Radio-Craft-1947-Feb

GERNSBACK,Edifor

Teleuísíon Sound Receiver

Instability in Apparatus

A Small Recording Studio

RADIO -ELECTRONICS IN ALL ITS PHASES www.americanradiohistory.com Model 315 Signal Generator. Designed down to the most V minute derail for highest ac. curacy, greatest stability, minimum leakage, and good wave form $67.35 a real Model 305 Tube Tester Tests ... gives servicemen all tubes. Provides for filament voltages from .5 volts to and in. cluding 120 volts. Spare sockets for profit- making set -up future tube developments....149.50 Model 260 High Sensitivity Set The successful radio serviceman today must have the finest in test instru- Tester. 20,000 ohms per volt. D.C. ments a very reason his only hope of present and con- Voltage ranges to 5.000 volts A.C. for practical -that's and D.C. Resistance ranges to 20 tinued profits. To meet the tremendous volume of business available he megohms. Current ranges to 500 mil- must be able to "trouble-shoot" fast and accurately every time. Only thus liamperes 531.95 can he correct trouble speedily, with satisfaction to the customers. Simpson offers you, in three basic test instruments, the accuracy and advanced electronic engineering which have given Simpson the proudest name in the industry. They are tried -and- tested examples of the kind of instruments Simpson has always built. Their use will demonstrate that from Simpson alone can you expect "instruments that stay accurate" with construction and design that lead the field. To dealer and to serviceman alike, Simpson offers today the assurance of continued profits that only quality can give. No Simpson instrument is ever marketed, or ever will be, unless its makers feel that. o of its kind, nothing finer can be produced.

S I M P S O N E L E C T R I C C O M P A N Y 5200-5218 West Kinzie Street, Chicago 44

I N S T R U M E N T S T H A T S T A Y A U R A T E r

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J. E. SMITH. PRESIDENT RADIO SERVICE BUSINESS National Radio Institute E7rd Year of Training Ned fer success In Radio WITHOUT CAPITAL tf; APPROVED The men at the right are just a few of many I have trained. at home n vC '.q in their spare time, to be Radio Lodi. Technicians. They are now operating You G.I.BILL their own successful spare -time or Build These and Many full -time Radio businesses. Hundreds of other men I trained hold good jobs Other Radio Circuits with in practically every branch of Radio. Doesn't this PROVE my "60 -60 method" of home training can give you BOTH a thorough knowledge Big Kits of Parts 1 Supply of Radio principles and the PRACTICAL ex- tbn+f bua1ncás perience you need to help make more money rO tfine Bad you tralningnlprogsaóof my °w+ad EIM. By the time you've in the feet- growing Radio industry? due conducted 60 sets of L+et ear ratelrpd to hico. hag Experiments with Radio Parts I supply, Let one send you facts about opportunities $a th made hundreds of measurements and ad- in the busy Radio field. See how knowing Radio pg, ß$(Sed °ymiSÓ Courget justments, you'll have valuable PRACTI- can give you security, a prosperous future , . . Bo+t,r CAL Radio experience lead to jobs coming in Television, am dofs Nw- for a good full or Electronics, 7me. part -time Radio job! Send coupon NOW for FREE Sample Lesson and 0ná r+dlo wo and 64-page, illustrated book. Read how NRI pboubf trains you at home in spare time. Read how Calelry&Inlylam grj d Óby, A1 you practice building. testing, repairing Ra- Chasoley. 1 with NortDa7 ;dND Ét¡: ' dios BIG KITS of Radio parts I send you. "u21' " Many Beginners Soon Make Extra Money In Spare Time While Looming am tBd¡+laklnmonths aftor ' The day you enroll I start sending EXTRA IDoK°arrlln MONEY JOB SHEETS. You LEARN Radio mee atnggaandrat0141u rad2t BENN¡p°rlJ gy,' principles from my easy-to-understand, illus- M FGOÓ 7llatonb rat Iq aoder, lñ ht trated lessons- PRACTICE what you learn by low¿ ABENDg Ry,11a)et oae building, testing and experimenting with parta I send -USE your knowledge to make EXTRA money fixing neighbors' Radios in snare time while still learning! From here its a short step to your own full -time Radio Shop or a good Radio job! Future for Trained Men Is Bright In Radio, Television, Electronics It's probably easier to get started in Radio now than ever before. because the Radio Re- pair Business is booming. Trained Radio Tech- You build the nicians also find 'No( SUPERHETERO- profitable opportunities in long e DYNE CIRCUIT Police, Aviation, Marine Radio, Broadcasting, Now above containing Radio Manufacturing. Public Address work. at.,760°":1eng a¡atlorw, ikst !6 preselector oscWator- Think of even greater opportunities as Tele- course os radio pull + we,t mixer -erst detector. vision. FM. and many nets, war -developed TFT a en week rit ces You build MEASUR- 1.f. stage, diode -de- Electronic devices become gam. ]39.lOth T Cho171BÁ+Ì ING INSTRUMENT tector-a.v.c. stage and available to the pub- dänó lic I Soon, will +. Sldne,. above audio stage. will there be more Radio equipment Nap, early in It to install. operate. maintain and repair than l° Course. useful for bring in local and over aloug aalÍl Radio work to pick UD distant stations. Get before in all history! Get the facts on all g f the these opportunities. Send g Dor EXTRA spare time thrill of learning for FREE books nowl a p. radi money. It L a vacu- at home evenings in er.. -ï'gad oft a'fratewár s,l+ +hard um tube multimeter. spare timo while you Find Out What NRI Can Do for,You Ava, gt.a4rig,RÌVwfoúntliLSY76i40o1f measures A.C.. D.C.. Dut the set through Mail Coupon ter. Sample Lesson. "Getting Newfoundland R.F. volts, D.C. cur- fascinatheg tain Acquainted rents, resistance,, re- with Receiver Servicing," and my FREE 64 -page book. Its packed with facts 1 ceiver output. about making Radio's opportunities for you. Read the MY over Building the A. M. details about my Course. Read letters from men I trained. men «h jet hoes. SIGNAL GENERA- telling what they are doing. earn- bec¿áße aros¡ :e2lG TOR at right will give ing. See how quickly, easily you can get start- MdN dflyLE$they ke ¡p sradu- 8okon rNa'ra NOB.f you valuable experi- ed. No obligation I Just MAIL COUPON NOW . ence. Provides ampli- in an envelope Or paste it on a penny postal. tude- modulated alg J. E. SMITH, nais for teat and ex- President, Dept. 7BX, National perimental purposes. Radio Institute. Pioneer Home Study Radio School, Washington S. D. C. SAMPLE LESSON FREE I will send you a FREE Lesson, "Getting GOOD FOR BOTH SAMDLEELB001f Acquainted with Receiver Servicing," to FREE show you how practical it is to train for J. E. SMITH. President, neat. 78X Radio at home in spare time. It's a valuable National lesson. it without Radio Institute, Washlneton 9. D. C. Study -keep it-use it- Without obligating me. Lesson and rlcúl Interested& pthe obligation! Tells how Superheterodyne Cir- below..I (eto In Radio Qechecckked cuits work, gives hints on salesman will Can. Please write plainly.) own Radio Service Bust. f ) ope ting Bxoadnstlog Receiver Sec vicing, Lo- ( ) My Station ( ) Sparo Time Radio Servicing t ) Industrial Electronics cating Defects, Repair of allY i cmlxc RCWRIaRD Technician for Radio ( ) Public Address Systems S[RYICINC ( ) Serviced Loudspeaker, I. F. Trans- , ICBM Gov't. Mill. former, Gang Tuning, ( ) Aviation r Radio ( ) tan' Raáirbor, (If you nave not decided which branch you prefer -mall coupon for Condenser, etc. 31 illus- facts to help you decide.) trations. Nane Age My Radio Course Includes Address TELEVISION ELECTRONICS City Zone State FREQUENCY Approved for Training Under Cl Bill MODULATION L NJ RADIO -CRAFT for FEBRUARY, 1947

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HERE IT IS AT LAST ! The radio line thousands of service engineers have been waiting for -yes, the radio that has everything the service trade needs to cash -in on today's big pent -up new set demand. And who else but National Union could provide a merchandising plan for radio sets -so perfectly fitted to the service engineer's special needs ? For over 15 years National Union products, COMPANION MODEL No. 571.5 Tubes. AC- plans and policies have been shaped for the exclu- DC. Superheterodyne Circuit. Built -in Antenna. Auto- matic Volume Control. 2 -Gang Air Condenser Tun- sive benefit of service dealers. ing. Illuminated Slide -Rule Dial. Standard American And now N.U. RADIO SETS are here -for the Broadcasts. Walnut Veneer All-Wood Table Cabinet, 13%" x 7%" x 85ú ". same service men who have so long known and used other N.U. products -and have found the OTHER MODELS NOW BEING PLANNED N.U. way of doing business a better, more profit- A 3 -Way (AC -DC- Battery) Portable Model. able one for their special type of operations. A Combination Table Model Radio -Phonograph with Automatic Record Changer. THE LINE -5 models, of which one 5 -tube and one 6 -tube A 6 -Tube Battery-Powered Form Rodio Table Model. model are now ready; three others available in 90 days. THE PRODUCT -Top quality throughout; precision -built chassis; beautiful cabinets in modern designs. Here, for the first time, is a practical post -war radio PERFORMANCE- Thoroughly up -to -the- minute; N.U. sets compare with the best in their class. line for the service engineer to handle -a group PRICES- Competitive with established brands. of fine modern radio sets -but above all a proven VOLUME REQUIREMENTS-None! N.U. sets are not sold on merchandising plan which fits. Ask your N.U. a franchise basis. Order whatever quantity you need. Distributor for the complete facts today ! DISTRIBUTION -Sold only through N.U. Distributors and Service Dealers. NATIONAL UNION RADIO CORPORATION, NEWARK 2, N. I.

; J,'. w L J S / _f

Transmitting, Cathode Ray, Receiving, Special Purpose Tubes Condensers Volume Controls PhotofubeS Panel Lamps Flashlight Bulbs Radio Sots Auto Vibrators Ballasts Batteries

2 RADIO -CRAFT for FEBRUARY, 1947

www.americanradiohistory.com F

PHOTOFACT FOLDERS analyze all post -war RECORD CHANGERS!

Post -war radio is barely a year diagnose trouble, hunt defec- old, but already are 40 tive parts, make re- there adequate PUBLICATION DATES: different record changers on placements in all the latest Set No. 11 .... January 10 the market. Do you know who radios, phonographs, record Set No. 12 .... January 25 makes them? How they oper- changers, recorders, communi- Cut this out and MAIL IT TO YOUR DIS- ate? How to service them in cation systems and power am- TRIBUTOR. If you do not know his name and address, send it directly to Howard W. case of breakdown? Do you plifiers. Data and photographs Same as Co., Inc., 2924 East Washington Street, Indianapolis 6, Indiana, and we will know where you can get up- are made from actual examina- see that your nearest distributor gets it. In Canada, write to A. C. SIMMONDS & SONS, to -the-minute results of life tions of instruments -not from 301 King Street East, Toronto, Ontario. tests that are now being run? reprinted or copied informa- Canadian Price, $1.75. This vital information now tion. PLEASE PRINT becomes a regular PHOTOFACT The cost? Only $1.50 for Send Vol. 2, O Send Vol. 2, Set No. 12 Set No. 11 FOLDER Service at no Extra each set of 40 folders. Actually Send me Volume 1 (including Sets Nos. Cost to You! Clear -cut they cost you nothing, for 1 to 10) with De Luxe Binder, $18.39. Individual Sets Nos. I to 10, $1.50 each. photographs, exclusive big line for they pay themselves over Send me a De Luxe Binder (at $3.39) drawings, parts lists, opera- and over again in time saved. My (check) (money order) (cash) for is enclosed. tion details, trouble- cause -and- Over 25,000 radio service en- (If you send cash, be sure to use registered remedy charts, tell you every- gineers now use and depend mail.) thing you need to know to do upon PHOTOFACT FOLDERS. Name a workmanlike job -help you Why let service problems Address PHOTOFACT do twice as many repair stump you? City Zone_State_ _ jobs a day. FOLDERS help you lick every PHOTOFACT FOLDERS save one of them! See your nearest Company Name valuable time in many other distributor or use the con- My Distributor's Name ways. They make it easy to venient coupon. City 'Trade Mark Reg. Pa

HOWARD W. Sams cO.,INC. si RADIO PHOTOFACT SERVICE Caoda-wrM a A. C. SIMMOlDS a SONS, M1 Kip Simi Est, raraaM, Oaten!'

RADIO -CRAFT for FEBRUARY, 1947 3

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FOR GOOD BUYS AND A GOOD TIME WRITE FOR OUR BIG BARGAIN BULLETIN VISIT OUR BIG BARGAIN COUNTERS b LISTING THE LATEST AVAILABLE EQUIPMENT counters in all our stores, Magazines These big bargain MAIL ORDERS FILLED FROM are printed months before you read with special items available are loaded down EITHER N. Y. OR CHICAGO them, stocks change, new things are developed advertise. in quantities too small to Marvelous and made, so we give you the very latest news war-time sets, new small gadgets you can have about the very newest things in radio and fun with . . . all sorts of new electronics in our Big Bargain parts and special things you'll Bulletin. Send for your want to see. Come in, look around NEW YORK CHICAGO copy to- and ask all the questions you 311w Yetrno S+ day and know all about the latest (1.10 1.111 wish. Come in often you'll have equipment first. When writing a wonderful time. address Dept. F -4 N.Y.C. Stores 115 W. 45th St 12 Fulton St. [Mitts & Warehouse: 242 W. 55th St. N.Y. 19

t, RADIO -CRAFT for FEBRUARY, 1947

www.americanradiohistory.com FEB. Prepared by SYLVANIA ELECTRIC PRODUCTS INC., Emporium, Pa. 1947

ONEDEVICE

FOR GREAT VARIETYD OF TESTSEMEN Electrical Measurements Made Easy With New Sylvania Unit!

SYLVANIA Poly (MULTI - PURPOSE) Meter

L..

Radio servicemen now can use the Measures D.C. from .1 to 1,000 Ohms ±6% to the left of 1/2 scale; new Sylvania Poly (MULTI-PUR- volts in full scale ranges of 3, 10, ±13% to the left of 3/4 scale. POSE) Meter type 134 to facilitate 30, 100, 300, 1,000. Current ±3% of full scale on all a multitude of electronic measure- Measures D.C. current from .1 but 10 ampere scale which pro- ments and tests. milliampere to 10 amperes in full vides ±5% of full scale. This product of Sylvania Re- scale ranges of 3, 10, 30, 100, 300, search is stabilized against errors 1,000 milliamperes and 10 amperes. INPUT IMPEDANCES due to voltage variations or gas Measures resistance from 1/2 ohm R.F. ranges -2.7 megohms resist- current in tubes. All accessories in- to 1,000 megohms in full scale ance shunted by approximately cluded. See your Sylvania Dis- ranges of 1,000, 10,000, 100,000 3 mmf. capacity. tributor. ohms and 1, 10, 1,000 megohms. A.C. ranges -2.7 megohms resist- CHARACTERISTICS AND ACCURACY ance shunted by approximately SPECIAL FEATURES 40 mmf. capacity. D.C. ranges ±3% of full scale. D.C. ranges -16 megohms resist- Tests audio, A.C. and R.F. voltages A.C. ranges ±5% of full scale up to ance. from 20 cps to 300 me through use 30 volts and ±7% above 30 volts. Remember the Sylvania Poly of proximity fuze -type tube built R.F. ranges ±5% of full scale up to (MULTI- PURPOSE) Meter type 134 is into handy probe. Full scale range 10 volts; ±7% from 10-100 volts; beautifully styled, compactly de- of 3, 10, 30, 100, 300. ±10% on 300 volt range. signed and easily read.

. 1 . _ L 1.1 A, ".n.. I' e. _. ,.

RADIO -CRAFT for FEBRUARY, 1947 7

www.americanradiohistory.com HERSHEL'S NG VALUES ; on Radio and Electronic Equipment

.L.,"r

1000 V PLATE SUPPLY IF transformer, mounted in aluminum can, KC, with trimmer, Thordarson plate transformer Thordorson T48003 2M -714 HI.valtage condenser, 3 shield 1500 air T47105. 1185 V each side of 550 swing MfO, 4000 V, hermetkally impedance coupled t 300 MA. Topped o 4% 5%í a5 sgóore M /un sealed in aluminum con. hpe 95c ]00 V each side of center, also black crackle cose. 1 KW. MODULATION TRANS. V at 55 MA bias. 6' 5' We hove a real value on a tr ddmion trans- 215a ,aaare gray, CHT $59.5 $49 former. This item, mode by RCA to broadcast 7%os. $9.5 specifications, is conservatively rated at 550 W ouches to modulate that new KW rig. Primary impedance for class B tubes up to 10,000 ohms plate to plate, seconda, y rated at 50 MA. 1:I Ratio. Third winding modular es saee., up to BO MA torrent. Really rugged construction, with flashover gaps on a Mycolea terminal board. Due to the fine lamination, this tro.,lormer will $1 not talk bock of 1 KW- Weight y 40

Westinghouse meter, 0.1 Wstinghouse meter, 0.1 Rf amps, round cose, MA movement, 2' round Western Electric meter, 4' 2 stole calibrated orimal Mermocovple, 0.140 and 0.500. Includes round, zero center,0- Vi MA gieol boa. Inside, mounting hardware. each side. mounting hardware '2"

Turing nit BC 375. Approx. 65 MMFD cond. toils, RF chokes, dials, asstd. mica condensers SELSYN t 2300 WVDC, over 550.00 in $375 pani MOTORS The ideal way of in dicating the position R. L. T. of r ary beos,m wind iindicator, and et TUBE TESTER Line cord ro.CED

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www.americanradiohistory.com FEBRUARY 1947 RADIO Editorial: Radio Pcggrpss is Slow by Hugo Gernsback 17

Radio- Electronics Monthly Review 18, 19

The Radio Pen in Europe 71 /.11A1:

AND POPULAR ELECTRONICS Electronics Incorporating {MORT WAVE High Speed Photo Flash by Lyman E. Greenlee 22 CRAFT TELEVISION NEWS RADIO & TELEVISION Teleguided Missiles by James A. Niland 24 Television for Today, Part IX -D.C. Reinsertion and Image HUGO GERNSBACK Synchronization by Milton S. Kiver 31 Ediror- 'n -Chief Antenna Principles, Part Ill- Directional Arrays and Radiation Fields by I. Queen, W2OUX 33 FRED SHUNAMAN Radio Frequency Lamp 46 Managing Editor

M. HARVEY GERNSBACK Amateur Radio Consulting Editor 250 -300 Mc Radiophone (Cover Story) by R. F. Scott, W2PWG 20 ROBERT F. SCOTT, W2PWG Simple Frequency Monitor by I. Queen, W2OUX 21 Technical Editor Ham Station from Surplus by Merrill Lindley 30 I. QUEEN, W2OUX Editorial Associate Servicing ELMER FULLER Problems of Instability by Ted Powell 25. Shortwave Editor Radio Data Sheet 344 (National Union Model 34 G -619) ANGIE PASCALE The Probe Tracer by Hubert L. Bailey 45 Production Monoger Transformer Winder 48 G. ALIQUO Circulation Manager Sound JOHN J. LAMSON Small Recording Studio, Part I- Microphone, Recorder, Turntable Advertising Director and Pickup by J. C. Hoedley 26 ALFRED STERN Sound Engineering 27 Conducted by A. C. Shaney 36 -No. Promotion Monoger Construction On THE COVER:

Building a Televiser, Part II -The Sound Section Is a Good FM Receiver... by Roy Freeland 28

Simple Modulation Meter by A. B. Kaufman 32 Detector for the Oscilloscope Kenneth C. Dike 74

Departments Transatlantic News by Major Ralph W. Hallows 35

World -Wide Station List Edited by Elmer R. Fuller 37

Radio -Electronic Circuits 38 Try This One 40 Why Not? 44 The Question Box 50 Directional Radiophone Technotes 54 built by the Japanese in

New Radio -Electronic Patents by I. Queen 70 imitation of American amateur Communications 76 equipment. Book Reviews 79

RADCRAFT PUBLICATIONS, INC. Hugo Gernsback, President; M. Harvey Gernsback, Vice President; G. Aliquo, Secretary

Contents Copyright, 1947, by Radcraft Publications, Inc. Text and illustrations must not be reproduced without permission of Copyright owners. RADCRAFT PUBLICATIONS, INC. PUBLICATION OFFICE 29 Worthington Street. Springfield 3, Mass. EDITORIAL AND ADVERTISING OFFICES 25 West Broadway, New York 7, N. Y. Telephone REctor 2 -9690. BRANCH ADVERTISING OFFICES: Chicago: 308 W. Washington Street, Suite 1413, Chicago 6, III. Tel. Randolph 7363. Cleveland: Burdette Phillips, Manager, 405 Erie Bldg., Cleveland, Ohio. Tel. Main 9645. Detroit: Frank Holstein. Manager, 307.8 Boulevard Bldg., Detroit, Mich. Los Angeles: Ralph W. Harker, Manager, 606 South Hill St., Los Angeles 14, Calif. Tel. Tucker 1793. San Francisco: Ralph W. Harker, Manager, 582 Market St., San Francisco 4, Calif. Tel. Garfield 2481. RADIO- CRAFT, February, 1947, Volume XVIII No. S. Published Monthly on 28th of month preceding date of issue. Allow one month for change of address. When ordering a change, please furnish an address stencil impression from a recent wrapper. All communications about subscriptions should be addressed to the Circulation Manager, Radio -Craft, 25 West Broadway, New York 7, N. Y. SUBSCRIPTION RATES: United States and possessions, Mexico,. Central and South American countries, $2.50 a year; $4.00 for two years; $6.00 for three years. Canada, 3.00 a year $5.00 for two years; $7.50 for three years. All other foreign countries, $3.25 a year; $5.50 for two years; $8.25 for three years. Special rates for members of the Armed Forces in U.S., or those addressed by A.P.O. or F.P.O. mail, $2.00. Entered at Post Office, Springfield, Mass., as second -class matter under the Act of March 3, 1879. FOREIGN AGENTS: Great Britain: Atlas Publishing and Distributing Co., Lfd., 18 Bride Lane, Fleet St., London E.C.4. Australia: McGill's Agency, 179 Elizabeth Street, Melbourne. France: Brentano's, 37 Avenue de l'Opera, Paris 2e. Holland: Technisch Bureau Van Beetle, Bemelmans & Co., Heemsteedsche, Dreef 124, Heemstede. Greece: International Book & News Agency, 17 Amerikis Street, Athens. So. Africa: Central News Agency, Ltd., 369 Smith Street, Durban, Natal. Universal Book Agency, 70 Harrison Street, Johannesburg. Middle East: Steimatzky Middle East Agency, Jaffa Road, Jerusalem. India: Magazines Distributors, 5 Bombay Mutual Annexe, Gunbow Street, Fort, Bombay I.

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Tubes used and Included: 2 -832. 3 -12A6, 1 -666, 2. 6517, 1.121501, 3- 12567. 1.1208, 1.9002, 3 -9003. I- IZAN1GT. These units were elmoyed front planes but are guaranteed and a shipped rn Ope,ating condition. including Wes, control head. and Cable plugs reedy to t drna- MOM/mo her power supply. Weight, 49 lbs. Shipping weight same. 65 lbs. Price $39.95 each

BC -375 -E GENERAL ELECTRIC MOPA TELRAD MODEL 18 -A 1111111 TRANSMITTER FREQUENCY STANDARD

Used as Raison transmitter in bombers Measures signals and ground stations. Frequency range 100 Kc.- 45,000 of 200.500 Kc. and 1,500- I2,500 Kc. Kc., with check is covered by means of 7 plug -in tun- points at 10.100. ing units furnished. By slight modifi- and 1,000 Kc. cation operation on 10 and 20 meters with a high de- is possible.- Oscillator is self- excited gree of accuracy. temperature compensated type. Pow- is Power supply is \TI er amp. neutralized class "C" using 21 I tube and is equipped with anten- self - contained na coupling circuit to match practi- for operation cally any antenna. Modulator is class from 110, 130, "8" using two 211 tubes. Power sup- 150. 220, and ply is 24 V. OC dynamotor which fur- 250 V. 25.60 nishes 1,000 V. at 350 M. A. However, transformer shown on cycles AC. this page is ideal for construction of I I O V. AC power supply, Complete with Transmitter output conservatively rated at 42.5 watts, phone 75 watts may be pushed to 150 watts. tubes, dual crys- _D_ CW. but as with tubes, dynamotor, seven tuning units, instruc- eve f- a m ea. pReAO0 Complete shown tal, and and cable connector plugs. Removed from bombers but checked tion book. and guaranteed. Brand new, Price complete $36.95 in original carton -..424.95 Weight, approximately 150 lbs.

Dynamotor ror 24 V. a operah.on of -- +'m`^^- 3 Hy. ma. -10 750 sCR-512 se 50. wt., 39 lbs / .A Swinging Choke for filtering of power. 5.000 V. insulation. Size 61/2 "x 71/4'r x 8". Weight, 38 lbs. Brand new, $7.50 fQ each (!)'. H. V. PLATE POWER TRANSFORMER LS -3 LOUDSPEAKER BC -348 COMMUNICATIONS RECEIVER 1425.0-1425 sec. at 750 6" PM type, housed in heavy Excellent selectivity, sensitivity and stability make this the ma, Pri. 110.115 V. 60- most outstanding of any receiver yet available from goy, metal case. For use on BC -348 ernment surplus. This receiver will give outstanding per- cycle, tapped for low and formance wherever high power. These trans- Receiver. Self- contained used. Built to withstand v.brahon and out- features gear driven 100.1 ratio vernier tuning control. formers were made for put transformer to match 4,000 Six bands- 200.500 Kc. and 1.5.18 Mc- Two stages RF, RCA equipment. Size. 3 stages IF. 13F0. filter, crystal manual or AVC. Complete I01/4 10" x ohm impedance. Used but guar- with tubes and 24 V. DC dynamotor. Easily converted to ' x 8" 110 V, AC operation. These receivers used, but an hardly Weight, 81 lbs. anteed satisfactory be told from new. Guaranteed operation. Models N, M, P, and Q available -please specify. Brand Price each new $17.50 each $7.50 Price $44.75 each

14 RADIO -CRAFT for FEBRUARY, 1947

www.americanradiohistory.com CS Sf Sce&fH

TWELVE FREQUENCY KIT 2: 25 RESISTOR MOUNTING STRIPS AND CRYSTALS TERMINAL LUGS $3.85 Contains 9 bake', e resistor strips for mounting 2. '4. 9.. 23. and 28 resistors which may be cut apart for any re. 11111 11111 Contains assorted freguenciss between 3.000 Kc. quirement. Also contains 's teen 1. 2. 3. and 5 lug termi- and 8,000 Kc. In FT 243 crystal holders.- We pick nal strips. fre- at random front mixed supply and cannot ¡elect Kit quencies. Complete AN /PRS -1 MINE DETECTOR

Complete Kit of 12 Crystals - 3.115 for detecting anetallicand non- metallic substances by oral or visual indication. Used for locating pipes, treasure, etc. Con elete ai shown with spare tubes, carrying use and ready tê,áperate by connection of batteries ITEMS FOR THE RADIO AMATEUR. not included. $hipped in original overseas moisture - EXPERIMENTER OR SERVICE MAN proof container. . ... ,- Available In kir form .0 a small f,a

KIT 3: 24 TUBE SOCKETS Containing the Iollowsng new Creams b-loss.soekets: 2. Acorn. 6 octal Amphenol. 4 -6 prong Millen, 4 -5 prong wafer, 4.4 prong wafer. 2 molded bakebte. 2 octal female Plugs and 2 -7 prong tube tester sockets with center socket fat checking

pilot lamps. . .

Complete Kit - __...._...._...:f2.3S

KIT 4: 6 ROTARY TAP SWITCHES

Contains: I -3 pole I I position non -shorting; 1 -2 pole 5 posi- KIT 5: 10 POTENTIOMETERS tion non -starting; I .6 pole 4 position non -shorting; I -I pole 9 position ran -shorting power tap; I ceramic insulated special; Contains 3 -.5 meg. carbon with ifs" length shaft. 2 -3500 I -6 pole 4 position with double contact wipers on 4 poles and 2 positions on 5th pole. ohm carbon 1 vac shaft, 1 -1000 ohm wire wound Vee Complete Kit of 6 Switches, shaft, I -dual 25,000 ohm wire wound with 3íe shaft. I - $1.85 I dual 30,000 ohm wire wound with Vae shaft, 2.100 ohm CARBON THROAT MICROPHONE wire wound with screw driver Ideal for portable, or mobile operation, also for construction of lie adjustment. plane, detectors, toys, etc. You can't afford to be without a few at the price. Ad- Complete Kit of justable elastic strap fits any neck. Works into 200 ohm impedance input circuit. Used. but in good condition. 10 Potentiometers $2.85 Price $0.25 cach

RADIO -CRAFT for FEBRUARY, 1947 IS

www.americanradiohistory.com SPRAGUE TRADING POST

WANTED - Triplett modele 1241 and FOR SALE OR TRADE -Record changer. 1232 -A In good condition. Have Weston Metro l0' records or ten 12" record. 801 .001 ma. AC and .001 ma. DC. new, with port. carrying case, 3 -tube ampli- never used. Also Solar CB -160. Philce 028. SWAP - BUY - SELL fier with Shure mike. Also, almost new RCA TS1V -97 -C. All N good operating Cryataliner. Want Rider's Manuale, re- condition. Jon Morrison. Box 4264. Okla- corder or sig. generator. Smith's Radie 9. Okla. Service, 21 N. Walnut St., Dexter, Mo. homa City SELL OR TRADE -s_ Chicago Instru- WANTED -Copy of T.M. -11 -879 or sim- ment *431 pocket VODCs (ono new) ilar on BC 1335 surplus transmitter: SWAP OR SELL -Oscilloscopes, oscilla- complete with Instructions and test leads. also manual on ID- 59 /APA -11 indica- SWAP OR SELL- Hickox 19X sig. gen- tors (BF and AFI. Presto recorder. Mols- Also Bello 0 -1 milllammeter. Need tor and Alf5 /APS -4 scope control unit. erator, tine condition. 100TH',, 828'a ener 14 -tube receiver. 211E and 209A P. A. speaker, sig. generator or what Murray J. Douglas, Box 506, Concord, 811's, 803's, 813'e, 807's, 11K34's. Want tubes, old earl. of many kinds including have you? Tom Erwin, 3735 Milwaukee Calif. .257 or .270 rifle. binoculars. good jig paw, loom couplers, DeForest HR and 990 Are., Chicago 41, Ill. also bench drill press. R. M. Short. 1509 tuba and Riders 1 and 2. Want tele N. 16th St., Boise, Idaho. coulpment and Ridera .5 and 10. Henry'. WANTED-All kinds of test emit., also Radio Berrice. 10 Fountain St., Newport. FOR SALE -HRO to rack, all colis and technical books and manuals. Send full R. I. noise limiter: 10 meter mobile miners descriptions and prices. Have some meters FOR SALE -Supreme #582 sig. generator -10. 15 and 15 watts: various Pioneer to sell trade. Sam Berenblum, 417 and ire. med., $45. Supremo *562 nudo- Oenemotors, custom built commercial po- Greenwich Are., Greenwich, Conn. lyser $85. Supremo tube tester *503. 145. FOR SALE- Melasner 150 -B transmit- llee '250 -watt phone. beautiful 6' cabinet. Supremo *547 multtmeter, $40. All la ter with shifter and extra parts and L. Quinlan, 8394 Park Ave., Weehawken, good working condition. Dixie Radio Shop, S20R receiver, both dike new. Have extra FOR SALE- Dfodemixed Supremo 5028 Jonestown, Misa. service parts to sell. Write for Ifat stat- tube teeter and analyzer 25,000 ohms per volt meter sensitivity. ing what you need. Wayne Storch, Beecher, Like new. Also FOR Hatticrafter lit. WILL SWAP one late model 805 R.C.P. old model Jewell multimeter with two SALE- communications tube and set a receiver SX -32, 13 tubes. 8 bands, 6 tester. Want portable re- meters and precision resistors, excellent point crystal corder. Chas. B. Alexander, 209 How- condition. Slicks Radio Service, P. O. Box selectivity, with Jensen FOR SALE- RMF, -99 with matching ard St., New London, Conn. 212, Marlon, Ky. speaker In Bud steel cabinet, Excellent Speaker, 12 -tubes like new. $150. Want condition. $135 f.o.b. Fred E. Fralick, 734 tube tester, voltohmmeter, SIR. generator. No. Church St., Salem, Oregon. DM -5 converter, and movie lamp socket for Airline model 62 -311. Capt. Chas. E. SWAP OR SELL -Ono ea. of following Spitz. Sgdn. Boca Raton K -1, Army NOT A tubes: 12SL7, 2526. 35Z5. V.R. 105. Also Airfield, Florida. several 5000 ohm small sensitive relays and two 8.000 ohm O.E. relaye. Melvin Youngman, WILL SWAP model airplane engine, air- 515 South Blvd.. Oak Park, IIL SUBSTITUTE Wanted -Used test equipment in fair or plane kit and all accessories worth $40 good working condition. for surplus SCR -284 or BC -054 -A Ro- Cash. Give full celver- details and price. Fritz Dubber, 120 Belle- Transmluer, or any other ham vue. Rutland. Vt. caulpment. What have you? B. Kopeck', 2010 W. 3rd St., Chester, Pa. FOR SALE -Howard 435 RCVR lust re- conditioned and aligned. Also two 1350v. SWAP OR SELL ---90 new Ire. 455 KC air-trimmed C.T. 300 me. sealed. Thor. transformers, $5 fron ilammarlund Super -Pro. ea. W. T. Rainey, Jr., Fayetteville, N. C. List $9.50 ea. Will swap for. suitable sig. generator. Burton M. Saks. 165 E. 19 St., Brooklyn 26, N. Y. FOR SALE -T.R.4 255 meter rig com- Mete. $30. Halltcrafter S39 receiver, 4 months used, $60. Mi. transmitter soot FOR SALE -1944 Scott Short -Nava Re- oMice.sale. Write for lint. V. Howerdel, 102 ceiver, model ECK., U.S. Navy special, 80 Hancock Ave.. Jersey City 7, N. J. kc. to 24 me., 6 banda. 8100. Mao Ham - marlund HQ 120X. $100. R. J. Blattner, 510 N. Bouidin St.. Baltimoro 5, Md. FOR SALE -Rider Chanalyet Model 162 -C. new. in perfect condition. $125 R. B. Hodge. Am Radio Shop. 603 W. Main. WANTED -CCash for broken down radios. Grand Prairie, Texas. Write to Edward C. Punt, 397 Melrose St.. Brooklyn 6. N. Y. Replace Wet Electrolytics with FOR SALE- Hallicraftora S -40 Commu- nication receiver, excellent condition, used WANTED- Melsener signal shifter. Have only about 2 months. Wilburn Wright, Box Filmo 8 mm movie camera with caso. TYPE RW 203, Hodgenville, Er. Howard 430 communication receiver, Un- SPRAGUE derwood portable typewriter. W. M. Mc- FOR SALE -Receiving tubes, boxed, 40 %, Donald, 13 Cooper St.,. Greenwood. When replacing wet electrolytic capacitors, use Sprague Type 50% off list, condensers, resisters. power Mass. very transformers, speaker., etc. Send for lista. RW. They're not substitutes! They're dry electrolytics of Could use movie. reflex camera. s -w receiver. E. Schmitka, Apt. 4E, 1981 FOR SALE -New 80 -watt phone trane- high voltage formation specifically designed for use as wet mitter with ails, slat and tubing anten- Shakespeare Ave., Bronx 52. New York. na, Radio Physics course and manuals. replacements or for other difficult applications. Due to their Want BT -6 10 -meter coils and crystals. extremely low power factor, lower capacity values give you FOR SALE -Solid silver buse for UHF Chas. llnleleln, 246 E. 148th SL, Bronx. 16 ga., approx. 9' roll, $1.25. Rat for New York. better filtering- For instance, Type RW -25 rated at 25 mfds. efficient coils and tanks. Also have new RCP 948 Docket multtmeter, 2000 ohms /v. is at least the equivalent of a 40 mfd. wet electrolytic. 16 ranges. $22. R. J. Cartwright. 69 FOR SALE -Abbott TR4 2 -meter rig Dlounttort St., Baton, Mue. complete with dual power supply. tubes They'll stand high peak surges. They'll handle a-c ripples - and hand microphone. Power nannies are 6 volt vibrator and 115 volt AC input. and they fit the standard mounting holes. Ask your jobber FOR SALE -TR -4 transceiver, converted 300 volt, 100 rail. output, $40. Fragil L. for Sprague Type RW. tor use on 199 mc. complete with hand Riggs, 5328 East Drive. Rockford, Ill. mike, power pack and new tubes. $50. R. V. Ruesoll, 25 Elk Place. Niagara Falls. N. Y. FOR SALE -ADC 1000 ohms- per -volt Write for the complete Sprague Catalog listing multitester wood AC-DC. portable typo in Capacitors and *Koolohm Resistors for - every case. uses 4" meter. In perfect condition. FOR SALE -Electronic multtmeter, model Postpaid for $14.95. J. Goldstein, 151- radio service, amateur and experimental need. 400. $95. Aaron Hollandmoritz, 918 N. 09 -39th Ave., Flushing, L. L. N. I. Madison Ave., Bay City. Mich. Address Ads to: Dept. RC -27 FOR SALE -Components from Russian WANTED -Rider manuals 8, 10, 11 and lank transmitter, coils. 12 also following tubes: 1LE3, 6A8. JAS, varlametof, dr- Radio Shop, St. namotor. phones. etc. F. E. Dickey, 237 21B8. Royce Saston's Green St.. Schenectady 6. N. Y. 1. Pontiac, Ill.

oov, FOR SALE -Western Electric BC -412 -A SWAP OR SELL-HRO colle em. oscilloscope 100 kc to 480 kc 1.7 -30 mc. Need small $35, or_}vhat have you to COMPANY Radio Serv- - set. trade? G. Doty, 1036 S. Broadway, Da) communication Bill's UM Spfl.NGuE Ice. 1747 West 6 St. Brooklyn. N. Y. 8, Ohio. NORTH ADAMS, MASS. JOBBING DISTRIBUTING ORGANIZATION FOR PRODUCTS OF THE SPRAGUE ELECTRIC CO. YOUR OWN AD RUN HERE FREE! Sprague will gladly run your own TRADING POST ad free of ject any that do not in our estimation fit in with the spirit of charge in the first available issue of one of the six radio mag- this service. azine, in 'which this feature appears. WRITE CAREFULLY or print. Hold it to 40 words or less and confine it to radio subjects. ..11..14/44/f Sales Manager Sprague reserves the right to rewrite ads as necessary, or to re-

ASK FOR SPRAGUE CAPACITORS and *KOOLOHM RESISTORS by name! Trademark Reg. U.S. Pot. OIT.

16 RADIO -CRAFT for FEBRUARY, 1947

www.americanradiohistory.com By HUGQGERNSBACK

RADIO PROGRESS IS SLOW

Radio Progress Is Evolutionary as Is Any Normal Growth

RADIO-CÌAFT continuously receives letters from read- the public is far ahead of the technician. Manufacturers, ers who deplore the slow general progress in radio. engineers, and those others who are really supposed to Many correspondents lament that the promised know, are slow and put obstacles in the way of every and glowingly advertised radio wartime inventions new invention and forward-looking device. so far have not materialized in our peace economy. Just to mention one case, note that when Dr. Lee They ask : Where are the radar applications for autos, de Forest first presented his audion to the Navy -which private planes, and motorboats? What about the prox- certainly had excellent radio people -he was given a imity fuse's miniature radio device -why don't we have long list of reasons why the audion or vacuum tube it in our pocket sets? What about those "printed" radio was no good and should not work! circuits doing away with most of the present -day wired It is a fact that, when confronted with something of radio sets? And a host of other similar questions. a revolutionary nature, technicians immediately begin We had occasion to speak of this some months .ago. to find fault and see reasons (probably good ones at the Because of the continuing interest, we present a num- time) why the device is not practical. Here the engineer ber of further pertinent facts on the problem: is probably right, because a crude model of an invention Radio progress is certainly not slower than progress IS full of faults, has an extraordinary amount of "bugs," in any other field. It may even be said that it has ad- all of which must be eliminated. This is usually a long- vanced at a rather fast rate, if we wish to draw paral- winded, heart -breaking process. The manufacturer, too, lels with other arts. knows that an early model -or even a semi -perfected Robert Fulton built his first steamship, the Clermont, one is usually an invitation to spend fortunes over which became known as "Fulton's Folly," in 1807. Yet many years before the article can be sold commercially. many decades elapsed before commercial steamships be- The manufacturer knows only too well that what works came a reality. The incandescent lamp was first demon- well in a laboratory may fail completely in the home strated by Edison in the year 1877, but it was not till or in the hands of the public. Books have been written about 1883 that electric lights were first used in private on this phase alone. Many manufacturers have gone homes -extensively not until about 1890. bankrupt in backing an invention which was theo- The Diesel engine was invented by Diesel in the year retically sound, but which had not been developed suffi- 1892, but Diesel locomotives came into use only in 1924. ciently to be placed in the hands of the public. You can make a long list of similar inventions and All this, however, is only one phase. There are other you will find that from the demonstration of the early more important ones. Chief of these are patent- ques- model to the successful commercial use of the device tions. Few patents may be termed "basic." Only a few there is always a time lag that may cover a number of such patents come along during the year. Even if decades. they are as basic as the audion, there is still trouble. Radio's most important invention -the audion, the While de Forest had many patents on the audion, that three- element vacuum tube -was invented by de Forest did not prevent others from suing him in connection in 1907. Yet in 1920 -22 we were still using crystal sets, with special manufacturing processes and the internal and it was over 19 years from 1906 to 1925 -27 before structure of the vacuum tube. vacuum-tube sets were produced on a mass basis. Nor An invention, no matter how good, is of no value at is the audion an exception. all if you do not have the machinery to build it. Often Modern broadcasting itself was first demonstrated by such machinery is more important than the device itself. Lee de Forest in the year 1907. It did not become a reality As an example of this let us point out only one. until the Pittsburgh Westinghouse station KDKA start- The slide-fastener, popularly called the zipper, was a ed regular broadcasts in the year 1920. Similar delays basic invention. Yet this invention was quite useless are true of all radio inventions and developments. There without the highly complex machinery necessary for is usually a lag from 10 to 20 years before the early mass production. In this instance the machine to produce model is translated into a full- fledged commercial reality. the device was really the heart of the invention. Many The reader may well ask the reasons for this seem- similar parallels can be cited. ingly slow progress in radio. They are simple once the There are still other phases of equal importance. These great difficulties of pioneer inventions are understood. are purely economic in nature. It is most difficult in In reality, there is nothing wrong with radio-or many instances to secure capital for new and unproved other inventions for that matter-it is always the hu- inventions. Bankers and capitalists are extremely hesi- man beings who are slow to grasp new things. Nor is tant about investing money in them. They know from it the layman who is slow. Quite the contrary -usually (Continued on page 51) RADIO -CRAFT for FEBRUARY, 1947 17

www.americanradiohistory.com SINGING COMMERCIALS a r e banned from the Argentinian ether waves by an ingenious regulation, an gpIIIlIIIIIIInNIIIIlII11I11111111i11111111111 American advertising man just back E -ELECTRONICS from Buenos Aires reported last month. E Hearing no musical advertisements during a three -day stop in the Argen- tine, he investigated, and found that 'commercial jingles and ditties had been Interesting introduced into the country several years ago. They had cluttered up the through the vapor of the substance to RADAR SAVED two radarless steam- pampas airwaves to such an extent that be analyzed. Certain wavelengths, of ships from head-on collision during a protests of music lovers prodded the these microwaves are absorbed by those blinding snowstorm on Lake Superior Direction de Radiodifusion into action. molecules which they cause to rotate in last month when an officer aboard a Unable to discriminate against the sing- resonance. Molecules of different sub- third ship perceived the danger on his ing as opposed to the spoken commer- stances absorb a different series of ship's radar indicator and warned them cial, the Argentine version of the FCC wavelengths. Thus for each substance by radio to change course, according to simply clamped down a rule against all there is a characteristic pattern of ab- Charles J. Pannill, president of Radio - recorded commercials. Now every ad- sorption lines which when projected marine Corporation of America. vertising word has to come directly electronically on a screen present an First Mate Tom Hermansen of the from the announcer's lips. And without easily identifiable "fingerprint" of the ore carrier A. H. Ferbert, aboard which recordings, singing commercials are im- vapor under investigation. Radiomarine recently installed a new practical. The basic elements of the microwave type .of three- centimeter merchant ma- spectroscope as developed by Drs. Wil- rine radar, was watching the radar just THE BLUE BOOK of the Federal liam E. Good, Donald K. Coles and T. W. before dawn on November 28 when he Communications Commission, which Dakin of the Westinghouse Research observed that the luminous "pips" rep- became the center of an etheric storm Laboratories are an oscillator tube or resenting two other ships on the radar immediately upon publication, has be- radar tube, waveguide, crystal detector, image were rapidly converging from come so popular -or the reverse -as to oscilloscope and sweep generator. opposite directions. necessitate another printing, a last Microwaves emitted by the oscillator Realizing that lookouts on neither month Washington report states. tube are directed through a rectangular vessel could see the other ship in the The book "Public Service Responsi- waveguide which contains the sample snowstorm, Hermansen immediately bility of Broadcasting Licensees" dealt gas or vapor to be analyzed in a gas contacted the two ships by radio, warned with the type of service the Commis- cell section that is sealed off with plas- them of their danger, and directed sion felt listeners had a right to expect tic tape. At the far end they are picked each on a change of course which avert- from their broadcast stations. Issued up by a sensitive crystal detector which ed the collision. originally in an edition of only 5,000 passes the impulse received on to the It was reported that the two vessels and priced at 25 cents, it sold out rap- oscilloscope. For clearer definition of were the SS J. H. Sheadle and the SS idly, as did another edition of 6,500 pub- the absorption lines the vapors in the Sascatu, and that the officers of both lished by the National Association of gas cell are held to a pressure of about vessels had been unaware of their dan- Broadcasters. The Commission accord- 0.1 mm of mercury. ger until they were warned by Her - ingly had to make arrangements for re- The oscillator tubes used to obtain mansen. printing several thousand more copies microwaves in wavelengths varying at the same price with the Superin- from 1.2 cm to 1.6 cm are reflex kly- GROUND 'CONTROLLED approach tendent of Documents of the Govern- strons, tuned by changing the size of (GCA) will be in operation at 56 air - ment Printing Office, who is also in the resonant cavity. Several tubes are bases in this country and overseas by charge of sales of the book. used to cover the band required. midsummer, the Army Air Forces re- The frequency of the oscillator tube, ported last month. Every major AAF RADAR WAVES from 1.2 to 1.6 cen- or klystron, is swept in installation in the country could be synchronism equipped with important blind -land- timeters in length have found a new with the horizontal sweep of the oscil- this use in microwave spectroscope devel- loscope tube, and ing device if sufficient trained personnel the output of the crys- available, oped for the analysis of chemical sub- tal detector is applied directly to the were the Army reports. stances. vertical plates of the oscilloscope The Mark II production model of so that in all Identification of whole molecules is absorption at particular frequency will GCA, used theaters of operations accomplished by beaming microwaves be recorded as a vertical deflection by the AAF, requires from three to five of the oscilloscope operators, or controllers, on each eight - trace. hour shift. This means that a minimum of nine trained controllers are needed Ammonia has to keep one Mark II GCA unit in op- been found to have eration 24 hours, or a total minimum a pattern of 30 dis- of 1,170 controllers to have the Army's tinct absorption stock of stored GCA units functioning. lines in this region. The Mark III and IV, the 1946 model, Other compounds requires only one controller on a shift. that have been However, these new models will not be- tagged by this come available to the AAF for some method are water time due to shortages of critical parts vapor, acetone, and the present high cost of production. cyanogen bromide and carbonyl sul- RADIO TUBE PRODUCTION for fide. The limita- December, 1946, hit a peak 40 percent tions of the micro- above the former all -time high figures wave spectroscope of 1941, stated M. F. Balcom, vice-presi- are not yet known, dent of Sylvania Electric Products, last but it promises to month. be a very valuable Since the number of types made was tool in the study of much smaller than in 1941, increases in molecules and even production of many standard tubes is of the atomic nuclei much greater than the overall figures The recently- developed microwave radar -spectroscope in operation within the molecule. indicate.

18 RADIO -CRAFT for FEBRUARY, 1947

www.americanradiohistory.com viously could no longer receive our FM

nllllllllllllllmlllllllummllnnmllllnlllllllllmlllnlmm station WMOT. We did not feel justified in advising our FM listeners to junk Ivi O N T H LY R E V I E W their sets and buy new ones when they become available. Ignoring these sets as far as FM is concerned would have done anything but further the interest

LAIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII111IIIIIIIIIIIIIIIIUUIIIIl011111111111111111111111111111111nllllllllllllll4 among enthusiasts who invested in FM to the Teehnieian receivers just a few years ago. The ob- vious answer to our problem was a RADIO ITEMS OF THE MONTH ' RADAR is now being used to detect converter to adapt a receiver to the new meteors, a recent bulletin of the Na- band. Billboard television is being studied by of tional Bureau Standards announces. While experimenting with a single - a large New England outdoor advertis- The Bureau believes that continued ing concern. Present billboards are at tube quartz crystal controlled converter study of meteors will reveal informa- at a location approximately fifteen a disadvantage because copy cannot be tion on the effect of meteors on radio changed readily. Television technique miles from the transmitter (operating waves which may be important in con- at the time with an estimated effective would make them literally up- to -the- nection with FM and other v.h.f. minute. radiated power of not over 100 watts) broadcasting. the oscillator' in the converter acci- One way in which meteors may af- dentally failed. Much to our surprise An electronic fire alarm uses a photocell fect radio waves is to cause the "bursts" which is sensitive to the ultra -violet and gratification we could pick up the (parts of programs from long- distance station on 94.5 megacycles at another rays emitted by flame. A special filter stations interfering with local station makes it insensitive to ordinary light, spot on the dial of the receiver while performance) on FM channels. Some trying to find a signal from the crystal though it reacts to a fire in a few sec- scientists, such as J. A. Pierce onds, often of Cruft as compared to the minutes Laboratory, Harvard University, be- required by heat -operated alarms. lieve that a large part of the ioniza- LI L2 tion of the E layer of the ionosphere TRANS. Thirty thousand cars in the United may be caused by meteors. A knowledge ANTENNA NF. LCyOLD F U REC. States have already been outfitted with of the behavior of the E layer is of pri- The tubeless converter is simplicity itself. two -way telephones, according to the mary importance since it controls radio Society of Automotive Engineers. propagation on many of the frequencies oscillator. We then found that the used for radio communication and radio crystal oscillator was no longer func- Static generated by automobile tires navigation. tioning. The part of the circuit remain- may be reduced or eliminated by a new Supporting evidence for these con- ing consisted of two tuned circuits and static suppression powder consisting of tentions was the fact that interference a detector crystal -this became the very finely divided carbon, says N. B. encountered on the old frequency mod- tubeless converter shown in the sche- Settle, service director of the Dodge di- ulation broadcasting frequencies in the matic. vision, Chrysler Corporation. The pow- form of "bursts" had been found to co- The unit is merely connected in series der, commonly known as acetylene incide with the appearance of meteors. with the new high- frequency antenna's black, is injected into the inner tubes Further, it had been reported that dur- transmission line near the receiver. No with a special tool. ing the war radar operators tracking other connections are necessary. The in- V2 rockets had been confused by re- put circuit is tuned to the transmitter Television shows which feature hyno- flections from meteors. Other radar ob- frequency and the output is tuned to a tism have been banned by both the BBC servers, such as O. P. Ferrell, working frequency in the old band. This latter and NBC, after experimental telecasts in an unofficial capacity in India, had frequency is the result of radiation indicated a possibility that members of actually made observations which coin- from the local oscillator in the receiver the audience might be hypnotized acci- cided with the visual observations of mixing with the transmitter frequency dentally. meteors. and producing a converter output signal which falls in the range of the old A new microwave "electric eye" devel- AMERICAN RADIO TRANSMIT- band. In the case of WMOT which is oped by General Electric uses centi- TERS will make Munich the voice of on 94.5 mc, several types of receivers metric waves instead of the usual light democracy, redeeming that old city which we have tried tuned in the sta- beam, and a parabolic receiving antenna from the associations of appeasement tion when the receiver dial was adjusted instead of a photocell for receiving the and treachery which have sprung up to near the high end of the old band. beamed waves. Since the microwaves around its name, according to a report The coils were easily wound for the pass readily through non -conducting from the State Department last month. job. All are self- supporting and space materials, it can be used for many pur- Three transmitters, each of 85 kilo- wound, 7/16 -inch in diameter. Ll is two poses for which the ordinary photocell watts power, were placed in service in turns of No. 18 insulated hook -up wire device cannot. For example, an elec- December to relay Voice of America interwound with L2. L2 and L3 are broadcasts of tronic counter can be used to detect non - to Eastern Europe. No. 10 solid enamel wire, L2 having 3 Special filled bottles on a conveyor line, even attention was attracted to the turns and L3 10 turns. L4 is 3 turns of though the liquid with which they are prospect of beaming Russian -language the same wire as Ll, and is interwound to be filled be quite transparent. broadcasts from the United States into with L3. We had only three components the Soviet Union. Programs are also to purchase for our converter. The two FOUR MILLION RADIOS, more or directed to Czechoslovakia, Yugoslavia, 8 -plate midget air -trimmer condensers less, will be equipped with FM in 1947, Rumania, Poland, Bulgaria, Hungary, Cl and C2 cost 35 cents each and the R. C. Cosgrove, president of the Radio Austria and France. Sylvania 1N34 crystal was $1.60. Sur- Manufacturers' Association, predicted plus radar crystals could be used in last month. A NEW FM CONVERTER, to enable place of the 1N34 but although they The exact figure estimated by Mr. old FM sets to pick up the new band, can be had for as low as 39 cents, some Cosgrove was 3,750,000 receivers, requires no tubes. It was described last of these crystals are probably rejects. which he expects will amount to ap- month by Henry R. Kaiser, chief engi- In addition, small static charges in the proximately 25 percent of the 1947 pro- neer of WWSV and its FM affiliate antenna circuit may impair operation duction. Ninety percent of the console WMOT. Mr. Kaiser said: of some of these crystals whereas the models to be made next year will have "After converting our FM transmitter 1N34 appears to have a greater current an FM band, he believes. for operation on the new band, approx- carrying capacity. Our converter cost Production of television receivers was imately 6,000 owners of the pre -war $2.39. (The nine cents covers the four estimated at about 325,000 for 1947. FM receivers in the Pittsburgh area ob- screws and wire.)"

RADIO -CRAFT for FEBRUARY, 1947 19

www.americanradiohistory.com By ROBERT F. SCOTT, W2PWG

250 -300 MC RADIOPHONE A Nell- Engineered Portable Directional Transceiver

THE radiotelephone - i.c.w. trans- of the low- frequency unit. These jacks Fig. 2) has three positions; the center ceiver shown on our cover was are for microphone, headphones, and a position is OFF and no plate or fila- captured from the Japanese in remote send -receive switch. A send -re- ment voltages are applied to the tubes. the Pacific Theater. Resembling ceive pushbutton switch is just above When the lever is moved away from ham equipment in many respects -even a flat mounting plate which supports a the operator, the circuit is set up for down to the use of American tubes - removable telegraph key. A key jack is reception of voice and interrupted-con- some of its features may prove interest- located just below the mounting plate. tinuous -wave signals. If the send -re- ing to American amateurs. Power for the set is supplied by a 6- ceive button is pressed while the modu- volt storage battery and a 180 -volt B- lation switch is in this position, the cir- battery, housed in the box on the ground cuit becomes a transmitter operative beside the tripod. for voice transmission only. When the The antenna reflector system con- modulation switch is thrown toward the sists of nine dipoles tuned to the mid- operator, the set becomes a transmitter dle of the tuning range (272.7 Inc). The for tone- modulated c.w. driven element is a pair of adjustable When the set is used for receiving, dipoles screwed into the sides of the the incoming signal is concentrated on high- frequency unit. Telescopic adjust- the dipole by the reflectors and coupled ments permit these elements to be to the grid of the 955 through the tank tuned precisely to the operating fre- coil Ll. At the plate, the signal is mixed quency. Fig. 1 shows the directional with the quenching voltage from the characteristics of the array. Maximum triode section of the 6F7 so that the 965 signal radiation is in a beam of '72 de- becomes a separately quenched super - grees. regenerative detector. The a.f. signal at Photo B is a close -up of the control the plate is coupled through transform- panel located on the left side of the low- frequency unit. The large wheel in the center of the panel is coupled to the tuning condenser in the high- frequency unit through a length of flexible shaft- ing. The regeneration control knob, below and to the right of the tuning wheel, adjusts the amount of voltage on the plate of the triode section of the 6F7 when it is used as a quench oscillator. The quench -oscillator coupling knob is used to vary the coupling between the pickup coil and the oscillator plate coil. The lever- operated modulation switch Photo A -The Mark 7, assembled for operation. is below the control knobs. Known as the Type 96, Mark 7, this transceiver was designed for receiving How It Operates Photo B- Operating controls are on left side and transmitting voice and interrupted - The modulation switch '(the several er Ti to the pentode section of the 6F7 continuous -wave in a frequency. range sections of which are shown ganged in Transformer T2 couples the plate cir- of 250 to 300 mc. Six slide -in coils are cuit to the headphones. used to cover the range. A 955 acorn The quenching voltage is generated tube acts as a superregenerative detec- in coils L4 and L5 and the triode 6F7. tor in an Ultraudion oscillator circuit Coupling to the detector is controlled by for receiving, and as a plate- modulated the position of L6. oscillator for transmitting. A 6F7 tri- To transmit voice, the modulation ode- pentode acts as a 300-kc quench os- switch is moved away from the oper- cillator and audio amplifier for receiv- ator. Pressing the send -receive switch ing, and as a tone generator or modu- shifts relays Ry -a and Ry -B to the lator for transmitting. The range is transmit position. This removes the given as five miles under ideal terrain plate voltage from the triode section of and atmospheric conditions. the 6F7 by opening contacts 7 -8. The Photo A shows a right -front view of output of the microphone is impressed the assembled set with its high- and low - on the low- impedance primary of M of frequency units and the antenna array Tl. The secondary voltage of the input mounted on a tripod. The high -fre- transformer feeds the grid of the pen- quency unit is mounted in a box sus- tode section which has become the modu- pended in front of the parabolic reflec- lator stage. The plate current of the 955 tors of the array. The low- frequency passes through the secondary of T2, unit and controls are mounted behind through contacts 1 -2 to the plate of the the reflectors and above the center of oscillator. The output of the modulator the tripod. Three jacks are placed in a fully modulates the plate current of the vertical row along the right -rear edge Fig. I- Radiation pattern of parabolic array 955. 20 RADIO -CRAFT for FEBRUARY, 1947

www.americanradiohistory.com Sidetone for monitoring is secured by coupling the headphones to the second- 12 1 ary of T2 through a 0.5 -1.4f blocking v 10 19 condénser. The insertion of a 500,000 - 6F7 KEY ohm resistor in the ground side of the ;Pò phones through contacts 4 -5 reduces the PENTODE SECT. 1 .5

sidetone to a comfortable level when PHONES' Ry -b. connects L3 to transmitting. the VOICE ground end of the tank coil. (The pur- Ì (MOD. CONT.) OFF4 -1-- -I pose of L3 and C1 could not be deter- M.C.W. mined during the tests because there IN OFF POSITION- was no apparent change in frequency or quality when either was omitted 1 from the circuit. It is possible that the TRIODE SECTION I designers felt that added inductance SEND was desirable while transmitting and

more capacity when receiving. This REC'VE I might account for the action I of Ry -b.) SEND-RECEIVE I Tone -modulated transmissions are PUSH BUT T. SW. made with the modulation switch in the .5 IIRyA: ikEGEN...COT.-1r JACK I i.c.w. transmission position. Contacts 0 I

í 15 -16 and 1 -2 are closed, making the ó%WyyÓKí OK triode section of the 6F7 an audio oscillator using the primary and secondary ( windings of T1 to supply the necessary B- A grid -to -plate coupling. Contacts 9 -10 are I opened so that plate voltage is applied to the pentode section only when the SOCK.TO RESECTION PLUG TO POWERT key is closed. The signal from the a.f. SUPPLY oscillator is amplified by the pentode R.F.SELTION _ section which functions as a modulator Fig. 2 -A.f. section (above) and r.f. section ust as it does during voice transmis- (right) of the Mark 7. An ultraudion oscillator ANT.COUPLING CONT. is used and many other points of similarity to sions. i L2 955 regular amateur v.h.f. circuits will be noted. !:A 1 50uut [ spaced to '4 -inch. The 420-me coil has

only one turn and its diameter is varied I CI sligf)tly to hit the band. The tuning REC1 condenser may be a Cardwell ZV -5 -TS SE which is designed for u.h.f. circuits. Its stator is divided into two segments. The RyB RF.C.I capacity range is from 1.6 µµf to 5 µµf. Technical material and drawings for this article on the Mark 7 were made 50uuf Í available to us through the courtesy of Top view of r.f. unit showing the 955 and one the Department of Commerce. PLUG TO A.F. SECTION of the tuning coils plugged into its position. Although the Mark 7 was designed SIMPLE FREQUENCY for specific military applications, its MONITOR circuit might be used as a basis for an IN THESE days of VFO, frequency useful in adjusting a transmitter. amateur transceiver for operation on multiplication and antenna- coupling A wavemeter can be used in several the 144 -, 220 -, and 420 -megacycle bands networks, the wavemeter is a most ways. Coupled to an oscillator, it ab- by using coils and condensers designed indispensable item. Wavemeters and sorbs maximum power from it when to operate most efficiently on these frequency meters are used to measure both are in resonance. Monitoring the bands. the same units but they meet different output of the oscillator will show a requirements. A wavemeter uses a slight change in intensity or frequency simple tuned circuit which absorbs (Continued on page 65) power from an oscillator under measurement. The indication is definite as to wave band but it is relatively broad. A frequency meter, as the term is generally used, is based upon an oscillating circuit which generates its Rear view of a.f. unit showing quench oscil- own signal to lator coils, Relay A and the tuning gears. beat with another. Al- Coils . for the u.h.f. ham bands are though its frequen- wound with No. 18 wire on a 1 -inch cy indication is form. (Silver- plated wire is more effi- sharp, the order of cient, particularly on the higher fre- harmonic must be quencies.) The 144 -mc coil has four f- determined by some inch turns spaced to approximately %- other method. Both inch and the 220 -mc coil has two turns types of meters are

RADIO -CRAFT for FEBRU AR Y, I 9 4 7 21'

www.americanradiohistory.com x$LYMA, E LEE

HIGH SPEED PHOTO FLASH

A Portable Battery -Operated Unit Which Can Take 10,000 Pictures with One Bulb

standard parts obtainable from hard- any particular value; the important wire stores and radio parts jobbers. point is that all must have the same ca- While the weight of the equipment is pacity (within about 10 percent). Oth- objectionable for some applications, the erwise an excessive peak voltage might results have been very satisfactory. The be built up across one or more sections units have been rebuilt a couple of times during discharge. for greater operating efficiency and re- The series -parallel discharge circuit duction in weight. Fig. 1 is the sche- has certain definite advantages for matic. photoflash work. It permits the con- An Electroflash bulb operates through centration of a great deal of capacity in the discharge of a high- capacity con- a small space with light weight. Stand- denser which is charged to a voltage ard components in a low- voltage power between 1,600 and 2,500. The capacity supply can be used. Since voltages are of this condenser may vary from 15 µf lower, the safety factor is greater and to 100 of, depending on the size of bulb there is much less chance of getting a and the light output desired. The pow- serious shock from any part of the cir- er unit consists of the large condenser, cuit. The only time a voltage of 2,500 a power supply to charge the condenser, is present is at the instant of discharge and associated relays to trip or trig- of the series -parallel capacitor bank. At ger the flash in synchronization with all other times the peak voltage will not the camera shutter. exceed 500 volts. The operating range Using a 9 -volt battery, the power unit for successful pictures is between 400. delivers 500 volts d.c. to charge 500 of and 500 volts. Since the camera shutter of electrolytic filter condensers which is tripped by a magnetic relay, camera are charged in parallel and discharged and flash bulb may be operated by rein series. Discharge voltage is between mote control to take pictures otherwise 2,000 and 2,500 volts, while the charge difficult, dangerous, or impossible to get. voltage is 475 to 500 volts. These may Battery drain averages 4.5 amp. WEIGHING only 23 pounds, be regarded as peak ratings which are Drain starts at 9 amperes and tapers this camera and repeating not to be exceeded because' the electro- rapidly during the 10-second charge in- flash unit will take over 1,000 lytics are 100 of units with 525 -volt peak terval to about 2 amperes. With care, pictures on a single set of rating. Some question might be raised as many as 2,000 pictures can be taken batteries and 10,000 or more pictures as to the life of electrolytics when used with a single set of batteries. The baton a single flash bulb. The Amglo cold for this type of service. So far, after argon light produces flashes with ter - about 10,000 cycles, on two different and rific intensity for about 1 /10,000 second, separate units, there has been no sign to stop the fastest motion. Requiring of capacitor failure, and a check shows only 10 seconds to recharge between that the capacity of individual units has pictures, a complete 60- exposure roll of increased slightly. Of course, for use in film may be taken in 15 minutes. a series -parallel circuit, the capacities The equipment shown in the photo- of individual units must be selected to graphs was built by the author from match, although they do not have to be

¿MMOD.SW.

I CAMERA d LIGHT 6 PRONG d PLUG -IN SOCKET SOCKET FOR POWER PACK Ode P SHORTING PLUG FOR 12-A FUSE BATTERY USE

100 CI C3 1 C4 1 C5

525 V. !MASTER SW. 112 GANG

! S.P. D.T. o-6ó0v. do-

Fig. I- Schematic of the main unit. Sockets and plugs are for a.c. power supply and camera. Photo B-A rear view of the photoflash unit 22 RADIO -CRAFT for FEBRUARY. 1947

www.americanradiohistory.com tery used for these tests was made up ed that it will withstand the operating as can be seen in the Photo C, to insure of six Burgess 4FH "Little Six" cells voltages applied. The vibrator is the adequate insulation. as shown in Photo B. Other batteries standard four -prong variety of 4- to 6- The switch used to achieve the rather . would work, but this particular type fits amp. capacity. Not all types of power complicated result outlined above was the case very nicely and has given ex- transformers will work in this circuit cellent results. As the batteries get old- as some of them will not supply sufficient er and weaker recovery time is slower output voltage, while others may be too (it may exceed 20 or 30 seconds), and heavy and bulky to fit the space. Note therefore 1,000 pictures is set as an that a 6 -ohm resistor is in series with average. For the first 1,000 pictures the the filament of the 12 -A rectifier. This recovery time will not exceed 15 seconds resistor is necessary with the 9 volts of if proper care is used and the power battery as otherwise the filament of the unit turned off quickly when not in use. tube would burn out. The unit was built into a standard The battery voltage was chosen be- 7 x 8 x 12 -inch metal portable carrying cause it took 9 volts to get sufficient out- case, obtainable from any radio parts put with the particular power trans- jobber. As shown in Photo C the parts former used. Some transformers will fit into this case without overcrowding work with 6 or 7.5 volts; and if such a and with little wasted space. Since transformer is available, battery voltage some of the parts used were salvaged may be adjusted accordingly. from other equipment, no dimensions or Photo E- Another view of camera and flash - chassis layout will be given other than Switching Arrangement lamp. How- that shown in the photographs. The main control switch consists of assembled from Mallory ever, those who may wish to construct sections taken three sections. Each section is really from two switches. See 3. a similar unit should have no trouble other Fig. four separate s.p.d.t. units. In addition, This is not a stock item, but a two - in working out their own dimensions if there is an Off position in which all con- gang having the general parts layout shown in the switch similar charac- is followed. teristics is available. Two of these units various photographs may be assembled into one -gang are shown on the wiring three Connections switch by sawing off the spacing wash- power unlit, cam- diagram for the the ers and spacing the sections closer to- era mechanism and a separate a.c. pow- gether. It is very important to nóte the er supply to replace the batteries. This particular sequence to be followed in power supply permits use of the unit merely pull- wiring each section ., of this switch to where a.c. is available by keep the potential ing out plug on differences between the shorting the front adjacent contacts to a minimum. and plugging in the a.c. power unit Since power only ten sections of the switch are used which will then supply in place in series -parallel condenser of the batteries. The batteries need not transfer, this leaves two sections unused.. One of be removed from the case. Use of such these is used as power switch a power supply saves batteries for use a in the primary (battery) circuit, while the where a.c. is unavailable. other is to While a standard autoradio power used switch the meter ranges from 0 -15 to 0 -600 volts transformer and vibrator are used, it by shifting be- Photo D -The voltage supply, camera and lamp. tween the two multipliers RI and R2. will be noted that a type 12 -A tube is The meter thus used with grid and plate connected to- tacts are broken. This position is not reads plate voltage gether as a half -wave rectifier. Either a shown in the diagram. There are two when the capaci- 12 -A or 71 -A may be used, but the 12-A live switch positions. The upper switch gives slightly higher output voltage. tors are being position is Off with all units disconnect- charged, and ' fila- The 12 -A was chosen for its low filament ed; the middle (as shown in the wiring ment voltage when current and quick heating characteris- diagram) is the Charge position, in the switch is in the tics, and also because it is so construct- which the capacitors are charged in par- firing position. The allel; and the lower is the Discharge meter used is a war surplus de- .SHUTTER RELAY sROTARY item SHUTTER signed for aircraft Fig. 3- Switch detail. (MERCURY) use and has a lu- III Or minous scale which permits operation in SHUTIER yel v-SHUT TER SW. an indication RELEASE O O total darkness. This gives CABLE C[tj bl ba. of battery condition at all times and also gr 54C4 serves as a warning not to leave the power switch in either the middle or red - 6PRONG PLUG lower position, which would result in rapid exhaustion of the batteries. The MODELLING LIGHT meter is mounted on top of the case for easy visibility, in one model. Fig. 2- Diagram of camera and lamp extension. A fuse has been included in the primary circuit. It could be omitted. with- position. When the switch is in the low- out affecting the operation of the unit, er position the capacitors are dis- but it is desirable to protect the rest charged in series through the flash lamp. of the circuit in case the vibrator points The flash is fired through the action should stick. About 15 amperes is the of two separate relays. See Fig. 2. The correct value. shutter relay mounted on the reflector, A modeling light is built into the flash housing the flash bulb first trips the reflector to permit focusing the camera camera shutter, then the shutter trips in darkness. This light is controlled by the firing relay. This synchronizes light an on -off switch on the front panel of and shutter so that the flash occurs the power unit. It will be noted that it with the shutter wide open. The firing burns only when the main switch is in relay is mounted on top of the power the Charge position. A small 6-cp minia- Photo C-A back -panel view of the equipment. transformer on a small piece of Lucite, (Continued on page 53) RADIO -CRAFT for FEBRUAR Y, 1947 23

www.americanradiohistory.com By JAMES A. NILAND*

TELEGUIDED MISSILES

N0 example of American technical scientific knowledge of radiation. ingenuity is more spectacular Later, two of the planes that than aircraft remote control. Be- were used at Bikini were gun as a plaything, it has been flown 2,600 over -water miles perfected by wartime research and now from Hawaii to California. as a weapon of war it may greatly re- Arriving off Santa Rosa vise tactical and theoretical military Island, one oftheplanes U.S.A.A.F. Photo thought. In common with other in- dropped a smoke Model of a projected supersonic rocket -pro- ventions developed primarily for war, bomb. The flight of these two B -17's was pelled radio- controlled plane of the future. it also will have valuable civilian use. radio -controlled from start to finish. use. See illustration in "Radio Target The use of radio -controlled airplanes The various setups in which remote Planes," RAmo-CitiFT, January, 1945. early interested the Army Air Forces control may be applied to aircraft are Levers on the box allow for any combi- because of their suitability as targets. basically similar. The channel of com- nation of plane functions, such as Sleeve targets towed behind other air- munication between the controlled and throttle control, raising and lowering craft only partially performed their controling airplanes, known as the flaps, etc. function: they were unrealistic and drone and mother respectively, is a While the range of control varies presented a hazard to the pilot of the specially designed transmitter and re- with conditions affecting radio recep- towing aircraft, often at the mercy of ceiver system. Controls on the drone are tion, control can be achieved up to a an unskilled marksman. operated by servo motors either through distance of '75 miles. Usually the take- A target aircraft, on the other hand, the airplane's automatic pilot or di- off of the drone is supervised by an realistic in every detail and Controlled rectly from the transmitter. The servo operator in a jeep -installed ground sta- by a pilot in another plane hovering at motors are activated by radio impulses tion. After the drone is airborne and a safe distance, could create the proper in accordance with the desires of the has climbed to an altitude of about 400 illusion. It could supply to the airborne controlling pilot. Practically any ma- feet the mother plane takes over. machine gunner, as well as the anti- neuver within the capabilities of the Under normal circumstances the aircraft gunner on the ground, with a plane may thus be accomplished. drone's altitude is automatically con- maneuvering target to spur him on to A two -view television set in the drone trolled by altimeter equipment specially his best efforts. is trained both on the aircraft's in- installed for that purpose. However, the The flight-testing of new aircraft too strument panel and the outside atmos- altimeter setting may be over -ridden, often has seen a plane go into a power phere. By flipping a switch the con- when necessary, by a special relay box. dive out of which the pilot was unable trolling pilot may visually examine im- The receiver- selector in the drone in- to level off. Crashing to earth the life portant dials and gages, as if he were cludes an eight -channel audio filter se- of the pilot was not the only loss suf- actually in the pilot's seat of the drone. lector circuit to discriminate between fered. The reason for the crash often The brains of the radio control system the various tones received. A relay unit remained a mystery, concealed in the are incorporated in an ingenious five - passes control voltages to the automatic shattered fragments of the plane and pound box, known as the beeper, because pilot from the receiver output. the dead brain of the pilot. of the bird -like sounds it emits when in (Continued on page 56) Today, plans can be test -flown without pilots aboard. The, most difficult flight maneuvers are accomplished by REMOTE CONTROL INDICATOR LIGHTS AND SWITCHES BC-617 REC. radio direction, with the reactions of MOTOR- THROTTLE CONTROL BOX - BAROMETRIC ALTIMETER the plane telemetered to the ground as TURBO-BOOST TRANS SWITCH MOTE CONT. TRIM UNIT they occur. If the airplane crashes, the POWER IGNITION DISCONNECT RUDDER MOTOR PROP. PITCH CONTROL TURBO TRIM UNIT reason is no longer secret. Valuable UNIT data CONTROL BOX AIR FILTER UNIT CONVERSION has been gathered and recorded and RELAY UNIT serves as the basis for improvements in ALTIMETER SCR -7I8 TIME CLOCK MODIFIED/ BC-456 SCR-274 A-I subsequent models. RECEIVER BC -348 INTERPHONE 2 CAMERA During the war the Army Air Forces TURBO-SUPER CHARGER AMPL. AMPL. loaded war -weary B -17 Flying For- JUNCTION BOX TELEMETERING INSTR.PANEL tresses with high explosives and pur- INVERTER START SWITCH UNIT posely crashed them into high -priority TELEVISION TRANSM. NVERSION German targets. Naturally no pilots TUNING UNITS AUX.POWER RE-26/AXT- 3 were aboard. The 'pilotless American C-I AUi0 -PILOT Kamikazes were radio -directed to their RC-103 ST ABILIZER -BRA KE M0T00. destinations by other B -17's. At that INVERTER ASSEMBLY time the remote control system was AIR SAMPLER not -17 CAMERA SCOOP d VALVE -K developed sufficiently to get the planes AUX. FUNCTION AIR SAMPLER off the ground by radio. Token crews RELAY BOX RECORDING took the planes up and parachuted to AIR SAMPLER METERS FLIGHT GYRO d A MPL. RELEASE PANEL safety as soon as the control planes K 17 CAMERA -MG-149 -F took over. DYNAMOTOR JUNCTION BOX I AUTO -PILOT Tile airplanes that flew through the RADAR TRANSM TIER TURBO-SUPERCHARGER C JUNCTION BOX atomic cloud at Bikini were controlled AMPL.12 PLUS I ABOVE/ entirely by radio; and the data their in- POWER BOX STATION 6 -RADIO COMPASS struments gathered has SCR-522 VHF COMMAND -GLIDE-PATH RECEIVER contributed to RECEIVER-TRANSMITTER ^FLIGHT ANALYZER *Information and Public Relations, Headquarters The B -17, adapted to act as a super -weight flying bomb, completely controlled by radio. Army Air Forces, New York, N. Y. 24 RADIO -CRAFT for- FEBRUARY, 1947

www.americanradiohistory.com PROBLEMS OF INSTABILIT

By TED POWELL

ONE of the perplexing problems control, industrial process, encountered in radio and communication, television, sound work by servicemen, is navigational and radar equip- circuit instability which some- ment are too complex to be times develops in equipment which has predicted in advance or too apparently been serviced properly. difficult for theoretical solu- Circuit stability is governed by either tion with the mathematical of two circuit conditions, positive feed- tools available. These com- back (regeneration) or negative feed- plex unpredictables constitute back (degeneration). Regeneration Is the well -known "bugs," gen- often deliberately introduced into r.f. erally more readily handled by means suppressed by altering the power factor . or i.f. amplifier circuits in controlled of trial- and -error models and graphical of one or two of the amplifier tube plate amounts to increase the available gain methods than by pure calculation. or screen -grid voltage supply circuits. 'and sharpness of tuning. Similarly, de- Persistent circuit instability results This can be done by inserting an r.f. generation may be introduced into cir- as much from mechanical arrangement choke or by eliminating or changing an cuits-in controlled amounts to reduce and resulting' stray- coupling factors as isolating resistor or by -pass condenser; hum and certain types of distortion and from the principal circuit constants introducing cathode degeneration by to suppress oscillation tendencies. themselves. In such cases, the usual and lowering or omitting the cathode resis- Under certain conditions,, regenera- obviöus by -pass filtering, shielding, low- tor by -pass condenser or inserting an tive and degenerative coupling effects ering of amplifier tube electrode volt- r.f. choke in one or two of the cathode may exactly cancel each other out at a ages result only in a change of over- circuits; adding or omitting some of certain frequency or frequency range all oscillation frequency. The final al- the shielding in one or two stages; re- to produce extremely stable circuit ternative is to re- arrange the wiring, arranging some of the wiring, com- operation. components and shielding on the chassis ponents or shielding in some of the in a trial- and -error routine till the stages; inserting r.f. chokes in series Four Kinds of Coupling greatest freedom from Regeneration stray coupling with the voltage supply busses to one or degeneration effects is determined experimentally. or two of the amplifier stages. The may be brought about by any of four A few simple alternatives may suc- circuit coupling power factor of the grid or plate coil or factors -conduction or cessfully eliminate the perplexing and resistor load circuits one electron coupling; inductive of or two of or mag- involved instability "bug" when it crops the stages may be altered by shunting netic coupling; capacitative or electro- up under certain favorable conditions. them with static coupling (in choke, condenser and resis- the case of hyper - In multi -stage high gain r.f. or i.f. am- tor networks; inserting small frequency circuits, by damping radiation or elec- plifiers, oscillation can sometimes be (Continued on page 66) tromagnetic coupling) and various combinations of these coupling factors. Conduction coupling may take place via common amplifier -tube electrode voltage -supply circuits, common grid - bias cathode -resistor circuits, common chassis ground returns, common ground bus leads, and in rare cases, via dielectric leakage paths. Although the d.c. ohmic resistances of chassis and wiring runs are measured in extremely small fractions of one ohm, their a.c. impedances are considerably greater, especially at radio frequencies. Inductive coupling by magnetic fields around transformers, chokes and current- carrying conductors can cause ' considerable instability trouble in high - gain amplifiers and inadequately shielded circuits. Capacity coupling becomes rapidly more severe with increase in signal frequency. At microwave frequencies, two wire ends facing each other serve as an effective capacitance. (Two polished parallel No. 10 conductor wire ends separated by 1 /10th inch, have a very small capacitance of about .00018 micromicrofarad, but at a hyper - frequency range of 30,000 me have a capacitative reactance [a.c. impedance] of only about 3000 ohms.) Certain design factors in electronic Werner's SerJice Shop, Binghampton, N. Y., is an example of a small but efficient layout.

RADIO -CRAFT for FEBRUARY, 1947 25

www.americanradiohistory.com By J. C. HOADLEY

SMALL RECORDING STUDIO Part I - Microphone, Recorder, Turntable and Pickup

IT is entirely feasible to equip a re- 8. An all -wave AM receiver and an FM interfering with either the recordist or cording studio without the expendi- receiver are desirable. the artist. It would be highly desirable ture of a small fortune. When we to provide a receptionist or secretary to reduce the prospective studio to its It is assumed that adequate space is meet customers. bare essentials, we find that we need the already available, preferably with three We are, in this article, primarily con- necessary equipment to make and play rooms. The recording equipment should cerned with the equipment necessary to back a good recording or transcription. preferably be placed in a room by itself, make a good recording. These essentials would be, in the or- to insulate the recording artist from the For this we must first have a turn- der of their importance: distraction of watching the business of table and motor assembly. The selection making a record and to insure that the of this item deserves our deepest con-

1. A 16-inch dual -speed motor and turn- attendant noises will not . mar the re- sideration. It is possible to cut corners table assembly. cording. nearly everywhere else, but we cannot 2. Rugged leadscrew assembly, prefer- The second space consists of the turn out good recordings with a poor. ably of the overhead type, and a good actual studio. It should contain several turntable. It must neither introduce cutting head. microphone outlets to reduce the possi- wow (which is a change of speed within 3. High- fidelity, low- distortion ampli- bility of tripping over the cord. A piano one revolution) nor slow down under fier with adequate power capabilities is a must, if musical recording is con- the pressure of the cutting head. Both not only for recording, but also for templated. The studio should be par= of these deficiencies will be noticeable ,playback. , tially lined with absorbent material. to even the most uncritical customer. 4. High quality playback pickup. One end of the studio might be so lined Wow is greatly reduced in a turntable b. , Playback speaker system, preferably and the other end left reflective. This that has great mass. Sixteen -inch tables of the dual -speaker type. would provide a versatile arrangement usually are made of cast iron and weigh 6. One or more high -quality micro- where the acoustics of a large hall or from twenty to fifty pounds. The drive phones and an acoustically treated outdoors may be simulated. motor should have adequate power, so room for the actual recording. ' The third space is the reception and as not to slow under the load of the 7. A second turntable and playback waiting room. There has to be a space cutter, and should have a continuous - pickup for re- recording and dubbing where the clerical business of a record -. duty rating of at least 1/30 horse- purposes. . ing studio can be conducted without power.

Courtesy Brush Development Co.

Courtesy Amperite Co.

Fig. I, left-Velocity microphone and typical field pattern. Righi- Cardioid field pattern with representative microphone of this type. Top photo- Non -directional sound cell microphone; bottom-standard dynamic type.

26 RADIO -CRAFT for FEBRUARY. 1947

www.americanradiohistory.com 6SN7 CONSTANT VELOCITY 6SJ7 VOLT. AMPL. NST. AMPL. MIXER 36K +20 20 15 INPUT N °I ± 2 RX 33K MONITOR HONES 20K

70 A INPOT TRWa T0 SPKRS SOOK 0 XTAL CUTTER BRUSH LOCAL MIKE IN. RC-20

6SJ7 SK TREBLE' 20 2 LBK smog 1350V. 8 SUPPLY 000` 6 5U4-G yo II 2 1 &SV. X FlLS - - 7' r- 1-4 al o -- 20 K INPUT N°2 .25 aY + 20 + o--IF5 + +_ir =s ti BRUSH EQUALIZER o-ßF-- TO PL-20 XTOseaIP F1ATo 116.3V FIL. TRANS. SEC. 6.3V. 3A. 40MA +50[V., 1 AMP SELENIUM RECT. X FM AM ár 250V. 250V. PICKUP N°2 0010000 Fig. 2 -The author's recording amplifier. A standard type may Q11D00. modifications, for recording. purposes. be used, with slight 1RM-1 117 V AC 000' ,1171LAC

117 XII RECORDING MOTOR POWER SS The leadscrew assembly which is to T drive the recording head across the rec- 117 ord should be rugged and without play of any kind. The overhead type is usu- the recording characteristic, which the cost is prohibitive, a good 12 -inch ally preferable. should be taken into account when the dual speed turntable, together with a There are many cutting heads to recording is made. pickup suitable for playing 16 -inch choose from. They range from six dol- A high -quality playback speaker in a records, can be used for dubbing and lars to several hundred. There cari be good baffle is a necessity to do justice copying. It is essential that this turn- no doubt that when cost is a factor, the to the playing of your best recordings. table be free of wow and speed varia- crystal type will provide the best re- An extended -range eight -inch speaker tions. sults. It is equally certain that the finer in a bass -reflex baffle is offered by at We will need several microphones. magnetic types will provide the very least one large manufacturer for less The types selected will depend upon best quality. than twenty -five dollars, although the their intended use. For music, a velocity The next most important item is our more expensive coaxial types would be type is considered good. Superb, also, amplifier. It should be of the highest more desirable. The minimum require- are the several cardioid types and the quality you can afford. In the interest ment of the speaker system is that it be sound -cell crystals. For voice recording, of economy, it might be well to con- reasonably flat from 50 to 8000 cycles, the crystal and dynamic types are pref- struct your own. and it would be desirable to have the erable. The crystal types are the most This amplifier should provide several range flat from 40 to 12,000 cycles per inexpensive in original cost. channels feeding a stage containing second. Several different pickup patterns are high- and low- frequency compensation, It would be desirable to provide a available in the different types and the which, in turn, feed an output stage duplicate 16 -inch turntable and over- microphones should be chosen with this capable of at least ten or fifteen watts head system so that continuous record- 'pattern in mind. Fig. 1 shows the pick - at a maximum of two percent distor- ings, could be made. In the event that (Continued on page 52) tion. Switching should be provided for several recording characteristics. Means should also be provided to monitor the output of the amplifier. An a.c. voltmeter, with a flat frequency response and plainly marked as to the maximum level that may be safely applied to the record, should be permanently connected to the amplifier's output. Also, it is desirable to provide audible monitoring by headphones or speaker. A suitable playback pickup must be provided. Again, there are many choices. The crystal types provide the best performance when cost is a prime factor. The magnetic and dynamic types cost much more, but can have wider range and lower distortion. In the interest of simplicity of compensation, it is desirable to use the same type of cutter head and playback pickup. It is significant that the average user of 10- and 12 -inch records will use a crystal pickup, whereas the user of 16 -inch transcriptions usually uses a magnetic or dynamic type. There is a profound difference in Heart of the recording assembly. Sturdiness and freedom from any play are important here. RADIO -CRAFT for FEBRUARY, 1947 27

www.americanradiohistory.com By ROY FREELAND

BUILDING A TELEVISER Part II -The Sound Section Is a Good FM Receiver

THIS receiver is the sound section No. 14 wire. A piece of spaghetti tubing third, and fourth video i.f. transformers of the televiser described in last is slipped over each coil, and they are are constructed and wired as shown in month's issue. Full winding data coupled as closely as possible. Fig. 3 -a. The windings and condenser for all tuning coils as well as audio The oscillator coils L10, L11, and L12 values are: and video i.f. transformers are given in are wound with No. 14 enamel wire as this article. The set may be used as a LA (L18, L21, L24); 23.5 turns, No. 30 follows: L10, 6 turns; L11, 4 turns; enamel straight FM receiver on the new chan- and L12, 1 turn. nels if slightly modified. Notes on wind- LB (L19, L22, L25); 41 turns, No. 30 All the coils are self-supporting, 7iá - enamel ing coils to cover these channels are in- inch in diameter, and spaced as re- cluded hire. LC (L20, L23, L26) ; same as LA quired to hit the desired band. CA (C22, C24, C31); 3 -25 µµf variable The mixer grid circuit coils are wound CB (C18, C26, C33); 3 -25 µµf variable as shown in Fig. 2. Winding data fol- (Set approx. 22 µµf) lows: CC (C19, C27, C34); 3 -25 µµf variable

Colle Turns Wire Size LB G lG LA (LI, L4, L7) 1 No.14 enamel LA*,, G LB (L2,L5) 4 No. 26 enamel (L8) 2 No. 26 enamel !Intl LC (L3) 4 No. 26 enamel IIi (L6) 3 No. 26 enamel 2'h-vd" d (L9) 2 No. 26 enamel I Fig. 2- Winding details of mixer grid coils. Coil LA is center -tapped. The first, fifth, and sixth video i.f. Position 1 of SW2 covers channels 1 transformers are constructed as shown Photo A-The composite end video i.f.f.'s. and 2; position 2, channels 3 and 4; in Fig. 3 -b. The coil winding data are: position 3, channels 5 and 6. The oscillator feed -back coil L13 -P14 Coils Turns Wire Size (Fig. 1) consists of a 1 -turn primary Construction of the video and sound LA (L16, L29, L32) 21 No. 28 enamel and 1 -turn secondary, each % inch in i.f. transformers is perhaps the biggest LB (L15, L27, L30) 29 No. 32 enamel diameter. Both coils are wound with task in building the set. The second, LC (L17, L28, L31) 23 No. 32 enamel

VI, MIXER,V20,V21, I.F. AMPLIFIERS. 6AC7 R209 Ç209í C2IO _.R210 V22,LIMITER, 6SJ7 V23,DISCRIMINATOR. 6H 6 R213 V22

TI* --RB---TC82 y¡ Lf6 AUDO ÁMPL. a216 C2I9

VI LISL TRANSPOSED LEADS TO ANT. R61

R5 C217j R215 C218 LI L2 CI 1.3 L

RI CIOx CII

C9 U2 íR7 *SEE TEXT JANUARY 1947 ISSUE 4 FILS

CH 101 B4250V. r CONTRAST CONT. BIAS, C42 C101 C102 C103 R101X La SECTION DOUBLE POLE T2 VI9 3 POS. SW. S2 V2 6J5 ,B+ Sv. 80 IT ó

R20

C7 C8 SW 6.3 V.

L13 LI4 III V. AC

Fig. I-- Complete sound section of the television receiver, including the mixer section which was also printed in last month's figure. 28 RADIO -CRAFT for FEBRUARY,. 1947

www.americanradiohistory.com The construction and placement of inches long, if properly isolated from T1 and T2 are shown in Photo A. magnetic fields, should give no hum The sound i.f. and discriminator pickup. transformers are wound on 1 -inch Construction details for the sound forms with the windings spaced as unit i.f. and discriminator transformers shown in Fig. 3 -c. The primary wind- are shown in the photograph of the ings L38, L40, and L42, and the second- sound unit (Photo B). The sound i.f. ary windings L39, L41, and L43 are all signal is fed from the mixer to the wound with 23 turns of No. 32 enamej sound unit through a length of 72 -ohm wire. L43, the secondary of the discrim- co -axial cable. The inator transformer T11, is center- audio output from tapped. All of the video and audio i.f. the sound unit is 3 I5/16" 4 1 13/4 are mounted in standard, 3/4 transformers sufficient to drive 13/16 shielded i.f. transformer cans. the phonograph in- w---13/16 4-9/I6V4 15/16 7/164--15/16 V4H-9/I Air trimmers are recommended for put circuit of any LA LB LC the i.f. and discriminator transformers; average broadcast however, mica trimmers may be used if receiver. If desired, CHASSIS 2 desired. the builder can add END The peaking coils L33, L34, L35, L36, his own audio DIMENSIONS IN INCHES and L37 for the detector and video am- stages. Fig. 3 a- Winding details for T2, T3 and T4. plifier circuits may be purchased com- fiCOND.C13, GND P 8+GND G mercially in the proper value, or they DIMENSIONS C45,0RC49. LA LB LC may be wound. The coils are wound 'as PRI. IN INCHES follows: L33 and L35, 280 turns; L34, TCHASSIS 155 turns; L36, 230 turns; and L37, 110 1 I END turns. All coils are wound on 1/2-inch i 1 __ t bakelite forms with No. 38 enameled I4-_ 64} I r3/4 h13/16 -+I ik-III /I6-1 13/16 wire. To insure wide -band operation t DIMENSIONS V8 ill+lk 3/I6 IN INCHES from the video detector and amplifier THIS DIM. IS 1/4 ON III CHASSIS END -2 V2 stages, the lead capacitance should be Fig. 3 -c -The sound i.f.'s and discriminator. kept to a minimum. Fig. 3-6-Winding details for TI, TS and T6. The oscillator vertical transformer to 8.25 me and adjust the trimmers on T7 is wound on an iron core salvaged Alignment of the Sound Receiver transformer T11 for resonance which from a small a.f. transformer or a.c.- The alignment of the receiver is some- will be indicated by zero reading on the d.c. filter choke. The outside of the core what difficult and, for accurate results, meter. Next set signal to measures approximately the generator 11 inch on requires equipment not readily avail- about 8.35 mc, and note the meter read - each side. The center leg is about 1 x The align- able to the average builder. O 3/ x % inch. Both windings are wound ment method described here is long and 8 GRID in the same direction with No. 32 enamel rather tedious but yields good results. PRI.IOGT. N°32 ENAM. wire. The primary has 100 turns and + SEC. 2001.. N °32 ENAM. The following equipment will be re- the secondary has 200 turns. Wiring PLATE- quired: a calibrated r.f. signal gen- N.B.:BOTH WINDINGS connections are shown in Fig. 4. IN SAME DIRECTION erator capable of covering the range -GRID RETURN from 8 to 20 mc; if possible, an r.f. Fig. 4 -The vertical oscillator transformer. T9-. V20 signal generator to cover the range from 44 to 88 mc; a 0 -1 milliammeter; and an oscilloscope or v.t.v.m. for out- No,:Imizzomms put indicator. Both signal generators should have provision for modulation of IlliHlilhil, the signal (about 400 cycles), and the +100+I 0+ i output should remain substantially con- Im....m stant over the frequency range to be 11111MICIMINUNIMI covered. The sound unit should be aligned first, since it will be used later in the final adjustment of the receiver. Insert 11 the milliammeter between the lower end -V LTS of the limiter grid resistor R211 and 8.25 -mc into &15MC 8. 5MC 8ä5MC Photo B-- Construction of i.f. transformers. ground. Feed an r.f. signal the grid circuit of V20 through a 50- Fig. 5-The ideal discriminator tuning curve. Wiring Notes µµf capacitor. Adjust the trimmers on ing (reverse connections to the meter When wiring the i.f. stages, all transformers T9 and T10 for maximum if the reading is downward). Set the ground connections for one stage should indication on the meter. Throughout signal generator to about 8.15 mc, and be returned to a common point. Care the alignment always use the minimum again note the meter reading. The two should be taken to isolate each stage. output from the signal generator that readings should be the same. If they Good quality carbon resistors should be will give a readable signal on the out- are not, readjust the primary trimmer used and connections should be well put indicator. Rock the signal genera- C214. After readjusting C214 check to soldered to keep circuit noise to a mini- tor 100 kc each side of 8.26 mc, and note see that the meter reading is zero at mum. Noise developed in the video cir- the reading on the meter. The output 8.25 mc. In general, C215 will affect the cuits will make the picture appear of the sound unit should remain fairly zero response frequency while C214 will grainy. constant over the 200 -kc band width. If affect the symmetry of the discrimina- Precautions should be taken to keep it does not, readjust the trimmers on tor peaks. A cut -and -try adjustment of 60- and 120 -cycle hum out of the picture the transformers while rocking the both trimmers will produce a satisfac- by placing wires carefully. Hum picked signal generator through the 200" kc tory curve similar to Fig. 5. up in the video circuits will appear as until a fairly constant output is ob- Remove the meter and reconnect black bars across the picture, while hum tained over the tuning range. R211. Remove the signal generator and picked up in the sweep circuits will Remove the meter and reconnect R211 connect the sound unit to the main re- cause a wavy edge on the raster. The to ground. Insert the meter in series ceiver chassis (i.f. co-axial line). Con- grid lead to the picture tube should be with R214 in the output of the discrim- nect the output of the sound unit to an as short as possible. A lead 10 to 12 inator ciréuit. Set the signal generator (Continued on page 62)

RADIO -CRAFT for FEBRUARY , I 9 4 7 ' 29

www.americanradiohistory.com By MERRILL LINDLEY

HAM STATION FROM SURPLUS Sow to Convert the No. 19, Mark II, to A.C. Operation

HE No. 19, Mark II, receiver and 240 -mc amateur bands. Set C is a 2 -tube relays must be operated from a transmitter set, a popular piece of interphone amplifier using a 6K7 -G and 12 -volt d.c. supply. The a.c.-d.c. supply radio equipment among experi- a 6V6 -G. shown in Fig. 3 uses a 117Z6 in a half- Tmenters and amateurs, is readily The transmitter of Set A uses the wave rectifier circuit. Its output is available on surplus radio markets. It hexode section of a 6K8 -G, V2B, as a tapped to supply 12 volts d.c. for the was built for use in Russian and British variable- frequency oscillator working relays. (This supply may be replaced tanks (dial and panel markings are in into an EF50 buffer amplifier. The final by two 6 -volt Hot -Shot batteries con- Russian and English) and is designed amplifier is an 807. The 6H6 is used as nected in series. They will last for to be powered from a 12 -volt vehicular an automatic drive control rectifier and months. The current drain is only 120 storage battery. The entire unit may be meter rectifier. The receiver uses a ma.) obtained complete with microphones, 6K7 -G r.f. amplifier, 6K8 -G oscillator - headphones, diagrams, and other ac- mixer followed by two 6K7 -G i.f. stages Circuit Alterations cessories. The purchaser should be espe- and .a 6B8 -G detector, a.v.c. and a.f. - The blue wire, connected between re- cially sure to obtain the schematics - amplifier. The pentode section of the lay L19A and the filament pin of the they are too large to reproduce here. 6B8-G is the modulator for radiotele- 807, V4A, is disconnected at the socket. By constructing suitable a.c. power sup- phone transmission and as the tone oscillator -modulator for m.c.w. The tri- w.." 0550% _2 L 5Z3/ s% 80/5Y3 ode section of V2B is the b.f.o. when receiving c.w. 550V. 'wi10N,100W n7V.AC 30H,110 IRA Set B consists of an E1148 high -fre- 6+ 350V. quency triode, two 6K7 -G's, and a 2° 25Ií 6V6 -G. When transmitting, the E1148 251 is a v.h.f. oscillator modulated by the 8= output of the 6V6 -G. -G, The 6K7 V1E, Fig. 2 -Power supply for the amplifier stage. is used as the microphone preamplifier. FIL.TRANS, When receiving, the E1148 is supplied The blue lead with black tracer is dis- 6.3V. with a 158- to 228 -kc quench voltage connected from the No. 7 pin of the generated by the 6K7 -G, V1D. The 6K7 -G, V1E. These loose ends are 6.3V. 6K7-G and 6V6 -G are a.f. amplifier and soldered together and brought out to a FIL.TRANS. power amplifiers, respectively.

Fig. I -The low-voltage power supply section. The interphone amplifier (Set C) has II7Z6 a 6K7 -G speech amplifier driving a plies, the owner of the Mark II may 6V6 -G power amplifier. adapt it for fixed station operation if The set may be operated from 117 - 5w. 1011,110 MA volt a.c. lines by he desires. using three small power `ÖÚÖ- The Mark II is units supplies and making two minor changes 117V. 1511 essentially three ,r2o N. 1 50W. in one. Set A is a complete 2- to 8 -mc in the control circuits. The power sup- .1 op 250v. 250V T 12V. OC voice and c.w. transmitting and receiv- ply in Fig. 1 delivers 275 volts at 110 - CHASSIS T - 40- ma to operate ing station covering the 80- and all tubes except the 807 Fig. 3 -A 12 -volt rectifier -type bias supply. meter amateur bands. The transmitter power amplifier of the transmitter. Two has a power output of 30 watts c.w. and 6.3 -volt 4- ampere filament transformers binding post on the front panel. The 5 watts voice. The transmitter uses a are connected in series -aiding to provide positive side of the 12 -volt d.c. supply m.o.p.a. circuit with the frequency con- 12 volts a.c. for the tube filaments. is connected to the binding post. trol ganged to the tuning control of a Regulation of the high-voltage section The negative side of the d.c. supply 6 -tube superheterodyne receiver. Set B of this supply must be good because the is connected to the chassis of the set. is a 4- tube.transceiver tuning from 230 stability of the variable- frequency oscil- (This supply should be polarized so that to 240 mc, thus covering the 235 - to lators depends upon constant voltage. the grounded side oi the a.c. line is al- T h e power -am- ways connected to the chassis of the set. plifier plate supply -Editor) is shown in Fig. 2. The receiver section may be improved It delivers 600 volts for amateur operation by providing with a load of 50 - manual r.f. gain control and including ma. Since the cur- a switch to ground the a.v.c. line when rent required is receiving c.w. signals. These changes comparatively low, may be made by comparing Fig. 4 with regulation may be the original schematic that accompanies improved by using the set. The cathode resistors of VIA a heavy bleeder and V1B are disconnected from ground across the high - and tied to the arm of a 20,000 -ohm voltage output. - potentiometer. One leg of the control is The circuits are connected to ground so that the r.f. gain switched from re- increases as the control knob is turned ceive to transmit clockwise. The a.v.c. line may be by control relays grounded by connecting a switch be- L19A and L19B in tween the junction of L10A and R8B Sets A and B, re- and ground. When the switch is open, zhed on page A front view of the No. 19, Mark II. The markings are bilingual. spectively. These (Conti 80)

30 RADIO -CRAFT for FEBRUARY, 1947

www.americanradiohistory.com Byi MILTON S. KIVER

TELEVISION FOR TODAY Part IX - D. C. Reinsertion and Image Synchronization

ANALYSIS of the video signal adjusts itself so that the areas above the same level. The purpose of the (in a preceding article) indi- and below the zero reference line are blanking pulses is to drive the control cated that it consists of two equal, this being true of all a.c. waves. grid of the cathode -ray tube to cut- parts: an a.c. and a d.c. com- What would be the effect of a missing off. However, with the pulses at various ponent. The a.c. component governs the d.c. component upon the final image? levels, it becomes necessary to bias the variation in detail from point to point, First, there would be no exact way of cathode -ray tube (with the brightness whereas the d.c. component governs the determining what the true average control) to such a value that most over -all background illumination of the background brightness is, since this is blanking pulses, in their new position, received image. We may look upon this a direct function of the d.c. component. cause cut -off. latter component as an over-all inten- Imagine two studio scenes, alike in Finally, every cathode -ray tube has a sity control, automatic in the receiver, every detail except the over -all light- certain characteristic curve. For a but adjustable at the broadcast studio ing. Assume that one scene is strongly definite input voltage, a certain beam according to the dictates of the produc- illuminated while the general illumina- current is obtained and a related tion manager. The transmitted and re- tion on the other is low. Examination amount of light appears on the screen. ceived signals. contain this d.c. compo- of the resulting video signal would re- To obtain repeated appearances of any nent and it is only in the output of the veal that they differed substantially one shade requires the application of second detector when the r.f. has been only in the amount of d.c. component the same voltage each time. This is not removed that we need give it special contained in each. The illustration in possible unless one reference level is attention. This becomes evident when Fig. 2, might very well present this used throughout. It is here that the d.c. we consider the nature of the video situation. component is useful. By reinserting amplifiers that follow the video detector With no d.c. component, both the this voltage, all blanking and synchro- and the form of the video signal. above signals produce essentially the nizing pulses are maintained at the Video amplifiers are coupled by same image, with an average back- same level and the, associated image de- means of condensers. The d.c. compo- ground illumination based primarily tail is likewise oriented correctly. nent is automatically eliminated in pas- upon the various shades of the people, sage. Fig. 1 compares the forms of the .their clothing, and the objects in the Reinserting the D.C. video signal with and without the d.c. image. The d.c. component may be reinserted, component. In one instance, Fig. 1 -a, As a general statement, the d.c. com- if it has been removed, because removal the synchronizing pulses are on one ponent controls the image sensation of this component . does not alter the level and the three degrees of inten- more in the regions of high brightness, shape of the video signal, but merely sity (white, grey, and dark) are proper- while the a.c. component produces a its reference level. Re- examine Fig. 1. ly oriented with reference to the top- greater effect in the low intensity re- If we could somehow raise each syn- most or black level. In the second illus- gion. Hence, removal of the d.c. corn - chronizing pulse of the a.c. video signal tration, Fig.. 1 -b, the d.c. component ponent will produce a darker image. back to the same level, then the video has been removed and the synchroniz- Secondly, with the removal of the d.c. detail electrically associated with that ing pedestals are no longer aligned to component, the blanking and synchro- pulse would likewise readjust itself. one level. Without the d.c., the wave nizing pulses are no longer aligned to Two methods are in common use for d.c. reinsertion. Both develop a variable bias which, when placed in series with the video signal, replaces the previously - REFERENCE AXIS lost d.c. component. The simplest cir- DARK G,AY WHITE cuit is shown in Fig. 3. The d.c. reinsertion (required only in video 0 the final - DARK my amplifier) is obtained from the com- WHITE bination of zero cathode potential plus Rg. I -A.c. and d.c. forms of a video signal (negative picture phase). grid -leak bias. The signal applied to the grid of this last amplifier is in the negative picture phase for proper orientation at the cathode -ray tube. In this form each synchronizing pulse possesses the most positive Fig. 2 -These two video signals are alike except for their d.c. level. potential of its line. This is very important, for on it depends the operation of the d.c. reinsertion network, Rg and Cc. The tube has no bias FINAL VIDEO AMPLIFIER CATHODE RAY TUBE other than that which appears across Rg, and the voltage at Rg is directly de- lrV EJ pendent upon the synchronizing pulses. tDC REINSTATED At each pulse the grid draws current and charges Cc. The condenser Re BRILLIANCE CONT. then -1M. discharges through R at a rate depend- ent on the time constant T =Rg x Cc. AC FORM OF SIG. - +H 6 +300V. By designing the network with a time r - oBt constant equal to or slightly greater Fig. 3 -In this circuit, Cc and Rg are the d.c. reinsertion components. than one horizontal line, we can force (Continued on page 72)

RADIO -CRAFT for FEBRUARY, 1947 31

www.americanradiohistory.com SIMPLE MODULATION METER A Simple Method for Obtaining Diverse Information

MANY modulation indicators netically. To check these troubles, short ground. It may be found impossible to have been designed, but few the deflection plates to ground; if this use the three -inch oscilloscope (because have the overall simplicity clears up the trouble, it is in the circuit, of a grounded deflection plate) except and accuracy of the cathode - probably due to application of a d.c. with single -ended transmitters. It is im- ray tube for discerning waveform, per- potential (as through a leaky conden- perative when using the five -inch or centage Of modulation, or deficient ser) to the deflection plates. Where this larger cathode -ray tube to use pushpull operation. does not clear up the trouble suspect deflection as previously mentioned; fail- The simplest modulation indicators magnetic fields. Check the surrounding ure to do so will result in a keystone employ either a diode tube, meter, or area with a small compass. Iron panels -neon lamp. These systems generally in- or the very deflection plates in the cath- ANT. XMR TERANTPOST dicate ' over -modulation only. Special ode ray tube may be magnetized. These a IMEG meter circuits may be employed to read R.F. INPUT --AMA- in percentage, but these are generally INTENS.ADJ. IOOK 500K expensive. Lo 5V. -50u0 SW. 80 V\ The use of a cathode -ray oscilloscope 1KV.00 600V 117V. to check percentage of modulation is 350V. ¡ AC 1 not new, many texts describing the IOOK Y Y familiar trapezoidal patterns produced 350V. I when r.f. and audio com- X 500K the signals are X bined properly in the instrument. E.3V. T FOCUS The required 1802-PI OR 902 équipment for these 200K = modulation tests is any standard cath- Y 6X 5 6àV. '1 ode -ray oscilloscope and a plain antenna Y or t.r.f. shortwave receiving coil. Where 5 AT SOCKET a commercial oscilloscope is not avail- Fig. I -The modulation percentage meter is able, it is possible to build a simple a simplified oscilloscope, and might be adapt- 7N7) modulation oscilloscope for relatively ed to general use by addition of amplifiers. little expense. Such an oscilloscope is 250K in a shown schematically, with this article may be demagnetized by placing r .01 (Fig. 1). Only three radio tubes plus strong a.c. field and slowly removing. SWEEP It FRED. S0K005 the cathode -ray tube are required. There may be. focusing difficulties. If ADJ. COARSE 'MEG . Power supply requirements are simpli- so, rotate the focus control towards the 600V.Apjo,;F fied by the use of one conventional mid- sharpest focus point. Then at the other AI 100H 1MEG ' get radio power transformer. Half -wave electrical end of the focus potentiometer 2MA rectification is used to supply the high add a 50,000 -ohm resistor so that more SYNC.IF DESIRED voltage for the cathode -ray tube. Use of voltage will be available in this direc- half the transformer to supply the high- tion. Follow up by backing off the con- indications of un- . voltage d.c. for the sweep circuit is a trol until focus is obtained. pattern with possible novel innovation, but perfectly satisfac- The primary side of the r.f. pickup symmetrical operation although it does tory and free of ripple where sufficient coil is connected to the antenna post of not exist. filtering is used. The sweep circuit em- the transmitter. Normally the loading There are two reasons for connecting ploys a high- vacuum tube which is inex- resistor or antenna is connected to the the secondary of the r.f. pickup coil pensive as compared with any of the other (unconnected) side of the primary directly to the deflection plates. The ver- gas -filled tubes normally used in these coil so that it is in series, effectively, tical deflection amplifier in standard circuits. The connection between the with the antenna lead coming from the oscilloscopes does not amplify much over sweep circuit and the cathode -ray tube transmitter. This primary eoil should 200 kc and thus is incapable of ampli- signal. is . control grid is to eliminate the flyback not be at a current node, but the exact fying the radio -frequency It sweep trace on the face of the cathode - location is not critical, there being noth- advisable to disconnect the oscilloscope ray tube. Normally synchronism of the ing to balance or adjust to cause the amplifier output tube from the deflec- sweep is not required, but input connec- indicator to show the correct percentage tion plates to reduce tube and wire cations are shown on the drawing, indicat- of modulation. Where the transmitter pacities to ground. Modern oscilloscopes ing where part of the audio signal may power is high, the primary winding may have disconnect links exposed on the be fed if sync is desired. be connected through a small isolating back of the unit for direct connection in- Positioning controls are not required condenser from the antenna post to to the deflection plates, making wiring for centering the trace. Manufacturing ground. changes unnecessary. When hooking di- tolerances center the beam within a The secondary of the coil should be rectly into the deflection plates, the ver- short distance of the screen center. If connected directly to the vertical deflec- tical positioning control is inoperative. the trace is not centered properly, look tion plates of the cathode -ray tube, with If the beam trace is too far from the first for a leaky coupling condenser be- all else (including the positioning con- center of the tube with this control dis- tween the sweep circuit and the deflec- trol) disconnected. If the oscilloscope connected, it is possible in some cases to tion plate. This condenser must show 20 tube is five inches or over, pushpull de- reconnect it and unwire the output tube megohms or higher, and for this reason flection (to be preferred) will be avail- connections to the deflection plates. it is often wise to use a mica condenser able. Here the secondary of the coil is Where positioning is obtained through in this section of the circuit. A loud- center- tapped (not critical) with the the *output tube by control of plate cur- speaker too close to the cathode nay tube outside connections going directly to the rent, this is not possible. may deflect the cathode-ray beam mag- deflection plates and the center tap to (Continued on page 58) 32 RADIO -CRAFT for FEBRUARY. 1947

www.americanradiohistory.com By 'I. QUEEN

ANTENNA PRINCIPLES Part III- I)ireetional Arrays and Radiation Fields

PREVIOUS articles described the Power is propagated only broadside propagation. The second figure is a operation of simple antenna sys- to the array. Assume that a wave starts view looking down on the antenna. tems suitable for broadcast re- out at some instant from one dipole. It A sharper beam can be transmitted ception and amateur operation. reaches the next dipole one -half cycle by using a still more complex array. More elaborate designs are used for later because of commercial communication and broad- the half -wave cast transmission. spacing. At this All practical antenna systems and ar- later instant the rays are directional to some extent. second dipole tends They may be grouped- in accordance to radiate a field with their characteristics as follows: which is out of 1. Those designed to receive or trans- phase with that mit along one or a few narrow beams which has just only. In other directions the system is reached it from the relatively ineffective. other. The two op- 2. Those producing an irregular pat- posite fields cancel tern. out along either di- 3. Arrays having circular patterns rection of the ar- in the horizontal plane. Actually these ray. A receiving types are directional with little propa- a n t e,n n a located PLUG gation upward or downward, but they broadside to the are commonly termed nondirectional.' array intercepts Fig. I -This array consists of four dipoles operating in phase. equal power from each of the four di- Photo A shows such a system. This Beam Arrays poles since in this case all currents are particular antenna is erected above the For point-to -point communication in phase, The total gain in the second forty -third story of the building which there are many advantages in using an case is 7 db over that of a single houses WOR's FM station WBAM, antenna which concentrates power in radiator. more than 500 feet above street level desired directions only. Secrecy is main- The narrow fields which are possible in the heart of New York City. It has tained and very high efficiency is pos- with the broadside array are shown in an effective gain of 60! sible. Interference with and from other Figs. 2 -a and 2 -b. The first is a cross - This array is beamed toward Wash- transmissions is reduced to a minimum. sectional view as it might be seen by ington, D. C., and can be used for trans- Sharp beams become practical at the an observer standing on a level with mitting at 47.1 or 106.5 mc. The inter- higher frequencies because the radia- the array (if radio waves were visible). esting antenna is of the same type as ting systems can be constructed within Little power is lost through upward (Continued on page 55) a reasonable area. The Amphenol broadside array is an example of a well- designed communications antenna for the 152 -162 mc band. These frequencies are assigned to fire departments, police, press, and railroads. The same array also can be used (with slightly lower efficiency) in the neighboring amateur and government bands which extend from 144 -198 mc. Its excellent directional characteristics recommend it for fixed or mobile point - to -point service. The electrical design of the Amphenol broadside array is illustrated in Fig. 1. Four half -wave dipoles are spaced by one -half wavelength and fed at their centers. The feeder system from the array may use RG8U or (for very long lines) RG17U co-axial cable. The large- diameter tubing lowers the inductance and raises the capacitance of each dipole. The low. Q broadens the response curve and accounts for the very wide band over which the antenna is effective. Use of low- impedance cable eliminates difficulty with voltage loops and leakage. Note that the outer dipoles are fed through cables which are one full wavelength longer than the cables which feed the inner ones. Therefore each is dipole fed in phase. Photo A- Example of a complex FM array, the antenne of WOR's station in New York City.

RADIO -CRAFT for FEBRUARY, 1947 33

www.americanradiohistory.com NATIONAL UNION "PRESENTATION" RADIO MODEL G -619 CIRCUIT: A.c. -d.c. Superheterodyne - Tuned r.f. stage- a.v.c. TUBE COMPLEMENT: I I2SK7GT r.f. amp. TUNING: Broadcast Band I I2SA7GT Converter I 12SK7GT i.f. amp. POWER SUPPLY: I 12SQ7GT Dot- -105 -125 volts, 60 cycles a.c. -105- a.v.c. -a.f. 125 volts, direct current-Approx. 30 135L6GT Power output

watts consumption 1 35Z5GT Rectifier

PRELIMINARY. ANTENNA: (a) Adjust the DIAL POINTER along the dial cord to the position opposite the first right -hand punch murk on the dial backing -plate, with the tuning condenser gang completely out of mesh Self- contained loop- Coupling for (Minimum Capacity); (b) Set VOLUME CONTROL to the FULL ON position; (c) Main. external antenna. tain SIGNAL GENERATOR output at MINIMUM consistent with a readable Output Meter indication; (d) OUTPUT METER across voice coi ; (e) Follow sequence indicated below. CABINET: Approximate SIGNAL SIGNAL Dimensions - DUMMY DIAL ADJUST SEQUENCE GENERATOR GENERATOR NOTES Height inches ANTENNA SETTING CONNECTIONS SETTING TRIMMERS -I3 Width -83/4 inches .01 mid. At HIGH fre- High side to sta- 455 K.C. Tie Adjust Trimmen quency end of tor lug of C2 -A Tib for MAX. output Depth ---61/2 inches cale. (Min. (Fig. I). Low Tla reading Capacity) side to 8- TIb (Fig. 1)

3 turn coil of :IR Pointer et rot- Across Dummy 1700 K.C. Tb Adjust Trimmer SERVICE NOTES or :20 insulated freme RIGHT Antenna (Flo. I) for MAX. output wire on 7" or R" HAND END of reading HUM MODULATION: 2 d i e t dial scale (Min. OSC. LOOSELY Capacity) Point. On Early Production runs Con- Coupled to loop or will be In line Antenna in Re- with FlRSTpunch denser C -18 consisted of two - ceiver mark at right .05 ).tf units. One ground terminal was connected to CHASSIS, the Same as in 2 Pointer In Tine Sarno as In 2 1520 K.C. Ta Adjust Trimmer 3 above with punch mark above ( Fig. 1) for MAX. output other to B-. Disconnect the R.F. SECOND from reading terminal the .05 Con- right CHASSIS of denser now connected to Pin No. as In 2 At LOW fra Same as In 2 530 K.C. None S40 K.C. signal Same I of the I 2SA7GT tube and con- above quency end of above should be picked scale (Max. Ca- up at or near this nect this lead to Pin No. 5 of 4 pacity) dial setting. either of the I2SK7GTs or to any Check operation This In Seq. 2 If sig- other convenient B- point. nal Is not picked effectively by- passes the a.c. mod- up ulation hum to B- instead of to chassis. REINSTALLING CHASSIS (AFTER ALIGNMENT): - (a) With chassis still on the bench, set dial pointer at the min mum capacity end of travel. OSCILLATION: (b) Slide chassis into cabinet and adjust its position so that the dial pointer is opposite and Remove one side of Resistor R -2 in line with the FIRST calibration mark at the right -hand end of the GLASS DIAL 5 (in grid circuit of I2SA7GT) now SCALE. (c) Tighten the chassis hold down screws. connected to a.v.c. bus and recon- (d) Tuning should now track. so that peak signal is attained at the proper frequency nect to cathode No. 5 Din) of i.f. calibration on the glass dial scale. -I 2SK7GT. 12SK7- GT 12SA7-GT I2SK7- GT I2SQ7-GT 35L6-GT 3.3K 1.0001 EXT. ANT. o 2ND I. 4 .01 1 4 .1. LOOP _ 8

I T28 T2A TOK 41 2W. 47 .0001 + green red + Fe r 50 501 IT 150V. TI 22MEG .005 V.C. L black BLOCK A.V.C. 500K 400V. - 12H 15

B+ I W.

10K 3.9 MEG CIB

220K .2í400V. SW. ON V.C. N°47 R.F. b.f. Iso 12S07 I2SA7 I2SK7 12SK7 35L6 3525 `} ONLY ON MODELS t. ^ _ USING N °51 PILOT 1.400V. I17V.ACDC 1827272127732 e. NOTES: -*2.05'5 IN PARALLEL ON SOME MODELS. RESISTORS 112W. AND CAPACITORS 200V. UNLESS OTHERWISE NOTED. CAPACITORS NOTED IN Jrf.

34 RADIO -CRAFT for FEBRUARY, 1947

www.americanradiohistory.com TRANSATLANTIC NEWS From our European Correspondent, Major Ralph Hallows

that the war began for us in 1939.) will sign on for a small weekly subscrip- Nevertheless, some firms have man- tion a "piped" programme service, guar- aged to produce real novelties- novel- anteed free from fading and interfer- ties of genuine value, and not mere ence. The subscription is about 35 cents flat- catching stunts. One of these is the a week. In return the relay company Murphy A104 receiver, the design of runs wires to the subscriber's house, which strikes out in an entirely new supplies him with a small amplifier and line. The basic idea? To get rid of the a loudspeaker and gives him a choice of HERE "boxiness" and "boominess" which are two programmes at all times. has almost inevitable of making A week or two ago an entirely new been no the results small a smallish cabinet act as the baffle for type of relay system was inaugurated at amount of disappoint- the loudspeaker. Every reader of Rugby. In this carrier -frequency meth- ment RAnio -CaAn knows that if a flat baffle ods are used and the subscriber has the that the is used better reproduction is obtainable choice of any one of six available pro- post - war radios loudspeaker in grammes, though only one pair of wires so than with the coopetup far offered for Much of thudding base runs to his house. The receiving equip- sale here have failed to show the won- a cabinet. the we know well is to cabinet ment consists of a 3 -tube unit, provided derful improvements which the ordi- too due nary man and woman had resonances. The trouble is to know how with a selector switch and a volume been led to a for a flat control. It is planned to extend the car- expect. Having read a thousand times to find convenient place that spectacular baffle. rier- frequency system to other localities advances in radio in the near technique were made during the In this Murphy set the problem is future. war, ingeniously so hang- they can't detect any evidence of their solved by, to speak, ing receiver on to 24 by 18 -inch Popularity Meter application in the new radios in the the a baffle. The illustration shows how this is Incidentally, the relay services supply shops. Most of these look (and sound) an infallible method of determining not to them very much like the same done. The receiver itself is long and old narrow with almost a straight -line lay- only whether a particular programme pre-war works in very much the same item is liked or not, but also just how old boxes! And I am sorry to have to out from antenna to output terminals. In use it should stand on a hard surface, much it is liked or disliked. The engi- confess that the impressions formed by neers at each main relay station have Mr. and Mrs. Broadcast Listener are which becomes an extension of the baffle. meters in the output circuits of their too often not very far from the truth! equipment and they can tell instantly, We are woefully short of raw materials This is something more than just an idea. It really works. The reproduction by glancing at the loads registered on -insulated wire, stampings for trans- their dials, what proportion of the sub- former cores and metal for loudspeaker is so much better than that obtainable with box -type cabinets that readers may scribers are listening at any moment, magnets in particular. This, combined for the load is naturally heavy when with labor shortages, has led manufac- care to try out designs of their own on the same lines. there are many and light when there turers to concentrate mainly on the are few. Some of the most interesting small superhet receiver, containing four or five tubes in addition to the main Far -East Transmissions rectifier. Short -wave fans may have been Now there are not many changes that puzzled over the location of a station you can ring on such combinations of broadcasting in English on 7.185 mc., tubes. Nor can you introduce much in and announcing itself as Radio SEAC. the way of frills when component manu- This is the British Army 100-kw trans- facturers quote delays of anything from mitter in Ceylon, which sends out daily twelve to thirty -six months for the de- entertainment programmes from 1330 livery of any but the most ordinary of EST. These programmes are broadcast simultaneously by a 15 -kw transmitter on 15.12 mc. Carrier- Current Broadcasting In England a large and prosperous system of relaying broadcast programmes was in being before the war and it is now growing vigorously. To L . understand why it is popular you must Side- pieces hold the baffle clear 'of the wall. realize that in all Britain there are only hours that I have ever spent were at 16 broadcasting stations, all run by the such a relay station, watching the dials BBC. These transmit between them two of the output load meters and observing programmes, the regional and the na- their continuous record of listeners' re- tional. In most places both programmes actions to the various programme items. are receivable with good strength and quality. But there are places where re- Anti- fading Antenna ception is none too good; it may be that A novel type of anti -fading vertical the field strength is insufficient, or it radiator has just been brought into use may be that man -made static spoils by the BBC in connection with one of A front view of the baffle -mounted radio set. things. the 100 -kw transmitters at Brookman's Here is how relaying has been worked Park, near London. The 500 -foot lattice small parts. Those are some of the chief hitherto. A corporation, having obtained mast is divided into two sections by reasons why the majority of our pres- the necessary authorization, sets up a means of three low- capacity insulators, ent -day radios differ so little from the large receiving station at an interfer- each 3 feet high and 9 inches in diam- receivers of seven years ago (remember ence -free spot and offers to any who (Continaed on page 63)

RADIO -CRAFT for FEBRUARY I 9 4 7 35

www.americanradiohistory.com Conducted by A. C. SHANEY

SOUND ENGINEERING No. 27

My amplifier is of the conventional This department is conducted for the benefit of all RADIO -CRAFT readers. design consisting of a 67, 56, and two All design, engineering, or theoretical questions of general interest on PA 2A3's in push -pull. I would appreciate installation, sound equipment, and audio amplifier design will be answered it very much if you could give me some in this section. No circuit diagrams can be supplied by mail, all answers idea on how to construct this unit.- being printed in order of their receipt. WALTER G. BRADY, Turtle Creek, Pa. (Note: when questions refer to circuit diagrams published in past issues of technical literature, the original, or a copy of the circuit should be supplied in order to facilitate reply.) The Answer: A vibrating pulsation produced on a Hawaiian guitar actually is a variable - RECORDING AMPLIFIER a.c. power line. This circuit has been pitch tremolo which is produced either The Question: successfully used on a number of com- on the flat or sharp side, depending I am desirous of building first -rate re- mercial recording amplifiers. upon the direction the player vibrates cording equipment. I have been search- A specific circuit for the cristal re- his finger. This type of effect cannot be ing for a suitable diagram for some time cording head has not been given as easily produced electronically in an and have not been able to find one. I was manufacturers' recommendations should ordinary amplifier which has a fixed - wondering if you could furnish me one be followed for the particular recording frequency signal fed into it. It can be with the following specifications: head employed. Connections to crystal incorporated, however, into a synthetic 1. Crystal recording head to be used. cutters are usually made directly from musical generator by slightly altering 2. Playback (crystal pickup) to be the plate circuit of the push -pull output the frequency of the master oscillator included. stage, through condenser and resistor tube. 3. Usable as a small PA system. networks as recommended by the manu- The volume -changing tremolo (or 4. Volume -level indicator of some facturer. The high -voltage secondary in vibrato) is considered colorless and kind, either meter or a cathode tube, in- the isolation transformer is approxi- monotonous by many musicians. This corporated. mately 125 volts, rated at about 150 effect, however, can more easily be pro- 5. High -fidelity-with inverse feed- mils. duced in an amplifier by simply arrang- back. ing for a rapid and fluctuating change Can you supply me with such a dia- ELECTRONIC TREMOLO in the gain of an amplifier tube. A rough gram? I will greatly appreciate any help The Question: idea of how this can be added to any you can give me. I have built several amplifiers for amplifier, follows: JOHN G. SJOBLOM, electric guitars and sold them, but I Set up a controlled sine -wave low - Anderson, Indiana, want to make an improvement on them. frequency oscillator (which will deter- About a year ago, I saw one that had mine the rate of the'vibrato). The out- The Answer: a feature that I would like to add, but put of the oscillator is then fed into A circuit diagram of the type you as yet I have had no success with it. one of the grids in a variable -mu tube request is given in Fig. 1. You will note This amplifier had something in it so that a vibrating change of gain in that a voltage doubler is used in the that, when you threw a switch, gave a the vibrator tube will produce a vibrat- rectifier supply and a combination iso- solid note a quivering or tremolo effect ing change of level at the output of an lation and filament transformer is used somewhat similar to a vibrating pulsa- amplifier. Fig. 2 is the circuit of an to isolate the circuit from the 117 -volt tion of a Hawaiian guitar. electronic volume- changing tremolo which was set up in our laboratory and SooKHló.xEaOWLRER found to operate exceptionally well. a 25C6-G(2) You will note that the 6SK7 is used ROSE INPUT NI _ as a tremolo variable -mu tube. The 4 .006 6SC7 MIKE V.0 N° 6SC7 6SC7 oscillator was made variable from 3 to 250K 12 cycles (in our experiments) to control the speed of vibrato. If you prefer, this may be a fixed oscillator. The amplitude of the vibrato is de- pendent on the voltage of the oscillator. V.C.N°2 MIKE We found a voltage range from 10 to .006 .05 K IK 65 volts more \\ __MIKE INPUT N °2 than adequate. 500K If you are interested in additional LO FREQ. EQUALIZER PHONO INPUT details on the production of tremolo and 500K 25K 25K vibrato effects in synthetic electronic PHONO musical instruments, get I. E. Remeeff's V.C. (Continued on page 59) 500K D vac. SPKR SOCKET Fig. I -An amplifier designed for recording. Fig. Tremolo unit for mu ice! instrument. DUBBING 65C7 -G FILS 2- IN Z-I AMP. FUSE HUMBUCKERt. IDO _ T + ISO 117Y AC RECORD P YBACK 6SK7 TO AMPLIFIER e 1 p °\ IOOK 10K f 4

oINPUT MEG 500K 81.250 K 1 0 A,B i C PUSHBUTTON tI 10 10K (SINE WAVE INTERLOCKING SW. 41 l COPPER OSC. 25Z6-G (2)- OXIDE RECO 3ru- I2.

36 RADIO -CRAFT for FEBRUARY. 1947

www.americanradiohistory.com Edited by ELMER R. FULLER

STATtl LIST

WE inaugurate in this issue from 0930 to 1245; CKCX on 15.19 what we believe is a new idea megacycles from 0930 to 1200; CKCS in listing station schedules. on 15.32 megacycles from 1205 to 1500; The time will henceforth be CHOL on 11.72 megacycles from 1300 stated in four figures of a twenty -four to 1800; and CKLO on 9.63 megacycles hour clock in Eastern Standard Time. from 1515 to 1800. These are all beamed Thus midnight will be stated either .as to Europe; while the following are 0000 (if a program begins at midnight) directed to the Caribbean area : CKRA or 2400 (if the prograrfi ends at mid- on 11.76 megacycles from 1820 to 1935 night) ; what was formerly 1 am will and CKRZ on 6.06 megacycles from now be 0100 and 2:15 am will be 0215. 1820 to 1935. Noon will be expressed as 1200 and 6 XGOY is being heard on 6.154 mega- pm will be given as 1800. Please remem- cycles from 0630 to 0745 hours EST, ber that these times are EST. We think with very good results. This is a good that you will also like this new system catch for early morning. The Chinese when you have used it a few months, have discontinued use of 9.635 mega- as it will eliminate the possibilities of cycles for the balance of the winter mistaking am for pm and vice versa. It months. A new Ethiopian is now being will be greatly appreciated if you will heard from Addis Ababa on 16.065 give your times this way when sending megacycles from 1330 to 1500 and from in reports to us. 2015 to 2130. Has not been heard here The picture of Eddie Startz, six - yet, nor have we any reports of it being language announcer of "The Happy heard, but we are looking for it. Have Station" was sent us by North Amer- you heard it? ican Philips. We would like more photos New certificates will be out about the of shortwave announcers and stations. time you are reading this, so if you wish You will note several changes since an appointment for the coming year let the last time we published this section us hear from you. Regular observers of the log, as many stations have will automatically be re- appointed, but changed their frequencies and sched- we could use reports from several more. ules. The CBC announced the following Send all inquiries to Shortwave Editor, Eddie Start; of Huizen, key basic schedule for the balance of the Netherland sta- RADIO-CRAFT, 25 West Broadway, tion, world -famous international announcer. c/o winter; CKNC on 17.82 megacycles New York City 7.

Freq. Station Location and Schedalo Freq. Station Location and Schedule Freq. Station Location and Schedule

2.500 WWV WASHINGTON, D. C.; U. S. Bureau 4.880 HJFH ARMENIA, COLOMBIA; 0600 to 2200 6.020 XEUW VERA CRUZ, MEXICO: 0700 to 0100. of Standard. 1900 to 0900. 4.890 HIGH BOGOTA, COLOMBIA: 1800 to 2200. 6.020 FZI BRAZZAVILLE, EQUA- 3.310 YVIRO TRUJILLO, VENEZUELA; 1700 to 4.920 CR7B0 LOURENCO MARQUES. MOZAMBI- TORIAL AFRICA; 1600 to 4; 2130. QUE: 1330 to 1500: Sundays. 1000 0000 to 0130. 3.340 VUD3 DELHI, INDIA; 1200 to 1245. to 1400. 6.020 PC1 HUTZEN, NETHERLANDS; 140D to 3.370 YVIRT MARACAIBO. VENEZUELA; 1730 to 4.920 YV5RN CARACAS. VENEZULA: 0600 to 1430: 1745 to 1815: 2000 to 2200. 2230. 2230. 6.030 MOSCOW, U.S.S.R.: schedule un 3.380 YV5RY CARACAS. VENEZUELA: 0930 to 4.920 HIAP CARTAGENA. COLOMBIA: 0600 to known. 2230. 1300: 1700 to 2200. 6.030 CFYP CALGARY, CANADA: 0730 to 0100. 3.390 YV4RK MARACAY. VENEZUELA; 1800 to 4.940 HJCW BOGOTA. COLOMBIA: 0645 to 1115: 6.030 HP5B PANAMA CITY. PANAMA; 1800 to 2230. 1600 to 2315. 2300. 3.390 COLOMBO. CEYLON: 0000 to 1200. 4.950 VQ7L0 NAIROBI, KENYA: 1100 to 1400. 6.040 ALGIERS, ALGERIA; 1230 to 1800. 3.400 YVSRW CARACAS. VENEZUELA: 0530 to 4.950 HJCQ BOGOTA. COLOMBIA: 1000 to 1400; 6.040 RANGOON. 0030 to 0230; 2230. 1700 to 2300. . BUBMA: t 30 3.420 YV2RC MERIDA, VENEZUELA; 1800 to 4.960 HJAE CARTAGENA, COLOMBIA: 1000 to 6.040 COBF HAVANA, CUBA: 0800 to 2300. 2130. 2230. 6.040 XETW TAMPICO. MEXICO; 0795 to 0095. 3.440 YVIRU MARACAIBO. VENEZUELA: 1900 to 4.990 YV3RN BARQUISIMETO. VENEZUELA; 1630 6.060 TETUAN. SPANISH MOROCCO: 0230 2130. to 2230. to 0300; 1330 to 1830. 3.460 YV4RP VALENCIA, VENEZUELA; 1730 to 5.000 WWV WASHINGTON. D. C.; U. S. Bureau 8.070 GRR LONDON, ENGLAND; 2300 to 0030. 2190. of Standards: frequency, timo and 6.070 CFRX TORONTO, CANADA: 0000 to 2345. 3.480 YV4RQ PUERTA CABALLO. VENEZUELA: musical pitch; continuously day and 8.070 BERLIN. GERMANY: 0000 to 0345. 1700 to 2130. night. 6.07D COLOMBO. CEYLON: 1930 to 0545: 3.490 YV3RS BARQUISIMETO. VENEZUELA: 1630 5.300 DTYC MUNICH. GERMANY: 0900 to 0930. 0715 to 1200. to 1230. 5.530 OAXIB PUIRA, PERU: 1800 to 2330. 6.080 WLWK CINCINNATI. OHIO: 1830 to 0100. 3.500 YV5RX CARACAS, VENEZUELA; 0930 to 5.810 MOSCOW, U.S.S.R.: schedato un- 6.080 CKFX VANCOUVER, CANADA; 0930 to 1400. 1530 to 2230. known. 0300. 3.150 YV6RC BARQUISIMETO, VENEZUELA: 1800 5.840 PZH5 PARAMARIBO. SURINAM: 1800 to 6.090 LRYI BU 4NOS,, AIRES, to 2130. 2045. 05 to 07 to RGENTINA; 3.530 YV5RS CARACAS. VENEZUELA: 0530 to 5.870 HRN TAGUCIGALPA, HONDURAS: 0800 6.090 LUXEMBOURG; 1430 to 1700. 2230. to 1000: 1300 to 1500: 1800 to 2300. 6.090 CREW. MONTREAL. CANADA; 0730 to 1945: 3.910 ZQP LUSAKA, SOUTHERN RHODESIA: 5.880 ZRK CAPETOWN, SOUTH AFRICA; 2345 2000 to 2400. 2230 to 1300. to 0130; 1030 to 1600. 6.090 ZYB7 SAO PAULO. BRAZIL: 1600 to 1950. 3.930 HC5EH CIUDAD CUENCA. ECUADOR; 1800 5.890 MOSCOW. U.S.S.R.: 0800 to 1645. 6.100 VUO 10 DELHI, INDIA; 0830 to 0915; 2039 to 2230. 5.890 OAX4Z LIMA, PERU: 1630 to 2330. to 2200. 4.040 PONTA DEL CADA. AZORES: 1700 5.910 OZX4V LIMA. PERU; 1800 to 2400. 6.100 WARSAW. POLAND: 1330 to 2100. to 1900. 5.950 HH2S PORT -AU- PRINCE. -HAITI; 0000 to 6.100 PRE9 FORTALEZA. BRAZIL: 1530 to 2100. 4.100 HCIB QUITO ECUADOR; 1800 to 2230. 0815; 1100 to 1300: 1730 to 2130. 6.110 GSL LONDON, ENGLAND: 1500 to 1745: 4.750 TV RV MARACAIBO. VENEZUELA: 0530 to 5.960 RVI9 MOSCOW, U.S.S.R.: 1700 to 2000. 1900 to 0030. 2130. 5.970 HVJ VATICAN CITY: 0900 to 0930: 1000 6.120 HP5H PANAMA CITY. PANAMA; 0700 to 4.770 YVIRY CORO. VENEZUELA: 1600 to 2130. to 1100: 1300 to 1830. 2300. 4.780 SINGAPORE, MALAYA; 1730 to 5.970 VONH ST. JOHNS. NEWFOUNDLAND; 0900 6.130 XEUZ MEXICO CITY, MEXICO; 1500 to 2230 2330 to 0130. to 1400: 1500 to 2200. 0030. 4.780 YV4R0 VALENCIA. VENEZUELA: 1630 to 5.980 LRSI BUENOS AIRES. ARGENTINA; 1800 6.130 CHNX HALIFAX. NOVA SCOTIA: 0700 to 2130. to 2300. 2300. 4.780 HJAB BARRANQUILLA. COLOMBIA: 1700 5.980 ANDORRA: 0500 to 1900. 6.130 COCD HAVANA. CUBA: 0700 to 2400. to 2255. 5.990 FG8AH POINTE -A- PITRE, GUADELOUPE; 6.140 HIDE MEDELLIN, COLOMBIA; 1100 to 4.790 BANDO ENG. NETHERLA ND IN- 1700 to 1800. 2300. DIES; 0730 to 0900. 6.000 ZFV GEORGETOWN, BRITISH GUIANA; 6.150 GRW LONDON. ENGLAND: 1445 to 1500: 1900 to 2215: 2.130 2345. 4.810 YVIRL MARACAIBO. VENEZUELA: 0590 to 0545 to 0745; 0915 to 1145; 1415 to to 2230. 1945. 6.150 CKRO WINNIPEG CANADA: 2200 to 0300. 6.000 BELGRADE. YUGOSLAVIA: 1130 to 4.810 HJBB CUCUTA. COLOMBIA: 1700 to 2200. CFCX MONTREAL. CANADA: 0700 to 2115. 6.150 6.000 HP5K COLON, 1800 4.820 XEJG GUADALAJARA, MEXICO; 2200 to PANAMA; 0700 to 1300: 2400. 1900 to 2300. 6.150 EQB TEHERAN, 1000 to 1415: 4.820 H1ED 6.010 ZRH JOHANNESBURG. SOUTH AFRICA: IRAN; CALI, COLOMBIA; 1900 to 2300. 6.150 TIRH SAN JOSE. COSTA RICA; 2130 to 4.830 YV2RN SAN 2345 to 0130: 0900 to 1100. CHRISTORAL, VENEZUELA: 6.010 C1CX SYDNEY. NOVA SCOTIA: 0530 to 2400. 1100 to 2130. 2200. 6.150 CSWD LISBON. PORTUGAL: 1430 to 1900. 4.860 PRCS BELEM, BRAZIL; 0600 to 1100; 1530 6.020 H1CX BOGOTA, COLOMBIA; 0700 to 0800; 6.160 HICO BOGOTA, COLOMBIA: 0700 to 0800. to 2000. 1900 to 2315. (Continued on page 64)

RADIO -CRAFT for FEBRUARY, 1947 37

www.americanradiohistory.com \ \ \ `\ . , N.\.\.

RECEIVER antenna may be used by connecting the slo 8 +250« NOVEL ILE OR LE AMP. This is a sensitive superregenerative signal generator to pin No. 1 and the receiver. It uses the new 6AK5 high - set antenna to pin No. 2. 211/450V. frequency pentode and standard plug -in RALPH J. WALSH, coils. The a.f. amplifier is a 6K6. A small Altadena, Calif. 6J5, power supply using a 6X5 supplies 200 6C5, ETC. volts for the plates of the tubes. If the TONE CONTROL .!-2MEG /41, I a IN34 OK voltage on the plate of the 6AK5 exceeds constructed an amplifier using Nvc .01 -.1 180 volts, a resistor should be insert- tone -control circuit' similar to that AUDIO OUTPUT_ ed between the B -plus lead and the 500 - shown in Fig. 2, page 763, of the Au- henry choke to drop the voltage to the gust issue, and found that there was in- OOK value Fig. 1). teraction between the controls and mo- FPTEfi C ±1TO3V. desired (See t T The power supply should be turned torboating when the bass control was a.v.c. The bias voltage may be obtained off changing coils to avoid the risk from batteries, bias cells or a tap on of receiving a shock and to prevent the bleeder resistor. operating the detector without plate H. M. HARVEY, voltage. Scotch Plains, N. J. JOHN JUSTIN, Cicero, Ill. COMPACT INTERCOM Here is a circuit of a compact instant- PHONO AMPLIFIER heating intercommunicator. A IN5 -G Here is a. phono amplifier that has drives a 3Q5 -GT power amplifier. given good service for over a year. It Small PM speakers are used at the uses push -pull throughout and has a master and- remote stations where they very low hum level. Inverse feed -back advanced beyond the mid -point. By serve either as speakers or microphones. tends to flatten the response curve. An changing the circuit to that shown here, Talk -listening switching is done with a Astatic HP 16 pickup, with an output I have improved the bass response and d.p.d.t. lever switch. of 0.85 volt, is used to drive the voltage stopped interaction and motorboating. The power supply uses a Federal amplifier stage. A 12 -inch PM speaker, JOHN KWIErINs1AS, selenium rectifier to supply high voltage housed in a bass -reflex cabinet, is used Duquesne, Penna. for the plates and screen grids and 4.5 with the amplifier (See Fig. 2). volts for the series -connected filaments. FLOYD R. HARRIS, The speaker voice coils are matched Denver, Colo. DUPLEX DETECTOR Here is a circuit that I use on my re- to the IN5 -G grid with a voice- coil-to- ceiver to permit me to use either a diode grid transformer designed for use in UNIVERSAL ANTENNA intercom units. An 8,000-ohm output This circuit contains practically all of or infinite -impedance detector at will. A s.p.d.t. switch connects the plate transformer matches the plate of the the condensers and resistors that may 3Q5 -GT to the voice coils. If it is not be specified by set manufacturers, as of the detector to B -plus or to the cathode, depending on the circuit in use. necessary for the remote station to dummy antennas for aligning their re- initiate a call, the unit may be turned ceivers. The components are mounted in As a diode detector, the 20,000- and 100,000 -ohm resistors form off until the master makes a call. a 2 x 6 x 1% -inch metal box which pro- the load resistor with the audio output taken off at F. C. HOFFMAN, W9VVU, vides sturdy connections and adequate Appleton, Wis. shielding against radiation. the junction of the resistors. As triode infinite - impedance REMOTE SPKR detec- MASTER SPKR ° j b tor, a.f. voltage is taken 20MII off of the cathode load re- I- TALKt----*LISTEN A00 .0002 .05 400 .00005 sistors. Signal voltage 3Q5 Tov, MICA. is ICC4 * 004 400 MICA PAPER 1N5 It-.01 250: taken from the plate of V.C. TO GRID IMEG In use, the signal generator is con- the i.f. or r.f. amplifier and nected to one side of the desired compo- rectified by a 1N34 crystal nent and the receiver antenna post to diode. This rectified volt- the other. If the manufacturer of the age is applied in series set does not specify the type of dummy with 1 to 3 volts of fixed antenna to be used, the I.R.E. universal bias which provides delayed

II7RAC 30 30 6AK5 T.01/00v TI50V. 150V. l WOK

sREGEN.CONT 6L6

6K6 114

IK 6L6 Fig. I, left-superregenerative shortwever. Fig. 2, right - A push -pull phono amplifier. 8 +250vy

3$ RADIO -CRAFT for FEBRUARY, 1947

www.americanradiohistory.com with a COMPLETE LINE o TEST INSTRUMENTS ié:i:'ét'c'' .....' ...,...... SHIPMENT - IMMEDIATE jobber. If your jobber with your regular radio parts in your Please place your order a list of jobbers our line, kindly write for order to us. does not handle instruments, or send your state who do distribute our The Signal Now you can SEE and HEAR with the new CA -12 SIGNAL TRACER for instant use it Always ready to be- takes less than five seconds TESTER this versatile unit. No The New Model 450 TUBE gin using Model rotary selector maze of special cables -the by newly designed one connecting Speedy operation -assured toggle, or lever actwn CA -12 uses only which replaces the usual No line cord -the CA -12 switch e¢sap. cable. batteries. operates on self- contained SPECIFICATIONS: controls of any eir. No tuning tubes up to 117 volts. tubes. model. Tests all up to 3 Megohms in all used in this shorts and leakages Features: Tests in rectifiers. read directly on the Tests both platee of the signal is linevoltage adjuster. Pentodes,Pentode etc., in COMPARATIVE INTENSITY in the speaker. New type such as diodes. triodes, of the signal is heard controls. Tests individual sections meter -QUALITY connecting cable -no tuning tubes. faulty elements Simple to operate -only one multi -purpose tubes or noise due to probe. Noise-Test -detects microphonic built into the detectordetecto internal connections. Tubee and resistor capacity networkdare and loose meter. -Alni V. speaker. a square rugged high gain amplifier SVz "z6'F "x9 " Uses 4W 60 cycles A.C. Built-in weight 8 pounds-measures on 90 to 125 volts sensitive condenser Completely portable- Probe, test leads, Works -May be used as an extremely comes with Detector EXTRA SERVICE THE MODEL CA-12 with Comes housed Checker. A even twhen self -contained batteries and instructions. two wlladetecttypeeakagesl $3950 cabinet beautiful porratede in minute. PRICE the frequency is one per toneeetchegd frontpanel.iNET TESTER The New Model 600 SET METER TUBE TESTER AND The New Model 670 SUPER A NEW COMBINATION MULTI -METER in ono unit. testing laboratory all VOLT - OHM MILLIAM- A complete Volte. D.C. Volts. D.C. A Combination IN- Test tubes. Reads A.C. REACTANCE, Resistances and Decibels. METER plus CAPACITY - Currents SPECIFICATIONS: MEDESIBEL MEASURE TUBE TESTER by newly designed DUCTANCE and Speedy Ìésw hr a iaured tubes up to I Il Volts. Tests all up to 3 Megohms In Testa shorts and leakages SPECIFICATIONS all elements In all tubes. all tubes. one element against VoltVolts 0/3°0/1 ,500/8.000 hreds ofrany etc.. In multi- VOLTS: 0 to 15/30/17.5/15/75/150/750/1,500/7.500000 Tests bodges andIn triodes, pentodes, A.C. to 15/30/150 sections such as diodes, O to 1 Amperes Individual OOto 1,5/15/150 Ma. In D.C.PCURRENT: ohms/.5 0 to 10 Megoams Testsa voltage Baluster. 0 to 500 /100.000 rolytltt) New type line Volts. RESISTANCE: (Quality test -METER SPECIFICATIONS: /75/150/750/1,500 361Moaolwa MULTI TNCE %1. 500 /3,00otóolte /l5 700 to227.0000 Ohms413.000 Henries O to 1S 60%130 / 300 REACTA 8.000 A C. VOW'S: 1.5/15/150 Ma. 0 to 1.5 Amperes. CE +30 to +58 D.C. CURRENT: 0 to Ohms 0 to20 afegohms. to +1,+1081 o +38. 2, 000 /20.000 /200.000 DECIBELS: -10 8tt RESISTANCE: 0 to equals .000 rugged, D.R. housed perating ininstructET $2840 DFto 8 D.B. +10 +88 $ 6250 st leeads aß5000-- lined.) -10 too+ cabinet complete wit -OhmD.R. Size 5wx7% 5r +30 to +58 The New Model 400

650 MULTI METER The New Model ELECTRONIC VOLTMETER A COMBINATION VACUUM-TUBE PLUS AND I"ND REACTANCE AND pAC1T T.V. CTANCE Aid SIGNAL GENERATOR DECIBEL MEASUREMENTS Specifications: 11 llogoluns In- RANGES: D.C. V.T.V.M. VOI/TS: (At 0 CO 3/15/30/75/150/300/750/ to 36 Megacycles put Resistance) 100 Kilocycles 1500/3000 Volts. 0 W on Fundamentals. \oltel O 3/15/30/75/150/300/750/15°°/ 25 Megacycles to 105 Megacycles D.8%15/8ov75150/300/750/500/3000Ohms Per Volt) to A 3C 0 oI/:S: (At 1,000 on Harmonics. modulated 00 RF obtainable separately or D.C. CURRENT: Ma. 0 to 3/15 Ampores. 0 8/15/80/75/150/800/750 by the Audio Frequency. than to cycles pure sine wave -less RESO Ohms; 0to 1/10/1.000 Meg oss " Audio Modulating Frequency -400 to 1,000/10.000/100.000 (ln iFD200. 2% distortion. (T pad). CAPACITY: 05-8 Attenuation -3 -step ladder type of attenuator o005-.2, with a Buffer Amplifier. REACTANCE: 100-50M (Ohms). .01-5 (Megolsme). a Hartley Excited Oscillator to 5M (Ohsns. $5250 Uses as modulated Buf- 635 as R.F. Oscillator; 6SA7 INDUCTANCE: 110 85i19000. Tubes: and rectifier. and Mixer; 6SL7 as audio oscillator N ET fer and instructions. DECIBELS: +10 to +. +30 to +19. Complete with coaxial cable, leads -30 to +18,

I Dept. RC 227 FULTON ST., NEW YORK 7, N. Y.I

RADIO -CRAFT for FEBRUARY, 1947 39

www.americanradiohistory.com ,.-- . . Q AND' r.MIA SAVE WIRE ANTENNA STATIC SPEAKER MATCHING t#W22SL =W18SH 22 gauge stranded 18 gauge stranded A continuous roar and crackle of I have my home radio wired so that rubber- covered lead - plastic- covered, may be used with a remote loudspeak- in wire cloth covered over- static in an automobile radio may often it 54e hundred ft. all hook -up wire - be traced to a missing discharge knob er. $5 thousand ft. available in orange, from the top of a whip -type antenna. The receiver was equipped with an red, green, blue, .:W2CM yellow or grey Although these knobs often appear in 8 -ohm speaker. I replaced the output 2 conductor shielded 60e hundred ft. gay colors, they are not put on the an- transformer with a multimatch trans- rubber -covered mike $5 thousand ft. cable tenna for a decorative effect. The round former and purchased another 8-ohm Se per ft. dt W2SJ - plastic knob is useful in reducing or speaker for the remote position. $7.50 hundred ft. 2 conductor Si card eliminating corona or static electricity $70 thousand ft. 5e per ft. $4.50 hundred ft. discharges from the body of the car. #W2OSH $40 thousand ft. 20 gauge stranded Small bakelite screw-on battery ter- rubber -covered lac- minals may be filed to a globular shape quer braid overall ±W18RB hook -up wire avail- 18 gouge stranded and soldered to the tip of the antenna. able in yellow, rubber- covered ray- Do not use hard rubber knobs as they green, brown on braid will melt 60e hundred ft. 60e hundred ft. during' the soldering. $5 thousand ft $5 thousand ft. JACK SAMUELS, Olympia, Wash. J Jt W22P StW4C 22 gauge plastic - 4 conductor, each covered wire conductor rubber - 50e hundred ft. covered overall RADIOCRAFT wants original kinks from $4.50 thousand ft. 9e per ft. $8.50 hundred ft. its readers, and will award a one StW22RL $80 thousand ft. year subscription for each one pub- 22 gouge solid rubber- covered lead -In 100 ft. coil 7/26 lished. To he accepted, ideas must be wire tinned antenna wire new and useful. Send your pet short- 45e hundred M. 22e each -CRAFT today! 10 for cut or new idea to RAnlo 54 thousand ft. $2 SPKR N°1 A two -gang cir- wire oll sizes in stock Tinned braiding - SPKR cuit- selector switch ¡¡SffePKR DATA FILE °Z is wired so that VOLUME CONTROLS speaker may ASSORTED SIZE SHAFTS & VALUES Many valuable charts, reference either be used alone by (3/a "- 21/4"), 15c -10 for $1.35 tables and graphs are printed in the various radio magazines and books that connecting it Octal wafers with metal flange the serviceman accumulates during his across the 8 -ohm $ .04 10 for $ .35 When the Acorn Porcelain Sockets career. Much of this material is mis- winding of the transformer. .45 10 for 4.25 laid and forgotten unless there is some switch is in the third position, the 6 ft. A. C. cord and bokelite plug speakers are paralleled across the 4- .19 10 for 1.75 form of index to tell just where to find ohm top. 11 ft. A. C. cord with molded plastic plug it when needed. 8 finger grip .35 10 for 3.25 Such a convenient index may be This arrangement may be used for 6 ft. extension cord with dual by using 3 x 5 -inch cards and any speaker impedances'as long as the table outlet .45 10 for 4.25 compiled are matched when 8 M. extension cord with cataloging all tables and reference data. speaker impedances for 4.75 cube -tap .49 10 Use a different heading for each card, used alone or when paralleled. for example. Abbreviations, Ballast Re- SGT. A. W. ADEY, CONDENSER SPECIALS' sistors, Condenser Codes, etc. On the North Bay, Ontario MICA CONDENSERS, high voltages appropriate cards, list the material by Assortment of 10 for $1.00 of book and page number. ALIGNING RECEIVERS con- title chart, 8 mfd 475 WVDC 4 prong plug -in can JOHNSON, denser $ .45 10 for 4.25 YVON On a large number- of radios, the .25 mfd 600 VDC metal tubular San Francisco, Calif. frequency calibration is marked on a .10 10 for .90 is permanently fastened to the .01 mfd 400 VDC metal tubular dial that .10 10 for .90 VOLUME CONTROL REPAIRS cabinet. This makes it impossible to as- .02 mfd 600 VDC metal tubular certain the dial setting after the chas- .10 10 for .90 When the shaft of p volume control .005 mfd 600 VDC metal tubular is clamped in a vise for cutting or mill - sis has been removed. .05 10 for .45 ing, the slightest pressure to either side 8 mfd 500 WVDC F. P. type .69 10 for 6.50 will cause the shaft to move and wobble 1600KC 16 mfd 500 WVDC F. P. type between the jaws of the vise. To pre- .89 10 for 8.50 vent this annoying condition, try placing 10 -10 mfd 200 VDC- inverted can .39 10 for 3.75 another piece of control shaft in the When the 25 mfd 300 VDC-inverted can opposite side of the vise. jaws I400KC .39 10 for 3.75 are clamped tightly, the shaft may be 30 mfd 450 VDC -inverted can 1.15 10 for 11.00 cut or milled without any trouble. GERALD EVANS, Ola, Ark.

SPECIAL BULLETIN OF VALUES ON DIAL CORDS RADIO PARTS AND EQUIPMENT' The dial drive drum on many radios for Yours Today! Send is made of thin sheet metal that has a tendency to cut the dial cord at the point t where it enters the drum. To remedy A simple and accurate way..to over- this condition and lengthen the life of come this difficulty is to mark the con- the cord, enlarge the hole with a drill denser rotor plates with a grease pen- spa- cil the alignment frequencies before SERVICE CO. OF PENNA., INC. or reamer and insert a piece of at tubing into the hole. removing the chassis. PHILA. 6, PENNA. ghetti 7TH AND ARCH STREETS, WILLIAM A. HOME, OTTO WOOLLEY, (ranches: 5133 Market St. and 3145 N. Broad SI. In Phila. Colorado Springs, Colo. Also In Wilmington, Del., Easton, Pa., Allentown, Pa.. Camden, N.), Petitiodice, N. B., Canada 1947 40 RADIO -CRAFT for FEBRUARY,

www.americanradiohistory.com WHAT SERVICEMAN COULDN'T MAKE MORE MONEY THIS WAY?

The business -like way to make money is to keep plugging ahead at your bench. If your stock is lean and you have to run to the distributor every time you need a volume control, you're frittering away your valuable "bench time" and income. Stock up too high on "special" volume controls and you, may wind up behind an inventory 8 -ball.

HERE'S THE RIGHT ANSWER 9 OUT OF 10 TIMES The sensible solution to your volume control replacements is the IRC Century Line. Over 90% (by OWE OF actual analysis) of all jobs can be taken care of by these TYPE D IRC VOLUME 112 types of volume controls. As a matter of fact, you c don't even need the entire 112; a selection of only 70 Type D IRC Volume Controls and 11 Tap -In Shafts may handle most of your work. So see your IRC Distributor right away and save your bench time, patience, and money with IRC.

THE IRC CENTURY LINE The 112 Volume Controls and 5 Switches That Solve Ovet 90% of Your Replacement Problems.

70 Universal Type D Controls with 7 Dual Controls with Fixed Shafts 11 easily installed Tap -in Shafts. 9 Controls for Specific Service 16 Popular Type Controls with Uses with Fixed Shafts Fixed Shafts 2 Special Controls for Power Re. 8 Clutch Type Controls with quirements with Tap -in Shafts Fixed Shafts S Switches All IRC Volume Controls have the famous IRC permanently bonded Resistance Element, the Five -Finger "Knee Action" Contactor, the Silent Spiral Spring Contactor, and the Steel Coil Spring Thrust Washer. Bring yourself up to date with the. new No. 4 Edition of this amazingly popular and useful manual. Contains detailed replacement information on nearly all models up to 1946. Complete listing of 1941 -42 models ... the ones now coming in for repair. 156 pages. 25c at your IRC Distributor.

INTERNATIONA yryCE COMPANY Wherever the Circuit says .Í1. ll

401 N. BROAD ST., PHILADELPHIA 8, PA. in Canada: International Resistance Co., Ltd., Toronto, Licensee NOW THE CONVENIENCE OF I1 IRC TAP -IN SHAFTS, -FOR ALMOST EVERY REPLACEMENT NEED.

RADIO -CRAFT for FEBRUARY, 1947 41

www.americanradiohistory.com ,,WaTetàion

To stimulate its radio and television training programs, this famous resident radio and television school is offering men interested in television this unusual opportunity.

IF you are unable to leave home to go to a resident school, N.Y.T.I. of N.J. can supply you with parts to build a television chassis in your own home. You will be supplied with the same instructions and directions with which the school's resident students are equipped, when they reach the stage in their training that calls for television set construction. If you already have a sound radio background, with experience in building radio receivers, you will be surprised to find how much you can learn about television by building this set. N.Y.T.I. of N.J. is one of America's leading resident schools for men seeking dependable, thorough, up -to- the -minute training in the various of radio and television. Instructor demonstrat- fields ing rare Schmitt Op- The schooling offered by N.Y.T.I. of N.J. is particularly useful to tical System, used in big picture, projection type, those who recognize the high -earning possibilities of technical training television receivers. This famous television school's location in the heart of the television industry, in radio and television and are willing to tackle the class and laboratory helps it to get such scarce scientific equipment. work offered, regardless of their previous education. At N.Y.T.I. of N.J. all types of television receiv- -school diplomas are needed for entrance. But N.Y.T.I. of ers are available for student study. No high N.J. requires that a student be earnest, sincere, and radio -minded. Stu- dents without proper mathematical backgrounds are taught the radio and

You can build a direct viewing television chassis similar to the school, located square in the HEART of America's television one pictured above, either in your own home or in the magni- manufacturing and broadcasting industry. Mail the coupon at ficently equipped shops and laboratories of this famous television the right to get full details.

42 RADIO -CRAFT for FEBRUARY, 1947

www.americanradiohistory.com Seakifkkatarftiome/

Instructor demonstrating theory of light in cornection with study of television mathematics they need. Several students with optical systems used in projection only grammar school educations have successfully com- type television receivers. This is just another one of the pieces of pleted advanced technical television courses. equipment which the New York A -state Technical Institute of N.J. bas considerable number of out -of students attend available for resident student the school because of its excellent, practical type of radio instruction. and television courses, so difficult to get anywhere else in the world today. Living quarters are obtainable by single students.

You Put Into Practice Everything You Learn Students at N.Y.T.I. of N.J. particularly like the way the school puts into practice what it teaches. You may actually build a 17 -cube television chassis. You also help build as many as 7 radio receivers of different types, a total of 75 electronic educational devices. Class study, and laboratory study, in the proper combination, increase interest -and your hands get as smart as your head. A 17 -tube, experimental, television chassis may be built by all resident students of television, and may be kept as their own property, they choose. Big picture television if so (16" x 211/4 ") in the flesh at N.Y.T.I. of N.J. Located in the Heart of the Electronic Industry When it comes to television receivers, N.Y. - T.1. of N.J. has it! All The New York Technical Institute of New Jersey is in types of television re- Newark, N. J., just across the river from New York City ceivers are available for student use and instruc- (only 20 minutes from Broadway by subway or train). tion at the school. The school is located in the heart of America's great radio and electronics industry. Such leading television, radio and electronics manufacturers as R.C.A.,Western Electric, Du Mont, Federal and Edison are nearby. This means that the school offers numerous advantages, as it is in touch with the most recent developments in radio and television. Highly qualified television and radio instructors are here in abundance. Equipment is easier to get. Television students are offered exceptional advantages in this great electronic center.

MAIL THE COUPON TO GET FULL INFORMATION ... FREE Standard laboratory type test pattern used for determining picture perfection in all types of television transmitters and receivers. (You can see it at N.Y.T.I. of N.J.) The school issues a special Bulletin which illustrates 7 and describes its truly exceptional facilities and equip- New York Technical Institute of New Jersey, Dept. 42 158 Market Street, Newark, ment. This Bulletin also describes classes that may be New Jersey Check here if you wish to receive the Special FREE Bulletin describ- attended, housing conditions, costs, hours, etc. If you are ing the resident school of the New York Technical Institute of New Jersey located in Newark, N. J.- including its facilities, equipment, courses interested in Television -you will want to read this Bulle- offered, costa, hours. etc. tin. You can have it free, merely by mailing the coupon D Check here if you wish complete information about building a tele- at right. vision chassis in your own home. D Check here if you are a War Veteran. The school will also be happy to send you complete information about the television kits and directions which are now available to you if you desire to build your own Name Age. television chassis at home. Just fill out the coupon at right and mail it NOW to: Address New York Technical Institute of New Jersey, Dept. 42, Zone City (if any) State 158 Market Street, Newark, N.J. I. RADIO -CRAFT for FEBRUARY, 1947 43

www.americanradiohistory.com ?? WHY NOT ?? Why not have the telephone companies devise a telephone that can be used from a distance of two or more feet away? This would make it unnecessary to hold a receiver in your hand. It would enable a woman to chat and do some mending at the same time. ELIZABETH REHM, St. Albans, N. Y. (Your idea has merit and if there is a sufficient demand for such a device the telephone people will provide it. We were interested enough to interview one of the telephone technical officials, who expressed this view too. For the record, loud-speaking telephones are not a novelty. Indeed, Alexander Graham Bell, himself, in the late 70's used a loud- speaking telephone to demonstrate the telephone. There were many other loud- speaking 'phones in the past-but this was before the day of amplifiers. In the above suggestion if you want to talk back this would mean an amplifier device. Then the phone could be laid on the table and a conversation could be held several feet away from the phone. Technically, the idea is quite feasible. Editor)

Why not design a crystal phono pickup nign with universal a transformer to match the most commonly used line impedances? It can serve a dual purpose as it can be so mounted as to provide a coun- BE CONFIDENT WITH terbalance for the tone arm. PFC. JOHN R. SIMPSON, A MICROPHONE BY TURNER Miami, Fla. Whether it's a general purpose unit for voice and music, or a unit Why not have all autos equipped with a for a specialized application you'll always be confident of accurate small 1- or 2 -tube receiver that delivers its output to a relay which could be pickup and faithful reproduction when your microphone is a used to control the speed of the car. Turner. Turner Microphones are proving their superiority in design Signals from small transmitters located and manufacture to new users every day. at busy intersections, schools and railroad crossings, etc. would be used to ac- Illustrated is the Turner Model 33 -a high fidelity all purpose tuate the control relay. microphone that combines high output with smooth response over Jos. P. BROOKS, a wide frequency range. Its matched acoustic design results in crisp, Vallejo, Calif. clear speech reproduction ... music is full and round with tonal qualities faithfully retained. Furnished in a choice of high quality Why not have headphones with a good flexible rubber cord? Cloth covered crystal or rugged dynamic circuits. It is recommended for studio cords kink, fray and short. Rubber cords recording, remote control broadcast, orchestra pickups, paging, dis- wear well, seldom kink and are easily patching and call systems,public address and communications work. cleaned. PAUL WEISENBACH, Cleveland, Ohio MODEL 33X CRYSTAL impedance: High impedance. Response: Flat within t sdb from Crystal: High quality moisture sealed (They were specified in most Army 30.10,000 cycles. crystal. equ ipment. Editor) Output Level: 52db below I volt/ Stand Coupler: Standard W-27 thread. dyne /sq. cm. Cable: 20 ft. removable cable set. Why not have radios with built -in line MODEL 33 DYNAMIC Impedance: 50 ohms /250 ohms /500 filters? This would eliminate the filters ohms /high impedance. Response: Flat within *5db from Magnetic circuit: Heavy duty dynamic that sometimes have to be inserted be- 40-10,000 cycles. cartridge. tween. the outlet and the receiver. Output Level :52db below 1 volt/ Stand Coupler: Standard %' -27 thread. dyne /sq. cm. Cable: 20 ft. removable cable set. TROY BLAND, Gilmer, Texas

Why not offer an efficient preselector THE TURNER COMPANY stage as optional equipment on the bet- 902 17th Street N. E., Cedar Rapids, Iowa ter class of home receivers? DX and Licensed under U.S. Patents of the American Telephone and Telegraph Company, and Western short wave fans should be willing to Electric Company, Incorporated. Crystals licensed under patents of the Brush Development Company. pay a premium for top performance. OTTo WOOLLEY, TURN TO TURNER FOR THE FINEST IN ELECTRONIC EQUIPMENT Colo. Springs, Colo.

44 RADIO -CRAFT for FEBRUARY, 1947

www.americanradiohistory.com vt,,,,,,4 eta Do you want the MOST for your money? Do HERE'S HOW IT WORKS: (1) Each month you you insist on getting GOOD radio parts? Then will get a list of Olson Radio Bargains, with the Olson Gift -of- the -Month Club is your dish! a coupon good for the Gift -of- the -Month. (2) Enclose the gift coupon with your order HERE'S HOW YOU JOIN: Just fill out the for a low minimum or more, and we will Application below, mail it, and you're a send you the gift FREE. (3) No obligation. You member. NO DUES - WE PAY THE GIFT -BILL! can order or not, os you please, any time. Paste This Application on a Postcard and 'Mail Today!

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THE PROBE -TRACER THE description of the Dynamic Hang for introduction into the chassis under be detected at the aerial coil with the ful Signal Tracer in RADIO -CRAFT, test, and two leads, one going to head- tracer volume control well advanced. November 1945, interested me greatly. phones. The probe may be applied to Batteries are used because of the sim- You might like to know about a less r.f., i.f. or audio circuits. The tracer plicity and cheapness of the method. The elaborate one which I devised early in can be used to listen to the signal at any batteries are wired to a tube socket 1945 and have used successfully ever point. Distortion, hum or noise can be and the cable from the tracer term- since. Due to lack of radio servicemen in traced to the stage at which it first inates in a plug which is pushed in the Australia, the authorities licensed a occurs. The tracer will indicate filtering socket when required. No switch is then number of experienced amateur radio hum, at the output of the filter if that needed. constructors and others to carry out unit is defective. If screen and cathode From my conversations with many radio servicing on a part -time basis. As by- passes are effective, no signals or constructors I believe this instrument a holder of a part -time license only, and very weak signals will be found at fills a need. With the addition of a coil, with no intention of taking up servicing cathodes or screen -grids. condenser and aerial it becomes a one - as a permanent occupation, I did not The tracer is so sensitive that it tube radio.- Hubert L. Bailey. want to buy or make too many items need only be 4 ONE SIDE CUT OFF of expensive equipment; and with the brought close to INSULATING COVER - help & TOP END NOTCHED of a good multimeter, an oscillator the grid or plate OUT FOR SNAP -RING and a tube tester, this simple Signal lead of any high PROBE TUBE SOCKET Tracer carried out all my servicing. level stage. Oscilla- TUBE TUBE SOCKET Amateur constructors who have made tion of the mixer INSULATING LE TYPE COVER HOLE FOR V.C. two or three receivers or amplifiers tube is readily de- VIEW WITH BOTTOM SHIELD REAhWED usually have sufficient practical knowl- termined, as a sig- 1 GROUND PROBE CARRIER OMMON edge to service their own sets and those nal is VOL.CONT. obtained ATTACHED WITH of their friends. The most common from SOLDER the oscilla- TUBE SHIELD methods used are voltage measurements, tor grid or plate, TUBE BASE--"' with ID8 -GT condenser and headphones. which differs from r------AI The device shown in the sketch should the output signal 250 ALUMINUM CASE MICA FROM appeal to many constructors because of by the intermedi- 0001 I.F. CAN -.5MEG PHONE. JACKS its simplicity, low cost and effectiveness. ate frequency Ht > The instrument is easy to build, and the (that is if a broad- C-4.5V. ALUMINUM STRIP HELD diagrams will 2MEG ON EACH SIDE give a fair idea of the cast of sufficient .002 WITH SELF-THREAD- B+45V. REMOVABLE compact form, though each constructor strength, A- B- C+ COVER ING SCREWS at the os- 1 LEA' will probably design a shape to suit the cillator frequency, TUBE SHIELD LSV PHONES .NO materials available. ALLIGATOR CLIP ATTACHES TO CHASSIS UNDER TEST is receivable by the BATTERY LEADS It is a hand -held tool having a probe set). Signals may

RADIO -CRAFT for FEBRUARY, 1947 45

www.americanradiohistory.com RADIO -FREQUENCY LAMP Since the beginning of the century, ultra -violet rays have been applied in CONCORD many widely diversified industries and occupations ranging from crime detection and interior decoration to physio- Bargain Catalog of therapy and germicidal purposes. Common man -made sources of these rays are carbon -arc and mercury -vapor lamps. The carbon -arc generator gives off considerable heat and is inconven- RADIO ient because the electrodes constantly wear away and require frequent adjustment of the spacing between their Equipment tips. The mercury lamp has metal FOR electrodes sealed in the ends of a quartz tube containing mercury vapor. An electric current is passed between the elec- Immediate Shipment trodes and the vapor ionized, releasing quantities of ultra -violet rays. The main difficulty with these tubes was the grad- ual breakdown of the electrodes with subsequent reduction in the ultra -violet output. There was no way of determin-

QUARTZ TUBE 1I7L7 -GT -I 250 Mut FIL

TIMING 5W MICA 250uuf y117V.AC/DCQvD 250uuf SPECIAL VALUES Fig. I -Power supply for ultra -violet lamp. HAM GEAR AMPLIFIERS m ing the useful output of the lamps and they were often used long after their useful life had expired. This handicap to users of ultra -violet ray equipment has been overcome by use of a special quartz tube and an r.f. oscillator. This tube has been produced in several sizes and for industrial and therapeutic purposes. The smaller sizes are available as "sun lamps" for the homes. Photo below shows one of the lamps. This lamp uses a quartz tube that has been exhausted to a high vacuum and filled with argon, neon or other Just off the press -48 exciting pages of radio parts, equipment, and inert gas, along with a small globule supplies of mercury. When the tube is placed in for dealers, servicemen, amateurs, maintenance, testing, a strong radio frequency field, some of building and experimenting- Thousands of items NOW IN STOCK and ready for IMMEDIATE SHIPMENT! Big feature sections of Radio Sets, Communication Receivers, Amplifiers, Ham Gear, Record Players and Portables, Record Changers and complete Sound Systems. Page after page of bargains and special values in top- quality standard -make radio and electronic parts. Mail Coupon NOW for FREE COPY Mail coupon below TODAY for your FREE COPY of this latest Concord Buying Guide and Bargain Catalog of Radio and Elec- tronic needs you can order for SAME DAY SHIPMENT from complete stocks in Chicago and Atlanta.

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www.americanradiohistory.com the mercury vaporizes and the tube con- ducts current. The resulting ionization is a source of ultra -violet rays. A simple 1 -tube r.f. generator, shown just below, is used to excite the lamp. It is small enough to be housed in the base, thus eliminating bulky high frequency induction coils and power supplies.

It's Easy If You Follow Our Plan Thousands of new jobs are opening up- FM, TELEVISION, MOBILE COMMUNI- CATION SYSTEMS, are only a few of the new radio fields which require licensed opera- Underchassis view of single I 17Z6 oscillator tors. This generator, Fig. 1, uses a single FREE Tells you the Government require- 117L7GT tube as rectifier and r.f. oscil- BOOKLET ments for all classes of commercial lator. The circuit is a series -fed Hartley operator licenses. Tells where to apply for and take the ex- operating between 16 and 20 mc. The aminations, examining offices, scope of knowledge required, coil consists of 12 turns of No. 18 wire extracts from FCC Rules and Regulations, extracts from FCC Study Guide and Refer- wound to a diameter of % -inch and ence Material, approved way to prepare for FCC examinations, positive method of check- spaced to about 1% inches. The coil is ing your knowledge before taking the examinations. tapped four turns from the grid end. Edition Limited-Mail Coupon Before Supply Is Exhausted The quartz lamp fits into clips connected across the coil with 250 -itµf mica condensers at each end to prevent d.c. CLEVELAND INSTITUTE OF RADIO ELECTRONICS voltage from reaching the lamp. CONTRACTORS TO THE CANADIAN BROADCASTING CORPORATION Successors to 251iaif (2)35L6-GT ;MNW NILSON RADIO SCHOOL SMITH PRACTICAL RADIO INSTITUTE Founded 1939 Founded 1934 35L6-GT RC TOWER, CLEVELAND 13, OHIO l -2 TERMINAL r "G -1 Bill of 45I5-GT Approved for Veteran Training Under Rights" . I I ' M A L T H S COUPON CLEVELAND INSTITUTE OF RADIO ELECTRONICS RC -2 TERMINAL TOWER, Cleveland 13, Ohio Gentlemen: Please send your FREE Booklet, "How To Pass FCC License Examinations." (Note: This Booklet does not cover examinations for Amateur License) NAME I have had experience in broadcast- 45Z5 -GT ing servicing O operating Fig. Push -pul supplies more power output. ADDRESS 2- mfg. CAA Army -Navy O When more r.f. voltage is required, CITY STATE .... amateur other in 2 may be used. In the circuit Fig. Check license desired: this instance, push -pull 35L6's are used I am a High School Grad. College Radiotelephone 3 1st. Class 2nd Class in the same basic circuit with the plate Grad. with degree voltage supplied by a 45Z5 -GT rectifier. Radiotelegraph 1st Class 2nd Clase available r.f. voltage from this cir- The licenses If a War Veteran, check here cuit is twice that produced by any I now hold these single -ended oscillator using the same voltage. The coil in this circuit plate CRYSTALS uses 11 turns of No. 18 bare- tinned cop- REPAIRING CRACKED per wound to a diameter of 7/s -inch and Electrically and mechanically, the to oscillate when mounted in the new - spaced to 11/2 -inch. Taps are connected most fragile component of a radio style (octal -socket) holder which uses 2 turns each side of center. transmitter is its frequency -controlling heavy pressure. When placed in an A small timing switch is built into crystal element. When used to control old -type round Bliley holder, however, the .base of the sun lamps so that the a high -power oscillator, it heats up and it operates almost as well as did the operating time may be pre -set to, pre- eventually may crack. We have some one -inch crystal of which it formed a vent over- exposure to the ultra- violet which have given way after many years part. This Bliley holder has an adjust- rays. of satisfactory operation in numerous able pressure, an important feature for experimental as well as conventional our purpose. Cigarette paper absolutely free of hookups. Maximum output and most stable leaks is made by a process developed by We find that ordinarily a cracked performance is obtained by decreasing General Electric. The paper acts as in- crystal ceases to oseillate. However, a the adjustable pressure against the sulator between two conducting rolls broken crystal whose surface is,other- crystal until the oscillator output is with high voltage between them. An air - wise unmarred can continue to oscil- greatest. Then the pressure is in- hole or piece of foreign matter of lower late if mounted under rather light pres- creased slightly to keep the crystal from resistance than the paper causes a flash- sure. For example, we have one small moving about. It may be necessary to over, which is indicated by an alarm fragment (about '/z by %-inch) of a round off any jagged corners or edges. bell or lamp. 40 -meter crystal which cannot be made -I. Queen RADIO -CRAFT for FEBRUARY, 1947 47

www.americanradiohistory.com TRANSFORMER WINDER

WHEN it comes to a show -down any- Those are purely the mechanical wind- one mechanically inclined can dupli- ing parts, the level wind guide is some- cate almost any gadget or machine from thing else. It permits winding each layer junk parts that clutter up his shop. This on straight and close. As shown in the electric coil winder was built entirely illustration, the operator sits by as the from scrap bits by the radio repairmen coil is being wound. His right hand is on of the 3124th Signal Service Co. when a crank (taken from the same field tele- they were stationed in Ghent, Belgium, phone generator) which he must turn to during the war. It came in handy when achieve the level wind. What he actually burned -out transformers weren't replac- turns is a threaded shaft, a rod that has able and impedance- matching trans- been threaded its entire length. Over formers were needed to balance off- this fits a little threaded slider that color foreign equipment with our own screws on the threaded shaft so that "standard" apparatus. when he turns the crank in one direction In Europe burned -out transformers or the other the slider moves up or down were the biggest problem. Most cities along the shaft. had so many different voltages that it was In the illustration the threaded shaft impossible to use any equipment is the one above, without first knowing the one attached to the heu( 30 WATT Deluxe what commercial crank. The lower shaft, which voltage was used. Antwerp, Belgium, is the same size, merely acts as a guide and PORTABLE was the best example with six: 110 keeps P.A. SYSTEM volts, 220 volts the slider, which is the piece half and 240 volts, on both way between a.c. and three d.c. the two uprights, from People who moved rotating with the upper shaft. from one part of the city to another (sometimes only across the street) had The slider has a small grooved pulley to exchange their electrical appliances attached to it over which the wire runs Here's a preview of ALLIED Sound for for those just before it winds onto the transform- 1947 in this of the new voltage. Some build- smoothly -styled, brilliantly ings had both a.c. and er. Thus by turning the crank at the engineered 30 Watt De Luxe Portable d.c. outlet plugs- System. New stabilized inverse feedback you could never be sure. proper speed and in the proper direc- circuit delivers high output, usable right The electric coil winder helped over tion, the wire moves along the coil sur- up to its peak. Flexible operation is pro- face and level vided the rough spots and cut down the work- wind is achieved with by two microphone and one phono surprising ease. channels, each with separate control. Has ing hours per job tremendously. It was bass -treble tone control. Amplifier and made from odds and ends of military The reason the level wind speakers are safety- fused. Amplifier guide is gain equipment but a civilian shop has com- hand -operated is that too many sizes on microphone is 128 db; on phono, 80 parable of db. Frequency response: 50- 10,000 CPS. junk. The winder was powered wire were used. Had the winder been System covers up to 4,000 persons, or up with an old phonograph motor geared mechanically fed each size would re- to 20,000 square feet. down with gears taken from a burned - quire a new gear system to move the out hand generator from Complete 30 Watt System includes: 30- an army EE -8- wire along at a different speed. Had Watt De Luxe Amplifier with tubes; 2.12" A field telephone. The number of turns hundreds of coils been needed, it could Safused Dynamic Speakers, with 30 -ft. was counted with a Veeder counter from have been cables mechanically operated, but and plugs; 1- Cardax Unidirec- a radio transmitter dial taken from a for the few dozen tional Microphone with floor stand and required it did the 20 -ft. cord and plug. Complete in hand- sunken Liberty ship that went down in work of a factory winder, at a slightly some luggage -type split portable carry- the English Channel. lower speed. ing case, 22 "x20 "x 15 ". Carrying wt., 60 lbs. For 110 volts, 60 cycles A.C. (Less phono top and volume level meter which are optional.) Complete System (approximate price) ()iffy

See your ALLIED Cat. alog No. 1 1 1 for the world's largest and most complete stocks of quality radio and sound equipment -at I today's lowest prices! For Everything Count on ALLIED for Radio and fast service, ex pert h elp. in If you haven't a copy of Catalog No. 111 - Sound send for it now -it's FREE for the asking.

ALLIED RADIO CORP. 833 W. Jackson Blvd., Dapt.,2 -B -7, Chicago 7, III. Ship 30 -Watt Portable System described above. $ enclosed. 13 Send full details on ALLIED Sound. Send FREE Radio Catalog No. 111. Name

Address

City Zone State

48 RADIO -CRAFT for FEBRUARY, 1947'.

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The Question Box is again undertaking to answer a limited s number of questions. Queries will be answered by mail 3 and those of general interest will be printed in the maga- line. A fee of 50c will be charged for simple questions requiring no schematics. Write for estimate on such ques- fions as may require diagrams or considerable research.

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INTRUDER ALARM connections for testing all types of of the May issue. I would like to have Y. a diagram showing how I may use a L" Please print a diagram of a bur- tubes. -L.P., Long Island, N. triodes, in A. Here is a complete diagram of a 0 -200 microampere meter in a vacuum - glar alarm using 0A4 -G gas Newark, a capacity -operated circuit. The capac- tube checker showing the connections tube voltmeter circuit.-J. B., ity antennas are to be placed at the for all commonly used sockets and for N. J. windows and doors of my home to all switches. A. A vacuum -tube voltmeter may be sound an alarm when anyone ap- To test any tube, it is necessary added to the tester. A 6Q7 is used. Plate proaches from the outside. -J.O.H., San that you refer to a tube manual to get the pow- volt- voltage is obtained by tapping Diego, Calif. the socket connections. Filament at on the tester. R2 -11. The tube er positive lead J9 A. Here is a diagram of a capacity - ages are selected by Sw will be 250 is plugged into the socket and filament is adjusted so that there operated alarm drawn to your specifica- the proper volts on the plate of the 6Q7. It may tions. A capacity wire of screen is voltage applied by throwing switches to connect the filament leads be necessary to experiment with the RY-I to busses A and B. If there is a cathode, value of RI to obtain initial calibration. CA, WIRE, SCREEIN,PLATE, it is also connect- SWI 0A4-G 1.5 V. ed to bus B. For 7MEG 607-GT ADJUST TO 250V. b 5V. I CIRCUIT C2 emission tests, all 6 POSITION SW. (R2 2MEG 117 V. AC other elements are connected to bus C. I5V. C3,2¡ ¡ IMEG In full - '700 50K testing 50u Cq wave rectifier tubes and duo -di- 200K 7K 5W. 150% TO ADDITIONAL UNITS odes, each plate is IN TEST Pp ZERO ME 5K ADJ. by 70K RY 2 tested in turn -DI connecting it to 500V 100 placed in to be protected. A 600V the area bus C. 30K 75 B+ grounded metal shield or baffle may be EXT.GND. TO The check iscali- CONNECT LEAD mounted about 6 inches from one side O 8 -TO CHASSIS GOING TO J9 brated by testing r. to reduce sensitivity from one direction. and recording From this point on, the Calibration Ad- These tubes have a photo -electric char- tubes of known quality the dial readings and setting of R2. just control will be used for corrections acteristic and should be shielded from and calibrating in- of the calibration. -1 has been Further operating light. After relay, Ry found on page 35 of is connected so that it may the alarm will ring until Sw2 structions may be The meter tripped, Radio Test Instruments with a zero -center scale so that is opened to reset Ry -2. Home -Made be used on page 25 of the July 1940 issue measurements may be made without Ry -1 is a 5000 -ohm plate relay and and of RADIO -CRAFT. regard to test lead polarity. Ry -2 is a small 6 -volt d.c. relay. SIMPLE TUBE TESTER V.T.V.M. CIRCUIT i. A.C. -D.C. POWER SUPPLY Please print a diagram of a simple I am .planning to build the Multi- Please print a diagram of an a.c: on page 584 r tube tester showing the socket wiring Purpose Tester described d.c. power supply for use with small 4 IliGRID CAP audio amplifiers.- V.P.B., Lyndonville, N. Y. THESE LINES 5o 25Z5/25Z6 MAY BE EXTNOD II 7 V. AC 40'It -f:íarr..// OTHER 450V. SOCKETS iiiiiiiii 3011 8+200V.

10 I50MA 10014A o pVOITS JACKS. IIlV. UP V4- 2W. NEON BUSA 11111113111111

SW ;sWl4 75W '' "16 .LICKS 30V DOWN A. The circuit of a half -wave voltage BUS S.113 doubler is shown. This circuit, using a 25Z6, will supply 200 volts at 9 OB 25Z5 or S : B 6B 7B 80 50MA. 117 V.AC R2 100 ma. The total current drawn by the PILOT 1281 R 6F6 and 6SJ7 will seldom exceed 40 ma, 12 6 1 so the output voltage will be about 240 1I IOB IR 5K volts. BUS IIII V' 50 RADIO -CRAFT for FEBRUARY, 1947

www.americanradiohistory.com RADIO PROGRESS IS SLOW Dial Belt Kits - Phone Needle Packet (Continued from page 17) Ruf -Koat - Dial Cable Racks - Lite -Koat Kit

G-C Ruf -Koat Air Dry -YS!";'`J,.=S G -C Servicemen's experience that it will take many Wrinkle Finish Dial Cable Racks years to develop anew device and , f /IrteerNA Convenient to handle The only wrinkle finish radio dial cables. Hang that in the process all et most of the that will air dry with- rack which has 10" ruler, out baking. Easy to use. easy to measure cable. original capital may be lost if further Gives professional wrinkle ... Spools wind independent capital is not forthcoming. There are finish. No. 60-2 -1/4 pt. of other spook. No. 7-A- 1T. List 45c 25 -rack, ruler 5 -25 ft. many cases on record where initial spools List 1 ®i $5.58 investments of $50,000 grew to over G -C Servicemen's G -C Luminous Lite- a million dollars before the device Phono Needle Packet - Koat Kit "Glows in finally appeared on the market. Dur- For every serviceman to the Dark" carry on calls. Sell needle Long -life, luminous, safe ing that process the original inves- replacements with this coating that emits light handy packet. Contains in the dark. Ideal for of- tors were forced to give up most of ten needles, two each fice, home, etc., many type and two recording uses. No. 184 -0 Deluxe kit their share in the device, if they stylus. No. 1432, List $8.50 -powder, mix-koat, top - were not to lose everything. Often koat, brushes and thin- the first investors did lose everything G -C Servicemen's Dial ner List $2.50 Belt Kits and the original company went into Fine woven fabric replacements bankruptcy. Subsequent investors for all sets. Made of finest material, no stretch, no G -C Ne-O -Lite Tester then stepped in, bought the assets, slipping easy to install. Supplied in kits Handy, inexpensive and financed the project until the of veriousquan- Ne -0- Lite Tester device was finally placed on the mar- tities, with steel that every box. No. G -25- one should ket. Pioneers thus more often than Kit of 25 belts have for List $6.70 countless uses. not lose out only to have others who Can be used are on 60 V.A.C. better capitalized take over and to 500 V.A.C. or D.C. market the invention. All of this is No. 5100- single tester on card List 50c normal evolution I AVAI AT LEADING DISTRIBUTORS. typical not only of WRITE radio, but also of any other endeav- FOR CATALOG TODAY. ors. It is a rare device in which the RADIO DIVISION DEPT. original investor reaps the fruits of his labor. CEMENT Mfg. (o., Rockford, III., U.S.A. GENERAL cities products Sc'loitres in principal The above facts should be kept in Manufacturers of over 3,000 p mind when you wonder why new radio inventions that should have been on the market long ago have not materialized: The Nationally Known HOLLYWOOD BROILER Take just one -the vest pocket miniature radio sets promised now Here's the finest broiler made. It has an easy for several years by some radio to handle cover, an attractive finish, comes manufacturers. Technically we seem complete with to have all the requirements to build rack and cord. It has two heats these receivers. Practically and eco- and is roomy enough for the largest roast. nomically, however, it may take some time before they will be on the mar- 12.95 each. 12.50 in lots III 6 ket. There are still a great many "bugs" to be ironed out. Miniature radio tubes still have to become small- HOT PLATE er and more efficient and sensitive. 3 heat, two element, mounted on attractive metal stand. Different circuits must be evolved. Three Switches Control all Heats. Complete with cord. Miniature variable condensers are yet to be perfected. Moreover, nor- Net:price 6.50 each. Lots DI ten 5.95 each. mal radio set manufacturing processes are not applicable to vest FOR ROOMS... 2 SPECIAL VALUES pocket sets. They cannot be produced FOR STORES . Representative Values From Our Complete Radio like regulation radio receivers simply FOR GARAGE ... Parts Stock. 5' P.M. speaker. Alnico slug ... 3 to 5 ohms because they are too small. Assem- RADIATION TYPE HEATER . voice coil. bling them becomes more or less a This cone shaped heater has replaceable 1.59 each.... . 10 for 14.90 watchmaker's element, and is 100% safe. Comes com- endeavor. New work- Output Transformer. Clinch or Screw Type. plete with guard. ers must be trained for an entirely Can be used with 5014 . . . 351.6 . 251.6. new kind of assembling job which 4.95 each... In lots of six 4.45 49c each. 10 for 4.50 never existed before. There is also a cost in Write us about your needs in Radio Parts, Testing angle connection with this and Sound Equipment, and Electrical Appliances. item, because no one is going to pay $50.00 or more for a vest pocket set. Send for Our Latest Catalog In order to bring the cost down a slow evolutionary process must be gone through. All these problems will RADIO PARTS COMPANY be solved eventually, but it always takes time. 612 W. Randolph, Dept. "C ", Chicago, 6, Illinois RADIO -CRAFT for FEBRUARY, 1947 51

www.americanradiohistory.com SMALL RECORDING STUDIO ewp.. \. (Continued from page 27) up patterns of the most common types. Now that we have an idea of what we need as a,minimum for our studio, let us see how those items are coordi- nated by studying an actual setup which was assembled by the author. After much shopping around, a.two speed 16 -inch Rek-o-Cut model D -16 turntable was purchased. This model comprises a heavy cast -iron turntable, rim driven through heavy rubber idlers by a 1/20 horsepower induction motor. The speed- change knob is conveniently located and easily operated without stopping the turntable. The rumble is very low and there is negligible speed change under cutting load. The turntable assembly was rigidly bolted to the top of a wooden Sears & Roebuck sink cabinet. It is not good practice to float the table in rubber, but rather it is desirable to fasten it solidly hfrriaTirc'S" to a rigid base. The attendant damping is valuable in removing the motor vibration. latest, greatest There were not a great variety of overhead assemblies available, so a second -hand 12 -inch Universal overhead was acquired and modified for 16 -inch AO/OCATiyz06' duty. The modification included turning new longer lead screws for inside -out and outside -in operation, and a long method of overhead offered by support bar. The Ys, here it is at last - the most complete catalog ever drive was changed also. By now a good Lafayette - the world's largest radio supply house. And what a catalog overhead system can be purchased for it is Its pages are brimming with an amazing display, of top- quality $150.00 or less, and at least one is ad- radio and electronic equipment -such items as radio parts, complete sets, vertised for less than $50.00, including build -it- yourself kits, amplifiers, microphones, automatic record changers, cutter. ham gear, test equipment - as well as hundreds of other items. There is usually quite a lineup problem in adapting an overhead to a turn- 144 PAGES - HANDSOMELY ILLUSTRATED table. This problem was simplified by All the tried -and -tested standard equipment is listed -also many items so using a single ball bearing as the rest- on the here the first time. And every- ing place for the overhead turn- recently developed that they're shown for center pin. The overhead is driven Be among table thing is in stock -ready for super-speed delivery- economy priced. by an arm which is contacted by the the first to get your copy of Americd's greatest radio catalog - FREE. drive pin in the turntable. It is impossible for a slight mal- alignment to cause mail coupon below binding and the annoying attendant wow. In the interest of cost, a Brush RC -20 Lafayette crystal cutter was used. It was attached typ1Cal to the carriage by a % -inch stainless e, e.Ratilv steel bracket. There was a tendency to- ,B.Pa/ys ward bouncing of the head, so a visco- loid damper was added, together with RADIO WIRE TELEVISION INC Neary.Dat an eight ounce weight, to lower the 100 SIXTH AVENUE NEW YORK 13, N.Y. ?Be resonant frequency of the carriage. The 110 FEDERAL STREET BOSTON 10, MASS. n volts at photo shows the drive mechanism and 24 CENTRAL AVENUE NEWARK 2, N. 1. and amps T Yolk Fa the finished cutter assembly. 2.5 this low Because we chose a crystal cutter, we this price. d / wf former HR y0 NOW also chose a crystal pickup. A Brush . 314-Filament from Yourar Trans- well pickup. g------LAFAYETTE RADIO, Dept. 1B -7 toss only PL -20 is a very constructed í2.93 Its response is good to beyond 10,000 100 Sixth Avenue. New York 13, N. Y. cycles per second. It is of the low -pres- sapphire type, with a Pleine send FREE C4TALOC air ones toe sure permanent Famous tooth arm. It was sup- Relayr spring counterbalanced 1 7 plied with an equalizer which corrects DPD¡rOmtt7ntulna_ Nome SPD7eonab eporoee for commercial modified constant- veloc- chanpeeYSr, 1°wl oNr/orbreok- ity recordings. i°' unman Address 9oinp r- 60.cycle on hand was mod- ONCE. 1 Iml toilo An amplifier Toes order sear enly0i1.9Sbb ified to provide the necessary character- R1ay..T recording. The modified am- Cityty istics for ------Zone -Slate - - - -- (Continued on page '77) 52 RADIO -CRAFT for FEBRUARY, 1947

www.americanradiohistory.com HAS IT! ITI HIGH SPEED PHOTO FLASH ARRISON HAS (Continued from page 23) HARRISONARRISON

ture bulb is suitable for this applica- For a tion (see Photo D). Incidentally, no Vy 73 to you, OM trouble has occurred through operating Joyous Christmas and a this bulb on 9 volts, since it carries a 6- to 8 -volt rating. A 6 -prong cable car- Productive New Year! ries connections between camera and Bil Harrison, W2AVA power unit. Ordinary 6 -wire speaker

HARRISON SELECT SURPLUS ALL STANDARD LINES we are Factory Authorized Distributors for the Your assurance of good, usable, guaranteed, sur- top Quality manufacturers and we now have in plus material nt sensationally low prices-TOP stock Iota more new, latest, improved VALUE ALWAYS! Como in and browse production Ham gear I Visit our stores today, for everything through our large HSS Department. you need. We promise you 'fresh, clean material -quicker--at the lowest current prices -and COMPACT VIBRATOR PACK above all, our sincere desire to be of friendly, FR for transceivers, portable receivers. etc.) Delivers helpful service. 135 volts at 80 ma: 671 volts at 8 ma: 1.5 filament or As one of the world's largest distributors of G.3 heater. bias. and microphone voltages. Communications Equipment. we are delivering Completely filtered noon tube voltage regulator mote load -start relay-ruggedly- made for dependable- plenty of Nary use. It¡" a 3 %" a 4'. Weighs only 2 168.1 Works on any 6 volt DC source. RECEIVERS Right Howl ALL MAKES - practically all models. Complete vibrator pack. loss only battery (use If you want your new set In the Quickest possible time It on four Naelillght cell., your Car send your order to HARRISON] For example: battery. ele.l 3.95 HALLICRAFTERS- With a clip-in RECHARGE- S -38. . 539.50 .. S -40 379.50 ABLE Willard Storage Bat- With TWO clip-1n S -36A. FM -AM -CW - 27.8 to 143 Mo 307.50 ton. Unbreakable. NON- Willard Primary bat- 8-97 - 130 to 210 Mc 391.75 SX -92 New FM -AM. .59 to 110 Mc. 250.00 SP°ILL, plastic $5.50 tß8 Çs. (Soo our Jan - one HAMMARLUND - New "Super -Pm" 1110 V AC .2 Amp. Trickle ad) $5.75 SPC -400 -X - .55 to 30 Mc. 334.05 charger $3.451 Speaker In Cabinet 113.20 HQ129X, completo with speaker -in cabinet 173.25 HSS EQUIPMENT BARGAINS NATIONAL - NC -240 D - Complete with speaker 241.44 Brand new, with diagrams and Instructions IlRO-5TA- 1 -ComplMO with pack and speaker 303.00 R 95 /Aßß- 7-Airborne Torsion of the Hank:- afters RME -45 - Complete with speaker 198.70 SX -28A Super Skyrider receiver. With cre- RME -84 - Complete with speaker 98.70 tal filter and tubes, less power LITERATURE ON ANY RECEIVER $ 137.50 GLADLY SENT UPON REQUEST RAK -7. Navy long wave 'IMF receiver. 15 to GOO BC -400 15 tubo RE- KC. With AC power - TEMCO 500 GA Sßgh`ÚIt used $19.95 A conservativo 750 watts output on all bands phono eptúeeea .... $59.50 (IIC- 400A-529.75) and CWI Rock stable YFO - simplified $1 tuning FR value to a post -war rlgl.... 800 Underchassis view Easily converted to a hot suporhet ham receiver. Soo Temco -75 GA $495 Photo F- shows power socket our prOvloUa ads. W e haves limited Quantltyaval labia for Immediate delivery Code Practice Oscillator AN /OSC -Tt. et 14.95 cable has been employed successfully Works on 110 Volt AC, eta In carrying caso. TWO METERS IS FUN! shown in Dynamotor. Runs on G or 12 volts. Delivers Now RTL compact Handio- Talklo. Pull with the unit Photo E. How- 500 volte at 100 MA. From í'E103 Paver Pack $995 out the antenna end you're on the air.... $31 .50 ever, insulation should be adequate and (Comploto with tubes and batteries - 535.95) PANORAMIC Abbott TR -913 . New. post -war model. FB $,52.00 it is a good plan to dip the cable in infor mobile or Peed W Add "eyes" to your receiver with a Hollleraftora Pano- station sulating varnish if it is of the woven ramic adaptor and Increase your operating efficiency (Complete mobile station. lesa only antenna - $81.61) and OSO acere. Completo with ten tubes 99.50 fabric covered type. and inetrudloD Y' MAIL ORDERS? Certainly! Just list everything you want in this ad, or A unit of this type should be wired TELESCOPING (items with the very best hookup wire avail- ANTENNA any ad, magazine, or catalog) and include Signet Corps AN29 -C. Sturdy, lightweight, braes remittance. Prompt Shipment. able. Ordinary radio pushback wire is renna extends to 12' 10", telescopes to 15 ". 5' diameter. Weighs only 80 oz. FR for mobile, or rotary Vy 73 de unsuitable as it simply will not carry boom elements. $1.95eaeh. at the high voltages in sta $1.74 present this type tJrc77[10H, W2AVA of equipment. Use wire having flame- [ proof glass, rayon braid, or similar insulation, capable of handling 2,500 volts. Use only rosin solder. The least bit of A.RRISON- RADIO CORPORATION

PRONG PLUG 5 STATIONARY 9 ,WEST BROADWAY, NEW YORK CITY 7, i e ONO- BArdey 7.9434 , FRvORr DFRr.- CAeq"HARR6ORA0" /1; w e pAMA!CA BRANCH:171 ,33 Hillside Ave.- REpublic 9- 41021_. "aj

F unit from the case or touching any part ing. Should the plate voltage be ex- of the internal mechanism. cessive a series resistor or voltage di- -e 2000 The 117 -volt power unit (Fig. 4) viding network may be required. Output 6.3V. L+ 52SV. T15W.V. furnishes 500 volts for charging the plate voltage must not exceed 600. SELENIUM RECT. 11 V AC capacitors, and about 8 or 10 volts for The low- voltage rectifier may be of Fig. 4-Diagram of the a.c. power supply unit. tripping the relays. It would be easily the type used in a battery charger, or possible to make a unit to deliver only it may be one of the types found on an acid will cause a flashover, especially in the low voltage, but it was thought de-. old loudspeaker since current drain is the switch contacts, and such a flash- sirable to include the high -voltage out- low. Usually it will be of the full -wave over may ruin the equipment. put to save wear and tear on the vibrator type, so connections may be altered ac- While not particularly dangerous power supply. Another important con- cordingly if necessary. With the large when in the Charge position, the output sideration is the bulk of a unit designed capacity (2,000 ttf) the rectifier output from the condensers is positively not to to furnish the 9 -10 amp required at 9 may be very small, since the capacity be trifled with when in the series or volts. Note that the transformer sec- of the condenser is sufficient to trip the discharge position. Hence, all testing ondary (high voltage) is connected to relays. must be done with due caution to avoid an 80 tube for half -wave rectification. Note the method of connecting the getting a serious, perhaps fatal, shock. With a small 4 -tube transformer, volt- power unit through a 5-prong plug so The main switch should always be re- ages should be about correct with the that batteries and vibrator are discon- turned to the Off position or to the two filament windings in series and nected when the shorting plug is re- Charge position before removing the using all the high- voltage plate wind- moved and the power unit plugged in. RA -DIO -CRAFT for FEBRUARY , 1947 53

www.americanradiohistory.com i

THE NATION'S HEADQUARTERS OMpANy FOR ELECTRONIC - IMMEDIATE EQUIPMENT! StR!$u,r: SHIPMENT! HEAR The New TdÇTERd SEE ithh the new TUBE aadaï'ae alá ry éeleaete a éásclsiPt.cVOItaln^It lugRlt' tabes' p LLT SIGNAL :pec.fioatfons: lama ñ WtoymylnPa'9oee BB A tensity tha lalón aleatanó lons t 1 MB.l^ F of theta abl TeetaFOTV r oá, P u taca tymsoñathroe motet LndlW ÌÌñe p {t ñt9ám1 one connecting tYPe ;aeYa«t v^'¡yu1tY'elemanls eD este tB_onlY agybehi.hand Ñew' Tlp tha r'o a tyhonMao[ rarëaaua in t° cttc tt NolerltT A.C. a S1mv t°D°uols mater uilt -1^ Cycles Í - poands- Volts BO N0 tdnaecuum-t^ ¿eted^r lr0bwe16hs 8 á'IOOSeFOñOBO fo 125 ¡°warte a oP CoLOmVl0t1Y Dortb r 34.85 utlane$39.5O _ glghlY senafitsty nNa Wester. camprotalnßWrattnó slnlm . Y. a^ ' / aIDDltfler BVas ...... Ws ... Qsint toBpined . GENERATOR .... SIGNAL óasDt°le ..... bleue signal. aottrudlata New Model sa a highly - e 1$.5 M xecma^td. The . W - lated-Dtpv115Ú Sc. a a on ton gife modu from 0 u an ad The Neto METER 11 rtc. t0by gcidbsmvlitude end IBoentelsuandl(TOm r°- UPER AÑÉ yodulattona(isect/valtalió^me4tv for telavtslon _eauallY mpdalettQl aewellbstterles. UREA sott-^,tteétdted an the A REACTANCE INN t re4DeneY CAPACITY alver' tlone ete $Z7.75 ECIBL FeatureRN GOOD-BAD All calibrations DECIBEL pád sciai panel. to Md 1 trmd ready °t s/ t! incluwdaual -ty V ' - °f Complete. 1 870 160 ° cO.O' CO. eltstken BALANCE µa11) le Sor áBn 28.4 DEPa51T. DISTRIBUTING B t lesP ando r- eers rassi 00 /a A con den with TERMS' ELECTRONIC YORK Test ('pmple ter ytsattvctiott GENERAL PLACE. 'd "y Wt complete / D 85 PARK cony ope retinó BF:F. .. Plesae sodC alo.. - ... : roe ,s MA^Rt% 1 mea satan gyolD . //D ...... ,hroue FogO / ' . o 'a9od r -..... Id subied 10 na, 1 Name . ...' so e ..... 0 enls 1 does E7E ...... a unils l F FaneMt . .. Stato -. . pll °wh¢n comDo^ unil CO . for anY < Y and ithra Addrasa aacevl ,ders ac tt to,d 1 ...... m,sYA *ed f y,t moY r0{und F4v/PM^ `ÓG ...... mpe,nourorea ;tm Purch 1Fa1 IF Clty _ 1or lurned ufe, ° 10 TO. C `.. - vlw Ahs unden,ondMS e

TECHNOTES WITH .. HUDSON MODEL SA -39 Weak and erratic reception, particularly at each end of the dial, often can be traced to the 9,600 -ohm resistor in the cathode lead of the 6J7-G oscillator mixer. The resistance of this YOU CAN component often increases to the point where local oscillations are weak or cease altogether. Replace this resistor Measure every type and with one of 10,000 ohms. kind of voltage in receiver WILLIAM H. EVANS, design and servicing. "VO- Alexandria, Va. MAX" increases your efficiency and profits by COUPLING CONDENSERS equipping you to measure Whenever leaky or shorted coupling r.f., i.f,. a.f.- actual signal condensers are found preceding a power volts- a.v.c., o.f.c., discrim- amplifier, the tube should be replaced Mator- a.c, and d.c. volts. at the same time as the condenser. The positive voltage placed on the grid by Input resistance is so astro- the defective condenser makes the tube nomically high you can draw excess current which often causes measure directly even in it to go gassy. Under these conditions, the highest resistance cir- distortion will still continue after the Post -wor design and construction at pre -war uninfloted price Is cuits. "VOMAX" is also condenser has been replaced. the secret of overwhelming demand for "VOMAX ", the true your output db. meter; HENRY M. HOFFART, v.t.v.m. Unequalled at any price, n is bought and used by the measures direct current up Shelton, Conn. Bureau of Standards, Navy, F.C.C., C.A.A., schools, universities, thru 12 Amp, auto set research laboratories -and by thousands of e.perience -wise range; resistance up to INTERMITTENT NOISE Intermittent noises that develop when service technicians. You, too, will find "VOMAX" your greatest 2,000 megohms. a set is tapped or jarred can often be profit meter. Only $59.85 at your favorite jobber. r traced to a pilot lamp making poor eon - tact in its socket. This condition may Send postcard for new catalog 35 YEARS OF RADIO ENGINEERING ACHIEVEMENT exist even when the lamp does not OVER of measuring instruments, cont- flicker. A sure cure is to build up the mumcation receivers, transmit- center contact in the socket with solder ters, kits and parts. See them so that the lamp will fit tighter.

ST , HARTFORD 3, CONNECTICUT 1240 MAIN at your favorite jobber. JOHN MEDNANSICY, Belle Fourche, S. Dak. FEBRUARY, 1947 54 RADIO -CRAFT for

www.americanradiohistory.com ANTENNA PRINCIPLES (Continued from page 33) Prepare NOW for a that which warned its GI attendant of the oncoming Japanese attack on Pearl Harbor. It is also similar to the array Better Job in used in 1946 to contact the moon by radar. RADIO ENGINEERING Irregular Patterns To properly serve two or more popu- lated centers and to avoid possible interference with nearby transmitters, it is often necessary to design a broadcast ADD TECHNICAL TRAINING TO antenna so that it radiates an irregular YOUR PRACTICAL EXPERIENCE. CLEVELAND INSTITUTE COURSES OFFER COM- PLETE TECHNICAL TRAINING RANGING FROM LOW -LEVEL TO COLLEGE-LEVEL. A. Master Course in Radio Communication. Covers fundamentals of Radio and includes complete preparation for FCC Commercial License Examinations. B. Advanced Course in Radio Communication Engineering. A college -level Radio Engineering Course. C. Specialized Television Engineering. Including post-war Television Techniques. All Courses Include The Remarkable Workbooks of Instructional Aids, prepared by the instructing staff of Cleveland Institute. Choose the course best suited to your needs-Start with the section you are qualified to enter -Use the economical CIRE "Pay -As- You-Go Plan." You may enroll for individual sections for highly specialised training. Study any one or more of the following sections if you do not require a complete course- I. Mathematics of Radio 5. Advanced Radio Telephony for the Broad- 2. Fundamentals of DC and AC Theory. cast Operator. 3. Essentials of Radio Communication. 6. Audio and Radio Components and Sys- tems (Design of Receiver and Transmit- 4. Communication Networks. ter Equipment). Write for descriptive folder No obligation CLEVELAND INSTITUTE OF RADIO ELECTRONICS CONTRACTORS TO THE CANADIAN BROADCASTING CORPORATION Successors to NILSON RADIO SCHOOL SMITH PRACTICAL RADIO INSTITUTE Founded 1939 Founded 1931

RC -2 TERMINAL TOWER, CLEVELAND 13, OHIO Approved for Veteran Training Under "G -1 Bill of Rights"

------(MAIL THIS COUPON) Cleveland Institute of Redo Electronles, RC-2, Terminal Tower, Cleveland 13. Ohio. Gentlemen: Please send information about your home study courses in Radio Electronics.

NAME ,. I desire training in I have had experience in broadcasting I] servicing ADDRESS operating onde. o CAA Army -Navy amateur other I CITY am High School Grad. College D Degree ZONE STATE D Check here for Veteran Enrollment Information.

magnitude and phase of each tower is taken as the reference, it requires no current and the position of each tower. control. The four dials represent: mag- Because of the many variables con- nitude and phase of the tower current; cerned, direct mathematical calculations distance and angle (in azimuth) of the become quite involved and consume a tower, with respect to the reference great deal of time. Several instruments tower. To operate this instrument, the are available for easing the problem, desired pattern is drawn with chalk on however. At least one mechanical de- the face of the oscilloscope tube. Then vice* has been designed for antenna cal- the dials are manipulated until the culations. same páttern is traced by the électron Figs. 2 -a and 2 -b. Patterns of Fig. I antenna. beam. The necessary tower factors are Hold page on side to better understand 2 -b. A still more modern and convenient instrument is the RCA Antennalyzert. taken from the dials. field pattern (Fig. 3). This also makes An oscilloscope is used to give instantly it possible to reduce power which other- the field pattern which results from the Nondirectional Radiation wise might be wasted on mountains, use of up to five antenna towers. Six- Many large and small manufac- lakes, and wooded sections. An irregu- teen dials control the Antennalyzer, turers are doing research in the design lar field pattern requires the use of four for each tower. Since one tower of high- frequency broadcast antenna more than one antenna tower. The pat- systems because of the widespread and RADeo- August 1948, p.652. ' CaArr. tern can be varied by adjusting the t RADIO- CRAMT, May, 1946. p.686. (Continued ón page 60) RADIO -CRAFT for FEBRUARY, 1947 55

www.americanradiohistory.com rMETROPOLITAN-N TELEGUIDED MISSILES Guarantees Delivery From Stock! (Continued from page 24) THE NEW MODEL'S -45 Electronics is also playing an ever - Colonel Harvey T. Alness and his 7th SIGNAL increasing part in both jet -propelled Bomb Group used this bomb during the and glide missiles. spring of 1945 to knock out the Jap- GENERATOR February, 1943, saw the first prac- anese supply railroad running between Battery Operated tical test of glide bombs (an ordinary Burma and Siam. bomb fitted with wing surfaces) against Another electronic missile, designated Self- modulated had a heat -sensitive electronic Signal Genera- a target in warfare; 58 B -17's launched Felix, tor, providing a 116 GB -1 glide bombs over Cologne, unit located in its nose, which by elec- highly stable signal. Gener- ates R.F. fre- gueneies from 160 Kc to 12:5 Mc on Funda- mentals and from 11 Mc to 50 monks. R.F. is obtainable separately or modulated by the Audio Frequency. Complete with leads, batteries $27.15 and instructions.

New Model 670 SUPERIOR SUPER -METER A Combination Volt- Ohm milliammeter plus capacity reactance inductance and d e c i b e l measurements NET $28.40 The JB -2 "bun-bomb" under the wing can be radio- controlled for a flight of 150 miles. New Model 450 Germany. They were released several trical impulses operating on the tail SUPERIOR miles from the target and guided to surfaces guided the missile in its free their destination by radio impulses sent fall to a target that was emitting heat - TUBE TESTER out from the releasing planes. The glide such as a steel mill or a blast furnace. "Speedy Operation" bombs were thus directed to the target The Razon bomb, an improvement assured by newly designed rotary selector without the necessity of the bombers over the Azon, was controllable by elec- switch which replaces into the danger zone of anti- trical impulses both in azimuth ..and the usual snap toggle getting or lever action aircraft fire. range. It had a gyro stabilizer which switches. Improvements constantly were made kept it from turning in the air during $39,50V NET in radio -controlled glide bombs. Drop the period of fall. The tail unit had bombs were fitted also with a special four elevators or rudders which per- CA -12 SIGNAL TRACER tail assembly that contained a built -in mitted this double control. radio unit which through servo units One of the latest developments in could control the angle of free fall of free -falling missiles, the standard 1,000- these bombs by varying the slipstream pound bomb known as Roc is fitted over the rudder surfaces. This free - with a television scanner in its nose. falling bomb was called the Azon bomb, The ground area that the bomb scans indicating it was controllable in azimuth during its free fall is televised back to only. the bomb -releasing plane, thereby en-

Now you can SEE and HEAR the signal. Simplest operation. Only one connecting cable -NO TUNING CONTROLS! Highly sensitive due to advanced Vacuum -Tube -Voltmeter circuit. Tube and resistor capacity network are built into the De- lector Probe. Complete with probe, leads. $34.85 batteries and instructions,

McMurdo Silver 905 "Spars" Signal Tracer... 639.90 McMurdo Silver 904 Capacit. Resist Bridge... 49.90 McMurdo Silver "emu" 59.85 SUPREME 543 Multi- Tester 18.95 SUPREME 589 Roll -Chart Tube Tester 48.95 SUPREME/599 Roll -Chart Tube and Set Tester 62.50 SUPREME 565 VacuumTube- Voltmeter 63.50 SUPREME 576 Signal Generator 68.95 DuMont Y Oscilloscope- 99.50 Writ. for RH Now I947 Catalog METROPOLITAN ELECTRONIC & INSTRUMENT CO. 6 MURRAY ST., Centel, NEW YORK 7, N.Y. The Roc televises a view of the target back to its control, who guides it accordingly.

56 RADIO -CRAFT for FEBRUARY, 1947

www.americanradiohistory.com General Elettrie RT -1248 15 -Tube Transmitter - Resolver TERRIFIC POWER (20 watts) on any 2 instantly selected, easily Famous pre -e usted frequencinegs from 435 to 500 Megacycles. Transmitter Collins tubas Western final. Re- ceiverfiver 0tubes including first detector and l'owl]. Autotune Transmitter and3 -7R7'. as IFs, with Ode -tuned 40 MC. plus a 7117. 7E8's, and 7Ft's. In addition unit contains This is the well known unit used in Army and 8e ate any sort t ternal equipment when relays D ysigedctoCope similar Navy planes that features automatic motor tun- finally desivgned for I2V periatio , powe pply Is not e ing of any of 11 front -panel preselected fre- as It Issrayy inch for any amateur to connect this unit for 110V AC. capablea of The quencies up to 18,100 Kc, as well as manual tun- for telephone In or for any kind remote ens ing at any time. The 'transmitter operates on trol applications as with drone airplanes. Instructions and din. running r tas on voice, CW, and MCW on all frequencies. This ende1°or voice, ó d for the receiver12iver either an AMor FM sot. As an FM et, the `receiver of the 1248 is capable beautifully designed unit uses an 813 final, and of better results than almost any of the commercial FM sets on push -pull 811's as modulator, measures 23 %x1314 the market, largely a alt of the superb engineering and meticulous workmanship employed in constructing are converter. x11, and weighs 70 lbs. Estimated average power oscillator and IF section.. Supplied in original cartons with 15 less of output is 150 Watts. Price including dynamotor If desired for marino or moobile` the dynamotor which will -$185.00. Write for literature describing any work on either 12 or 24 VDC ana supply all power for the set, units you wish more information Is onlyn $15.00 additional. - on. BENDIX SCR -522 Six Band Communications Receiver CHECK THESE BARGAINS Very High Frequency Voice Transmitter -Re- WIRELESS RECORD CHANGERS -These are ceiver- 100- to-166 MC. THIS JOB WAS Featuring. continuous coverage from 1600 Kc beauties-two post. with featherweight plastic GOOD ENOUGH FOR THE JOINT COM- to 18,000 Kc on a direct reading dial with the and chrome pick -up, plays 10' and 12" records MAND TO MAKE IT STANDARD EQUIP- finest vernier drive to be found on any radio at intermixed through any radio without connec -. MENT IN EVERYTHING THAT FLEW any price -- extreme sensitivity with a high de- tions. Complete with your choice of blue leather- EVEN THOUGH EACH SET COST THE gree of stability -crystal filter and phasing con - ette or walnut stained cabinet, priced at only COV.'T. $2600.00. Crystal Controlled and Am- trol-BFO - antenna compensatign - transmit- $28.96. plitude Modulated -High Transmitter Output receive relay -standard 6 volt tubes. Contains a D.C. POWER SUPPLIES -Operates from 110 and 8 Microvolt Receiver Sensitivity gave good plate supply dynamotor in compartment within V 60 Cycle. features perfect filtering for smooth- communication up to 180 miles at high alti- the handsome black crackle finislr cabinet, the er output. Output 6 Volts -20 Amps.: 12 tudes. Receiver has 10 tubes and transmitter 7 removal of which leaves plenty of room for in- Volts -10 Amps. Either 6 or 12 volts may be tubes, including 2- 832's. Furnished complete stallation of a 110V, 60 or -E5 -cycle supply. used at the same time. Made by one of Ameri- with 17 tubes AND POWER SUPPLY for 12 or These new receivers, which make any civilian ca's foremost manufacturers. Priced at $36.95. 24 volts, also remote control boxes and cable con- communications receiver priced under 8200.00 PUBLIC ADDRESS AMPLIFIERS -26 Watts nectors. We include complete diagrams and in- look cheap and shabby by comparison, are only peak output, complete with 5 tubes. separate structions for the simple conversion of the 522 to 844.60. Power supply kit for conversion to 110V, controls for Microphone and Phono Inputs, full 110 -Volt, 60 -Cycle operation. Your cost $44.50 60 Cycle, is only $8.50 additional. $65.00- value for only $32.00. .

GENERAL ELECTRIC 150 -WATT TRANSMITTERS ... NOW ONLY $44.50 These units manufactured for the Army Air Forces during the war by General Electric are now available at a price every amateur can afford. They are the same brand new transmitter. completo with seven plug -in tuning units, antenna tuning unit, dynamotor, connector plugs, cables. all tubes- and instruction book, which sold for as high as $175.00 last year. These trans - mitters have a frequency range of 200.500 Ifc. and 1600- 12,500 Kr. and will operate on the 10 and 20 -meter bands with slight modiCcation. Instruction booklet for conversion to 110V, 60 -Cycle is also Included. Transmitter dimensions are 21% z 23 z 9Sí Inches. Total shipping weight 250 lbs. Obtain yours NOW tar the lowest price at which this model has ever been sold CO MPLETE $44.50 BUFFALO RADIO SUPPLY 219 -221 Genesee St., Dept. 2C Buffalo 3, N. Y.

abling the bombardier to guide Roc to , that issue. Cam- its target by means of radio impulses. era tubes were to Differing from all other free -falling be pointed in the missiles, Roc utilizes a circular airfoil six cardinal direc- which can be tipped at different angles tions, each trans- by radio impulses, thus changing the mitting the view it angle of fall. picked up to the In the field of radio -controlled jet - control headquar- propelled missiles is the German V -2 ters, where all the rocket, which was used largely in the images were to be latter months of World War II in projected on a Europe for attacks on England, Bel- single screen, giv- gium, and Holland. This missile has a ing the command- complicated electronic control: there ing officer a com- are radio- controlled carbon deflectors at plete view of the the mouth of the rocket engine which whole scene of ac- control the. blast angle during take -off tion- Television re- and acceleration, and rudders located at connaissance the end of the four stabilizing vanes planes wereactual- guide the rocket after th'e jet motor has ly used to some ex- ceased to function, which is 63 seconds tent in the Pacific after ignition. theater, and adem- There is no field of either free-falling onstration of Block drop missiles or jet -propelled missiles in and Ring airborne which electronics does not play an ever- reconnais- increasing and important part, and un- sance television doubtedly this will continue to hold in was given at the future. Recently charged with the Washington last responsibility for all War Department year. [RADIO- investigation of guided missiles, the CRAFT, May, 1946]. AAF is subjecting new developments in Television was also this field to exhaustive evaluation. used on the Roc, . (It is interesting to note that a com- to transmit the pletely remote -controlled plane incorpo- scene ahead of it rating television was proposed by Hugo and thus permit Gernsback more than twenty years ago the control oper- ,in his magazine, The Experimenter, ator to guide it ac- November, 1924. The illustration re- curately to its tar- - -L produced with this article is from get.-Editor) Reproduction of the page which showed the proposed television plane.

RADIO -CRAFT for FEBRUARY, 1947 57

www.americanradiohistory.com SIMPLE MODULATION METER (Continued front page 32) JUST OUT! The observed pattern is very simple Failure to bypass the cathode bias resis- to interpret. There are no set of pat- tor in the final for the audio as well as terns to memorize. With no r.f. signal the r.f. component may produce this there will be a single horizontal line. undesirable result. Where unsymmetri- With the carrier turned on, sans modu- cal modulation causes an upward shift lation, 'a horizontal rectangle of light of average carrier power, it can usually will appear on the cathode -ray tube. be attributed to improper operation This corresponds to pattern A in Fig. 2. of the audio system or incorrect r.f. Regardless of the horizontal sweep fre- excitation. With suppressor -grid or quency selected it will be found impos- grid -bias modulation, these symptoms sible to see the individual alternating may indicate incorrect biasing of the waves of the carrier because their fre- modulating grid, or poor stability of quency exceeds the available sweep fre- the r.f. exciting source to the final quency by a large amount. stage. With sinusoidal modulation and cor- Pattern C in Fig. 2 indicates down- rect operation of the modulated stage, pattern B in Fig. 2 will be observed. Here the horizontal sweep frequency selector and fine control should be ad- to observe audio waveform justed the I II II II IIII II II II II II I IIII I II I II II II I II II II II I I II Ii Il II FOR upon the carrier, the same as if observ- BETTER ing straightforward audio from an am- A- Unmodulated radio- frequency carrier SERVICE plifier. With voice modulation clear wave. AUDELS OIL BURNER curves will not be seen, but the peaks CARRIER FREO.WAVE GUIDE -A new practical, r concise treatise, 384 pages and minima may be observed for ap- O -31 Chapters -321 Diagrams proximate modulation percentage. It is and Illustrations -covering Domestic and Indus- ' Jliii,IJI,l.lfr,fiiil41lliiili possible to into the microphone 1101'' N trial Oil Burnam. New from Cover to Cover. whistle Illfl'If l;'l'iIl'ii'lil!I'lli' Gives practical inside working knowledge of and hold a pure sine -wave audio pat- operation theory, construction, installation, MODULATION /. fasting, servicing and repair of all types of oil tern long enough for' close measure- I I burners. Includes electrical hook -ups and ments, when it is desired to check the Me (QjpRX 100) wiring diagrams of automatic control systems. overall audio gain and modulation char- l 1 Mel) up your ownekili with the facts and Ogures of your trade. Audele Mechanics Guides contain Prac- acteristics. AUDIO FRED. WAVE . Meal Inside Trade Information In handy form. is found by B-One cycle of audio modulation on Fully illustrated and Easy to Understand. Highly Percentage of modulation Endorsed. Check the book you want for 7 days carrier. Free Examination. PO Bend No Money. Nothing to pay Postman. )the formula M X 100 - AIIiN I,I IJ111 l rr l,, , I!!J, - -N - C U T HER E 2P I;,; w -- - - -5 'iulll P is the unmodulated height of carrier 11111'fl'l'ffffU'l''' MAIL ORDER signal as viewed on the scope tube. Q is C- Incorrect carrier modulation is in- AUDEL. Publlshers,49 W.23 St., MNY. Y N the peak-to -peak vertical signal dicated. Masse send me postpaid for FREE EXAMINATION books one -half marked tai below. If I decide to fume them I agree to produced by modulation. N is one-half mae ea In 7 Days on each book ordered end further mall $1 monthly on each book until l have paid Pelee. of the node -to -node signal produced by PN Otherwise- 1 v/M return thepi. ,,, modulation. These figures are clearly i I 0IPIJ I'll OIL BURNER GUIDE, 384 Pages ...... i1. REFRIGERATION & Air Conditioning, 1280 Pgs. 4: shown on pattern B in Fig. 2. POWER PLANT ENGINEERS Guide,1500 Pages. 4: indicates, 100 percent formula I As the I'I1IIIIIIIIIII I III' PUMPS Hydraulics &AirCompressors, 1658Pgs. 4: la modulation occurs when the minima or WELDERS GUIDE 400 Pages D -The reverse condition to that shown BLUE PRINT READING 416 Pages nodes come in to just touch each other, SHEET METAL WORKERSHan dyBoo . 38i1Pas 2. above. SHEET METAL PATTERN LAYOUTS, 1100 Pgs. 4: while the peak-to -peak signals swell out AIRCRAFT WORKER 240 Pages .. la to twice the unmodulated value. At 50 MATHEMATICS & CALCULATIONS, 700 Pgs.. 2. MACHINISTS Handy BookBook, 1600 Pages ... percent modulation these peaks and MECHANICAL Dictionary, minima increase and decrease the un- AUTOMOBILE DIESELE ENGINE MANUAL 400 Pages . . modulated carrier waveform by that MARINE ENGINEERS Handy Book, 1280 Pages 4. percentage. Thus by adjusting the sweep SHIPFITTERS Handy Book 272 Pages . . l: MECHANICAL DRAWING COURSE, 160 Pages L rate to make the audio waveform visible, E-The familiar pattern of overmodula- MECHANICAL DRAWING & DESIGN, 480 Pgs. 2: it is possible to approximate the per- tion. MILLWRIGHTS & Mechanics Guide, 1200 Pas. 44 CARPENTERS & Builders Guides (4vols.).. 6i centage of modulation at a glance. CR.f. carrier alternations as shown in these PLUMBERS & Steamltters Guides (4 vols.) . 6; is indicat- drawings are not visible on the tube MASONS & Builders Guides (4 vols.) . Unsymmetrical modulation MASTER PAINTER & DECORATOR, 30Pgs. 2: ed by any difference in the percentage screen.) GARDENERS & GROWERS GUIDES (4 vols.) 6i ENGINEERS.and Mechanics Guides of increase of the peak -to -peak signal Nos.', 2, 3, 4, 5, 6, 7 and 8 complete ... 12: versus the node -to -node signal. Simply Answers on Practical ENGINEERING only. This can indicate ENGINEERS & FIREMANS EXAMINATIONS . L stated, if the negative audio cycle re- ward modulation ELECTRICIANS EXAMINATIONS, 250 Pages . 1. duces the carrier pattern by one inch failure of one of' the tubes in a push - WIRING DIAGRAMS 210 Pages . . .. 1: increases push class -B modulator stage, single - ELECTRICAL DICTIONARY 9000 Terms ., 2. and the positive alternation ELECTRICAL POWER CALCULATIONS, 425 Pgs. 2. it by only three -quarters of an inch un- ended class -B modulation, incorrect bias HANDY BOOK OF ELECTRICITY, 1348-Pages 4. RADIOMANS GUIDE 914 Pages 4 symmetrical modulation exists. In this of a class -A modulator, or incorrect ELECTRONIC DEVICES 216 Pages . . . .. 2. case, with more negative signal than operation of the final modulated r.f. ELECTRIC LIBRARY, 12 vol., 7000 Pgs., $1.50vol. positive, there would be a downward stage. Incorrect biasing of the modu- shift of average carrier power under lated grid in either suppressor-grid or Name modulation. Incorrect bias in the speech grid -bias service may produce this re- Addreee- amplifier or modulator, poorly regulated sult. Where the final r.f. tube is oper- plate supply to the final, or incorrect ated 'with an incorrect plate current Oeeupatieu- r.f. excitation .of the final could cause load, saturation may prevent a rise of Lannoyed by these symptoms. Excitation could be plate current and only the negative R.C.F. excessive in the case of fixed bias, in- modulation cycle which reduces this sufficient in the case of grid -leak bias. plate current may be visible. This can 58 RADIO -CRAFT for FEBRUARY, 1947

www.americanradiohistory.com be due to wrong r.f. excitation or load. types of amplifiers and have tried dif- Single -ended class -B or failure of one ferent pickups of the same type and SERVICE- of the tubes in a class -B push -push mod- they all distort. ulator may cause pattern D of Fig. 2 to I am using a type of pickup with MEN'S appear on the 'scope. This last state- strings vibrating in the magnetic field. ment may sound confusing as we just [to ONE SPECIALS EDWIN COOPER, SMALL MOTORS: G.E. 27V. DC. 145 RPM. .85 mentioned that these same items could 51.49 Independence, Kansas Shunt Wound 1í/401H P.4ReReversible. 27V DC cause downward modulation. The an- amps. duty. The Answer: 4 S4 , shafta1.4 "g. rStSadt crackle finishh 3.5 swer lies in the phasing of the signal POWER RHEOSTATS. Heavy duty. Popular brands. 25 75. . 130. 175. 277. 500. or 1800 from the modulator. With single The trouble you are experiencing may hms1' .89 -ended 50 watt-2, 4, 40, 250. 300. 3K. 7500 or 10 K be caused by any one of the following: ohms 1.29 class -B, only tine-half cycle is produced SPECIAL! 50 tt 15 ohm rheostat .98 1. Overload at low frequencies. Dual 50 watt 200 ohm rheostat 1.79 in the output winding of the modulator. SNT.S-t1U .. ... 2. Improper mounting of magnetic MULTIPLIERS. 1W preeislon, sv Ire. Therefore the voltage produced makes 1740, 2500. 300. 3370.15290. 78ÓÓ. 30K. 50K or 400K .35 one output lead positive and one nega- pickup. Binding Boy'duty plated brass. 3. Mechanical loose contact, knurled head. O.D. 1Etj ". Ws" tive all the time with no alternation in rattles caused by high.1e 12nfor 1.00 polarity. These leads may be connected hardware, speaker cone hitting cabi- ALNICO MAGNETS to give either upward or downward net, or acoustical resonance at some low ml modulation. Each tube in a double -end- frequency. ed Class B modulator produces a half It will be necessary to determine cycle in opposite directions to form an which of these are causing most of the trouble. I therefore suggest that tt 1-Bar. alternating cycle or sinusoidal modula- I B shorter x engths. n r Inch s.12 you have amplifier tt2 -Face 1 Veal ./..x7/.. highs .98 tion. Depending upon which tube fails, the checked for its S3 -Heavy duty 3y-xl3/4"xóilr thick r4 -Faro ve"x. St k" high .39 the modulation may be upward or down- power -handling capacity at low frequen- r5- Polished. face 7/s"x9 /18.1 " high .35 low 9/18".1/2".1/2". 20 t r ... ward. Incorrect bias cies. Distortion at frequencies can :a -Pot' heyd"biar., high 1.100 in a class -A modu- r 8- ALNICO V.H'shole. poles KS .75 be approximated by using a reasonably #9-ALNICO V,hshoe, poles 9 18' 11" Ì4E1" lator, improper r.f. excitation, or incor- high .58 good audio -frequency oscillator and os- SIG- ALNICO 0,11-shoe. poles 1 "x11/2"x230" rect plate current in the final stage (too hi 8.55 cilloscope. Watch the wave form at low e 11-Horseshoe, ea pole 11/18" O.D.. 21/2" low for modulator output so that nega- high 1.3529 frequencies when the amplifier is prop- g12- (similar to tt5) high tive audio peaks are clipped) may cause SPECIAL SIZES IN QUANTITY. CUT TO 05015 erly loaded. If the strings are not vi- TUBES: Perfect condition. sealed this pattern to appear. Guaranteed 2s. 27. or -21 n'ó24. brating in a homogeneous magnetic field, 42, 77, 89, ODO. 8HO.s BKB, or OK7 -39cí Symmetrical overmodulation is indi- 75. 78. or 6A3 -S.59. #50. will Brand new R.C.A. UX -200 tubes In seated cartons. cated by pattern E of Fig. 2. Here ex- distortion be apparent, particular- Ideal detector -8 for $1.00. ly at the low frequencies. HEADPHONES Signal Corps HS-33 2000 ohms. cessive modulation may be indicated by adj. .26 With sponge rubber hó e^ cushions-$1.45. a flattening of the and To check for mechanical rattle, an os- Headbands only (as above). ith PL-54 & cord -4.39 peaks nodes of P54 plug and 13" tipped double phone rd -$.19 the cillator should be connected into the am, SELSYN SYNCHRO-TRANSMITTERS 115V. 80 cycle. carrier signal. Unsymmetrical over -' Brand new, in original Used In pal e plifier and its frequency slowly changed mitter follower.lower. 4"x5 .-per pair..510.49 modulation will flatten either the peaks TUBE AMPLIFIER (2.7C5. 7F7. 7Y41 Used as elec. throughout the audio spectrum. Any tronte supercharger control. 110V. 400 cycle. Con- or nodes, first one and then the other as tains: power trans. condensers (mica and oil), 7 rattle will be easily detected. Once the resistor.. 4 'octal sockets plus other components overmodulation is increased. several the 3 crackle ubls ,vrlh slide. in 'B1 Summarizing, this system has two causes are found, corrective measures Ì l Less tubes- will suggest themselves Frequency meter Tech. Manual (Navy) Theory & Opera. advantages and to you. taon. 39 Illustration & diagrams: 58pp one disadvantage when EXPERIMENTAL 5.15 compared to the trapezoidal method of AeludT TEES. A sizes L. hest types .íf00 ADIO TELEPHONE HANDSETS TS-13). Con- modulation Radar tracking of "rocketsondes" will tains 000 ohm r0Ó0 checking. The disadvantage push- to6e.taik switch. 1/a french type nit. Complete enable the'U. S. Navy to with 51/a" ft. Cord. PL -55 and PI.OB plugs 52.95 is that unlike the trapezoidal method of study weather RADIOMAN' HARDWARE TREASURE. Over 1000 L,, w S , lugs, etc. PLUS handy 58 indicating modulation, a sweep control at heights from 100,000 to 500,000 feet, anent d kit box S.59 18" N.B.C.N. RECORDINGS.RECORD Each contains 2 complete must be set to a frequency which thereby securing data of great value to 15 Inure 'VO of the Army" dramatic programs with Over 80 different titles. such a matches approximately the predominate aviation, according to Lt. Commander Whistling Willie, Cate Hoary, Philippine écmm, 33 1 /3 R.P.M. 5 east records $1.49 voice or oscillator audio frequency. Daniel F. Rex, of the Navy's Office of 3etc.2mfd /450WV tubular leolyticlea. 2t x4" 1s.79 2Omfd /200WV tubuar electrolytic.. O for 51.00 However in both cases Research and Invention. 5 TUBE AMPLIFIER fBendlxl. 2 -8NB. 3-8SN7. Orig. an unvarying used with mote Indicator. 27V. V. 400 cycle. note must be used if the patterns to Black enckle, pock -road. casese fitted chassis. 7V," are s4 *4)/t. ". Sñpg. wt. 7 Less tubes ... $2.49 ceramic Coil Form.. Low leas ribbed & grooved, leaa- be observed with any degree of accuracy. holes. wall. VictorraPoower Tfan:dorm"er for OmodelsxR 32. 45. B2 The advantages override any disadvan- Unshielded BAKELITE PANLS: A" glossy brown. 7"x10- S 5 9 tages. There is no needto open up a í10V PANEL LIGHT ASSEMBLY. I" amber jewel. D.C. bay base. Gun metal finish: O.D. 1" $.49 transmitter to secure any leads, making Neon watt. bulb. Double mat hay. basselY) .2 field checks (as in aircraft) easy. The For Examining My 2" Meter Case & Housing (round). Completo with glass & adjust screw. 1" deep resultant patterns are few and easy to New 7 Volume Set on 5.39 interpret without SERVICEMEN'S KITS memorizing. The sim- S 1 -R.F.. Antenna & Ose. coll.. 10 asstd. . .98 plicity ELECTRICITY r2- Speaker Cones: 12 o td. 4" to 1. of the system and its use of frooedge (magnetic Incl.). Less HERE'S a valuable book of 160 Electrical and Radio wiring moulded ÌS. .... 2 .00 standard available equipment is an- diagrams with charts and Instructions. Practical Informa- S3- BAKELITE MICA CONDENSERS: 50 td. tion you need towi n security and promotion. It's yours FREE SOdv n t 2.95 other good point. merely for examining my 7- Volume Bet on Applied Prac- tt bla ' HíPasßaO Condensers:ond slea óaT.00 urto 25mfd: 200.000WV. Standard tical Eteetrlei on 7-day's free trial. This 7- Volume Set 2.49 COVERS EVERYTHING ELECTRICAL from HOUSE r5- Electrolytic.: to siesta. Including WIRING to ADVANCED AC-DC MOTORS and EQUIP- Pallor & s 1.25 MENT. Thousands of diagrams and photos ... written so #8Dial Scales: ".std simian. & 'elide. both bogimers" and "old - timers" can easily understand. Mass 2.98 SOUND ENGINEERING Srule scuutcheon Plaltes: 125 uairpla...... llde.rule you full vision types 2.95 volume AT RISK, *8d 25 td. wood &. bfrkellte. Inelud- (Continued from page 36) 7-DAY'S FREE TRIAL set eKnobs: s .2o postpaid, for 7-day's FREE examination. I'll also send you SO-WaferSoccke °12 -on 4 to prong 35 the FREE book of 160 Shop Prints which you are to keep as S 10- Voltage Dividers; 10 a std. andard my gift regardless of w or not you multi-tapped. High wattages included . 1.98 Patent No. return the 7 -book (No salesman willeail.) s -S(oiellersCans: 15 asstd. for coils. tubes. 1,990,024, which is available set. V 1.00 25 Offer Limited -Send Coupon Nowt r 12 -Mica Fodder, & Trimmers: 15 asset at cents, from the U, S. Patent Office, Incl. multiple & ceramic base types .09 Controls: 10 asstd Washington, D. C. comp. Less 1.49 #5- Wire- Wound esistors. 15 asstd. ohmages, 5 damna. to 20 watts .9S DISTORTION ELIMINATION PROMPT SERVICE ON ALL SPEAKER & PHONO PICKUP REPAIRS. Minimum order 52.00 --20% The Question: NOT AN deposit required on all orders. } ORDER -JUST A WRITE DEPT. RC.2 I am using a 17 -watt amplifier and FREE COUPON REQUEST TO SEE BOOKS Please add sufelpnt postage. plug my electric guitar into it to use H.C.Lswls Press Coyne ElecMalSchool Dept soo s. PAIILINA STRfEET, CHICAGO 12, IIilN015' 27-12 I as the amplifier for the instrument. I Heed me the new? hams set.. ectrldtl." Also the book of 160 shop Prints which is s FREE gift tome re -' Either peee.dteaeorwhetter ornot li. Ma r.votume sets''llsubarea -' the amplifier or the speaker dis- sum Ne7.book set ín 7 dan end keep the ISO Shop Print. book saiift from )o nd owe yo y thin or per IS within 7 dare torts or rattles on a bass notes. I have I IßsÌ fs meat', v ail 121 Is 09d, er I'1í Bend tee eeeh rice of I I , 6Ìa.75 one roar FREE ComW aaUoa Service sod Teebolosl Bol- RADIO CO. tried several kinds of speakers (PM) 1 lee iooladed. 1 OF CONES AND FIELD COILS with good wattage ratings but the dis- NAME Aso I MAKERS tortion still occurs on high volume. I ADDRESS 65.67 DEY STREET. NEW YORK 7. N.Y. TowN__ -- WORTH 2- 0284 -5 Could you please tell me how to elim- 51.25 p I th cashe rief of BILIStoenérli way. Samee ï-.st:sa.mâ I 12,000 SO FT. OF RADIO PARTS inate this lion sod Honer -Back Guarantee. trouble? I have built many ad RADIO -CRAFT for FEBRUARY, 1947 59

www.americanradiohistory.com ANTENNA PRINCIPLES Low Cost (Continued from page 55) increasing importance of FM and television. FEILER TS -1 Requirements for high - frequency broadcasting present very special prob- WHOLESALE lems. First there is the consideration of distance coverage (Fig. 4). Because of Signal Tracer the line -of -sight limit, large pbpulation RADIO- ELECTRONICS centers can be properly served only by locating the transmitting antenna in the Saves Time & Guesswork heart of a city and high enough so that PARTS DISTRIBUTOR it overlooks most obstructions. FM, on All Radio Repair Work PLASTIC HANDLE NUT DRIVER KIT

MODEL TS -I ONLY

$ 85

Complete with vacuum tube (less batteries)

Fig. 3 -Field pattern of WMAL, Washington. Sizes 3/16 ", Va ", 5/I6 ", television, and multiple communica- 11/32 ", ' ", 7/16" 1/2" Easy to Use! Pays for Itself! tion require very wide modulation -fre- With handsome tool holder. GETS TO THE HEART OF RADIO quency bands, and consequently special Your cost -$4.95 TROUBLE IN A FLASH! antenna designs. As the carrier fre- Locates Causes of: quency increases, the length of a resonant conductor becomes smaller, and as NAVY ANTENNA1 Noisy Sets Low Sensitivity the modulation band increases, the Can be used indoors or outdoors. Parts Failure Distorted Tone cross section must be made greater. Easily mounted. Your cost -$1.95 Mistracking Intermittent Sets Many high- frequency antenna systems now in operation take on odd Servicemen! Experimenters! Here's an ab- METER SPECIALS solutely dependable Signal Tracing Analy- shapes and sizes, often named for the zer at the lowest price ever quoted for objects they resemble (cloverleaf, turn- HALLICRAFTERS - 5 MA - such an instrument! Enables you to test any stile, rocket). Each is designed for cir- METER $4.95 An- radio or amplifier just by touching the cular radiation at low angles, a wide WESTINGHOUSE to any portion of the cir- alyzer probe modulation band, and small mounting 31/2"-0-1 AMP. D.C. METER $3.95 cuit -the signal you hear in the phones area. permits you to isolate and locate the All these commercial antennas are 31/2 "-0 -5 AMP. R.F. METER $3.95 in just minutes. Easy use-no trouble to designed according to the fundamental 31/z "-0-15 VOLTS A.C. -VOLT- special skill needed. Works with any mag- have, METER $3.95 netic headset, 1000 ohms or higher. Re- principles already set forth. They quires only one 221/2 v. battery and one however, many interesting special fea- G.E.- 3%z "-0 -2 VOLTS A.C.-VOLT- No. 2 flashlight cell. Self- contained in com- tures, arising in most cases out of using METER $3.95 pact (63/4 x 43/4 x 31/4") brown metal case; different methods of solving the same WESTERN ELECTRIC - 3"-0 200 with snap -lock cover and battery compart- problem. A description of these an- MICRO -AMP. METER $ 4.95 ment. Compact bakelite probe houses tennas is worth an article in itself, and miniature vacuum tube and circuit com- the next number in this series will cover ponents; has 3 ft. cable. With excellent a'number of them. L PAD step -by -step instruction repair guide. An 8 Ohms. Safely Rated 3 Watts. invaluable instrument that pays for itself Field Surveys Has continuous range from 5 quickly! By mathematical calculations and by to 30 DB. Your cost 95c each IMMEDIATE DELIVERY! Place your order for the TS.I Signal Tracing Analyzer with your regular the use of precision mechanical com- parts Jobber. If he cannot supply you, write for name of nearest jobber stocking this Instrument - puting devices and such instruments as 15 WATT UNIVERSAL or send your order directly to us. the Antennalyzér, it is possible to de- OUTPUT TRANSFORMER c-D HORIZON DISTANCE IN MILES Uncased. Channel mount ....95c each 11!: loo IMMEN 11111 . 11IIIIM . u - CCClh.: .a:C:: = - 0 1.23 lax iCñstsatonussunu MAIL ORDERS FILLED PROMPTLY i 11 ...111 D IN MILES 111IIM- H IN EET UIIIII FEILER ENGINEERJNG CO.. Dept. 2.87 11í1 803 Milwaukee Ave Chicago 22. Illinois Jumm11III uuIIIII D Ship mo ono TS -1 Signal Tracing Analyzer III lo ." E enclosed. 1IIIII!!i1l'..1\ Send mo FREE descriptivo literature. 1./.. D 6 .aiiiiis_ssa all Covers IJhei Globe D Send name of local Jobber stocking /I111111-.1111 4 111111 3 ml11111 m ULII11 11111 .11111 ..1111 ARCH STREET Name somm- m- NI- 509 0 00 1000 10 000 PHILADELPHIA 6, PA. H ANTENNA HEIGHT IN FEET Address LOmbard 3.0513 Fig. Antenna and broadcasting City Zone .... State 4- height range.

60 RADIO -CRAFT for FEBRUARY, 1947

www.americanradiohistory.com r ;)/ n.r. I e ` r " oa... termine accurately the field radiated by f :r.. 1 - MAT I I _1--1 any o.`". i ...I antenna. However, the actual field 1 .. r - ---a intensity at any point is known only I .r.ao I wr + u ,' . .... I wr when ideal conditions exist. Especially I I ' at the higher frequencies, field strength and contour are determined not only by the radiation characteristics but also % by the height of the antenna and the `_ï}--F > r..... -... - ' S,,, _ ' i..'i, obstructions. -- C .'y .v l Í ...r ,ói ...... » Broadcast stations must supply .. -''4.... i ` actual field measurements to FCC ,...... r....s.0 ; the .. p ,--;,,s ,, I O..r,., ( so that possible interference between ...a.Q-`-,1-t( 7 : l i of ,. J i'""!^e!- l --ynu;aouc. t stations can be eliminated and maxi- '' / mum population coverage provided. ist -/ -j--o f /;I .». I - -'10.,,,, .,,, '9 `-1-- ) ...\-- I The Federal Commurijcations Com- I I- ..!' ) -.. ,c- .. \ mission requires the use of accurate re- r :W'. . ---- ' ceiving and continuous ,,,,r 1 1 1..:,,r recording equip- ;-. --., nYla.,."' ment for the survey. Generally the 6 . ?.r..r-. ; , ., uyp!.y -- \t .ú`.rr w`+",.. \ chart may be driven by the same sr. \ 07.- . ,r}__T{- -.». r. .. y mechanism which actuates the speed- uro : -ó ,- 1( ometer of the automobile or truck >`'- -1 +.'.W=u¡ 1--/ I I which holds 4...... r: ,... - ,f the equipment. Recording `..: ^ 'ÿ,,.*r°` is made along eight radials extending ea...... 1...7e ; t ` .. . from the transmitter, each spaced by ' '''.5'. 'L .%;'! I about 45 degrees. 7"Yr:'ì r--; ! Highways spaced so S "1 .0 MV/M :»: r/ s/ .,.: G conveniently do not generally exist, but ',p--,r\ f\^T`',a^ ! l it is usually possible to choose streets L.J .. -.',/l.is.`AVras .l r"., T. or roads which run approximately ,/k..,,<;, parallel to such radials. / ai ry...'/ \ ./° ... ;i gj; The I Qr.MÿtY- %r.7M^" survey must continue past the , y r t .f ,, points which indicate 1,000 microvolts O.0 per meter of field strength so that the required 1,000 -microvolt contour may o be drawn. A 500- microvolt contour around the station is required also, but due to difficulty ! / / .05 MV/M i :`.,. `t-... with fading at such low r field strength it is usually computed SCALE \0 50 40 O MILLS p from the data for the stronger field. =.t>_.... A \ typical recording is shown in Fig. 5. Fig. 5-A typical radio contour map, showing 1,000 and 500 microvolt -per -meter coverage. FIX ANY RADIO Amazing New Invention Find radio faults with a new simplified method. Repair all radios in minutes instead of hours. Revolutionary, different Comparison technique permits you to do expert work almost immediately. Most repairs can be made without test equipment. Simplified point-to- point, cross- reference, circuit suggestions locate faults quickly and easily. CHARTS, BLUE -PRINTS, TESTS, PICTURES, HINTS, JOB -SHEETS Learn time -saving trouble- shooting short -cuts; find any radio fault with ease. Follow the tests shown on 24 large circuit blue- prints. Over 1,000 practical repair hints. For all types of radios. Hundreds of simplified tests using a 5c resistor and any filter condenser. Introductory material for beginners and to serve as review for experienced radio men. Several chapters on test equipment. Complete plan in manual form, 64 job sheets, data on all tubes, large size: 81/2x11 inches. Schematics, pictures, charts. Sold on no -risk trial. Use coupon to order. NO TESTERS NEEDED NO RISK TRIAL ORDER COUPON REPAIR ANY RADIO IN MINUTES This newly developed method tells you how to locate the source of SUPREME PUBLICATIONS trouble in any radio set without equipment. Make needed tests, 9 S. Kedzie Ave., Chicago 12, Illinois measure voltage, trace the signal, by using only a 5c resistor, small Ship postpaid the new complete Simplified Radio Servicing by condenser, and a crystal detector. Inject signals without any signal Comparison Method manual for 10 days' examination. I am enclos- generator. Test parts by the new Comparison method. Test tubes with- ing $1.60, full price. I must be entirely satisfied or you will refund out equipment. Repair any radio expertly following simplified picture my total remittance. plans. Improve your radio servicing ability. Data on all sets, portables, NAME: AC -DC, FM, recorders, intercoms, P.A. Examine and apply the plan for 10 days without obligation or risk. Send trial coupon today - ADDRESS: RADIO -CRAFT for FEBRUARY, I947

www.americanradiohistory.com BUILDING A TELEVISER (Continued from page 29) bíieAtifr 2e411 audio amplifier. Apply an 8.3 -mc ampli- Live receiver or by Lecher wires. The mixer i RADIO PARTS tracked with the oscillator by adjustment of th tude- modulated signal to the grid of trimmer and by varying the spacing between and VI through a 50 -µf capacitor and ad- turns of the grid coil without changing the dis- just trimmer C13 for maximum output tance between the ends. After the circuits have from the audio amplifier. This will be EQUIPMENT an approximate adjustment of C13 and SIGNAL CORPS JACK BOX can be re- aligned later when actually receiving a signal. BC- 1 366 A Straight FM Receiver The sound channels of the televiser may be converted into an experimental receiver for the new FM sound channels by making the following changes in the tuning componente of the mixer and oscillator stages. The channel switch Sw2 and coils Ll through L12 are omitted. L13 and L14 are retained. Continuously variable tuning is required to cover the FM channels and a tuning Cast aluminum box held together condenser must be added to the mixer circuit. The conversion uses only two coils in a conven- by II banana plugs; 2 jacks, I tional antenna circuit. The new coils are wound as single and I double circuit, po- follows: tentiometer, and double deck Coil Turns Wire size Length (niches) Photo C- Placement of the underchassis rn is Ant. 17/8 24 r1ÿ hand switch. Single unit 59c. Lots been tracked, ganged coupling may be used on Grid 2 18 2 the two condensers. The circuits will work most of 10 45c. Lots of 100 38c. Ose. ya 18 efficiently when they resonate with the trimmers The oscillator and mixer circuits are tuned at approximately minimum capacity. -Technical OIL -FILLED CONDENSERS by two 15-µµf condensers, cut down to approxi- Staff, RADIO -CRAFT mately 5 µµf. shunted by 25 -1.4f air trimmers. This series on constructing a televiser will be .1 MFD -3000 V (round can) $1.25 The oscillator trimmer is adjusted so that the concluded next month with a discussion on how .25 MFD -600 V .10 oscillator will cover from 96.25 to 116.26 mc. to align the video receiver and select and install .4 MFD -600 V .10 This may be checked with a calibrated regenera- a suitable antenna. .5 MFD -400 V .10 LIST OF PARTS .5 MFD -600 V .10 VIDEO SECTION C62, C55, C57, C59-8 µf, 450 volte .6 x .6 x .6 MFD -90 V, 60 cycle .75 R1-65 ohms C54- .00025 of mica .05 x .05 x .05 MFD -150 V .75 R2, R75 -600 ohms C60, C61, C62 -.005 pf mica 2,000 -ohm pot. C64 -.003 of mica .22 x .22 x .22 MFD-300 V .75 R3- R4- 27,000 ohms C67, C68 -.05 µf, 2600 volts, mica 1.0 MFD-400 V .60 116, R12, R17, R22, R29, R34- 60,000 ohms C70- .000125 of mica C71 -.002 of mica 1.0 MFD-2000 V 1.50 R6, R31, R103 -6,000 ohms R7, R30, 1137, R71 -2,000 ohms C72, C75 -.001 µf mica 1.2 MFD-600 V .75 R8, R89- 25,000 ohms C72, C75 -001 of mica 2.0 MFD-600 V .75 R9, 1132 -3,000 ohms C74 -.0005 of mica R10, R15, R20, R26 ohms C77, C78 -.001 µf, 2500 volts, mica 2.0 MFD-I000 V 1.00 -70 R11, R16, R21, R26 -100 ohms C79-0.5 µf, 450 volts 2.0 MFD-1500 V 1.25 R13, R18, R23. 1146, R64 -1,000 ohms C80 -0.2 µf, 2500 volts, oil filled C81 -.01 µf, 1600 volts, oil filled 2.0 MFD-2000 V 1.50 R14, R19, R24, R28, R53, R73- 10,000 ohms R27., R46, R51, R68, RG1, 1172, RS8, 8101- 100,000 TI-Composite i.f. transformer 4.0 MFD-600 V .60 ohms T2, T3, T4, T5, T6 -Video i.f. transformer 4.0 MFD-1000 V 1.00 R33-150 ohms T7- Vertical oscillator transformer 1135- 15,000 ohms T8 -High voltage power transformer 5.0 MFD-330 V, 60 cycle .60 R36, R48, R52 -5,000 ohms T9 -Power transformer, 700 volts c.t., 150 ma 5.0 MFD-150 V, 500 cycle .. .. .50 R38, R -49, R57, R59, R94, R95, 6196, R99, 8100- F1- 10- ampere fuse Swl- Switch, s.p.s.t. 5.0 MFD-300 V .50 1 megohm R39 -5,600 ohms Sw2- Switch. 2- section, 4 -pole, 3- position 5.0 MFD-600 V .50 R40, R78, R87, R92, R93- 500,000 ohms Chl, Ch2, Ch3- Filter choke, 10 henry, 150 ens L2, L3, L4, L5, L6, L7, L8, Antenna coil 6.0 MFD-1500 V 1.50 R41- 25,000 ohms -10 watts Ll, L9- U42- 20,000 ohms- non -inductive L10, L11, L12- Oscillator coil 7.0 MFD-600 V .75 R43 -3,500 ohms -10 watts- non -inductive L33. L35 -300 µh 8.0 MFD-500 V .60 R44, R7G- 100,000 -ohm pot. L34 -175 ph R85 megohms L36 -250 µh 9.0 MFD-600 V, 60 cycle .60 R47, R65, R79, R80, R84, -2 R60- 11,000 ohms L37-125 µh 12.0 MFD-330 V, 60 cycle .60 R54, R55 -8,200 ohms 14:0 MFD-600 V .75 R56 -1.2 -meg pot. AUDIO SECTION R60-3 -meg pot. 15.0 MFD-300 V .75 RI01- X0,000 ohms -10 W R62, R67, R68 -3 megohms R201-500,000 ohms 20.0 MFD-330 V, 60 cycle 1.00 R63 -3,000 ohms R102, R207 -150 ohms R66, R70, R74, R61, 8102- 50,000 ohms 650.0 MFD-80 WV (Cor- R213-50000 ohms 869, R82 -4,600 ohms R203, R205, R207 -A, R209, R212, nell-Dubilier) 1.00 R77- 75,000 ohms R204, R208-2,000 ohms SPECIAL PRICES ON LARGE QUANTITIES RS3- 40,000 ohms R206, R210- 20,000 ohms -ohm pot. 150,000 ohms RECORD CHANGERS R86- 500,000 R211- R90, 3191, R97 -1 -meg pot. R214, R215, R216- 100,000 ohms Detrola -late model $16.50 net R98- 240,000 ohms CI01. CI02, 0103 -16 of 450 volts C2 to 60 variable Crescent -late model $17.50 net Cl, -4 µµf C201, C202, C203, C206, C207, C208 -.006 of mice C3, C4 to 20 pµf variable -3 C204, C205, C209, C210, C214, C215 -2 to 25 µµt RADIO KITS C6, C6 -2 to 12 µµf variable variable C7 to 20 apf variable 6 Tube "Super Het" $14.95 -2 C211- .0901 of mica CS -33 pif mica C212 -0.1 of 450 volt 5 Tube "Super Het" AC -DC . $12.95 C13 -2 to 30 pif variable C14, C15. C20, C21, C28, C29, C213 -50 µuf mica Special 5 Tube "Super Het" with Slide C9, C10. C11, C12, C47, C48, C73, C76- C216, C217 -.0002 of mica Rule Dial $19.95 C36 C43, C44, C46, .006 of mica 0218 -.001 of mica 25% °emit with order. Minimum order $2.00. C36, C37 -25 pf, 450 volts C219-.05 of 450 volt C38, C39 -16 µf, 450 volts TI2 -Power transformer 600 volts c.f., 60 ma; C41 pf, G00 volts C40, -.05 6.3 volts, 2 amperes; 642 -4 1µf variable 5.0 volts, 2 amperes SALES CO., INC. C60, C66, C68, C66 -0.1 µf. 450 volts LIBERTY 60 ma 600 volts CHI01- Filter choke 10 henry, 115 WEST BROADWAY NEW YORK 13, N. Y. C53 -0.I µf, C51, C63, C65, C69 -.25 µf, 450 volts RFC -2.5 mh FEBRUARY. 1947 62 RADIO -CRAFT for

www.americanradiohistory.com TRANSATLANTIC NEWS (Continued from page 35) ìosr°oss#ept eter, inserted at the 400 -ft. level..At the top of the mast is a new kind of adjustable capacity loading unit. This consists of four jointed radial booms, each 30 feet in length, with wires join- ing their extremities. At the 400 -foot level there is a platform carrying a large variable inductor, which can be so adjusted that the greatest possible non- fading range is obtained. Previously, severe fading was liable to occur in districts of Kent, Surrey and Sussex, ly- ing to the south -west of London. The new radiator is proving highly successful, providing fading -free reception in these districts. Blind Landings Britain, as a.good many G.I.'s discov- ered when they were over here, is liable to fogs in autumn and winter. For that reason the problem of blind landings at civil aerodromes is a particularly acute one. At present there is no international agreement on standardizing radio and radar systems of blind approach and landing at passenger and commercial aerodromes. It seems that it may be some time before the committee now considering the subject is able to come to decisions. Our authorities felt that something had to be done quickly. HERE are two brand -new books, just off Rather than wait, they have gone ahead the press -both important additions fo with the installation of a RADIO- CRAFT'S 1946.7 NEW MODERN LI- blind landing BRARY SERIES. Last molìth five other fresh system. The one adopted is the Ameri- titles were announced (see list to the right). -you- Watch this page for further titles each can "talk down" GCA. As an aid to month. blind navigation the Decca company has "Easy -to-read, easy-to- grasp, easy -to- apply" been authorized to operate its hyper- -is the best way to describe the books in bolic system, which makes use of very this popular series. Let them be your working tools to a better understanding of radio - low- frequency continuous waves. This to help you achieve higher goals. You will does not mean that we have like the handy size, the fresh up-to -date type, washed our the good printing, the carefully drawn sche- hands of the international committee. matics, and the flexible covers in attractive If they decide modern dress. 64 pages. Price 50c each, post- on different systems, paid. RADIO we'll adopt them. NO. 33 AMPLIFIER BUILDER'S GUIDE Insured Radio Maintenance A valuable book for the designer and con- Radio structor of sound equipment. Theory and con- CRAFT servicemen will be interested in struction of audio amplifiers are treated in a scheme for the guaranteed mainte- separate parts. The theory section contains an nance of receiving sets which has unusually wide range of technical informa- been tion on such subjects as r -c amplifiers, phase NEW launched in this country and is proving inverters, equalizing phonograph pickups and popular with customers. It is working volume expansion. well from the dealer's point of view, NO. 37 ELEMENTARY RADIO SERVICING MODERN since it assures him both a steady in- A book for the radio man who knows little come and a steady flow of work. Briefly about radio repair. It shows how to get started and keep going. A wide range of es- LIBRARY the scheme is this: when he purchases sentials is covered in logical sequence: a new radio the customer is offered Planning and Equipping the Shop, Systematic a Circuit Checks, Signal Tracing Methods. complete insurance against defects and Servicing Midget Receivers and other funda- SERIES breakdowns of every kind. In return for mental servicing topics. an annual payment the dealer under- SEE YOUR DEALER. 5OÇ each takes to make a thorough check -up each IF HE CAN'T SUPPLY YOU. USE COUPON. year as a matter of routine; to do any Here Are Five trouble- shooting, adjustments or repair RADCRAFT PUBLICATIONS work 25 W. Broadway, New York 7, N. Y. Other Recent that may be required; to replace D ALL 7 Titles free of charge Kindly send me the volumes (500 each. BOOKS any tubes or components postpaid) checked. HANDY KINKS that become faulty. Average terms are, D No. 29 29 AND SHORT CUTS 75 cents per year for each tube the D No. 30 UNUSUAL PATENTED set contains. I enclose 6 30 CIRCUITS 1944 -1946 Higher premiums are Np 32 charged as the radio advances in age. ADVANCED SERVICE The charges-$3.75 D No. 33 # 32 TECHNIQUE for a 5 -tube, or Nome $4.50 for a 6 -tube radio E) No. 36 RADIO TEST -must be con- # 36 INSTRUMENTS sidered in connection No. 37 í with the fact that HOW TO BUILD tubes (which Address are the most likely parts D No. 38 # 38 RADIO RECEIVERS to need replacement) cost a great deal more than in the United States. 'RADIO -CRAFT for FEBRUARY. 1947 63

www.americanradiohistory.com WORLD -WIDE STATION LIST rHARD -TO -GET PARTS page 37) POWERFUL ALL -PURPOSE INDUCTION (Continued from. MOTOR IDEAL FOR EXPERIMENTERS -101 USES LEEDS Sturdily constructed to precision standards.this self-startingIf- starting shaded Location and Schedule pole A.C. Induction motor Is Freq. Station number uses.ú Some of these are: Tim- ing Devices. Current Interrupters. SELSYN 6.160 COAX VANCOUVER. CANADA; 0900 to Fans. Electric SPECIAL 0210. `o Dapys PtoellCoto Devices, Electric Vibrators, Small BC -645A MOTORS 6.160 HHCM PORTAU- PRINCE, HAITI; 0500 to Grinders. Su nen and Polishers, Brand 0830; 1100 to 1400; 1700 to 2145. Miniature M N e Iv. Complete II5V 60 cycle Type Ice) Mod- all 6.160 HER3 BERNE. SWITZERLAND; 0020 to els, i reen,ns'man e ther app with tubes, includ- 5, Perfect- 0120' 0245 1200 to 1700. ons. p e r to 0700: ing W. E. 316A Guaranteed, 6.230 HRD2 LA CEIBA, HONDURAS: 1200 to Conaumee about e15 watts f pair $5.00 1400: 1900 to 2300. power and has o ed of 3.000 "Door Knob" -460- r.p.m. °When down. this 490 MC. Can be 115V 60 cycle Type 6.240 HJCF BOGOTA. COLOMBIA; 1700 to 2300. unit constantly 6.240 NIIN CIUDAD TRUJILLO. DOMINICAN to °a cú loaded converted to the II -1 mounted in REPUBLIC; 1600 to 2230. with 200 Iba. dead weight- THAT'S POWERI 420 =450 MC Ham armored case and 6.280 NCIB QUITO ECUADOR; 1800 to 2200. Dimensionsconient high has mounting studsltlsshaft le 'M' long B a n d. Detailed with indicated 6.190 HITA SANTIAGO. DOMINICAN REPUB- by 3/15' dinmeter. aand e In self- alIgning conversion & dia- scale. LIC; 1600 to 1800. retaining bearings. Designed for 110-20 volts. 60 -60 8.200 MGT BOGOTA. COLOMBIA; 1000 to 1400; Cycles. A.C. only. SbP. Wt. 2 Iba. grame supplied. PER PAIR ITEM NO. 147 Q,'9 Eí-5 1800 to 2315. YOUR PRICE 6.200 YV6RD CUIDAD BOLIVAR. VENEZUELA; $ 2 7 $14.95 $9.00 1700 to 2315. 6.310 HIIZ CIUDAD DOMINICAN MAGNET (TRUJ ILLO. ULTRA 6.330 COCW HAVANA, CUBA: 0000 to 2400. LIFTS MORE THAN 20 TIMES 6.340 HEI2 BERNE, SWITZERLAND. ITS OWN WEIGHT 6.360 HRPI SAN PEDRO SULA. HONDURAS; LITTLE GIANT MAGNET ARMY RADIO PHONES 1100 to 1415; 1800 to 2255. Lifts 5 lbs. easily. Weighs oz. 6.370 CSX LISBON. PORTUGAL; 1330 to 1900. Made of ALNICO new highmegnetle 6.450 COHI SANTA CLARA. CUBA; 0700 to steel. Comr.leta with keeper. world.. T 2345. Thetexperimenterl and [hobbyist will 6.480 H12T MONSIGNOR NOUEL. DOMINICAN find I l.` REPUBLIC: 1600 to 2400. high Quality permanent magneé Measures 1a/" k 1Lk Ship. Wt. 6.510 CP40 COCHAHAMBA, BOLIVIA; 1930 to ba. 1 22110. ITEM NO. 169 6.530 TGWB GUATEMALA CITY. GUATEMALA: YOUR PRICE $1.50 0000 to 1200; 1830 to 0100. 6.620 T02 GUATEMALA CITY. GUATEMALA; 1800 to 2300. GENUINE MICROPHONE TRANSMITTERS 6.710 ZLT7 WELLINGTON. NEW ZEALAND: Berate? trans- 0415 to-.0450. mitters taken large 6.720 PMA BANDOENG, NETHERLAND IN supply com- DIES. pany.. overstock. ok 6.750 JUT TOKYO. JAPAN. perfectly dry ales. be used 6.760 YNDS MANAGUA. NICARAGUA; 0800 to inter. 10000; 1700 to 2330. ms. 6.770 CP49 LA PAZ, BOLIVIA: 0700 to 0900; sho t- tine °1telephone err. 1100 to 1200; 1930 to 2100. house- o.house fcelte.arm -to -farm hone lines. 6.770 SINGAPORE, MALAYA; 0395 to talk through your 0935. alsotoradio or e 6.850 YNOW MANAGUA. NICARAGUA; 0800 to dictai one pick -up. Use- 2400. ful placements n bot, L tery-operated runt tele- 6.910 YNQW MANAGUA. NICARAGUA: 1300 to phone lines. 2300. ARE 6.980 MOSCOW. U.S.S.R.; 1600 to 1745; TRANSMITTERS. MADE BYmFKELLOGG. WESTERN They're perfect and were O.K.'d by ELECTRIC AND SpTRO MBERO-CARI,SON. excellent In 2915 to 2345. and remarkable snd Signal Corps inspectors. For battery - 6.980 FO8AA PAPEETE, TAHITI: Tuesdays and oneeseldom in [these times. Wt. le lb. Fridays. 2200 to 2400. ITEM Ne. 160 less phone or recordings, etc. Complete 7.010 XPSA KWEIYANG, CHINA: 2330 to 0030: YOUR PRICE $2.10 dynamic hand mike, 2 earphones, head- 0430 to 09011. 7.100 BISSAU. PORTUGUESE GUIANA; AMAZING BLACK LIGHT!! band, cord set and special 1600 to 1730. /345 Powerful 250 -Watt Ultra-Violet Souree 7.120 GRM LONDON. ENGLAND; 1145 to 1215; connecting cord set: A real 1445 to 1515. e best and pst practical of ult. violet light for special ONLY 7.130 HARGEISHA. BRITISH SOMALI - generalThrs LAND; 0800 to 1030: 1200 to 1300. une. Makes l fuor- 7.150 XGOY CHUNGKING, CHINA; 0630 to 1130. !nt nit.substances brilliantly fuslumi- nescent. No y 7.160 VIENNA. AUSTRIA: 0000 to 0200; needed. Fits any standard 0000 to 0800: 1000 to 2030. lamp 7.190 JCPA CAIRO, EGYPT; 0200 to 0300; 1500 opalescent hues in envious Laboratory Precision Variable Condenser to 7777; 2230 to 2400. types of materials. Swell for 7.210 FGY DAKAR, FRENCH WEST AFRICA. r parties. play etc.: to 45 -1500 mmf designed for use in general obtain unique 11 htinQ Resta. radio 605 -B Signal Generator 7.210 VLQ2 BRISBANE. AUSTRALIA; 0230 to Bulb only. Sho. Wt. lbs. 0890. ITEM NO. 7 Special $3.00 7.220 JCKW JERUSALEM. PALESTINE: 2330 to YouR PRICE $1.95 CARDWELL XE 240 XS 30 -240 mmf 0130. 7.220 SINGAPORE. MALAYA: 2230 lo 0130. Variable .100 Airgap Mycale: insulated, 7.230 G8W LONDON. ENGLAND: 0100 to 0115: WESTERN ELECTRIC BREAST MIKE $2.95 This is fine light -weight air- 0130 to 0330; 0600 to 0645: 0700 to craft carbon microphone. It weighs 0730: 0795 to 0900; 1045 to 1130; only 1230 to 1490: 1530 to 1715. ik¡.e Incomes with breastplate 7.240 VLQ BRISBANE. AUSTRALIA; 1500 to has can Aerovox 0.1 mfd 7500 vde Oil Condenser $1.50 1900. Inn adjustment so e adjusted to any desired position. C -D 2 mfd.2000 vde " " 2.25 7.250 NCI WILLEMSTAD. CURACAO; 1130 to There are 2 woven stra;strain. one 1230: 1630 to 2130. goes aroundand nec the other C-D 4 mfd 2000 vde " " 3.50 7.230 GWI LONDON, ENGLAND. around cheat. Straps be 7.260 GSU LONDON. ENGLAND: 2345 to 2400; fir m Aerovox 8 mfd 1500 vdc " " 3.45 0090 to Ieniosngeu oarrangement. ranent.lclIr 0200: 0630 to 0845: 0700 to This xcellent mike be 0800; 0815 to 0900: 1045 to 1300; adapted for home broadcasting or 1930 to 1700. private 10,000 VDC sontiingktbreastplate, it can be Cornell Dubilier 2mfd Oil Special used $12.95 omes mplete with 6 -foot con, and hard rubber plug. Finished In snerardlud The Patent Office reports an 81 per cent plate, n rustabie. Shipping weight. 2 Iba. ITEM 132 Westinghouse 3" Bake Case 0 -20 ma $2.45 increase in patent applications awaiting YOUR PRICE $1.49 Weston 2" " " 0 -1 ma action during the past year. Pending ap- 500 V Scale 3.50 WATTHOUR METER plications in the radio field more than Completely overhauled and ready for immediate service. 5 doubled during the year. Designed regular 110- Heineman 115 Volt Amp. Magnetic 9Ó cycle e A.C. Circuit Breaker $.95 Simple to °t al 2 `c ilree. line d 2 wires to the load. Stúrd. fly constructed in heave In Stock: New Type General Radio Co metal ose. 8%. high. 6t/." deep. Variata 5 Westing - Get Started in Radio hwide,ouse, G. E. Ft. Wayne. Sangamo o other available Type V -5 115V input 0 -135V output @ 10 "HOW- TO- DO -IT" BOOKS make Shp. Wt. 14 Me. 5 Amps 860 Watt $18.15 Geta a solid foundation In radIO by Type 200 B 115V input 0 -135V output these 170 Each cÌa written. profusely nillus. @ I Amp Watt 12.65 hcentains over inted, 15.000 rds. CO. Information packed °Into thewealthhandy HUDSON SPECIALTIES hooks. Excellent for reference-ide°I 40 West Broadway. Dept. RC -2 -47. New York 7. N. Y. If not rated 25% with order, balance C.O.D. for technical library. Your money I have circled below to numbers of the Item. I'm back If not satisfied. ordering. My full mittance of S tin- All prices F.O.B. our warehouse New York. elude shipping charges) Is enclosedlosed (NO C.O.D. 5 BOOKS for 50c ORDERS UNLESS cACCOMPANIED WITH A DEPOSIT.) No order under $2.00 OR deposit of S is enclosed 120% 10 red). nip Mer C.O.D. for balance. NO C.o.D. BOOKS for $1.00 ORDERÌ FOR LESS THAN 55.00. BE SURE TO IN- We ship to any part of the globe CLUDE SHIPPING CHARGES. Sent to You Postpaid Claie Item No. anted: No. 1 -How ToT Make Four tionary (Leading Terms) 147 159 180 87 162 33 Doerle Short Wave Sets No. 6 -How To Have Fun NO. 2-How To Make The With Radio Most Popular All -Wave 1 No. 7 -How To Read Radio Name LEEDS RADIO CO. and 2 Tube Receivers Diagram No. 3- Alternating Current No. 8 -Radio for Beginnen 75 Vesey St., Dept. 45 fOr Beginners No. 9- Simple Electrical Ex- Adress Ne. 4 -All About Aerials pert men t° Plea- Print Clearly Ne. 5- Beginnen' Radio Die- No. 10- Television COrtlend 7 -2612 New York City 7 Remit by check or ney Orden-register letter if you end nob or Ramas. CITY Stau RADIO PUBLICATIONS, 25A West 'way, New York (7) 64 RADIO -CRAFT for FEBRUARY, 1947

www.americanradiohistory.com SIMPLE FREQUENCY MONITOR -(Continued from page 21) THE SECRET'S OUT!

as the wavemeter is tuned through The New aod SpectarAdcdt resonance, or a meter in the grid or plate circuits of the oscillator will de- ACA-100DC AMPLIFIER flect at resonance. Another method is to measure the power absorbed in the 9s Recall 104 .eliveÌlit! wavemeter itself. This can be done with a pilot bulb or other r:f. indicator. DESIGNED BY A. C. SWANEY One of the important uses of a wave-

meter is in aiding VFO design. Cou- ,. A revolutionary development in amplifiers cleverly pling the meter shows at once whether to defy obsalescince and amazing in lis 0,designed the oscillator is above or below the de- 'performance.? New circuits. new materials and nevE: sired frequency, thus simplifying the 7 processes are actually combined in this one amplifier, work and saving time. Many transmit- to produce the most ictisfying musical amplifier, the world has ever known. If you ore ¿ne of those ters use high-sensitivity pentodes and noting persons for whom nothing less than the best frequency multiplication. In such cases a disappointment, -you ore one for whom the AC it is altogether too easy to mistake one 1000C won designed. Send for technical literotti , harmonic for another. Here the wavemeter is almost indispensable to keep from going out-of-band. It is also necessary when using the popular pi-network 398 Broadway, New York 13, N. Y. and similar antenna coupling systems. A. C. Shaney's FM-AM AMPLIFIER MANUAL is still available at 25c In such cases, a change in the tuning condenser is accompanied by an op.

N E W "SPARX" DYNAMIC SIGNAL TRACER

Touch "SPARX" prod to grid, to plate, of every receiver circuit. You'll local- ize trouble in 30 seconds per tube-trouble in o five- tube receiver located in Commercial type made for high frequencies 2' k minutes! True dynamic posite change in the coupling condenser. signal tracing at ri., if.. Thus, is possible to have a variety a.f. - plus indication of it presence or absence of of condenser settings for the same a.c. and d.c. operating band, and, in ,turn, the same tuning voltages, hum or distor- settings may apply to more than one tion. Tests phono pickups, band. The wavemeter gives a positive microphones, amplifiers, speakers-"SPARX" is your indication in all cases. New postwar design and construction, out ow pee-war price, Since the wavemeter does not require shop test speaker, toooll precise calibration or special low-loss explains view wise service technicians buy it by the thousands with visual and audible construction, many hams prefer to con- Matching -VOMAX", 904 laboratory C-R Bridge, 906 AM FM sigral tracing. "SPARX", radio's complete signal struct their own unit, incorporating Signal Generotor in sire and style, -SPARX" s the same out- they require. tracer-tester, will earn its whatever special features ' it will earn standing buy '. Al only $39.90 you. too, more low cost for you in no time -is in the One home-made job shown profits that oily other instrument you've ever bought. flat. photo. It is Made up of parts available in any shack. The condenser is a double- type (two 365 Ruf sec- unit broadcast Send postcard for catalog of tions in parallel). The wide capacitance OVER 35 NEARS OF RADIO ENGINEERING ACHIEVEMENT range makes it possible to cover the 80, rew measuring equipment, 40 and 20 ineter bands without plug-in W9/444/0-,574e.r., communication receivers, trans- or switching troubles. The coil is wound mitters, kits and ports. See them ST HARTFORD 3 CONNECTICUT on a 2%-inch long, %-inch diameter 1240 MAIN at your favorite jobber. lucite rod extending from the rear of the condenser. There are 18 turns of No. 20 wire closely-spaced in the coil, pushing the 80-meter calibration as far To make a measurement, simply in- which is wound at the further end of as possible towards the high-capaci- sert the wavemeter into an oscillating the rod. This makes it possible to in- tance setting so that ample room would coil and tune the wavemeter for maxi- sert the coil into practically any size be available for 20 meters and below at mum brilliance. Then read the calibra- and shape of tuned circuit for measure- the other end. The 40-meter point is tion. It is well to proceed cautiously at ment. A No. 47 pilot bulb is soldered found both by using a 40-meter crystal first unless there are plenty of bulbs directly to a condenser lug. and tuning in the second harmonic of on hand. Even 20 watts input to an Calibration is simple. The 80-meter the 80. This serves as a double check oscillator or amplifier can easily burn band is found by using an 80-meter against using the wrong harmonic. out the wavemeter bulb. For more ac- crystal and ,tuning to the lowest fre- Similarly, the 20-meter paint is found curate indication, withdraw the wave- quency of the transmitting oscillator. by using the second harmonic of 40 and meter until the filament just barely In this case the coil was designed by the fourth of 80. glows.-W2OUX. -RADIO-CRAFT for FEBRUARY, 1947 65

www.americanradiohistory.com ...in N2W getfey PROBLEMS OF INSTABILITY (Continued from page 25) it VARIETY resistors in series with the amplifier to correct the "error." It may eliminate

SUPERIOR grid and /or plate leads; rearranging a stray coupling . factor which was de- Model 670 the chassis ground -return aid voltage liberately inserted £o introduce a con- Super -Meter supply connections; etc. - trolled amount of degeneration to sup- A Combination Such minor circuit design alterations press oscillation tendencies. Or it may change the more or less unpredictable have created a small amount of regen- Volt -Ohm Milliammeter stray and conduction coupling factors eration to increase gain and peak the plus Capacity Reactance and may counteract regenerative effects tuning. Inductance and Decibel with sufficient degeneration to stabilize If a peculiar circuit design or ar- Measurements. the circuits. rangement or unorthodox wiring loca- Complete with test leads and At times, the instability problem may tion is noted in the wiring diagram or instructions $28.40 lie in uni -stage oscillation or parasitic in the equipment itself, it should not oscillation in a single amplifier stage, be "fixed up" by eliminating it or alter- RADIO KITS by "EASY BUILT" because of stray grid -to -plate coupling ing it to standard circuit design. Again, -AC -DC Electric Battery effects. This type of circuit instability intentional stray coupling factors may Model No. 2 Kit Kit with Cabinet complete with Tube, SM.- is rather infrequent in the case of mod- be disturbed and satisfactory circuit dal Variable Conden- ern tubes. operation upset. ser, Earphones, Bala- ton, Hardware and Special Fittings. Com- An obscure source of circuit instabil- Chassis ground return or voltage sup- pletely Wired Tube ity is the resistance-rectification con- ply connections made anywhere on Socket. Diagram on the Mounting Bus-Beady nection problem caused by corroded or chassis or at any point in the voltage Cut and Drilled defective riveted, bolted, soldered, spot - supply bus wiring are not always the $5.01 each welded or sliding- contact junctions in "same thing." At radio frequency levels, radio or sound amplifier circuits. Such a few inches of chassis or wiring has Battery operated. emit tuning. non -linear resistance connections may appreciable impedance and inductive Model No. 2B attractive wood finish cabinet. Complete with Tube. Coli. Battery. Headphone, Hard- not only cause oscillation but also loss and capacitative coupling effects. Insta- ware and Base. List Pria.- MN $3.33 Special in signal strength, hum and distortion bility troubles may crop up if these Klt Ne. I 82.13 effects which are at times difficult to original wiring connections are juggled Kit Na IX 5213 track down. about. Some receivers develop oscillation or Federal Teleco SELENIUM RECTIFIER Service and Repair Notes Replaces Rectifier Tube 5149 each excessively peaked tuning tendencies 6 or more 99c each In repairing a piece of equipment, the when all the r.f. or i.f. stages are lined original wiring should not be disturbed, up too accurately with signal generators PHONO MOTOR -with TURNTABLE to avoid changing the original stray cir- and c.r. oscilloscopes or output meters. 60 Cycles 116 Volts $3.95 cuit coupling factors. Similarly, when Such receivers perform more satisfac- replacing defective circuit components, torily on an alternately staggered Suitable for every Pho- the exact replacement part or an equiva- slightly off -tuned basis, and represent nograph instrument - - where low cost and lent should be used and replaced in ex- an exception to the general rule "a job dependable perform. - - done ance are required. actly the same position. well pays off in the end." If an amplifier tube ',shield, by -pass At times, defective corroded connec- $3.95 condenser, isolating resistor or choke tions develop in a circuit to produce or circuit shield has apparently been operational troubles. Such non-linear re- Famous Brand "omitted" in one or two of the amplifier sistance connections may be tracked VOLUME CONTROLS with SWITCH stages, do not insert one in an attempt down with a low -range ohmmeter, re- 75e each 10 for $6.96 5.000, 10,000. 25.000. 50.000. .1 mug. .25 mug, 85 mug. .85 -meg 70.000 ohm tap. .5 meg. .5 meg 60% tap. I meg. 1 meg 50% tap. 2 meg 50% tap. Out- side diem 1t,6'. shaft length 3'. fiat K. RADIO TERM ILLUSTRATED RESISTOR CABINETS -All wood con- $3.89 struction. Six .shelves, 24 compartments R.C.A. -T65 CABINET Packed in original carton. Beautiful inlaid veneer with grill cloth. Speaker bate, for 5' speaker. Bobber feet. $4.95 each. Three for $14 Bargain! Guaranteed! 100 Assorted Bypass Condensers 10-. 001 -600V. 10-.02 -600V. 15- .002 -600V. 10- .05 -600V 10- .005 -600V. 10- 1-600V. 15- .006 -600V. 10- 5 -200V. 10- .OI -600V. Value 511.00 Special -$6.95

20 r 150 WV. Electrolyt ic con- SPECIAL! dens.er20 Fr esh stock guaranteed. Value 5815 10 for $4.95

Write Dept. C -2 for our FLYER. 20% Daoslt w lth order required. Please add sufficient postage. Excess will be refunded.

Inc. `t/aaiet . ELECTRIC CO., Suggested by T. F. Bohannon 601 Broad St., Newark 2, N. J. Houston, Texas

66 RADIO -CRAFT for FEBRUARY, 1947

www.americanradiohistory.com sistance bridge or a cathode -ray scope and signal generator combination. CRESCENT Modernization Notes Automatic Care must be exercised in altering RECORD CHANGER tube types in a piece of equipment, especially when shifting to higher -mu tubes. In the old receivers using triodes in the r.f. or i.f. stages, the neutralizer stabilizing circuits have been designed for a specific set of tube and circuit Model C -100 stray capacitances and inductances. When such tube types are altered, some Physical Size: trial- and -error modifications of the neu- 153/4" x.12%2" tralizer circuits may be necessary to Plays Twelve 10" prevent unistage oscillation. or Ten 32" Records When considerably higher -mu tubes Noiseless are inserted into amplifier stages, the Child -proof Mechanism resultant higher signal voltage levels is Crystal Cartridge coupling, Reject Button may increase the inter -stage Finished in Neutral Beige Crackle causing oscillation and hum pick -up. In- PM SPEAKERS creased circuit shielding, rearrangement RECORD CHANGER ONLY S195O 4" Alnico (5) PM Speaker $1.39 ea. increased by- Your Cost Each 5" Alnico (5) PM Speaker 1.49 ea. of wiring and components, 6" Alnico (5) PM Speaker 1.89 u. pass filtering and omission of one amplifier stage may be necessary to eliminate LEATHERETTE BASE AS ILLUSTRATED PHONO AMPLIFIERS Above -Model H -100 the instability. 1 -Tube Phono. Amplifier $2.35 ea. Brown Finish, Made to Fit YOUR 3 -Tube Phono. Amplifier 430 u. In substituting diode detectors for Model C -100 Record Changer. COST for 5" grid -leak or biased detectors, it should 6" High, with Grille $4.25 ea. TUBULAR ELECTROLYTICS be remembered that although diodes are Speaker. 100-MFD- 25 V...á .22 ea. 10-MFO-450 V...$ .29ee. is quite possible 10-MFD- 50 V... .22 ea. 16 M F D -450 V.. . .39 ea. "non- amplifying," it V... .22 ea. 1010-MFD-450 V. 59 ea. for immediate 20-MFD-150 for them to develop oscillation effects Orders are now being accepted 30-MFD-150 V... .29 ea. 20.20-MFD-150 V. .29 ea. when a tuned r.f. circuit is present in delivery -no waiting. Terms: 2% check with 40-MFD-150 V... .39 ea. 30-20-MFD-150 V. .39 es. V... .45 ea. 40-30- M F D 150 V. .45 ea. order. Or 25% deposit, balance express C.O.D. 50-MFD-150 .150 the diode stage. Oscillation and hum 8-MFD-450 V... .25 ea. 50 -30 -M F D V. .59 ea. pick -up may take place if inadequate shielding and excessively long wiring SUPPLY CO. leads exist in the high -fidelity diode de- HOLLANDER RADIO tector stage. West Randolph Street Chicago 6, Illinois In wiring up new power amplifier 549 stages, precautions must be taken against parasitic oscillation, especially effectively with a sine -wave or square- in push-pull -parallel stages where an wave signal generator and a cathode - electronic "hunt" type of h.f. oscilla- ray scope. A sine -wave audio signal tion apparently takes placee. Cases have sent through the power amplifier stage been known in transmitter installations will show up as a sine -wave modulated where about a dozen varieties of para- by a fuzzy r.f. ripple when the scope's sities have been successively developed "V" and "H" amplifier gain is turned by power amplifiers with each circuit up. A square -wave signal will show a modification before being finally sup- small "pip" close to the leading corner pressed. which indicates a h.f. oscillatory tran- Such parasitics may result in -hums, sient condition of the circuit. birdies, whistles, distortion, loss in out- A simple and practical test is to touch put, excessive plate currents and over- the power amplifier grid circuits with a heated tubes which sometimes cause a tool held in . the bare hand or else to radioman to pull apart all of a trans- shunt the grid or plate circuits to mitter's or receiver's circuits except the ground through small mica condensers. one actually causing the trouble. This will result in clicks and shift in Radolek's big Free Profit In radio receivers, grounding the the oscillation noise in the speaker or Guide Catalog and Profit i speaker chassis and voice coil, shielding a complete cessation of oscillation. If Bulletin supplements keep RADIO PARTS the speaker leads, inserting mica shunt no change is noted in the birdies or you abreast of the condensers in the power amplifier grid hums, the trouble is obviously in the rapidly changing radio or plate load circuits, inserting non -in- r.f. or i.f. stages. situation. Buying from ductive low- resistance series resistors Minor circuit alterations which ob- Radolek means greater in the amplifier grid circuits, arranging viously do not, as a rule, result in in- values, better service SOUND SYSTEMS the power amplifier stage componente stability problems, are: increasing the and more profits. Make FREE to produce the shortest and most direct power ' supply hum filters, replacing Radolek your buying wiring leads, keeping the wiring out in glass -envelope amplifier tubes with headquarters. CATALOG the clear from other wiring and com- metal -envelope types, replacing old ponents, shielding the power amplifier type audio transformers with new high - Large Stocks tubes with roomy and well -ventilated fidelity types, substituting impedance shields, etc., are some of the methods coupling for transformer coupling be- Fast Service which can be applied to suppress para- tween audio amplifier stages (with sities, if and when they crop up. moderate -sized coupling condensers),

' modern Receiver power amplifier parasitics replacing old speakers with RADOLEK CO.. Dept. C-114 can be checked by removing the detector types, replacing grid -leak detectors 601 W. Randolph St.. Chicago 6. III. tube. If the trouble is in the ri. or i.f. with biased detectors, replacing two or Please rend your FREE Profit Guida Catalog. stages, the whistles and hums will three low -mu audio amplifier stages Name cease. If not, the trouble is obviously with one or two medium -mu or high - Addrma parasitics in the power stage. The mu amplifier stages (respectively), in- trouble- making stage can be checked (Continued on page 68) SAVE AT RADOLEK RADIO -CRAFT for FEBRUARY, 1947 67

www.americanradiohistory.com A 'Complete PROBLEMS OF INSTABILITY (Continued from page 67 ) Business System serting r.f. filtering in the power line tor circuits; omitting or adding some and power supply circuits, etc., etc. shielding in one or two of the amplifier The "Radio Service Standard Under certain conditions, altering ex- stages; altering the bÿ -pass condenser isting equipment circuits may result in or inserting r.f. chokes in the cathode Rate Book" such serious oscillation instability that circuits of one or two of the r.f. stages Price: $1.00 all the usual methods will fail to sup- are often more effective than shielding. press it. Only a major reshuffling and Altering the plate or screen grid volt- A compre- trial -and -error rearrangement of cir- age supply circuits of one or two of hensive pricing cuit components, wiring and shielding r.f. system and the stages by changing the by -pass Code of Ethics on a new chassis may result in sufficient condensers or adding r.f. chokes or thedesigned Radio to aid reduction of circuit coupling to result omitting isolating resistors; by con- RADIO SERVICE Service Dealer in stable circuit operation. centrating the voltage supply bus leads STANDARD to establish of each stage at RATE 100E fair and equit- that stage; by concen- able rates for Construction Notes trating the chassis ground return leads the servicing of each stage at of radios. A new or untried design should not - that stage; altering The book is be built in a permanent form but rather the amplifier plate or grid load circuits r-_-11M.1. divided into as a rough experimental model, espe- of one or two stages by adding shunt .aaaa.e-=LOOM ISIIIM..=11 e i x sections, networks eaaaa.wMIM of aaaaaw+p..wa. covering auto cially where multi -stage high -gain cir- resistors and condensers aotwem radios, A.C. cuits inadequately D.C. battery or shielded or port- portables, con- able equipment is involved. This will ö sole radios, ta- WAR SURPLUS allow elimination ble model ra- of instability and dios, record operational "bugs" by trial -and -error. players and Generally speaking, SALES- record chang- the more shield- RADIO-ELECTRICAL-ELECTRONIC rs. Each section outlines the general servicing ing employed, the more stable the cir- EQUIPMENT - PARTS - SUPPLIES procedures for each type of set and lists standard cuit operation and the lower rates for various types of repair service. the stray Parts prices and tube prices are conveniently signal and hum pick -up effects. Under NEW Navy RBL 3 Low Frequency listed, plus suggested standard rates for labor, certain conditions, increased shielding Radio Receiver service calls, pickup and delivery, estimates and T.R.F. type receiver, with regenerative de- alignment. may increase rather than decrease cir- tector designed to cover 6 bands frequency Includes Crystal Cartridge Digest, showing il- cuit instability. Shielding alone cannot range of 16 to 600 Kc; suitable for reception lustrations, voltages, pressures and list prices. of voice, MCW, ICW, and CW signals. Oper- Also includes registry of electronic manufac- suppress oscillation tendencies if other ates on 115 v. 50 -60 cycles AC. 7 Tubes sup- turers of radio and appliance items. stray circuit coupling effects are favor- plied with set. Also metal box containing spare equipment- condensers, resistors, switchm able to oscillation. es, tubes, replacement power transformer and In constructing resistance or other misc. items. Everything com- The !°Radio tmpe- plete, Only Service Work Sheet" dance- coupled audio amplifier stages, al WESTERN ELECTRIC Tungar converters; Price: 60c -sheet large inter -stage coupling condensers AC (50 pod) °lt to 24 volt DC; Complete should not be employed in an attempt slamy 19.95 servicing and to extend low- frequency response. SIGNAL CORPS DRY RECTIFIER CON- pricing de- The VERTERS; steps down AC input from 96v to tails on.your heavy long time- constant condensers -50 -60 cycles. to 24 -36 V at ,service job will set up a circuit condition wherein 1.5 amp125v s 19.95 are outlined SUPERIOR 2 KVA Power Stats ; input 116 on the "Radio the audio amplifier stages will take off volt AC, 50 -60 cycle single phase,-output Service Work in a low-frequency "motor- boat" type of voltage range 0 -136 volt; maximum rated Sheet." R e - output current 16 amp available over entire verse side il- multi -vibrator square -wave oscillation range of output voltage: weight lustrates which cannot be controlled. approx. 20 lbs. 29.50 your method For a given SUPERIOR 2 KVA 3% KW power stets, 2 of pricing. set of grid and plate load in tandem, each 116 volt AC single phase. Rates for resistances or impedances, increasing Same as the above but twice the service calls, input and output voltage 54.50 labor. etc ., -the capacitance value of the coupling Crystals 6000 KC complete are listed and condensers beyond a certain maximum in holders 1.95 explained. value results in little increase in low Standard rack cabinets heavy gauge steel. A space L gray crackle finish ; panel opening provided for frequency response. Special low -fre- 19" wide. 27" high 12.95 the dealer to quency compensating circuits do this PRILCO TANK ANTENNA -all aluminum, insert his copper weld, dark grey finish 12 feet long. name wit h much more effectively. Resistance- in 8 sections ; weight 10 oz.; base r u b b e r coupled amplifier circuit component 5/16 ", dia. tip 3(, ". Very special $ . stamp. Prompt Delivery A valuable asset to gain customer confidence charts should be consulted for suitable 250/ deposit required on C.O.D. arder and good will and a reputation for fair dealing. coupling- condenser values. Shipped F.O.B. New York. Minimum Order $2.00. Too many audio amplifier stages MICHAEL The ' °Radio Service Record" should be avoided in straight radio re- STAHL, INC. ceivers. 39 RCF VESEY ST. This will reduce audio circuit Tel. COrtland 7 -5980 New York 7, N. Y. Price: $1.25 (100 -sheet book) instability and achieve higher fidelity Providesa and a better signal -to -noise corn rehe naive ratio. One e....te.e ru I record system of driver is usually adequate to obtain full PREPAID ASSORTMENTS SAM a:.mD mnRn every repair job, output from the power stage. GUARANTEED FIRST QUALITY showing all ma- The oscillation problem is loo 41 3 Watt Realtors All Insulated.... $2.98 m.rs,en aule OM terials used, la- sometimes 100 Watt Resl.ton All Insulted 3.98 100 777 Watt Resistors All Emulated 4.45 bor, time. etc. particularly troublesome when a new 3.98 The "Radio 50 200 volt Paper condenser. -_- 2.46 t.r.f. receiver is constructed, particular- Mica Condensers ...... 2.95 Service Record" is ring-bound and contains con- 20 Dry Electrolytic Filter Condensers...... 6.75 secutively- numbered job tickets designed as a' ly where three stages are involved. 10 25 ft. Rolls !lookup Wire- .Aaot colors 1.98 file card, customer's claim check (with and Tone Controls -No Switches 1.98 space for Some 100 ft, Spaghetti and Vinylite .95 dealer's rubber stamp), and radio repair tag. of the usual methods applied to Coils I.F.. R.F. Ant. and Ose 3.95 A convenient way 600 (6 20 Wafer Ceramic and Switches 3.98 to order: lots books), prevent excessive instability are: care- 20 Auto pd 2'98 with numbers running consecutively. Price $6.25. 50 Electrical Wiring Devices. Plugs. Tape ful shielding of the r.f. coils, glass-en- asee, Elements. Fuses. etc 5.00 velope amplifier tubes, tuning condens- SEND FOR TRUTONE COMPLETE RADIO AND Available your ELECTRICAL LIST at ers, by-pass condensers and r.f. chokes. Terms: 25% deposit reoulFe with order. Balance Radio C.O.D. Merchandise étl t pr9Daid if full re- Parts Jobber Filter circuit isolation of the common mittance accompanies order. plate and screen grid voltage supply TRUTONE PRODUCTS CO. Oelrich Publications and cathode chassis ground return cir- 303 W. 42nd St. Dept O New York 18. N. Y. 1627 South Keeler Avenue Chicago 23, III. cuits; separation of cathode bias resis- 68 RADIO -CRAFT for FEBRUARY, 1947

www.americanradiohistory.com R, may be resorted to in stubborn cases. Rearranging the wiring, compon- e i;:,,,. ents and shielding; inserting r.f. filters Phono- ilarya[ns . in the power supply and /filament supply leads; inserting series ri. chokes be- 1 TUBE PHONO OSCILLATOR 53.95 tween the voltage supply bus leads to uses I I7N7 GT tube (less tube) 1 Or 1 . each stage; increasing the minimum WEBSTER "56" RECORD CHANGER e .. i4 .,"0000 i cathode resistor grid -bias voltage in automatically stops after last roc- U 526.65 each stage; reducing the plate and ord is played. v screen grid voltage supply to each stage; omitting one r.f. stage; may all AC-DC PHONO- AMPLIFIERS completely wired "el e...- have their uses. I TUBE uses I I7L7 $2.06 It must be remembered that a circuit 21/2 GEARS SHAFTS BUSHINGS 2 TUBE uses 50L6 & 35Z5 $2.94 modification which should theoretically 3 TUBE uses 50L6- 12J5 -35Z5 $3.53 SPACERS SPRINGS RIVETS suppress or reduce circuit instability, 4 TUBE uses I 2SL7-35Z5-35L6-35L6 $5.29 ETC. POUNDS BRACKETS CLAMPS may actually wind up in increasing (less tubes, speaker and volume control) COMPLETE rather than decreasing the trouble. This PHONO MOTORS $3.49 ASSORTMENT 1 a29 may occur when the complex inter -cir - WITH TURNTABLES -1 POSTPAID cuit stray coupling phase -relationships 2 POST V.M. RECORD CHANGER 7.95 OUTSIDE OF U. S. A. ADD 50e have been altered in such a way as to $, próduce a net over -all in -phase positive 3 for $52.00 GEORGE BROOKS & ASSOCIATES feed-back regeneration effect. Thus the PORTABLE PHONOGRAPH CASE Two 220 SOUTH HALSTED STREET CHICAGO 6. ILLINOIS addition of isolation filtering, shielding, -tone Leatherette finish dimen- $9.95 etc., may in certain cases, actually in- sions 153/4 "L it 143/4 "W x 8 "1-1 crease rather than suppress instability. If It's a CANNON -BALL PORTABLE AUTOMATIC PHONOGRAPH WIDERANGE TESTER ERROR RECORD- CHANGER CASE 9 4.95 It is a A mistake appeared in the diagram of the Widerange Pocket Tester, page `, GOOD HEADSET o a 790, August, 1946. Mr. Pallatz writes: TEST EQUIPMENT For clarity of tone use In my recent article entitled "Wide - Cannon - Ball sensitive range Pocket Tester" I erroneously McMURDO -SILVER "VOMAX" 559.65 phones. Assure depend- stated capacity measurements are voltohmmeter / able performance. Guar- that between McMURDO MODEL 905 "SPARX "$39.90 ... anteed to give absolute made "Minus" and "Cap." satisfaction. Write Head- jacks. Actually the checks should be signal tracer """'"'"v set Headquarters for made between the jacks marked ("Plus" AU item' subject to prior sale H-vy wr men* 20% with order balane. C.O.O. express nab 9 kb folder R -2 illustrating We prepay on theirM M complete line. and "Cap." $50.00 orders In U.S.A. Write for catalog clones,',. No damage can result from using the Electronic Parts, Inc., Dept. C2 C. F. CANNON COMPANY wrong terminals, but readings can be 622 W. Randolph St., IPRINOWATER, N. Y. Chicago 6, III. obtained only when the correct connections are made. ELECTRIFY your LAWNMOWER -)JOBBERS-DEALERSE- Battery Operated! AND SERVICEMEN! Self- Contained Self- Propelled We show you how to convert your Your Tube Worries Are own lawnmower for use with a car Over! battery. Save energy, labor and IF YOU NEED TUSES time with this self -propelled unit. LT- - Our simplified plans make it easy. COMPLETE PLANS $ WE'VE GOT 'EM! LEJAY MFG. C0..256 Lela), Bldg.. Minneapolis 8. Minn. We seek your exclusive tube business. Send us a trial order (in quantity preferred). This will convince you we merit Five Tube Superheterodyne Kit your patronage, based on low prices, -BUILD 15 RADIOS- Small Bakelite cabinet size 9" x 5" x 6". coetempl pars (except wire and solder) for the construction quick delivery and guaranteed merchan- standard superheterodyne receiver using 50L6. 35Z5, of a matched dise. 12SA7. 12SQ7. and 128K7. All parts properly Absolutely No Knowledge of Radio to chassis base. $10.75 Only Radio Tubes is our business. The follow. Necessary -You Need No Additional Price not Including tubes ing ie a sample of our bargains always in Kit stocks Parts or Tools Six Tube Two Band Superheterodyne In solid color wood cabinet (green. red). con- Type Type tains all parts (except wire and older) to con- 36 Page Book Written by Expert Radio In- ' S 7B6 S .32 es. struct a high grade 2 band superheterodyne receiver 80 ® LO ea. ® structors. Teaches You to Build Radios in a covering regular broadcast and short wave bands. 25Z5 60 ea. TAFT Q.... .32 ea. 1.6507. ®...... Tubes consisting of 2 -6SK7. $17.75 129.47 Professional Manner. I.12SN7, and 25L6 included. Price .. r Q... - .51 ea. j Receiver lU6 Q .39 ea. 6Y3GT Q... .37 ea. You Will Start with a I -Tube Receiver Six Tube Superheterodyne - ,designed walnut 50B5 Q .44 ea. 1625 Q an exceptionally artistic Before You are Done With this Kit You Housed In this Is such engineering cal SPECIAL 829 @ 2 -50 ea. good in the most Will Have Built II Receivers, I Public sebltot- provides design. locations. Built -in loop antenna of special Address System and 3 Transmitters. Broadcast band 540 to 1620 KC. 30 $23.65 ALL OTHER TYPE TUBES IN STOCK": Watts Input. Prize The SIMILAR LOW PRICES PROGRESSIVE RADIO KIT is THE Intercommunication System profes- WRITE, WIRE OR PHONE FOR OUR SPECIAL ONLY COMPLETE KIT-Contains Every- of PRICES sionaÌsionals andborntwo-way s onsists ó s mastersGGIP' thing You Need! Your Price J and one remote. noises 25% deposit en all orders. balance C.O.D., Mallory line filter-- useful In eliminating F.O.B. New York Instruction Book, Metal Chassis, Tubes, from offending electric appliances by Installing the with $3.45 Radio Parts, Soldering Iron, Pliers and filter at source. Compares favorably filters listing at $10.00. Your cost SENCO RADIO, Inc., Cutters, Screwdriver. Speaker repair kit (coldpatch). Eliminates $75 the use of messy cements. Price each (EXCLUSIVELY RADIO TUBES) Price $ 19.75 AU prices are F.O.B. New York City. 96 WARREN ST.. N. Y. 7. N. Y. TEL. CORTLANDT 7 -6065 Write for our ent, cubes large new test equipment, tubes ends large PROGRESSIVE ELECTRONICS CO. of whe replacement parts. 22 Havemeyer St., Brooklyn 11. N. Y. promptly. SPECIAL OFFER TO SERVICEMEN e chipship Bnywhero IN 1 COMBINATION Gentlemen: Dept. 125BC aAYES You MORE THAN 26/ Please send me the Progressive Radio Kit. t. plant' dlo piles $1.50 aato h eet-5 socket sizes r/4. 5/10 Check or Money Order Enclosed. Postage prepaid. 7/16. 4'i 1.2E C. 0.1i. I will psy postage. pc. Oeaulne Allen wrench set In leather - NAME flexible 5ashllto 1.EÓ ADDRE4 S Total value s5.ó0 OUR SPECIAL PACKAGE PRICE $3.50 CITY STATE h Item y be hated parately at above NOTE: Add 2% Bales Tax If In N.Y.C. SUPPLY CO. I Claremont Parkway, Dept. C. N. Y. 57. N. v. RADIO -CRAFT for FEBRUARY, 1947 69

www.americanradiohistory.com NEW RADIO - ELECTRONIC PATENTS AMSCO By I. QUEEN CRYSTAL PRESELECTOR The triodes may be separate tubes or halves of a twin -triode type. Glenefh F. Collar and Richard C. Young SPECIA1. Because of its connection to the positive term- Seattle, Wash. inal of the power supply, the second grid is Patent No. 2,405,999 normally positive and current flows in the plate This invention aids in eliminating interfer- circuit. Current through the bias resistor causes DE LUXE assortment ence due to atmospherics and from adjacent the first tube to be cut off. When a negative pulse consisting of trans- channel signals. It is especially useful where is applied between B and ground, the first grid formers, switch box, switches, chokes, only a few frequencies are to be tuned in since goes positive and current flows in the plate cir- knobs, resistors, coil forms, tube sockets, two crystals are required for each incoming fre- cuit. The pulse in the latter circuit is trans- panel light, insulators, terminal boards, quency. - ferred through the coupling condenser to the condensers, relays, fuse holder, wire, second grid, cutting off this tube and causing a sudden rise in plate voltage which is transferred volume controls, vibrators, neon lights, to the output circuit. 1 -21/4" speaker or Mike, etc. -Weight The condenser and resistor in the second grid approx. 25 lbs. circuit are so chosen that the negative charge (With every 5 is maintained on the grid for a desired interval. $4.50 The resistor may be adjustable as shown in order kits, i kit free) per kit to vary the width of the square wave. When the Write for our catalog. charge leaks off, current flow in the second plate circuit, again biasing the first tube to cutoff. The AMERICAN SALES CO. circuit is then ready for the next pulse. 1811 W. 47th 81. Chleaeo e. III. Ordinarily. a crystal filter is too sharply tuned If the input pulses are positive, they aie ap- to permit speech without distortion because of plied to terminal A instead of B. the high Q. In this circuit, an auxiliary circuit is added to reduce the Q as desired. The com- MEN MADE TO ORDER ponents are contained in a metal box with three Fit Your Abilities shielded compartments. The first contains a wavetrap and the antenna coil. The wavetrap ToThe Opportunities may be tuned to a persistently interfering signal. You have unused talents The second compartment contains the high -Q and mental powers. Learn to crystal circuit. X is resonant to an adjacent develop those faculties of mind channel frequency and acts as a abort -circuit to which today's world of business bypass the undesired signal. Y is ground for the desired frequency. The signal passes through 111 demands. Start life anew-with- it and through the auxiliary circuit in the third Aftout changing your affairs. Write compartment. C is adjusted to equal the capaci- the Rosicrucians for free Sealed tance of the Y crystal holder. If current of other Book telling how you may receive age -old than the desired frequency flows through the FREQUENCY METER teachings to achieve personal power. holder capacitance, it is opposed by the current Robert D. Schwartz, Devon, and William West Address: Scribe L.Z.A. through C, and cancelled out. Moe and Lowell J. Hartley, Bridgeport The ROSICRUCIANS, (Amore) San Jose, Calif. The auxiliary tuned circuit is adjusted for (Assignors to General Electric Co.) resonance to the desired frequency. It is found Patent No. 2,137,859 that auch a circuit loads the crystal circuit and Although reduces the Q. several types of frequency meters RADIO TUBES The coil is provided with a tap are available, there which varies the width of the response curve is need for a simple circuit Most Critical TypesinStock50L6,1A7,35Z5,etc. as required. which is easily adjusted and which can measure Brand New, in Sealed Cartons over a wide range. This new circuit uses only 100% GUARANTEED two tubes: a power pentode and a double -diode Repairmen and Dealers. Write For ELECTRONIC CAPACITANCE tube. The input voltage may vary over wide Available List at Trade Discounts R. Lee Hollingsworth, Riverhead, N. Y. a range, for example, 25-160 volts. It is required that the RADIO -EXPERTS (Assignor fo Radio Corporation of America) negative peaks cause plate current cutoff and 178 E. 93rd 8t., Dept. C. Paterson 4, N. J. Patent No. 2,407,424 that the positive peaks result in grid current. This invention discloses a new type of elec- A resistor Ri is placed in the grid circuit to tron tube which is essentially a variable capaci- prevent excessive current flow by producing the ELECTRICIANS! RADIO MEN! tance possessing no inertia. It seems to have necessary grid bias. Depending upon the instan- many possibilities, an important one being a taneous polarity of the Input frequency, therefore, Earn More Money! frequency modulator as described here. the pentode operates either at cut-off or at ELECTRICAL maximum plate current. In the first case there is no voltage drop across Rr, and in the second and RADIO case the voltage drop across it is practically equal to that of the plate battery. As a result, the condenser C1 charges and discharges periodically. TROUBLE The charging current must flow through D1 and therefore does not affect the microammeter. The discharge current, however, does cause de- ,?-SHOOTING flection since it must pass through Di. MANUAL 150 200 200 u GUARANTEED BY The tube contains a single grid with cathodes o %FREQUENCY COYNE and filaments constructed symmetrically on ir ©

either side. Electrons are emitted from each CI______cathode to set up a apace charge within the tube. The capacitance Yarlly/ODoysfs between cathodes varies with R2 D2 the intensity of the space charge. It is a mini- 6K Needed by au workers. maintenance mum when no electrons are present between grid men. beginners, old timers) Nothing DI OVER else like it. Saves time. helps boost our and cathodes, the dielectric constant then being pay...4 GREAT BOOKS IN OyNEI equal to that of space. 1. New Step-by-Step Trouble Shooting empty C22 R3 500 Course. 2. 500 Shop Prints. 3. Else: The tube is connected across a tuned circuit ! Large Size Radio Dictionary. 4. Spare Time Jobs (or a quartz crystal). The modulation input yr. Tedmical Counsel by changes the grid potential If the condenser d'scharge were complete Electrical FREE!1 from at an audio rate, thus and Radio mail COYNE staff, on causing a change in the tube capacitance and each time the meter would indicate in direct trouble- shooting problems. to the might Shop Prints SEND NO MONEYS See offer below. therefore carrier frequency at the same rate. To proportion input frequency and -Nowto read Satisfaction guaranteed by famous produce single aide -band modulation it is only be damaged if a very high frequency were im- COYNE "Learn -by- Doing" Elec- pressed. The discharge is limited by Cr, how- al dusethem trical School. Rush coupon now! necessary to suitably bias the grid so that it can vary only in a negative (or only a positive) ever, and at high frequencies the meter reading t H. C. 27 -71. tends to become constant (see typical meter L W1,_ r esident. apt FREE TRIAL I direction. a00 S. Pauline St.. Chicago 12, IN. COUPON I scale). Send postpaid Coyne's new Electrical and Radio I Trouble Shooting Manual. In 10 days I'll either re- The main frequency determining elements are turn It or send $3. then $3 monthly until total TRIGGER CIRCUIT Cl and R,. Typical circuit values for two fre- $1.50 is paid. ()Cash price 50.só-you save over 55e. I Same lo-day [roe trial d return privilege ° I Arthur J. Ruhlig, Washington, D. C. quencies are as follows: NAME Ago I Patent No. 2,405,237 Ra C, ADDRESS Midseafe frequency CITY Zone.... STATE This is a simple circuit which can generate 110 cycles 20K lOpf square waves in synchronism with input pulses. 1 me 30K .06µf 70 RADIO -CRAFT fof FEBRUARY. 1947

www.americanradiohistory.com o

THE RADIO PEN IN EUROPE SENSATIONAL CLEARANCE of IN EVERY April issue of RADIO- entire article as a new American inven- WAR SURPLUS EQUIPMENT CRAFT, for many years past, its edition, without, however, giving any hint at a Fraction of Its Original Cost tor has endeavored to have a little fun that it was a hoax! We offer hundreds of "hard-to-get" items in with his readers. To this effect he usual- This led to quite a few repercussions amateur radio supplies along with the beet in "HAM" equipment-all at a great saving to ly cooks up an electronic hoax, which in France when a number of other YOU. he disguises in such plausible terms French technical magazines let loose Our stock includes a wide assortment of: that the project looks real. Many an an Olympian roar of laughter at the Plate Transformers, Chokes, Relays Filter conds., Trimmers, Padders, Cables innocent reader, no longer astonished expense of their discomfitted publisher Tubes, Transmitting & Receiving Conde. at the latest electronic miracles, may confrère. Said the French Toute La Coax Cables, Fittings, Wire, Crystals Radio in issue: Switches, Sockets, Dials, Plugs, Dynamotore get caught in this scientific hokus- their July- August Test Equipment Coils, Chokes, Power Sup - pokus. That is, unless he plows through "It happened that a French journal- plies Receivers, - Transmitters, Rectifiers, Ampli- the entire article and reads to the very ist has taken the article seriously. In a fiers end where he finds the words "April professional radio magazine he dedi- Hundreds of other items 1st." He may then have a good laugh cated a very elaborate article to the Our latest bulletin is just off the press giving complete descriptions, specifications and bar- at his own expense, or cuss the editor description of the 'Fountain Pen' re- gain prices. Get your copy of BULLETIN roundly. Trouble is that most readers ceiver (but omitted to mention the 1 RC today. do not read the entire article; thus a source of his information). Gernsback We also carry standard lines as : Cardwell, B &W, Shure, Temco, Westline, I.C.A., Work- goodly percentage take the article at surely never expected such a repercus- shop Associates, Waterproof Elec. Co., Tele- its full face value. sion of his joke. For our part we found graph Apparatus, Atlas. S/C Labs and others. Catalogs on request. The interesting part of the joke is, that the subject gives rise to gratifying that none of the projects which are reflections intermixed with sweet mo- NIAGARA RADIO SUPPLY CORP. published every April are impossible! ments of hilarity." 160 Greenwich St., New York 6, N. Y. They are not only feasible, but usually Another French radio magazine of Please send me a copy of your latest BUL- LETIN 1 RC, listing hundreds of "hard -to- in a décade or more they will become Paris, Le Haut Parleur (The Loud get" radio supplies, and place my name Speaker) comments as follows, in a on file for future mailing. page -long article, translating the orig- Name inal American text: Address CE "The four -tube Radio Pen is in reality a good joke. Unfortunately, this was City Zone .... State not realized by a French confrère, who hadn't read end. Immediate Delivery On All 4 the article to the He Items coolly proceeded to reprint a full description in a recent issue of his journal. "We ourselves reprint the fantasy - ARA RADIO SUPP 6, N' Y. New York IAG wich St., 9 -7993 article just for a bit of amusement. Greenwich Green After all, perhaps we deal here only 160 BOwtin9 with a simple anticipation." That, however, was only the begin- ARMY -NAVY ning. It appears that dire international HEAD PHONES complications due to the Radio Foun- tain Pen are in the offing. In their issue of October 2, 1946, Le Travailleur Alpin (communistic newspaper) of Southern France, expostulates: "A nice little story)" A 4 -TUBE RECEIVER IN A F FOUNTAIN PEN. "Such is the promising title in the F 1ó.2- Cba¡¡i/ dunad:a./y/o, American Magazine Mum-CRAFT, apre,¡ eo%vei»en! di/Go/Wen which gave full descrip- 7-,té/é,o//ove crf'¡,tßt/. details and a exterieur: à tion of this new 'Marvel.' C, cha f/fetfíYde naf/ te _ Ct, C2, comeaya/eur,lfixey- Lr, L2, "This was also the title of an article L,I, Lq,/ampe,/fuperosiniature in /a French magazine informing its '.4,27,e, con tac fjuperieur er readers of the sensational invention GET THIS inFerieurde/a óa/terieP- B, without mentioning that this formid- catalog, latest devel- G oóinepriina/re accordée _ able 'Fountain Pen' was nothing but opments in radio and GoGii/e dáa>enne _ Cv, coo- electronic parts and de- áe?/ateur rariaó/e_ F. Goulov an amusing April Joke! vices, newest horn gear, ino/%%dácrord. "RADio -CaArr was, of course, dated gadgets and bargains. April 1, and the end of the article BURSTEIN -APPLEBEE CO., showed that it was only an April Joke 1 1012 McGee St., Kansas City 6, Mo. realities. Yet for the time being each (French 'An April Fish'). ._.- _..Send me your new FREE catalog. remains just an April Fool hoax. 1 "Our French Fellow -Journalist had I -Send me pairs of pheson of $2.49 plus 20c pair postage. I enclose The Radio Pen in the April, 1946, not seen this and he was the April Fool. 1 issue was no exception to this. RADIO- (In French: He swallowed the Fish). I s in payment. RC NAME CRAFT received the usual quota of let- "But let us not be too much aston- I ters from readers who wanted to get ished about this. Doesn't the American 1 ADDRESS more information where they could buy 1 propaganda try every day to hook us TOWN STATE either the complete pen or some of the with such jokes? Accepted in a more 1______components, etc. But the Radio Pen than favorable manner by certain proved an exception to the usual run (French) newspapers, it showers us of former, similar April jokes, in that ceaselessly with news items,, one more SPECIAL a serious technical magazine swallowed sensational than the next. The sense of While 1000 kits last. IO lb the whole article hook, line, and sinker. criticism of more than one reader is Radio Parts $is Assortment In their Juné, 1946, issue the French being sapped. Some heads have been so technical radio magazine La Radio Pro - deeply penetrated by the conviction that AMERICAN SALES CO. fessionnelle, of Paris, republished the (Continued on page 80) 1811 W. 47th St. Chicago 9, III.

RADIO -CRAFT for FEBRUARY, 1947 71

www.americanradiohistory.com TELEVISION FOR TODAY WILCOX CW 3. (Continued from page 31) i RECEIVER each pulse to set the level of the bias here and inserted into the video signal which will prevail during the associated through the 470,000 -ohm resistor. line of image deteil. Thus, by having To respond to only the negative syn- the tube's grid bias vary directly with chronizing pulses, the diode tube must each line, we can reinsert the d.c. com- be inverted. The plate will then reach ponent. its most positive value (with respect Note that the bias does not vary from to its cathode) at the synchronizing instant to instant, but only at each pulses. As the pulse reaches its great- pulse. Throughout the remainder of the est amplitude, the voltage difference be- line it is steady, affecting each video tween the ends of R2 reaches its great- variation in an identical manner. In this est value, with the top end negative. The CW Receiver is a highly way we do not erase the detail within This potential is applied directly across selective crystal controlled su- the line. Values of Rg range from 400; R3, Cl, and Rl. Because of the diode, perheterodyne unit operating 000 ohms to 1 megohm ; Cc - is then the 1- megohm resistor is effectively by- of any fixed frequency in the chosen accordingly. passed at this instant and condenser Cl band of 1900 kc to 16,500 kc. From the plate of the final amplifier is charged to its greatest value. The total band is covered by the adjusted signal is applied to the Throughout the remainder of the video means of four groups of plug - control grid of the cathode-ray tube. line, until the next pulse, the diode tube in coils. Extension of the range No intervening condensers are em- is inoperative while the accumulated ployed, since these would only above or below the specified remove charge across Cl discharges through the d.c. that has just been inserted. Be- the 1- megohm, range may be had by means of the 3,300 -ohm, and the cause of the direct connection, it is 10,000 -ohm resistors. The flow of elec- special groups of plug -in coils. necessary to place a positive voltage on trons is up through Rl, making the Plug connections are provided the cathode of the image tube to coun- grounded and negative with respect to for 1 10 volt, 60 cycle AC power teract the positive voltage at the con- the other terminal of the resistor. The source and for connection of trol grid. amount of charge on Cl varies from receiver output. An additional control must be pro- line to line, being governed wholly by vided at the image tube so that the each synchronizing pulse. The voltage blanking pulses of the incoming signal will fluctuate as described for the prev- * FIXED FREQUENCY RECEIVER coincide with the beam cut-off of the ious method. * 7 TUBE SUPERHET CIRCUIT tube. A potentiometer (generally Since the d.c. reinsertion occurs be- * CRYSTAL CONTROLLED LOCAL labeled Brilliancy Control) is placed in yond the final video amplifier, it is per- OSCILLATOR the cathode lead. With it, the observer missible to insert a coupling condenser is able to adjust the cathode -ray tube between the 1852 * COILS SUPPLIED COVER 5.6 TO IO and the control grid MEGACYCLE BAND bias so that no retrace is visible on the of the cathode -ray tube. However, there screen. is no coupling condenser after the d.c. * AUDIO AMPLIFIER STAGE CAP- Some commercial receivers obtain d.c. reinsertion. The ABLE OF PRODUCING presence of the 0.1 µf ZERO reinsertion by adding a diode tube. See coupling condenser remòves the previ- LEVEL DB OUTPUT ACROSS A Fig. 4. video 500 OHM LOAD The final stage now is op- ously high positive voltage from the erated as a conventional amplifier. control grid of the image tube and per- * TUBE COMPLEMENT The amplified signal is coupled to the mits a smaller biasing voltage at the 2.61(7 grid of the cathode -ray cathode. I -61(8 tube. At the same time a portion of the signal (that 2 -6C8G Image Synchronization I -6$N7 appearing across the 3,300 -ohm resis- 1-80 tor) is applied through a 10,000 -ohm While the video information is being resistor and a 0.005 Isf condenser to a supplied to the * COMPLETE SET OF EXTRA SPARE grid of the image tube, TUBES diode tube. The d.c. voltage is produced some directed voltage must be activat- * FITS STANDARD 19" RACK, 19" WIDE, 3)/2" HIGH, 111/2" DEEP 1852 FINAL VIDEO AMP. * GRAY & BLACK FINISH * PACKED IN WOODEN SHIPPING R3 CI i_ CASE ION .005 + BRIGHTNESS CONT. * WEIGHT ONLY 14 LBS. NET 3.3K RI I MEG * SHIPPING WEIGHT 42 LBS. COMPLETE WITH- INSTRUCTION * 8+ 6 8- 8+90V. BOOK, COILS, LESS CRYSTAL Fig. 4 -This method of d.c. reinsertion uses an additional diode tube.

ONLY $219. 5 HORIZONTAL SYSTEM HI-MSS OSC. SAW -400TH WAVE DEVEL- F.O.B.. N.Y. FILTER (15,150rv) OPED NERE 25% deposit required on C.O.D. shipments CHO SI TO CATHODE RAY TUBE

SAWi00TH LO-PASS OSC. WAVE DEVEL- FILTER (BON) MARITIME SWITCHBOARD OPED HERE VERTICAL SYSTEM 336 CANAL STREET NEW YORK 13, N. Y. Fig. 5 -Block diagram of typical deflection and synchronization system.

72 RADIO -CRAFT' for FEBRUARY, 1947

www.americanradiohistory.com ing the deflecting coils to position the video signals in their proper place on the screen. This is the function of the synchronizing pulses. Four Reasons There are two types of synchronizing pulses in a video signal, the vertical and the horizontal. Since all pulses have Why the same amplitude, their separation necessarily must be based upon their frequency difference. Horizontal pulses SERVICEMEN PREFER have' a fundamental frequency of 15,- RADIO 750 cycles per second; vertical pulses appear every 1 /60 second. In addition to their separation, it must be remem- WRIG NT VERIFIED SPEAKERS bered that at no time should either synchronizing system be permitted to BRIGHTENING STURDY CONES slip out of control. Tone Quality Construction Stay Centered

THE VERIFIED GUARANTEE PROTECTS THEM /LONG TIME CONSTANT Against Any Loss SIGNAL / i C

PULSE OUTPUT WRIGHT INC. Fig 6 -a- Fundamental diode clipper circuit. 2233 UNIVERSITY AVE. ST. PAUL 4, MINN.

MORE SMASH BUYS at National Radio Distributors ANNOUNCING- NOW! IMMEDIATE DELIVERY! The first volume in the long - THE NEW AND IMPROVED NA- awaited Massachusetts TIONAL RADIO AND PHONO KITS. Instituts The original and still the finest. of Technology Radiation Labora- All partsr brand new and uncondi- tory Series. bringing you- tionally guaranteed against defect. No War Weary Surplus. Component parts perfectly easy wiring and topnotch perform These. kits also feature new the engineering data you need anc . speakers. Plas- tic Cabinet.. Built- InBlloop Antenna. Dust -Proof backs, and illuminated Airplane dials. Instructions include to design RADAR SYSTEMS clearly drawn, a y to follow schematic diagrams. MODEL N. R. 7 -5 TUBE 105.125 A.C./D. C. SUPER. HETERODYNE. 01.6 ` 3525TubSKT' Tubes Net Price 511.95 Here iv an important Lote of 3 10.95 Look which the Kit of 4 Matched Tubes 4.50 presents T500MMf MODEL N. R. 5-5 TUBE TWO BAND A.C./D.C. SUPER general principles of HETERODYNE, as bove Freq. Ranger 'Band 1.550 to 1800 the design of various K.C. Rand 2 -5.5 to 18 Megacycles Net Price $13.95 radar systems. From as applied commercially. of Fig. 6 -B-The above Kit of 5 Matched Tubes 3i.5Ó the .standpoint of the MODEL N. P. 1 -4 TUBE A.C. /D.C. 105 -145 T.R.F. Uses 12 SKY, 12 SJ7 SOLO A 3525 Tubes. Recommended designer the book dis- A block diagram of the entire syn -. for Students, Schools, Hospi- cusses the basic consid- tals and Institution s. chronizing system of a typical television Net Price 510.95 erations which underlie %It of Matched Tubes receiver is given in Fig. 5. At some Net Price 3.50 and are particular to MODEL P. R. 7-Portable Ra. systems design. dio-Phonegmph COMBINATION Ready Soon point beyond the video detector, a por- KIT. is Features, Powerful tion of the video signal applied to a Tube Superheterodynenne radio, See N. R. T clipper tube which separates the pulses Self Starting Phono Mo. tor, Feather-Weight Crya. RADAR SYSTEM from the rest of the signal. Vertical and tal co-Up Arm horizontal pulses are separated by Luxurious leatheretteatherette pay 00 & 2- re. means of low -pass and high -pass filters. Id. with lid closed. ENGINEERING 527.50 Other names for these units are inte- Kit of 5`Mattche d Tube. Net Price .50 Edited by L. N. RIDENOUR. Assodate Professor grating and differentiating networks, NEW VANITY PORTABLE ELEC- of Physics. University of Pennsylvania. Over TRIC 900 pages. 9:9. $7.50. ready lo plug o from the similarity of their actions 110 V.A.C.sall A: lna: Ladles. to the same processes in mathemati- Vanity Case. Measures AFTER a general approach to problems encountered. this authoritative book take. up the leading design mu- cal equations. 6 q sideratlona for the Important components that make up lAlnico nd'erneat turn. The pulses obtained from the filters tore. radar set. Detailed examples of actual Systems ere in- Watt Beam Pow. cluded. Two new and important auxiliary techniques- trigger their respective synchronizing Outp t. with Tone A moving target indication and the transmission of radar Volume Control. displays to a remote indicator by radio means-are fully oscillators, locking them in to the pulse Luxurious treated. Anyone interested in the varied applications of coered carrying case. radar will find this new volume of Immense value as a \ill play 10e a l2- rec- frequency. If the two are close in fre- orda. bade, useful reference. quency, the lock -in will be sufficiently L. price $34.50 Tour Net 522.95 Meese Remit at least 25a/ with order. We will *hip balance C.O.D. We carry complete stocks of Supreme. 10 days' free examination -mail coupon binding to prevent the oscillator from Precision. Duo -tone Bright Star, Webster, Stance,. Merit, etc. WRITE FOR COMPLETE CATALOG. it's FREE! returning to its free -running state. The Cable address. ..ENARDEE... New York synchronizing oscillator controls the McCraw-Nl! Book Co.. 330 W. 42nd St.. N.Y. 18. Send me M.I.T. Radiation Laboratory Series. Vol. 1- charge and discharge of the saw-tooth Radio Distributors Radar System Engineering for 10 day, examination on National In 10 will send upofew e A saw postage -' turnysbook postpaid. (Wen pay tage on voltage generator. -tooth wave, cash orders.)ra applied to the deflecting plates or coils, 899 r Southern Blvd., New York 59, N. Y. will place the image properly on the Name screen. The purpose of the clipper is to Radios for the hard -of- hearing are now separate the synchronizing pulse from being made by a national manufacturer. Address the rest of the video signal. In opera- The radios have, in addition to the regu- City and State tion, then, it must remain unresponsive lar loudspeaker, a molded plastic ear- Company to any voltage other than the pulses. piece individual volume control ad- with RC. 2-47 (Continued on page 74) justable to the listener's needs. Position RADIO -CRAFT for FEBRUARY, 1947 73

www.americanradiohistory.com "TA B 1>llI>/ TELEVISION FOR TODAY (Continued from page 73) That's A Buy Transforme Cased "LANCEVIN" Prl 105 tO 250V /OOcy Bee 2240vCT/500ma. 12V/ 4.5A, 19.2/2.5A. 2.5V /l0A $11.50. TWO Perhaps the simplest way of achieving aration between signal and pulse. Typi- 1000 cycle hummer DC rapt -freq, d)ust$19.997 Transformer 50 /800cys /80&11SV: Sec 1000 this is to permit the pulse itself to serve cal circuits are shown in Fig. 7. Each VCT-300V 110ma. 8.3V/4.5A.5V/3A to 3V /.65A. 0.3V /.65A. 8.3V/l.25A. & 2 as the biasing agent. In Fig. 6 -a, the tube is zero -biased in the absence of a R'eaeed chokes 1OHI,//110ma & Two 3mfd/ il Condors 1641/ diode 33OVAC/I000WV& & 9.95 clipper uses the time constant of signal. When a signal is applied, current Transformer R and C to bias the tube so 3Ä 83V /1Á,8.338Á15V /Bd that all save flows, charging the coupling condenser. pulses Coondr2 /Ónrd&Smffd /800WVDC & Rack the synchronizing are eliminated. Throughout the remaining portions of chassis LOS chokes Condenser C and the resistor R form the cycle, when WTwolfacae 10lly /125ma/18Sohm. grid current is not 2.50 a low -pass filter with a relatively long drawn, Cc discharges through Rg. The YOU DON'T SEE IT - WRITE FOR IT time ASK FOR CATALOGUE constant, equal to approximately result is grid -leak bias. Since this form New Navy SP 3 Syñ hrose Complete 559.50 10 horizontal lines. Therefore, the of bias is determined by the most posi- S.C. Remote control Unit RC201 Corn /lete.. 92.4 voltage developed R B.C. Tuning Unit BC -740A & across (and C) tive portion of the signal, it works very Ext 2 crystals 1.00 cord 18 foot hvy duty SJ with Male' do will be determined Fmalee l 1.00 by the highest volt- well in producing sufficient bias to serve WE Dynamipc MlGephone 847334D4: with 50' blo 9.90 age applied across the input terminals. as a clipper. To aid clear -cut separation, Kenyon dynamic Ike to Grid tracer 1.95 Collins choke le 2ame /1950OV 4sE Cased 19.00 This, of course, means the synchroniz- lowered tube potentials are utilized. Micro-Mu Switch leaf SPDT 15A/125V. Two 1.05 ing pulses. Throughout the remainder Tone line to line 500. 333. Q25Ó. 200, 125. 1DB 1.93 of the line, while Woet'h''s Rector mot. 12.BV /1.3A gimp 3.40 the video voltage is Heaadset. 118 10A -S.C. new B.C. Map with 1.95 active, the plate is never driven suf- W. E. 509 Headset & 8 ft Gerd Plug ( 12i 4.95 ficiently positive to overcome the posi- e- G.R. VARIAC 2000U /860W /Oto13OV /SOty tive cathode bias. & Dial. Knob $14.95 INPUT C.R. VARIAC 2008 /I70W /Oto130V /60cy A commercial application is shown in Ri 9.95 Sola LAB model Constant Voltabe Trensf Fig. 6 -b. One half a 6H6 is used for pic- 6OWatt /95 -125V 15.00 ture signal detection (not shown) while Condor IOmfd /600WVDC oil (2.2.5mf6&5mí0) 91.25 Condor 2omfd /800WVDC (1 -2.4.5 -8mí0) 2.50 the other half is devoted entirely to /5000WVDC oilil (181145) 08.75 Coo toned 12.00 combined pulse rectification and clip- 6SJ1 Gondar 3 mfd /330VAC Two for .... /1000WVDC ping. Rl and R2 form the pulse detector Condor Pyre of ]mfd%330VAC /I00v0WVD0 2.95 Condor RP 25mmfd /10000V wkg new 3 for .75 load. Here the rectified is Condor CD oil Omffd /15000WVDC 2 signal devel- Condor GE Pyran 1 4 section 28mfdiedO oped. The' VAC/2000C 7.85 time constant of the load is WE mincer min PP /P to PP /C Input K89929 1.20 WE PP inppt & PP driver transfo 0Vß/905 6.9S set essentially by Cl and Rl. At the dynamic to grid Ouncer choke i pedence .49 application of each pulse to the tube, a short flow of current takes place, re- Fig. 7-Triode and pentode types of clippers. PRECISION WIRE WOUND 1% RE- SISTORS, IRC. SHALLCROSS. NIP. charging Cl, and, at the same time, CO. INST. RES. Co.. ONMITE Fon It should be noted METERS. Rg1t,00ES AMPLIFIERS. causing the pulse to appear across R2. that the foregoing l5E0Ó 2000: '164%0 43000 This voltage is passed on 1852 triode and pentode clipper stages are 7500 7950e 30000 15000 to an 17000 30000 75000 100000 synchronizing essentially similar in form to the d.c. 140000 147000 166750 201000 pulse amplifier. The se- 229000 250000+ 950000+ REST inductance insertion network of Fig. 3. Their dif- "TAB" SPECIAL 3 for $1.00 107o) ries L maintains the re- 250000 294000 314000 333500 ference, however, lies in the values 353500 400000 402000 422000 sponse of this network to the higher of 458000 478000 THREE for 51.50 the grid resistors, and 3000 70000 THREE for S1.95 frequency components of the square - the electrode 1 Megohm 1 %aory THREE for 52.45 shaped pulses. operating potentials. In the clipper, Rg is high, generally 1 megohm or more. Dynamoton 12V not /275V/110ma 91.93 Note that the Dynamoton 500V /Soma Coney. rated & filter circuit in Fig. 6 -b em- & 273V unit 3.49 Further, the operating voltages are low. Weston 476 9p 3 WC 15VAC (910) 4.25 ploys a separate diode for pulse recti- Weston 0E 10 BDB 500 /800ohm L 3.95 In the d.c. reinsertion circuit, Rg is Weston fication and 301 meter 10KV /1000ohms V &6 Mult 15.00 clipping, and in addition a WESTON 706 insulation tester & Megohm- much lower in value and the tube volt- In k 24.95 separate amplifier. A simpler arrange- Electronic VOM 11meg ens 3 -300V & 10 ages are higher. The high grid resistor 24.60 ment would have resulted if the clip- SC A27 Phantom Antenna new ith manual of the clipper biases the tube to the Contains ping did not occur until after the first /3000V &12 AWL plaque 2o m/40 1.95 point where only the pulses cause Dynamic mike & min transit to G new 1.95 video amplifier. plate In this way, the addi- current. The lowered plate voltage aids 'CRYSTALS MTD "BT" CUT Four for... $3.00 tional amplifier would have been un- DC -I5A Standards 200KC -.± IOcy 5.95 this action. In the d.c. insertion circuit, CINCH MICA necessary. B Dual crystal sockets. 8 for 1.00 the negative bias is less, permitting VE Crystals boxed 1N21 -22.23 3 for . 51.29 The chief disadvantage of a diode current flow WE Crystal boxed sealed 1N26 UUF11 /lem ea .54 to throughout the entire CR 1'rnlsioovyyn 1KV /lme9 I,4% H'mtelly clipper is ($25) 1.99 the loss in amplitude that 'video signal. In both instances, how- WSTGHSE DUAL ) IND 200 microamp 4.50 GE Meter 2t/ß WC one amp RF results. With a triode or a pentode ever, it is the synchronizing pulse por- GE Meter 2 B'C ave amo RF 3.30 GE & DeJu 22,60 WC one ma DC mtr 2.95 connected as a pulse clipper, we gain tion of the signal which is Sock Octal Amphenoi 7898 mica H (18e) effective in 5 t some r 1.80 amplification plus a sharper sep- setting Socket I.00talMO) 89 -8X (20e) 20 for 1.50 the bias. Socket Octal ceramic 4985.a8 (45c) 15 1.30 So kaetfOctal ceramic & saddle ring Cinch 1.50 S ck tumsghul ceramic 49 -SSIUL (1.251 .98 866A GE Comb, tubes. SI trans!. caps, sockets DETECTOR FOR THE OSCILLOSCOPE 872A Comb tubes. SI trend, taps, sockets 12.00 808 RCA tubes new Std S.C. BOXED Two 5.00 every service shop of re- be heard as ket miniature bayonet DialCO 99 -4931 well as seen. This speeds L90 h 9 .15 NEARLYspectable size now has an Socket Hubbel 13A /125V Twist lock 7588 oscillo- services greatly and many troubesome Five for 2.00 scope. This is very OSCILLOSCOPE 30 Rit Includes transformer a handy instrument, problems can be solved in a jiffy with 115V /6OcyPrl. 375VCT /11oma 1320V. with a 5V /3A. 2.SV/3.25A. 6.3V/2.75A Cathode multitude of uses. A few addi- this efficient instrument. The detector Ray tube. Rectifier tube. Condign. Chokes Low &H.V. Supply .. 16.95 tions can increase its uses to cover many can be constructed and installed in Pri trans( top 230V /secil9 %lí2 %lÓ3 %e3V at three 19.93 other things. Most oscilloscopes respond or four hours for less Auto Tnsra GE 115V%I60/170 /150/1.95A 2.95 than five dollars. Llttelfuses 230m11/3AO (L.P. 250) 48 for 1.00 to only a limited range of frequencies, The Condenser kit silvermica & mica condal, 50 exact location on the chassis of .j 00 generally not over 100 kc. Resistor kit BTty &1Watt 50 to 2megohm This range the detector will vary with the make aaatd resistore is sufficient Control kit ABJ; 50 to 2me.ohm: -Ten for 3.50 for many uses but if you of the 'scope. I found it best to put the desire to MIR. order Postage RH orders use it as a signal tracer, the tube on a separate little chassis of its annd 5/a posit.. WOrth 2-7230. Send elee higher frequency 300. Specialists In International Export. School. Col- r.f. is only a blur on own -approximately one and one -half lege & Industrial trade. Money Buk Guarantee. the 'scope. By inserting a detector before by two and one -half inches in size -and the amplifier in the 'scope you can trace bolt it directly to the top of the 'scope "TAB" DEPT. RC2 a modulated signal from antenna post chassis. The detector should be close to 6 -A CHURCH STREET. NEW YORK 6, N. Y. to the speaker. By adding a phone jack the amplifier already in the 'scope. or a small 4 -inch speaker the signals can An infinite- impedance detector was 74 RADIO -CRAFT for FEBRUARY, 1947

www.americanradiohistory.com Order from LAKE! found to work the best of all circuits You'll Make No Mistake! tried. This was followed by a straight OSCILLOSCOPE amplifier to increase the gain on weak RADIO Cabinets & Parts signals. To save space a 6SN7 (twin tri- FOUNDATION KIT ode) tube was used as the combined de- 5 IN(AN De Luxe tector- amplifier. It was found to give z I PHONO good gain in the amplifier (p=20). The Consisting of Case, Chassis, two shelves ` -T -- CABINET infinite- impedance detector will work (right & left), tube shield and bracket,front - Covered In luxuri- well on either large or small input sig- ous, genuine brown Most important is it does not panel, screen leatherette, has de- nals. that brass hard - overload the circuit to which it is window fl-iii, r. war a throughout, frame, han- :t made completely of coupled. It also has low distortion -an plywood with brawn dle, plastic plastic handle, has important fact when a circuit is being window sock- padded lop and be taken bottom. Motor tested for fidelity. Care should et, with 5CP1 x i58 Overall dl mentions 18" L x in constructing this circuit so no distor- Cathode Ray 15" W. x 8' H. Your net price tion will be introduced by it. tube - DE LUXE RECOR and .CCA LAGER B+ Special .... De luxe changer case with ample room for amplifier. H. Overall dimensions 20" L. s 16" W. x 10 OUTPUT TO Sturdily built of W. plywood. de luxe brass hard- 25K 250K ware Inside dimensions: 1555' L. VERTICAL throughout. .1 .25 14yí W. x 9345 H. $12.95 BINDING POST Net -o the 1550 Also blank e cabi walnut opening on front I- following lee. with speaker °DETECTOR° alde. (Note: 75 has ter grill.) 6SN7GT JfI Sy- I. x Soh^ N x 4 0 51.95 2x2 Tube 21.00 -101/4- L x SW H x 5 D 52.75 412 POST Socket for 2x2 Tube .25 ft 1O L x 7" H x Sty,h. D i2.5Ó 7 1.9S tide. H.V. Condenser .5 Mfd 2000 V- Spnker Opening In Center of front KIT, without Cathode Ray tube 11.95 S[RV,ICSMSN -RSTAI LESS Join a ustomer list today Tube shield and bracket only 1.98 Writ* today new 14 catalog .00025 150 IMEG toa for our n u -Ratratedmailing Dept. C SIM SW. SURPLUS TUBES LAKE RADIO SALES CO. and amplifier stage. BARGAIN PRICES 615 W. Randolph Street, Chicago 6, III. Circuit of the detector at fie The figure shows the circuit and meth- All Tubes New and Sold Under , od of hookup. An extra binding post New Tube Guarantee ,. The should be installed on the front of the HOUSE OF A oscilloscope for the input and can be '. . labeled "detector." A 0.1 pf condenser MILLION RADIO PARTS couples the detector grid to this binding post. The cathode of the detector is by- passed only to r.f. but the plate is by- POPULAR KITS passed to both r.f. and a.f. by a 0.1 pf FOR SERVICE AND SOUND MEN condenser between plate and ground. 5CP1 -3.95 884 - .99 6)5GT - 31 5BP1 -4.95 885 -1.05 6L6G -1.20 GOS 6 Assorted Speakers Cones of the detector is coupled The output -4.95 8012 -1.25 6L7 - .99 6-6 & 8" $2.49 a 5BP4 60K Assortment of 60 bakelite knobs to the grid of the amplifier through 5JP1 -9.95 15E -1.25 6SD7 - .65 push on - 2.95 0.1 pi condenser. The output of the 3BPI -3.45 I5R -1.25 6SH7 - .65 100K Assortment of 100 knobs bakelite- wood -push on- and amplifier should be connected through 954 - .89 E-1148 - .69 6517 - .89 set screw 6.72 a 0.25 pf condenser to the vertical in- 9002 - .89 2C26 -1.30 6SN7 - .69 101R Assortment 100-1 watt. ivy watt which is already 1619 - .89 EF-50 - .79 12SK7 - .80 and 1/4 watt Carbon Resistors 2.94 put binding post 1625 .70 VR105-.99 6X4 -.69 200R Assortment 200 1/4 watt insulated coupled to the vertical amplifier in the - resistors 4.96 scope. The detector circuit is turned on 1629 - .89 2050 -1.30 6Y6G - .89 69K Heavy Duty Army Code Key ... .69 1631 - .99 7193 - .99 12A6 - 99 IOC Heavy Duty 10 tube Power Trans- which grounds or un- or off by a switch 1633 - .89 UH50 -3.95 12C8 - .79 former 2.95 grounds both the detector and amplifier bargains available for 1644 - .99 l0Y - .99 12SN7 - .79 Thousands of other cathodes. B+ for the plates is obtained 37 shipment. Catalog on request. 2C40 -2.30 5R4GY- .99 - .49 immediate from any handy suitable high voltage 2C43 -4.25 Lifetime Sound Equipment Co. point under the chassis and the fila- 3C45 -I.40 6X5 - .89 I J66 87 DEPT. 26 TOLEDO 2. OHIO ment is connected in parallel with 100TH -8.25 843 -2.75 12SQ7 -1.05 the other 6.3 volt filaments. An open - -1.35 811 -2.00 34 - .80 801A -2.05 6F8 - .92 30 - .80 ' jack can be installed on the front Do you n circuit 802 -2.05 6SJ7 - .74 83 - .92 panel for the 'phones. The jack can be 803 -7.95 75 - .70 6K7 - .79 BINDING POSTS? coupled through a .05 pf condenser to 805 -5.25 70LJ -1.65 104 - .79 The XL PUSH POST with Ito Action Constant Contact an the common side of the vertical ampli- 813 -7.50 IRS - .79 6B8G - .y9 quick sewesion. on 826 -4.2p¡5, 2X2A 6AC7 - .99 Manu:attwig to All A112111212 Type M fier on-off switch -this is usually the -1.05 at 12e ten. scope now ó5Q7 - .W 3A4 - .79 6AC7 - .84 Bakelite Top Type RI vertical gain control. The is ready for use and with the phones I616 - .99 3Q4 - .89 39.44 - .60 Atlomlaumah200. ALL 35Á5a PPRÖ 717A -1.05 LESUS eSTELL SPXINOp Ñ plugged in any modulated r.f. signal 6AB7 - .84 5Y4 - .63 SPRAY TEST a. NON. 713A .85 b 940 HR. itT fed into the "detector" binding post will 6AB5 -1.05 5Y3 - .63 Manufacturer.D,non Dealen. Liberal 37I A -I.29 6AK5 -130 6K6 - .69 be heard as well as seen. Seeing as well 1960 - .75 .89 6W7 .79 X. L. RADIO LABORATORIES as hearing aids greatly in service work 836 -1.75 6AL5 - - 420 West Meese Ave.. Chime 10. III. -distortion can readily be seen on the 837 -2.10 6C4 - .64 12 SF7 - .69 Low -temperature dry cells. developed 'scope as well as heard in the 'phones. 866 -1.25 6C5 - .59 6SK7 - .79 by the Bureau of Standards during the With the detector off it in no way af- 865 -1.05 6H6CT- .56 6J7 - .80 war, operate excellently at 22 degrees fects the operation of the oscilloscope. Minimum Order on Tubes $2.00 40 The amount of work and the below zero, and can be used at be- small All Prices FOB New York City, N. Y. low. One of the new cells is a methyla- small cost, to the service man, of adding mine hydrochloride- ammonium chloride this circuit will be repaid many many Send for Our FREE Monthly Bulletin type, the other works with calcium times over by the ease and speed with Highbridge Radio-Television chloride and ammonium chloride. The which he can now repair those really latter battery was the more successful, "tough" jobs. The service man will find and Appliance Co. and is adaptable to many commercial countless new uses for his oscilloscope. 340 CANAL STREET NEW YORK 13. N. Y. uses. -Kenneth C. Dike RADIO -CRAFT for FEBRUARY, 1947 75

www.americanradiohistory.com WIRE! WIRE! WIRE! U. S. Army Wire W -110 -B COMMUNICATIONS 5500 ft. Double Strand Per ft. $33.00 ALWAYS ONE INTERESTING ARTICLE Coil Deposit Returnable 6.00 RGU 8 Low Loss Cable - Dear Editor: pure service magazine, and for that rea- Radio Frequency about I think RADIO -CRAFT is one of the son I ttike Service, Radio Service Dealer, 1200' to a coil .... $.041/2 ft. great magazines; there is always at Radio & Appliance Journal and Radio least one article of interest in it. Take Maintenance. I don't expect it to talk Radio & Communication for instance articles like that one on the nothing but Ham lingo, and for that Wire 7/32" Copper 'Scope in October, that keen article on reason the newsdealer sells me QST, the Shielded -Brown rub- Improving Sound Equipment in Novem- Ham Bible (ARRL Handbook) and CQ. ber - Covering about ber, and -for a change-the .December I believe that RADIO-CRAFT is in a 5000' -Coils .. $3.50 1000' story on W2IAY was very good. class of its own -a good solid, middle - AN 16 Aircraft Wire I get a kick out of reading the Com- of- the -road radio and electronics maga- munications Dept, or the Complaint De- zine, and by Also AN 14 $3.50 1000' the beard of the Prophet, . partment, as it sometimes be. may be White and other colors seems to it always thus! I think some of these correspondents V. H. HERNDON, are like the gal who married the poor Odon, Indiana. LYELL HARDWARE CO. guy to improve him, instead of improv- (While RADIO -CRAFT is pleased and Pe O. BOX 5 ROCHESTER II, N. Y., ing themselves, which is why I read happy to receive letters like the above, RADIO -CRAFT (from Volume I, No. 1). please keep on sending your kicks to AMAZING NEW I don't expect RADIO-CRAFT to be a our "Complaint Department. " -Editor) t Pocket or Perse sire RADIO! SMALL AS A PACK OF CM- SERVICEMEN SELL ,+ SHOULD ounces-Beautiful black chrome Come to the famous plastic Eacase. s new born Dear Editor: crystal HI aPlwo . Woe.ll a aÌ l ins."oad Usual receives As a new hand at the game, I have COYNE caeq DUtouie aerial `J wires. the following to offer on the question: TO PLAT when used according to Inetruc- "Why does a radio (service) man want TRAINING SHOPS dons sent with each radio! You can to sell sets ?" where yoli'Iearn by doing oeluse bin., Inbed, etc®loIa of fun-real entertainment! I opened up shop this year (1946) (cash, money ppa Send Only 5100 °$á9order,us delivery feee, with the sole idea of service and service or $3.99 for stpald delivery. Com- plarrivalote shown dReady te Play wwith self contained per- TFOR ml phone. only. After turning out 600 sets in three - For Gifts -children ill love It-grown- RADIO ups An exceptional value -order yours and enjoy months, I want more than ever to sell many good radio programs coming! Don't be without your Pa -Kette Radio another day! (All foreign or- radios! ELECTRONICS ders 35.00 U.S. cash.) Pa -Kette Electric Co. Dept. RC -2 Kearney, Nebraska Each salesman has his particular IN Rs FEW WEEKS item or product to sell. Also he knows the game and is a qualified (not an Prepare For A Good Job Now With PEN -OSCIL -LITE "authorized ") man in his particular A Lifetime Future I Extremely convenient teat oscillator for all radio Trained Radio- Electronics men needed now. They Servicing; Small as Self field. A good baker knows bread; a will be needed too in the years to come. Don't be Range from 700 audio tao caught napping. Get a Radio training now and be 600 Output good furniture man knows. furniture. ready. ow incoC1tcost -Veed Write Learn by.Doing. Free employment service Information. by i for for life after graduation. Many earn while learning Why should not a good radio man know If you are short of money. ask about my Student TEST EQUIPMENT radio? Finance Plan. Now added Training in Industrial Electronics and Electric Refrigeration. We are 38 Argyle Ave. Buffalo 9, N. Y. also equipped to train those who qualify under G. I. But here's the story I hear every day Bill. We also have facilities for men with physical disabilities whether due to war or other causes. Fill from set owners: "When I bought that in and mail coupon for details. ELECTRONIC VOLT - OHMMETER console, I thought I was buying a good SEND COUPON FOR FULL DETAILS 110 AC radio. Instead I bought a good box." VOLTS 20 RANGES B. W. COOKE, Dir. Radio.Electronice Div. 51185 0/5/10/50/100/500 /1000/5000 volts DC and This is true. If the customer wants a COYNE ELECTRICAL SCHOOL AC. 0- 1,000.000,000 ohms in sir over- 600 S. 27-811, 12. ILA lapping ranges. SeendUv1ty: good shortwave radio, the furniture Paulina St., Dept. Chicago POSTPAID over MILLION Send Big Free Book; also details about Coyne Part- OIIDIB Per YOUT on 5 volt nags. man sells-him a large console. A radio Time Employment and Student Finance Plan. Complete kit includes all component parta, ss,, Send G. I. Bulletin Physical Disability enameledto man would recommend a communi- anelEasyÌ aueled wired.iedbeautifully ps md cations set, something the furniture NAME Special slideback circuit developed during war by AGE scientist at the California Institute or Technology gives man, druggist or other "radio amazing sensitivity and flexibility while completely elim- dealer" ADDRESS inating necessity of batteries and ,pensive ter. Each never of! instrument is individually calibrated. Dial scale Over heard nine inches long! More once, I CITY STATE In addition lorm the Usual volt-ohm function.. than after had picked up this instrument as ymea HET OSCILLATOR. AVC. AFC. TRUE GRID BIAS AT THE a big 'box, the customer has come in GRID. BIAS CELLS without affecting the circuit. Measures the exact leakage resistance of INSULATION. TUBES. while I had the "works" on the bench, CONDENSERS. It can be used with s signal generator for SIGNAL TRACING. and refused to believe that the midget a GOLD MINE of chassis was his radio. They STERLING ELECTRONIC COMPANY buy their SURPLUS PARTS 168 N. Sierra Bonita Ave.. Dept 2. Peredena s. Calif. sets on a basis of: "The bigger the box, the better the receiver," and feel swin- for RADIO REPAIRMEN YOUR ELECTRIC DRILL dled when they see "that little thing on AMATEURS AND EXPERIMENTERS the bench." You can explain to them Has 100 Other Uses that the big box acts as a baffle and when used with KJax attachments $2.00 improves reproduction but they still feel I of RADIO PARTS onlr METAL SAWING . . . SHEARING 12 ils. RIVETING ATTCHMENTS (correctly) that a "bigger and better" Ask your Hardware deafer or write for illustrated circular radio would be even more of a help to get a better output. Relays - Condensers - Resistors K-JAX, 2600 Canton St., Dallas, Texas Transformers - Coils - Hardware It takes a radio man to sell radios. Wire, etc., etc. British trains are experimenting with As one radio man to all you others, I Send 2.00 cash, cheek or M.O., today! (Pay small radar to cut down time lost in fog. The say: "Let's stop the `box' racket and express charges on receipt.) Write for Radio Parts Catalog. work is being carried on cooperatively sell the public radios, the kind of radios by the country's four largest railroads, they need and require!" ELECTRONIC PARTS, Inc. and radar -equipped trains are already OTIS H. WYMAN, 622 W. Randolph St. Dept. C2 Chicago 6, Ill. making test runs. Collinsville, Ill. 76 RADIO -CRAFT for FEBRUARY, 1947

www.americanradiohistory.com SMALL RECORDING STUDIO (Continued from page 52) A RADIO KIT OF NOTABLE QUALITY AND VALUE! plifier consists of two input circuits ar- 33 1/3 revolutions per minute. The re- ranged as a mixer, so that individual sponse can be varied to provide the Our model R -3 is a gain control of each circuit is possible. proper conditions for recording FM, 3 -tube receiver kit voice, special effects of the regenerative The mixer is followed by two voltage AM, and for any Type. This receiver amplifier stages and a push -pull triode required. is the 110 volt type output amplifier. Negative feedback is The last group of controls includes end operates at a applied to the cathode circuit of the. the cutter switches and power switches. frequency of 550 first voltage amplifier stage. See Fig. 2. One switch applies the amplifier output Kc to 1500 Kc by means of a plug in coil. Filter networks are so inserted in alternately to a playback speaker or the The power supply is self- contained in the the feedback net that the low- and high - cutter. There is another to give either receiver thus eliminating the need for a a constant -velocity or constant- ampli- separate power pack. This kit comes to frequency response may be varied inde- you pendently. Note the method of connect- tude cutting characteristic. The main completely disassembled. power switch and motor power switch ing the mixer plate circuits so that the ALSO AVAILABLE loading of the tubes on each other is complete the group. KIT MODEL 5.55 ... a 5 -tube superhetero- negligible. The speaker and monitor Located conveniently are the jacks local dyne radio kit, comes complete including phones are driven from the output for the microphone and the ear- tubes, bakeiite cabinet and instructions, transformer, which is of the high -fidel- phones. A 0 -1 milliammeter is mounted ready for assembly. ity type. The crystal cutter is driven in the top surface of the cabinet to indi- through a pair of 2-p1 condensers dicate cutting level and is plainly marked KIT MODEL 56X ... a 6 -tube, 2 -band receiver rectly 6B4G's. as to the maximum cutting level. A kit, equipped for either 110 or 220 volts, from the plates of the AC or DC . . covers the following ranges: To reduce the hum level to the vanish- 1N34 germanium crystal diode is used meter rectifier, frequency 550 Kc- 1600 Kc, 6-16 Mc. This kit is fur- ing point, all the heaters except the as the as its nished complete, reedy for assembly. 6B4G's are supplied from a 6 -volt d.c. response is absolutely flat over the source. This d.c. is obtained from a audible range and far beyond. KIT MODEL RP -55 ... a combination radio selenium rectifier through a heater fil- All the external connections to the and phono kit. (5 -tube superheterodyne ter circuit consisting of a filament cabinet are made by means of a ter- -.Idle), 5" Alnico V Speaker, Astatic L-72 minal plate which includes the radio, yack -up, beautiful walnut finish cabinet, transformer and two 1000 -d filter con- ready for assembly. densers. mike, and remote pickup inputs, speaker output, 117 -v input, and filament and (ALL KITS SUPPLIED The amplifier gain is approximately four -stage t.r.f. 100 db which is adequate for all but the plate voltages for the LESS WIRE & SOLDER) lowest level microphones. A AM tuner. All the wiring from am- pre-am- plate is Write for Dwariptive Catalog M plifier is used when additional gain is plifier to panel and terminal necessary. completely shielded to reduce hum pickup. With the gain controls wide open RADIO KITS COMPANY The amplifier is mounted in the cab- /and the bass ¡boost control in the maxi- 120 Cedar St., New York 6, N. Y. inet, with a sloping metal panel added mum position, the hum is inaudible. to mount the recording controls. These There is no pattern on the recordings include the two gain controls, together from motor vibration or from any other with their input selectors. One input is source, and the rumble of the turntable BE YOUR OWN BOSS! used for AM, FM recording, and play- is below the scratch level of a profes- back from either the Brush pickup or MAKE MORE MONEY sional quality recording disc which has In "CASH IN you the dynamic pickup, mounted on the $1.00 been cut with a new sapphire. VALUE now get THE real auxiliary 12 -inch Presto moneymakers - doe - turntable. The The speaker system consists of a Jen- ens of profitable tasted other input is used for microphone work mall order plane, con - sen 14 -inch auditorium type L woofer fldonttal business se- and can be switched from a remote crets, dozens of DM- and a Jensen type C tweeter mounted 25° Mall tested formulas. mike to a local one so that the recordist in a home -made bass reflex baffle. A wceeeeful totted 40.000 schemes - actual ex- may make necessary; announcements. photograph of this speaker appeared periencee of men who WORDS have started on a shoe- The next control group includes the in the November (1946) issue of RADio- string -with lass than IN $10 capital. 250 bass compensation control, the high-fre- CRAF r, in which it was described com- may postpaid. Send quency selector and the high- frequency pletely. TEXT U. S. stamps. money order, or eosin. compensation control. There is a wide In the next installment of this series, Mr. Money Back choice of high frequency boost points Hoadley will tell how to make a record. Succeed- Guarantee which allow compensation of the high ing articles will deal with electrical considera- tions recording troubles and other features of NATIONAL PLANS COMPANY loss in recording toward the center at sound recording. Box 26RF, Ansonia Station New York 23. N. Y.

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RADIO -CRAFT for FEBRUARY. 1947 77

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s6gettrra8s Allied Radio Corp. ' 48 National Radio Institute I George Brodsky Advertising Van Sant Dugdale & Co. GOOD DISCOUNTS Almo Radio Co. 60 National Schools 13 ON ALL TUBES E. L. Brown Co. The Mayers Co. American ales Co, 70, 71 National Union Radio Corp. 2 786, 7C6, 7G7, 58, IDS, 2A6, 12K7, 1497, ILB4, Amplifier corporation of America 65 Hutchins Advertising Co. ILC6, SZ4, 788, 7C5, 84, 12Z3, ILA6, 43, 47, Sternfield- Godley, Inc. New York Technical Institute of N. J. 42, 43 Audel Publishers 58 Schwab & Beatty, Inc. 25Z5, 321.7, 57, 12A8, 6F5, 50Y6, 35Z3, 35, 697, Grant & Wadsworth Newark Electric Co., Inc. 6 0Z4, 11726, 7M, 701.7, 787. 6A8, 50A5, 2A5, Ball Telephone Labs Inside Back Cover The Charles Brunelle Co. 59, ILN5, 14R7, 7C6, etc. N. W. Ayer & Son Niagara Radio Supply 71 Brooks, George & Associates 69 Burke & All Tubes New and Guaranteed. Wayburne Advertising Agency The Schram Advertising Co. Oelrich Publications 68 Write for Catalog -We Ship Anywhere. Buffalo Radio Supply 57 Sander Rodkin Advertising Agency International Advertising Agency Olson Radio Warehouse 45 Burstein- Applebee Co, 71 Jessop Advertising-Company RADIO Frank E. Whalen Advertising Co. Opportunity Adlets 78 COMMERCIAL 8, MASS. C. F. Cannon Co. 69 Pa -Keita Radio Co. 76 36 BRATTLE ST.. BOSTON M. J. Werner Adv. Arrow Advertising Agency Capitol Radio Eng. Inst, 49 Progressive Electronics Co 69 Henry J. Kaufman & Associates Radcraft Publications 63 Chief Electronics 78 Radio Dealers' Supply Co. 69 Graphic Company of Advertising Burke & Wayburne Advertising Agency Cleveland Institute bf Radio Electronics 47, 55 Radio Electric Service Co. 40 THE YEAR'S BIGGEST OFFER Kenneth Kolpein 'David Zibman Adv. Commercial Radio 78 Radio Equipment Co, 77 Goulston Co., Inc. Radio-Experts 70 10 lb. Rodio Parts Assortment Communications Equipment Co. 12 Radio Kits Co. 77 Borough Advertising Co. Hamburger Agency Concord Radio Corp.- 46 Radio Parts Co. 51 A "find" for the radio serviceman. E. H. Brown Advertising Agency Sydney S. Lovitt Adv. Hundreds of valuable radio parts, Coyne Electrical School 59, 70 Radio Publications 64 Phil Gordon Advertising Agency Redolek Company 67 including coils, resistors, trimmer Coyne Electrical School 76 Turner Co.

condenser e, lugs, transformers, McJunkin Advertising Agency Randolph Radio Stores - 78 switches, hardware, etc. Crabtree Wholesale Radio 79 Reed Manufacturing Co. 79 DeForeif s Training Institute II Rosicruscians, The 70 Only $1.95 Lauesen & Salomon Richard Jorgensen Dow Radio 79 Writs for radio puts circular Electronic Parts, Inc, 69, 76 Campbell & eynolds Esse Radio Co, 14, 15 RADIO SCHOOL DIRECTORY-See Page 80 RANDOLPH RADIO STORES Gary A. Ruben Advertising Feller Engineering Co, 60 609 W. Randolph St. Chicago 6, cal. George Brodsky Advertising American Radio Institute General Cement Mfg. Co. 51 Sternfield -Godley, Inc. Sander Rodkin Advertising Agency Baltimore Technical Institute G I Electronic Distributing Co, 54 Benson Radio Institute SERVICE Bass & Weber Co., Inc. Gunn -Mears Advertising Agency MEN! General Test Equipment Co, 76 Candler System Co. RCA Radiotron Sylvania Suzanne Heyman Adv. Tunnel Raytheon Rand -Ries Adv., Inc. Tubes, Parte Harrison Radio Co. 53 Commercial Radio Institute i Equipment Altomari Advertising Agency Write our latest Lincoln Engineering School for bulletin, Dept. CI Hershel Radio Co. 8 Hugh Allen Advertising Buchanan- Thomas Adv. Distributors of ' RADIO EQUIPMENT Ill hbrldge Radio -Television and App. Co 75 Melville Radio Institute Burke and Wayburne Advertising Agency Seidel) Adv. Hollander Radio Supply Co. 67 RCA Institutes Turner Advertising Agency United Radio Television 104 MAIN STREET, POUGHKEEPSIE, N. Y Howard Supply Co. 69 Western Radio Television Institute The Square Deal Supply House Hudson Specialties 64 Y.M.C.A. Instructograph Co. 79 Turner Advertising Agency International Resistance Company 41 John Falkner Ardnt & Co., Inc. Sams & Co., Inc., Howard W. 3 K -Jax 76 Aitken -Kynett Co. OPPORTUNITY AD-LETS Lafayette Radio 52 Sanco Radio, Inc. 69 Advertisements in this section cost 20 cents a word Reiss Advertising Agency Simpson Electric Co. Inside Front Cover for each Insertion. Name, address and initials must Lake Radio Sales Co. 75- Kreicker & Heloen. Inc. be included at the above rate. Carts should accom- Sander Rodkin Advertising Agency Sprague Products Co. 16 classified advertisements by annimredit artising Leeds Radio Co. 64 Harry P. Bridge Co. for le than ten words accepted. Ten percent dis- Bass & Webber Co., Inc. Sprayberry Academy of Radio 9 count six issues, twenty percent for twelve Issuer. LeJay Mfg. Co. 69 Harry P. Bridge Co. Objectionable or misleading advertisements not ac- Frizzell Advertising Agency Stahl, Michael 48 cepted. Advertisements for March. 1947. issue must Leotone Radio Corp. 59 Bass & Weber Co., Inc. us not later than January 29, reach 1947. 79 RadieCraft 25 W. B'way New York 7. N. Y. Alfbmari Advertising Agency Standard Electronic Did, Co. Liberty Sales Co. 62 Sterling Electronic Co. 74 Sternfield- Godfrey Inc. Superior Instruments Corp. 39 Lifetime Sound Equipment Co. 75 Bess & Weber Co., Inc. CORRESPONDENCE COURSES AND SELF- TNSTRUC- The Miller Agency Supreme Publications 61 tion books slightly used. Sold. Rented. Exchanged. Ail Lyell Co. Henry H. Te litr, Advertising subject.. Satisfaction guaranteed. Cash paid for used Hardware 76 courses. Complete information and 100 -page illustrated McGraw -Hill Book Company 73 Sylvania Electric Products, Inc, 7 bargain catalog Freel Write- Nelson Co.. Dept. 39, Chi- McMurdo Silver Co., Inc. 54, 65 Newell -Emmett Co. cago 5, III. Edward Owen & Co. "TAB" Technical Apparatus Bldrs. 74 Mallory 6 Co., P.R Back Cover Bass & Weber Co., Inc. WE REPAIR ALL TYPES OF ELECTRICAL INSTRU- Aitkin -Kynett Company Trutone Products Co. a 68 Haselton Instrument ments, tube checkers and analyzers. Maritime Switchboard 72 Julius J. Rowen Company Co. (Electric Meter Laboratory), 140 Liberty Street, New York. N. Y. Telephone- BArclay 7-4239. Metropolitan Electronic & Inst. Co. 56 Turner Company 44 Bass & Weber Co., Inc. W. D. Lyon Co. MAGAZINES (BACK DATED) -FOREIGN. DOMESTIC. Murray Hill Books, Inc. 4, 5 Variety Electric Co. 66. arts. Books, booklets. subscriptions. pin -ups. etc. Cata- Harry P. Bridge Advertising Agency Bass & Webber Co., Inc. log 10c (refunded). Cicerone's. 863 First Ave.. New National Plans Institute 77 Wright, Inc. 73 17. N. York Y. National Radio Distributors 73 Kay Advertising Agency Laboratories 75 AMATEUR RADIO LICENSES. COMPLETE CODE Burke & Wayburne Advertising Agency XL Radio and theory preparation for passing amateur radio examinations. Home study and resident courser. American Radio Institute. 101 West 83rd Street. New York City. See our ad on page 80. CARBON ARC SOLDERING SCRATCH REMOVER S'REE WHOLESALE BULLETIN. TUBES. PARTS. I find that good soldering carbons can Plastic materials such as flash- Bargain prices. Renshaw Radio Supply, 3913 Pelaran City, Kansas City, Kansas. be made from the arc carbons used in light lenses and radio dials often be- movie projectors. These carbons are come scratched and soon take on the WANTED COPIES OF "MODERN ELECTRICR" AND "Electrical Experimenter." State price. Box GT. % Radio - copper sheathed and the leads may be appearance of ground glass. The Craft. soldered directly to this coating. scratches may be remóved by buffing 'TITRE RECORDER READ- RECORDS. REPRODUCES. The negative carbon is the surface with a piece of soft felt that erases. Highest Quality laboratory instrument. Brush preferable be- made for Government. Value $12.50. Our price $2.50 cause it burns down to a sharp point. has been coated with a film of jeweler's with order. Redioco 111OR Marshall Bldg., Cleveland. Ohio." ' Used carbons may be obtained from the rouge. Glass also may be polished by ' ALL RIDER MANUALS WANTED. WRITE, LOPES. projectión room of almost any movie this method, but the process is a long 780 E. 214, New York City. theatre. and tedious one. BARGAIN -CONDENSER KITS 15 ASS'T. MICAS N. SCHREDMAN, HARRY A. NICKERSON, .00005 to .001 -2Tí0 -500 V 81.00. Reliable Radio, P.O. Box 132. Merchentrlll. N. J. Bronx, N. Y. Dorchester, Mass. 78 RADIO -C RAFT for FEBRUARY, 1947

www.americanradiohistory.com ö1111MI1II'-` n ,l,I EASY TO LEARN CODE EI B i: K EW S It Is easy to learn or increase speed . with an Instructograph Code Teacher. Affords the quickest and most practical method yet developed. For be- RADAR, WHAT IT IS, by John F. ginner. or advanced s t u d e n te. RADIO FAMILIES -U.S.A. Compiled Available tapes from beginner's and published by the Broadcast Meas- Rider and G. C. Baxter Rowe. Published alphabet to typical messages on Ill Rider Publisher, Inc. Flexible subjects. Speed range 5 to 40 WPM. urement Bureau. Flexible fiber covers, by John F. Always ready-no OHM. spiral wire binding, 81/2 by 11 inches, paper covers, 81/2 x11 inches, 72 pages. pages Price $1.00. ENDORSED BY THOUSANDS! 250 pages (publisher's statement, The Instructograph Code Teacher $5.00. literally the place not numbered). Price This simply written and well- illus- tructoorr (anyone to learn and master code without - trated book is prepared for the layman Thousands Ñ "a.acquired the' code "° athe Instructograph System. A compilation of the number of fam- or student with no previous knowledge Write today for convenient rental and purchase plans. ilies owning radios in each county in of radio or electronic fundamentals- the United States, this book is divided nor is this knowledge required -for the INSTRUCTOGRAPH COMPANY into three sections. The first compares work gives a fairly complete picture of 4701 Sheridan Rd., Dept RC, Chicago 40, III. the total number of families with the radar that can be understood by ele- number of radio families in each county. mentary students without resorting to in the United States, and is divided by mathematics or physics. ROTA -BASE all cities of NEW HANDY LAB. DIAL. Simply hum the ovable states. The second indexes Its eight chapters, illustrated with dial to the tube number desired on the ROTA -BASE and complete correctrect connections are instantly indi- 10,000 or more population, plus all cities photographs, diagrams, and clever car- cated on the "prong" diagram. Filament. grid, plate. types given. of under 10,000 which have a radio sta- toons, utilize simple analogies to explain No more valuable ptime los00o engthy reading or thumbing of pages. ROTA-BASE actually gives tion. List is alphabetical by city. The the fundamentals, development, and ap- "prong pitture of the action. PRICE NOW ONLY Postage p plus third section shows the population and plications of radar. Because of the IMoney ack if not delightfully pleased. radio population of metropolitan dis- simple presentation, this book will pro- REED MFG. CO. a',.:;g:».nühr. tricts. vide interesting reading for the scien- A Canadian supplement shows radio tifically minded layman. ownership by counties, or by census sub- divisions where counties do not exist. ELECTRIC MOTOR REPAIR, by 2vaty Percentages are given in all cases, Robert Rosenberg. Published by Murray aS'ulyny and show that radio ownership ranges Hill Books, Inc. Flexible fiber covers, from 91.1 in one county in Massachu- 61/2 x9 inches, special binding, 308 pages 4Llacttonic Azad of text and 243 separate pages of illus- FOR THE- setts through 50 percent in an Alabama RADIO SERVICE MAN county to 34.3 in one county of Quebec. trations. Price $5.00. D by This book, which can serve equally STUDENT Although all figures were secured El ER statistical methods and therefore do not well as a text, laboratory workbook, or NDUSTR AL reflect local variations from the general handbook on electrical motor repair, will WRITE FOR ILLUSTRATED PRICE LIST pattern, the overall picture given by be useful to motor repairmen as well as these percentages should be very useful students and .vocational instructors. GP RABIREE' not only to the radio advertiser but to Step -by -step servicing and trouble- the general businessman surveying eco- shooting procedure is presented on all WHOLESALE RADIO: nomic and cultural conditions in any types hnd sizes of a.c. and d.c. motors, DALLAS sloe Ross AVE. TEXAS of the areas covered by the report. (Continued on page 80) ORDER NOW Signal Corps 1 -222A Signal Generator 8 to 15, 150 to 230 MC $69.95 300 Ohm Amphenol Twin Lead, per 100 ft 2.90 75 Ohm Arophenol Twin Lead. per 100 ft 2.00 P23 Army Head Set. 8000 Ohm with 5 ft Cord and plug 2.95 8 Gang 410 MMFD. Per Section Condenser. Es- collent Quality 2.95 BC3I2 Army Receiver 59.95 BC 312 converted for 110 VAC 79.95 National ACH Dials 3.00 4 MFD 800 Volt 011fllled condenser. standard can mounting 1.59 IAN type 2c40 Lighthouse tube. new ln cartons 4.49 Complete line M RCA. TALYOR, 0E. and EIMAC Tubes. Write ye Your Needs In Any Nam Equipment. DOW RADIO ' 1759 E. PASADENA 4. CALIF. r Pasadena Phone- SYmmoro 3-119e Loa Angeles Phone -RYan 16653

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Radio propagation predictions are again available to the public, the CRPL -D series, "Basic Radio Propaga- tion Predictions" is issued monthly, copies being obtainable from the Su- perintendent of Documents of the Gov- ernment Printing Office for 15 cents each or $1.50 per year. RADIO -CRAFT for FEBRUARY. 1947 79

www.americanradiohistory.com reference guide to repair and trouble- shooting methods for that type of motor. RADIO SCHOOL DIRECTORY Over 900 drawings and photographs illustrate the many steps and processes encountered in motor repairing. PREPARE NOW FOR SKILLED JOBS IN RADIO AND ELECTRONICS A duo -spiral binding divides the book effectively into two parts with text in one part and illustrations in the other. Each part is used as a separate book so that illustrations may be kept in INTENSIVE COURSES -Thorough, technical view as the text is being studied. education for progressive men and women. 1. RADIO TECHNICIAN -The MRI General licensed by the State of New York HAM STATION FROM Course. Includes F.M. & Television. Prepares For FCC r SURPLUS Broadcast license'. I 2. RADIO & TELEVISION SERVICING --Pre. MELVILLE RADIO INSTITUTE (Continued from. page 30) pares For employment as Repairman on Stand. 45 West 45th St., New York 19, E> and Broadcast, F.M. & Television Receivers. N. Y. GENTLEMEN: 3. RADIO COMMUNICATIONS- Prepares for RC 'normal a.v.c. operation is permitted. FCC Operators' license Leads to position ós Send me FREE Closing the switch removes Merchant Marine or Flight ,Radio Officer; Corn. Information about this voltage. mercial Operator. your school. The amateur experimenter may make 4. FUNDAMENTAL RADIO MATHEMATICS other. improvements such The MRI Preparatory as adding a Course. Required pre - Name training for students lacking o basic mathe- vernier dial or connecting the output matical background. of the 6B8 -G amplifier to the input of Address MELVILLE RADIO INSTITUTE the interphone amplifier. A loudspeaker may be connected into the plate 45 W. 45th Sf., N. Y. 19, BR 9 -5080 circuit of 6V6 -G "WI» Raille Scheel Afie t.d ,gy Reale .Mere" L the power amplifier V8B. The over -all gain of the set may be improved by reducing the value of the CORRESPONDENCE COURSES IN cathode bias resistors in the M. ampli- Radio Men Needed RADIOardELECTRICAL ENGINEERING fiers, Under no conditions should these ELECTRICAL ENGINEERING x od er , be reduced to the point of instability. tlr tr Bern The Finest In Radio Training Course. yourself low S simplified Quickly. Train for well -paid positions in Radio En- RADIO ENGINEERING E °ne apGr. in tl+ man re

AMERICAN RADIO INSTITUTE BREAK 101 West 63rd St.. New York 23. N. Y. Rb LI Bi. APPROVED UNDER al BILL OF RIGHTS. LIOA RCA INSTITUTES, Inc. AVC UNE TO R8B Offer thorough training LEARN courses in all technical phases of R.F. GAIN AVE SNL Radio and Television RADIO -TELEVISION -FM DAYS -EVENINGS 'WEEKLY RATES Complete course's in all phases given in both 20K VETERANS: RCA Institutes Is approved day and evening classes. Fig. 4- .A,v.C. and r.f....gdin control details. under G. I. BIII of Rights Veterans accepted Fer Free Catalog Write Dept. RC -47 under G.I. bill RCA INSTITUTES, Inc. United Radio Television Institute A Radio Corporation of America Service 225 Halsey Street Newark 2, N. J. THE RADIO PEN IN EUROPE 75 VARICK STREET NEW YORK 13. N. Y. (Continued front page 71) COMMERCIAL RADIO INSTITUTE A radio training center for 'America only is capable of making tw. nty-six years. something exceptional, that for many, De man. learn how so asna and news from America is as true as words RESIDENT COURSES ONLY from the Gospel! of me01fora Jobs. Good "pay{ Broadcast. Service. Aeronautical. Television and Marine interesting' adv...., work. tes at home quick- 4 tMaarspb7 cl now forming. Literature upon request ly famous system. "A -tube radio in a Fountain Pen! Veteran training Classes now forming for mid -year for TREE Why not, if the Pen is. American! term. Feb. let. Entrance exam. Jan. 13. CANDLER Dept. «EMCO. Dept. C. 38 West Biddle St., Baltimore 1. Md. 3-11, 2. Den8 1. "Paris in a glass Bottle! Why not, enumm Blmmmolu IIIIIIIIIIInnoni III111111III1111111IIIIIIIIIIIIOIIIIIIIIIIE if the bottle is American!" RADIO COURSES Another technical magazine Servicing, Broadcast Engineering. Commercial Operating, which LEARN RAPID Television joined the ranks of those who were INDIVIDUAL LABORATORY WDRKI -LEARN W DOING! RADIO SERVICING DAY AND EVENING CLASSES taken in was the Italian technical maga- Send for Free Information: "3 Ways to Learn Approved by the Maryland State Dessinent of Education zine l'Antenna. In their issue of Sep- = Radio.^ Approved (or Training Veterans. and the Veterans Administration FREE TO VETS-TEXTBOOKS, TOOLS. TEST SET tember, 1946, they reprinted the article WESTERN RADIO INSTITUTE E. Write for Bulletin and even went to the BALTIMORE trouble to redraw 1457 Glenarm. Denver 2. Colo. TECHNICAL INSTITUTE the April Fool diagram 425 Eutaw Place -Dept. C. Baltimore 17, Marl d solemnly. mmmunmm11mnmuunnmuunmuuuuniguumuuuIMIMMnmR 7 L'Antenna started the article by stat- BOOK REVIEWS ing that the Radio Pen was manufac- RADIO COURSES tured by "Utis Electronic Corporation" RADIO OPERATING CODE (Continued from page 79) RADIO SERVICING - ELECTRONICS -without stopping to think what the REFRIGERATION SERVICING word meant. Utis is a character from Personal Counselling Services for Veterans selsyns or synchros, the old Greek mythology. The word Write for Latest and electronic Trade & Technical Catalog motor control units. Each type of motor means, literally- Nobody! Y.M.C.A. TRADE & TECHNICAL SCHOOLS is w. even Street Na. York alb discussed at length in a separate Evidently RADIO-CRAFT'S April Fool section that is concluded with a quick- joke has come home to roost! 80 Printed In the U.S.A. RADIO -CRAFT for FEBRUARY, 1947

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Ta Alexander Graham Bell could look several hundred yards by waves of vis- microwave radio. It was developed by at the microwave antenna in the illus- ible light, electromagnetic waves of Bell Telephone Laboratories for mili- tration, how quickly his mind would high frequency. tary communication and found impor- go back to his own experiments, 67 Bell's early experiment with the par- tant use in the European theater. In years agol abolic antenna and the use of light the Bell System it is giving service be- For in 188o the inventor of the tele- beams as carriers was for many years tween places on the mainland and phone had another new idea. Speech only a scientific novelty. His idea was nearby islands and soon such beams could be carried by electric wires, as far ahead of its time. will be put to work in the radio relay. Bell had demonstrated to the world. Sixty years later communication by In retrospect, Bell's experiment illus- Could it be carried also by a light beam? means of a beam of radiation was trates once again the inquiring spirit He got together apparatus -a tele- achieved in a new form - beamed of the Bell System. phone transmitter, a parabolic reflector, a selenium cell connected to hand - phones -and "threw" a voice across BELL TELEPHONE LABORATORIES

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