per volt) SUPER METER. A Combination Features: VOLT - OHM - MILLIAMMETER Compact -measures 3%" x 5! " x 214 ". plus CAPACITY REACTANCE. Uses latest design 2 i accurate 1 Mil. INDUCTANCE a n d DECIBEL D'Arsonval type meter. Same zero ad- MEASUREMENTS. justment holds for both resistance ranges. D.C. VOLTS: 0 to 7.5/15/75/150/750 / It is not necessary to readjust when 1500/7500. A.C. VOLTS: 11 In 17/30/ switching from one resistance range to 150/300"1500/3000 Volts, O U T P U T another. This is an important timesav- /1100/70110, VOLTS: o io 15!30/150'300 ing feature never before included in a D.C. CURRENT: n to 1.5/15/110 n V.O.M. price Housed in 0 to 1.5 Amps. RESISTANCE: 0 to 500/ in this range. 100.000 Mims. 0 to 10 Slegohms. CA- round- cornered, molded case. Beautiful PACITY: .001 to .2 Slfd., ,l to 4 Mfd. black etched panel. Depressed letters (Quality test for elrrtrolyllen.) REACT- filled with permanent white, insures long - ANCE: 700 to 27,000 Ohms: 13.000 Ohms life even with constant use. to 3 Megohms. Specifications: 6 A.C. VOLTAGE RANGES: INDUCTANCE: 1.75 to 70 Henries; 35 0.18 /30, 11t. 3011, 1/01/31011 sols. to 6,11011 Ii inries. 6 D.C. VOLTAGE RANGES: 0 -7'1: I-. 511 xoltc. DECIBELS: - Ill to +18. +10 to +38, 1511- /1500 n :11 4, +86. 4 D.C. CURRENT RANGES: 51a. 0 -l'a Ami, . housed in a rugged, The model 670 comes 2 RESISTANCE RANGES: 0 -5un crackle -finished steel cab- Sie -e0u1. complete with test The Model 770 comes complete inetinet and operating in-i with sell-contained batteries, truetions- Size 5'/:" NET test leads and all ing 7/ "x3". 52 V40 instructions. 390NET The New Model 606 THE NEW MODEL 777 TUBE & SET TESTER 20,000 OHMS PER VOLT!! A COMPLETE TUBE TESTER Tests all tubes including the new post -war miniature loctals such as the 12AT6, emission & SET TESTER by the well.established TUBE 12/1U6. 35W4. 5085. 11723. etc. Tests Tests shorts method for tube quality. 1 re-tly read on the scale of the meter. Tillie Tester Specifications: of any and leakages up to 3 hlegohms in all tubes. Tests leakages and shorts * 'ruts all tubes including New Miniatures. etc. Also Pilot Lights. one element gainst all elements in all tubes. Tests both plates in rectifiers. l.. -ts by the well -established emission method for tube quality, Tests individual sections such as diodes, triodes. pentodes. eta in multi- * -mn +n:Jn of the meter. New type line voltage. purpose tubes. ui. r.1I the * A COMPLETE MULTI-METER V.O.M. Specifications: D.C. VOLTS: tat 20.000 Ohm, fi D. C. VOLTAGE Per Voltl. 0 to 7.5/15,75/150175n RANGES: 0 to 7.5 15 75, 1.100 Vous. 150 757 1.560 Volts 6 A.C. VOLTAGE RANGES: 0 to A.C. VOLTS: (At 10.000 Ohm, 15 30 ILO 300 '1.5.0 3.000 Per Volt). 0 to 15/30/1311 30n Volts 4 D.C. CURIIENT 1,500/3,000 Volte. RANGES: 0 to 1.5 15 151 Ma. 0 to 1.5 Amps. LOW D.C. CURRENT: 0 to 1.5/15 RESISTANCE RANGE: 0 to 150 11a. II to 1.5 Amperes. 2.000 Ohms 11st dioi;ioa RESISTANCE: 0 to 5,000 /50 is I 10th of an ohm.) 2 000/500,000 Ohms. 0 to 50 Meg- MEDIUM RESISTANCE ohms. RANGES: 0 to 20.n00 200.(0) Ohms NIGH Model 777 n 90.120 volts GO cycleses A,C.A.C. Moused .n RESISTANCE RANGE: beautiful hand -rubbed cabinet. 0 to 20 Megohms 3 Complete with tat load DECIBEL RANGES: d detailed 95 trued -10 to +38 +10 to 9opera. to D.B. Lions, Size 13- +38 +30 +58 121y , NET

Model 606 tomes housed in a beautiful hand rubbed $4785 oak cabinet complete with portable cover. b-st leads. NET The Model 88 -A COMBINATION tube charts, and detailed operating instructions

The Model S -35 a POWERFUL SIGNAL GENERATOR AND REFLEX PROJECTOR TRACER COMPLETE N -ITII ISt'ILTIN DRIVER UNIT CONSERVATIVELY SIGNAL Signal G RATED AT 35 W VI-TS-HANDLER UP TO 55 WATTS WITHOUT Specifications: BLASTING. DRIVER UNIT MEG. BY WESTERN ELECTRIC. Frequency Range: 150 Kilo- cycles to 60 Megacycles. 'The Rea :dni In 1 hr r . eliminates blast- R.F. Signal Frequency is kept Inc s andl blaring. ,I1 New pl:utie , peaks of the old type; also It is absnhn, I, I, hantes whereas the completely constant at all out- std ISIl l' w .ubreet to atmospheric cor - put levels. Modulation is ac- l'Xnlh9r lldt tnmlitiunally complished by Grid -blocking ac- guaranteed for one -ear . m tion which is equally effective for alignment of amplitude and Specifications frequency modulation as well as POWER (CONSERVATIVE) - 35 for television receivers. R.F. ob- WATTS: AIR COLUMN -3'ç FT.: tainable separately or modu- DISPERSION-8V: POWER 'PEAK) lated by the Audio Frequency. - WATTS: BELL DIAMETER- -55 Signai Tracer Specifications: -15"; IMPEDANCE -8 ohms: FRE- 'Uses the new. Sy,21112 IN04 Orr QUENCY RANGE -130 to 5000 titanium crystal Oimlr which min C.P.S. PROJECTION -'/a mile: bined with a resistance- capacity network prnrides a fre- FINISH - Attractive quency two tone crystalline. rmge of 300 cycles to 50 -Megacycles. The Model S -35 Comes 52850 Complete with Built -in The Model 88 comes complete with all t est leads and operating Driver Unit. ONLY instructions. ONLY NET 20'; DEPOSIT REQUIRED ON ALL C.O.D. ORDERS

PARK PLN. Y. GENERAL ELECTRONIC DISTRIBUTING CO. NEW YORK 798

SEPTEMBER, 1948 Test Instalments Bridge Measures I. -C -I1

Building au accurate iuslrumeul

for measuring rad io pa res. alues By RUFUS P. TURNER

FOR good all -around flexibility and under test. Signal voltage is injected 2 100 -ohm resistors dependability, the skeleton -type im- into the bridge through jack J1, and the 2 1000 -ohm resistors pedance brio7e is unecual!ed for null detector is plugged into jack J2. 2 10,000 -ohm resistors reliable resistance, capacitance, and While any 10,000 -ohm wire -wound 1 0.0001 -pf capacitor inductance measurements. It is distin- rheostat or potentiometer might he used, 1 0.001 -pf capacitor guished from other L -C -R bridges in a rheostat having a logarithmic taper 1 0.01 -uf capacitor that it employs plug -in standards that affords an open, easily readable dial. 1 1.0 -pf capacitor reduce the errors caused by stray Ordinarily, logarithmic rheostats are The accuracy of the bridge depends capacitances in the range -switch circuits rather costly, but an excellent compon- upon the accuracy of these standards. ordinarily employed in home -made L -C- ent of this type recently has appeared Precision, non -inductive wire -wound re- R bridges. in the surplus market at a very low sistors should be employed (they are not price. expensive) and the capacitors should The skeleton bridge described in this have at least a l': accuracy rating. article is patterned after the discon- tinued General Radio type 625 -A and is Construction 4 a siml+.ification of a similar bridge previously developed by the has The author's bridge (See Figure 2) is TO DETECTOR author.' It the fo,lowing ranges: resistance, .01 built in a standard 6 x 6 x 6 -inch steel J2 CLOCKWISE box. The posts take wire leads ohm to 1 megohm in 7 steps; capaci- terminal 10K and banana tance, 1 µµf to 100 pf in 7 steps; induct- jacks. input J1 a female 2- ance, 1 ph to 100 h in 7 steps. Signal jack is terminal connector. Bridge output jack The bridge ranges may be changed J2 is a female co -axial connector. Differ- LOGARITHMIC by p1u -ling in standard resistors and TAPER ent types of jacks are used because CASE capacitors of appropriate value (see the input and output terminals of the n Tables 1, 2, and The dial of 3). the bridge cannot both be at ground poten- rheostat (Fig. 2) can be read directly in tial without short- circuiting the rheo- SIGNAL INRIT ohms. micromicrofareds, microfarads, stat. which would be the case if co-axial mif ' or Fig. 1-Schematic shows simplicity of bridge. henries, millihenries, henries. jacks were used in both positions. The :ollowing standards are required The bridge has plug -in terminals in for .o '.ete coverage of the resistance, The dial is 3' inches in diameter three of its four arms. By simply shift- cap:uitance. and inductance ranges: and has a metal skirt. A disc of thick ing the standards and the unknown com- white drawing paper is cemented to the 1 1 -ohm resistor ponent among these terminals, the metal disc and the graduations from 1 10 -ohm resistor bridge may be converted from the zero to 10 (see Fig. 2) are draw on this Wheatstone type (for resistance meas- See Radio Test I usl non rn is by Rufa. P. Turner paper. urements) to the Wien type (capaci- The standard resistors and capacitors tance) or to the Maxwell type (induct- should he mounted inside small boxes or ance). cans provided with banana plugs that Any convenient signal source, such as fit into the terminal posts of the bridge. an audio oscillator or the low- voltage Wiring must be done with stiff bus output of a 60 -cycle filament transform- wire run by the shortest route between er, will supply a.c. input to the bridge. circuit points. Fig. 3 gives a clear view Any convenient null detector may be em- of the simple wiring. Be sure to connect ployed. Satisfactory null detectors in- the rheostat so that resistance increases clude headphones, audio amplifiers with with counter -clockwise rotation. electron -ray indicator tubes, oscilloscopes, and a.c. vacuum -tube voltmeters. the In some instances non -electronic a.c. Calibrating bridge The skeleton bridge is voltmeters have been used with some calibrated by rt success. When making resistance meas- marking the rheostat dial in resistance urements, the a.c. signal source and de- units. Connect to terminals 1 and 2 a tector may be dispensed with and a bat- well -calibrated ohmmeter or a resistance tery connected to the bridge input ter- bridge of good quality. Temporarily con- minals; a center -zero d.c. microammeter nect wire jumpers between terminals 3 or bridge galvanometer may be connect- and 4 and between terminals 5 and 6. ed to the bridge output. Rotate the knob until the ohmmeter The skeleton -type bridge is easy to or external bridge reads 100 ohms. Mark build and calibrate. The circuit is shown this point on the scale. Repeat at as in Fig. 1. The only adjustable element is many points as possible between zero the rheostat, which carries a direct - and 10,000 ohms. Remove the jumpers reading dial. The terminals, 1 -2, 3 -4, from the bridge terminals. Remove the and 5 -6, are provided for plug -in stand- dial from the rheostat shaft and ink in ards and the resistor, capacitor, or coil Fig. 2- Bridge is built in square steel box. the lines permanently. Mark the 1,000- RADIO -CRAFT for .11

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_Zà*ite Onayd N AME......

100 SIXTH AVENUE, NEW YORK 13 229 W. MADISON STREET, CHICAGO 6 AOOSESS..... 265 PEACHTREE STREET, ATLANTA 3 110 FEDERAL STREET, BOSTON 10 24 CENTRAL AVENUE, NEWARK 2 542 EAST FORDHAM ROAD, BRONX 58 ITY ZONE.... STATE...

SEPTEMBER, 1 9 4 8 52 Test Instruments ohm point 1, the 2,000 -ohm point 2, and so on up to 10. Then carefully replace TABLE I TABLE 2 the dial. Resistance measurement Capacitance measurement The of will accuracy the calibration Range Terms. I -2 Terms. 3-4 Range Terms. I-2 Terms. 5-6 depend upon the precision of the exter- (ohms) (ohms) (ohms) nal meter or bridge used, the care with (ohms) (µf) which the dial points are inscribed, as .I-1 10,000 1 -100 µµf 10,000 .0001 0.1-10 10,000 10 10 -1,000 µµf 10,000 .001 which dial is well as the care with the 1-100 10,000 100 100 µ)sf -.01 µf 10,000 .01 replaced on the rheostat shaft after ink- 10-1,000 10,000 1,000 .001 -0.1 µf 1,000 .01 ing. 100-10,000 10,000 10,000 .01 -I µf 10,000 I

1,000-100,000 1,000 10,000 0.1 -10 at 1,000 I

10,000-1,000,000 100 10,000 1 -100 µf 100 1 Connect unknown resistor to terminals 5 -6. Connect unknown capacitor to terminals 3 and 4. mined by means of the formula, Power Factor ('r ) = .000628 fRC. where f is 3 and 4, R. is the resistance of the main the bridge signal frequency in cycles, R bridge rheostat at its null, and R is the is the resistance of the auxiliary rheo- resistance of the auxiliary rheostat at stat at its null, and C. is the value of its null. Use the shortest possible leads the unknown capacitor in microfarads. between the rheostat and the bridge ter- A sharp null often cannot be obtained minals. in inductance measurements because of To check resistance by the d.c.-bridge the resistance of the coil under test. To method, connect a 1'/2- to 41/2-volt bat - improve this situation, a calibrated rheo- ery to jack Jl, and a zero -center d.c. stat, R, is connected in parallel with the microammeter (100 -0 -100, 50-0 -50 or standard capacitor and bridge terminals lower) to jack J2. Connect a pushbutton 5 and 6, Fig. 6. R then is adjusted along switch in series with the battery and J1. Set up the bridge for resistance according to Table 1. As the bridge dial is rotated, depress the pushbutton intermittently, noting whether null is ap- Fig. 3- Wiring is rigid and leads are short. proached. As the meter deflection ap- proaches null, the pushbutton may be Operating the bridge held down safely. Exact null, of course, An a.c. signal is used for most meas- is indicated by zero meter deflection. urements. This is supplied in most cases by an audio oscillator. Connect the oscillator and the null detector to the bridge TABLE 3 with short lengths of flexible shielded (Inductance measurement) cable. Fig. 4 shows the bridge supplied Range Terms. 3-4 Terms. 5-6 by an audio oscillator and connected to (ohms) (µf) an oscilloscope used as the null detec- Fig. Bridge used with generator 'scope. 4- and I tor. This is a very sensitive arrange- 1-100 ah .01 with the bridge dial to give the sharpest 10-1,000 µh 10 .01 ment. 100 µh-10 mh 100 .01 Plug in the standards and connect the null. At this point, the equivalent series 1-100 mh 1,000 .01 unknown resistor, capacitor, or inductor resistance of the coil may be determined 10-1,000 mh 10,000 .01 by formula, Equivalent Re- as indicated in Tables 1, 2, and 3. Ad- the Series 0.1-10 h 1,000 I just the rheostat for a sharp null. Read R.R,. 1-100 h 10,000 the resistance, capacitance, or induct- sistance (ohms) = where R, is the Connect unknown coil to terminals I -R and 2. ance of the unknown from the dial, according to the range given in the table. standard resistor connected to terminals If no null is obtained with a given set of standards, change the standards to the next range. Very often, a sharp null is not obtained during capacitance checks. This is due to capacitor power factor. For sharpening the null and for measuring the power factor, the scheme shown in Fig. 5 is recommended. A calibrated

STANDARD CAPACITOR

R CALIBRATED RHEOSTAT

BRIDGE TERMINALS S B 445 fig 6 Fig. 5 -Extra rheostat measures power factor. Fig. 6- Adjust R for the sharpest indication. rheostat, R, is connected in series with the standard capacitor and bridge terminals 5 and 6. The rheostat must be connected by the shortest possible leads. R is adjusted along with the bridge dial until the sharpest null is obtained. At this point, the power factor of the capac- "The sign means RADIOS, you muffinhead!rr itor under measurement may be deter- RADIO -CRAFT for 53 ---.r Your CREI Training is DOWN PAYMEN t-yam; s` MORE MONEY, ON PROMOTION, SECURITY

Train With One of America's

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CREI Training Cari Help You to a Better -Payin . Job!

EVERY WEEK letters from students and graduates not drop you off at the elementary job training tell us of new pay increases and promotions that phase. You quickly advance lesson -by- lesson to the are made possible through the help of modern more advanced study of engineering principles technical training with CREI. and practice. The courses are practical, authorita- Said one man recently: ". . . I am happy to tive and easy to follow. report that in the past seven months with Station K - - -, I have received three increases in salary and Your future success can be assured by the plans a promotion which can be partly credited to CREI." you make today. Just figure out for yourself how Hundreds of engineers and technicians with key many good jobs are waiting for good men to fill positions in the radio industry, broadcasting. FM them. These men must have modern training to and Television owe their sucessful training to handle intricate present day equipment. You can't CREI. We are ready to help you in the same way we have been helping others for over 20 years. say, "I don't need more training." Every radio Even if your radio experience is limited, there man needs more training to increase his technical is a CREI course for you. CREI takes you all the knowledge, no matter how limited or how great his way to a practical engineering level. CREI does experience.

Send for and read our 24 -page booklet that explains our self- improvement program -our courses -and what we can do for you and your future. CREI courses are still available at pre -inflation prices and today give you more MAIL COUPON FOR FREE BOOKLET thorough instruction service per dollar than ever before - on convenient terms. It costs you nothing to read the CAPITOL RADIO ENGINEERING INSTITUTE facts. Please write today. 16th and Park Road, N. W., Dept. RC -9. Washington 10. 0. C. Gentlemen: Please send your free booklet, 'TREE training for your better job in Radio -Electronics," together with full details of your home -study training. I am attaching a brief resume of Capitol Radio my experience, education and present position. Check field of greatest interest: PRACTICAL RADIO- ELECTRONICS PRACTICAL TELEVISION BROADCASTING AERONAUTICAL RADIO ENGINEERING Engineering Institute RECEIVER SERVICING INDUSTRIAL ELECTRONICS NAME An Accredited Technical Institute STREET Dept. RC -9, 16th & Park Rd., N. W., Wash. 10, D. C. CITY ZONE STATE__...___ I AM ENTITLED TO TRAINING UNDER G. I. BILL. Branch Offices: New York (7) 170 Broadway San Frandsto (2) 760 Market St. ti. SEPTEMBER, 1948 5.11 Amateur

Four -Band Converter Has Crystal Control

By HERBERT S. BRIER, W9EGQ

signals beat with the 20 -mc oscillator This does not occur with antennas to produce 7- to 10 -mc difference fre- using half -wave elements - The converter is mounted in a steel cabinet. fed with low quencies at the plate of the mixer tube. impedance feeders (300 ohms or less), The difference frequencies are fed into and the switch does provide a convenient THE big problems in designing high - the receiver, the tuning of which deter- method of switching the converter in frequency receiving equipment are mines which signal will be further am- and out of the circuit; but with long - instability, drift (have you ever plified and detected. wire antennas or high- impedance feed tried to use the crystal filter of Tight antenna coupling broadens the lines, some spurious signals may leak your receiver on 6 or 10 meters ?), and response of L2 sufficiently to cover the through. a high signal -to -noise ratio. The first desired frequency range, and it puts the All coils, except the oscillator cathode two cease to be problems - with crystal greatest possible signal on the grid of coil, are wound on Millen type 74001, controlled equipment. the r.f. amplifier-necessary for the best slug- tuned, shielded, plug -in forms. signal -to -noise The pictures and diagram show the ratio. L4 is loaded by a In construction, 6,200 -ohm resistor and by being closely the parts layout simplicity of this crystal- controlled con- closely follows the electrical sequence. verter. With it, any well -shielded re- coupled to L3. The box used was 4% x 7 x ceiver, capable of 3% inches, covering a frequency The receiver to be used with the con- but a larger box with a hinged top is range equal to the width of the desired verter must be practically dead without recommended. band, becomes a sensitive receiver for an antenna; otherwise unwanted signals that band. All receiver controls are used at the converter output frequency will CRYSTAL TABLE in the normal manner. Even the dial leak through and interfere with the de- Crystal Crystal Signal Receiver calibration can be used if a judicious sired signals. Make the test at night Freq. (Me) Harmonic Frequency (Me) Dial choice of crystals is made. With the con- when the signals are loudest. Disconnect verter oscillator producing a 20 -mc out- the antenna, temporarily shielding the i 4th 21 -21.5 5 -5.5 put, for instance, a 28.5-mc signal will terminals, if necessary. One or two weak 3rd 21 -21.5 6.6.5 beat with it to give an 8.5 -mc input to signals can be tolerated, because the 4th 27 -30 7-10 the receiver; a 29 -mc signal will give 1 noise contributed by the converter will 9-mc 2nd 21 -21.5 7.666 -8.156 input to the receiver; and so o . cover them up; but strong signals will 6.667 - The same relationship can be had to cause annoying interference. 3rd 27 -30 7 -10 other bands. The crystal table lists a few With a "souped -up" BC -348 there was Fund. 21 -21.5 11 -11.5 of the crystal frequencies which may be enough pickup from the antenna ter- 10 2nd 27 -30 7 -10 used. minal for some commercial c. w. signals The extreme stability of the converter to push the S meter well up the scale. Fund. 21 -21.5 6.333-6.833 is 14.667 especially noticeable when receiving Use of crystal microphone connecters 3rd 50-54 6-10 weak DX signals through interference. and a shielded lead between conver- the Fund. 27 -30 7 -10 Below is a schematic diagram of the ter and the receiver eliminated the un- 20 converter. Assuming that 10- and 11- wanted signals when the converter's an- 2nd 50-54 10-14 meter signals are to be received, the tenna switch was not used. However, slug -tuned r.f. and mixer coils L2 and with the switch and with an antenna L4 are resonated to 28.5 mc. Being having considerable pickup at the un- To obtain short leads the coil and heavily loaded, L4 allows approximately desired frequencies, weak signals would tube sockets in the r.f. and mixer stages equal amplification of all signals be- feed through the small capacitances be- are turned so that pin 3 (the grid con- tween 27 and 30 mc. The 27- to 30 -mc tween the switch contacts. nection of each coil socket) is adjacent to pin 1 (control grid) of the tube TAL MI NE CONNECTOR/ TO RCA 6ÁK5 (3) sockets, and in the oscillator so that pin 3 (the plate connection) of the coil socket is adjacent to tube socket pin 5 (plate). Pin 3 is the hot one on all coils, and the numbers on the diagram indicate the pins used for the remaining connections. Winding data for all coils is given in the coil table. All components below the chassis are hung in place wherever convenient, aid-

C 2 TURNS OF INSULATED W RE AROUND GRID LEAD ed by tie lugs. All grounds are made directly to the chassis, and the only e+IS0V /ISMA 6.3V/.525A shielding required, in addition to that The schematic diagram shows how simple the converter is. Three miniature tubes are used. (Continued on page 56) RADIO -CRAFT for 55

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turns are recommended. The more turns used, the more L2 is loaded. Up to a point the signal -to -noise ratio also im- proves. The antenna itself has some bearing on how heavily the input circuit may be loaded. An antenna having considerable pickup at the converter output frequency will cross modulate the GAK5 grid when coupled too tightly, and signals will ride through without regard to the position of the slugs in the coils. When this effect is present, the antenna is overcoupled; and reducing the number of turns in Ll not only eliminates the trouble, but also increases the strength of the desired signals. An improvement in signal -to- tube -hiss ratio may be obtained by adjusting the mixer bias. Temporarily replace the mixer cathode resistor with a 10,000 - ohm potentiometer. Replace the antenna with a resistance of the same value as the feeder impedance to eliminate outside signals. Pick up a weak, locally generated signal, and adjust the mixer bias to the value that gives the greatest signal -to -noise ratio. Before adjustment, the S meter may read S6 with signal and drop to S4 without signal. Increas- R.f. and mixer tubes are covered with shields. Wind all coils except L6 on shielded forms. ing the bias may drop the meter reading to S5 with signal, and at the same time supplied by the coil and tube shields, is cause the voltage is so small. A receiver drop the no- signal reading to obvi- by Sl, the shielded output lead. tuned to 40 mc can be used, tuning ously a tremendous improvement in sig- the slug for maximum signal strength; nal-to- noise ratio. the optimum is After Preliminary adjustment but the easiest method to leave the value is found, the actual resistance in To put the converter in operation, in- 28 -mc coils in the r.f. and mixer stages the circuit is read with an ohmmeter, sert the 28 -mc coils, tubes, and crystal; and, with the receiver dial set to 11.5 and the process repeated for another mc, in 40 -mc connect the converter output to the re- to adjust the slug the band. The optimum value will be differ- ceiver antenna terminal through a oscillator coil for maximum signal. Out- ent on each band, because it depends on shielded line; and apply the proper volt- put of the mixer will still be at the dif- the amount of oscillator voltage being ages. Connect a low -range voltmeter ference frequency between ri. and oscil- injected into the mixer grid. Use the across the oscillator cathode resistor and lator signals, but the oscillator will be lowest resistance, because - within adjust the slug in L4 for minimum read- operating above the r.f. The converter limits- higher resistance merely reduces ing on the meter. The crystal oscillator will work as well on 27 to 30 mc as be- mixer sensitivity slightly without affect- signal should be clearly received when fore, but the receiver dial calibration ing the over -all signal -to -noise ratio. the receiver is tuned to the crystal fre- will be backwards. However, if the resistance is less than quency or a harmonic thereof; removing Once the oscillator is peaked, insert 1,000 ohms on any band, it indicates that the crystal will cause the signal to dis- the remaining 50 -54 -mc coils and adjust insufficient oscillator voltage is being in- appear and will increase the meter read- as outlined for the 28 -mc band. The re- jected into the mixer grid. Wrap an- ing slightly. ceiver dial should be set near 12 mc and other turn of the wire forming capacitor If a signal generator is available, set the signal generator to 52 mc. 50 to 54 C around the mixer grid lead and repeat it to 28.5 me and couple it loosely to the mc will correspond to 10 to 14 mc on the the procedure. converter input. Tune the receiver dial receiver. Coils for the 21 -mc band are When the converter is used with a around 8.5 me until the signal generator similarly adjusted. BC -348 receiver, bands 4 and 5 cover is heard, and adjust the slugs in L2 and Ll, as specified, is approximately cor- only 6 -9.5 and 9.5 -13.5 mc, according L4 for maximum output. If a signal rect for 300 -ohm feeders. For feeders to the dial calibration. Nevertheless, generator is not available, simply set the of different impedance, the number of without turning the band switch, the receiver dial to 8.5 megacycles and ad- turns must be changed for best results. entire 6- and 10 -11 -meter bands can be just the slugs for maximum noise out- Three turns should be correct for 75 covered by turning the dial beyond the put with no antenna connected to the ohms, and 10 turns for 600 ohms, on 28 calibrated portion of the scale for the converter. When the antenna is con- megacycles. On 50 megacycles two to six high -frequency ends of these bands. will a increase in nected, there be great COIL TABLE background noise; and if the band is Turns open, signals can be tuned in by moving the receiver dial between 7.16 and 9.7 Signal Frequency (Mc) 21 -21.5 27 -30 50-54 REMARKS mc. The antenna will detune the input circuit somewhat, and the slug in L2 LI 10 7 4 Over grounded end of L2. should be readjusted with the receiver Closewound. L3 near top of dial set at 8.5 mc. Its setting will be L2, 13, L4 22 15 6 form; L4 separated from L3 by 1 -16 inch. much less critical than before. The same procedure is followed with LS 43 22 11 Closewound the 50-54 -mc coils; however, if it is Crystal Frequency (Mc) necessary to triple or quadruple the 4 5 6.667 10 14.667 20 fundamental crystal frequency to reach 5 -10-mc, closewound.

1 wire it is quite diffi- L6 I 20 18 15 10 7 j4 10-mc, spaced diameter. 40 mc in the oscillator, 14- 20-mc, spaced to )2-inch. cult to tune the oscillator plate circuit to by observing the variation in All coils wound with No. 24 enamelled wive, except LS for 21 -21.5 mc and LI for all bands, which resonance are wound with No. 28. LI to LS are made on Millen 74001 z h -inch- diameter shielded slug - voltage across the cathode resistor be- tuned forms, L6 on s -inch plain forms. RADIO -CRAFT for a I

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u e11 LINE VOLTAGE REG I. ....1 %7 :G1 ey 1111111.5 11111. 701 R.55 25.00 operable 1111 V. ml e). 2.1::1.\ 9311 91113 . Sec 1131 , I 1 2 KIl 1'1 $99.50 2.122 32117 :213:: Inc. K.W 15.00 ro'. roc Vlete with ta. VOLTAGE REG`" '1%.: .'I'cp. "Iu1" 2 Kt., 2.120 2997 :1119 nee. 271 K.\V. 15.00 crystal. cal. than. antenna. Load. Inpu; .. 540.00 2.127 2903 2992 Inc. 1 K.W 15.00 Iel.r & lomerslon kit and VIILTAGI fat 1',. 1, ' 3 1% 15.00 1111 TRANSTAT _ 1 :12 7511 25211 me. K. data f n 1111 T, ly .Blf11llm $29.95 11111 111.. t t $75.00 2.135 1'k:. 1219- -3203 Inc. '.5_ 3 K.W. 25.00 I i ', ITE Circuit Breaker. .wW.. S15.00 2.1311 l 'kg. 17 'tä:13 me 8.7 R.W. 25.00 2.151 l'kc. 9,111 9411% me. 311 K.W. 25.00 A COMPLETE LINE OF MICROWAVE EQUIPMENT IN 400 CYCLE TRANSFORMERS :1.161 21.001 nlr. 33 K.W. 17.50 STOCK: 10CM. 3CM. 1.25CM. SEND FOR MICROWAVE KS 9384: 115 V. 400 e). _':,o nia, 35. I'M: 71 1 A V 15.00 FLYER. Ill 41 110. $12.50 ^UIIV 58101 mc. Imo K.W. 25.00 #121133: Prl: 115 1501 e Sec: -15111 sel. 210 Iva $9.95 KLYSTRONS: 7371.5 II $7.75 711711 S20.00 Plate XfnD: Pri: w 115 v. w a$o.280o Cy. Sec: 22011 v. 3111 HEADSETS volt amps $5.45 MAGNETS Dynamic mike and headset combination. A high qual- Pow 2.121 73% -A. 2.122. 2.120. 2.127. 2.1::1. 2.132. and Kg 9273: Pei: 115 s, 4110 -24011 rw. See: 711'III I. 217 to ity. rmehmt 111111. used In 11 -Ill tank Xmtra. Stile & ::.1::I Karl. $8.00 622 V.A $1.35 plumes emlipleie. newI $2.75 15311 f .i.1, 1,,11 . t - p1lc dlen 8.00 KS 944.%: Pri 11% V. 1110-24011 es. ..el: 592 sel. 1211 1 OIS :ill li KALISE.T \ fu-,uhe¡III'Irlo lita11511 with insert 1 e ',. I5,.- Ville diane 8.00 6.3 v. 8 aolp amis. $3150 :011 l' type phone. Ilia, rut ba.kgln eel nuises IM a minimum. 11:11..' ._iatle 2.... to 3' bet )'late Xfn11 115 v. 4110 c)'. See: 98011 or Lut I limo lam impedance 131111 0111115i assure. emelene)' & high pote Le,. 12.00 32 ma. 1 $12.50 0111.1lß' 85c Plate e XfI: 1f'. r. nun ... : 1156 -1.11311 %laIrbiug 1r:dishUmer lu 11131131 31111 lawns to 611011 None 40 ma. 51.75 TI N \Itl 1. l'KG'l) "('W" MAGNETRONS Ienput 35e OKGI Sirs Plate Motel r . :ts 11 $1.15 273.3200 It 13 Insolset. 51100 Minis ImiXhI tIue, rubhrr .11x111511$. :f1311 3371 \Ors. (1(02 11x01, nnilb + void & 1111111 l'I.. %. New $1.95 POWER CHOKES NEW -$45 each New -S55 each SWINGING ('11111, : ill 1 amp 12 .711473. Sharp band pass peaked UH51M $10.93 BAND PASS FILTER. .11 el,.. ,aid :1 High-to-high unmd:11we. 111n be m: hY, 2 amp .. 51.4, n,, 17 tira .52.45 SPECIALS und int,'Vh ne 1111111111 111 n5riner. it'ulS nut 8.5 hy, 123 ina I.5(1 .ill III. 2.. 3 amp 1,50 ulu o $2.25 C. Includes %:nlon. 411151. New. will) Illnlit diagram 21 by. 05 ma 1.10 .35 by, .:C1 amp 7.5) panel turns Ie i: 3 . hy. 1311 ma 1.50 Dual 2 hp, 1311 m1 1.21 may be switched 1)ní 7 hy. 75 ma. 11 .1 l0'. 12 amp. 46 noms 16.50

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SEPTEMBER 1948 Ji Amateur

Modifying the R- 44 /ARR -5

This set makes a top -notch FM receíuer

By L. W. MAY, JR., W5AJG

After carefully checking the circuits of the ARR -5 and the commercial coun-

terpart, the S -36A, we found that the e-- major circuit differences are in the audio circuit. The S -36A has a push - pull output stage capable of several Front view of the set after conversion. watts undistorted audio output, while the ARR -5 has a single output stage de- THE type R -44 /ARR -5 v.h.f. receiv- livering only 50 milliwatts of audio. A er is one of the better pieces of video output connection for feeding the military radio equipment to appear AN /APA -6 radar indicator was made on the surplus market. It is the in the cathode circuit of the 6V6 a.f. military version of the Hallicrafters' amplifier. The r.f. and i.f. channels are S -36A v.h.f. FM- AM -C.W. receiver used practically identical and with a few in the services as an airborne search changes in both the a.f. and r.f. sections, receiver for locating enemy radar and the ARR -5's performance can be made communication channels between 27 to approach that of the S -36A. and 143 mc. The old and new FM broad- Rear of the R -44 /ARR -5 v.h.f. receiver. cast bands and the 11 -, 10 -, and 6 -meter R.f. circuit alterations amateur bands are included in this The R -44 /ARR -5 was used with the The modifications are not at all diffi- range; therefore this set will prove AN /APA -10 panoramic adapter or AN/ cult and can be made by anyone familiar equally useful as an FM broadcast re- APA -6 radar indicator to provide visual with v.h.f. receiver construction. To ceiver or a v.h.f. receiver for the ama- indications. These units were connected start with, the ARR-5 has an extra r.f. teur bands. to the receiver through co -axial connec- amplifier stage using a 956 tube in a This set can be used as is by adding tors on the front panel. A motor -driven reradiation suppressor stage. This is a suitable power supply and loudspeak- scanning device was provided for con- an untuned r.f. stage (Fig. 1) in a sep- er; however, some changes and modifica- tinually tuning back and forth over any arate shielded box between the antenna tions improve its over -all performance predetermined section of the tuning terminals and the standard r.f. section and adaptability for civilian use. range. (Continued on page 60)

RERADIATION SUPPRESSOR 50 COAX IN

¡CBI iR13 Ì 503 ANT 1 L 956 I RERADIATION STAGE TO MIXER I r--

R77

iB NOT USED iE REMOVE FROM SET

5Î SRí

AGANG CB3 L-GANG A- ANT COMPENSATOR 251110- SEE TEXT

--sSCREEN 6+ -.B+ PLATE SCREEN B+ SCREEN 8+ A F GAIN

AFIN TI ANTI,10 01 6V6 OUTPUT TRANS R60 6V6 TOVC

ANT214) 91 xi 11

I I, T3

ARTA 0 I Q.

B+ fig3 fig4 fig

Fig. I -R.f. circuit of the R -44 /ARR -5 before conversion. Fig. 2 -The r.f. circuit of the receiver after conversion. The reradiation stage is removed bodily from the chassis. Fig. 3 -An optional connection permitting separate attenas for each tuning range. Fig. 4 -Note the circuit of the combination audio -video output stage before conversion. Fig. 5 -The output stage after conversion is completed. RADIO -CRAFT for 59

Machines in RCA's Lancaster Tube Plant are designed for mass production of Kinescopes- television picture tubes -at lowest possible cost.

Behind the magic of a Television Tube

Every morning, 14 tons of glass coated with fluorescent material - Every phase of manufacture con- "bulbs" go down to the produc- forming a screen on which an elec- forms to scientific specifications estab- tion lines at the RCA Tube Plant tron gun "paints" moving images. lished by RCA Laboratories. Result: Television tubes of highest perfection in Lancaster, Pa. Each step is so delicately handled -assuring sharp, clear pictures on the By evening, the bulbs are television that, although RCA craftsmen are screens of RCA Victor home television picture tubes, their luminescent faces working with fragile glass, breakage receivers. ready to glow -in television homes is less than 1 %. news, sports, enter- When in Radio City, New York, be everywhere -with Water, twice -distilled, floats the tainment, education, politics. sure to see the radio, television and fluorescent material into place on electronic wonders at RCA Exhibition Born of glass, metals, chemicals, the face of the tube, where it clings Hall, 36 West 49th Street. Free admis- the picture tube comes to life by molecular attraction -as a uni- sion. Radio Corporation of America, through flame and heat. Its face is form and perfect coating. RCABuild ing, Radio City, NewYork 20.

illit RADIO CORPORATION of AMERICA

SEPTEMBER, 1948 IiÍI L 1ilO>IIfCYP,

Fig. 4). The circuit was altered as in Fig. 5. The output transformer should The reradiafion stage be of fair quality for best FM reception, was originally located on the rear of the sub - and may be mounted in place of the chassis supporting the filter choke L3 which isn't needed since r.f. and oscillator as- sufficient filter may be included in the semblies. The original power supply. All necessary changes antenna coils were re- are shown on the before-and -after audio - placed with coils wound section schematic and all are of minor from thin copper strips. importance. Only one component is add- This change resulted in ed, a cathode bypass condenser for the an overall gain increase output tube. of 6 to 10 db. The antenna primaries were No power supply is included. Any wound with rather normally well filtered supply providing heavy bus bar covered 250 to 275 volts d.c. at about 100 ma and with suitable insulating 6.3 v a.c. at approximately 2 amperes material. may be used. The scanning motor requires 24 volts d.c. at less than 1/2 ampere, if this feature is utilized. The of the receiver. Its purpose is to sup- separate inputs could be provided on the power input receptacle is replaced by a press any radiation from the receiver it- terminal plate on the side of the r.f. 5 -prong socket. self, thereby preventing the enemy from compartment and switch section S1A employing direction -finding techniques neglected altogether. This connection is Optional modifications to spot its location. Its efficiency in shown in Fig. 3. After the set had been section, working for a suppressing any signal leaking out of With these changes in the r.f. few days, we decided that there was a the receiver is remarkable. Unfortunate- and after routine alignment of the trim- chance that we were losing some signal ly, it also does a fair job of suppressing mers C74, C75, and C76, performance is in the r.f. coils, which were sup- wound on any incoming signal as well, making the better than with the reradiation bakelite forms. Consequently, T1, T2, ARR -5 receiver relatively insensitive pressor stage in the circuit. Signals and T3 were all removed, the recently and leaving much to be desired in the should average about 20 to 30 db strong- wound antenna primaries being included way of a good v.h.f. job. This situation er. This is quite an improvement, and and carefully laid aside so that they is easily corrected by eliminating the some users may find the increase in gain could be reinstalled should the coming reradiation suppressor stage and rerout- sufficient for their needs. However, this experiment prove disastrous. ing the antenna input directly into the arrangement did not satisfy us for long First, first 956 r.f. amplifier stage (Fig. 2). and additional changes were made. a length of common copper 400 end it was noted strip about 1/32 -inch thick and s4 -inch Balanced -ohm antenna feeder In tracking the front wide systems are employed exclusively on the that the receiver's wide frequency range was connected from the ground v.h.f.'s at W5AJG /W5JKM. Since the makes it practically impossible to get point of the rotor on the main tuning to the ground side of ARR -5 is set up a co -axial of one antenna to look entirely resistive the r.f. grid coils. for input Another piece 50 ohms impedance, changes were made over the whole range. An antenna com- of this material was in the mechanical construction of the set pensator was added across CIA to peak used for winding the coils themselves, to accommodate balanced inputs. the received signal. This is a small 25- in a spiral fashion, making a very rigid air -supporting structure. The new low - Referring to Figs. 1 and 2, the before - µµf variable condenser conveniently impedance antenna coils were then and -after circuits of the r.f. section, and mounted on the underside of the chassis, wound to the photographs taken after modifica- in the present location of the a.f. gain from rather heavy bus wire. On tion, it is seen that the suppressor stage control. Remove this control and push the first try, nothing would resonate - been the wiring intact. In- it seems that when using this flat copper has removed bodily and an opening it aside, leaving ribbon provided in the side of the r.f. stall the antenna compensator and drill or strip material for coils, ap- first stage proximately twice compartment for the new balanced leads a % -inch hole through the chassis. This as many turns are re- to The of will come out directly under the first quired as when using ordinary wire emerge. primaries transform- coils. ers Ti, T2, and T3 were used for the section of the main tuning condenser. plate -coupling windings of the suppres- Use a piece of strap copper about 1/32 After increasing the number of turns sor tube, so they have a relatively high inch thick and s/4 inch wide to connect on the copper- ribbon coils, the r.f. stage impedance. We use 400 -ohm lines, so the two stators together, and another performed beautifully. By tuning in a these windings are removed entirely and piece to ground securely the bracket known station and watching the S- lower -impedance links of a few turns which carries the antenna compensator. meter, it appeared that a worth -while substituted to serve as the antenna pick- The a.f. gain control may be mounted improvement resulted. up coils. It is possible, by reducing the on a small piece of bracket material With these changes the ARR -5 be- number of turns to fit the particular soldered to the chassis or screwed to comes a very desirable piece of v.h.f. antenna in use, even to use the windings anything convenient and controlled from receiving gear, versatile and very us- without removing them. After doing the front panel by an extension shaft. able. It is suspected that lots of v.h.f. this, the coupling is still rather loose. The co -axial antenna input receptacle men grabbed this set for the same pur- This may result in insufficient antenna was removed, and the audio volume con- pose for which the writer uses it pri- pickup and transfer. At this particular trol shaft extends out through this open- marily - that is, checking the muf installation, the coupling proved to be ing. (maximum. usable frequency) between insufficient with the original cut -down The panoramic adapter outlet was left 30 and 50 mc. Intelligently used in this primaries. Hence the new windings and connected as it is convenient for work- manner, it will save many fruitless closer coupling. ing out of the r.f. section into a regular hours of listening to dead 50 -mc air. Coupling capacitor C83 is also re- communications receiver set at 5.25 mc. One v.h.f. enthusiast contacted, who moved, and the antenna is connected in This affords greater selectivity than the used an ARR -5 for this purpose, avowed on the arm of SiA. If a 50 -ohm co -axial ARR -5 is capable of providing because he would set up the sector automatic input is employed, the original front FM i.f. transformers are used. Be sure tuning and insert a relay in the a.v.c. panel receptacle labelled ANT can be to use a blocking condenser, as the mixer system, so when a signal was scanned used and one side of the antenna coils plate voltage appears on the outlet. by the automatic mechanism, the set returned to ground. If separate an- would stop on the signal and ring a tennas are used, say one for 10 meters, A.f. circuit alterations warning bell, indicating that 50 mc was one for 6 meters and one for the new The 6V6 video output stage has an in business. Could be- anyway, it's food 88 -108 mc FM broadcast band, three audio output of only 50 milliwatts (see for thought. RADIO -CRAFT for li 1

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1B24 ....6 4.95 9MP7 14.9; 806 17.50 C58 12.95 106 1.06 6AQ76T ,. .8N NISI. .. .88 14H7 .8, I B25A .. 4.96 10BP4 34.95 807 1.25 C6A 9.95 IC7G 1.06 6A135 .66 6271: 1.28 14J7 1.01. I B26 .... 15.95 I0CP4A , 42.20 808 2.95 C6J 12.95 1C8 .88 6AT6 .54 6Z1-51. .72 14N7 1.06 1B27 .... 4.95 10FP4 54.50 809 2.50 CEQ72 1.95 IDSG 1.28 6AU6 .72 7A4 /XXL .72 14Q7 As 1B29 .... 4.95 1011P4 ., 49.50 810 7.95 CK1005 .39 1D5GP ., 1.28 6A V6 .54 7A5 .72 14R7 ,88 1B32 .... 4.95 TOY .69 811 2.25 CK1006 .69 1D7G 1.06 6ß4G 1.06 7A6 .72 1457 1.06 1.06 1B56 .... 8.00 10 spec , .69 812 2.9F EF50 .79 IDSGT . 1.28 6B5 1.56 7A7 .72 14W7 IN21 .59 12DPT 14.95 812H 6.90 EL3C 4.95 IE5GT 1.56 6B6G .72 7A8 .72 14X7 1.06 IN23 ... .59 12GP7 14.95 813 7.9:. EL225 1.95 IE7GT 1.56 6B7 1.06 7AD7 1.06 14X4 .88 1P22 ... 11.50 123 P4 60.00 814 1.9.. F123A 12.95 1F4 .88 6B8 1.06 7AF7 .72 19 1.06 1P24 ... 2.00 15AP4 125.00 815 2,50 F'127A 22.50 1F5G .88 6138G 1.06 7AG7 .88 19T8 1.06 IS21 .... 1.95 15E 1.50 816 1.19 F660 150.00 1F6 1.28 6ßA6 .66 7AH7 .88 20 1,56 2AP1 .. 2.95 15R 1.50 822 11.95 FG81A ., 6.95 IF7G 1.28 6ßE6 .66 7B4 .72 22 1.26 2B22 ... 5.35 20AP4 270.00 826 .79 FG105 19.95 II:IGT .88 61366G 1.92 7135 .72 24A .72 2C21 ... .98 23D4 .49 827R 99.50 FG172A 32.50 IG6GT .88 6BH6 .93 766 .72 25A6 1.116 2C22 ... .39 45 spec .49 828 6.95 FG238B 160.00 IH4G .72 6ßJ6 .72 7B7 .72 25AC.6 1.06 2C26A .. .75 75TL 3.95 829/A/B 7.95 6L146 11.00 11156T .60 6C4 .60 7B8 .72 25AC5GT 1.06 2C34 .. .59 100TH 12.95 829B/3E29 4.95 (.L605 250.00 IH6C 1.06 6C5 .60 7C1/I203A 1.06 25C6G 1.06 2C40 .... 1.98 100TS 3.00 830B 5.25 í:L697 150.00 IH6GT 1.06 6C5GT .60 7C5 .72 25L6 1.06 2C43 .... 7.50 102F 4.00 832/A 3.95 HFI00 3.95 IJ6GT 1.06 6C6 .72 7C6 .72 25L6GT .60 2C44 .... 1.75 114A .69 833A 39.50 HF200 17.95 1L4 .72 6C8G ... 1.06 7C7 .72 2SY5 1.06 2C46 .... 7.50 I14B 1.25 836 1.15 HY2J 1.50 ILA4 1.06 6D6 .60 7E5 /1201 1.06 25Z5 .54 21)21 .... 1.69 120 5.95 837 2.50 HV312 5.50 ILA6 1.06 6D86 1.06 7E6 .72 25Z6 72 21329 .... 1.39 121A . . 2.65 838 3.95 HY69 .,, 2.49 1Lß4 1.06 6E5 .72 7E7 .88 25Z6GT .54 2E22 .... 1.50 20313 10.95 641 .69 HY75 ,. 1.2.5 ILCS 1.06 6F5 .60 7F7 .88 26 .60 2E24 .... 4.37 203R .., 5.95 843 .69 HY1148 . 1.25 ILC6 1.06 6F5GT .., .60 7F8 1.06 27 .54 2E25 .... 3.95 204A 49.95 845 4.95 HY115 1.25 ILDS 1.06 6F6 .72 767/1232 1.06 28D7 .98 2E26 .... 1.29 205B 4.50 845W 5.95 HY615 1.25 ILE3 1.06 6F6G .60 7%7 .80 30 .72 2E30 .... 2.25 211 .98 851 98.00 HYEI148 .48 11.65 1.06 6F6GT . , , .60 7.17 1.06 31 .88 2321A .. 14.95 215A 3.00 852 14.95 HY I 231 5.50 ILH4 1.06 6F7 1.06 71E7 1.06 32 1.06 2.122 .... 24.95 217C 7.51) 860 3.00 HY1269 . 5.50 ILN5 1.06 6F86 1.06 7L7 .88 32L7GT .., 1.2, 2]26 .... 14.95 221A .. 2.95 861 49.95 KCI 105.00 INSGT ., .72 6G6G .88 7N7 .88 33 1.06 2J31 .... 24.95 222A 120.00 864 .69 KU676 22.00 IPSGT ., .88 6116 .60 7Q7 .72 34 1.06 2332 .... 24.95 227A ,., 3.95 865 .98 ML100 105.00 IQ5GT .88 6H6GT .60 7R7 .88 35/51 .72 2J34 .... 24.95 2416 90.00 866A .89 ML101 150.00 1R4 .88 6.15 .51 7S7 1.06 35A5 .72 2338 ... 37.50 242C .., 5.95 868 1.95 ML502 300.00 IR5 .72 63567 .51 7V7 1.06 35B5 .72 2.139 ... 34.95 249C 3.49 869B 75.00 MR4 90.00 1S4 .$8 6J6 1.06 7W7 1.06 35L6GT .60 2J40 .... 34.95 250R 7.95 872A .., 2.50 QK59 45.00 185 .66 637 .72 7X7 /XXFM 1.06 35W4 .46 2J42 .... 34.96 250TH 19.50 874 2.49 ßK60 ,, 45.00 1T4 .72 6376 72 7y4 .72 35Y4 .72 2J49 .... 34.95 250TL 19.50 676 .98 QK6I . 55.00 ITSGT .88 6J7GT .72 77.1 .72 35Z3 .72 2351 ... 31.95 252A 4.95 878 2.49 QK62 55.00 1114 .72 638(: 1.06 is 1.56 35Z4GT .50 2.11351 .. 4.95 259A 4.95 879 .69 REL21 4.25 1115 .66 6K5GT .138 12A6 .89 35ZSGT .46 2J53 .... 25.00 274A 1.25 884 .98 RKI2 1.95 IV .î2 6K6GT .54 I2A6GT 1.06 35266 .88 .88 6K7 .60 12A7 2J54 .... 25.00 274B 1.25 889 .98 11X21 . , 3.95 1 V5 1.06 36 .86 2K25 ... 24.95 301A 4.95 891 110.00 6X22 4.95 1WS .88 6117G .60 12AMGT , .72 37 .60 2K28 ... 24.95 304TH ., 7.95 89211 200.00 RK25 2.95 2A3 1.06 6K7GT ., .60 12AR7GT .88 38 2 3API ... 2.95 304TL ., 1.98 902P1 7.95 14X33 .98 2A4G 1.28 6K8 .88 12AL5 .72 39/44 .59 3B22 .... 4.95 305A 12.95 905 11.95 ßK34 .. , .59 2A5 ... , .72 6Kß6 1.06 12AT6 , .54 41 .60 .88 , .88 42 3823 .... 4.95 307A 6.25 920 2.91 111(59 , , . 3.95 2A6 6KSGT 12ÁT7 . , 1.06 .60 3824 .... 1.95 310 4.95 923 .98 ßK60 .,. .79 2A7 2.20 6LSG 88 12Aí16 ,.,. .72 43 .60 3B25 .... .98 311A 1.98 931A 4.95 RK65 24.95 2R7 .88 6L6 1.28 í2A1'7 ,,,, .R8 45 .60 3B26 ... 5.95 316A .89 950 1.06 RK69 ,, 49.50 2E5 .88 6L6G 1.06 12AW6 .96 45ZSGT . - .60 3BPI ... 2.95 322A 120.00 9538 4.95 RK72 1.9S 2V3G 1.10 6L6GA 1.06 12BA6 .66 46 As . .69 , , 3C21 .... 5.95 327A 4.95 954 .75 RK73 , , 3.95 2X2A 6L7 12BE6 . , .66 47 .88 3C22 .... 2.95 331A 4.95 955 .75 ßK75 .., 6.25 3A4 .72 61.76 1.06 12C8 .89 I! .88 3C23 .... 4.95 350 /A /B 2.95 956 .75 RXI20 ,. 10.00 3115 1.29 6N6G 1.28 I2FGT .60 50 1.56 3021 .... .69 3S3Á 4.95 957 .75 T20 ..,. 1.95 3A8GT 192 6N7 .88 12H6 .60 50A5 .88 88 3C30 .... . 1.50 368AS 9.95 958A .75 TZIO 2.95 368 1.06 6Nî67 12]50.7 .51 50B5- .72 3CP1 ... 3.00 3î1A 2.95 959 .TS 1'X6653 1.95 306 /XRB 1.28 6P5GT .88 12370 72 50066 1.06 6.95 .89 6Q6G 1.06 3ßP1 ... 3.lS 371B 2.95 991 .69 V700 , 31)6 /6T7G 12]7GT .72 501667 .60 3EPI ... 3.15 388A 7.95 1000 spec. 24.95 VR75 .75 3E6 1.06 6Q7 .T2 12K7G . .70 50X6 .60 3D21A .. 3.00 7.95 1611 75.00 VR90 .75 3íF4 1.06 6Q76 120(8 .60 50Y6GT .60 4.95 394A 60 3E29 ..., 39411 4.50 1611 .99 \'690 .75 3Q4 .T2 6Qî67 60 12Kß .813 53 As 3GPI ... 4.95 4í7A 23.95 1614 . . .75 VR92 1.49 3QSGT .88 6R7 .88 12K667 .88 55 .72 4 -65A ... 14.50 434Á 3.95 1614 1.75 Vß92 .75 3S4 .72 6ß76T .88 I2Q76T .60 56 ...., .60 .AA 4-125A .. 27.50 446Á 1.95 1616 1.39 Vß105 .TS 3V4 .72 6S7 12SÁ7 , .60 57 .72 4 -250A .. 37.50 450TH 24.95 1619 .75 VR150 .98 5AZ4 .42 6876 .88 I2SA7GT .60 58 .72 4A1 .... 1.98 503 195.00 1621 .., 1.98 VTI2IA 3.00 5R4GY 1.03 6S8GT .96 I2SC7 .72 59 1.06 IAPIO .. 6.95 527 12.95 1622 1.75 V11111 1.19 574 1.28 6SA7 .60 12SF5 .60 707.7GT 1.42 4621 ... 4.95 531 49.50 1624 1.75 \1'1.460 14.95 5174G .53 65Á76T .60 12SFST .60 7IA .72 .RR 4035 ... 19.95 575A 14.95 1625 .19 R'i.46A 14.95 WIG .1113 65ß7Y 12$F7 .72 75 .60 1E27 ... 8.15 632A 9,95 1626 .49 R'L532A 4.95 5W1 .138 6SC7 .72 I2SF7GT .88 76 .6o .9R 4J2ß .. 34.95 701A 4.95 1627 7.95 WI.562 , 150.00 5W4GT .60 6SD7GT 12567 .72 77 .60 .60 6SF5 4J29 .. 34.95 702A 3.95 1629 .69 N'1.616 . 105.00 5X4G .60 I2ÇH7 .72 78 .60 4.95 50 6ß56T .72 AN 5AP1 ... 703A 4.95 1630 . 7.50 W1.619 49.50 517.G 125J7 .60 79 í AP4 ... 5.95 704A 1,98 1636 5.95 Z225 1.95 5Y3GT .... 38 6SF7 .72 12SJ7C.T .60 80 .42 1.69 .50 6SG7 .72 81 1.28 .5ßP1 ... 1.95 705A 2.95 1638 .98 0A2 SY4G 12SK7 .. , , .60 5BP4 ... 4.95 706ßY 24.95 1641 .79 OA3 /VR75 .98 5Z3 .60 68117 .72 I2SK7GT 82 .88 5CP1 3.95 9ß OA4G 1.06 571 A13 65]7 60 ,88 83 .RA ... 706CY , 21.15 1642 . .. 12SL76T SCP7 .,. 13.95 707A /B 24.9: 1654 1.98 OB2 2.05 6A3 1.06 6ß37G7 125N767 AO 83V 1.06 1D21 29.95 .75 .88 6ßK7 .60 84/6Z4 ... 708A 7,95 166S .98 OB3 /VR90 6A6 12907 , .54 .60 .60 :íFP7 ... 3.95 7O9Á 9.95 1851 1.25 0C3/VR105 .75 6A7 .72 6SK7GT 12SO7GT . .54 85 .72 5GPI ... 9.95 713A .. 1.65 0152 1.06 OD3 /VR150 .75 6AR .72 6SL7GT .813 12Sß7 .72 89 .72 53P1 ... 11.95 714AY 14.95 1853 ..., 1.06 00 .50 6A8G .72 6SN7GT .80 125ß76T .72 99V 1.28 5329 ... 29.50 715A/B 19.95 1963 .95 0Y4 .88 6Áß6T .72 65Qî 54 12X3 .98 91X 1.28 5.130 ... 29.50 715C 29.58 9050 .98 OZI .88 6Aß5 /6NS. .RR 6SQ7GT .54 1223 .88 II7L7GT 1.42 51.P1 ... 11.95 OZ4G .88 69R7 .60 1.06 117M7GT 1.42 717A . 1.65 0051 ..... 98 6Aß7/1953. 1.06 14A4 5TP4 ... 20.00 7200Y 34.95 0140 20.00 OlA. .50 6ACSGT 1.06 6SR7GT .60 IIAS 1.56 117N7GT 1.42 6AF6G . .Aß 1A3 .... .72 6S87 .66 17Z3 .51 721A /B 4.35 _511 4.95 9ÁC7 /Iß52 1.06 14Á7/12B7 .913 6C21 .... 24.95 IA4 1.28 6. T7 ,88 723ÁB 5.95 5516 5.95 6AD7G 1.06 65V7 /XXD fiD4 .... 1.95 4.95 IA4P 1.28 11TZ6GT , 1.06 í24A /B 55562 10.00 IASGT .8A 6AG5 .96 61'5 6C5 14667 AN 24.95 .88 1112667 6Q56, .., 1.25 725A 7193 .39 IÁ6 1.06 6ÁC77 1.06 615667 .72 1167 FM-1000 1.213 23.50 88 7ßP7 ... 4.95 726A 6005 4.95 IA7GT .72 6AÁ6 1.42 6U7í. .60 1469 1273 .89 7EP4 ... 17.95 800 2.25 8011 2.95 1Aß5 - 1.06 6ÁJ5 .99 6V6 106 14C5 .88 9002 .69 î6P4 ... 19.40 80111 98 8012 4.95 IB3GT 1.56 6AK5 .99 6V6GT 72 14Cî 813 9002 .89 9GP7 ... 15.00 802 2.95 8013 2.95 1B4 1.28 6AK6 .88 6W7G .88 14E6 .72 9003 .49 9JPI ... 3.95 803 8.95 8016 1.89 IBS /258 1.06 6ALS .72 6X4 .54 14E7 .88 9004 .49 9J P2 ... 3.95 604 9.95 8020 3.95 IB7GT 1.06 6AL7GT 1.06 6X5 .88 11F7 .813 9005 .98 9LP7 ... 4.95 N05 4.95 8025 ... , 7.95 ICSGT .72 6AQ6 .... .66 6X5GT . , , .54 64F8 1.06 9006 .49 Prices Subject to Change Without Notice All Types in Stock Now Subject to Prior Sale DEPOSIT 20°x; ALL PRICES WITH ORDERS NIAGARA RADIO SUPPLY CORP. F.O.B., N. Y. UNLESS RATED C. 160 GREENWICH STREET DEPT. C NEW YORK 6, N. Y.

SEPTEMBER, 1948 Amateur Relay -Controlled Ham Rig

The c.w. key controls the whole station By RICHARD H. DORF, W2QMI

THE control system of this 60 -watt ciency and reduces the power output. the 6V6. This cuts off the 6V6 and re- c.w. transmitter was designed after The oscillator cathode is keyed so that stores the 807 screen voltage to its nor- the writer saw a number of ham the transmitter can be used for break -in mal value. stations where changing over from work, if desired. The OD3 /VR150 volt- A Collins pi- network is used in the receive to transmit involved throwing age regulator keeps the oscillator plate output. Two coils, one for each band, are three or four switches, unplugging a and screen voltages almost constant, so switched in and out. Any single -wire an- pair of phones and going through a there is no perceptible chirp. The click tenna can be used. The pi will load any- moderate acrobatic routine. filter (RFC1, RFC2, Cl, C2, and RI) is thing from a lead pencil to a steel tower. Pressing the key puts the station on so effective that no clicks can be heard The commercial coils used have end the air, switches the antenna to the even when the receiver is placed right links, so a balanced feeder can be used transmitter, and silences the receiver. next to the transmitter. in place of the single wire. Usually, a When keying is finished the receiver The oscillator is capacitively coupled separate antenna -tuning network will be automatically comes on again, the an- to the 807. Try different values for C3 required for that. tenna swings over to it, and the trans- if the 807 grid current is less than 3.5 The power supply shown uses a com- mitter goes off. A self-contained audio ma with the key down. bination -type power transformer, keying monitor operates a small loud- Grid -leak bias is used on the 807 to though separate plate and filament speaker on the transmitter panel. This avoid the loss of plate voltage that transformers can be substituted. The control system was designed for this rig would be caused by a cathode resistor. condenser -input filter gives poor regula- but can be readily applied to any size A 6V6 is connected between screen and tion but a high output voltage, 600 volts c.w. transmitter. ground to prevent the 807 from burning in this case. Since the OD3 /VR150 takes The rig is a standard oscillator -am- up when there is no signal (key up) and care of the oscillator, the poor regula- plifier combination. As the schematic, no bias. When the key is up there is no tion in the final does not matter. Fig. 1 shows, a 6V6 Pierce oscillator bias on the 6V6 and it draws maximum drives an 807 power amplifier. Depend- plate current. This large current, pass- The control system ing on the power -supply voltage, outputs ing through the 807 screen resistor, R2, Three single -pole keying relays are up to 50 watts are possible. causes a large voltage drop across it. used because a 3 -pole keying relay Five crystal sockets and a selector The voltage on the screen is, therefore, seems to be hard to find. Any -acting low - switch are provided for quick frequency very small. This prevents 807 fast plate cur- voltage relays are usable; the ones here change. 80. and 40 -meter crystals can be rent from rising to more than about 40 are 5,000 -ohm, 4 -ma sensitive used for the 80- and 40 -meter bands or ma. units. They operate nicely on about 20 volts. 80 -meter crystals can be used for 40 When oscillator is keyed - the the grid The first relay, RY1, keys the oscilla- meters by using the final stage as a leak bias on the 807 is applied through tor cathode. RY2 keys the voice coil of doubler. This, however, impairs effi- the 100K isolating resistor to the grid of the audio monitor oscillator speaker. RY3 operates the control circuits which ANT 7SW COILS take care of antenna changeover and 6V6 -G OD3 VR 150 807 RCVR ANT receiver disabling. 3 r HI t441 eoM .002 .00025 The control circuit uses one half of XTALS 52 5 5 0-200MA 7VAC the 6N7. R4 and C6 are a series RC .-{ 0 -o-# 40Mtit RYSIIC time-constant circuit. When the key is Ho{-. up and the contacts of RY3 are open,

A 1151.31P-Ti, 22.5 volts HUH 47N 50pµf 0005 from the battery are applied -orr to the grid through R4 HUH' i I and C6. There is TUNE} ANT RDa no drop across R4 because there is no -{al-- C4$0002,1,, (5 current flowing through it -C6 acts as a blocking capacitor. With 22.5 volts on the grid, no plate current flows and RY4 117V AC is open. PILOT IOH/200MA EB When the key is pressed the contacts 1 of RY3 close and short the grid to 6.30 FILS 25K .. ground. This reduces the bias to zero, 5R4 -GY I! I R6 plate current flows and RY4 closes. This /25W energizes RY5, which switches the an- 600V tenna over to the transmitter and opens the receiver disabling circuit. When the key is opened after making 5V Cl/.5 each dot and dash the short across C6 is removed. However, the capacitor takes time to charge up and the full 22.5 volts HI VOLT o FRONT PANE do not appear between grid and ground

II7VAC RY6 NOTE , f . until it does charge. If the key is pressed II E -R2 KEY RY3 again, for the next character, before the 2A 400 - IBN - KE F1 500 3916 grid voltage has time to reach a value' - REAR ANON -.® 51 600 - 4716 that would cause RY4 to open, RY4 V 700 - 82K stays shut and the station stays on the 17 VAC SWITCHES - SI - DPST HEAVY OUTY: $2- PST; 53- 0501 RFC 1 i2.2.5M11 R0 -RCVR DISABLE air. If, however, keying is finished, and Fig. l -Six relays are used in the transmitter. The antenna may be a random length of wire. the key is not pressed again the grid RADIO -CRAFT for Amateur lisi voltage will reach cutoff and RY4 will open, turning on the receiver and switching the antenna. The time taken for C6 to charge depends on the values of C6 and of R4 and the battery voltage. The time in which the capacitor will charge to about 67 percent of the battery voltage is equal to C in microfarads times R in megohms. With the 10-megohm resistor and 1 -id capacitor, the maximum time is about 10 seconds. However, the 10- megohm resistor is variable, so the operator can set time according to his own average keying speed. If he is a speed demon, the time can be short; if he is an average or slow -speed operator the time and the resistor setting will have to be larger so RY4 will not open between characters. The other half of the 6N7 is an audio oscillator. The transformer may be any push -pull output unit. The grid leak, R5, and C7 may be changed to give a different tone. If necessary, a small capacitor can be shunted across the transformer primary. A 3 -inch speaker was used since compactness, not fidelity, was the important point. The audio oscillator is keyed by RY2 and gives a good indication of the operator's keying, though transmitter output signal should be checked occasionally for roughness. Fig. 2-The power supply is shown at the lower right in the picture. Coils are at center. Construction A 13 x 17 x 3 -inch chassis was big enough for all the components, but not too big, so don't try to economize on a chassis. Fig. 2 shows how the parts are mounted. The oscillator tube is at the upper right in the photo with the 807 next to it. The 6V6 screen -control tube and the OD3 /VR150 are below these two. A standard 807 shield is included to minimize spurious oscillation. The battery is fastened to the chassis with a yoke of stiff bus bar. The small black pointer knob controls the resistance of R4. The two coils are mounted at right angles to each other so the field of one will not cut the turns of the other. Underneath the chassis (Fig. 3) the coil switch is fastened down with an angle bracket and an extension shaft is used to avoid long leads. The audio transformer is on the right. At bottom is RY6, which is controlled by a panel switch and breaks the center tap of the high -voltage transformer winding for long standby periods. Fig. 4 shows the front panel with the transmitter mounted in a metal cabinet. Fig. 3 -The high -voltage relay is under the chassis. There is little crowding of parts. Height of the panel is 8% inches and width is 19 inches. In addition to the key Transmitter adjustment C4 for a plate-current dip. Now, rotat- jack on the front panel there is one on Place the tap on the bleeder (R6) at ing C5 will load the antenna. Advance the rear apron so that a key can be it in small steps, retuning C4 each time plugged into either place. the ground end, remove the 6N7, and adjust R7 for maximum resistance. for a dip, until 807 current is 100 ma. Now turn on the HIGH- VOLTAGE switch. Replace the 6N7 and advance the tap See that the 807 plate current does not on R6 until RY4 closes when the key is go above about 40 ma. pressed. Remove the paper clip from Insert a milliammeter between the RY5. Now pressing the key should put cathode (pin 2) of the OD3 /VR150 and the transmitter on the air and operate ground and adjust the tap on R7 for all the control circuits: Adjust R4 until 25 -ma. Replace the cathode connection. the time delay is satisfactory. Connect an antenna to the transmitter If the monitoring tone in the loud- and clamp RY5 shut with a paper clip. speaker is too loud, a series resistor can Turn on the high voltage, press the key, be inserted in series with the transform- Fig. 4 -The front -panel layout is symmetrical. and, with C5 at maximum capacity, tune er secondary and the voice coil. SEPTEMBER, 1948 64- People HARRY DIAMOND DIES Harry Diamond, Chief of the Elec- tronics Division of the National Bureau of Standards, died suddenly June 21. One of the inventors of the radio proximity fuze (No. 2 secret weapon of World War II). Mr. Diamond was widely honored for his work. Among the acknowledgments he had received were E.M.C. MODEL 300 the 1940 Award Vacuum Tube Volt -Ohm Capacity Meter for Engineering DC VOLTS -6 ranges to 1000 volts. Achievement of the AC VOLTS -5 ranges to 1000 volts. Washington Acad- RESISTANCE -6 ranges to 1000 meg- emy of Sciences; ohms. the Naval Ord- CAPACITY -4 ranges (.000025 mfd to nance Development 20 mfd) Award for Excep- HAS ZERO CENTER POSITION tional Service,1945, Model 300, as illustrated and the War De- with leads $39.50 partment Certifi- (other models also available) cate for Outstand- See the Model 300 at your Jobber ing Service. WRITE TODAY to Dept. B -9, for NEW. FREE CATALOG Mr. Diamond played a large part in the development of the Instrument Landing and ELECTRONIC ,[JlLJ MEASUREMENTS System (ILS) participated in the first completely blind flight and landing of an aircraft, which took place C O R P O R A T I O N in March 1933. Another development of world im- 423 Broome St., New York 13, N. Y. portance in which he had a major role is the radiosonde. His other contribu- HEARING AID AMPLIFIER ASSEMBLY. tions to the radio art include visual Vacuum tube type. Make a REAL VEST beacons for air -craft guidance, antenna SEPTEMBER POCKET RADIO or AMPLIFIER adding rP l. only small tuner sect. and speaker o, systems, range- beacon course -alignment phone. Ready-wired tern, - nenta Include: 2 controls li & 4 meg procedures, a simultaneous phone and output trans.. Oble. choke. switch, r PECIALS sisters. condensers. etc. Compiete wilt. beacon -range system, aircraft -engine LEo oNE UNIT SCHEMATIC. Less tubes a.i ignition shielding, automatic weather 2'x5 1. des,,. Weigt,s .1 FREE:: New "HEARING AID AND MINIATURE PARTS" rase. s' Supplement only 3t a. stations, upper-air wind velocity deter- ALNICO MAGNETS mination by radio, a method for meas- OE D.P.O. T. RC- -N E N' EXPKRI. -finder polarization er- LAYS - 3 16- s i l- TUBES! TUBES! TUBES! MENTAI. KIT of 10 uring direction ca tacts, pro- SUY NOW -SAVE UP TO BOO g with .std. Bar, " . and bombs. teredtective plastic bous. 90 DAY GUARANTEE!! Circular, Block, etc. rors, director for electronic ng. 16.251. Dc. Most types In stock: unhealed cartons. Kit of 10....1.90 100 ohm o 11. 427, 35. 30, 37. 39. 177. 54. 81. 50. WRITE TODAY FOR 'IRANI, NEU' c 5W4. 523, OHO. 8K7. OL7. or 0X5 39e LATEST ILLUS. ONLY .39 1141. 75. 70, 78. 5U4. 513. 514. 1A7. 'CRATED "ALNICO MAGNET" PHILCO'S NEW VICE- PRESIDENT 11.N5. 0A4. 0A7. 6B7. 6C5. 11E5. 6G S. .SUPPLEMENT. 15 for 5.00 BJS. 6E6. 81.6. BSA7. 65.07. 05117. 05K7. Radcliffe L. Romeyn has been appoint- Vi PILOT JEWEL ASSEMBLY OR7. 7A7. 7B8. 714. 125K7 or 5085 49c B LANK CHASSIS for small re- with faceted Red. .tot 'rt'BE: CARTONS -Plain White ceiverIver r amplifier. O:ta'x4-x ed Vice -President and Factory Export her r Clear Jewel. tMiin Miniature tI' 1.021$'). Per 100... .90 11/2'. Rua tpnx,ftd steel .29 base .19 CT lt/' 1.x344'1. Per 100 1.2E Manager of the International Division 6 for 1.00 medium II'.1" sd.x4i/ 9. Per 100 1.49 II'.. 2. - a 4. or 03 -IA CO -AXIAL CONNECT- Larne ,2- a,t.x5'i. Per 100 1.39 21/a. or 5 amps. of Philco Corporation. For the past two OR. Rt. angle Ea. .29 .03 10 for 2.50 Sox of 2S .69 years Mr. Romeyn has served as Fac- PE -157 POWER SUPPLY. Incomplete unit. but a "Rohl tory Export Manager. He will continue mine" of relays. switches. Jacks. selenium reel, ete. Porte. "17" IS YOUR LUCKY NUMBER!!! ble hinge,) lid metal rase tO'xs -x129. OD crackle finish. the same duties with added responsi- Yes. Leotone's value.packed new JUMBO RADIO PLUS descriptive 173p. Tech. Manual. Shoe. wt. 20 lbs. bilities in his new position as Vice- Presi- PARTS ASSORTMENT is the YEAR'S BEST 2.49 BUT! & 17 FULI. HOUNDS of new dismantled ISIOM FOCUS use with 10'. 12- or dent, radio and electronic parts -- COILS. TRANS- COIL-fur FORMERS. WIRE, SPEAKER REPAIR PARTS. tunes. 275 ohms DC M 125MA. Fully shielded' HARDWARE. RESISTORS. CONDENSERS, tc.. Triangular 444^ mtg. 1.0; 16- bete. .SOPP. tel 4.25 All these amt much man 4 lbs. forf only 2.95 W-110 FIELD WIRE-Wok to rigid govt. specs. Twisted RCA APPOINTS rubber i sul. pair. outside r All- purpose for in. NEW OFFICIALS dnr orn outdoor Radio. Telephone or P.A. u Sold in rolls approx. 3000 ft. o,ly several slgths. per Glen McDaniel has been elected a vice - rollt. Shpg. wt. 75 Ins. Shipped express collect. Per roll 5.95 president of the Radio Corporation of Get on our mailing Ibt. Always something new. America to serve on the president's FACTORY SPEAKER REPAIR SERVICE staff. Min. Order 52.00 - 20% Deposit Required on COD's David C. Adams, assistant Please add stfcient Postage general counsel of the National Broadcasting Company, has been elected vice- presi- dent and general attorney of RCA Com- munications, Inc.

MAKERS OF CONES AND FIELD COILS FARNSWORTH ENGINEER DIES 65 -67 DEY STREET NEW YORK 7, M.Y. Charles J. Lemieux, senior engineer WORTH 2.0284 -5 in charge of the Capehart laboratory of 12.000 SO FT OF RADIO PARTS Farnsworth Television & Radio Corpor- ation died June 26 at the age of 44. Mr. Lemieux was with the Farnsworth Cor- poration eight years and was in charge TELEVISION RECEIVER -$1.00 INSIDE DOPE of the Materials Testing Division seven Complete Instructions for building your own television years. receiver. 16 pages- 11'117' of pictures. pictorial dia- ON grams. etas ill.' rhematies. 17%22' complete schematic Prior to joining Farnsworth he diagram & chist Is layout. Also booklet d alignment instruct10,1., voltage & resistance tables and trouble - IDEAL AMPLIFICATION was with the International Detrola Cor- shooting hints.- All foe 31.00. SEND 3c STAMP FOR POSTAGE poration. He was widely known in the LABORATORIES CERTIFIED TELEVISION radio components industry and was a Dept. C, 5507 -13th Ave.. Brooklyn 19. N. Y. AMPLIFIER CORP. of AMERICA 398 -10 Broadway New York 13, N. Y. member of the RMA Safety Committee. RADIO -CRAFT for 65 HERSHEL RADIO CO. 5249 GRAND RIVER DETROIT 8, MICHIGAN IMPORTANT NOTE All orders F.O.B. Detroit- Minimum order 52.00- Michigan customers odd 3% sales tax -20% payment must accompany all orders.

NEW BC 223 AX MY 109 TRANSMITTER tt STANDARD TYPE HE 801 Oscillators and 801 power ampli- $2995 100W. Bleeder consisting of 5 sections; 750 ohms, 23 49C TOGGLE SWITCH fiers, 2.46 modulators and I -46 speech ohms, 23 ohms, 7500 ohm, 3000 ohms, Total -11,296 ohms. MY 147 amplifier 4 Xtal frequencies and master oscillator on selector DPS T. 30 amps, in switch. 10 to 30 Watts output. Tone voice or C.W. Mod. Ideal IF TRANSFORMER Ba k a -lite 39cíMY 151 for 80 meter band. Comes with 3 coils TU 17A 2000 -3000 Ke Mounted in aluminum shield can. 5 MC cose, with air trimmer, impedance coupled 95c TU 25 3500-5250 Kc. Black crackle case. Includes two separate type. DISCRIMINATOR TRANSFORMER TO MATCH 95c MY 115 coses to store extra coils. Frequencies chart and tubes included, packed in original coses, less crystals at this low price. COAXIAL FITTINGS LOTS OF BARGAINS

SPST Relay. 24V. 528 ohms. coil. contact rating 5 amp. Packed two to a carton. PYRANOL CAPACITATOR 2 for .49 MY 132 Coaxial solid copper tubing -30 foot length 1 MFD, VDC, 5ç 256 356 206 5000 -beaded insulation 2.95 Site 4x4 1/sx33/' $295 ANGLE - HOOD SOCKET PLUG ADAPTER 50 -30 MFD Electrolytic condenser, 150V. SO -239 PL -259 M -359 tubular. Well -known brands: Solar. etc. .49 83 -IR 83 -15P 83 -IAD Containing: 6V. AC relay. 3 minio. Assorted tubular ell -filled condensers up to CHASSIS .25 MED. I5 tor 1.00 Iure sockets with tube shields. 5 Brand new BC375 Transmitter. GE. 150 $195 Walt less Dynamotor res. and cables. including MY 150 condensers and 6 Site: 3.5.1'. tuning units 49.95 SELSYN MOTORS MODEL 2JIGI Assorted resistors F'2 Watt fully insulated. BK 22 K RELAY in popular ohmages. 100 for 1.49 Used noon TWO MY 110 with 5C5269 F.change FOR MY Assorted mica condensers. 100 for 1.95 over 28V. step 5 402 relay deck, 6 Assorted high frequency chokes. 25 for 1.00 $295 position switch. 12V. DPST. Assorted wafer sockets. 100 for ... 2.95 The ideal way the of indicating 148003 position of Rotary beams, wind in. Thordrson -2 HY -7 HV, 550 MA swinging choke-Size: a x DETROLA RECORD Acato,. etc. line chord in 4'2' 5'2" 5 ". and Black crackle case 5.95 CHANGER MY 311 structions for 110 AC operation furnished on request. Handles 12 -10' records ors 10-12' rcords. Automatic changer. $124$ TUBES POTTER 8 BRUMFIELD ANTENNA DUPLEXER OVERLOAD $195 815 51.95 872A 1.95 3API 1.95 I H5 .69 Originally used on SNIFF equ,Pment to allow RELAYS the use of o common an enna for receiver and MY 16 3BPI 1.95 305 .69 transmoner. 156 to I8 t MC 55.95 5BPI 1.95 6L6GA .95 Potter and Brumfield. Relay u1-5000 ohms, coil cw rent 10 MA. Relay 12 -110V. 60 Cy., AC coil. SPDT. 5FP7 .95 5U4G .44 BOTH UNITS ANTENNA SBP4 1.95 68A7 .44 ONLY 7BP7 1.49 RK60 .95 2 m : 157. 9LP7 2.95 1T4 .44 187 MC. Originally used $995 VRI50 .69 304 ,44 with SNIFF equipment - 30 MC-1F MY 412 955 .65 3S4 .44 Messfully used on 144 SILVER -SLUGGED 9002 .44 I N5 .69 asa non -directional C 29°' 12X3 .44 VT25 1210) .. .44 antenna 55.95 MY 310 9004 .44 6R7 .44 9006 .44 5W4 .44 MODULATION TRANSFORMER 5085 .89 2X2 .95 AND DRIVER TRANSFORMER MICA CAPACITATOR MY 166 35W4 .69 8016 1.49 002. MFD. -3000 W.V.D.C. 69c C E PHOTOCELL 95c BOTH UNITS ONLY 41 Type used in movie projectors, burglar alarms, etc. $495 MY 302

RC 1206 modulation transformer. 815 Class AB2, 56W. audio. RC 1205 FILAMENT TRANSFORMER driver transformer, 65N7 to 815, Class AB2- Companion to RC 1206. 1 IOV., 60 Cy. Sec. 1, 4V. at 16 SCOPE TRANSFORMER amps, Sec.2; 2.5V. of 1.75 amps, insulated for 5000V. Ideal for MY 104 Primary 110V. 60 Cy. Sec; 4000V. at 10 MA. Size 2X2 and 826 tubes. MY 145 $x)95 Hermetically sealed. $195 a, 6x4x3Yc'. No. MXI6 Cross pointer 3'/2' Meter. Two 200 micro amp movements. Brand new $2.95 Size: 6x3% x.4 1/21. 500 ohm to grid matching transformer 81749 69c Ceramic Silver Padders Dual 3 to 12 MMFD or 5 to 20 MMFD l9c Ceramic mica Padder single 5 to 20 MASH) per doz. S0c DON'T MISS THESE SPECIAL SAVINGS! Choke-300MÁ 20147. Insulated for 5000V. Heavy Porcelain Insu- lators. Very conservatively rated. Idle for KW rig 58.95 304TL Powdered iron, % slug myi l8.... 10c Jacks for PL55, or P168 my119.... 10c TUBE 89, Asi t mica condensers -per 100 myl 20 ....S 1.95 Pin straightener for miniature tubes my122.... 25c Ear phones, 2000 ohms, used myl 24 .... 95c SCR625 Mine detector, used my 127 ... .539.50

75,000 -ohm 200 watt Bleeder Res. my4 1 3.... 95c Just the tub. lac that IKW anal - TRANSFORMER typical operation 2500 volts at 400 Audio oscillating transformer with 9 5 c MA. An ideal b. for that induction neater et SILVER CERAMIC CONDENSERS output and feedback winding. MY 148 dielechic heater. Efficient opera. tien of 1500V. to 3000V. 500 W.V.D.C. 12c ea. 10 for $1.00 Available capacity (MMFD's), 2, 3, 4. 5, 7. 8. 8%. 10. 11. 12. 15, 24. 25. 40, 45. 50, 51, dual 60. 70, 72, 75. 80. 81, 95, 100. 120. 470. 500, and 1000. SEPTEMBER, 1948 (iii New Devices

FM -AM TUNER a.c. or d.c. and 50 volts r.f., I ampere d.c., and 100 megohms resistance. An MULTIMETER SOLDERING IRON Laboratories, Inc. Browning important feature is that the meter Bradshaw Instruments Co., Jett Thermal Device Co. Winchester, Mass. may be zeroed on the range to be used, Brooklyn, N. Y. rather than having to be switched to Brooklyn, N. Y. The R.: .A. has separate AM Mode 10 ranges, the basic range for adjustment. -e covers 25 includ- The Slim. Jim soldering iron weighs and FM Both sections include in g Cao3_ farce to 10 tuf, a.c, to 15 A detachable crystal -diode r.f. probe only 31/2 ounces, By what the manufac- an may be plugged into the instrument fo a- pees, a.c. and d.c. volts to 1,000, turer calls the ''wattage expanding Se-s w of t ^e FM section is less measuring frequencies as high as 1O9 principle," the thermal cartridge con- than 10 for 30.db noise reduction. t: mc. An additional probe can be pur- centrates all its heat in the tip instead Two I: are used in the Armstrong -.es chased to extend the range to 400 -- of wasting a large amount in useless circa:, FM a,d.o response is flat from Input resistance on the d.c. ranges is radiation. This allows a 30 -watt car' 10 to 15 A compensation 000 cycles. 11 megohms.- RADIO -CRAFT network e rares frequency drift aft - e a 2 -mi -cute warmup period. MULTIMETER Radio City Products Co. N. Y. New York, fridge to fur: ;Sr 3S r-uch useful heat as Model 450 series Hi -Meg meters in the ror.mal 00 watt iron. I thn dude a resistance range for measur- direct cue-ts to ampere, and re- With t- ansformer, which also acts sistance to 2 megohms. as a horn,. 'he ror. works on 117 The tester, which is offered in both volts a.c. Witrout the transformer, a bench any portable models, contains 6 -volt ca battery furnishes suitable a fuse to protect the meter move- power. ment. A 3.inch meter is used.- RADIO- Tips, made of a nonoxidizing ma- CRAFT terial, are replaceable. Cartridges of Audio response of the AM section is different wattages may be inserted. - RADIO -CRAFT flat from 20 to 6,600 cycles ±3 db. Re- V.H.F. GENERATOR ce -t', oe:elooed triple-tuned i.f. trans- are employed. AM sensitivity Rollin Co. is 5 u. Pasadena, Calif. RADIO SILENCER A _o ^ector on the rear of the chas- Tm M 30 sis a,ows use of a phonograph pickup. powertype standard Kenworth Mfg. Co. A s3ro3-o 300orm antenna feed line signa ge -error tunes from 40 to 400 Milwaukee, Wis. roc. Max`- - output is 5 watts (15 is - -;,a fo in the FM section: the volts'. A- 3ten uatior. network brings Rudi -Off automatically turns off the I r an AM antenna.- RADIO- -3 ado when the telephone CRAr output tow o minimum of 0.1 uy. eceiver is ing up to 1,000 megohms without an The so'a. vial scale has an effective Rifted off the cradle, and turns it or external battery. Other ohms ranges length c 'earl,' 4 feet and calibra- again when the receiver is replaced. POWER INVERTERS extend to 5 megohms. tion ma --s 3'e inserted at 1% fre- No electical connection need be with sensi made to the telephone. American Television & Radio Co. The meters are available quent i teu ais. Leakage fields are tiv,ties of 1,000, 5,000 and 20.000 ohms less rhar 0.1 I v per meter.- RADIO- A shallow metal box is placed un- St. Paul, Minn. per volt. All models have ranges UP CRAFT der tee telephone instrument. The toc ATR d.c. -a.c. inverters in- to 2,500 volts d.c. and 1,000 volts a.c., of the box is spring -mounted so that, as the releohone's ch-o mating on d.c. input I ampere, and -9 to +55 db.- RADIO- weight decreases (whey the receiver volq ^s ra -g nq from 6 to 220, deliv- CRAFT FM TUNER removed), the e-: -0 a o manor of 110 volts, 60 cycles, box too. ises slightly and opens an Collins Audio Products Co. i^ten3 ,ao icitar =es ranging from 75 to POCKET -SIZE TESTER switch contact, turning off the 530 These inverters are specially Westfield, N. J. radio watts, Co., ces. qre] for operating a.c. radios, PA Precision Apparatus This ru -,- ers the 88- 108 -rec FM Elmhurst, N. Y. band. It is pemeabilitytuned and, ac- cordirq to me maker, has no frequents The Series 40 circuit tester is con. drift. tained in a Bakelite case 35/4x6!/ x2' /_ The Ar' circuits used include inches. It includes 31 a.c. and d.c. so.q two Casca 3., limiters. in the ranges to 6,000 volts, 600 ma, 70 3e, Included 11 tubes is a 6AL7.GT tuning indi and 5 megohms. Sers >.v. tv is IOuv. assuring good The meter is a 3 -inch, 400µa instru- ca',. _aa- pt ;ac ' some distance from the ment. Two pin lacks are used for al' --RADIOCRAFT ranges, except the 6,000 -volt one 1c- t- smitten which a recessed safety jack is provided. A rotary switch selects the desired functions. -- RADIO -CRAFT Cu, e :ter ro the radio is made by s. .'sion sets, amplifiers. small p!ugg:-g t -e radios line cord into a a and electrical appliances receptacle wired to the Radi -Off and fro o.:. swrces. Featured is an au- HAM INDUCTORS plugging the latter into the wall socket. tom3tC Switching unit for use with 32- E. F. Johnson Co. The device is adjustable for the a-d IO-voit d.c. inverters, permitting Waseca, Minn. weights of different elephones.- a,.to -rat'c starting and stopping of RADIO -CRAFT

, a is turned or Airwou' 's for the final these -its as the load -. and off. Moe than 33 different stand- stag, TUBE TESTER inverter types are offered.- RADIO- SMALL CAPACITORS CRAFT General Electric Co., Syracuse, N. Y. Solar Mfg. Corp. The Type YTW -I facilitates rapid North Bergen, N. J. WINDOW -MOUNT checking o' receiving tubes. A large ANTENNAS degree o' flexibility is attained Type TST Tiny, Sealdtites are tubu- through the use of individual circuit lar - pw paper capacitors. 3/16 Vertrod inches co- meter x s,á Corp. switches fo- each tube element. inch long. They are molded in Hi -Temp 'Jew York, N. Y. Tubes accommodated include a-, 5 -, plastic compo_r -i for satisfactory operation TV 6 -, 7 -, and 8.pin standard types, 5 -pin :sting FM and under t ^e high small. 7- and 9 -pin miniatures, and operating temperatures --red for those who found - aturized electronic equip- rct install standard an- lock -in toes. Batteries and pilot lights 1 o car also be tested. ment and personal radios. Unlike con - -- 04. The units mount ventiona rer-,osetting molding The YTW -I is an emission -type tester. ma- . -. d project out- terials tee H: -Temp plastic compound 45 inches. fered in several types. Two models for It also checks for filament continuity withstands (without waiting for warmup) and open housl:,g extremes of humid - each band provide for matching high - it,.- RAD'" DAFT current, low -voltage or low- current, and s -ore3 e'ements. Weight of the high -voltage tubes. Various links to ,mit is IS eovnds -- RADIO -CRAFT match transmission -line impedances MOBILE TRANSMITTER may be plugged into the swinging link RADIO CABINETS arm. Standard Transformer Corp. The inductors are supported on poly- Nemes Chicago, Ill. styrene. Each part of the assembly is Chicago, Ill. available separately. -RADIO -CRAFT The ST -203 -A amateur transmitter is t -e problems in One of great put- designed for in ting togethy radiophonographs from operation an automobile but can be used also at a fixed compo^e -t : arts is finding a cabinet. WIDE RANGE METER station. Operating in the l0 -mete Triplett Electrical Instrument Co. band, its maximum plate power input is The cvli drical ceramic base houses Bluffton, Ohio 27.5 wafts. Power requirements are a- elech;cal network which permits the 400.500 volts d.c. at 200 ma, and 6 use o' 300 -ohm balanced line for the Model 625 -NA is a wide -range volt - volts a.c. or d.c. at 2.8 amperes. lead..-'. Three models are offered. ohm-milliammeter with a 6 -inch mir- Five tubes are used. They are: 6V6 r.f. They aopear to be similar, but they dif- ror -scale meter for better reading ac- oscillator, 2E26 power amplifier. 6J5 fer ir the network contained in the curacy. Ten d.c. voltage ranges extend speech amplifier, and two push -pull ce3 --ic housing. They are for TV and up to 5,000 at 10,000 -and 20.000 ohms 6V6 modulators. The transmitter may FM, FM and AM, and TV, AM, and per volt. A,c. voltages up to 5.000 volts be controlled from the driver's seat FM.- RADIO -CRAFT at 10,000 ohms per volt are in five by the push -to -talk button on the micro- ranges. There are three resistance phone. ranges up to 40 megohms, and six di- The unit is provided with a base V.T.V.M. rect- current ranges from 50 rua to 10 mounting plate for installation in an Triplett Electrical Instrument Co. amps. A decibel scale on the meter automobile trunk. The transmitter These fastens to the base plate with two Bluffton, Ohio Is calibrated from -30 to 69 db. The cabinets are constructed to or- instrument is housed in a black mold - der. Size, style, and type of wood may springlooded catch fasteners. Dirnen Model 2451 electronic volt -ohm mil ed-bakelite case with a removable be specified by the purchaser.- scons are 8s/ z 75/8 x 3/4 inches. - liammeter measures up to 1,000 volts strap handle.- RADIO -CRAFT RADIO -CRAFT RADIO -CRAFT RADIO -CRAFT for THE COMPLETE TELEVISION MANUAL

HAND BOOK THE 71CHNIEAt TELEVISION VIDEO HANDBOOK COMPEETf THE 768 pages ... 14 sections, covering every phase in television ... over 800 illustrations ... handsomely bound in black with red and silver stamping. How Television Works. How to Design and Engineer Tele- Basic ... though advanced. vision. How to Troubleshoot and Repair Tele- How to Create a Television Show. vision. Safety procedures. How to Build an Operating Television How to Select and Install a Television Receiver. Complete Instructions. Antenna. How to Select a Television Receiver. The vast amount of information contained in this book can only be briefly outlined here . The VIDEO HANDBOOK contains thousands of vital facts-covering everything you need for working in Television. All this information is designed for easy reading, quick reference-all in non- mathemat- ical language. every point of discussion pictured in diagrams or photographs. The VIDEO HAND- BOOK is divided into 14 sections -each a complete, authoritative coverage on its subject -arranged in a practical, easy -to- follow handbook of solutions to every television problem. READ BY: Engineers. Experimenters. Maintenance men, Broadcast technicians, Servicemen. Production men. Program directors, Manufacturers. Designers. Laboratory technicians, Studio personnel, Laymen.

Section 1. Television, Past, Present and Fu- must know the I lm i tauons -and the amazing advantages ture. of television as a medium of entertainment and etlu- The first section of the VIDEO HANDBOOK is an cat ion. This section these intnsluetlon to Television. In It you will find an at-mount presents problems and their solu- of the inventions, and developments led tions- Illustrates the imilarity to n p411si pielu n dlcomries stage to tilo present system ,f television. The Television in- production and Slit -ie this similarity ends. Il thoroughly the special r dustry today is covered in a complete descript iuu of Its explains all qui retuuts and Possi- organization. operation .mid characteristics. And -you will bilities of television as separate form of expression. Ilnd an Invaluable outline of television in the future. The sensitivlly of television ca eras tu color and lighting. m In addition, there are statist its on present day tele- special requirrnirnlls to set design and arias' vision-how many tranmitters there are and where -the make -ups. The versatility of dltfortnt lenses fo- creating special effects. Network control and the u of r aune sl:uulanl required for satisfactory operation -and men- rWlipuu'nt tioned last, but no lea,. the Status of color television. in combination with studio e uiltuwul. n plow This seetial is the most complete explanation and the carious dulies of studio personnel e 1 he applied In the best .sans of television dale. beginner advantage. Timing of action i for top eat - Section 10. Television Test Equipment. How to It will introiun a snowy in into the field -and it will give an expert much he did the shoe and In relation to other shows To Use It -How To Buy It. out promiling and following. Trends in audience reaction. know: The This chapter gives information on how to select the phenomenal possibilities of electronics for special instruments anti her to use these items for bese Section 2. Fundamentals of Electronic Tele- effect s. proper vision. results. Complete descriptions of all milers. tracers. Section 7. Descriptions of Modern Television generators and testers a e food here. These descriptions In this rllapler. a simplified explanation of tho com- Receivers, are illustrated With photographs and diagrams. Detailed plete electronic television system Is The entire Circuit Variations -De- given. sign- Mechanical Features. inslrticl tats for connecting and using every type of process, equipment, used and Its operation) are covered in instrument are presented and illustael. Complete in- a This section hpìudes a circuit diagram is thorough disrusshm -- designed to give anyone and every typo formation an hoe the mrll lograph works and how IO use of n the market everyonen a complete basic understanding of television. r tala.)' are Included and Illustrated. Every The titer who is going Io sell. work iiuth. it separate current. Today's television system is based on the i-alhlslo ray design. voltage. anti resistance ...moment Is as are re Install t engineer tdry i ilote receivers tiret tube. Its development made electronic telev islin pos- wi. must impedance. capacitance, etc.. as applied to all sections know :demo the sets now in use. Section 7 of sible. Therefore. a detailed amount of the a istrucl ton, the VIDEO and spa acs of the television receiver. )I_NDInliiK complete information on function, and eharacl.eri.sl is o te cathode ray tulle is prm'Ides the vari- Test ire. and measuring are simple toilet operations ous types tif rereivers . . . presented. This and all the things that are television aro their eseplelt circuits, when clone with the ruledpnuvu. but the knowledge their i- unponents, the ditTerences between Rient 'inns com- proper presorted here in a carefully planned introduction to the of whirl) is the proper Insn uuleut n Ilse is all impor- more detailed and special iced sections that follow. Every- plete drsetiptiois of how each hype opral r.. 0i1sland- tant. Section 111 of the VIDEO HANDBOOKI)It1H)K w s ex- thing Is written and illustrated so that the beginner may ing features in each receiver u e pole. as are diitereut In:uuwlit or pressly designed to v vu this Information -it can see ud read how television works . . . without weight - rmtstrUrl lan of Ille same nnllpunra ls. For ex- [imple Imninuous e you as much as tRion. iO in purchasing lest equip- niathnivatical language. tuning. torrelltn lyMe looms. and trail ment. nitia tuners In the 11F stm b ri differences In os- Section 3. The Television Station Il:dor n-lrcuita, types. antenna coupling variations. etc. Section 11. Building a Television Receiver. Pick-up-Control-Transmission. The various peculiarities in design of the other five sec-.r The quickest. most Ihoolgh method of leaning tele- Now. tions of all in the third section. the mechanical and electri- Ille types of receivers are Ii spussell . vision is In build a leriter. This project can1 rapidly cal details of transmitting a television urigrami gnnmdrd grill amwinrn. push -pull oscillators. single- give 1 beginner the prarl in-al experience ho needs. and given. From the ranters to the transmission M the tele- tube oselllalm.s, triode mixers. cathode followers. .tFlf knowugnt nr xptriented mans understanding and vision tar i signal, every piece ot equipment is Ursa dbnl and lbdors. ele. This information provides the knowledge ledge. In n each ease. the result of this project will illustrated. All leehniral functions of the television sta- and experience otherwise obtainable only through montons be a valuable television r r that can be used for tion are covered. The power supplies, video an plillens, of painstakingng r . arch. pre -Insu allat hn surveys, elaborator- experiments and microwave lengths. .sync generators, video and audio Section 8. Installing Television Receivers. demonstration. It Is a eomplet receiver In every respect transmitters and all the oilier lelllelnts IA a complete with .h. added :tlhantage of being profitable. station This is a highly specialized oneral ii i_ but It ran bot are dteusetd in detail. Pick-up a nninuunt. bath dew by following carefully Inludnl hers are completeattplete plans. diagrams. photo- studio and remote is onered in detail. including cameras. toy the Instructions In this graphs M etempaumis and stepby -step section. It w -s preparedpreped as a guide and reference assembly camera tubes. such as orthicons. leetsegn -s aril signal for il Instructions. Ereoy part is listed and information as rallattonn technicians tutti rviceten Id gives complete to orthicons. plus all the other trnnwaents used. u obtain it. whether Vial can construct the infomuuon on everything s from the all important safely Part yourself ur not and apprnxhnato cost of each Section 4. The Television lil'rr:titiitills Io an i ose item. Receiver. ruirlioll outline on how Io tomate Flat li mdion and t.seoluenee In This is the section of the VIDEO ILtNDBOOK that Ille were Ivor after Its installed. constructing this receiver are .separately descrlittl In an easy- us- (ollow style. will be Every . the most frequently used by most readers. step it covered pre -installation sorveys. This project. lit addition being The signal is followed from the antenna through equipment required. locating and erecting the to a highly interesting atours, and enjoyable o e for every stage of the receiver-step-by-step. Early stage layon, ln,tnusulisslal lines, is -ailing anyone interested in television. Is Ille receiver ill Ille a very valuable education in itself. diindividually studied zit iia frl1minllu completely hulloing. All these prorvlures are illustrated sin step by .seribed a a unit and i relation to all the miner step. working photographs covering all details including Section 12. Data Section. stages. These are then separated Into the reeeivers six Prnpet wa:s r climb rants. fastening lines. securing Here are compiled all the graphs. charts, curves, basic sedans - --I lie RE stet itm, the Video channel. the antenna mop it.a le. In addition there's a trnnplele set nomography, symbols. formulas and rules used in tele- 'cep circuits, the low and High Voltage Paver Slip of photographs 'mfr test patterns. illustrating maladjust- vision. Designed for win irk iefei enne. this section presents the ¡'in-ttwe tube milli its associated circuits, and ments and tonnai interferences (auto. diathermy, 1,31.1, all the figures and 4Iala mooed for aqy typo it work or the sound channel. Each section Is then discussed as au weak sign:ds, tea -sting signals. mis-match in the an- television. This information is found complete only In peratilg unit. completely explained and Illustrated. tenna system, rte. Thrrr a o rurantnendatitns as to the VIDEO BAN DIR)OK. There is no further need for For example. in the sweep circuits. the video .signal is customer-relations: lemv In Insure legality of certain wading Ihrovgh s cal books to find the standard (or- frayed Willi photographs of oselllogranns showing all installations In respect le house rules, leases. Or. Tills ients w chart you r neon. This is a lino-saving feature of erring wart' foams. . the advantages and teih se thon Is a prat-Oral. how- lo -do -It guide that will save the VIDEO HANDBOOK that trill spare you much ag- uiques M design of flywheel synriwanizauinn and trig- a lot of money! travatino, re.earrh. It will sane money, because it saves synchronisation gered circuits are Indio ideally 1111ns- Section 9- Servicing Television Receivers. time. raed explained . and sweep r generators and their Section 13. basic circuits are discussed as are Troubleshooting -Interpreting Test Television Terms. sweep simplifiers and A n imp i itr illt't lntary' of wards, inethmis of damping. The picture IOW anti Its foie - Patterns--Alignment-Repair. terms, phrases and titers it the reeei ter are illustrated by means of circuit Tunis is another sertit; tlevotell In detailed. how-to-dot Mks used In television. diagrams. rniaway drawings. rte. Staggered to ed violet, It provedere, this tinte on servicing the receiver. Here Section 14. Bibliography. u pliiler. the interrarrier. sound you will finit the most complete systems. and all the account yet published This is the mod en iplete ll..t of-Ilterai urr on Cher circuit ar aegemerds. Every inqun em that on ev .step in pair n ai nieuanen. tele- gsgoes There are detailed vision Issued to dote. For anyone wanting another book Into the modem i blokchdiagrams television mother i :anarzcd. Illustrating every test equipment set -up. or per10.11ml on the subject. this Theo. are serlion has It In Its rirru it diagrams Illustrating every stage dis - eomplrte listing and a descriptive Section 5. Television Antenna s Systems. paragraph of that lit - ressed. etc y component. Val will find a complete de- eralllres' rmi(elnl s. No Ilene wasted In iiiiti.siai the antenna assielles trono ifus impor- scription of alignment pun At getting the wrong -titre, signal Iran- hug fm' s or Imam . . . tance. In section fl this importance is thoroughly periodical no gurssmrork on titles. wonder- ex- troubleshooting and over 100 photographs of ors ilingrams ing plained and ru:lzrii. The totem. antennas if they represent the material ymt Want. Should Iho for the showing Wave forms rl countered. There a 20 pages of user of the VIDEO HANDBOOK vvarious receivers and leales a n-xitlatned. The effects trouble- desire other literaturq shooting charts, short -cuts that are t money- saving on the subject of television he will fled of Urales t, antennaoutlltdeiny are presented. and l iule- saving. this complete o lihmrrtpe Index right in the back. another time- The term different wines of aroma 1 on sayer! the market a ` illustrated and disclosed. Wave mvliat-pat- 768 PAGES 14 BIG SECTIONS - ONLY terns are it Mustv.td. Propagation of television waves S5.00. OUT IN DECEMBER. MAKE SURE YOU GET YOUR COPY ORDER NOW! aril howl they resemble to light wave.. In sane ways. Leading. Ini petla tire. polarization. idtrrrt It ily. ele.. MAIL THIS COUPON TO YOUR JOBBER. OR DIRECT T0: explained and diagramin.it ii-:illy illustrated. Feed systems RC-9 and transmission linos a classified and illustrated. BOLAND & BOYCE Inc., PUBLISHERS 460 BLOOMFIELD AVE., MONTCLAIR, N. L Seitoi f of the VIDEO i iHANDBOOK is designed to clarify the present confusion over television antennas. D ENCLOSED IS 55.00 (55.50 FOREIGN) It will provide valuable and interesting Here's my order for one VIDEO HANDBOOK reading --it ENCLOSED IS $1.00. I WILL PAY POSTMAN provides 31141 more better infnrmathn of the subject 54.00 (IN U.S. ONLY) than heretofore at:d!.Ible. NAME Section 6. Creating A Television Show. Programming and Production. ADDRESS The problems of producing a television show are re- lated to the limitations and chararlerlstirs of television CITY ZONE equipment. They are prblenis that must be h'an1liei by coordinated aetion ml Ilia part of truaram directon and STATE television technicians. Every man in the bi oadcast studio SEPTEMBER, 1948 68 New Patents DIFFERENTIATION CIRCUIT rectifier tube E and a filter system. The filter may WANTED be a simple R-C combination because of the low Patent No. 2,436,891 drain of the C supply. The regulator tube not Wm. A. Higinbotham, Santa Fe, N. M. only standardizes the grid potential of the pentode (assigned to United States of America as tube but also the negative voltage output. Your This circuit is especially useful in connection Name represented by the Secretary of War) on our mailing list to receive our with class C amplifier power supplies. Differentiating circuits are important in tele- FREE MONTHLY BULLETIN uion and electronic counter; Isar. page 26, July TRIGGER CIRCUIT uno- Caerrt. To differentiate a voltage, it is listing hundreds of outstanding nnccted across a series condenser and resistor. Patent No. 2,441,006 radio bargains. output appears across the resistor. For an Arthur E. Canfora, Brooklyn, N. Y. unite differentiated output R must be negligi- (assigned to Radio Corp. of America) To get your name, your address, RSE offers compared with C. Unfortunately. this results This circuit is controlled by a neon lamp. The practically no output. two triodes are connected so that when one con- MIDGET I.F.TRANSFORMERS o ducts the other is cut off. Change -over takes place Bock again -by popular demand ! when a pulse of correct polarity operates the INPUT C R DIFFERENTIATED OUTPUT RSE scores with a new and tube. again better e first I. F.l 400 -500 KC range-1% square x If the input is positive VI conducts. Its plate 3' high -ceramic based mica trimmen- This new circuit combines accurate differentia- voltage to value to high gain iron cores -pep up old receivers, tion with high output. It is shown below. The drops a low due heavy current ideal for new construction-and now avail- icput passes through a cathode follower for isola- through R and the neon lamp cannot light. The able in either input or output types -for tion from the differentiating circuit C, R, S. The grid resistor of V2 is connected through the lamp peak performance) Individually boxed voltage drop across the two resistors is amplified and R to the positive terminal of the power in the colorful RSE carton. List price $2.10. and then transmitted to the beam power cathode supply. If this path is interrupted when the 1RI- input; LR2- output¡ follower. The cathode current of this tube flows neon lamp is not lighted) V2 is cut off because Specify Type. through S. Matched Egg Gate Each Pak Dozen of 100 36c 69c $3.95 $29.00 14 B+ VOLUME CONTROLS CATN FOLLOWER Ouro n private brand -made by a nationally known manufacturer. The some kind that net for $1.09. Noise -free carbon con. struction, standard shaft and bushing. Individually t--o boxed inourcolorfulcartoncarrying the RSE equolityseal DIFFER NTIATED of approval. Complete with switch, full range of sires. OUTPUT its grid is a so connected to the negative end 10 M ohms 100 M ohms C the is 15 M ohms 250 M ohms each of supply If the input pulse negative VI 25 M ohms 500 M ohms 59c The vol age drop across S is made up of two is reduced to cutoff. The high plate voltage lights 1 parts. Otte is due tu the original differentiated the ncon lamp and provides the second tithe with 50 M ohms Meg ohms per 10 2 Meg ohms The other is produced by a reverse cur- a positive grid voltage. Therefore this tube con- asstd. 2 current. 500 M Knurled Shoff $5 50 rent similar to the first but greatly amplified. ducts. 500 M ohms less switch, 39c each, 100 for $35.00 These voltages can be made to almost cancel. The change -over from conduction to cutoff is R is Therefore the combined effect of and S abrupt because the neon lamp strikes at a definite PHONO CABINET negligible as required. potential. The other parts of the circuit are not The voltage appears critical. It is only necessary that input pulse Used in the Zenith "Cobra accurately differentiated the Tone Arm" record demon- at the cathode load of the beam power tube. exceed a certain minimum value. strators. Solidly built of z/e' This circuit can be used as an improved pulse plywood covered with counter or tas an eltrtrronie switch. moroon luggage cloth. 14' x 16' square, I1' high. Flocked VOLTAGE REGULATOR grill for 8' speaker. Rubber Patent No. 2,434,069 mounting feet, ventilated AUTOMATIC FIRE ALARM rear cover. Brand new in Harold Goldberg, Irondequoit, N. Y. factory cartons. (assigned to Stromberg- Carlson Co.) Patent No. 2,439,502 Every shop Regulated power supplies which provide high Thomas J. Tate, Talladega. Ala. an d shop A is a -ell in can useus th ese at voltages at fairly heavy loads use at least the thermostat this invention to au- :a r. !lowing tubes : rectifier, voltage regulator, pen - tomatically sound lire alarm and summon aid. de. and triode. In the figure these are illus- The alarm may he sent over telephone wires to PHONO AMPLIFIER trated. respectively, as A. R, C. and I). T. de- the central office or may be sounded at the ass the switchboard of a hotel or apartment house. A high quality AC -DC phono oerihe briefly the operation, time that amplifier featuring the latest output voltage (across the bleeder) undergoes an There is no interference with normal use of the circuits and tubes. The chassis increase for any reason. The control grid of the telephone lines. is only 2' e 2 % x 51/2' and pentode then assumes a mure positive potential includes volume and tone con- and causes greater plate current to flow through -in output transformer, trols, built R. There is an increased voltage drop across and 5' rubber line cord. Coin. plete with 35W4 and SOBS this resistor and therefore the triode grid be- tubes. Operates on 110 to 120 comes more negative. The higher tube resistance volts AC or DC. Supply is is in series with the power supply. consequently limited -first $w 19 the output drops and compensates for the original come first served 4 rise. When properly adjusted. such a circuit can maintain an output voltage constant to within a small percentage. OZ4'S In the circuit illustrated. the voltage regulator The only parts needed are a thermostat and tube B is used simultaneously to regulate a sec- a blinker. The thermostat is adjusted to close at 73% OFF! ond voltage, for example, for bias purposes. To the circuit at about 135' F. When a fire breaks Until sold out -RSE offers do this it is necessary only to add a half -wave out its contacts close and the blinker sends 15000 new guaranteed 0Z4 periodic signals over tubes. You know who made the wires. At the them -- You can't other end of the line go wrong at 59e a light goes on and off or a gong sounds to indicate where the ORDER INSTRUCTIONS +3509 fire has broken out. Minimum order -52.00. 25% de- For greater safety posit with order required for all two thermostat cir- C.O.D. shipments. Be sure to include 117VAC COMMON cuits may be connect- DEMAND THIS sufficient Postage -excess will be refunded. Orders received without ed to the lines. SEAL OF QUALITY postage will be shipped -105V express collect. All prices F.O.B. Detroit. Left -A regulated power supply. Addition of an extra tube KHVIV SUPPLY & and a simple resistance- capacity filter provides a source of bias. ENGINEERING CO., Inc. 125 SELDON AVE. DETROIT 1, MICH. RADIO -CRAFT for New Patents 69 VIDEO AMPLIFIER Patent No. 2,441,880 Elmer Dudley Goodele, Bayside, L I. and Vernon J. Duke, Rockville Centre. N. Y. (assigned to Radio Corp. of America) A video channel amplifies only the a.c. component of picture signals, The d.c. must be re- inserted in the output. A diode tube rectifies the

B+ V3 SIG IN SIG OUT V2!ß - I V5 BIGGEST VALUES in TELEVISION! Large -Image, Direct -View TV Kits at Low Cost! Kits Engineered for EASE of ASSEMBLY and Top Performance. Cabinets designed and built for Beauty, Utility, Durability. NO TECHNICAL KNOWLEDGE REQUIRED FOR ASSEMBLY. pulses and provides the d.c. for correct background brilliance. The d.c. component must be kept fairly constant, especially at the transmitter end. If the video amplifier feeds into a grid -modulated power amplifier this may be difficult. As the grid bias varies it causes change in the picture background. This change can be avoided by adding a compensating tube. Only the a.c. component is amplified by VI. This voltage is rectified by V2. The cathode condenser of V2 becomes charged to the peak voltage and gradually discharges through the resistor network. This d.c. voltage is applied to the grid of V9, a cathode follower. From here it goes to the grid of the power amplifier V5. The grid current of V5 may change with different values of excitation. This tends to vary MODEL 10BL grid bias on the tube. Compensating tube V4 is connected across the cathode load of V3 to Pre- Gives 115 Sq. In. Picture vent this. When V5 grid current increases t through RI it results in greater negative voltage across R. This makes the cathode of V4 more negative and therefore increases plate current of the tube. Note that this current also flows through R but in the opposite direction. The mutual conductance of V4 may be adjusted to make as the two opposite currents equal. Then the aver- ¡sa age drop across R remains constant and cannot affect the average brilliance of the picture background. VOLTAGE REGULATOR Patent No. 2,439,938 Reuben Lee, Catonsville, and Consolette Model 7CL Roto -Table for full 180" Visibility Charles K. Hooper, Shipley Heights, Md. (assigned to Westinghouse Elec. Corp.) HANSVISION manufactures the most extensive line of high quality Even in a well -designed power supply the reg- I Television Kits, Cabinets, and Components. Models illustrated and listed ulation tends to become poor at low current of leading values. These find that the sharp change here are only representative Transvision's drains. inventors See your distributor. in voltage occurs when the harmonic compo- FM out- MODEL IOBL, TV /FM Kit, gives 115 sq. in. picture; complete nents become larger than the average or d.c. cabinet NET $299.00 put. Radio: ceceives all channels: streamlined Roto -Table for Model IOBL, gives full ISO' visibility NET $ 24.95 7CL, TV Kit. gives 60 sq. in- picture; consolette with TELEV MODEL NET $199.00 ..L'Y.f'..n.. Rulo- Table: streamlined design MODEL 7BL, same as 7CL except that it is a table model NET $189.00 All prices tubes, antenna, and TUL can he supplied F3! Red a fur small additrional cost I1 -FREE - "SERVICE NOTES" AC IN Fascinating by TRANSVISION o the Key to Successful BOOKLET Television Servicing ... On Television c. uadentlal Television :mil Information, Tile.. hoc, of experience - hai 20.001 tele- The c h',raetorist it I'll r e becomes more n tuiy tele- basic information on -Intl eesets. Completo straight if the d.c. through the load always vision. t:sa at your distrlbn- photos. diagrams. remains arger than the harmonics. This may n', for in FREE COPY; on unite lo as for intinta of tlls- II orth a small fortune. be assured by adding a conventional bleeder i,ihutors. Cost Is only $1.95 NET across the load. Chokes large enough to pass the combined load and bleeder currents are re- All prices 5% higher west of Mini sippi; all prices fair traded. quired. A more efficient solution is to add re- For further information see you distributor, or write to: sistors before the chokes. A full -wave power supply requires two re- TRANSVISION, INC. Dept. R.C. NEW ROCHELLE, N. Y. sistors. For highest efficiency each should io Transvision 8572 Santa Monica Blvd., equal to 37.6fL- 0.239 /fC, with f in cycles, I. In Calif.: of California, Hollywood 46 in henries, and C in farads. Dry rectifiers such as selenium permit cur- For TELEVISION, it's TRANSVISION -the complete rent flow in both directions to some extent. In line of High Quality Kits, Cabinets, Antennas, Lenses, many cases the leakage may be equal to or larger than the above value. Therefore there is Filters, Boosters, Components -Ask your distributor! no need for the added resistors. J SEPTEMBER, 1948 7o I Question Ii11x CONVERTING THE SCR -178 AND -179

I have an SCR -178 radio set con- ma, and their d.c. resistance should be sisting of a BC -188 receiver, BC-187 4 ohms or less. The inductance should be 30,000 transmitter, and BC -188 modulator. .02 henry or more. Cl, C2, C3, C4, and Please modify the transmitter diagram C5 are 6 -volt electrolytics with capaci- for use with a.c. on the filaments and tances of 500 IA or more. SUCCESSFUL crystals in the oscillator circuit. I also You may raise the tuning range of want a diagram of an a.c. power supply the transmitter to 4 me by removing a RADIO SERVICE - for the entire set. Can I alter the tuning, few turns from Ll and L2. For 40 range (2.4 -3.7 mc) to 3.5 -4 and 7 -7.3 meters, remove about half the turns TECHNICIANS READ nuµ ? -B. M. McN., Sydney, Nova Scotia. from Ll and L2. Vary the position of the grid tap on Ll and the number of MIMING IN WV PM eIrlpa POI M circuit has been re- turns on L3 and L4 for best results. Ad- 0 {MK I II(xNl(iIM A. The transmitter vised, and a power supply is shown. just Rl and R2 for correct bias on

10 .00025 865 4 VT-2S 6 75uut VT-55 395µ,t IP4 POS SW 3 SEND SI 3 265 t MN SEC AN yy pp2.5 L3 ( 251114 ANT METER 1 CT 175Nyt .01 25K TTRI RECANT X TALS o ROC CTP

CONTROL 25K I I5K - 25011 e B+ - SCR GRID 400 -475V YArp oB 6 KEY x5YY -o TO MOD + Separate d.c. supplies provide bias and the VT -25 and the VT -55. Do not at- filament voltages for modulator and re- tempt to double in the final or oscillator. ceiver. Rect. 1, Rect. 2, and Rect. 3 are Ready -made plug -in coils can be used fullwave rectifiers that deliver about 6 in the receiver if they can be made to volts d.c. at 300 ma or more. They may be fit the coil sockets. If not, you can wind MONTH F SW EVERY 117V AC RADIO MAINTENANCE today fills a breach that a long time. Al- has existed in the radio field for 1000 11343900 read RADIO MAINTE- .94444 00040 .1361349. ready 30,000 technicians sssssas NANCE every month because it is devoted entirely to the Radio Serviceman. The RADIO MAINTENANCE staff specializes in 6.3V/1A 420V+ 5Y/2A the preparation of articles on every phase of 40MA which may be Radio Maintenance in series form RECT 3 filed and used for reference. The leading articles 2 cover everything for the radio serviceman on Television, FM and AM; Test Equipment; Elec- 11 80 tronic Appliances; Tools; Antennas; Alignment; Troubleshooting; Repair; Construction; Pick -ups and Sound Amplification and Reproduction Equipment. Also, in RADIO MAINTENANCE 4 10N /SOMA each month there are departments on hints and kinks, the latest news of the trade, review of IIC 40/450V-AA trade literature, radiomen's opinions, new products and news from the organizations. All articles 3.3K 3 are presented in a step -by -step precision style, clearly illustrated, with schematics, accurate drawings, white photographs, specially prepared 50/25V 40 150V on black charts, color diagrams, isometric pro. iections and exploded views. 75 150 6.3R 1.9K in beautiful green simulated leather Binders 2w 2 are now available for your RADIO MAINTE- NANCE magazines - see the current issue for + 4.5V - + 3V - +3V -4.5V -3V 0- +67.5V +90V 167-A C A-C+ B B TO XMITTER ONLY BC- details. s A C TO MOD ONLY BC-166Y1 TO RCVR ONLY BC -166 RADIO MAINTENANCE MAGAZINE RC -9 460 Bloomfield Avenue, for 140 -1.4µf Montclair 6, N. J. Mallory type 1B12R or equivalent. The them, using standard data Please send me RADIO MAINTENANCE for chokes in these circuits should carry 300 tuning condensers. I year, 0 2 years, $S 0 $3 Payment enclosed Bill me later

Name PREAMPLIFIER WITH A.G.C. Address City-State Please print a. circuit of a battery - the control in the plate circuit of the and first 1T4 for satisfactory operation. Occupation powered microphone preamplifier include automatic gain control. I would If the preamplifier is some distance Title like to use 1S5's throughout, if possible. from the main amplifier, use a plate -to- Employed by -N.F;W., East Alton, Ill. line transformer as shown in the circuit. If the two units are close together, you *Independent Serviceman - Dealer Serviceman - Service Manager -Dealer -Distributor - Jobber. A. Here is a circuit of a microphone can use capacitive coupling as shown by preamplifier with a.g.c. Remote -cutoff broken lines. Replace the transformer tubes work best in a.g.c. circuits so 1T4's with a 1- megohm resistor in the plate or equivalents are desirable. A 1S5 is circuit and change Rl to 2 megohms. the a.g.c. amplifier and rectifier. Adjust Connect the plate of the 1T4 to the high - RADIO -CRAFT for 71

FREE w;#tt.,yo

DoicI ( - f . f !. 44.i.' .< ' ¡ r . , 1 _ k ` J,l ' ?: ,t, > á t,` ,Ija i! .i x- i f % / C " h i+. % : z ,t . ':'. q!N '. r* t " i F4" _ VLR >>. 143¡ r': ^7 > - r iwaty. ?' T r' ',4.1.'7. aiúf¡. 3`` ..; rw l.a rrs4Ìÿ h .yr {.t4i 'pr t`ir JL-S/ . i _ i ` at,¿ / `i.Y- yN rriJ F si'3C: Provides Practical Construction and Servicing Articles from Many Parts of the Globe Now we can offer you, for the first time, the cream of articles on construc- CONTENTS TRANSITRON OSCILLATOR-ITS USES tion and servicing prepared by foreign technicians. MAKE A V.H.F SUPERREGENERATOR CHECK YOUR FREQUENCY 1948 Another feature of the Annual is the IDENTIFY THAT STATION The RADIO -CRAFT REFERENCE CONSTRUCTING A B. F. O. ANNUAL brings this world -wide infor- RADIO -CRAFT Index, covering issues TODAY'S 0.C. AUDIO AMP. some our METAL LOCATOR mation, along with of the best of between Oct. 1946 and Sept. 1947. This LOW -LEVEL TONE CONTROL own country, in one volume. Just run your Index enables you to locate the important PHOTO -PRINT TIMER eyes the contents listed on the right SUPERSONIC DOOR OPENER down articles appearing during the year on POWER SUPPLY STABILIZER and see for yourself what a wealth of new NEW CIRCUITS FOR OLD and important material it contains. Each such special subjects as come up in the SIMPLE TUBE VOLTMETER 2 -TUBE PORTABLE article has been selected with a view to course of your work or studies. Taking all SIGNAL TRACER FROM OLD RECEIVER presenting information not appearing in all - - the worldwide construction and HI -FI TRF TUNER 4 -TUBE REFLEX SET elsewhere in textbooks, manuals, or pe- servicing articles - - the handy kinks and LOUDSPEAKER FIDELITY printed in. the United States. PHONO AMPLIFIER WITH ADJUST- riodicals short cuts, and the RADIO -CRAFT Index ABLE FEEDBACK Each has accurate schematics and de- you have a well rounded reference book of MULTI -CIRCUIT CLIP SET tailed data enabling you to get at con - inestimable value. Get this valuable 1948 A. F. EQUALIZER STAGE DESIGN structional and operational features easi- FM RECEIVER reference book by subscribing to RADIO - NOVEL GLASS A AND B AMPLIFIER ly, and you so desire duplicate -if -to CRAFT at once. V.O.MCOND. TESTER similar models. RADIO -CRAFT INDEX OCT.46- SEPT.47

RAM()- ('RAFT 25 West Broadway, Dept. 9, New York 7. N. Y. Mail Coupon Gentlemen: Enter my stilveription to RADIO- CRAFT. for the period indicated below, and send me a free copy of the new 1919 RADIO -CRAFT REFERENCE ANNUAL. I enclose my remittance.

with Your 1 Year $3.50 L 2 Years $6.00 3 Years $800 This is a new order E Renewal Extension Remittance Name (Please print clearly) Address Today City Zone State (Canada, Mexico. South and Central America same as U.R.A. All other foreign $1.00 extra for each year.) SEPTEMBER, 1948 72 question Ilex

ALMO PRESENTS THE NEW HALLICRAFTERS T -54 Here's the Finest in TV at a Price You Can Afford YOUR COST $169so Only Hallicrafters can offer you such a fine TV receiver for so low a price. You are assured of constant reception with this new receiver because of a special automatic gain control circuit. Both sensitivity and distance reception are comparable to TV receivers in much higher price brackets. An attractively styled cabinet finished in rich silver grey has an airodized top on a full length piano hinge. The control panel is New Hallicrafters T -54 has 7 inch electrostatic deep grey. The T -54 is also available in a tube, push button tuning on all 13 channels, op- walnut and blonde finish cabinet at $179.50. erates 105 to 120 volts, 50 -60 cycle A.C. three The same excellent engineering that you I.F., iron core I.F. transformers, eighteen recognize in other Hallicrafters products stage makes this exciting new T -54 a prized pos- tubes plus 3 rectifiers, automatic gain control session for the man who understands radio. circuit, inter -carrier modulation type FM, and a We will send your new T -54 the same day built -in 4" by 6" PM dynamic speaker. that your order is received. Send check, Money Order or C.O.D. ALMO RADIO COMPANY, 509 Arch Street, Phila., Penna.

terminal of the am- LP -21 impedance input COMMAND LOOP plifier through shielded cable. RADIO COMPASS HI IMP RECEIVERS INDICATOR ANTENNA In INPUT 20KAP`l'r -if nC454 3 to 0 Me. with Can be used for ,tall bean, tator. Lunn rotated by selsyn tit,: $5.G5 too. also has .selsyn indiratta 1T4(2) 1 MEG - II 500A .02 loll` . to BC-455. 6 to 0 1 at, for Iowa.: indication. INSTEP NB assv. Wiring diagram Rehentatle $7.95 sslip lin. WIN New for At °nr at 11111 Is Included. Used. $3.95 .006 TUNING CONTROL CRANKS 50c but Tested TRANSFORMER FOR RECEIVERS-11 Volt. nit yeie l'riuioty See. 2511-0 -2.50 Volt 50 )IA: $2.95 SELSYN INDICATOR AND Schuman, 3 Val :md II Volt. with AC MOTOR INTERPHONE AMPLIFIER BC 347 L'ia' ii' nial it luu'ln1l,11. $2.95 Used (Tested) Ann, Aircraft Tutw. Contains two I2' 51 14,1 Fidelity l'TC Punier nails- High 1 INDICATOR hunters (7%" x t1%"1. Intuit 200 ï -82 5" single or push DUll (hid; gun tu Radio t nuqusn lie alar lh Output 200 ohm fron single or it plus resistors s'lsyns (Ir let tre ìmNe,t- push -pull plate. non (Used and Tested) at $2.95 c,dm .. ell, Completely S.'lienuatie. Sire: 2k" x 4" x With New $4.95 r; . Less Tube, eAd/ Nev. 79c Or three (3) for $20 SELSYN 2JIG1 DYNAMOTORS oingested tit. 110 MOBILE USE ll 510 rr+ le Ìmiuded. NOT nut; output 405 si.:; madly °pet ales (1010 57% Also will operate t: einte 400 cycle. Used (Test - NB TO 300w LINE input: output 2 u ed) Per Pair- $3.50 NIA. Rixe: 3" x "' $3.95 only 7". DM 035x .. MINIMUM ORDER -52.00 Prices Lima. Ohio 25% DEPOSIT Question Box queries will be an- 132 SOUTH MAIN ST. swered by mail and those of general SALES LIMA, OHIO interest will be printed in the maga- FAIR RADIO zine. A fee of $1.00 will be charged for questions requiring no research ELEMENTS OF MAGNETIC SMOOTH fM SERVICING or schematics. Write for estimates AND requiring diagrams or TAPE RECORDING TN. VHF ALIGNMENT / Y 0.111121161111 on questions APPLICATIONS WAND Imo cenunu check considerable research. Be sure to 999 VHF Alignment Wand A. C. SHANEY an th, dynes n el TV a f give full specifications and details by v with Instructions ider 5-500 m ., can 60c Six to 8 weeks is le u....u. tamed. and on the application. lá Set...syear bTRACKING,SENS SENSITIVITY 15:Nht. required to draw up answers involv- achasonant to and, hmh .y and he. snack A modern MUST ® AMPLIFIER CORP. GI AMERICA HAWKINS RADIO COMPANY ing large schematics or research. 398-10 Broadway. New York 13. N. Y. sii Eut 110 S...1 K....s Ca, 3, Ma RADIO -CRAFT for Technotcs I 7:c . CONDENSER SHORTS If a small set with a loop antenna GIVES YOU WHAT YOU NEED! lacks sensitivity and image rejection even after being properly aligned, check ACORN LOW PRICES IMMEDIATE DELIVERY the variable condenser for a high -re- APPROVED FM APPROVED FM CIRCUIT: Superheterodyll, AND TELEVISION sistance short which may be loading the TUNING RANGE: 55.1115 %It SWEEP FRONT -END INTERMEDIATE FRE.(IrI.Ncv: SIGNAL antenna. Remove the condenser, clean it 10.7 MC GENERATOR AVAILABLE FOR: 21.6 MC MODEL A -300 with ,Television I FI carbon tetrachloride, and bake it $18.95 FR:VI:Ncl DRIFT: Negligi- ble after minutes in an oven to remove moisture. Don't 3 TUBE,: OAKS Amplifier $43.50 0.16 Oscillator. mixer, de heat it too much. lector A ru1l)tEYIV RANGE 6135 Indicator Crusting Eye JOE FIEDERER, ANTNNA:E 300 Ohm line r Iole) 99 Worcester, N. Y. COMPLETELY ALIGN-I 1, 'N. NO POWER St'PP1.\ n. queue), oscillator: D-6C -1 TERMINAL STRIP :Ih TOR -Mixer -Cathode follower FRONT PANEL CON - output tube: F7Y4 -Rec- OLDSMOBILE 982375 TUNING RATIO: ID: I TROLS lifter tube. .... TUNED LINES: Brass. silver .sweep width 1 A- 500 D GENERAL overlay .0005 thick to approximately 10 MC: TION- When installed in the automobile this S stoR control: C- A-High frequency Insula- Tunin vernier control 111 tion throughout: B -Max1. set would cut out after about a half to I raun: D- selector output 500.0(10 G PP 6L6 OUTPUT TRANSFORMER switchItch FM- RF -CAL: F á0c-Power required 103- hour. On the bench it would sometimes shielded. upright n output t Output control: F- 125 Volt 50-60 cycle AC Fully nwitt, S2.45 11oriontal sweep output: 35 watts: U -Power um- limner. Will handle 21 fn.,. Irus111- -RF output. guter built play for a whole day without the slight- mull 016'a. Mie. renters 3:'x'. 3- H. s -in: F.-Special 21 a w'. 3^ D. cPri t,. each O -TYRE EIHIEB capacity tuninhtuning Reactance tune condenser: F est difficulty. 4.8.15 ohm voice c oil. "'SIlmPp i,11,1'gbt 1 - -Pilot light mtg. 3 'Tr $7 Iola tar. R-6('4 -Eizea idicator: G -Generator lbs. Channels (m m ." modulated output can be used either The trouble was in the oscillator grid i l lator. (- -(lC4 -Conti frequency modulated or coil. Loose FM TUNING CONDENSER musty variable beat fre- pure RF. turns on the ground end were 3 gang 3.:10 1 nfrl. trimmers. 88 -I101 meg. il A $1.10 rubbing against each other and shorting perfect ndentser to cover each POWER TRANSFORMER FM band. shaft, w. Prnna,-V 115 At' -tot cycle conrlary out. The winding cannot be seen but 11 a ^. h. 2:'a^. 1. 34C. the 1 3 for S3 -.., . - -t'TI : t 141 lí.3 ts:irfL! l Shipping weight r 1 lb. mils r. trouble was detected with an ohmmeter. 1.31:m 5 :1 amp.. l'pr,ght wt. mtg. centers 2:1, X OIL CONDENSERS Nude by Tlu,,,,larspn. (Same I removed the winding, rewound the CONDENSERS as ,n. R -621 Weight O Ills. ELECTROLYTICTYPEE CANS 2 x .02 mill 1500v 9 .69

loose . turns, and heated the coil to drive .1 mrd :1500v . .79 33.79 3 Tor $10.75 .1 mfd 7500v . 1.79 out moisture. Then I gave it a coat of -.S .39 30 trv :lllln. .25 mfd :1000e' 1.19 FILTER speaker cement. The set then worked 20.20 a 'tsr .15 mfd 4110t1v 1.39 30 450v .5 mftl 5000v . 1.89 CHOKES 10 henry at 85 mils. ,link DC. Channel mount. Mounting - perfectly. 20 450v YY 1.0 mfd 2000v 1.29 .,.n ers 2. ^ 1.0 mfd 1200v .99 Made by Thordarson Shipping t I. 2 Ilia. C. W. TEWS, 21 a 4231v .0 mfd 1000v .89 97e ea. 3 for $2.75 IO henry at 55 20.20 a 450v . .74 4.0 mfd 600v . .3 mils. 350 ohms DO. Milwaukee, Wis. 20-20.20.20 a 450v 1.29 3.3 mfd 600v .79 Channel mount. Mounting renters Zak Inches. Shipping wt. 1 lb. .44 . 20.20 a 400v-250v 6.0 mfd 600v .79 79c ea. for 8.1 mfd 1000v 1.39 3 $2.25 10-10 a 350v 8 henry at `00 mils. 135 ohms DC. 20 0 25v 10 mid 000v .89 Channel mount. Mounting 15 mid 1000v entent 344. 0:10 ® 1.99 .Tipping wt. 4 Ms. ..$1.19 a. S for ys 450v .. .79 1.0 n101 3:I0vAC 100 % ..-.nv .. .49 10000C .39 TEAMS: 20rn cash with order. Balance C.O.D. All price. RADIO 1000 .99 F.O.II. .pur wnrehuuse N.Y.C. No orders under 82.50. -CRAFT offers a 1-year subscription -IO.n ,. 4itlh .59 1.5 nib] 333vAC/ 1001100 .39 or $3.50 for television Technotes de. NTDENSERSU. Write For FREE BARGAIN CATALOG CON TLA OIL FILLED scribing troubles in popular TV receiv- 44c ea. 4.0 mfd 01)0V 1.9 ACORN ELECTRONICS CORP. ers and telling how the problems were -.n pad 1111111, 1.3 80 VESEY ST.. DEPT. C9 NEW YORK 7. N. Y. solved. CHECKING OSCILLATORS 4 CONTINUOUS HOURS of PLAY .... ARLINGTON MODEL 7J7 Another receiver with the MAGNETAPE The set played intermittently and dis- can be used to find torted badly. The distortion remained out whether the lo- after the defective a.v.c. filter and audio cal oscillator in an - -- TWIN -TRAX coupling capacitors were replaced. Dis- apparently dead re- connecting and resoldering the leads ceiver is operating x RECORDER from the output transformer to the or not. speaker voice coil cured the trouble. Evidently the original connection was Tune the good faulty. receiver to a frequency equal to the C. W. TEWS, NO OTHER RECORDER OFFERS THESE SPECIAL FEATURES Milwaukee, Wis. dead receiver's i.f. plus 500 kc and the 4 hours continuous play ... Fre- Complete symphonies and operas - or any musical or quency response 40 to 10.000 variety program up fo 4 hours in duration can now . dead receiver to cycles z db . . . Individual be recorded and played back on a single 1 31/2 inch TUNING CAPACITORS about 500 kc. A bass and treble controls ...... Simplified tape threading . . reel of magnetic tape with the newly -developed A dirty tuning capacitor is a frequent beat note should be Heavy -duty non-ove rhealing Model 910-8 Magnetape Twin -Trax Recorder. In- motor ... No tope rewinding corporating new mechanical design features and the cause of noise and erratic operation. An heard in the good finest magnetic recording amplifier ever constructed. tar,table facilitiess available ne oil can filled with carbon receiver. hum this exceptional instrument is the only answer to pro- tetrachloride low level (DC on h I helps clean high -resistance bearings. sets Automatic tape rev rsal at longed, uninterrupted high - fidelity recording of music The two may end of reel . . Sockets for VU or voice. Built-in reverse control and instantaneous meter and To have be too} switch ... Major stop feature makes this recorder ideal, also, for clean dirt from between the plates, to coupled comp easily accessible dicta ... tion and conference recording. blow it out and use pipe cleaners or a fairly closely if the No mechanical noise ... Instan- - with- Tape costs are actually cut in half through the revolu. visiting moistened in dead one is well un . card . carbon tetra- out threading I tionary use of two independent and isolated sound s stop - rapid start ... High tracks on standard y4 inch reels of tape. The cabinet. chloride. Look through the plates with a shielded. It may be speed forward and a with. ingeniously designed for compactness and beauty, out unthreading . . . light behind them to find metal filings or necessary to u s e No tape covers and spillage possible during high protects the reels during operation of the steel wool. If plates recorder. are touching, place capacitive coupling speed shuttle . . Ploys single a calling card or a plastic speaker shim between the oscil- track recordings mode other Its many exclusive features make this recorder unmis- recorders .. Separate re ord- takably the perfect unit for ing between each set of plates until the set lator and the an- and playback amplifiers on the home, laboratory, industry. single chassis . . Rubber- rimmed operates. tenna of the good drive canal recording studio, and broad- sieve/op Rats . set. A 2 -turn gim- Complete elimination of capstan cast station. Also available Small metal chips can usually be re- tape lippage...3.2 and 500.600 is Model 810-B Twin-Trax Re- ohm balanced line mick around t h e outputs . . corder, which plays moved by burning them out. Connect the Jack for for one oscillator grid or sp hour at high fidelity on stand- high voltage momentarily across the monitaringP . Twin electronic ard I/2 -hour reels of magnetic plates. Do not anode may be used area heads . . Flut- do this if the plates them- ter and . wow 0.1ee . No tape. Priced at $285.00, less selves are touching each other. to couple to the an- belts to loosen or pulleys to slip microphone. Unit op ara tes with Dimensions 20'.1" 17" If net ...1.51. ut your cover and sides closed. H. A. NICKERSON, tenna. 15'. s ". W1 SS lbs. Dorchester, Mass. THOS. P. MOTTLEY, AMPLIFIER CORP. OF AMERICA

(Better disconnect the coil first. Ed) Ocean Grove, N. J. I 398 -10 Broadway New York 13, N. Y SEPTEMBER 1948 7II Try This One TUBE BASE CONNECTOR Connect one microphone, one headset, the battery in series at the receiver TECHNICAL KOs Flat cable connectors can be made and base location. Run a 2 -wire line (anything easily from old tubes. Cut off the to the roof. inside clearance. will do, even lamp cord) OIL -FILLED TRANSMITTING leaving about % -inch Across the roof end of the line connect CONDENSERS MICAS microphone in NUT,2+or WASHER the other headset and .05 NIF-11 1000V $0.35 000025 2500V $0.15 .05 500V .14 1100115 2500V .15 series. DISC (BAKELITE,PLASTIC,FIBER) .1 2100V .75 00005 30011V .35 ®._ Depending on the components at hand, .1 1 75110V 1.65 00005 5000V .85 .20 CUT OFF 6 SMOOTH WITH FILE 2 .1 7001V 4.10 000067 2500V or slightly larger battery may .20 a smaller .12 15111111V 7.95 00007 2500V --ANY OLD TUBE 8115E 25011V .25 2,000 -ohm .2.1 10u11V .35 00025 IA". be desirable. With ordinary .25 40101V 2.15 00025 000V .85 110110V 3.75 Oí10.5 2500V .25 headsets and surplus oxygen -mask iilx.25 snail .05 110072 50011V .85 f OLDER TIP microphones, four and one -half volts 000V .28 00118 51100V .85 1 5 1001V .40 0001 2500V .25 worked well. uus1V .75 0011 5000V .85 DRILL I COUNTERSINK .75 4011V .30 002 12011V .20 RICHARD HENRY, 000 V .35 002 3000V .65 1.0 1á10V .45 110275 20011V .25 SMALL MACHINE SCREW New York, N. Y. 2.0 10V .20 003 25011V .30 2.11 000V .40 003 3000V .65 2.0 10110V .60 004 25011V .35 4.0 6I111V .60 005 1001Yr.V .15 same INTERMITTENT CHECKER 4.0 10110V 1.00 005 3000V .65 Cut out a plastic disc of about the 5.0 220VAC .55 006 201111V .35 as the tube base. Many intermittents are caused by 00 11100V .70 008 1200V .15 diameter 0,0 1000V 1.45 III 1200T. V .15 Drill holes for the cable in the side capacitors which open when normal 0.0 61111V .85 TUBES -CH OK EPOTS applied to them, but which 9,0 10011V 1.75 Tubes -li VO Stein! $0.89 of the base. Connect the wires to the voltages are 10.n now 1.00 Tubes -12KB Metal .29 disc check O.K. on a condenser tester. To 50.0 9u VAC 1.40 Choke- 1001Lí -10H. tube prongs, then place the plastic :01.0 3301'AC 3.75 250 Ohio 1.59 over the tube base, as the drawing locate one of these, it is usual to wait l ms. -OK -.WOK 100K .19 25.0 25V .40 Dual. % Meg shows, and fasten it in place with a flat- 100.0 25V .50 250K -5010 .30 headed screw run through a hole drilled SHIELDED WIRE #22 50 Ft. for .65 in the bottom of the base. After the nut RESISTOR KIT Assorted '_B1W 100 for 1.49 is tightened, file the edges of the disc BATHTUB KIT Sx 1 5 05. ETC. 10 for .58 flush with the tube base. CONDENSER KIT .01- .00001...100 for 2.99 WILLIAM F. WENDT, MICAS .01, .002, .005, ETC. All Values .08 .05-Jiuf 31416 .01 150V PAPER (MIDGET) 60 for 1.00 Napa Calif. 0.1 í,00V PAPER 8 for 1.00 until the receiver stops working, then MEASURING OUTPUT shunt a good capacitor across the suspected one. Often the sudden charging $2.00 min. order F.O.B. N.Y.C. Add postage When aligning a receiver, the voice 50 °° deposit, balance C.O.D. with all orders. of the good capacitor is enough to start Manufacturers inquiries Invited. Send for Flyer. coil is the logical place to connect the Prices are subject to change without notice. of accessibility. the set going again. output meter because suddenness of the The voltage at this point, however, is To reduce the charging, place a 3- megohm potentiom- good capacitor. TECHNICAL RADIO PARTS CO. OLD PLATE -VC TRANS eter in series with the OUTPUT METER for maximum re- 265 Greenwich St. Dept. RC-4 N.Y. 7. N.Y. Set the potentiometer sistance, then shunt the combination CLIP across the suspected capacitor. Slowly rotate the potentiometer shaft to mini- 1949 MODEL RCVR mum resistance. If, somewhere along set starts to operate, the MUTUAL CONDUCTANCE the line, the CLIP chances are good that the suspected TUBE TESTER bad one. with new 9 pin ket to hondleA capacitor was the all future tube developments ...$49.95 RUSSELL SWANFELT, No possibility of good usually too low for a satisfactory read- Fort Wayne, Ind. tubes reading "Bad" or bad tubes reading ing. "Good" as on dy- Any old output transformer will make (No gadget can be depended on for namic conductance shop tool to obtain a higher consistent results with intermittents, testers or other ord- a useful inary emission test- voltage. Equip the secondary (4 -8 ohms but this one is simple to make and ers. "Attractive panel with a pair of leads ending should repay the effort required -Edi- and case equal to any impedance) on the market in ap- in alligator clips. To make output meas- tor) pearance . . . Large urements, connect these clip leads SIG- TRACER RECEIVER --51 0e" meter. . . Cali- and clip the brated micromho scale across the set's voice coil Some of the surplus receivers, espe- as well as a Bad -Good voltmeter leads to the plate winding of . . Individual the low -frequency models, can be scale . Front panel fuse. The trans- cially sockets for all tube base types- voltages from the old output transformer. used as signal tracers. The receiver 76 volts to 117 volts and complete switching former will step up the set's output volt- flexibility allow all present and future tubes should cover the 1.f., i.f., and local os- to be tested regardless of location of elements age and a very good meter reading will on tube buse. . Indicates gas content and be obtained. SHELDED WIRE detects shorts or opens on each individual section of all ]octal, octal and miniature tubes ALBERT LOISCH, -- ¡f - -Y -- -=.ANT POST including cold cathode, magic eye and voltage Darby, Pa. regulator tubes as well as all ballast resistors. Name of the nationally known manufacturer withheld because of special price offer. PROBE - 2 TURNS INSULATED TV INSTALLATION FROM PROBE TIP Model "C "- Sloping front counter case $49.95 Model "P " -- Handsome hand -rubbed For installing television antennas, it portable case 54.95 TUNE TO PROPER FRED Built -in -roll chart with either of above is essential to have communication be- 95.00 extra. tween the man on the roof and the man watching the screen to determine when BUFFALO RADIO SUPPLY cillator frequencies of the receiver under 219.221 GENESEE STREET BUFFALO 3, N. Y. the image is satisfactory. A very simple DEPT. 9C test and should have a c.w. oscillator. It system requires only two pairs of mag- varie- netic headsets two carbon microphones, should be one of the well -shielded and a 4% -volt battery. ties. Shield the antenna post and attach a probe to it with a short shielded cable, Radio, Television, Electronic CARBON MIKE as shown in the drawing. It may be Kits. Parts, etc. L O W E S T PRICES. Also War Surplus necessary to replace the antenna ter- Bargains. Get Your Copy Now. Tv SET i ROOF minal with a jack for better shielding. GEORGE H. HAGUE, OffENBACH & REIMUS 3 -6v i CARBON MIKE 372 fILIS ST., SAN FRANCISCO 2, CAL Fall River, Mau. RADIO -CRAFT for Try This One

TIP JACKS When tip jacks are needed try the base pins of old tubes. Break up the tube baste with a hammer, being careful not PHOTOFACT Publications to crush the pins. Heat each and blow the solder from inside it. Several different -sized jacks can be made from dif- * HELP YOU TO SUCCESS! ferent base pins. L. E. KLINGBERC, These are the indispensable service data books Inglewood, Calif. you'll use profitably every single working day . , , FM ALIGNMENT FM ratio detectors sometimes are jarred slightly out of alignment by a rough trip from the factory. To align NOW! PHOTOFACT VOLUME 4 my them I turn on the motor of car, Includes First Three TV Course Installments which is less than 50 feet from the antenna, tune in a weak station, then Bring your file of post -war receiver Service Data right to up to July, 1948! Here's the most accurate and complete adjust the ratio- detector trimmers radio data ever compiled -preferred and used daily by cancel out the ignition -noise interfer- thousands of Radio Service Technicians. Includes: Ex- ence. clusive Standard Notation Schematics; photo views keyed to parts lists and alignment data; complete parts This method will not work with sets listings and proper replacements; alignment, stage gain, that have limiters. circuit voltage and resistance analysis; coil resistances; ROBERT C. GREEN, record changer service data, etc. Order Volume 4 today only Hyattsville, Md. -keep your Photofact library up -to- date -it's the Radio Service Data that meets your actual needs! Vol. 4. Covers models from Jan. 1, 1948 to July 1, 1948 Your Prior 61 3. Covers models from July 1, 1947 to Jan. 1, 1948 PILOT LIGHT LONGEVITY Loch Volume, 839 Vol. Jan. 1, 1947 to July 1, 1947 To avoid the bother and expense of In Deluxe Binder Vol. 2. Covers models from changing pilot lights in a.c. receivers Vol. 1. Covers all post -war models up to Jan. 1, 1947 and amplifiers, unsolder the leads of the light socket from the 6.3 -volt power 1947 Record Changer Manual transformer winding and hook them Nothing like it! Complete, accurate THE FIRST winding. Re- data on over 40 postwar models. across the 5 -volt rectifier Exclusive exploded views photos TELEVISION FOLDER ducing the voltage applied to the bulb to from all angles. Gives full change APPEARS cycle data. information on adjust. IN 5 volts will about triple its life. ments, service hints and kinks, cor. PHOTOFACT the first SET NO. 46 Be sure that the socket is thoroughly plete parts lists. PLUS -for DON'T time - complete data on leading MISS IT? insulated (both contacts) since the light Wire, Ribbon. Tape and Paper Disc hard cover. Now- PHOTOFACT will be at high voltage to ground. Lack Recorders! 400 pages; you brings cause short- Order now! $495 a new kind of Television of care in this respect may OÑLYflat. Service Data-a severe curate complete, ac- ing of the high -voltage supply or analysis of a Receiver Tube Placement Guide Television popular shock. receiver-based on Shows exactly where to replace each actual examination no 5 -volt winding is available, a you of the set If tube in 5500 radio models covering in the Sams' laboratories. resistor of about 10 ohms in series with 1938 to 1947 receivers. Each tube lay- is the beginning This out is illustrated by a clear, accurate uniform, of a series of the lamp will accomplish the same pur- time -eliminates risky accurate, authoritative diagram. Saves Television Folders, pose. The brightness of the light does hit -and -miss methods. 192 pages, corn. PHOTOFACT exclusively with $'25 plus the not decrease noticeably either ÓNLindexed. Television Course $500 method. cost to you! -at no extra Don't miss Set No. ROBERT D. CARLEN, Dial Cord Stringing Guide 46 -at your local jobber you the one right now! Brooklyn, N. Y. The book that shows STAY way to string a dial cord. Here, in one AHEAD OF THE GAME handy pocket -sized book, are all avail- SUBSCRIBE REGULARLY - able dial cord diagrams covering over PHOTOFACT TO ANTENNA COUPLING 2300 receivers, 1938 through 1946. FOLDER SETS Makes dial cord restringing $100 The performance of some receivers, jobs quick and simple. ONLY.. both t.r.f. and superheterodyne, can be improved by winding the insulated antenna lead around the grid lead of the a CO., INC. connect- HOWARD W. SAMS input tube several times before 7, INDIANA ing it to the antenna post. This adds INDIANAPOLIS capacitive coupling to the inductive coupling. Capacitive coupling is built into many sets. Those that don't have it the receiver at the antenna location with are improved by this trick. the relay contacts in series with the EASY TO LEARN CODE BODINE, beam -rotator motor. FRANK W4JVZ, It la eon to learn or Increase speed Wayne, Ind. To rotate the beam, switch the trans- with an Inatructograph Code Teacher. Ft. Affords the quickest nd most prac- mitter to the receiver's frequency and tical method yet developed. For be- `inner. or advanced student s. is pointing in the e beginner's RADIO -CONTROLLED BEAM key it until the beam Available t p from Then switch the trans- alphabet to typical message. mi all The BC -357, a surplus marker -beacon right direction. subjects. Speed range 5 to 40 WPM. receiver, has a relay in the output cir- mitter back to the operating frequency Always ready -no QRIg. cuit. It was originally designed so that and go on the air as usual. ENDORSED BY THOUSANDS! The tnatruetognph C o d Teacher This receiver can, of course, be used takes the place of an oper-- an incoming signal would close the re- ator-instructorr- instructor and enables one to of radio -controlled de- earn and code without fur - lay and light a lamp. for other types u.erloperliterally eriatanee. Tnoueanda a¡ eu ress¡u1 nnentor nave en wun me ioetrnetoruann A. R. GREEN, rena.ey plans. The receiver can be used to control vices. write' today 'torfor eonven,ent rental and p the rotation of a beam antenna located Fort Worth, Tex. at some distance from the shack. Shunt INSTRUCTOGR'APN COMPANY the two tuned circuits with capacitors (A 1 -tube 6 -meter control transmitter 4701 Sheridan Rd.. Dept. RC. Chiesee 40. III. made of twisted wire to lower the fre- might be built especially for operating quency from the original 75 me to the the antenna. This would save the trouble would permit operation of 10- and 20- upper portion of the 6 -meter band. Place of retuning the main transmitter and meter beams. -Editor) SEPTEMBER, 1948 76

FOR RADIO M E N T O ASSEMBLE THEI R OWN

* Save 2/3 the cost. * Gain valuable knowl- SCOPE edge. ELECTR'oFANY * Achieve better work- THE UTILITY manship. traces separately controllable Learn many new appli- two scope. * inputs on any locate cations. dividual output traces, the input and See both immediately. shift, etc., * Ideal training for use. phase positioning distortion, controls and gain rate con - Individual fine sweeping Heathkits are regular Coarse and control. matches theformted factory quality test Complete Heathkit troll. are punched, equipment unassembled All metal parts with tubes, 5 tubes, Complete but with all forming, and cadmium plated. and inst blueprints punching, calibrating parts, detailed 13 lbs. and printing already Shipping Wt. completed. Nothinfl,E

THE NEW HEATHKIT VACUUM TUBE VOLTMETER KIT The most essential tool a radio man can have, HEATHKIT now within the reach of his pocketbook. The Heath- kit V1VM is equal in quality to instruments selling CONDENSER CHECKER KIT for 575.00 or more. Feat 500 microamp meter, transformer power supply, 1e'ó glass enclosed di- A

clipper, a 6SN7 as a cathode follower output and 1 593 as transformer power supply rectifier. The square wave is of excellent shape between 100 and 5,000 cycles giving adequate range for all studio, FM and television amplifier testing. Either sine or square wave available instantly at a toggle switch. Approxi- mately 25V of sine AC available at 50,000 ohm output impedance. Output + 1 db. from 20 to 20,000 cycles. Nothing else to buy. All metal parts are punched, formed and cadmium plated. Complete with tubes, all parts, detailed blueprints and instructions.

* * >f DEPT. C e .. BENTON HARBOR, MICHIGAN RADIO -CRAFT for 77 TEST EQUIPMENT NEW 1948 HEATHKIT OSCILLOSCOPE $3950 KIT er servicing You can '.. ... , ELSE MI, ell tanoro The TO supplied. metal parts ' Heafhgir and BUY A c lomplet,FM . punched, F and andul two pike of laboratoryA plea evening's work plated and 41tÌ equipment and you have every port Check the available, she most into horizontal /eater, taring amplifiers 5111.1 tub*, 's horsvolts negative using cle to vertical epafive and 65V cycle 30 M and 330 volts power transtransformer ,weep goner- positive. /toe gives sine Bt 1100 2" x 13" high, All controls 17" deep, on front weight only plot with oll panel with 26 reds. tubes and estnvolvoltage Order rasa details artsand ext. y while surplus age syn post. tubes make thetpo weight possib HEATHKIT HIGH FIDELITY AMPLIFIER KIT HEATHKIT 3 -TUBE RADIO ALL-WAVE INTERPHONE $14.95 110 -volt AC operation 2 KIT Build this high fidelity An ideal way to learn $8.75 -WAY CALL SYSTEM This is complete amplifier and save two - radio. kit com- thirds the cost. Push ready assemble, with .y Ideal call and of parts. pull output using 1619 tubes and all other munication system for type Operates from AC. Simple, homes, offices, factories, tubes (military instructions 61.6's), two amplifier clear detailed stores, etc. Makes 4- make this a good radio stages using a dual client electronic baby training course. Covers g y triode (6SN7), and a watcher, easy to as- phase inverter give this ular broadcasts and short coils. semble with every port amplifier a linear repro- wave bands. Plugin duction equal to amplifiers selling for ten times Regenerative circuit. Oper- wtl supplied including sins. this price. Every pan supplied; punched and formed ates loud speaker. ple instructions. Distance chassis, transformers (including quality output to Add postage for 3 lbs. up to 1/S mile. Oper- $14.50 3-8 ohm voie coil), tubes, controls, and complete ates Iront 110 V.A.C. lbs. set. instructions. Add postage for 20 MS 30 Headphones Per $1.00 3 tubes, one master and one remote spooks,. 12" PM speakers for above .. $6.95 21/2" permanent magnet loudspeaker $1.93 Shipping Weight S pounds.

HEARING AID HEADPHONES POWER TRANSFORMER Sjáeel4 4 METER Sfe 4l The Army's best - eliminate flot ears Primary 117V 60 cycle. Secondaries and outside noise. Complete with supply 746 V.CT at 220 MA, 6.3V Brand new Delur Model 312 transformer for conversion from low at 4.5 A., and SV. at 4 A. Will 0 -800 M.A. D.C. Square 3" to high impedance. With cord and handle 13 tube radio receivers. 0 -10 M.A. basic meter with plageug pletIb.e. Add post- Supply is limited, order early. Ship- built in shunt. Probably the best buy ever offered in a á1.00 fcomor 1 ping Wt. 11 lbs. each. surplus meter. 3 FOR $3.95 $9.95 shipping Wt., 1 lb. $ 2.95 COMMAND SET OUTPUT TRANSFORMER ACCESSORIES Push pull 6V6's to 6-8 ohm voire coil BALLENTINE 6 VOLT excellent characteristics. No. 800 3 FOR 5" PM SPEAKER $ 1.95 ,..t. DYNAMOTOR With output transformer, TRANSMITTER TRANSFORMER Dynamotor only from PE 103 matching headphone The tranformer from Transmitter Power power supply. Input 6 or 12 $2.80 Volt at 200 output Supply listed below, 600 Volts, output 500 Volts at 160 MA and 4 Amp. filaments of 3 to 24 MA. Brand new original car- Volts. Also S Volts at 4 Amperes for Dual receiver rack FT277A $ tons, Shipping Wt. 29 lbs. $5.95 with connecting plugs 'P 1.00 rectifier. Shipping Wt. 12 lbs. $9.50 Single transmitter rack MILITARY POWER TRANSFORMERS FT234A $7 .00 Convert your i'itary receivers without ÿ T32 TABLE MICROPHONE rewiring the filament. "A" type up- One of the Army's best. Built by Kel. pl at 50 MA, SV at 2A and logg, ideal for foctory call system, SPLINE SHAFT FOR TUNING es 500 VCT 34V at !h A. "B" type supplies 500 publ.c address, amateur use. Brand COMMAND RECEIVERS VCT at 50 MA, SV at 2A and 12V at new in original cottons, s295 Allow use of regular tuning 1 Amp. State whether A or B odd postage for 3 lbs...... knob on BC 453 -4 -5 receivers. `w9c type desired. Ship. Wt., 4 lbs. $2.95 110 V. A.C. TRANSMITTER 110 V. A.C. MILITARY RECEIVER POWER SUPPLY KIT POWER SUPPLY KIT For BC -MS, 223, 522, 274N's, etc. Ideal for powering military transmitters. Supplies 500 Ideal way to convert military sets. Sup to 600 Volts at 150 to 200 MA plate, 6.3 4 at 4 Amps and 12V at plies 24 Volts for filament no wiring C.T. at Amps, 6.3 - 4 Amps. Can be combined to supply 3 -6.9- changes inside radio. Also supplies 250 V. 12 or 24 Volts at 4 Amperes. Kit supplied D.C. plate voltage at 50 -60 MA. Connec- complete with husky 110V 60 cycle power tions direct to dynamotor input. Complete transformer, SU4 rectifier, oil filled con- with all ports and detailed denser, cased choke, punched chassis, and instructions. Ship. Wt., 6 lbs. $ 5.95 all other pars, including detailed instruc- $14.50 tions. Complete - nothing else to buy.

DEPT. C ... BENTON HARBOR, MICHIGAN SEPTEMBER, 1948 78 I Construction

Radio - Television - Electronic Parts & Equipment Specials

TELEVISION. CATHODE RAY HIGH VOLTAGE 2000 volt D.C. Power Supply l'or an unbelievably low price, w e an supply a completely filtered television or cathode ray 20011 volt U.C. power aupPly Why bother with bulky and dangerous 60 cycle supplies or expensive K.F. power supplies when you can purchase a complete 2000 volt D.C. unit (not a kit), ready to plug into the 110 volt A.C. power line. The ridiculously low price has been made possible by a fortunate purchase of high quality components. These units are brand new, completely tested and guaranteed. Price $7.95 4000.6000 VOLT TELEVISION SUPPLY Similar to the unit above. but has a much higher U.C. output voltage suitable for use with the new 7" and 10" television tubes. PRICE 812.50 RADIO NOISE FILTERS Eliminates extremely noisy radio reception due to power line disturbances caused by lights. refrigerators. washing machines. vacuum cleaners. elevators, oil burners. diathermy machines. etc. F ilters out man -made noises in the broadcast. short wave. and ultra -high frequency bands. Designed for all radios. appliances. and electrical equipment consuming up to 1300 watts 112 amperes) at 120 volts AC or DC. Housed in a metal ease Ise" x 3" x 71 complete with male and female line connectors. PRICE ONLY $1.95 Industrial Type Radio Noise Filter -Will handle up to 50" amperes. Housed in shielded case 31a" x 39ír a 2' a PRICE 53.95 The photo -sensitive lamp is the one beside the knob, which acts as a sensitivity control. EASILY ASSEMBLED RADIO KITS 5 Tube AC -DC superhet kit furnished in a brown plastic cabinet of artistic design, cabinet size (9 "x5 "x6 ") Variable condenser tuned; with 2 double tuned I. F.'s. Tubes used: 1 - 12SA7. 1 - 12SQ7, 1 - 12SK7, I - 35Z5 and 1 - SOL6 Neon "eai "g Lamp as Phototube PRICE 511,95 standa1°rdt tubess 6 TUBE 3 WAY PORTABLE KIT For operation on 110 volt AC or DC and battery By ROBERT connections are reversed. This connec- Superheterodyne circuit JONQUET Full vision dial tion is necessary for a stable circuit. High gain loop The photosensitive lamp Neon 2 is Cabinet of Blue Aeroplane cloth finish. connected directly across the size 13x9.1!.. x7" THE average radio and electronic output of Tubes used 1A7, 1H5, 3Q5. the 6SC7. 11776 and experimenter is not aware Blocking condensers may be 2 - 1N5 that used, i "CFading tab .., if desired, to prove that a.c. rather PRICE 513,15 N °t neon glow lamps have photoelectric [xtra ror t tnbrs 53.75 than d.c. is required for proper opera- 6 TUBE, 2 BAND SUPERHET KIT characteristics that make them Bands tion of Neon 2. The sensitivity of this covered BC 550 -1600 KC and G - IA MC sensitive to variations in light intensity. Power supply 105 -125V AC. DC circuit is controlled by 500,000 Full vision dial Under some conditions they are sur- the -ohm Variable condenser tuned. with two double tuned resistor and 0.1 -uf condenser in series I. F.'s 455KC prisingly sensitive and can be made to Walnut veneer wood esbiret work like the familiar relaxation between the phase-inverter plate and PRICE oscil- ground. $15.75 lator when supplied with a..c. instead of The operating voltage is supplied by A SCIENTIFICALLY DESIGNED d.c. a 6H6 connected as a voltage doubler. A PHONO SCRATCH FILTER The diagram shows a Resonated at apprax imately 4500 cycles effectively neon lamp Neon pair of selenium rectifiers can be used reducing objectionable needle scratch without alter- 1 connected as a standard relaxation ing the brilliancy of reproduction. instead to give a higher and more stable Contains a H1111 SERIES resonated circuit. Tested oscillator operating between 500 and voltage. by means of an audio oscillator and an oscilloscope to give 22 db. attenuation with very low signal loss. 700 cycles and feeding into a 2 -stage When constructing this circuit, dupli- Attenuation may be regulated by means of a SPECIAL MINIATURE gain control. voltage amplifier consisting of a 6SJ7 cate as closely as practical all parts EASY TO ATTACH and one half of a 6SC7. The Just two wires to clip on. Compact. other half values specified on the diagram. It may Price $1.65 of the 6SC7 is a phase inverter. A gain be necessary to experiment with values TUBE PHONO AMPLIFIER control is in the grid circuit of the of condenser C. This should be adjusted An assembled unit ready for installation using tone and volume control and six feet of rubber cord $2.95 (Not including Tubes) ,P 65J7 01 SOOK GAIN COPT 6SC7 With Complete Set of Tubes 83.95 e 2 PHONO OSCILLATOR NEON I NEON 2 Wireless phone oscillator transmits recording for .00 SENSITIVITY (ANT crystal pick -ups or voice from carbon mike through s radio without wires. Can also be used as an intercomm .1 500K by using P.M. speaker as mike. Price (excluding tubes) $2.95 With Complete Set of Tubes 53.95 HI- - SPECIAL! SPECIAL! SEE TEXT Mammoth assortment of radio and electronic parts, not less than TEN POUNDS of new transformers, chokes, condensers, resistors. 1 switches, coils, wire, hardware, etc. A super- buy for experimenters, service- 211E6 EACH IK/SW 8/450VI- men. and amateurs for only $1.25 Hookup of the experimental neon phototube. Satisfaction guaranteed on all merchandise. All prices F.O.B. New York City 16/460V WRITE FOR FREE CATALOGUE amplifier section of the 6SC7. The 470,- 000 -ohm resistor in series with its grid óll 6.3V FILS RADIO DEALERS SUPPLY CO. prevents it being overloaded by the I 135 Liberty St. New York, N. Y. GSJ7. Note that the control and screen grid 117 VAC RADIO -CRAFT for Construction 79 slight glow on one electrode of Neon 2. When you are sure of proper operation this far disconnect the phones, turn the gain control all the way up, and adjust FALL SPECIALS the sensitivity control for full resistance. This should make both electrodes of Neon 2 glow brightly. Back off the TUBE SPECIALS sensitivity control about three -quarters GUARANTEED - STAt.DAiU) BRANDS I LH4 .59 12A6 .30 and decrease the gain until one electrode ILN4 .59 12SA7GT .45 3B7 .89 12SG7 .62 goes out completely. 3D6 .69 12SK7GT .40 384 .49 12SH7 .65 Now adjust the sensitivity control un- 304 .59 12ßQ7 .50 lamp begins to flash slowly. De- 5R4GY .89 25L6GT .50 til the 5Ú4G .45 5CL6GT .50 crease the gain until the lamp just goes 6AB7 .89 117Z6 .80 6ÁC7 .59 30 .60 out. At this point, Neon 2 is most sensi- 6AG7 .79 34 .89 6D6 .40 49 .80 tive to light changes. Focus light rays 615 .39 76 .45 it will begin to flash 6L6 .70 956 .65 on the lamp, and 6SJ7 .39 958 -A .60 again. If it fails to do so, a slight ad- 6SK7 .40 59 .45 6ßL7 .40 1625 .35 justment of the gain or sensitivity con- 6ßH7 .40 2050 .69 6V6GT /G .45 803 6.00 trols, or of both, should produce the 6x5GT/G .45 807 .95 desired results. Placing phones across the lamp, you SWITCHES The wiring the chassis is noncritical. below will be able to hear the frequency of the SI'UT AN- 3022 -65. I side Mom. center off Lum. Tip .25 pulses increase or decrease as the light SI'ST AN- 2022 -2B. Bat liandle. Lum. Tip .25 11i'IYr Slide Sw. Statist/01e 5 A. 125V .15 to cause Neon 1 to oscillate at between source is brought nearer or moved away ß1'11'f Momentary, center off. 6A 135V. Long between Bat Bandle .30 500 and 700 cycles. Try values from the lamp. When phones are con- 41'ÚT Bat Handle l0A 12.íV .50 .0007 -pf and .003 -pf. Almost any neon the lamp, it may be neces- STUT Center on, AN- 3022.1B Lum. Tip. 6A nected across 125V .30 glow lamp may be used for Neon 1. sary to readjust the controls slightly. SI'ST Bat Handle. 6A 125V .25 SI'UT Bat Handle, 6A 125V .30 Neon 2 may be a type NE3, NE51, or In its present state, this device is UPDT Momentary, center off. l0A 125V .50 DI'ST AN- 3023 -2. l0A 125V .45 any other 1/25 -watt glow lamp without simply an interesting experiment. How- l)PST Momentary, lush Type. 6A 525V .35 a resistor in its base. experi- SI'ST Rotary lenelosedl 6A 125V. Va' shaft .25 ever, it offers a challenge to SI'ST Plume Switch %' shaft .20 This unit is simple to operate. Make menters who may be able to put the sure Neon 1 is oscillating by connecting circuit to practical use. The writer is G. E. SWITCHETTES a pair of phones across Neon 2 through interested in hearing of any progress CR-0OTOS'. I, normally open .35 Clt -10701 ., _1.i, or norm. closed .35 blocking condensers or by noting a that you may make toward this goal. ('R- 107111 '. .35 SURPLUS SPECIALS Small 110V Al' 00 r), Arm) frame motor 'A" Metal Locator I -S 7,, by Small pace shaft. 2700 RPM. IIP mfg. Barber Culmann Co. 2.00 2 -foot length of wire wrapped around Syarbronous Moors: Si" shaft 110V AC CO cycle is an efficient metal locator 4r:.. 1. 1 -1/5 & li4 RPM 2.2 Watts. mfg HEREwhich can be made very small, es- the cabinet. by Hayden Mfg. Co. 2.00 I Sot dry speed desired) pecially if hearing -aid batteries are The tuning capacitors Cl and C2 used. No cabinet dimensions are given, are 100 -µµf air padders. They are screw- AMAZING BLACK LIGHT since each constructor will use his in- driver adjusted and are less affected by ('o.1 -d and Ultra Via I,., , r,, r. Ito 1..: d, U, 110111 110V AC line genuity to put the electronic parts in vibration than standard mica padders. RIgi,1 .Smoot Type 93.95 t ax,seneek 51011115 Type 4.49 as small a box as possible. The receiving coil L2 is a standard Replacement Bulbs .35 -band r.f. coil with a tickler Luminous Paint kit consisting of two colors. Blue As the diagram (Fig. 1) shows, 3A5's broadcast and Violet. Can be used in conjunction with are used in both transmitting and rewinding added. Vary the number of Black I.I:1.1 .89 turns for best results. If several coils ceiving sections. The transmitter uses MISCELLANEOUS a Hartley oscillator. The transmitting are in the junk box, experiment to find PL -259.5 reps s 11111110, A s o.hut. sìlser plated. coil Ll is the exploring device and is the best one. for It081' & ROI1U Pr. .60 Variable r amicons 4 -30 mmf 7 -45 mmf .25 located at the lower end of the handle, Tel r Antenna 7 fora I.00 Rectifier. topper oxide, full ware. 110V AC In- Fig. 2. It is wound around the edges of put. 100V DC output IA 3.50 Solenoid. 6V DC complete with plunger and a 3 -inch thick piece of wood 18 inches rag. bracket 1.25 20 of No. 18 bell wire Pilot Light Assy. complete with %. jewel. white square. Use turns 4' -6- or red. & miniature bayonet base .25 or any other wire larger than No. 24. la Flexible Shaft 8r4' long with spline ends .25 2 handle at the point of balance. PL-55 Phone plug with 4' cord .30 Experiment for the best place for the Fig. -Place DI- Dental sockets (less mfg. ring) .50 2X2 socket .35 tap. To adjust the metal locator, open the Octal Steatite socket .15 4 Prong socket .12 The long handle (see Fig. 2) is a 41A- antenna trimmer about half way, then Shock Mounts (Lord) rap. 75 lbs. .60 Stemlown Transformer l'TC Type 63823 220V to foot of length of 2 x 2. The cabinet con- adjust both tuning capacitors until the 110V. 100 Watts. 60 cycles 4.00 - Octal plug .20 taining the tubes and electronic corn loudest signal is heard in the phones. Dynamic Microphone ELECTRO VOICE ponent3 other than Li is mounted at the -ohm will pro- Model 000C (press to talk switch) cord & plug. The 50,000 potentiometer 111gb impedance 4.50 top. vide some volume control. Tune the an- T-17 with press to talk switch, cord & .79 The two sections of the transmitting tenna trimmer until a clicking sound Microphone 3A5 are paralleled. The plates of the re- appears in the headphones. In explor- WIRE WOUND RHEOSTATS ceiving tube are paralleled but the grids ing, a change in sound usually indicates 1.1 Ohm 10 Watt with switch 1.25 011111 23 Watt .65 are not. The antenna may be a 1 -or the presence of metal. -JOHN ÇIAYNES 8 ohm Sa dart 1.00 250 ohm 50 Watt 1.05 2500 ohm 25 Watt .65

2.5411 HI IMP PHONES CONDENSERS & CAPACITORS STANDARD BRANDS Capatitor 700 1.11,1. 2110 V IM' I35 4 ofd. 2000 V DC Oil Filled Conti 3.75 10 mfd. 1500 V DC Oil Filled Cond. 2.95 10 mfd. COO V De 011 Filled Cond. .90 1 mfd. 2500 V DC Oil Filled Cond. 1.25

Na sale Ian than $2.00. All twist FOB N.Y.C. Add 25e te covar postage. 20'!. dement required with all orders. A. M. RADIO SALES CO. XMITTER I RECEIVER !- -I. 345 Canal St. N. Y. C. 13, N.Y. Fig. I- Schematic. Note the special regenerative system used in the receiving section. SEPTEMBER. 1948 80 Construction THREE GREAT NEW AMPLIFIERS Commutiicaliotis T.R.F. Designed by A.G. SHANEY

By T. W. DRESSER

SINCE short waves were first used stages may have to be added to compen- for communication, controversy sate for the loss of gain. This further in- has raged over the relative merits creases the cost and the noise level. It is of the t.r.f. set and the super- another vicious cycle. Featuring Better Response heterodyne. The prime bone of conten- The superregenerative receiver is More Power Smaller Size tion has been the signal -to -noise ratio. hardly worth mentioning. It is extreme- and 5 -YEAR GUARANTEE The t.r.f. enthusiast swears that he gets ly noisy and decidedly unselective. "ShaneyDeslgned" bal. long been accepted as the a signal as strong as, but considerably The t.r.f. set shown in the diagram 5 and. ed of quality in amplification equipment. But clearer than, the superheterodyne user; uses the best of the modern high -gain never has so much quality been incorporated into popu- tar--priced amplifiers as n this e.ceptional trio of while the latter is equally emphatic that r.f. tubes to improve the sensitivity. It public address units. They are specifically designed to he can pick up signals the other fellow incorporates all good qualities of the 111 provide amazing fidelity and trouble -free operation for all indoor and outdoor public address requirements, in- can't even hear. t.r.f. Its performance was judged . eluding electioneering, and auditorium and stadium Manufacturers of receivers for the against that of a superhet built some operation. SPECIFICATIONS amateur have, with few exceptions, ad- time ago, on which performance figures . (Not.: feegeeney response for all models; 30 to 15000 cycles hered religiously to superhets; and it were available. -.- I db. All models have following output impedances: 4. r. lb. 250. and 500 ohm..( must be admitted they have turned out In designing the circuit selectivity . R.ted Oner.11 Dime.. o Gel. sir... Price excellent jobs. But one point about their was a first requirement, so a minimum Medal (2) 1 high; 24 H.gh -133 db 14.7.5'/," 861.00 products makes the t.r.f. user wrinkle of two (preferably three or four) tuned I ltc lo. Wrlis Lon - .0 db his nose-they have all had to use noise - Model Ill I b,qh; it High -In db 17.10.10" 556.00 circuits was desirable. Shielding had to IN 380 1 med.; Watts Med.-110 db limiting Itoe low - .Odb circuits. be adequate, and there had to be ample Model 151 7 6,0. 03 3 High Grin 11.10.10" 8141.00 The suggestion put forth by some that decoupling. The detector had to be ca- SUD gam m4e; Wens M.le-124 db; d. qua Med. Gain the t.r.f. as a short -wave receiver is fin- pable of handling a large signal without

m.1e: 1 for hd.le-101 db: go. phono. Phono-70 db. ished is difficult to justify. On the distortion as no a.v.c. was to be used. All mplile ...00hed nigh matched . of tube,. whole, its advantages far outweigh its The circuit, although not highly orig- If not available at your dealer. order direct. disadvantages. Its simplicity in con- inal, makes full use struction of the high gain AMPLIFIER CORP. OF AMERICA and operation lends itself to available from modern 1852 tubes. Three sturdiness; it is not prone to alignment 398 -10 Broadway, New York 13, N. Y. of them are used in the r.f. stages with troubles, and-perhaps its outstanding somewhat unorthodox decoupling. A point -it has very low noise level. Its 6C5 acts as a grid -leak detector and a principal fault is poor selectivity, in- 6V6 is the output tube. Plate and heater EVERYTHING !N ability to separate stations 10 kc apart. circuits are well filtered, making for low But there is no reason why such separa- hum and stability. Each stage is un- tion should not be achieved in a t.r.f. usually well shielded from its neighbors TELEVISION The advocates of the superhet claim both above and below the chassis deck. that it is both selective and sensitive if The r.f. gain control is in the cathode of the design is good; and, of course, they the second stage. are correct. But a great deal depends Tuned grid circuits are used through- upon the design, particularly upon the out and the coupling capacitors are va- choice of the intermediate frequency. If riable. Alignment, therefore, resolves MODEL the latter is low, in the 450 -kc region, itself into adjusting for maximum sig- EL -1 image suppression is poor. If it is high, nal these coupling capacitors and the 1600 kc to 3 mc, there is a strong risk trimmers on the 4 -gang tuning capaci- that the i.f.'s will pick up signals at or tor. The antenna capac tor is used with close to the fundamental frequency. single wire antennas. In the first model Moreover the gain at these higher fre- plug -in coils were used, but switched Latest design Features High Defini- quencies is relatively poor, and il. tion. Brilliance and Stability New Syn- coils are more convenient if there is chro-Lock and Contrast Emphasis Cir- Bradford, England really effective shielding between stages. cuits 55 sq. in. Screen Beautiful Cabinets 1852 1852 1852 6C5 6V6 FILS VI V2 V3 V4 RECEIVERS, FM STRIPS, 4.75 °t +250V TEST EQUIPMENT, KITS 2/\1_, 4.710 .001 .001 10K FILTERS. LENSES, l+-4 ,510° DECALS. TUNERS, 4%00y 1.e10 .os ei4sov ACCESSORIES, HtìH M-i - W COMPONENTS, -4 ASSEMBLIES. SINGLE WIRE CH _AREGEN .0005 ANTENNAS, ANT CABINETS VI e 3-351.µ/t T 10-1001Wf ye t (51 SURPLUS RADIO, INC. 4 ,- 5 1-.__:/) n 44 -31 Douglaston P'kwy t T 7 00K STRAP 5Hl iH AF 8 Douglaston, L. I., N. Y. e01 2202 .01 .01 ! .01 GAIN GND 500; 220 Please send me your FREE Catalog 5W

Name -250V Address - CI,C2.C3,C4- 20µµf 4-GANG TUN NG COND T- 3 30490 CH-eSMN Town State Capacitive coupling between r.f. stages is used in this t.r.f. communications receiver. RADIO -CRAFT for Construction I 81

Assembled on a 12 x 8 x 2% -inch aluminum chassis, the receiver is good REVOLUTIONARY SOLDERING IRON looking, and it has exceptional sensitivity, a noise level that is negligible, and selectivity that is outstanding for a t.r.f. Given a good layout with regard lnllVl. Soldetron to the high gain involved, short wiring, - .1 r. Mark Reg., 1st. Ycnd. and good solid ground connections, it For Easier, Better Soldering-on Any Job! Here will provide excellent performance. Weighs only 3 ozs., yet can do the job of a 200 watt iron. in Britain, with 10 feet of uninsulated Heats up in twenty seconds from a cold start; saves time. wire hanging 6 inches from a brick wall Fingertip control; permits soldering without fatigue. and surrounded by high hills, it has received Australia and Argentine consist- ently at R8. As for the c.w. hound, use of the regeneration control will give him all the code he wants, with the r.f.stages radiation Ready for attachment effectively preventing any and operation an 110 L_ from the antenna. V A.C., 50.60 cycles- i rm¡- - -- _ through transformer ^- supplied with iron, or TABLE 6 -8 volt A.C. or D.C. without trans former (from an automobile battery). COIL Overall size 9Ya^ x 15, 16 ": ship. wt. approx. 4 lbs. L2 Wave length L1 Wire Ideal for fine precision work in "hard -to- reach" places. (meters) (turns) (turns) size Readily interchangeable tip- heads; no cleaning or filing. 7 -18 21 /a 51 21 Retains heat with switch off up to I minute; efficient. 17 -36 31/4 13 21 Bakelite handle. cork covering, for comfortable cool grip. 34 -78 7 24% 21 PRICE. including transformer and Tip -Head 'A," $13.95 75 -150 11 52 23 5'i higher west of Mississippi: fair traded. 145 -250 13 111 28 Ask your distributor. or for further information write to: 240 -575 20 230 30 TRANSVISION, INC., Dept. RC, NEW ROCHELLE, N. Y. In Calif.: Transelsiou of Cal., 8572 Santa Monica Blvd.. Hollywood 46 All forms 1 inch in diameter. All coils closewound. SURPLUS BARGAINS MAILEFROM ELECTRON -RAY TESTER WAR ABELL! The diagram shows a tester using a LINEMAN'S XMITTER DESK STAND MINE DETECTOR SCR 625 SAFETY BELT 100 WATT MICROPHONE 6E5 indicator for measuring a.c. and d.c. Sl arc RC 375.0 -350 MA, 0 -S amp With swiftly O and M.P. n. rond :end plug. bell size. RF and 0 -15 V meter:. Lots voltages and detecting bad capacitors 0u ohm ruban mciallle trig m,hla in of fine top quality Ports imual. Iumber. and resistors. $5.75 for your medium $10.95 Approximate $2.95 depth M detection 6 feet power rig 1 To check (l.c. volts, connect the voltage LINEMAN'S depending on soil ,. Iltbq z. Supplied gilh to d.e. set Si to position POLE CLIMB- batteries and the terminals, ERS and .1i it., EE-8 FIELD PHONES WIRE tubes. .,11 portable _ GRIPS Schematic. Tested 2, and adjust the potentiometer for zero $4.50 :din G.r ICON ALO NGS) before shipment. shadow. If the potentiometer dial has Lninlsrl. Shipping ,1 for faru- ROPE right. previously been calibrated with various 70 lbs, . uuIc11' Itu.l. Sy1.V-1. $1.50 it will read the value applied. I11,.II1i l Te. l, . voltages, ?I t 1111'51 $2.50 541,51 11hn11m. . .. $3.50 1 1-510:1, The same holds true for a.c., which is Sinnt..., I.:,1 50.75. l'air 517.95 INSULATED AN. rectified by one of the 25Z5 diodes. Maximum 7 CONDUC- TENNA TRIPOD KC SOS length -150' GIBSON GIRL 500 To check open S2. Bias for TOR CABLE t+ ' r .o,ln .a of 2^ resistors 14 l ,n, tubing. XMiTTER JJ ni,"nllr is by the 8,000 -ohm LEATHER TOOL STRANDED 13 «. high (rp,ratra front lile raft. boat or ve- the 6E5 developed . ('*- Ì n ' .`rn blea POUCH nuclr.. l'rr,vidr. 211 ronds au n- 6110 V instil- NumLing balbear. sos or alarm atonal, then 0 cathode resistor. Switch Si to position Slips on twit 49e al una. IÌ to - head. WM elan«, 1°n ,'; 2 = tube or .haft. 1 and connect the resistor across the d U' ` l.Ight weight. .000g. .d.d manually. .vu batteries.1iins : I ...,I Indicating and tuning control mi Sti ilk l'Ifg entered. does not need RF SI feet long. .. Tuben-12,cÌ (Amin ose. terminals. If it is good, it will act as a pin .ot $2.25 ro- 111F osr.l Radie and . ;uñ Itussell Sto11 tating beam.. TV. rie ,ao;a^ó by hand S:IS9I1 Fa. to ,.¢btyet grid leak and the eye will close. If it is limit a. .«tall. (ling tt antenna nwlutl i' ide at a.11 end. i.,1.iII.\ ed. .pares; 2balbnls 2 hydro- ST Ill - Si, 45 box parachute. open, the grid will float and shadow ^ 1 11P $4.95 tt i adjuslahlr `: -, ft. iIrem-hum,,antlo. 1.p:, tittle i nri angle will be maximum. 29e In %h.n.k.pr,atf.rr wet. .f1 b1tg. Easy to operate To check capacitors open S2, switch to needed). Weight JO" 11 n. ..., md r e . t órlginal hara. . . .524.94 position 4, and place the capacitor across SEND FOR SPECIAL the terminals. The 1- megohm terminal VALUE BULLETINS Satisfaction guaranteed. Or- der by Mail. We ship resistor and the potentiometer act as a On our large stock of Radio and Photo Supplies. Tell us JJiebibntilty "why C.O.D. Order today. Prices voltage- divider across the cathode -re- your wants. Prices Do ST.-BALTIMORE 2. MD. subject to change without Not An ludePostage. 5.E. BIDDLE sistor voltage, with the grid connected to DEPT. No. 15 notice. the center. Now switch to position 3. If the capacitor is good, its charge will tend to hold the shadow angle small. If GENERAL ELECTRIC it is open or shorted, the shadow angle will enlarge to maximum. 150 WATT TRANSMITTER RUSSELL BEANE, Cost the Government $1800.00 Tionesta, Pa. Cost to you $44.50!!!! oAC DC RESISTORS CAPACITORS This is the famous transmitter used In U.B. Army bombers IMEGT and ground stations. during the war. Ito design and construction have been proved in mire. under all kinds of conditions. all ocrt the world. The entire frequency range is tosend by means of plug -In tuning units which are included. }.ach tuning unit has its ado oscillator and power amplifier 25Z5 coils and condensers. and antenna tinting circuits -each designed to operate at top efficiency within Its particular 5 frequency range. Transmitter and aeressorles are finished In black crackle, and the mllliammeter. voltmeter. and on the front panel. Originally designed to cover the frequency range from 200 to 500 3 RP ammeter are mounted K( :Intl 1500 to 12.5ó10 KC. Will operate on le and 20 Meter Bands with slight modification. Here are the specifications: OSCILLATOR: Self -excited. thereto compensated. and hand calibrated. POWER AMPLIFIER: SI Neutralised class "C" stage. using 211 tube. and equipped with antenna counting circuit which matches practically any length antenna. MODULATOR: Class "It" -uses two 211 tubes. POW }It SUPPLY: Supplied complete with conversion Instructions for 1 either 12 or 2411 dynamotor (SPECIFY), which furnishes 1000V at 350 MA. Complete 280 3 `8 4 MEG 10 and 20 Meter bands, with the tuning units supplied, as well as 110V AC modifications are furnished. SIZE: 21% x 223 x 911 Inches. Total shipping weight 200 lbs., complete with all tubes. dynamotor power supply. live f unused tun inn: 11 a tuning unit and the essential Mugs. These units have Iron removed from aircraft. td , to in perfect condition. II7VAC _ MA G,ENESEE STREEDEPT. 4 150V 4 BUFFALO RADIO SUPPLY BUFFALO 3,2N1 9C sz SEPTEMBER, 1948 aa) Itadio-EiIcctronic I:ircuita. CODE OSCILLATOR Here is a multivibrator oscillator RADIO -CRAFT welcomes new and orig- 00.71 which can be used for code practice and inal radio or electronic circuits. Hook- as a signal source for testing amplifiers. ups which show no advance on or M ES-U OpN GE éoN N 00% The key is connected in series with the advantages over previously published 6SC7 cathode. A phone jack is provided St circuits are not interesting to our read- ua a for headphone output and a pin jack takes a test lead. ers. Send in your latest hookups and receive a 1 -year subscription to RADIO. i `S 6SC7 CRAFT or $3.50 for each contribution 01sASOOK VOL CpNT accepted. Pencil diagrams -with short .001 'A01 47K >< 47K ' = TEST LEAD I fE descriptions of the circuit -are ac- a01+ r,, OI ceptable if clearly drawn on a good - IMEG ----o- sized sheet of paper. 4701( 7 SELENIUM RECT i--- ° KEY FR _ 4.7K/2W 2A. TI PILOT .e . dicator leads to the a.v.c. line and the ° II - aT2 set's ground. Adjust the trimmers for 1I7VAC aq,! maximum closure of the shadow on the PRICE 6E5 screen. ' If the eye closes too soon, turn the A selenium rectifier is used. T2 fur- at n,tr,n- nishes 6.3 volts for the 6SC7 filament potentiometer to close the grid switch or gto, "sore y. con's . Ohioan, add 3, State Sales Tax. and the pilot light. It is also connected and adjust it for the desired shadow to TI, another filament transformer, angle. which is operated in reverse to produce TED R. PARKS, 117 volts for the rectifier. This isolates Salem, Ore. ASigrsálette the power supply from the a.c. line, a MULTI -FREQUENCY GENERATOR good idea in view of the fact that the ex- In radio service work, time means money. Locate trouble faster, handle a much greater volume of posed metal of the key would otherwise work with the SIGNALETT E. As a trouble shooting tool. SIGNALETTE has no equal. Merely plug be connected directly to one side of the 110 V. ACDC line, start at speaker end of cir- line. cuit and trace back. stage by stage. listening in set's speaker. Generates RF. IF and AUDIO Frequencies. The frequency can be controlled with- 2500 cycles to 20 Megacycles. Also used for checks on Sensitivity, Gain. Peaking, Shielding. Tube in limits by the 1- megohm potentiometer. testing. Wt. 13 oz. Fits pocket et- tool kit. See at your dist. or order direct. The oscillator will not chirp, even with INSTRUMENT very fast keying. C'lsppardLINCORATORY, W. A. M. WOOD, VE4MW, Winnipeg, DEPT. C. 1125 BANK STREET Canada CINCINNATI 14. OHIO L Qualified Jobbers write, wire for details. a. CODE OSCILLATOR

This 1 -tulle code oscillator Rive loud- T.R.F. TUNER speaker output. T may be almost any The diagram shows a high fidelity center -tapped output transformer. Ch t.r.f. tuner described originally in Radio can be any filter choke or it may be re- and Hobbies, an Australian magazine. placed by a resistor (experiment for Standard coils are used with a 3 -gang value). 365 -µµf tuning capacitor. Since the key contacts are connected To align the tuner, tune in a station to the high voltage use insulation or one toward the high end of the band (or a of the surplus keys which are entirely signal from a test oscillator) and ad- enclosed. just trimmers for maximum output. If a The potentiometer will vary the tone commercial calibrated dial is being used, (HJ(1( as well as the volume. peak the trimmers and note the dial Fill WOODROW V. RYDER, calibration. If it is off, move the dial Red Hook, N. Y. slightly toward the correct mark and uF BUYS! realign. Keep this up until peak output KEY occurs at the proper marking. As a ALU) s tILI.VI. check on the trimmer settings tune to '.ION PARrl tJM:! /ADDRESS one side of the carrier and peak them tN'IP tOMMUNIC/L on the noise. If iron -core coils are used, tuRf AICORDCRt, they can be peaked on a frequency 'EtORft CHANGERS A MUST for all low- it st IN1fPUM[N7S Service Dealers station, then the trimmers rechecked on IduiS AMATEUR Amateurs EQUIP 7 (NAN(ELLOR Experimenters 4 pAUiO: NAROWARE Induste:als 117VAC /DC TUNING CONOS EACH 365µµf GANGED r(tNR.I(AL ROOKS Institutions, Go ment 6U7-G (2) 6J7-G Agencies SET ALIGNMENT RADIONIC EQUIPMENT COMPANY A 6E5 electron -ray tube can be used 170 NASSAU ST., NEW YORK 7, N.Y. as an indicator for aligning sets with ANT t,iban. theotre Foirant a.v.c. lel. WOrth 1.0421 Coble "CHAN tOR A unit like the one shown in the dia- RADIONIC EQUIPMENT CO.. Dept. 108 gram can be built in a small metal box. .05 - 47K 170 Nassau Street, New York 7. N. Y. Use a toggle switch in the transformer ( Send at once your free atalup S. supplements and liar - gain lists as publi.hed -listing praluets of leading primary circuit. The grid switch is on manufacturers of radio- eïm'tt noir parts and equipment. the 3- megohm volume control. Adjust the on 50,000 -ohm bleeder NAME tap the until 10K. CAF CUT the power-supply output is 250 volts. P.O. SOX or STREET To align a receiver, supply it with an si 1- TOWN STATE unmodulated signal and connect the in- e +2O50V pe aU RADIO -CRAFT for Radio-Electronic Circuits ¡83 a high- frequency station. Very little tracking trouble will be had. The 6J7 is an infinite -impedance detector. The tube operates on a non -linear tll the "Know HoW portion of its Ea-Ip curve, as in a plate Of detector, but output is taken from the cathode circuit. This gives negative RADIO feedback reducing distortion. MITO REPAIR handy training book .. RADIO -CONTROL UNIT in one for only $1.50 The transmitter for this radio- control unit uses the spark -gap discharge principle. It is shown in Fig. 1. An old Ford TWICE AS EASY spark coil steps up the voltage from a MAKES THE WORK 6 -volt battery to a high value; the high Covers all auto radio types from mid- 1930's voltage discharges as a spark across the to the present, including mobile FM receivers between the 1- Ilere- ritten by a practical alts radio expert of 20 gars ' standing -is just gap two inch -diameter the data y trodti to repair car ratites faster. easier. and a lot more profitably! A. brass balls. These can be salvaged from L. Ilmlbut! SERVICING THE MODERN CAR RADIO la the only book devoted solely In this fast -growing service field. Explains every detail of the work an old brass bedstead or curtain -rod clearly-amid tolls this elf with 222 Illustrations anti over 500 circuit diagrams cov- assemblies. ering specific service details on every type of automotive radio in use: COMPLETE THEORY- TEST -INSTALLATION- rLpOODD ANTENNA -AND SERVICE DATA It Is the only single boll( that include; lelllla tllnulltin4: contains pertinent in- 0 001 needed data ber trau.Wnli a go.l home- tonnai i,.r on Fil receivers: tells homy to radio sl.ti,mali tes,. a car radio ex- get hosines,. Ilmv to deal with auto 6V DC FORD SPARK COIL pert. I)t .. . Its rit Toits. Expia ins auto- radia alaise customers. and how to set motive electrical unit:. their function and up your shop, test bench. etc.. for max - o efieet on radio performance. Tells hrnv Iulula iMclency in this specialized, fast- to install ear radins pral.elly and why growing Held. In short. SEIIVICINO BRASS BALLS I/16 "APART SERVICING they should v be lu -n.Oed that w v. Pi o- Tl IE MODERN CAR RADIO combles Odes I mit diagrams on hundreds of at your fingertips a complete, easily un- of Fig. 1-Activator of the radio control tube. popular u.lrls aand I mtains ample data derstosl encyclopedia facts. methods lo lait Ilunl do a good jolt on sets for and data for operating complete auto THE MODERN wIllIt ill.tgranis are not readily avail- Tolle service station. Use FREE Fig. 2 is the receiver diagram. The attic. Gives full details on Droner an- EXAMINATION couPat todayl antenna is a length of copper tubing CAR RADIO bent to form almost a complete circle 12 OPPORTUNITY OF A LIFETIME inches in diameter. A 1.5 -volt flashlight BY A. L. HLRLISI l :I stn Radio Service for alert servicemen, says A. A. Ghirardi battery biases the 2051 gas tetrode. Manager and Design Take this advice from A. A. Ghirardi, author of When the signal is picked up, the tube is Consultant famous radio service books and articles! triggered and the relay is energized. I have read llurIbul's SERVICING THE MOD- Second Edition, 702 ERN CAR RADIO front corer to corer. I sincerely represents an opportunity no wide awake x 11, 222 il- believe it COPPER TUBING pages, 8% errli,emau can afford to miss. For nowhere in radio lustrations, over 500 dia- today is flier.' a better chance to build busi- grams, $7.5(1. 71.8a. increase profits, step ahead of compe- 2051 5Res SENSITIVE RELAY tition! Practical, easily un- OVER 9,000,000 CAR RADIOS! 11 derstood data on think of Approximatell, nr out TO CANTS Entering the Car Radio "Just it! DEVICE serf every tau radio receivers in use today are Field is increasing Principal Differences be- car radios -and this percentage tween and Honte every day. Good automotive radio servicemen III 1111 Mobile a gold -1 Radios are scare. -and Mr. Hurlbut vices +45-625i- - Automobile Antennas mine of information you need to cash in on Antenna Input Circuits this profitable business. "' The Power Supply Il !VAC 0001 Typical Circuit Features The Automotive Electrical Fig. 2- Control tube is a small thyratron. System Setting Up the Car Radio Murray RITI Snot,. Inc. (Division of Rinehart & Co.) Service Station Dept. RC -98. 232 Madison Aye., New York 16. N. Y. Anything can be controlled if it is Installing the Car Set connected to the relay contacts. Control Installing the Antenna stud nie then Second Edition of llurlbnt's S.rrvidug the Modern Car Radio Loudspeaker Installation t,,r to days' examination o .Ipprmal, In In days I will send $7.50. plus few is reliable, however, only if the trans- a postage. or 11 book postpaid. Vixaage Paid on rash orders; /Mine re- Interference U.S. mitter and receiver are no more than 12 Servicing Procedure I (Books sent on approval in only. Price outside nU.S., Vibrator Maintenance s.unririu-ge.n, pu.mait'.l feet apart. I use the gadget to open my Servicing the Loud speaker garage doors without getting out of the Car Radio Alignment Name car. The transmitter creates radio inter- Push -button Tuning Address ference for a greater distance so should and over 500 y (.ale) & St ¡to be operated as little as possible. specific car radio MELVIN YOUNGMAN, Oak Park, Ill. circuit diagrams! O c t opal i o n NOVEL REFLEX CIRCUIT In the conventional reflex amplifier a resistor is connected between B -plus and the plate as an audio load. This causes a loss of plate voltage and a reduction in r.f. amplification. The reflex circuit shown in the dia- TERRIFIC VALUE - gram avoids this by taking the audio PORTABLE ELECTRIC DRILL (Sold at less than established factory price so we cannot mention brand name) Only $19.95 minipiled with n4" .IatM.s Geared Chuck and Key. IF Net a intermittent duly drill. toil a f1111 .sizt rugged tool. Olin, I. a, tut West type switch. natural grip handle, and balance like a sir- Precision cut gears -turbine type roiling blower -extra log brushes. .0015 No ,.tailing under heaviest pressor: because or powerful 110 Volt AC DC Be motor and multiple loll thrust hearing. Other hearings self- alignlog lifetime Irhrleatlne Chrysler 01111e type. Made for toughest year iu and year -Inn service In Plant or on construction Jobs. .005 100 AUDIO OUT Aidtai ng perpetual factory co wantt e, a al of a lifetime of troublefree u -I . deposit on t'.D. It 's.II rñni sit tenoned prepaid within Ove a days. FRott )it 1---Se .003 BUFFALO RADIO SUPPLY 219 -221 GENESEE STREET BUFFALO 3. N. V. DEPT. 9C SEPTEMBER. 1948 81 Radio-Electronic Circuits

from across the screen dropping resis- To check continuity, set S2 at CHARGE, ONLY $89'50 IS THE COSTI, tor, leaving the plate connected to B -plus close Si, and use the test terminals. To through the i.f. transformer, just as in check for presence of a voltage, open Sl, ordinary non -reflex circuits. set S2 at DISCHARGE, and watch for the The arrangement can be adapted to neon lamp to glow. almost any tube used in a reflex receiver. Since this instrument is connected di- R. A. CUNNINGHAM, rect to the line, it must be built into a Newport, Ky. box and only the leads from the neon (The idea is interesting. Gain may be tube and 100,000 -ohm resistor brought lower, but with r.f. filtering, the audio out. I. L. FRIEDMAN, could be carried through two stages. Editor) - Brooklyn, N. Y.

1 -TUBE TRANSMITTER AUTOTRANSFORMER Here is a 1 -tube 80- or 40 -meter trans- A war surplus size 5 synchro makes mitter which is as simple to build and an excellent adjustable autotransformer when connected as shown. With an input for the SENSATIONAL-NEW -IMPROVED of 117 volts at 60 cycles, output can be 10 INCH varied smoothly from 0 -80 volts or from 23 -175 volts by turning the rotor. Five TELEVISION hundred watts can be handled intermit- KIT tently or 150 watts continuously. A less tubes friction lock on the shaft or a worm - Complete with 13 channel tuner, all parts and gear drive be easy step-by-step following instruction. and should used. schematics. $89.50 leas tubes Kit complete with all tubes $149.50 Cost of cabinet $25.00 Using the new 13 CHANNEL TUNER which is pro- wired and factory aligned for the entire television spectrum. The kit builder merely Insuails this unit into hit chassis and makes three connections. Contains 3 an 1t.F. stage, oscillator and mixer. It is extremely S2 small and compact. Using new I.F. rods which pro- OUTPUT vide maximum gain and plot ure dinniliout. Sound SW OPEN 0 -80V SW CLOSED 23 -175V reception Is high quality F.M. for cotnplcle listen - lug pleasure. This autotransformer will be found operate as SAME TELEVISION KIT-7 INCH. complete less the usual 6L6 oscillator but tubes $59.50; complete with all tubes 899.50 especially useful in the service shop for which gives nearly 20 watts output. boosting IMMEDIATE DELIVERY FROM STOCK line voltage to intermittent sets Standard coils for 80 or 40 meters can to hasten the breakdown of the inter- be used for L and crystals for either ELECTRONIC & mittent L¢.tiwpD.l(Ìcul component. band may be used. Operate straight - INSTRUMENT CO. G. A. DIxoN, through, as doubling lowers the effici- Dept. RC9 42 WARREN ST. N. Y. 7, N. Y. San Pedro, Calif. ency. Plug a 150 -ma meter into the keying pack for tuning. Adjust antenna NEON TESTER coupling for a maximum current of be- BUILD from KITS This simple tester will give a reliable tween 80 and 90 ma. YOU CAN MAKE MODERN RADIOS report on the condition of capacitors and ROBERT FINK, AND TEST SETS YOURSELF! IDEAL FOR SCHOOLS AND HOBBYISTS can be used for checking faulty receiv- Cleveland, Ohio MULTITESTER ers. KIT M.3C Place a capacitor across the test ter- A.C. -D.C. AMPLIFIER 1000 ohms per volt minals. Close Si, then set S2 to CHARGE. Economy of is sensitivity cost combined with good Ohms and AC /OC volts A good capacitor will charge and this quality reproduction in this general - Versatile. compact. 467x3'. will be indicated by a flash of the neon purpose a.c.d.c. amplifier. 3 tx' round uu; er. EnVlln-s following ranges: Volts AC lamp. Open Si and set S2 to DISCHARGE. The first two stages provide sufficient or DC 11i5/50/150/590/1500; Milliamperes DC 0/5 ^! /- SELENIUM RECT amplification for a phono pickup or a TAU: Ohms O/2000/20,0001- orCHARGE 200.000. Available In bench 1 aS2 microphone. A .003 -µf condenser from -..4 marl or portable case. ---o 100 the control grid of the 6SJ7 to ground Complete n1111 !III pl i fled Instructions. 117V AC VACUUM TUBE SI 116 'DISCHARGE filters out any needle scratch that may c be present when records are played VOLTMETER

KiT 012 10011 1/25W NEON e51 through the amplifier. Decoupling is pro- ASHY bridge type volt. circuit. vided by a 25,000 -ohm resistor and 8 -Itf A-5ter 00 m amos DC, I/al. squ`ere meter. TEST TERMINALS condenser in the plate lead of the input Output meter - 60O ohm circuit, 1 ini. tubes. LEON watt re level. A good capacitor will discharge and the POLLARD, For high frequency EM will Dorchester, Mass. 1 TV. I1 Iegohms lamp flash again. DC. 6.5 megnhma AC resistance. 0/1111 to lotto 6SJ7 .02/600V 65F5 .05 /600V 25L6 In 5 ranges. Linear AC i. DC volts 0 -10011 volts, 5 3 5 orales. OHO balanced 500K 2.51in OUT. TR.PRI. linear AC roomier. ppdiode resistor. OxOxt . Probe for high INPUT frequency FM and TV a 500K Wavailableith completeexinstructione. KIT S-5 DELUXE PLASTIC TABLE SUPERSET 2526 2516 6SF56SJ7 A STREAMLINED DELIGHT Modern e oit aulbin Mapic Ltnp" Powerful Alnico speaker Improved auperhet with trodt.in 100g and Alnico met speaker! Ea,V.tune airplane dial. 12067 IF. 120A7 converter. 12607 AC /DC 1kt. -1 st Aul' in.SOLO Power CHOKE output, 3525 rectifier Beautiful banellte cabinet. Simplified Instructions for This general- purpose amplifier circuit may be 20T I50V 20 With a These and many other models available at your adapted to a number of purposes. local jobber or directlyrefrom us. suitable line cord, various a.c. -d.c. tube types Write for Catalog K 25Z6 may be used. For high -output crystal pickups 1 ÿ RADIO KITS COMPANY 117V 01-.1/600V QpSW an input might be mode direct to the 6SFS. 120 Cedar Street, Now York 6, N. Y. AC/DC RADIO -CRAFT for - Miscellany aa SMALLEST B- BATTERY 1 fTHE NEW MODEL 247 TU BE TESTER Checks octals, loctals, bantam jr. peanuts, television miniatures, magic eye, hearing aids, thyra- trons, the new type H.F. miniatures, etc. FEATURES: * A ly designed element selector reduces the possthi WYlY of obsolescencemu. to .m Absolute mini- * when checkarg Diode. Triode and Pentode errions of mull i- pulsnse tubes. sert i nos r he tested individually. A special naaling circuit all, W% each ie tested as i t w rs r a separate elope * The Model 24: p .video super ssensitive metet hod of checking for Courtesy Obn Induct rivs Ltd. horts ant up t r 5 Meg. ohms between any and all of the Individual cells of new B- battery interlock terminals. * One f the oat mpormnt Im. automatically to make electrical connections, pr.rcen enta, e believe. In the fart that the 4 position fast -art ben snap eliminating 91% of soldering. Electrodes are switches numbered In setup xallith the s -Ibrd R. Mt. b thin carbon -coated zinc plates which fit the t nering.a m to 1 the element log - No. 7 square windows seen in center of sections. of a tub Mntinatis under 1 7 is acrd for that t. ONLY Mobile communication needs have grown so much that the FCC last month proposed to separate the present auto- 19" mobile and truck telephone service into three new classes, each with its own THE NEW MODEL 257 frequency band. The three classes would be: land transportation-busses, trucks, trains, and taxicabs; domestic public service - ELECTRONIC common -carrier service for the general public; and industrial service -delivery and pickup trucks, doctors' cars, and ambulances. ANALYZER The proposed new services consolidate THE MOST COMPLETE MULTI- RANGE, MULTI -SERVICE UNIT EVER DESIGNED ! ! a number of present services, reduce overlap between them, and increase the ITS A HIGH FREQUENCY A.C. number of businesses eligible to use VACUUM TUBE VOLTMETER

radio. (A true A.C. V.T.V.M. employing a I -A3 Diode which together ai h a resistant', capacity network is built into a specially de. signed Polystyrene High Frequency Probe., Rabic Dfar5 Ago ITS A D.C. VACUUM TUBE VOLTMETER iln Qìrrllgba(k PublaattonS (At 11 mecohms inout resistanco.) HUGO GERNSBACK IT'S A CAPACITY METER Founder IT'S A Ra.9CTANCE METER Modern Eleetries 1909 Electrical Experimenter 1913 IT'S AN INDUCTANCE Radio News 1919 METER Science it Invention 1920 Radio -Craft 1929 ITS A DECIBEL METER Short -Wave Craft 1930 Wireless Association N America 1909 ITS A 1000 OHMS PER VOLT V.O.M. Some of the I ibraries in the country still hay M D.C. Voltages (at 1.000 optes of ELECTRICAL EXPERIMENTER on Cl, to ohms per volt) up to 3.0v3 volts. readers. nitrated A.C. Voltages (at 1 .pn0 ohms per volt) up to 3.000 Volts. D.C. car - In September 1914 rent up to 1s amperes. Resistance UP to 1.000 s. ELECTRICAL EXPERIMENTER r The Model 297 ones housed in a beautiful hand. rubbed oat cabinet complete ws. test leads 50 V.T.V.M. plebes and instructions. Size: 812-. $ How to use the "Electro" Loose Coup- ' 10W.514". NET ler Sixty, yes Sixty- ..palan ranges an provided by this most vermeil. unit aver designed. Improved Buzzer Transmitter by Specifications Frank H. Broome A.C. V.T.V.M. VOLTS: (Input resistance- 750/1500 tIilO V,,i(o- Aerial Mast Construction by Charles 10 megohms shunted by 8 micromicrofarads. D.C. CURRENT: 0 to 3/15/30/75/150/300 / Freg. Range --50 cycles to 500 Megacycles.) 750 Ma. 0 to 3,15 Amperes. RESISTANCE: Fitzgerald 0 to 3 15 30 75 -150 300 Volts. D.C. V.T.- 0 to 1.00010,000/100,000 Ohms: 0 to 1!10' The Sayville, L. I., Wireless Station V.M. VOLTS: IAt 11 Megohms Input Re- 1.000 Meguhma. CAPACITY: In MFDI sistanc'l 0 to 3 15'30.75.150 7110'750,1500/ .0005-.2 .1)5 -20 .5 -200. REACTANCE: Adjustable Condenser and 'Phone 3000 Volts. D.C. VOLTS: tA (.000 Ohms 10 to 5M 1Ohms) 100 -50M IOhmsl:.OI Switch by Frank H. Broome Per Volt) 0 to 3/15/30. 100,750/ ( Megohms). INDUCTANCE: Ihn Henries) -140 14.000. DECIBELS: good 1500'3000 Volts. A.C. VOLTS "\t 1.000 .035 -14 .35- 35- A Mineral Detector by Ralph Ohms Per Volt) 0 to 1 -:u :300/ -10 to +18 +10 to +38 +30 to +58. Humphrey Portable Wireless Station Tower 20'' Deposit Required On All C.O.D. Orders Automatic Tikker Receiver New Pickard Crystal Detector Stand I MOSS ELECTRONIC DISTRIBUTING CO. Firing a Revolver by Radio Waves DEPT. RC 9 229 FULTON STREET NEW YORK 7, N. Y., 200 Volt Radio Transformer SEPTEMBER, 1948 Misccllsmy

Scale models of tele- RADIO TUBES vision studios simplify For immediate shipment planning. Transmitter is at rear, control console

R.M.A. Guaranteed in foreground, a n d Individually Sealed Cartons cameras at right in this picture. General GT Types Miniature Types Electric emplcyees 6K6GT .40 1S5 .50 Jean Thater and Jane 6KSGT .46 1T4 .55 Reid inspect the model. 6V6GT .46 1R5 .55 6SA7GT .46 3S4 .55 6SJ7GT .46 6BA6 .50 6SK7GT .46 6BE6 .50 SPARK PLUG REDUCES INTERFERENCE 6SQ7GT .46 6AT6 .42 NOW that FM and television are gain- urinal and one side of the spark gap. ing wide acceptance, high-frequen- The resistor has a damping effect. 6X5GT .40 12BA6 .50 cy noise from automobile engines is be- The damping reduces the duration of 12SA7GT .46 1213E6 .50 coming an important source of interfer- the oscillations and also restricts the ence. A new spark plug developed by oscillation to lower frequencies. The 12SQ7GT .46 12AT6 .42 the Electric Auto -Lite Company con- oscillation peaks are damped so effec- 12SK7GT .46 35 W4 .42 tains a built -in resistor which is said tively that radiation is kept below 35 to reduce noise radiation considerably. millivolts per meter from 540 kc to 12SJ7GT .46 50B5 .55 The discharge at the gap of a spark 150 me at 50 feet from the engine. 35L6GT .40 plug consists of high- voltage, high-am- In addition to suppressing interfer- perage damped oscillations of short du- ence the new plug is said to reduce en- 35Z5GT .32 ration followed by a non -oscillating dis- gine misfiring, help lubrication, and 50L6GT 46 chargé of much greater duration. The lengthen the life of pistons, rings, and 25 °o DEPOSIT REQUIRED ON C.O.D. -2 °ó C.O.D. oscillatory discharge generates high cylinder walls. 10o. DISCOUNT ON LOTS OF 50 OR MORE frequencies of large amplitude. RAVAC ELECTRONICS CORP. These cause serious 432 Fourth Avenue radio interference. New York 16, N. Y. As the cutaway photograph shows, the new plug has a MASCO SERVICE KIT built -in 10,000 -ohm ceramic bonded Kit includes assortment of: I pr. head -phones or lip S Volume Controls. carbon resistor be- mike. 10 wire Wound Resistors, 100 Resistors, !z and 1- 10 & 25 watt. tween the11hot "ter- watt. 25 Connectors. Plugs, Ties 100 Condensers. paper. 10 lacks (Phone) & Tip. mica. electrolytic & can. 12 Padder Condensers. 10 Switches. Toggle, 12 Terminal Boards. BETATRONS IN FIGHT AGAINST CANCER Gang & Rotary. 25 Ceramic Insulators. 100 lt. Spaghetti, vari 2 Panel Lights (I neon). Betatrons will be used next year for their maximum effect at the surface. ous sizes. I Screw Driver. 12 Knobs, round and I Tube Puller. cancer treatment for the first time, The betatron produces its X -rays by bar. 2 Allen Wrenches. 2 lbs. Hookup wire. 2 Panel Fuse Holders. Science Service reported recently. The bombarding a platinum target with 20 Fuses. 4 Binding Post Strip, 10 Tube Sockets. and many other valu- betatrons will produce 20- million -volt high -energy electrons. able items. I lb. Hardwe (screws, X -rays 20 When it was invented, its originator, nuts, lugs, etc.). times more powerful than Bought individually would ost S9 those used heretofore. These X -rays can Prof. Donald W. Kerst of the Univer- 560.00 -Now! Yours for nIY 95 rgmplet.. be concentrated on a point deep inside sity of Illinois, pointed out its cancer - PHOTO -CELL AMPLIFIER body in this I, the patient's with reduced danger fighting possibilities. Research t)f damage at the point where the rays direction was delayed, however, by the ii tnter the body. Lower -voltage rays have war.

Ittiu-,. $9.95 PARABOLIC REFLECTORS 15' spun aluminum. Alzak Iln. for 1200 Me. l'p. 2 for V$3.00 Vibrator -Sy-n. 2 Volt T picota for G.E. Portables. Replace, 1X -530. 2 for $2.49 Microphone-T -24 Carbon with Push Switch and ('able. New .79 ;IS Substitution .n.l rinn Scope Tubes ]1l1'I 't"I.) new In ear $2.29ry by sots. Each Y Signa eSubstit Servicing tht-AM A vodoSIe 31(r1 Wrae Today roblems, s -s tells HOW - in The Simple, -s AMERICAN SALES CO. and adjustment to simple, direct language. Not Worpotcbose 1311 W. 47th St. Chicago 9, III. alignment inQ complex t ealro equipment New 9th edition now off the press. Wo - nonoobs'lestcEquipment 100 pages of valuable information. Universal B E.., ploys only Available from all leading rodio parts and nearly ready ...the new, bigger, distributors or directly from factory Its ever of equipment for ÌW9ICataloa at only 40c per copy. For 'priority" delivery. reserve your free COPY of this; helpful. huyinK guide now. write: a Inc. 91 -27 Horace Harding Blvd., Elmhurst 4, N. Y. on tinny your "RECISION APPARATUS COMPANY, address. Ìt rd. WALTER ASHE RADIO CO. 1125 PINE ST. ST. LOUIS 1, MO. RADIO -CRAFT for FA11 117 FM STATION LIST response to our call for FM scouts THEhas been extremely good. Mail has 35 years -the been arriving in large quantities and * For over the letters have all been interesting. We finest in electrical and expect that the reports from RADIO - electronic instruments. CRAFT readers will be of definite importance to those who are gathering information about FM propagation on the 100 -mc band because they upset any theories which might still exist about line -of -sight reception. Sidney Padrick, of Avenal, Califor- nia, for example, reports reception of KIMV, Hutchinson, Kansas; WKY -FM and KOCY -FM, Oklahoma City, Okla- homa; and KCMC -FM, Texarkana, Texas, among others. Signals were strong -and all the stations were from TUBE 1,200 to 1,400 miles away! This was no laboratory experiment; a Meissner TESTERS tuner was used with a Ward antenna. Although the antenna array included a elaex tie eX. be'cta.! reflector, rotating it had no effect. %' Hayes Lyon, located in Austin, Texas, Television receivers MUST have reports hearing KNX -FM, Hollywood, good tubes. You can depend on California, and WNDB, Daytona Beach, Florida, 1,200 and 1,000 miles HICKOK Tube Testers to reject away respectively. He used a Scott all weak tubes quickly and receiver with the antenna built into the accurately. cabinet. The signals faded in and out, Exclusive features that have put HICKOK being absolutely clear and noiseless at their best. Tube Testers far in the lead are: Another Scott owner. R. J. Marks of 1. Tests FUTURE life of tubes! Norfolk, Virginia, reports reception of 533 DM (illustrated above) KOCY a -FM, Oklahoma City, distance Mutual Conduct- 2. Tests all tubes ACCURATELY! of about 1,175 miles. Dynamic John A. Beckman of Jacksonville, ance Tube Tester 3. Reads micromhos DIRECTLY -the Florida, reports frequent reception of The popular and effective only true test of a tube! WMIN -FM, St. Paul, Minnesota. He selling -aid model, designed 4. Tests tubes for gas content -more uses a Hallicrafters SX --13 with a half - for quick customer -convincing, wave doublet antenna cut for the 40- counter demonstration and important now than ever before! meter amateur hand. Reception over test. Incorporates the new this 1,190 -mile path is best after 6 pm. HICKOK test feature that The signal fades in and out at 5- to 10- foretells future tube life. The HICKOK line of Tube Testers is COM- minute intervals. Large 9" scale, reading PLETE. They are available in portable, counter Several 1,000 -mile reports came in. directly in micromhos, also and display cases. Also with self -contained, Roger E. Hammer of Elkton, Virginia, indicates "GOOD ", " ?" and high sensitivity multimeters and with specially received WFAA and KIXL in Dallas, "REPLACE ". 17" x 263/a" x designed professional features. Texas, with a Westinghouse receiver 11". 110-130 VAC. HICKOK has long been the choice of leading and a folded dipole and reflector 30 feet technicians and electronic manufacturers the above ground. Charles E. Brown in world over. West Palm Beach, Florida, heard See your jobber or write for free catalog. WFUV in New York City on a hone - THE built receiver with an r.f. stage and three i.f. amplifiers. 'ELECTRICAL INSTRUMENT COMPANY Reception of WMIN -FM, St. Paul, 10531 DUPONT AVENUE CLEVELAND 8, OHIO Minnesota, was reported by S. B. Knapp of Baton Rouge, Louisiana. Mr. Knapp made a wire recording of the programs to prove his DX report. Harold R. Vogt of Mountain Lake, Minnesota, writes that he heard WTPS- FM in New Orleans, Louisiana, with SCR -274N COMMAND SET plenty of volume for a few minutes, after which the station faded out. The _ r The greatest radio equipment value in history owner in of Schmitz Radio Staples, A mountain of valuable equipment that includes 3 receivers Minnesota, reports reception of WMAS- that use plug -in coils. and consequently can be changed FM in Springfield, Massachusetts. wwto any frequencies desired without conversion. Also in- There were several long- distance re- J cluded are two Tuning Control Boxes; I Antenna Coupling ports on old -band (42- 50-mc) FM. The riot'.i Bon four 28V. Dynamotors (easily converted to I10V. ordinary skip -effect is known to be operation); two 40 -Watt Transmitters including crystals, present on this band, which was one of ' Ilk and Preamplifier and Modulator. 29 tubes supplied in all. I a limited quantity available, so get your order in the reasons for going over to the high Only P} Ili fast. Removed from unused aircraft and in guaranteed band after the war. These reports were, electrical condition. A super value at $34.95, including therefore, excluded from our discussion. crank type tuning knobs for receivers. We hope that all RADIO -CRAFT readers BUFFALO RADIO SUPPLY 219 -221 GENESEE STREET who own FM sets will continue to act as BUFFALO 3, N. Y. DEPT. SC FM scouts and send in their reports on SEPTEMBER. 1948 any record long- distance FM reception. rounding Alums um /ear box 1818:7 that contains two power- the receiving location -hilly, ful electric motos and two matched gear (rains. 62 When you write please include all the flat, etc.; signal strength of stations re- gears n all varying in size from Sk to 4 Inches In (Barnet r. This unit Is readily converted to rotate information you can think of. Especially ceived, time of day, and giving us air- beam ntenna or any other similar use $3.00 important are: type of set; description line distance between your location and TUBES -All types in stork. 6OSF on tan all tubes if ordered 0t lots of IS or ue e. of antenna; the type of country sur- the transmitter. AUTOTRANSFORMERS-Ntrps up 1111v. or steps .Iovn 226c to Hot-31.95. FREQUENCY FREQUENCY FIL. 6.3v. 211 Amps. Universal TRANSF.: -31.98: (MC) CALL LOCATION (MC) CALL ttnt pelt Trans. N Watt- 8k: IS Wall -$1.29: 311 LOCATION 1Vatt- $1.69. AUDIO TRANSFORMERS: S. ]'late to I;rid. 3:1 -7k: S. Platt- to I'.1'. (]rids --79e: lie.ivy Duty (lass All or It. P.1'. puts- $1.49: 44.1 W2XMN Alpine, N. J. 93.7 WCSI Columbus, Ind. 89.1 WHSF Midget Output for AC-UC acts -69e: MIKEI TRANS Wausau, Wis. 93.7 WCSI Franklin, Ind. FORMER for T -17 Shure microphone. similar to 89.5 WSUU So. Orange, N. J. 93.7 WDRC-FM Hartford, Conn. is type Stanc SB or mike to FTC t : - $2.00. h pit 89.9 KCRW Santa Monica, Calif. 93.7 WFBC-FM Greenville, lime or (grin- áI.95. S. C. 89.9 WCTF Cnicago, Ill. 93.7 WKJF Pittsburgh, Pa. POWER TRANSFORMERS-Ball shell type. 1111V, 89.9 WHKW Chilton, Wis. 93.7 WLAWFM Lawrence, Mass. ,al ty. Cenlett:toed 11V at iudlug. Sperity either 3.5 90.1 KOKH Oklahoma City, Okla. 93.7 WSGN-FM Birmingham, Ala. n 6.3V filament when ordering. 90.1 KRVM Eugene, Ore. 93.9 KSPI-FM Stillwater, Okla. For 4 -5 tithe set. -650V. 4O11A. 5V 6 2.5 or 90.1 WABE Atlanta, 1.3V $1.49 Ga. 93.9 WCOU-FM Lewiston, Me. ]For 5 -6 tube sets-650V. 45MA. SV & 2.5 0 90.3 WBOE Cleveland. Ohio 93.9 WNYC-FM New York, N. Y. 11.'1V ... 1.75 ...... r 90.3 WSHS Floral Park, N. Y. 93.9 WRC-FM Washington, D. C. For 6 -7 tube sets 675V. 50MA. 5V & 2.5 u 90.5 KWGS-FM 11.3V ...... r 1.90 Tulsa, Okla. 93.9 WROW-FM Albany, N. Y. F'or 7.8 tube sets -700V, 70MA. 51/ A 6.:1 0 90.5 WKAR-FM E. Lansing, Mich. 94. KERN-FM Bakersfield, Calif. 0 2.5V t 2.35 90.7 WI UV New York, For 741 tube sets -700V, 7OMA. 5V & 0.3 ;25 N. Y. 94. KLZ-FM Denver, Colo. 90.7 WHAD cycle, 3.60 Delafield, Wis. 94. WEAU-FM Eau Claire, Wis. For 8 -0 tube sets -700V -13031A. 5V 3A. 2.5V- 90.9 KOKU Norman, 3.5A, 2.5 -10.5A 2.85 Okla. 94. WEMP-FM Milwaukee, Wis. i'or 0 -11 tube sets-700V. 5V & 6.3V -4A 2.85 90.9 W DTR Detroit, Mich. 94. WGST-FM Atlanta, For 0 -15 li sets -600V. 15OMA. 5V A 6.3V 2.95 Ga. tuo 90.9 WEHR State College, Pa. 94. WHBCFM Canton, Ohio TURULAR WV 600 -.001. .002. 90.9 WFIU Bloomington, Ind. 94. WIBGFM Philadelphia, 005 -Sc; 01. .05 -9c; 1 -10e; .25-23e; .5 -35e: Pa. ELECTROLYTIC!: Kmfd 200v -20e; lomfd 35v -20c: 91.1 WBGO Newark, N. J. 94. WKOK-FM Sunbury, Pa. 91.3 KCVN Stockton, 30mfd 150v -23e; 20/20m14 150V 35e: 30/20 150v Calif. 94. WMIX-FM Mt. Vernon, III. Sae; 5 , fd 150v-50v-43e: gmfd 475v -34e: 16mfa (í50v 91.3 WBKY Lexington, Ky. c OIL CONDENSERS: 2mfd 94. WREN-FM Topeka, Kans. -6Se: amid 600v -49e; 91.3 Ames, 11111v -29e: 3% .1mfd 600v -39e. WOIFM Iowa 94.3 WBEC-FM Pittsfield, Mass. 91.3 WTDS Toledo, These PM speakers aro the finest that are Ohio 94.3 WJLK-FM Asbury Par,, N. available. have uverside V J. All heavy Alnico magnets. 91.3 WWCH W. Chester, Pa. 94.3 WOCB-FM West Yarmouth, 91.5 KSLH St. Louis, Mass. 3t/a. $1.15 6 for $6.60 Mo. 94.5 KGKL-FM San Angelo, Texas 91.5 KUSC Los Angeles, 4^ $1.15 6 for $6.60 Calif. 94.5 KWOC-FM Poplar 13104, 91.5 Chicago, Mo. Rae (oval) $1.95 6 for 511.40 WBEZ III. 94.5 WHDM-FM Boston Mass. 5' $1.10 10 for $9.50 91.5 WHA-FM Madison. Wis. 94.5 Columbia, New WIS-FM S. C. 6^ $1.90 6 for $8.70 91.5 WNYE York, N. Y. 94.5 WMLL Evansville, Ind. 91.5 WPTL Providence 7" (Car Radio Size) $4.30 6 foe 321.50 R. I. 94.5 WMOT-FM Pittsburgh, Pa. KALW San Francisco 8 for $20.50 91.7 Cali. 94.5 WNDB-FM Daytona Beach, 91.7 KOAG-FM Stillwater, Fla. 9 .. 21 oz. .. $4.95 6 for 526.50 Okla. 94.5 WSYR-FM Syracuse, N. Y. 91.7 KSDS San Diego, 10 .. 21 or. .. 65.50 8 for $30.00 Calif. 94.7 KOCYFM Oklahoma City, 91.7 KSUI Iowa City, Iowa Okle. 12 .. 21 or. .. $7.95 6 for $42.00 94.7 KROC-FM Rochester, M,,.5, 91.7 KUHF Houston, Tex. 94.7 WAAT-FM Newark, N. J. FILTER CHOKES- Mon Itght dory 91.7 WIUC Urbana, III. . T,- 1199c: 250 na 35 94.7 WAPO-FM Chattanooga, Tenn. '.dad -51.951 91.7 WJUN Philadelphia, Pa. 94.7 Chicago, I. .a e,. 1- Sleissner tYP0'. WLSU Baton Rouge, WENR-FM 91.7 La. 94.7 WMAS-FM Springfield, Mass. 91.7 WTHS Miami Fla. 94.7 WMCP Baltimore, Md. .79c. 91.7 WUOA Tuscaloosa, Ala. 94.9 KAKC-FM Tulsa, Okla. LIN 1111141. 110V-each c 91.7 Ann unit otalna two 2 mid. WUOM Arbor, Mich. 94.9 KCFM Kansas City, Mo. r . l a 1 5 1 1 1 1 1 . 1 . core 92.1 W2XEA Alpine, N. J. such hunter 94.9 KFPW-FM Fort Smith, Ark. 92.1 WNAE-FM Warren, Pa. m Oar ! foe 98.e 94.9 KING-FM Seattle Wann. 92.3 KFEQ-FM St. Joseph, Mo. SELENIUM RECTIFIERS -Dry disc type 1if. 1. 1.2 94.9 KSCJ-FM Sioux City, Iowa Amp. n..- for convening tut relays too 92.3 KRPO San Jose, Calif. 94.9 KSFH San Francisco, Calif. AC, - ; lug 1, ament h, mnmb:e radios, 92.3 KVNJ-FM Fargo, N. D. converting 11C meters b ACC U ae am also 94.9 WCMW-FM Canton, Ohio ppllraums. 92.3 WEBC-FM Superior, Wis. 111.0 be Used In sow current chargers-90c. 94.9 WDBJ-FM Roanoke, Va. 92.3 WCOH-FM Newnan, Ga. 30 MC IF loulde slug Wiled-25e. 94.9 WMRC-FM Greenville, S. C. 30 MC VIDEO AMPLIFIER 92.3 WCOL-FM Columbus, COILS -Slug Ohio 94.9 Miami Fla. unes -2Se. 92.3 WJOB-FM Hammond, Ind. WQAM-FM 94.9 WWCF Greenfield, Wis. 92.3 WPRO-FM Providence, R. I. 94.9 Indianapolis, Ind. BUFFALO RADIO SUPPLY 92.5 KCMC-FM Texarkana, Tex. WXLW-FM 95. San Bernardi.,o 92.5 KRLD-FM Dallas, Tex. KFXMFM Calif. 219 -221 GENESEE STREET. BUFFALO 3. N. Y. 95. St. Louis, Mo. 92.5 KYWFM Philadelphia, Pa. WEW-FM DEPT. 9C 95. Columbus, Ga. 92.5 WFRS Grand Rapids, Mich WGBA-FM 95. WGPA-FM Bethlehem, Pa. 92.5 WGOV-FM Valdosta, Ga. Huntsville, Haverhill, 95. WHBSFM Ala. 92.5 WHAV-FM Mass. Clarksburg, W. Va. 92.5 WINC-FM Winchester, Va. 95. WPDX-FM 95. WRXW Louisville, Ky. 92.5 WMBD-FM Peoria, Ill. Come to the Great 95. WTMA-FM Charleston, S. C. 92.9 K B U R-FM Burlington, Iowa Bellaire, Ohio 92.9 KDKA-FM Pittsburgh, Pa. 95. WTRF-FM 95. WVFC Ithaca, N. Y. SHOPS OF 92.9 KGDM-FM Stockton, Calif. 95.3 KGBS-FM Harlingen, Texas 92.9 KONO-FM San Antonio, Texas San Jose, Omaha, Nebraska 95.3 KSJO-FM Calif. 92.9 KOAD-FM Cleveland Heights, Chio 92.9 WBNY-FM Buffalo, N. Y. 95.3 WSRS-FM COYNE 'fric` 95.5 KECA-FM Los Angeles, Calif. r. 92.9 WBZ-FM Boston. Mass. Portland, Ore. whereyouiearn by doing - SILL,/ 92.9 WEEU-FM Reading, Pa. 95.5 KPRA i 95.5 KRBA-FM Lufkin, Texas 92.9 WOSH-FM Oshkosh, Wis. Atlanta, Ga. 93. KNX-FM Hollywood. Calif. 95.5 WBGE-FM 95.5 WCHA-FM Chambersburg, Pa. 93. KWBW-FM Hutchinson. Kans. High -Salem, 95.5 WHPE-FM Point, N. C. 93. WAIR-FM Winston N. C. Johnstown, Pa. 93. WFBL-FM Syracuse, N. Y. 95.5 WJAC-FM Providence. R. I. 93. WGUYFM Bangor, Me. 95.5 WJAR-FM RADIO 95.5 WJZ-FM New York, N. Y. 93. WHYN-FM Holyoke, Mass. ELECTRONICS -TELEVISION Detroit, Mich. 95.5 WMBI-FM Chicago, III, 93. WJBK-FM Pottsville, Pa. 93. WKAT-FM Miami Beach. Fla. 95.5 WPAM-FM Albany, N. Y. Q , 93. W K BH-FM La Crosse, Wis. 95.5 WRWR 93.3 W FLA-FM Tampa, Fla. 95.7 KOA-FM Denver, Colo. To Succeed hi Television, You Need 93.3 WGBR-FM Goldsboro, N. C. 95.7 WCRS-FM Greenwood, S. C. 93.3 W I P-FM Philadelphia, Pa. 95.7 WMMW-FM Meriden, Conn. All- Around Radio Training! 93.3 WJTN-FM Jamestown, N. Y. 95.7 WMUR-FM Manchester, N. H. WKPB Knoxville, Tenn. Trained men needed now. Radio 93.3 95.7 WTPS-FM New Orleans, La. Radio Get 93.3 WKYC Paducah, Ky. training and be ready for a real future. Learn 95.9 WFMZ Allentown, Pa. 93.3 WRBL-FM Columbus, Ga. 96. KCRA-FM Sacramento, Calif. .41 actual equipment at Coyne. 49 years of train- WTMJ-FM Milwaukee, Wis. 93.3 96. KFMX Bluffs. Iowa ing experience Not "Home Study ". Free employ- 93.5 KOCS-FM 0-ta rio, Calif. Council ment service to graduates. Many earn while 93.5 WDHN New Brunswick, N. J. 96. KLCN-FM Blytheville, Ark. learning. If you are short of money, ask about 93.7 KRFM Fresno, Calif. 96. WAMS-FM Wilmington, Del. student Finance Plan. Now added Training in 93.7 KV5O-FM Ardmore, Okla. 96. WBCM-FM Bay City, Mich. Electric Refrigeration. G.I. Approved. 93.7 KXOK-FM St. Louis, Mo. 96. WCAE-FM Pittsburgh, Pa. SEND COUPON FOR FREE BOOK B. W. COORS President NEW BUSINESS cOYNE ELECTRICAL a RADIO SCHOOL mechanism, power or outlets, convert, 500 S. Paulin. St.. Dept. 08 -811. Chicago 12. III. Multiple coin timer clocks for utility revamp new machine Iron, Fans, Air- condition- ',end Big Free Book; also details about Coyne Part- any or old A.C. radio, Washing- ing, Refrigerators, Heaters, Ice -makers, etc., for coin machine operation. 1 laze Employment and Student Finance Plan. TIMER MECHANISM, LIGHT-CORD AND FITTINGS NAME AGE 5c for 10 minutes $4.95 TIMER MECHANISM, LIGHT -CORD AND FITTINGS 25c for I hour or 2 hours each $4.95 ADDRESS Quantity Lots Write If-Oi. Roe Aeyeles C ITV 4TATF RADIO- COIN -MATIC 1110 S. Normandie, Los Angeles 6, Cal. RADIO -CRAFT for 8!1 RG -8 /U COAX CABLE 500' 195 PHANTOM ANTENNA mil. Only $3.95 3 CONDYCTO RPM RG -8 /11 is the ideal cable for feed- TELEPHONE WIRE ing, receiving and transmitting antennas for all frequencies up to 250 3 conductor Braided % MC and can be used up to 3000 M(' insulated copper & steel A transmitting wire. is and DOWN to DC. New in 100 foot telephone It antenne, tot use on lengths. Less than ever before. made of copper for con. ductivity, and steel for approximately 450 95 Only strength. Worth at least MC. Complete with 3c per ft. Yet due to an standard coax coo- $395 exceptional buy, we can tore A weather. now offer it at less than proof unit. ,Add lc a ft. 25c to cover hand- Shipped express rnllcrr Shipped Expres. Collar ling and postage..

Ideal for o boom rotor, plenty of pow.,. Ori- ginally deugn.d for 24 volt S operation, but easily led, 110 volts AC Complete instructions included. Excdl.nt for other // c too. Brand new, surplus, gsorontd..e y "ívei/F,f- Add 40. .00h to cover postage and handling 5

Brand new Bowfin D.C. Volt meter 0t. 9 volts in 2" caw wilh 2 3/4" IMPORTANT! Flange _ - ..ch .99c Brand new Bowersn D.C. An.t.rm rDl0t 0 t. 100 me scales '600 me Brand n All merchandise subject to prior 3 0.3, DC voltmeter J movement . .th 100 mp shunt 2" round case sale, minimum order $2.00, No Meter hoe 450 ohm, same caw O. olt mt., each 99c n,tonc 150 C.O.D. orders accepted. Mich, - ,ohms per volt,. Add Add I 5c ach to 20e each to gon residents must add 3 tont, postage and hand. co, po,tag State and ha..dlina soles tax. ling

6532 EAST McNICHOLS ROAD DETROIT 12, MICHIGAN s&,ffc o sagaza,-

FREQUENCY (MC CALL LOCATION

96. WGAA-FM Cedarstown, Ge. 96. WMBH-FM Joplin, Mo. GASOLINE HEATER MOMDOL°GN`L 96. WNAO-FM Raleigh, N. C. 96. WOHS-FM Shelby, N. C. An internal combustion type heater which 96. WOWO-FM Ft. Wayne, Ind. will give 15.000 B.T.U. of heat per hour. Ideal- 96. WTAG-FM Worcester, Mass. ly suited for use with equipment, farms, boats, 96. WVJS-FM Owenboro, Ky. bungalows, cabins, trailers, work sheds. dark- 96.3 KRED Eureka, Calif. rooms, mobile equipment, transmitter stations KRKD-FM 96.3 Los Angeles, Calif. etc., and any place where a quick heat is re. 96.3 WBIK Chicago, Ill. 96.3 WINK-FM Washington, D. C. quired in volume. 96.3 WJMC-FM Rice Lake, Wis. Very economical in operation -tank holds 96.3 WJR-FM Detroit, Mich. which is for 96.3 WC/KR-FM New York, N. Y. one gallon of gasoline sufficient 96.5 KRON San Francisco, Calif. 6 hours operation. Uses any grade gasoline. 96.5 KSDO San Diego, Calif. 96.5 KSEI-FM Pocatello, Idaho This unit is designed primarily for aircraft 96.5 KXYZ-FM Houston, Texas installation, 24 -28 volts d.c., but it can be 96.5 WAPJ Altoona, Pa. readily adapted for a 115 or 230 volt 60 cycle 96.5 WGH-FM Norfolk, Va. power supply by use of a transformer and 96.5 WHEC-FM Rochester, N. Y. rectifier. Simple circuit diagram for adoption to 96.5 WHOO-FM Orlando, Fla. 115 or 230 volts 60 cycle use supplied with 96.5 WTIC-FM Hartford, Conn. each unit. Can be used on 32 volt farm or 96.7 WBUZ Bradbury Heights, Md. the 96.7 WEAW Evanston, Ill. boat systems as is without installation of 96.7 WSTC-FM Stamford, additional transformers, etc. Power consump- Conn. s rea-\abatw. 96.7 WVAW-FM Cheviot, Ohio. 0\ tOCK tion approximately 75 to 100 watts. KALB-FM Alexandria, a om ave`óarb' 5 96.9 La. eRtYateet`'lebbvr N om9o. Approximately 12" long x 914," high a BUB" 96.9 KCRK Cedar Rapids, Iowa We uN c9\ e\. jEßsgos èscor6àóE` pq user wide. Complete with technical manual and parts 96.9 KFBK-FM Sacramento, Calif. meterbte. ME s ' 96.9 KRBC-FM Abilene. Texas list. O sÿia aaeh.mete;\a^ 96.9 WCSC-FM Charleston. S. C. >áa p a r `ä ¡os 96.9 WEBR-FM Buffalo, N. Y. OV a\so é sobls. lets psmiiteÿi, o*rt $22.50 F.O.B. N. Y. 96.9 WIBX-FM N. Y. We lub i,o0 u Utica, ves. t`t ra ^re 96.9 WJHP-FM Jacksonville, Fla. e\ee êqodte estesstah Send for Free Circular 96.9 WLAN-FM Lancaster, Pa. 96.9 WLAV-FM Grand Rapids, Mich. 96.9 WOPI-FM Bristol, Tenn. c_ esyO" 96.9 WPAD-FM Paducah, Ky. MARITIME SWITCHBOARD 96.9 WXHR.FM Cambridge, Mass. 338 NEW YORK 13, N. S. N ori h 4- 8216 -7 -8 -9 97. KKLA Los Angeles, Calif. CANAL STREET 97. KMHB Belton, Tex. 97. KPFM-FM Portland, Ore. 97. KTUL-FM Tulsa, Okla. 97. WASH Washington, D. C. 97. WBBMFM Chicago, III. RADIO -CRAFT will pay full ;puce rate for construction article on 97. WBZA-FM Springfield, Mass. 97. WELD-FM Columbus, Ohio modern .standard and shortwave ree eiYers. Sets should be preferably- 97. WMHC Indianapolis, Ind. small- -six or less- -and built with new efficient postwar tubes 97. WNBC-FM New York, N. Y. tubes 97. WRCM New Orleans, La. and components. Similar articles on other radio and electronic equip- 97. WTCN-FM Minneapolis, Minn, 97. WWJ-FM Detroit, Mich. utent will also be welcomed. 97.3 KSO-FM Des Moines, Iowa SEPTEMBER, 1948 90 - RN

RISCO HAS IT FREQUENCY FREQUENCY (MC) CALL LOCATION (MC) CALL LOCATION DO YOU HAVE IN YOUR TELE -SET GHOSTS 97.3 KTRN Wichita Falls Texas 98.7 WGNB Chicago, Ill. 97.3 KWBR-FM Oakland, Calif. 90.7 WHKB Columbus, Ohio 97.3 KWBR-FM San Francisco, Calif. 90.7 WHOP-FM Hopkinsville, Ky, Trap it out with a NETCO 97.3 WFMY Greensboro, N. C. 98.7 WJNO-FM West Palm Beach, Fla. Television Eliminata 97.3 WHCU-FM Ithaca N. Y. 98.7 WPAG-FM Ann Arbor, Mich. m 97,3 WHP-FM Harrisburg, Pa. 98.7 WOR-FM New York N. Y. Ilu:ualaee.1 m .lenì unte EM. 97.3 WIL-FM St. Louis, Mo. 98.7 WSOY-FM Decatur, III. .ilato .nil ,II 0111 97.3 WIOD-FM Miami, Fla. 98.7 WWVA-FM Wheeling, W. Va. I.o.lt,.,n - in ,nn,slio4e- 97.3 WKWK-FM Wheeling, W. Va. 98.9 KBOA Kennett, Mo. 97.3 WROL-FM Knoxville, Tenn. 98.9 KJBS-FM San Francisco, Calif, 97.3 WTARFM Norfolk, V-a. 98.9 WCOAFM Pensacola, Fla. 97.3 WTOC-FM Savannah, Ga. 98.9 WHBF-FM Rock Island, Ill. II 97.5 KPOR Riverside, Calif. 98.9 WHFM Rochester, N. Y. rr o 97.5 KWNOFM Winona, Minn. 98.9 WM-FM Youngstown Ohio m 97.5 WAKRFM Akron, Ohio 98.9 WKY-FM Oklahoma City, Okla, 97.5 WATL-FM Atlanta, Ga. 98.9 WSNJFM Bridgeton, N. J. 97.5 WBOC-FM Salisbury, Md. 98.9 WSPA-FM Spartanburg, S. C. $600 97.5 WESB-FM Bradford, Pa. 99. WNHC-FM New Haven, Conn. 97.5 WLVA-FM Lynchburg, Va. 99. KUGN-FM Eugene, Ore. 97.5 WSIX-FM Nashville, Tenn. 99. KWK-FM St. Louis, Mo. SERVICEMEN'S SPECIALS 97.7 WISR-FM Butler, Pa. 99. WDOS-FM Oneonta, N. Y. 97.9 KFAB-FM Lincoln, Nebr. 99. WGTR Boston, Mass. 1, 'L\\" 51.45 100-1\FUI. Rl.]., KIT '- 97.9 W BTM-FM Va. 99. WH1O-FM Dayton, 15-ASST. BV-PASS COND. .89 Danville, Ohio ALLIANCE PHONO SIOTIIItS 2.50 97.9 WEHS Chicago III. 99. WMAZ-FM Macon, Ga. ASTATII' 1.-70 l'II'KI'l'S 1.79 97.9 WFAA-FM Dallas, texas 99. WNAV-FM Annapolis, Md. ASTATII' L-70 CARTRIDGES 1.45 97.9 WGYN-FM New York,Y N. Y. 99. WSLSFM Roanoke, Ve. AST,\'fIC NVIA)N l-.1. 3.45: \II.II .. 1.95 97.9 WJLB-FM Detroit, Mich. 99. WTTH-FM Port Huron, Mich. .. 50141 0I"'I1'1T TRANS...... 35 97.9 WLEU-FM Erie, Pa. 99. WVMH Hillsdale, Mich. OVO P.P. OUTPUTS ...... 97.9 WLPM-FM Suffolk, Va. 99.3 KGAR-FM Garden City, IF TRANS. 456 KI' ,IIII.I.III.II INN 'I lilt Kans. 017I'I'T ea. .35 97.9 WLTN Lewistown, Pa. 99.3 WAJR-FM Morgantown, W. Va. MEISSNER OSI'. l'1)I1. I2s : .12 97.9 WMARFM Baltimore, Md. 99.3 WFRO-FM Fremont, Ohio VOLI-ME CONTROLS 500 \I \ > i. nn,4 l .29 97.9 WMRFFM Lewiston, Pa. 99.5 KFYO-FM Lubbock, Tex. ANTENNA. LOOPS. l'It151 & SLr .23 97.9 WRNYFM Rochester, N. Y. 99.5 KISS San Antonio, Tex. 2-TI'ItF: l'IIONO .531P. \1'I llt.l l 1.95 97.9 WWPG-FM Palm Beach, 99.5 KRIC-FM Beaumont, Tex. 2 TUBES 1.00 Fla. 10s 51.\ SI:LENII'3I RECTIFIER, .59 98. KOZY Kansas City, Mo. 99.5 WABF New York, N. Y. GE PREAMPLIFIER \\'ITII T1 /t1 4.25 98. KQVFM Pittsburgh, Pa. 99.5 WAFM-FM Birmingham, Ala. 6 FT. RUBBER LINE, MUDS .... .12 98. KRSC-FM Seattle, Wash. 99.5 WEFM Chicago, Ill. -F.1'4 TIT.I:\'ISI11N TI'111', 1J.95 98. WCOD-FM Richmond, Va. 99.5 WGFM Schenectady, N. Y. 100 FT. 3110 01IM LEAD IN 1.65 98. WLAU-FM Philadelphia, Pa. 99.5 WJLS-FM Beckley, W. Va. SI'I'EIt11ET VARIABLE lO\I. .59 98. WBRL Baton Rouge, La. 99.5 WMFR.FM High Point, N. 11111 FT. l'IIOSI'11OR 1f1111N%t II tl, ,' \Itl.l .59 C. R PUSH BI-TTON S\\'ITI'll ...... 39 98. WFMR New Bedford, Mass. 99.5 WMIN-FM St. Paul, Minn. SPAGHETTI-36' LENGTH .05 98. WFNC-FM Fayetteville, N. C. 99.5 WNLC-FM New London, Conn. Henderson V. 98. WSAL Saginaw, Mich. 99.5 WSON-FM Ky. M. -. VELVET MIXER 98. WVUN Chattanooga, Tenn. 99.5 WTAD-FM Quincy, III. RECORD CHANGER 98.3 KAGH Pasadena, Calif. 99.7 KNBC-FM San Francisco, Calif. 98.3 WEEX Easton, Pa. 99.7 KPDR-FM Alexandria, La. 98.3 WHAI-FM Greenfield, Mass. 99.7 KTFIFM Twin Falls, Idaho 98.3 WHNY-FM Hempstead, N. Y. 99.7 WHAS-FM Louisville, Ky. . 515.30 98.3 WLAD-FM Danbury, Conn. 99.7 WJAS-FM Pittsburgh, Pa. 2 for 529 i:FM11..% ...$13.75 98.3 WOAK Oak Park, Ill. 99.7 WMC-FM Memphis, Tenn. Portsmouth, \I Intl 528-prepaid 98.3 WPIK Alexandria, Va. 99.7 WSAP-FM Va. Astati. 1T30 Crystal 98.3 WTFM-FM Tiffin, Ohio 99.9 KBMT San Bernardino, Calif. Mikes 58.95 98.5 KBIX-FM Muskogee, Okla. 99.9 KMYCFM Marysville, Calif. SI;NlI t.. Lal,. I, 98.5 KBTR Minneapolis, Minn. 99.9 KVEC-FM San Luis Obispo, Calif. 99.9 Wichita $15.50 G , , . IL rdin_ Itta lik e. 98.5 KOPY Houston, Texas KWFT-FM Falls, Tex. 98.5 KWOS-FM Jefferson 99.9 W8T.FM Charlotte, N. C. Above Easily Attached to Any Radio City. Mo. or CAN BE USED WITH AMPLIFIER BELOW 98.5 WAGE-FM Syracuse. N. Y. 99.9 WCLO-FM Janesville, Wis. 98.5 WBRE-FM Wilkes- Barre, Pa. 99.9 WEBQFM Harrisburg, III. Condenser Specials -New Stock 98.5 WCBT-FM Roanoke Rapids, N. C. 99.9 WERC-FM Erie, Pa. 20 -20 -150 5 .29 s°.V CAN $ .16 98.5 WHLD-FM Niagara Falls, N. Y. 99.9 WFNS-FM Burlington, N. C. 20 -20 -150 CD .49 ss1011 l'1' u,.\NI .39 98.5 WJPF-FM Herrin, III. 99.9 WHFB.FM Benton Harbor, Mich. luslus lus lo -loo C .49 11 98.5 WKPTFM Kingsport, Tenn. 99.9 WKMO-FM Kokomo, Ind. 8- 45 \ - .29 I,IS üI, \' .45 8x8 -450V .45 -0s31ä130{' 98.5 WMOXFM Meridian, Miss. 99.9 WKRG-FM Mobile, Ala. .49 N. Y. UP TO -.112- PAPER 4 600V 10 for .42 98.5 WNAM-FM Neenah. Wis. 99.9 WKRT-FM Cortland, UP TO .25 10 for .52 98.7 KDYL-FM Salt Lake City, Utah 99.9 WSAN-FM Allentown, Pa. 98.7 KMGM Los Angeles, Calif. 99.9 WTRT-FM Toledo, Ohio. PHONO AMPLIFIER 98.7 KPOJ-FM nortland, Ore. 100.1 WKBR-FM Manchester, N. H. 3 -TUBE AC -DC 98.7 KVWC-FM Vernon, Texas 100.1 WLBRFM Lebanon, Pa. Wired and Te.IJ .52.75 98.7 WCTP Greer, - N. C. 100.1 WMUS-FM Muskegon, Mich. Volume and Tone Controls Set M 3-Tube. $1.75 mown Trme .35 5' Alnico Spk. 1.19 PHONO OSC -2 -TUBE & Teled BUFRAD CAR RADIO ANTENNAS 2 Tul.e- 81.20.. $2.75 2504 on O.O.D. orders. Order. Fulled as Received All of our crr radio antennas are made of triple plated Admiralty VISIT OUR NEW SNOW ROOM Brass Tubing, complete with low loss shielded antenna lends and Fred Catalog 1.C" Just Out high quality fittings. We Specialise in Mail Orders SIDE COWL -BR -1, 3 sections extend to 66 ". Your price -single lingo - 91.50; in lots of 12- -01.35 ea. RISCO ELECTRONICS SKYSCRAPER -BR-2 has 4 heavy duty sections that extend 98 ". This super -aerial must be seen to be fully appreciated. Your price WHOLESALE DISTRIBUTORS single units -$2.45; in lots of 12- -$2.25 ea. 25 West Broadway, N. Y. 1, N. Y. TILT ANGLE -BR -3, may be adjusted to all body contours, 3 sections extend to 66 ". Single unit prict- $1.50; 12 lot price-81.25 ea. VERSATILE -BR -4, single hole fender or top cowl mounting may he adjusted to conform with all body contours. 4 sections extend 1,. 36 ". Single unit price- 82.90; 12 lot price --92.75 ea. THE MONARCH -BR -5, single hole top cowl mounting, 3 section, exicnd to 56 ". Single unit price -- $1.90: 12 lot price --91.75 ea. AFTER SEEING OUR ANTENNAS AND COMPARING, GREYLOCK YOU WILL NEVER BUY ANY OTHER MAKE: BENDIX SCR 522 -Very high Frequency Void,- 'l'rau.mitter-Re- A Dependable Name in ceiver-10U to 156 MC. This job was good enough for the Join: Command to make it standard equipment in everything that flew. RADIO TUBES even though each set cost the Gov't 92500.00. Crystal Controlled GT, Glass, and Miniature Types. and Amplitude Modulated -HIGH TRANSMITTER OUTPUT and All Tubes Individually Booed. 3 up to 125A7. 125117. 12597. SOLD. 12Á76. Microvolt Receiver Sensitivity gave good communication 129A6. 128E6. 35W4. SOBS cn 39. 180 miles at high altitudes. Receiver has ten tubes and transmitter 4 IRS. ISS. 174, 354. 304. SANS. SACS. DA05. a has seven tubes. including two 832's. Furnished complete with 17 69ES. 611A6, 6AÚ6. 6116. 694. 11723. each 49c SOLI, 70L7. 117L7 each S9c tubes, remote control unit, 4 crystals, and the special wide band All Tubes carry RMA 90 -Day Guarantee VHF antenna that was designed for this set. These sets have been BRI BR2 BR3 BR4 BR5 removed from unused aircraft and are guaranteed to be in perferl Ide free PM SPEAKERS parts and diagrams for the conversion to "continuously variable I in the 4^ Alnico NO. S each $1.19 receiver. S^ Alnico Ne. S each 1.29 The SCR 522 complete with 24 volt dynamotor sells for only $37.95. 'The SCR 522 is also avail- Net COO. No order accepted for less than 59.00 able with a brand new 12 volt dynamotor for only $42.95, WRITE FOR BARGAIN CATALOG C -8 GREYLOCK ELECTRONIC SUPPLY CO. BUFFALO RADIO SUPPLY 30 Church Street New York 7, N. Y. 219 -221 GENESEE STREET, BUFFALO 3. N. Y. DEPT. 9C RADIO -CRAFT for FM !11

FREQUENCY (MC) CALL LOCATION THE NEW MODEL 40

00.3 KGW-FM Portland, Ore. 00.3 KMPC-FM Hollywood, Calif. 00.3 KSL-FM Salt Lake City, Utah, 00.3 WACE-FM UTILITY Chicopee, Mass. 00.3 WCLT Newark, Ohio. 00.3 WCNB Connersville, Ind. 00.3 WFMF Chicago, Ill. 00.3 WGBG-FM Greensboro, N. C. 00.3 WHO-FM Des Moines, Iowa TESTER 00.3 WMGM New York, N. Y. 00.3 WRAK-FM Williamsport, Pa. ACCURATELY TESTS 00.3 WSAV-FM Savannah. Ga. 00.3 WWLH New Orleans, La. RANGES 00.5 KMBC-FM Kansas City, Mo. SHAVERS HEATERS IRONERS 00.5 KSBR San Bruno, Calif. WASHERS FANS VACUUM CLEANERS 00.5 WDXY Spartanburg, S. C. AIR CONDITIONERS REFRIGERATORS 00.5 WFIN-FM Findlay, Ohio SUN LAMPS TOASTERS WASHING 00.5 WHMA-FM Anniston, Ala. MACHINES and MOTORS 00.5 WHTN-FM Huntington, W. Va. ALL MOTOR[ -single phase, multi -please, universal. squirrel cage. 00.5 WLDS-FM Jacksonville, Ill. induction. in fact every type of motor from fractional N.P. to 2 P.P. 00.5 WMNE Mt. Washington, N. H. 00.5 WMUS-FM Muskegon, Mich. THE MODEL 00.5 WNBF-FM Binghamton, N. Y. 40 UTILITY TESTER 00.5 WWNY-FM Watertown, N. Y. Rill Indir.tlr nh 'hr vial i o is ]lu Volts or 220 A'wits, if 00.7 KIRO-FM Seattle, Wash. current is . \.C. or I1.i'. and If frequency is VI cycles or 60 00.7 WBAB-FM Atlantic City, N. J. cycles. Will tes, 'Memo-nits under actual working condi- 00.7 WBIB New Haven, Conn. tions. \VIII measure the actual rtlrreut consumption of any ap- 00.7 WBML-FM Macon Ga. pliance either A.C. or D.C. while the unit is in operation - 00.7 WBOX-FM Louisville, Ky. reading will he direct in amperes -the appliance or utility 00.7 WCEC-FM Rocky Mount, N. C. may bo plugged Birr ally into front panel receptacle--a spe- 00.7 WCIL-FM Carbondale, Ill. dial pair of insulated clip -end hurls is provided fur nine,.. 00.7 WHKX Cleveland, Ohio Incorporates un °ItI.r- sensitive direct reading resistance rango 00.7 WKAP-FM Allentown, Pa. which will accurately hirssure all appliance and utility re- 00.7 WKIL Kankakee, III. sistances down to a fraction of 00.7 WRJN-FM Racine, Wis. an ohm. Will test bulbs. fuses. Model 90 Utility Tester condensers, field eons, etc. Is 00.7 WSVA-FM Harrisonburg, Va. comes housed in a rugged ideal trouble shooter as 00.7 WTJS-FM Jackson, Tenn. It will crackle finished steel cabinet instantly locale opens. shorts 00.7 WTRC-FM Elkhart, Ind. With portable cover. 00.9 WABX-FM Harrisburg, Pa. and grounds. Will locate muse 00.9 WBYS-FM Canton, Ill. of failure in three -way heat 00.9 WCFR Fall River, Mass. Control switches, Will indicate 01. KGLO-FM Mason Iowa when one side of appli- City, connected to 01. KHJ-FM ance moor cted Hollywood, Calif. line under test Is 01. KTRH-FM Houston, Texas Will indicate excessive leak- 01. KVCI-FM Chico, Calif. age between a ,rotor and a 01. KXLW-FM Clayton, Mo. line. \VIII hulicate when a I. WBBB-FM Burlington, N. C. three -phase moor is coing I. WBCA-FM Schenectady, N. Y. ertatirally dom to a "blown" 01. WBOW-FM Terre Haute, Ind. fuse. I. WCAC-FM Anderson, S. C. 20% DEPOSIT REQUIRED ON ALL C.O.D. ORDERS I. WCBS-FM New York, N. Y. I. WJPG-FM Green Bay, Wis. I. WKST-FM New Castle, Pa. GENERAL ELECTRONIC DISTRIBUTING CO. I. WLCS-FM Baton Rouge, La. DEPT. RC -9. 98 PARK PLACE. NEW YORK 7, N. Y. I. WLWA-FM Cincinnati, Ohio I. WWDC-FM Washington, D. C. I. WXYZ-FM Detroit, Mich. 01.3 KLX-FM Oakland, Calif. 01.3 WATG-FM Ashland, Ohio 01.3 WCFC Beckley, W. Ve. Better Products for the Radio Industry 01.3 WGAL-FM Lancaster, Pa. I 01.3 WSBF South Bend, Ind. 01.3 WSRK Shelbyville, Ind. 01.5 KFMB-FM San Diego, Calif. NEW G -C NEW G -C 01.5 KGKB-FM Tyler, Tex. 01.5 KMUS Muskogee, Okla. STATIC CHASER INJECTOR TUBE PULLER 01,5 KYFM-FM San Antonio, Tex. 01.5 WFMD-FM Frederick, Md. AND POWDER Makes it easy to remove or insert 01.5 WGCM-FM Gulfport, Miss. Tire static miniature tubes -simple to oper- 01.5 WIBA-FM Madison, Wis. powder kits ate. Inserts or extracts tubes 01.5 WJBC-FM Bloomington, III. - improve where fingers will not reach 01.5 WRAL-FM Raleigh, N. C. auto radio -into hard -to -reach places. 01.5 WSPD-FM Toledo, Ohio reception. Saves time and money. Ends 01.5 WWPB-FM Miami, Fla. Eliminates tube breakage, prevents 01.7 KWIL-FM Albany, Ore. wheel static inter- viso0 burnt fingers. 01.7 WFAH-FM Alliance, Ohio \ ferente. New pow- No. 5093- Miniature Puller List $1.65 01.7 WLIN-FM Merrill, Wis. der is blown into No. 5093 -D Display of 12 List 01.9 KARM-FM Fresno, Calif. all inner tubes -easy to use. For every $19.80 09.9 KFXD-FM Nampa, Idaho car owner. 01.9 WCTS Cincinnati, Ohio G -C "Speedex" 01.9 WGAN-FM Portland, Me. No. 5604 -- Injector for G -C Static Pow- 01.9 WGHF New York, N. Y. der List $1.50 WIRE STRIPPER 01.9 WGNC-FM Gastonia, N. C. No. 5605-G -C Static Powder Packet 01.9 WSFL Springfield, Mass. for S tires List $1.00 Strips 01.9 WSYO Sylacauga, Ala. insulation from wire sixes No. 5606- Kit -One Powder packet and No. 01.9 WVBT South Bristol, N. Y. injector List 8 to No. 30. Ideal tool for $2.50 manufacturers, electricians, maintenance men, etc. Strips G -C FELT KOAT FLOCK 750 to 1000 wires per hour. FINISH SPRAY KITS For the new 300 ohm Television Now it's easy to supply I and FM twin transmission line: flock for refinishing turn- tables, cabinets, grilles etc. Kit con- No. tains specially designed spray gun, 2 733 -H Standard Model List $6.00 colors flock, undercoats, thinner, brush, No. 744-H Automatic Model List 8.00 instructions, etc. No. 180 -2 List $9.50 are G_C products at leading Hove you seen the new G-C availoble rite for Wire Strippers write W "Speedex" ... distributors. our new for illustrated literature. your copy of catalog. RADIO DIVISION DEPT. D illustrated

GENERAL CEMENT Mfg. Co., Rockford, III., U.S.A. Suggested ,eft, by it'. J. Coe Springfield, Maas. Manufacturers of over 3,000 products Soles offices principal crises "Look Ma! We're playing television." SEPTEMBER, 1948 ye, RM

FREQUENCY rHARD-TO-GET PARTS-. (MC) CALL LOCATION POWERFUL ALL- PURPOSE INDUCTION SEPTEMBER MOTOR 01.9 WVCV Cherry Valley, N. Y. SPEI iot AL FOR 02. KSTP-FM St. Paul, EXPERIMENTERS -101 USES Minn. 02. KRKN-FM Sturdily constructed to precisionn Fort Smith, Ark. 3 TUBE PHONO st this 02. WELL-FM Battle Creek, Mich. ndaeC .. hisestartinghadedaelso 02. WEWS-FM Cleveland rful enough for number of uses. Ohio AMPLIFIER Some of these are: Automatic Tor- 02. WFIL-FM Philadelphia, Pa, ino Devices. C Interrupters. 02. WIMA-FM Electric Fans. Electric Chimes. Lima, Ohio Window Displays. Photocell Control 02. WRNL-FM Richmond, Va. Devices. Electric Vibrators. Small 02.3 WGAY-FM Silver Spring, Ori . Md. $1.95 Min,ature P50105 Mandchanical` Mod- 02.5 WFJS Freeport. III. tiIs. Sirens. and other .00110a- inns. 02.5 WIBWFM Topeka, Kans. Consumes 02.5 WNDR-FM Syracuse, N. Y. COMPLETELY rower and hasna speed or 13.000 WIRED, ' "down. this 02.5 WISE-FM Asheville, N. C. VOLUME AND sturdy unit will constantly riper- 02.5 WOAI-FM San Antonio, Texas TONE CONTROLS Me loaded 02.5 WPLH-FM Huntington, W. 200 lbs. dead weight áÚ\TS POW EENI Va. Set of 3 tubes: 50L6. 35Z5, 12A6 $1.10 mounting- by 02.5 WRVC Norfolk, Va. Output trans. SO 1.6 .35 haDi4ntenslvenient studsstuds: °sh Is I 'Tay Ions 02.5 WTSP-FM St. Petersburg, Its Meg. vol. by 3/18. Fla, control with sw. .35 volts 02.7 KCRC-FM Enid, 4 pm speaker .95 Designed ïí0.20 . 50.00 Okla. les. A.C. only. Ono. Wt. 2 Ins. 02.7 KOKX-FM Keokuk, Iowa 5" pm speaker 1.15 ITEM NO. 17 r pm speaker 1.55 YOUR PRICE $2 957 02.7 KFMY Fort Dodge, Iowa r pm saker 2.75 02.7 WCAO-FM Baltimore, Md. 12- pm speaker 4.89 02.7 WSMB-FM New Orleans, La. 4 x 6- pm speaker 1.89 ULTRA MAGNET Astati, 02.7 WTRI-FM Troy, N. Y. pickups 1.89 LIFTS MORE i AN 20 TIMES 02.9 KFOR-FM Lincoln, Nebr. AstaUo crystals 1.59 ITS OWN H 02.9 KPRC-FM Houston, Tex. Alliance motor & turntable 2.50 LITTLE GIANT MAGNET Von 1400 intermix changer 02.9 WCVS-FM Springfield, Ill. 28.95 t.lfts 5 Iba. easily. Weigh. ox. Made of ALNICO n high- magnetic 02.9 WFMU Crawfordsville, Ind. steel. Complete withkeetnr. World 02.9 WHKY-FM Hickory, FAMOUS MAKE CONDENSERS Tmost powerful magnet ever made. N. C. he W /Vlsl will 02.9 WJDX-FM Jackson, Miss. 50 x 30 150v... experimenter il ht. .45 39 and hundreds of a cement use for 02.9 WLET Toccoa, Ga. 20 x 20 150v... .35 400v or 600v ... per 10 this high quality epermanent manelMi . 02.9 WPEN-FM Philadelphia, 20420 (10) 156v (25) ^ hip- Wl. Pa. .39 .01. .02. .05 .49 02.9 WPIC-FM Sharon, Pa. 8 R 8 450v.... .49 .001, .002. .005 .49 ITEM ENO. WI $1.50 02.9 WRLD-FM Lanett, 25 25v 29 OUR PRICE Ala. 25 03. KRJM Santa Maria, Calif. GENUINE MICROPHONE TRANSMITTERS 03. WCTW New Castle, Ind. AN prices F.O.. N.Y.C. -on C.O.D. 2504 Deposit. 03. WFMO-FM Jersey City, N. J. Write for free catalog. Regular taken froom large 03. WJJW Wyandotte, Mich. telephone supply - 03. WOAP-FM Owosso, Mich. panY k. eork 03. WRGK La Grange III. THE ROSE Cyaen `2 dry ivy- COMPANY used 03.3 KBEE Modesto, Calif. is call systems. inter- 88 West Broadway, Dept. C, New York 7, N.Y. communicationsten 03.3 WAGA-FM Atlanta, Ga. short-lint telephone Mr. 03.3 WDBQ Dubuque, Iowa fapets. house -to -house rm -lo -farm hone lines. 03.3 WEEI-FM Boston, Mass. also toa talk (Mooch 03.3 WIZZ Wilkes- Barre, Pa. or concealedi r 03.3 WLOG-FM Logan, W. Va. dicta hone ick Use - 03.3 WSBA-FM York, Pa. tery- operated`Irrurural tole- 03.3 Montgomery, ¡¡oonce WSFA-FM Ala. TRF.8E lines.ARE GENUINE 03.3 WSM-FM Nashville, Tenn. TRANSMITTERS. MADE. BY KELLOGG. Mankato, DUE TO POPULAR DEMAND ELECTRIC AND STRation. excellent In 03.5 KYSM-FM Minn. si,eesrann and operation. A remarkablere kip le vn1.Ie and 03.5 WMOH-FM Hamilton, Its Ohio seldom offend In these times. nShlp. Wt. 1 03.5 WSOC-FM Charlotte, N. C. WE REPEAT THESE ITEM No. ISO YOUR PRICE $1.95 03.5 WSTV-FM Steubenville, Ohio 03.7 KOW-FM San Francisco, Cali,. WATTHOUR METER 03.7 WFBGFM Altoona, Pa. Completely rhaulee and 03.7 WJBY-FM Gadsden, Ala. for Immed service. New TERRIFIC BARGAINS Dreadyesigned for regular 1In. 03.7 WKNB-FM Britain, Conn. volt. 80 cycle 2-wire A.C. 03.7 WROV-FM Roanoke, Va. 'fhrc; ii,orted new circuit. Simple to Install: 03.7 WSAR-FM Fall River, Mass. MICROPHONES. 2 wires from the line 1 including push -to -talk type 51.99 2 wires to the load. Slurd- 03.7 WTAX-FM Springfield, Ill. lly nstru ted In heave metal case. 8l/' high. 03.9 KENO-FM Las Vegas, Nev. Ten assorted R. F. Chokes including wide. 5^ deep. Wresting. 03.9 KOPP-FM Ogden, Utah high frequency types Monte. G. E. Ft. Wayne. $ .35 Saki available 03.9 WBNU Aurora Ill. Five aasorted AUDIO or FILTER Shit r Wtflrr 03.9 WDLB-FM Marshfield, Wis. 03.9 WFAS-FM White Plains, N. Y. CHOKES I .99 YOUMR PUl E $6.50 03.9 WJEM Springfield, Ohio One Hundred assorted RESISTORS $1.95 03.9 WTAL-FM Tallahassee, Fla. AMAZING BLACK LIGHT!! 03.9 WXNJ Green Brook Twp., N. J. Ten aasorted JAN CABLE CONNEC- Powerful 230 Watt Ultra -Violet Source 04.1 KFUO-FM St. Louis, Mo. TORS. including SCR274,522 and The best ana o t practical 04.1 KMFM Monroe, La. BC375 types 8 .99 aource of ltravioler light for 04.1 WBMS-FM Boston, Mass. Six aasorted OIL Anon nsept use.r) all ° fluorea. 04.1 WJW-FM Cleveland, Ohio PILLED CAN TYPE ant bstances brilliantly lumi- 04.1 WLAB Lebanon, Pa. CONDENSERS, all with mounting nescent. brackets eded. Fits anyy atandarl 04.1 WMUN Muncie, Ind. $1.49 lamp socket. Brings out beau - 04.1 WPAY-FM Portsmouth, Ohio opalescentmaterials. r Ten assorted METAL & BAKELITE type Sn ell for 04.1 WRUF-FM Gainesville Fla. KNOBS no amateur parties. Warns. etc.: m 04.1 WSJS-FM Winston-Salem, N. C. --1 wooden knobs) 1 .39 SEll in reloue light n` nee U. ulk Only. Ship. WI. R lis. 04.3 KGNC-FM Amarillo, Texas Six assorted VARIABLE CONDENS- ITEM NO. 87 04.3 KTOK-FM Oklahoma City, Okla. ERS, including butterfly types 11.49 YOUR PRICE $2.50 04.3 KWI K-FM Longview, Wash. Baton Six asserted POWER and AUDIO 04.3 WAFB-FM Rouge, La. TRANSFORMERS, all WESTERN ELECTRIC BREAST MIKE 04.3 WEXL-FM Royal Oak, Mich. new 91.98 Thisla fine Baltimore, Md. carbon icrophone. ItEneigh. 04.3 WITH-FM Six aasorted isolantite and bakelite R. F only I lb. 04.3 WLOS-FM Asheville, N. C. COILS, shielded and unshielded with 04.5 KIXL-FM Dallas, Tex. $ .99 d has swivel-4 o ti` an 2.wawÌy`se 04.5 KRCC Richmond, The above ten assortments totaling over $12.00 at the nnnging adlustment so that It can be Calif. adjusted to anyn desired position. 05.5 WHIS-FM Bluefield, W. Va. unbelievable bar ain prices listed can be purchased There am 2 straps: t. together as one lotlot a super- special total price of goes around np eck. the other 04.5 WWST-FM Wooster, Ohio only 910.00. All merchandise guaranteed to be as round 1e hest. Strap, he 04.7 KWFM San Diego, Calif. advertised. ingereed n and off quickly lo, an nious arrangement. 04.7 WF.INFM Fitchburg. Mass. This excellent mike n h' 04.7 WHVA Poughkeepsie, N. Y. BUFFALO o broadcasting or RADIO SUPPLY privlaeA communication sy 04.7 WIST Charlotte, N. C. 219.221 GENESEE dismounting breastplate. iernsit can be 04.7 WJF.I-FM Hagerstown, Md. STREET BUFFALO 3. N. Y. used as desk mike. DEPT. 9C Comes complete with 0.foot 04.7 WJI.D-FM Birmingham, Ala. c I and hard liner plug. Finished in aherardlxed 04.7 WOPT-FM Oswego, N. Y. plate. n stal.le. Shipping weights 2 lbs. 04.9 KONG Alameda, Calif. ITEM 152 YOUR PRICE $1.49 04.9 KURV-FM Edinburg, Tex. 04.9 WLAL Lakewood, Ohio 04.9 WMCK-FM McKeesport, Pa. HUDSON SPECIALTIES CO. 05.1 KCLI Los Angeles, Calif. 40 Broadway. Dept. RC9 -48, New 12B8 and 2588 TUBES West York 7. N. Y. 05.1 WONC-FM Durham, N. C. below me or the items I'm 05.1 WFMJ-FM Youngstown, Ohio onionig. `My r`Ìfull .. A.lapter unit, using 2 miniature tubes I GATO elude shipping charges, Is enclosed 05.1 WODI Quincy, Ill. and 6BA61 or (1211A6 and 12AT61. Takes WÌTtd (NO[PC.O.D. 05.1 WVCN De Ruyter N. Y. less apace than original OR my deposit of S is enclosed iglIch 05.3 WARY Norfolk, Va. tube-nothing else Ired : only order C_O.D. for balance. NO C.O.D. to buy -just plug in and works. 3.00. E[ SURE TO IN- 05.3 WWHG Hornell, N. Y. it Money - ING3 CHAR back guarantee. 12B8 or 2588 unit complete: ClKlet.7mCLUDE SHMG. `nit 05.5 WFOB Fostoria, Ohio $2.49 each. 10 units for 122.50. ISO 160 Si 152 33 05.7 KIMV Hutchinson, Kans. 05.7 KUOA-FM Siloam Springs, Ark. Send 25% deposit, balance C.O.D. Write for Iowa free parts catalog. Name 05.7 KXEL-FM Waterloo, 05.7 WARM-FM Scranton, Pa. 05.7 IdDAEFM Tampa, Fla. COMMERCIAL RADIO Adema Please Print Clearly 05.7 WMBS- Uniontown, Pa. 36 BRATTLE STREET 05.7 WRUN-FFMM Rome, N. Y. BOSTON 8. MASSACHUSETTS City Sute 05.7 WSIC-FM Statesville N. C. 05.9 KFI-FM Los Angeles, Calif. RADIO -CRAFT for 93

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FREQUENCY WAR SURPLUS 1SAKtiAIN SPECIAL! TEST -AID (MC) CALL LOCATION Brand New FIRST -AID FOR RADIO -TELE SETS 05.9 KOMA-FM Oklahoma City, Okla. BEAM ANTENNA ONLY 05.9 KSBS Kansas City, Kans. 06. KDNT-FM Denton, Tex. ROTATOR $ll 95 06. KGO-FM San Francisco, Calif. 06. KIDO-FM Boise, Idaho MOTOR 06. WKJG-FM Ft. Wayne, Ind. 06. WKNP-FM Corning, N. Y. $595 06. WLOB-FM Claremont, N. H. COMPLETE 06. WTHT-FM Hartford, Conn. Postpaid in 06.3 WMLN Mt. Clemens, Mich. 06.3 WOTW-FM Nashua, N. H. Continental U.S.A. WRITE FOR 063 WBEN-FM Buffalo, N. Y. CATALOG OPERATES DIRECTLY ON 11OV AC, 60 CYCLES 06.5 WFML Washington, Ind. (Requires only 12 MFD Condenser) SHEET 06.5 WGOR Ft. Lauderdale, Fla. NO STEP -DOWN TRANS. NEEDED AND RESIS- 06.5 WRGA-FM Rome, Ga. NO LINE RESISTOR NEEDED TORS FOROFAT S FAULTYGCONDENSERS 06.5 WSTP-FM Salisbury, N. C. Tenn. HIGH TORQUE - NO FREE SWING SUBSTITUTES 11 DIFFERENT VALUES OF CAP. OR 06.7 WCLC Clarksville, RES. WITH SET IN OPERATION SOmml to Omrd 450- 06.7 WGTM-FM Wilson, N. C. APPROX. J/ R.P.M. 600 WVDC-27 ohms to S men. 06.9 WHHM-FM Memphis Tenn. REVERSIBLE - ONLY THREE WIRES NEEDED CHECKS CONDENSER LEAKAGE ON DIRECT CURRENT 06.9 WMIT Winston -Salem, N. C. ELECTRICALLY & MECHANICALLY QUIET SUPPLIED FROM OWN PWR SUP. 07.1 WAJL Flint, Mich. LIGHTWEIGHT, RUGGED, QUIET OUTPUT INDICATOR FOR ALIGNMENT -CONTINUITY 07.1 WCAP-FM Asbury Park, N. J. MOTOR & GEARS OIL SEALED CHECKS 07.1 WLEY Elmwood Park, Ill. NO EXPENSIVE CONVERSIONS PROVIDES 100 VOLTS AT 100 MA FOR EXPERIMENTS. 07.1 WWDX-FM Paterson, N. J. FLAT MOUNTING SURFACE 01.3 KSEO-FM Durant, Okla. - These are only few of the many uses the TEST-AID. FOUR TAPPER HOLES 07.3 WBNB Beloit, Wis. FI. FOR 2 -6 -10 -LITE 20 BEAMS oses h at your e oseesoof 07.3 WFMI Portsmouth, N. H. or write as FREE COMPLETE INSTRUCTIONS A DIAGRAMS due t. es . 07.3 WMAL-FM Washington, D. C. \' o 07.5 KTEM-FM Temple, Texas ALVARADIO SUPPLY CO. BKLYN, N.Y 07.7 KFSA Fort Smith, Ark. DEPT. RC3. 903 S0. ALVARADO 256 E.98th STREET, 07.7 WAYS-FM Charlotte, N. C. LOS ANGELES 6, CALIFORNIA 07.9 KXOA-FM Sacramento, Calif. WABB Mobile, Ala. GENERAL ELECTRIC RT -1248 15 -TUBE 07.9 -RECEIVER 07.9 WDAK-FM Columbus, Ga. TRANSMITTER 07.9 WEMI New Haven, Conn. PEN 1 1 -OSCIL -LITE 1 1 R 4 - , ' F u instantly t 435 to 07.7 WFNF Wethersfielrj, N. Y. Extremely convenient test oscillator for all radio Western 07.7 WLIV Providerce, R. I. servicing; alignment Self A IC. ul.es includ- and 07.7 WVBN Turin, N. Y. froma 7000 l cycles °audio to v ing11I,:,a s,' s s1 davriuraild oscillator. 3- 000 megacycles u.h.f. Cutout from zero to 125 V. 7H7's as IV's. 'ww -ith 4 lug -tuned 40 Mc. IF trans- 07.9 WEST-FM Bethlehem, Pa. in Ued by Signal Corps Write for formers. tutus a 7H7, 7E11'a and 7E71s. In addition ILownformation.o contains 8 relays leaigned to ol,erlie ally sort of 07.9 WRRN-FM Warren, Ohio unit signal externaltai equipment when actuated by received 07.9 WWOD-FM Lynchburg, Va. GENERAL TEST EQUIPMENT a similar set elsewhere. Originally designed for as it 12 volt operation.ung power au1ply is not included, ILfat 3$ Argyle Are. Bulialo ! N. Y. 110Va AC. any supply canonic of 00V 135MA. The ianuptaoetí4Oideal unit for use in mobile or stationary service in the Citizen's Radio Telephone Hand where The stations are listed this month by no i cense is necessary. Instructions and diagrams TUBE SPECIALS uuplied for running the RT -1248 transmitter on either nr frequency and the list was checked AC -DC live -50L6GT, 35ZSGT. 12SM. K7, Q7OT..81.90 ((eh' n e ln AM or FM transmission reception. Miniature Me --5055, 35W4, 12AT6. ItA6 BES.... 1.90 for e as mobile public address system, an an 80 to FM receiver. as Facsimile against the latest information available. * TWO JUMBO ASSORTMENTS * a Am tterror ieeceiverA as °a mateur elevislion for you, 40- 35'/.5. 20- 501.0. 10 ea. 35M. 12225.\7. KT. Q7. 100 tubes. eiver, for remote control relay hookups. We'll have another list prob- 40-33W4. 30- 50115. 10 ea. 12AT6. 846. BEd. 100 tubes. for Geiger- Mueller counter application. It sells for Either of the above specials at only only 629.95 or two for $53.90. farine ably in December, giving the latest $34.00 Ifhdesired ffor Every tube new snd perfect. Guaranteed 100%. either 1z r 24v DC and supply all p,wersfor the information. This month's list gives 121 Selenium miners 100M.4 -ten for $7.20 additional. Footage . ZOO'. deposit on C.O.D. orders. set is only $15.00 Send for our new bargain list. BUFFALO RADIO SUPPLY stations more than our June list, indi- 219.221 Genesee Street. Buffalo 3, N. Y. Degt. 9C HALLMARK ELECTRONIC CORPORATION cating the rapid growth of FM. 592 Communipaw Ave. Jamey City A. New Jersey SEPTEMBER, 1948 91 I Rook Reviews TECHNIQUE ()l- MI( ROWAN 'tEASt'RE- MENTS 1 Volume XI of the M.I.T. Radiation Laboratory Series), edited by Carol G. Mont- gomery. Published by McGraw -Hill Book Co.. Inc. 6% x 9V. inches, 939 pages. Price $10. Like the other volumes of the MIT Radiation Laboratory series, Volume XI is a compilation, written by several authors, of knowledge gained during the war in many laboratories. There are four main measurement techniques covered by the book. These are power, frequency and wavelength, impedance and standing waves, and attenuation and radiation. Each technique differs radically from its counterpart in low- frequency work. Not only must standard procedures be revised, but many new factors must be taken into account. The dielectric constants of all the media and materials concerned must be accurately known, for example, and such properties as the capacitance and inductance of the shortest wire connections assume great importance. Elec- tron transit time makes normal tubes useless in microwave work and special klystrons have been developed. PRACTICAL INFORMATION This volume is a comprehensive and authoritative compilation of all the

have bran i a it mg ter. available information on microwave Whether you're interested in amateur or professional measurement. But in describing meas- recordine, .you'll find PRACTICAL DISC RECORD- urements, a good deal of information on ING by Richard H. Dorf invaluable. It not only tell, the basic methods of flizszvcrs you how to make successful records. but in addition generation, propa- each important recording component is given n full gation, and reception is given. The cal- chapter, explaining its purpose. and what features culation of waveguide dimensions and to look for when buying. the conformation of the guides Without is treat- You'll like this book for many reasons. ed in great detail, as are many other Your waste of words. it gets right down to business on the first page. It tells you what you need to make subjects, such as klystrons, oscillators, good records and how to do it by using any type and attenuators. R.H.D. equipment --from the simplest to the most expensive -depending on your purpose and pocketbook. You u will find all the practical phases of recording cov- TELEVISION -HOW IT WORKS, by Wm. cs/ions underlying S. Q ered as well as the principles. Rouie. D. ('clan, H. Chanes and R. F. Koch. Published by John F. Rider Publisher, Inc. Paper covers. S'. x II inches. 203 pages. Price $2.70. FILLED WITH FACTS The works of four authors have been combined in this latest edition to the Chapter I di.. 0- mrv,mol. I.hirh Hake up the

1 I l l i l - rnnp11.11. syst1.,', Chinn., 2 to 5 t ion 1 1 1 praetir:ll r a Rider's "How it Works" series. These o 110 0..0.11111 .' ' list.S. 11111101s : ml mrllt:ddr.. (col authors present television theory so it ach ails., ud Chapter 6 nton,I tra i pimlali,u , un amplitude and I Islam velocity repaid is easily understood by anyone with a ni,. lnudaunulal I ,riling elan armlet 11., t tithirh knowledge of basic radio. ail l,hor,'i ó.t011. Chapter 7 t sI VIII, aItr11011. In Chapter 8 Ibe soot .muce. 111111.101111011e. adl. There are 12 chapters covering tele- 111111ns, rlr.l 1lis tu .r,i.1 .t female Is the handy chart of aha arLr is lisa tit di17uirnl types u1. raphinie. Chapter 9 vision systems, television signals, andl.rusrs Ihl all Important midilha.li l'irrui is of 1.:d tennas, r.f. circuits. audio and video pl aal trot auipli this ale tienn. In Chapters IO thru 13.s ypn'll 1111 eapl:Iin0,1 1110 .101:11101 techniques al Inakint goal 1 rids. channels, sync and sweep circuits, pic- All the liar Pntu1 ul :n hus11ural. 01p1a11a:u lun, 1111,1011110111. ture tubes, power supplies, and TV re- i 1. l , placement awl n i phwa 110 111 01111 a w ho l e ehapl l dobbin,. Chapter IC is nahe S111111111113. n( t ceiver servicing. The book is well illus- 110111110: 1 lud hor Iot n eremite them. The nbook trated with drawings and partial sche- Ito ill 11 a elus..ns in ding terms. GERN SACK matics showing various types of circuits found in the more common TV receivers. 96 PAGES 82 ILLUSTRATIONS -RFS.

TELEVISION AND FM RECEIVER SERVIC- Only 75c ING. by Milton S. Kiver. Published by D. Van LiBRARY Nostrand Co., Inc. Paper covers. 81/2 x II inches, 212 Price $2.95. See your jobber Indas tt send for PRACTICAL DISC pages. RECORDING: along r with other titles in the This is a practical treatment of tele- GERNSBACK LIBRARY. vision and FM receiver servicing theory and practice prepared by the author of Television Simplified and FM Simplified. r -- MAIL THIS COUPON NOW - -- The first chapter covers v.h.f. antenna systems, their characteristics and in- RADCRAFT PUBLICATIONS, Dept. 117 10 OTHER BOOKS -50g EACH 25 West Broadway. New York 7, N. Y. stallation methods. Design data is given No. 29-Mandy Kink - No. 3a- Radin -Flee. Send nie the books tpostpaidI eneeked. - and Short Cuts ironic Circuits on several types of FM and TV an- NO. 39- PRACTICAL DISC RECORDING No. 30- Unusual Pat- No. tennas and a number of commercial 75c ented Circuits 3.5- Amateur Radio Builder's Guide systems are illustrated and described. I tarloia t No. 31 -Radio Ques. tiens and An- O No. 36-R ad i o Test The next eight chapters are devoted en- our Nana swers Instruments tirely to television receiver servicing. (Print rlcarly) I G No. 32 -A d v a ne ed G No. Elementary S I I1 ass Service Tech 37- Ra- Equipment required for servicing is de- nique dio Servicing luhher's Natile scribed and illustrated with block dia- C No. 33-A m p I i 0 e r O Na. 38 -How to Build grams and simplified schematics. Pic- h . Builder's Guide Radio Receiver, tures of test patterns show the effects RADIO -CRAFT for Book Reviews of various ty pes of interference and maladjustment within the set. BOTH BOOKS The last four chapters cover FM PLEASE TEAR OUT fundamentals, typical commercial FM FREE receiver circuits, and aligning and ser- THIS ADV. AS REMINDER vicing FM receivers. This book will prove useful to TV and FM service technicians, particularly cmnpete INDEX ro when manufacturer's servicing data is .Moe - fan - Needed not available.- R.F.S. RADIO ELEMENTARY INDUSTRIAL ELECTRONICS. DIAGRAMS by William R. Wellman. Published by D. Van Noatrand Co.. Inc. 6% Jr 9% inches, 372 pages. Price $3.20. Those persons interested in electronic tubes and their industrial applications, will find this book informative and easy to read. It has been prepared for students, maintenance engineers and workers in allied fields who desire a basic FREE t reader of Radio -Craft. No strings. saubi r 11, w t'. (se Diagrames" gives hints. .shoe r the u of diagrams i rnrllo s "'I' je knowledge of electronics. fudo,errt INDEX will tell you Just what models 'r:are in- Among the devices and theories de- .lu.lyd ,. .t I llt I'II retina- nnrn.Ncr ,lrl Radio Di:r scribed are: a.c. fundamentals, basic r.,.,ks in - ,n-1 principles of vacuum tubes, gas -filled SUPREME PUBLICATIONS is Ave. tubes, industrial applications of keno- Chs. Kedl trons, applications of hot -cathode gas - type rectifiers, mercury -pool rectifiers, vacuum -tube amplifiers, industrial high NOW -A REALLY HIGH-POWERED - frequency heating, electronic control of RADIO FACTS motors and generators, electronic con- AND FIGURES trol of resistance welding, photoelectric Radio Engineering 1001 AUDELS RADIOMANS GUIDE- 914 Popes, 633 Muss devices, and electronic lamps. trotions, Photos, Wiring Diagrams, 38 Big Chapters, covering Radio Theory, Construction, Servicing, includ- The reader will appreciate the care- Library ing Important Data on Developments In Television, fully worded descriptions of the actions Electronics and Frequency Modulation, Review, Questions and Answers, Calculations & Testing, occuring in various types of tubes, to- Highly Endorsed-. Indispensable for Ready Reference gether with the clear diagrams. A chap- and Nome Study, ter is devoted to electronic symbols and S4 COMPLETE PAY ONLY S1 A MONTH Step up your own skill with the facts and figures of terms, suitably illustrated. The section your trade. Auricle Mechanics Guides contain Prac- tical Inside Trade Information In a handy form. on kenotrons and hot -cathode gas -filled Fully Illustrated and Easy to Understand. Highly Endorsed. ('heck the book you want rot 7 days' rectifiers includes diagrams of thyra- Free Examination. tron battery chargers and a thyraton The Library r. 1, s a selection Send No Money. Nothing to pay postman. of books rullul limn leading Mc- inverter. All types of v.t. amplifiers are Graw -Hill publications in the rare- --- CUT HERE - -'- described, with circuit diagrams. The din field. growing use of high frequency heating rsperi tc //g elected by radio specialists of .1 /- MAIL ORDER Grow-/ /ill publications NEW rORK for industrial purposes makes this sec- to gier Prost complete, dependable coverage of AU 13 EL, Publishors,49 W. 23 St., ao. tion particularly useful. farts nccded by all whose fields are grounded on Please send me POetpid for FREE EXAMINATION book, radio fundamentals erked , below.11 I decade to keep them 1 to The chapter on electronic lamps cov- available at a special price and terms mail SE In 7 Days on each book oreeled and runner mall Si monthly on each book until I have paid price ers many details scarcely ever men- THESE books cover circuit phenomena, tube the- -0thersnse. I will return them. ory. networks, measurements. and other sub- tioned in the average book on electron- RADIOMANS GUIDE. 914 Pages . . . $4 jtels -rive specialized treatments of all fields of ELECERICIANS EXAMINATIONS, 250 Pages , 1 ics. Different types of electronic lamps practical design and application. They are book- WIRING DIAGRAMS. 210 Pages 1 discussed are glow lamps of the argon of recognized position in the literature -books you ELECTRIC MOTOR GUIDE 1000 Pages , . 4 will refer to and be referred to often. If you ELECTRICAL DICTIONARY, 9000 Terms . 2 and neon types, neon lighting tubes, are a practical designer. researcher or engineer ELECTRICAL POWER CALCULATIONS, 425 Pgs. 2 sodium vapor lamps, high- intensity mer- in any field based on radio. you want these books HANDY BOOK OF ELECTRICITY. 1440 Pages 4 for the help they give in hundreds of problems ELECTRONIC DEVICES 216 Pages 2 cury vapor lamps, fluorescent lamps and throughout the whole field of radio engineering. ELECTRIC LIBRARY. 12 vol., 7000 Pgs., $1.50 vol. their characteristics, and the high -in- 5 VOLUMES, 3319 PAGES, 2289 ILLUSTRATIONS OIL BURNER GUIDE, 384 Pages . I REFRIGERATION & Air Conditioning, 1280 PCs. 4 lamp. A series of I. Eastman's FUNDAMENTALS OF VACUUM TUBES tensity photoflash 2. Terman's RADIO ENGINEERING POWER PLANT ENGINEERS Guide.1500 Pages. 4 questions and references are given at 3. Everitt's COMMUNICATION ENGINEERING PUMPS, Hydraulics &Air Compressors, 1658 Pgs. 4 4. Hand's HIGH FREQUENCY MEASUREMENTS WELDERS GUIDE. 100 Pages 1 the end of each chapter. A suitable in- 5. Henneys RADIO ENGINEERING HANDBOOK BLUE PRINT READING, 416 Pages 2 H.IV.S. In da, u e:a.s leile Special prat de,r SHEET METAL WORKERS Handy Book. 388 Pgs 1 dex completes the work.- Uri otter s, i,Man ,,(s b, h, s separately. «t i antI standard took, n r library v, fir hly SHEET METAL PATTERN LAYOUTS, 1100 Pgs. 4 a Inn while s the hooks. AIRCRAFT WORKER. 240 Pages . 1 RADAR, What Radar Is and How It Works 10 DATA FREE EXAMINATION -SENO COUPON MATHEMATICS & CALCULAI IONS, 700 Pgs 2 (Revised Edition), by Orrin E. Dunlap, Jr. Pub- MACHINISTS Handy Book. 1600 Pages 4 MECHANICAL Dictionaryy, 968 Pages 4 lished by Harper & Brothers. 5_r x 8% inches, McGraw -Hill Book Co., Inc. 330 W. 42nd St., N.Y. C. 10 268 pages. Price $3.00. AUTOMOBILE GUIDE, 1700 Pages 4 Send had lo Ens, ,nrenIn:: Library. I... for In DIESEL ENGINE MANUAL, 400 Pages 2 ,lays xmt1 tu, Nrnsat. lii Ili Mies 1 rill send This is a book for the layman who has 3:,11. plus few' rents 'I postage. and 11.5.00 monthly till MARINE ENGINEERS Handy Book, 1280 Pages 4 $17.50 is return pay MECHANICAL DRAWING GUIDE, 160 Pages . I no technical background but still would rdrsa mean ied by remittance of s the frsin-to ament.i el. MECHANICAL DRAWING & DESIGN, 480 Pgs. 2 like to know how radar works. MILLWRIGHTS & Mechanics Guide, 1200 Pgs. 4 The author writes in a clear and in- Name CARPENTERS & Builders Guides (4 vols.). . 6 PLUMBERS & Steamfilters Guides (4 vols.) . 6 teresting style and begins with the Address MASONS & Builders Guides (4 vols.) . , 6 MASTER PAINTER & DECORATOR, 320 Pgs. 2 early inventions that led to the final de- & GROWERS GUIDES City and State GARDENERS (4 vols.) 6 velopment of radar as we know it today. ENGINEERS and Mechanics Guides 1, 3. 4, 5, 6, 7 and 8 complete in- Company Nos. 2, 12 Photos of radar apparatus and the Answers on Practical ENGINEERING 1 ventors who helped to perfect it are in- ENGINEERS & FIREMANS EXAMINATIONS . I PosDlon n .a.18 8 cluded in the work. Many of the amazing feats performed by radar during the the time required for the echo to be re- Na e war are described. The later chapters ceived when the wave is reflected by a Address deal with post-war applications of ra- ship. plane or other object, is clearly dar, the development of Teleran, Shoran, explained. If you have not kept up to Occupation B.C.F. G.C.A. radar, and other systems. date on the many applications and im- Employed by The simple method of sending out proved forms of radar, this book will pulses of radio energy and measuring acquaint you with them.-H.W.S. SEPTEMBER, 1948 RCA INSTITUTES, Inc. URer thorough training RADIO SCHOOL DIRECTORY courses in all technical phases of Radio and Television DAYS-EVENINGS WEEKLY .ATES VETERANS: RCA Institutes is approved under G. I. Bill of Rights For Free Catalog Write Dept. RC48 PRACTICAL TECHNICAL TRAINING RCA INSTITUTES, Inc. .t Service of Radio Corporation of America 350 WEST ITH STREET NEW YORK 14, N. Y. 2nQClll3¢ IN RADIO, ELECTRONICS ELECTRICAL ENGINEERING TA CAREER WITH A FUTURE! COURSES Prepare for a sut'Ccssful career in in- SERVICE ELF.V-ISill:NI 6 to 12 Months dustry or a business of your own in 6 SHOP Molt A npaosti lawn Electricity lullt I4ucele Thale mini Welding months to 3 years. More than 35,000 for - It.: Inxi It.%11110 %ERLE II E A ItE1'.\I It iatriElectricalral F. Refrigeration mer students in industry the world over. Engineering M. . TFI.FI INIli Heating with Major in Tit.% \SMITTEIN 1111 IIE 1,538 students Prepense lo, E.C.C. LICENSES TECHNICIAN now enrolled from 48 states Flsewenia In 3 Years. 11.11110 TECH 01.01:1 I to 2 Years and 13 overseas countries. Faculty of 72 Electricity aatNING - arriano. WIDOW CUSSES ahmten um Mimi/men Radio specialists. Write for Catalog and Per - AVAILABLE UNDER G. I. BILL Electronics conal Guidance Questionnaire. Refrigeration, Hearing II IE 1.1? 1111TY SCHOOL OF and Air Conditioning Terms start September, January, April, RADIO ELECTRONICS TELEVISION PROFESSIONAL July. 105 EAST 13th STREET, NEW YORK 3, N. Y. DEPT.R 3 Years LICENSED BY STATE OF NEW YORE Electrical Engineering Bachelor of Science MILWAUK££i1". Degree ENCINEERIN/ Machinery or CHI= of A Intuitole F nundrd 19113 RADIO Technical Electronics 5 TECHNICIAN and RADIO SERVICE COURSES J Dept. RC -948 North Broadway, Milwaukee, Wisconsin FM and TELEVISION AMERICAN RADIO INSTITUTE loi West 63rd St.. New York 23. New York Approved tinder GI Bill of Rights LEARN RADIO! L r nerd !,u New York State WANTED: IN ONLY 10 MONTHS Men and Women to Fill PREPARE FOR A GOOD JOB! COMMERCIAL OPERATOR (CODE) BROADCAST ENGINEER R- ADIO C OURSES TOP RADIO JOBS RADIO SERVICEMAN RADIO OPERATING CODE Television RADIO SERVICING in AM- FM- Television Servicing-15 Months F.M. TELEV ISIÓ NLECTRONICS If you are Lei:- t.rr a carver with a future. why not REFRIGERATION SERVICING join the humes.., of graduates from the Don Martin Veterans get 5130.00 Equipment Write for Catalog and Picture Brochure School of Radio arts now successfully employed in the SEND FOR FREE LITERATURE radio industry. The demand is great for qualified Y.M.C.A. TRADE A TECHNICAL radio in AM -FM- Television. Train now to SCHOOLS/ personnel BALTIMORE TECHNICAL INSTITUTE 15 be an ter script writer, disk jockey. news W. 63rd St. (N'r B'way) New York City caster, o indio technician. Complete day and night 1425 Eutaw Place, Dept. C. Baltimore 17. Md classes the Chest enunnnent. Fret placement / service. Approved for veterans. Write for free booklet. Don Martin School of Radio Arts S,s/ORT 1655 North Cherokee St. Hollywood 28. 4fir Calif. FM- RADIO -TV PRACTICAL 2 Re an Expert tu Radio Thousands of TRAINING ' fed. Intensely intereatin' l'ntr fully -equipped laboratories provide the 'e. w pay. Learn at ho - wherever w . l'IIACTICAL training essential for Emceess(1d RRCC BOOK quickly easily. RADIO ENGINEERING iieers with the famous Candler Code speed in Radio Communications I FCC li- amateur or commercial license. Book noes) and in Radio- Television Servicing Television -Broadcast Technicianl. CANDLER SYSTEM CO. FM- Train under the supervision of Dept. 3 -K, Boa 9YN, Denver 1, Colo. r r . Radio. Marine Radio, Rodio Finical specialists with commercial -type mobile - Radio and Ultra High equipment. Investigate why WRCI SPECIAL - in all branches of Rein, :ut I 'lrr,noueh training IZED TRAINING methods are outstanding; 'tonics. Malern laboratories and euuipmrut. Old why WRCI t.iblished school. Ample housing lactlll i es. 7 a. laboratory- trained specialists are THIS COUPON MAY PROVE ampus. Small classes. enrollments limited. Out in demand. Read our illustrated bulletin be- graduates are in demand. Write for catalog. fore enrolling in any school. Approved for TO BE THE KEY TO YOUR Approved for Veterana veteran training- non -veterans accepted. Send for free SUCCESS IN ELECTRONICS VALPARAISO TECHNICAL INSTITUTE copy of Bulletin -M today. Deut. C VALPARAISO, INDIANA Western Radio Communications Institute MELVILLE RADIO INSTITUTE Specialists in Radio -Electronics Training 341 West 18th Street, Los Angeles 15, Calif. The Progressive Rodio School Managed by Radio Men Licensed by the N. Y. Stale Beard et 'Education Complete Radio Engineering RECOGNIZED BY INDUSTRY Couve. Bachelor of Science De- APPROVED'FOR VETERANS gree. Courses also in Civil, Elec- trical. Mechanical, Chemical, Aeronautical Engi- neering: Business Administration. Accounting, CIT IT CITI FILL IT GOTI MAIL IT 0ÚT1- NOWT Secretarial Science. Graduates successful. 65th year. Enter Sept., Jan., March. June. Write for I MELVILLE RADIO INSTITUTE RC catalog. I Melville Bldg., 15 W. 461h St. , N. Y 19. N. Y. ceu.INDIíAiNA TRI-STATE COLLEGE 'teas 1 Send me without obligation information oboist Preparatory, Service, Broad- your intensive courses: cast, Television, Marine I Op- Rodio Technician CORRESPONDENCE COURSES IN erating, Aeronautical, Fre- I Radio & Television Servicing RADIO and ELECTRICAL ENGINEERING quency Modulation, Radar. I Radio Communications ENGINEERING g."= Classes forming for Tall term Oct. 1. ELECTRICAL :,de jja ée,T 1 Fundamental Radio Mathematics Prepare our,ef aat too et. for secure future.tu Entrance course ; understand e'. Modern exam Sept. 20. I My Noms RADIO ENGINEERING Wel1e aadrM anote-°a " eleetrie Veterans. Literature. ruark. Train you to be super- aerelw man. teal vacuum. ne technician. Servicemen needed badly. Diploma COMMERCIAL RADIO INSTITUTE I Address m lotion Many graduates earning Dag pry. (Founded 1920) Send postcard for Fee Copley of Eitnef 35 West Biddle Street, Baltimore 1, Md. I II WRITE d «::i ,. ;en° $15 Curse Lincoln Engineering School, nos 331-C115. Lincoln 2. Nose. L======RADIO -CRAFT for Communications 97

THE TABLE OF CONTENTS Dear Editor: The Table of Contents in RADIO -CRAFT is almost invariably on page 10. That is inconvenient for the newsstand buyer, who may want to see what's in the magazine before he buys it. It's also a nuis- to owner of back issues when he ance the ABSOLUTELY NO KNOWLEDGE OF RADIO NECESSARY tries to find an article and has to thumb through 9 pages of advertising before YOU NEED NO ADDITIONAL PARTS! finding the contents page. THE PROGRESSIVE RADIO KIT is the ONLY COMPLETE KIT How about putting the Table of Con- Operates on 110-120 volts trol -grid modulation. Both vacuum tube and tents on page 2? That will save much ACIDC. Contains every- selenium rectification are employed in these wear and tear on the fingertips and the thing you need. Instruction Book, Metal circuits. The circuits are designed to provide temper! Chassis, Tubes, Condensers, Resistors and all excellent performance. Altogether, fifteen cir- other necessary radio parts. The 36 -page In- cuits are constructed, including 11 receivers, NATE SILVERMAN, struction Book written by expert radio in- 1 audio amplifier, and 3 transmitters. The Los Angeles, Calif. structors and engineers teaches you to build sets start with simple circuits of 1 tube plus radios in a professional manner. The first rectifier, gradually grow more complex, and (Turn to the second page of this circuit built is a simple one -tube detector finish with several examples of radio sets issue and take a look. You'll find the receiver. Each succeeding circuit incorporates using three tubes plus rectifier. Table of Contents there! Mechanical new arrangements of detectors. RF and AF PROGRESSIVE RADIO KIT -ONLY $14.75 printing difficulties have long prevented amplifiers. This kit is excellent for learning of receiver, our putting on the second page but the principles transmitter and it amplifier design. It is used in many radio SPECIAL FREE OFFER from this month on, readers will be able schools colleges. All of the commonly- and Electrical n.1 Radio 'I. to find out what's in RADIO -CRAFT with- used detectors are used, including diode, grid with each rm :r, iv.. Irr.hin l'mgnsslve 16,án, 1.11 out any trouble. -Editor) leak, plate and infinite -impedance. The trans - free ancra advice and consultation mitters are designed with Hartley and Arm- reused radin 1 .,Wens for further 1111.1. or enter yourn, KIT NOW! MORE SERVICE ARTICLES strong oscillators, using screen -grid and con- Dear Editor: WE PAY POSTAGE ON PREPAID ORDERS C.O.D. ORDERS SHIPPED COLLECT I have followed RADIO -CRAFT for about as long as it has been published. I enjoy the April Fool stories such as Fips' Tubeless Homo- Heteradia (RADIO - ATTENTION RADIOMEN!! CRAFT, April, 1948) as well as the technical items. Progressive's new DEALER'S CATALOGUE is just off the preSS There has been a lot of talk about a RADIO KITS PORTABLE RADIOS paper shortage which is forcing magazines to limit their size. In common, I AMPLIFIER KITS CAMERA -RADIOS think, with most readers. I approve of light material like the Fips article occa- FM COIL & CONDENSER KITS TUBES sionally, but my interest in radio makes RESISTOR KITS AUTO RADIOS me wish that instead of printing letters from readers who try to tell taller and CONDENSER KITS HOME RADIOS space taller stories, you would use the RADIO TOOL KITS TELEVISION SETS for radio articles. I think, too, that you give too much FM -AM CHASSIS TELEVISION CABINETS space in the Teehnotes department to re- SPEAKERS TEST EQUIPMENT ports on very familiar troubles and very rare cases that are not likely to happen RADIO PARTS FM TUNERS again. I would like to see that space used for more good articles on modern SEND FOR YOUR FREE DEALER'S CATALOG servicing methods. AND PRICE LIST TODAY! ROBERT F. STONES, Daytona Beach, Fla. PROGRESSIVE ELECTRONICS CO. BEST CRYSTAL CIRCUIT DEPT. RC -17 497 UNION AVE BROOKLN 11, N. Y. Dear Editor: Spain, in the December, 1946, RADIO - CRAFT, gave crystal enthusiasts about as good a receiver as can be put together Hollywood Make Good in at Experts without using expensive parts. After I orne tried it for three months in competition Help You RADIO -TELEVISION H TELEVISION 1948!! fr. ,.,I, of 1 a.lr. Tete. (RADIO - that IC.. ndrry vitre a .T -AF times with the "Loud" Crystal Radio Train at an Institute pioneered en 11d tested home training.` Her 'at last -easy to hou that irkly mil ties you for CRAFT, September, 1945) and the Mod- in TELEVISION TRAINING since 1938. adY. gm,dpny 'lobs or your n Haut,,, business. 10 big (RADIO -CRAFT, Morning, Afternoon or Evening Ses- lis of radio parts given at no entra charge. Get full de- ern Midget Set January, ., I. t once! I postal for FREE GOOK Mow to Make sions in laboratory and theoretical in- ,.''od In Radto.Telrvl.ion..' 1948) I give it my medal for superior- struction, of under guidance experts, RADIO TRAINING ASSN OF AMERICA, Peet. RCM ity. covering all phases of Radio, Fre- 5620 Hollywood lvd. Hollywood aa, Calif. quency Modulation, Television, lead All the sets were compared using the to opportunities in Industry, Broad- same components except casting or own Business. Licensed by for the capaci- N. Y. State. Approved for Veterans. tors. The coils were carefully trimmed ENROLL NOW FOR NEW CLASSES SOUND RECORDING SCHOOL for best results. Visit, Write er Phone A practical eneureeliug +I ,dal Fvndan anal.. Recording. and Sound 'h.ur nd s By the way, I am using the same a laboratory nitaining transmission nets. oseillapn.. RADIO- TELEVISION square nase generator and Inlermalulatlnn analyzer, and galenas as when I started making crys- other egnlPment. Completo cording studio assimilating broadcast. motion tal receivers in 1920! INSTITUTE picture nde commercial sound ruvrdMlg, under the direc- 480 Lexington Ave., N.Y. 17 (46th St) tion of I1. M.Tren.a ire. G. S. ROBERTSON, ' Plaza 3-4595 2 blocks from Grand Central HOLLYWOOD SOUND INSTITUTE, Inc. Montreal, Canada 1040 -C No. Kenmore NNlywsad 27. Gllf- SEPTEMBER 1948 98

aPPvRnNm AD-LETS Index To Advertisers Advertisements in this section cost 25c a word for each Insertion. Name, address and initials must be included at the above rate. Cash should accompany Abell Dist. Co. 81 all classified advertisements unless placed by an Acorn Electronics Corp 73 accredited advertising agency. No advertisement for Air King 6 loss than ten words accepted. Ten percent discount Allied Radio Corporation 55 issues, twenty percent for twelve issues. Obier- Almo Radio Anable or misleading advertisements not accepted. Co 72 sit era Isements for Ortober, 1948, issue must reach Alvaradio Supply Co 93 ms later than August 24. 1948. American Sales Company 86 Radio -Craft 25 W. Byway New York 7. N. Y. American Surplus Products Co. I6. IB Amplifier Corp. of America 64, 72, 73, 80 A. M. Radio Sales Company 79 S}LECTED GROUP OF MEN. GRADUATES OF WELL- Walter Ash. Radio Co. 86 known trade school, desire employment in Radio Field, Audel Will Publishers 95 travel anywhere. Qualified in radio servicing. instal- Bell Telephone lation. test instruments. circuit aeration, etc. Contact Labs. 8 Placement Dept.. Eastern Technical School. 888 Purchase Boland and Boyce Publishers, Inc. 67, 70 Street, New Itedford.atase. Brooks Radio Distributing Co. 47 MAGAZINES IIIA(K DATEDI- FOREIGN, DOSIESTIC. Buffalo Radio Supply . .. 74, BI, 83, 87, 88, 90, 92, 93 arts. Boots. booklets, subscriptions. pin -ups. etc. Cata- BursteinApplebee Co. log lue (refunded). Cicerone's, 863 First Ave., New Capitol Radio Eng. Inst. York 17, N. Y. 5 53 Certified Television Laboratories 64 YOU CAN ACCURATELY ALIGN SUPERHETERODYNE Cleveland Inst. of Radio 15 receivers without signal generator. Complete instructions Clippard Instrument Laboratory, Inc Broadcast El. Moneyback guarantee. Chas. Gates. l'ecos 2, Texas. 82 Combination Commercial Radio 92 LANCASTER. ALLR-INE A ROMMEL. 436 IBOWEN Communications Equipment Co. Building. Washington 5, D.C. Registered Patent Attorneys. 57 Intercom System Coyne Electrical School 88 Receiver & Practice before United States Patent Office. Validity and Coyne Electrical infrngement Investigations and Opinions. Booklet and School 93 Price includes BRAND NEW form "Evidence of Conception" forwarded upon request. Custom -Graff Mfg. Co. 93 DeForest's Training Institute radio -master AMATEUR RADIO LICENSES. COMPLETE THEORY 13 for examinations. Electrdnic Measurements Corp 64 station, I Electronic Research Labs. $29.95 drar resientcoures..Ìinsei American a Ra ÌÌoo Iitstuyand IO Mil N'est 63rd St.. New See our ad Espey Mfg. Co., remote, & 50 LIMITED York City. ce l'aga 96. Inc. 10 Esse Radio Co. wire QUANTIIT NEW CARTONLD RADIO TUBES 39c. WRITE FOR 14 ft. of bargain catalog. llenshaw Radio. 3313 Delavan, Kansas Fair Radio 72 City. Kansas. General broadcast (6 tube superhet) re- Cement Mfg. Co. 91 Standard WE REPAIR ALL TYPES OF ELECTRICAL INSTRU- General Electronic Dist. Co. 49, 91 ceiver, plus home or office intercommunica- menls, tube checkers and analyzers, Hazeltor Instrument General Test Equipment 93 Co. (Electric Meter Laboratory). 140 Liberty Street, New finish, modern design Greylock Electronic Supply Co. 90 tion system, walnut York, N. Y. Telephone- BAreIay 7.4239. Hallmark Electronic model; high quality components; Corp. 93 table RADIOMEN. SERVICEMEN. BEGINNERS - MAKE Hawkins Radio 72 more money. easily, quickly. ekly We uses one to four remote stations. Any $250 possible. The Heath Company 76, 77 show you how. Information free. Merit Products, 216 -32L Hershel Radio Co. station can call the master while radio is 132nd Avenue, Springfield Gardens 13. New York. 65 Hickok Electrical Instrument Co 87 playing; call can be returned to any re- BRITAIN'S FOREMOST RADIO 'MONTHLY, PRAC- Hudson Specialties 92 TICAL WIRELESS, sent all over world to "hams" Inter- mote. 115 v. AC; original list was $84.50 Instructograph Co. 75 ested European radio developments. Leading technician, Lafayette Radio (with 4 remotes). Additional remote describe new British ideas and much val nabis ads ire 51 published for both amateur and expert. Indispensable to Leotone Radio Corp. 64 stations, $3.95 each. the keen serviceman enthusiast who wants to "keep ahead" McGraw -Hill Book Co., Inc. 95 W for all DX "hams" who listen otit a , ss Atlantic. P. R. Mallory R Co., Inc. Inside Front Cover For annual subscription mailed direct from r London. send Maritime Switchboard 89 $2.1111 Newnes only to George Ltd. I t'Y.'. Ili. 312 Madison Metropolitan Anmw, New York 17. Elec. d Inst. Co. 84 MidAmerica Co. II SUITCASE SIZE RADIO SHOT- IIUILU IT ANIS Midwest Radio and Television Corp 19 ST. Dept. RC-98 reap huge profits. Free literature. write; Grand Federal. Moss 1426 N. QUINCY 3516 1Voouiend. Kansas City 3. Kansas. Electronic Distributing Co. 85 Murray Hill Books, Inc. A R L I N G T O N , V I R G I N I A 83 National Radio Inst. 3 National Schools 7 Niagara Radio Supply Co. 61 Offenbach i Reimus Co. 74 Opportunity Adlets 98 Precision Apparatus Co. 86 Progressive Electronics Co. 97 EXCITING! BARSIN Radw- Coin -Matic 88 Radio Corporation of America 59 Radio -Craft 71, 94 ßr7 25 to 40 WATTS Radio Dealers Supply Co. 78 Radio Kits Co. 84 10 to 80 METERS FOUNDATION KIT Radionic Equipment Co. 82

RADIO SCHOOL DIRECTORY (Pages 96.97) American Radio Institute Engineered around the BC -010 series of plug -in tuning units. Described in the 11th edition Radio Baltimore Technical Institute Handbook. Completed exciter uses 6AG7 Crystal Candler System Co. or electron coupled oscillator, 6L6 buffer -doubler Commercial Radio Institute and 807 amplifier. Kit includes four tuning units (illustrated at right above with cover removed l, 71i(ASTEKPIECES Deiehanfy Institute speciol 51/4" aluminum relay rock panel, socket Don Martin School of Radio Arts for plug -in units and special hordware, together /11 in ('ARINETItI- with full instructions and diagrams for assem- Television cabinets yperla I Iy ' n t: i nee re d for Hollywood Sound Inst., Inc. bling complete exciter. 12" and 15" Standard rund DeI L.u.xe' "Trans- Lincoln Engineering School 1 7 e No. A28, FU -40 Foundation-, Spec. .9 95J vision" models. Also available for 12" and 15" Melville Radio Institute Standard and Champion "Television Assem- PARTS KIT. Everything needed to complete ex- I'v' models. Exclusively designed tubés to Milwaukee School of Engineering citer except tubes and power supply. Includes match. Various finishes. Write for ptartieu- Radio Television Institute oll mica condensors, resistors, RF chokes, sockets, (:ors, Dept. R. meter switch, O -200 ma meter, key jack, and Radio Training Assoc. of America miscellaneous parts. 931 TEL COJIPANI' RCA Institutes No. 31A28A, Special Per Kit, Each elm Havemiyer St., Brooklyn I I. N. Y. Tri -State College DID YOU GET ITT Valparaiso Technical Institute THE BIG B -A 1948 Catalog No. 481 - Western Radio Communications Inst. Everything in Radio and Electronics. Write MAKE MORE MONEY YMCA Trade and Technical Schools if you hove not receicved it. FREE on request. 91.011 VALUE In "1' \511 IN" Top pmt p,I THE real money. Radio Supply i Engineering Co. 68 makers ,li,catis .d Ravac Electronics Corp. 86 tiri,iii able seated moil 90 er pions. ,v infbleut lad Risco Electronics ENSTRIVAPPLOLID Rose 92 WOVE s/IIfEr. 25c tallans ties sort Ie. duzen.. The Co. 1012'4 4 ma,Gea tested mt- R. B M. Radio Co. 98 KANSAS WY R. MISSOURI ledllas, ssful teat Howard W. Sams 6 Co., Inc. 75, Inside Back Cover 40,000 schemes actual r Sanco Radio, Inc. 12 rar r who WORDS iriroves N. Silverstine 89 .taped on .1 shoe- IN than Simpson Electric Co. Back Cover RADIO -CRAFT needs more photos of ;fin capital 23e copy Solar Capacitor Sales Corp. 4 TEXT postpaid. Send U.U. Sprague Products Company 20 service shops and service benches. We stamps, money order, or Sprayberry Academy of Radio 9 coin. will pay $6.00 for each 6x8- or 8x10 -inch NO ADS Supreme Publications 95 glossy photo accepted. Do not "dress up" ALL Money Back Surplus Radio, Inc. 80 Sylvania Electric Products, Inc. 17 your bench, but take a bona -fide photo, "MEAT"!', Guarantee Technical Radio Parts Co. 74 preferably with men working. NATIONAL PLANS COMPANY Tel -Craft Co. 98 Bag 26RA, Ansonia Station New York 23. N. Y. Transvision 69, 81

I 4 8 Printed in the U. S. A. RADIO -CRAFT for SEPTEMBER. 9 «saes' apsut SOWS owes,« + Domo ou«ots WNW, ac

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