April 1961 37¢ "220".. . band for big GONSET gam• ••• COMMUNICATOR IV·220
220 megacycles .. . long regarded as a band of promise noise figure of 3 to 5-exceptional for equipment of ' " where big antenna gain comes easy. A quarter-wave this ge nera l type . Receiver is contin uously tunable but antenna is only a foot long and good ground planes also includes provisions for spot frequen cy reception includin g the top of a car-are ea sy to come by. Simple on one crystal controlled frequen cy.(AC-O requirement .l beams and even complex arrays of hi gh gain are con veniently small in size- easy to put together and get Power input to 6360 final amplifier is 20 watts, ampli up into the air. Here's a band where antenna expert tude modulated by p.p 6805's. Transm itter is crystal mentat ion can run rampant. Multi·element yagi 's .. . controlled, has 6 crystal positions. Dual power supp ly stacked colinears .•• sleeve types •. . bed springs . .• is built-in, operated from 12V OC /lIIV AC , is equally log-periodic types .. helicals. The band has OX possibil well suited to fixed station or mobile operation . ities too . Remember KH6UK to W6NlZ? CoO Models, Model 3351 is certified to OCOM as meet In Gonset Communicator rv·220 you have ready-to ing applicable specifications, qualifies for matching operate " packaged" equipment that offers power to funds when furnished with Model 3361 CoO Kit. really go places on this fine band. On the intake side 50 - an exce llent triple conversion receiver having sen Communicator IY-220 .... #3351 ... _$394 sitivity of 1 microvolt for 10 db S+N /N ratio. And a (l ess mic rophone, crystals.)
G 0 N 5 E T Diuision a' Young Spring & Wire Corporation 10 1 $OUTH .. ... I N I T . • • U ...... N K. c a. L I FO " N l a.
EXPORT SALES: WESTREX C ORP • • 111 EIGHTH AVE., NEW YORK 11. N.Y. ANNOUNCES THE NEW 200'7 BROAD-BAND Exciter-Tra nsm itter
NEW FEATURES IN THE 200V Amateur net. •.. $ 7 9 5
NEW! Sillcon rectifier power supply. Better regulation. Less heat. Htgher voltage. 200 walls PEP input on SSB. NEW! Frame grtd (6EH7-6EJ7) mixers. Extremely high gainLess heat. Unwanted mixer products down in excess or 50 DB. NEW! Temperature compensated crystal oscillator circuits for ex tr-eme, long term stability. NEW! Increased mike pre-amplifier gain. Compensates for weak voices or low output microphones. NEW! Smooth as silk two speed tuning knob with 5 KC per turn vernier tuning ratio.
COMPLETELY BROAD-BANDED. You tune only the VFO . Inher ently matches output impedances of 50-72 ohms. PLUS COMPLETE BAND COVERAGE. ALL 01 the 80-40-20-15-10 meter THESE bands, plus generous overlap and position for extra band . ORIGINAL INPUT 175 watts on CWo FSK and PM. 100 watts on AM. FEATURES "TAILORED" audio liIter-Audio limiter. ADJUSTABLE POWER OUTPUT control. 2" MONITORING SCOPE. CALIBRATION ACCURACY belter than I KC. UNWANTED SIDEBAND SUPPRESSION 50 DB. CARRIER SUPPRESSION at least 50 DB. HARMONICS down in excess 01 50 DB. THERE IS Third order DISTORTION PRODUCTS down in excess 01 NOTHING 40 DB. FINER THAN EASIER TO OPERATE THAN EVER I Choice 01 USB-LSB-AM-PM THE CW-FSK at the lllp 01 a switch. Perlected VOX, PTT, CW breakln 200V -4 ways to key.
Available soon - write for literature.
• 175 WATTS Al\A~'IE~1:r AM-CW CD out- \uce JOore c kl du\ation 50 MC-54 MC 144 MC-148 MC to prol _1 hig\lCr tl\(h'er pres- tanU .y OI ' j j . w ith Automot ic; Modulation Control a nd Clipper-Filter pu than an mercta Y Circuitry copoble of producing more usable " fo lk power" power " an able coro f "[rans· sent\)' a . teur \'11 thcm many kil ow att ri g s. built arna (3.5 Me-30 Me and 220 Me adopters availab le soon) ,Hitter
~tesome of the many features found only in this outstanding new VHF Transmitter: • High Level Plate and Screen Modu • Two Unit Construction with Remote lation Modulator and Power Supply Con. • Highly Efficient Type 7034 Final serves Space at Operating Position Amplifier • Attractive Styling • Self-Contained Stable VFO Amateur Net Price: Only $559_ Com • Built-In Automatic Modulation Con pletely wired and tested with all tubes, trol Modulator, Power Supply, VFO, cahles, • Simple Band Switching and Tune-Up etc.
~6M.Matching VHF RECEIVER!
"LABORATOR I ES RT. 53, MT. TABOR, N. J . • OAkwood 7-6600
2 73 MAGAZINE 73 Magazine April 1961 Vol. 1, No.7 1379 East 15th Street Brooklyn 30, N. Y. Table of Contents
Six Meter Nuvistor Converter Russ ell Summerville K8BYN . 9 Two 6C\V4 's i n c ascode g- Ive Il fea r ru ~ l y low nuiee figure. Power Meter Tom Lamb K8ERV . 12 Another valunb!e piece of t u . t gear (or t he h am " h a c k . Surqe Protection in Reverse Roy E. Pafenberg . 13 P rotect. y o u r aificon d iode puwer :s u p p! y f rom descr-uetion by s h o r-tin g-. Let's Modulate, Not Crepitate Richard Genaille K4ZGM . 14 Gettinjt good modulation out of a H eisinK Modu lator . ANew Noise Limiter ...... J im Kyle K5JKXj6 . 16 Get out the soldering iron , this one'll /:0 in your receiver. Calibration . Conway W ilson W4WQT . 18 W hy we ha ven't srct it , how much we need it . lind how to ~et it. Big Cannon J ack Holloway W6VVZ .. , 20 OK, here's a 20M K W amplifier, now stop bothcrtne u s fo r that. Tennessee Indians Gray Berry K2SJN . 25 The public relation" side o f taming t hose I ndia ns. Half Wave Feedlines Bill Robeds W9HOV . 27 One resonant feedlfne fo r severn! bands ? YUl),
Automation Jim Kyl e K5JKXj6 . . . . , . , . . .. 28 You did n't t hink we'd P II SS up A p ril without une Ientu re, did you'f Audio Boosting the Command Receivers Art Korn K8HDR ...... 30 Turns out to be rediculoualv sfm p le .. . once yuu know how. Pick Up the Droop Howard Pyl e W70E . 31 You r beam been II aKg}' late!}'? 40 Watt Transistor Modulator . Monroe McDonald KL7DLC .. . .. 32 Great fo r mobile rigs. Testing the Heath Twoer " .. Don Smith W3UZN . 34 You will no dou bt be ft abbergust ed tu Iind t hat Don like,," t he T woer. R-F Noise Suppression Bill Ashby K2TKN . 38 Tech n lea l t reatise on how to exorcise t he noise- demons. from your ca r . 432 me Transistorized Conveder . .' J. Specialliy W3HIX . 40 Part II (a hem) . the scheme t tc diagram. Take Your Pick Staff .. .. 42 Big tech nica I article : I F aelect ivit y nnd the devious means used tu Knin it. Propagation Charts for April Dave Brown K21GY . 54 W hat t.i rne, whe-n , to w here on what ba nds pr-obably, Writinq for 73 Staff . 56 H ow to gt>t rich beyond your wildest d r-eams. Misc.: Staff: T.-: ble of C ontents , ,... 3 editor-publisher Wayne Gre en W 2NSD Editorie] ," .. ,, ,. 4- publlcetions mO ""ger , , .. Da vid Fish New Use for e C rvstel Socket ,. . ". ,, . 24- essoclete edito r .,, , Don Smit h W 3UZN Ohmmeter Poleritv Check , ,.... . 27 eesociete e ditor ," , ." " J im Kyle K5JKXjb esscclete ed itor ,., Morvin lipto n VE3 DQX Toroid Tip ,, ', 33 essocie te editor C harles Spitz W 4A PI Be ndel lin n K8lAP Certocn ., .. ,.. 50 sa les re presentetive , J im Morrissetf W A6EXU Three Dee W orld and U.S. Mops ,.. 51 sa les representoti ..e J a ck G utzeit W2 LZX letters ,, ". .. 51 ph otoqrepher J oe Schimmel W2QDM Club Subscription Retes , ". '. . 52 subscriptio ns . . ,., , .. , Mrs. Virginia G reen .AF MARS Te chnical Broed cests " . . , .. ,.. .. 59 tren sportetioo ,., ,, . Porsch e O t her H a m Publicatio ns ... 63 printing . ... . Ye O ld e O 'briene Presse
COVER: W 2M UM's tower 0 5 phctoqrepbed by J oe Schim me l W2QOM.
13 ~Ia lui nl!' II IlnMllhPd mOnlhly by " mRtll'Ur Radio Publlshlnlr. In.... 116 Main ~1..eer. :"on..lk . Conn~tl rul. BUl lnl!'U Om Ml , l!T9 Eut 151h ~l r t"i"I , B rook l)' n 30. :-;fYo' York. 'relepbone : :S."- 9·01110. ~u b l crlptloa rat" : 1' .::;. .-\ . Inti poesesatons, "1'0. FPO. C.nad. anti ),Iuteo; one year 13.00; 1\\ 0 yean $5 .00; thrf'l!' ,.&lIn $1.00 . F orll'll[n : ,,,'.. fur $ ~ . OO ; 1\\" yea rl IT.1l1l S",-ond-.-l... poltaae n.id . t ~<7r'Walk . Connecticut. Printl!'lt In IhI- L'" .S. A. Entire centems ..t1llyrlaht 1961 by Ama te ur R adiO I' uh ll l h ina . Inc. Postmasler: P leal8 send form 3519 to 13 ),r ,.,gazlnc. 1379 East 15th Su-eet , B rook lyn 30 , xew YUI"k .
A PRIL 19 61 3 • • • de W2NSD
(never say die)
The more observant readers will d iscover ham journals. T'hia means that we 're depend that we have thrown budgetary ca ution to the ing quite a lot on your to tell others about 73. winds this month and have bou nd in a post If every reader men tioned i3 to every contact card. The reasons behind t his are manyfold on the air for a few weeks, every ham in t he and would possibl y be t oo numerous to men count ry would at least hear about the maga- tion were it not that I have little else t o com z•me. ment on. Grumbles Besides goading more of you to vote on the articles you find most interesting, the card also Someone wrote in compla ining because he will enable the more industrious to request found some sma ll errors in the magazine. He literature from our advertisers j ust by writ wanted to know why we didn't hire a better ing in their name and addresses. Ha ving al proof reader. The three examples he used to ready experienced t he drawbacks of merely p rove that 73 is a " ma ss" of errors consisted incl ud ing a reade r's service cou pon in a maga of two words with transposed letters and our zine and being aware that the advertisers " Subscr ip ti on Depart ment" ad which he know how easy it is to circ le a f ew extr a num t hought was mispelled. bers on incoming cou pons to make t he response \Ve will have to hire ou r first proof reader look good, we plunged ahead with a more fool before we can attempt to hire a better one. proof syst em. Virginia and t he authors do the best t hey can Let me put in just a short cong-ratulatory to correct the sometimes incredible mish-mash st atement . You fellows have been doing a fi ne tha t comes back from the printer. I look 'em job and are holding up your end quite well as over too. Wha t in the devil is it that bothers readers. The advertisers, who a re paying fo r some folks so much about a n occasional word t hi s magazine, a re enthusiastic abou t your re g-etting- bolixed up . .. it isn't as t hough t hi s s ponse and I not e that many of t hem, after g-ave t hem even a slig-ht diffi cult y in figuring trying you out for a mon th or so, have decided out what is being written. The next thing' you to sign f or a f ull year of advertising. Don't know we'll be getting r equest s for correct let down. g ramma r usage. Good grief! Building \Vhile t hese odd chaps are going over t he magazine with a fine tooth comb looking for ' Ve are ~ttinK more and more letters from errors we are trying desperately just to make readers who claim that 73 has pushed t hem su re that we get all of each article in each over the brink and started them to home brew issue. I t is awf ully easy to leave out a parts ing. Operating is fun, but it is onl y half of list , a coil table, 0 1' a photograph during the the hobby. ' Ve have a long way t o go ye t.W e'll last hect ic hou rs of hassle when we are t rying keep at it with everything we can muster t o to g et everything set fo r the presses. Just develope t his atrophied activity. Those of you how easy I fou nd out last month when we who have been around the hobby for a few managed to leave out the whole schematic years can remember when the loca l di stribu diagram for the 432 mc converter.How many tor had a big parts department with tables of of you frustrated proof-readers noticed that specials. You may even remember when parts one? Ha ! Well, it's in this issue anyway, manufacturers advertised in ham magazines. marked "part II." How many of you have seen a Bud catalog? How come no proof readers? Beca use we I used to practically wear t hat one out looking are t r yi ng to bring you a new type of ham over their coils, racks & panels, a nd small magazine a nd we sta r ted f rom sc rateh without parts. Maybe, if we keep at it , we can see much scratch. P roof-reading vol u nteers will a r eturn to t he old days.Ma ybe we'll aga in be be accepted at our editorial offic es at any time, able to pour over catalogs of parts by Nation the only thing is t hat they will have to work al, H amma r -l und, J ohnson , P a r-Met al, and for the sa me sala r -y as the rest of the st a ff. Mill en. Propaganda Caveat Emptor
. . There are still a lot of fellows who don't I n s pite of our acknovvsledged pover t y we are, know t hat 73 exists.We cannot, a s you should I beli eve, t he most particula r when it comes to be a ble to fi gu re ou t , advertise in the ot her ou r adver ti sers. Again, we have to depend on
4 13 MAGAZINE INTERNATI 0NAL 1961 CATALO G
AMATEURS- Complete data on International's all transistor subassemblies; 6 and 2 meter transmitting and receiving gear; crysta l controlled conver ter s fo r 75, 40, 20, 15 and 10 meters. CITIZEN LICENSEES Interna tiona l transceivers, accessories and antennas for dependable 2-Way radio communication. See Interna tional's kit for constr ucting your own Citizens transceiver. EXPERIMENTERS - Printed circuit oscillators, RF con verters, IF units, audio un its, tran s is tor s u b asse m b lies, c r yst a ls and crystal ovens. Mail today for your FREE Catalogl •••••••••••••••••••••••••• International Crystal Mfg_ cc., Inc. 18 North Lee, Oklahoma City, Okla. Send Free 1961 lnt ern.tional Catalol:
No m".~ _
Address' _ •• • •,• City' Zone St ate : ••• ..•••••••' ' li.:••••••.! "..
APRIL 19b1 • S •
you. Please let us know if you have a ny prob lems, hut don't a sk us to mediate or stra ig hten them out. If we get sever a l compla ints we will j ust have to look elsewhere for an advertiser.
Feedback We've enoug h votes on the January lineup of articles to conclusively determine the STRENGTH winner. Way out in front wi th 229 votes we find Tom Lamb's Nuvistor Converters. Our monthly technical article placed second with 1-17 votes. In third place wi th 11 5 votes is Down With Dr ift by J im Kyle. 1296 mc b)' o Bill Ashby was fo ur th 'wit h 96 votes. F ou r z THREE REASONS WHY othe r articles received over 50 yates. I'm learn YOUR BEST BUY IS ... ing a lot f rom the yat es. Some a r t icles t hat I figure a re of lesser interest turn out to get a lot of yates. For in sta nce take the " 8 me Crystal Modificat ion Kit" article by \V3UZN in January. I figured that Heath and a hand I ful of readers would be interested. Believe it or not we g ot 43 votes for this article! How I E·Z '!!AYA ERO.DYNAMIC many people could be interested in 1296 me ? ... design decrea ses wind load 96 votes is quite a landslide. • Cind provides te lescoping The February issue vote puts Kyle right action t hat p ermits ra is in g back up on top again. His "Rolling Your Own" , a nd lowering of t o w er sections. really rolled up a score ! All of which would CRANK U PTO 60 FEET. DOW N TO 25 FEET and seem to prove that interest is high in build TIL TS OVER FOR ACCESS ing. The VHF's get a lot of votes, so perhaps TO ROTOR OR BEAM. it isn't too surprisi ng to have this 50 me rig pull down the fi rst prize : a n all expenses paid l STRENGTH i s built-in to every E-Z Way T ower . ••Heavy trip to Santa Susana, California . .. plus 50 % e:( wa ll stee l t ubing l e g s , co n extra on t he article payment. Second place t in u o u s dia g onal bracing o f goes to another V HF r ig, t he Two Meter Pip solid steel rod a nd elec tr i c Squeak by Ray Fulton K6BP. Ray is just re co lI y we lded t hr ou g h o ut •. •. no covering from a n accident whi ch st ove in a lo os e baits o r n uts here . E-Z few ribs and he may be behind on answering :E Way deJ ign and s t reng t h o re mail. QUI' big technical article on BFO's came e:( yo ur assura nce of DEPEND. ABILITY t hat you con coun t in third! T he re j ust isn't any question, we've w on yeor after yeo r . See y o ur g'ot to run more good technical articles. Kyle's a:I nec r e s t distr ibutor t od a y o r Worlds Sim plest Phone P atch was Iourth, with write for free li terature. Squawk hy Ken Cole, W 7IDF fi fth. Both of our commercial gear evaluations got many Q Th e SATelLITE votes from ot her than the manufncturers so Model RB X-60-3P (Pointed) $335.00 we'll cont inue that sor- t of thing. Z Mode l RB X-60-3G (Galva ni zed) $410.00 Conventions e:( MOUNTING kiTS: GPK X60-3 (Ground Pos t) a:I $125.00 We'll be seeing those of you who attend BAK X (Wall Brocket) $17.00 - the Swampscott, Dayrt on, Rochester and Freight Prepaid a nywhere in (48) U.S.A. Phoenix Convent ions. Don't f orget that Phoenix dat e on l\Iay 26-29th. It isn't much of a drive from Southern Ca lifo r nia , so I hope all you fellows come on over for t he fun. Virginia will be there with me and would like to meet you all.
California Style
U. S. # 1 Electronics will offic ially open t heir £-z WAY store in Linden New J ersey on April First. I'll be over t here picking things over a s soon as they open up for they tell me that they have a ® • veritable mountain of su r plus st uff there. .. . W2NSD
6 73 MAGAZINE MODEL HE·26 HYBRID PHONE PATCH Perfect for AM-SS B Ph one Pa tch operat ion . VU Meter monitors line level for Q5 phone patches. An unmatch ed low- 1\ 24.50 ~
MODEL TM·15 WAVE METER Che cks transmitter output for 8.95 harmonics, parisitics, and cut of·b and operat ion. Prov ided with magn etic feet. Perfect for , the novice.
MODEL TM·14 FIELD STRENGTH MET ER Co mplete , no wires t o connect. 37.50- Monitor tra nsm itter o ut pu t; HE-2B RF WAITMETER check ant en na s, etc. Perfect for mobile, provided wit h mag AND SWR BRIDGE netic feet. 150 watts full scete -c-auttt-rn du mm y ' load- Wattmeter ± 5% to 54 meso SW R ± 5% for In line use. 7.95 AN UNHEARD DF BREAKTHROUGH IN THE COMMUNICATIONS RECEIVER FIELD THE LAFAYETTE HE·3D • TUNES 550 KCS TO 30 MCS IN fOUR BANOS • BUILT·IN Q-MULTlPLIER FOR CROWDED PHONE OPERATION • CALIBRATED ELECTRICAL BANOSPREAO ON AMATEUR BANOS BO THRU 10 METERS • STABLE OSCILLATOR AND BFO FOR CLEAR CW AND SSB RECEPTION • BUILT·1N EDGEWISE S-METER THE DREAM RECEIVER FOR TODAY'S 99.50 CROWDED BANDS AND AT AN IDEAL PRICE
-~--
~~.At..~E"I""I"E 165-08 LIBERTY AVENUE, JAMAICA 33, N. Y. '. .a B. .At.. :J:> ::I: <> or,,, LOCATIONS - -'-- NEW YORK, N. v., NEWARK, N.l. I BRONX, N. Y. IPARAMUS, N. J., BOSTON, MASS. I PLAINFIELD, N.l. 100 6th Avenue 24 Central Avenu e 542 E. Fordham Rd. 182 Route 17 no Federal Street 139 W. 2nd Street ------T------I Lafayelte Radio Dept 73· 1 P.O. Box 190 Jamaica 31, N. Y. .. . FREE 324-Pale: 0 $ Enclosed. Send Stock # ...... 0 Rush fREE 324 Page Catalog 610 1961 I 0 $ Down Payment Enclosed for Stock # ~ _ . Catalog No. 610: Lafayette Easy Pay Application Will Be Forwarded Upon Receipt of Down Payment
I Him. Cut Out & Paste I Add~ .. on Post Card ~ i CII7 ZO"- l tat-
APRIL 1961 7 - •
MI lton S 3909 t4tIlI'Y High Vi e.,. El ectron i c r E. Peer ' a I Rd . 3300 .'I'or t h nstr ~ellt Co " 111no18 LOIlg hI eroQ 81v cl . . , Inc . Il1Icl cr ty 1 D..-s r Si r- ' s , Y.
I 90·WATT CW I n •• TRAN SMITTER- I NEW! I • \ . • .' • # 720 60·WATT CW I __ . Kit $79.95 I TRANSMITTER I CITIZENS Wired $119.95 I # 723 · U. S. Pat. No. 0·184.776 t(it $49.95 BAND " Top Duality" -ELECTRONIC I Wired $79.95 : ~ TRANSCEIVERS KITS GU IDE. Ideal for vete ra n or Idea l fo r novice or advanced ham 'L..-/ Single and novice. 90W CW, 65W external I needing row-power, stand·by r ig. prate modulation. 80 thro ugh 10 60W CWo SOW extern al plate mod I MultIChannel Models Ava ilable. I ulation. 80 through 10 meters. I From Kit $59.95 Wired $89.95 meters. 1 ------~------, I • or' f' HleH·LEVEL I - _ I ~ != UNIVERSAL ·i,r- '.', . y:'" J !II MODULATOR· I ' ' lit I/"S CRID I ... .c _ " -~__• D.IVE. I ~J DIP I_ PEAK·TD·PElK ~ - # 730 METER 0.-.0 YTYM # 232 z Kit $49.95 Wired $19.95 I #710 I• • 0 Delivers SOW undistorted audio. I Kit $29.95 Wired $49.95 I 't t &. ·UNI ·PROBE ~ ~ Modulates transmitters having Includes complete set of coils .:--::'t' W i:'::~ ~: ::~ ..... RF inputs up t o lOOW. Unique I for full band coverage . Cont inuo I - . ;,g cver-rnocutattcn indicator. Cover ous coverage 400 kc to 250 me. VACUUM TUBE VOLTMETER # 221 ~ ------[·5 $4.50. ---r------T------I 500 ua meter. I t(it $25.95 Wi------red $39.15 _ I COLOR &. I RF SIGN AL MONO DC·5MC I DYNAMIC I GENERATOR LAB &. TV s- I CONDUCTANCE I " • #324 OS CILLOS COPE • HHlHlIt.lo TUBE J • •• (150kc:-435mc:) #460 J I I &. TRANSISTOR I l& iii . ~ M $26.95 Wired $1 29.50 - - TESTER # 666 - Wired $39.95 Kit $79.95 J I - Kit $69.95 Wired $109.95 TV·fM SWEEP GENERATOR 5" PUSH·PULL OSCILLO SCOPE I TUBE TESTER # 625 I &. MARKER # 368 # 425 Kit $44.95 Wired $79.95 I Kit $34 .95 Wired $49.95 I Xit $69.95 Wired $119.95 EICO, 3300 N. Blvd., L.I.C. 1, N. Y. I 730 o Send free Catalog & name of 'Name . neighborhood distributor. ~~~ii:Li~;~~~~~~.tr~~i~::~ ,'Address .
25c enclosed for postage I City Zone Stat e . & handling. I Add ~ 'Jl, ill ~ '-u t.
ENGINEERS: Excellent career opportunities in creative electronics desIgn. Write t o the Chief Enl ineer.
a 73 MAGAZI NE . .., .. ..
Russell M. Summervill e K8BYN Box 354 Niles. Michiqen
Fig. 2 Six Meter Nuvistor Cascade Converter
OR many years it has been the secret desire on the Nuvistor sockets and slip them int o the F of almost every amateur interested in the t op of the holes cut for them. Solder t he t abs VHF bands t o own one of those gold plated to the t in plat e. Be careful not to bend the 417A converters, but for most of us scr -a pi ng lugs on t he socket that a re for the pur pose of up the gold dollars to buy the tubes has been g rounding the N uvist or sh ield ,..hen it is in out of the question. serted into t he socket. Now a miracle has happened! RCA has de Two 8 ter minal tie lug st r ips are m ounted veloped a tiny ceramic tube which they call 2 %, inches apart and r esist ors " A" t h r u " H" a Nuvistor for use in their TV tuners. These are connected across the point s. All of t he re little gems at a cost of only $2.49 each are the sitors on the str ip near the ou t side of chassis answer to your dreams. For a ll practical are connect ed together and t his is t he B plus "ham" purposes they perform about the equal bus line. ( F ig. 3.) of the 417A! Althou gh it is not necessa r y to use them, for After listening to a commercial on TV all convenience and t o sa ve s pace dual ca pacitors about how noise free RCA's Nuvi stor tuner were used on each tube socket a nd at the was I decided just for kicks to build up a terminals of t he if transformer s. Keep all 6 meter converter using Nuvistors in cascode. leads short-mount the capacitors a s close to The resulting converter out perfor med most the socket pins a s possible. If you use d uals, conventional converters and equaled a couple j ust ground t he center lead a nd connect t he 417A converters in comparative noise tests. outer leads to the poin t s to be bypassed . It is customary t o use rf chokes in series Construction with filaments and to bypass them with small To mount t he Nuvistors cut out a piece ca pacitors. B~· using' shielded wire (the t ype of t in ( t in solders r eal ni ce ) 1% inch b)' 1 %. with heavy wire and high inter nal ca pacit y) inches and drill 2 holes just the size of t he fo r fila ment wiring the use of rf chokes a nd Xuvistcr sockets. Also drill 6 holes around the bypass capacitors is not necessa r -y. Be sure to edge of the tin plate. These are for mounting ground the shield close to each socket. screws to fasten the tin plate solidly to t he A neut r alizing coil is usually employed aluminum chassis. (See Fig. 2.) Mount the where ,..·e use resistor "L". This coil t o be tin plate to the chassis. Bend back the 2 tabs useful. ..must be. r esonat.ed at 50 me and unless
9 APRIL 1961 • • "
Fig. it is correct it does little jrocd. The increase to make all units exactly alike. If you find in noise because of the use of the resi stor in in final alignment that with t he slugs all the place of the usual coil is neglig ible. way in the coils will not reach a peak then add a small capa citor from ground to plate or I·F Transformers g rid depending on which coil needs lowering or both if necessa r y. (See UK" in Fig. 1.) The if transformers can be made from -10 Several makes of slug coils were wound a s me video if's removed from an old TV set , or described and all were found to resonate fairly if you want to use new parts use Miller #6218 close to 50 ru e when connected in to the ci rcuit. T V video if transformers.Remove all of the If extra capacity is needed use as little a s existing windings a nd wind 17 t urns of # 18 possible usually bet ween 5 and 20 mmf d. enamel wire to form the lower part of the transformer and connect to lugs. T hen wind Coils 10th turns of the sa me wire to f orm the top half of the transformer and bring leads down The input coil 1.1 is made of 10 th turns of to the lugs and solder. #2:! bare wire wound around a %. inch coil I n all tuned circuits in which a wide band form tapped at 2 turns for the antenna input. pass is necessary it is possible to broaden out An A irclux type of coil could be used. The t he r espon se ei t her by putting a " swamping" important thing- is to be sure t ha t with the resi stor across the tuned circuit or to make antenna plugged into the jack, the tube in the use of a circuit having a large L IC ratio. The socket and the circuit wired, the circuit will latter method is used in t hi s converter in both resonate at 50 mc when the tuning capacitor the if transformers and the input and output across t he coil is tuned. If t he frequency is coils. T he idea is to have the coils "self too high add another tu rn or two to t he coil resonant" KO that t hey resonate at the signal if necessary and, if too low, take off a t urn frequency with little or no capacity other tha n or two. di stributed ca pa cit y, str ay circuit ca pacit y, and T he f requency of the crystal and the oscil tube capacity. Sometimes a sma ll amount of lator tank circuit (La) must be 50 mc less ca pacit y is necessary because it is impossible the out put frequency desired from the con ~ 1\ O= l t~ verter. F or exa mple the SXlOIA has a 6 mete I' d ial and requires an input of 30.5 me.
~ '"'=-.IS OUT"'JT -jt;]!- The oscill ator frequency then must be 50 minus "Q~O w,~ ClIT r ...of MClU '" , 30.5 or 19.5 me. You can use a fundamental or J 4 . LZ I --Y: -""' "lATt-,."....,ovtI' " overtone 19.5 mc cr ystal or a cheap s ur plus ~ r i.-vo,,· -t-W-~ lower frequency crystal and multiply in t he IlO WCUD second half of the (jJ6 to t he desired frequency. • OUT""'" Fl 10 73 MAGAZINE - would work wt h more crys :a ls than other more com alicated circuits. The ou t put coil ( 1,2) must be broad a nd :; 0 it is tuned to resonance by it's ow n di stributed capacity. With the bottom slug of t he coil all t he way in and t he top slug part wa y in , put en o u g h turn s of wire around t he form so that it will reson at e at the desired out pu t f requency. This will have to be done experi mentally a n d checked with a grid di pper while the coil is wired into the circuit. The conver t er Fig. 3 shown here ha d an output frequency of 30.5 megacycles and it was found that with 25 sig na l sou rce to a round 50.3 me a nd adjust C tur ns of #22 enameled wire t hat frequency across antenna in pu t coil for peak. Set Sig was obt ained . If you want to use a low out p ut nal sou r ce to 50.8 a nd t une the top of T 1 frequency, such as 5 meg a cycles, it would be a nd T2 for maximum readi ng on S meter . If desirable t o use a finer wire. meter goes above 8 9 reduce rf gain control. The oscillator coil ( L3) is a tank circuit Then set sig nal sou rce t o 50.1 and adjust t he and s hould be a fa irly high Q so some capacity bottom of T l and 1'2 for peak reading. Now should be across t he coil. It was found tha t set to 50.5 and a djust output coil 1.2 for Ma xi with a 25 mmfd capacitor across the coil it mum. If you cannot get a peak with slugs all would tune to 19.5 me when wound with 15 the way into the coil add some ca pacity a s turns of # 18 wire.To pick up a sig nal for described earlier. You should get very broad inject ion into the mixer a cou ple turns of in peaks-don't expect a sha r p one.T he s ha r p s ula ted wire is wrapped loosely around the ness of the peaks in no way indica tes the noise coil and soldered to the lug which connects figure of the conve rter . In fact we found with to the mixer grid through t he 15 mmfd capaci t he input coil way off frequency we could st ill tor. The coi l f orm (slug tuned) was removed get a good noise figure with much reduced from an old T V t u ner, but a Mi ller 6218T V sensit ivit y. video if transformer would work here also, as would many other types of coils. Conclusion Power Requirements T hi s converter is hot- it puts out more than an 89 "hiss" in to mo st receivers. If your re- The converter will draw about 35 rna when t he voltage on the B plus bus ha s 150 volts on it. Resistor " H " is a vol t age dropping r esistor in ser ies with all of t he decou pling } , and dropping resi stors feeding the tubes.If your power sou rce is 250 volts you will need a drop across " H" of 100 vol ts. Since E 100 R = - we find we need 01' approx. 2860 I .035 ohms. A 3000 ohm resistor would work fine. The power di ssipation needed would be 100 X .Oa5 or 3.5 watts. A 10 watt resist or would he OK but a 20 watt one st ill better since by using a much la rger one t here would be less Fig. 4 heat dissipated. If your sup ply is 150 Volt s connect directly to B plus bus line. cerve r does not ha ve a n rf g ain control it would probably be well to reduce the output Alignment of the converter feeding the receiver by put t ing a very sma ll capacitor "J" in place of F rom a WEAK signal sou rce such a s a weak the .001 s hown in the d ia g ram. The f'ront of st a t ion or sig na l generator OJ" crystal oscillator the converter is quite su bj ect to overload f rom adjust the rf gain control on your receiver st rong st a t ions and because of it's g rea t sensi- so that t he 8 meter will read about S 5. Set (Continued on page 61 J APRi l 1961 II The Power Meter Tom Lemb K8ERV 1066 Larchwood Road Me nsfl eld. Ohio H E Power Meter was designed to be a T " dummy next stage." When coupled t o an oscill a to r , amplifier or multiplier tank coil it will indicate the a pproximate drive available for the following st age. It is basica lly a com tinuous tuning, link coupled absorbtion wave meter with a loaded and metered r] indicator. The Circuit T he fi rst depa rture from st anda rd wave meter design is the use of a mult iband reso nant circuit, tuning 4 to 35 me. T he very simple MBT described by J ohnson! solves the problem of winding and finding numerous plug in coils. The reader should refer to J ohnson's Remove the lamp and set S I to l OK-l rna . m-t icle for changes in the t uning ra nge or Loosely couple t he link to a grid dip oscillator. L and C values. As with any multiba nd tank, Set each desired calibra t ion frequency on the two frequencies ar e t uned simultaneously. GDO, peak C l and murk the di al. When t he However, these t wo frequencies are far high end of C l is reached, pick up 'he sa me enough apart that the correct one will usually f requency a t the low end and keep on going be obvious from the circuit under test. up. The l\IBT is coupled into the simula ted The Power Met er will do anything a con "next stage" consisting of variou s values of ventional wavemeter will do, within its fre grid resi stance, a grid current meter, a nd a quency range. Some of its uses are: GA L5 diode . Don't t r y to use a semiconduct or Frequency Indica tion-Method 1. Cou ple t he d iode in this circuit. Power Meter link to a n operating circuit, pea k A #49 pilot lamp is coupled to t he MBT for the meter with CI, a nd read the frequency. those who are used to it s power ind ica tion. T he S 1 serves as a sensit ivity control. Note that lamp should be removed from its socket during the dial will indicate two possible frequencies. calibration, accurate frequency reading and normally the correct one will be obvious, but there is no way of being s ure without addi t ional equipment. This is t he disadvant age of the mulitbanrl tank. Frequency Indication-Method 2. If the t uned circuit to be measu red has its own indicator, such a s a g-rid or plate current meter, simply use the P ower l\Iet er as an abeorbtion. wave meter. Couple the link to the operating- tuned ci rcuit a nd adjust C l for a sha r p dip in the circuit's Indicator. The a dvantage of Method 2. is t hat no line power is required for the (jA L5, making the P ower Meter useful for portable and mobile work. Harmonic I nd ica tor. Couple the link to the circuit being tested and run Cl throughout its range. Use 8 1 for a sensit ivit y control. All metered power reading. f requencies present will be read and their rela The construction is not a t all critical. This tive voltages indicated." meter was thrown tog ether in a h urry to meet It is int eresting to not e t he amount of u n an immed iate need. Mou nt Ll. to C l with sho rt desired output in high-or de r f'requency multi. leads, don't place metal panels too nea r to L t , and you have it made. - .\'ote t lrot the meter j " d icl,lt ioli ttI I ~ 71 ~AGA Z INE • pliers. The low Q tank circuit usuallv used in multipliers may pass considerable ·energy at one multiplica tion above a nd below the de sired one. Thus in a quadrupler t he P ower 6Al5 ~ Meter will show additional outputs at three and fi ve times the f undamenta l. If strong enoug h, t hese outputs can contribute to the 2.5Mh'" grid current of the next stage and g ive a falsely high r eadi ng. PL . 4 ~ In t he hetrodyne t ype of exciter, the output j'~ strength of the undesired products of mixing .,. is strongly affected by the amplitude of t he in "."U put signa l. Indica ting t he rela tive voltages of lsttt:" ~1( PROBE- IT I- GiG. the desi red and undesired outputs is a main feature of the P ower Meter. Output P ower Indicator. \Vhen breadboard "''" as ing' an oscillator or multiplier, the P ower , '00 Meter becomes a metered load, or d um my next ., - '0' , sr stage. Set Sl for the planned resistance and 0 current of the next stage, couple the P ower • 0 Meter to t he output coil, and read the approxi • mate dr ive that will be obta ined. •• \Vith a little experience, the P ower Meter " ca n be one of the most usefu l accessories in the , .R shack. It is in almost daily use in mine, and I would like to hear f rom anyone fi nding other useful applica tions. 73 • Surge Protection Reverse Roy E. Pofe nberg OLTAGE multiplier power supplies have The entire question of safety shor ting of A inc reased in popularit y since the int ro ca pa citors is open to debate. Ca pacitors, even duction of silicon diodes. T he classic voltage of t he electrolytic t ype, can hold let hal charges t ripler circuit is familiar to most a nd the for a substantia l period of time and common function of t he input surge r esistor needs sense dictates that t hey should be discharged little explanation. The value of this resistor, before working on t he circuit. On the other R l in F ig. lA, is such as to limit t he cha rg hand, short circuiting the terminals of a ing current of the capacitors to a value below charged capacitor can result in current that the maximum surge current rating of t he recti will fuse t he internal leads of t he unit. Also, fi ers. F or example, the Sarkes Ta rzian 1\1 -500 rig-go ing of haywire limiting r esistors to safe ly silicon diode is r ated a t 30 a mperes surge cur discharge the capacitors could possibly result rent. The li miting r esistor is calcula ted on the in more accidents that the procedure was de basis of peak a pplied volt age a nd f or a line signed to avoid. 117 x 1.414 The best answer a ppea rs to be t he inclu operated supply would be or at sion of limi ting resistors such as R2 and R3 30 in Fig. IB to provide protection to the com least 5.5 ohms. ponents in the event of accidenta l shorting of the supply and a fail safe bleeder circuit for Xot so obvious is the function of resistors personnel protection. T his a r rangement wiII R2 and R3 in Figure IE. Assume the power provide the maximum protection to components supply shown in Fig. lA is delivering- power to a nd t he amateur. . Pafenberg a light load and t ha t t he input line is opened, leaving Cl cha rged to t he peak line voltage. Accid en tal or safety sho rting of the supply output will discha rge Cl t hrough diodes CR2 a nd CR3, invariably leading to the catas trophic failure of both rectifier units. Resis tors R2 and R3 will limit this current to a safe value in the event t he power supply out put is accidenta lly shorted. Values the sa me as Rl should provide adequate protection with commonly used fil ter ca pacitor values. APRIL 1961 13 Let's Modulate, Not Crepitate Ri chard A. Genaill K4 ZG M 719 Quarterstaff Rood Winston-Solem, N. C. [i'VERY year, about this time, a rash of arti g ive one a fully modulated-low di stortion port £.J d es begin to appear in almost all of the able transmitter t hat will get results.Here's popular "ham" publications dealing with Iow how it's done, the easy way. power transmitters designed for mobile or T o under stand the basic f undament als of other po r table type ope rations.T hi s r a sh is " choke-cou pled" modulation take a look a t Fig. mo re t ha n likely caused by vis ions of vacation 1. T his is t he circuit of t he basic Heising modu trips, F ield Day activities or possibly t he end la tor and simplicity in it self. The in put power of the winter hibernation. At a ny rate, t his to t he fi nal ampli fi er is a combination of t he article is designed to help VOlt, the pros pective dc power from the plate su pply a nd t he audio low-power transmitter builder, to modulate power from the Class A Audio Amplifi er that fl ea powered job without having to make Modula tor. The use of audio choke CHI, rather any excuses for low modulation percentage or than a modulation transformer, establishes a severe d istortion. 1-t0-1 coupling ratio between the modulator You may have noticed that many of the tube and the final amplifier st age requiring portable transmitters described in various arti that the de plate voltage and plate current cles make use of "choke-coupled" or, more com to the final amplifier be a dj usted to a value monly, Heising modulation. In many cases, which will prod uce a suit able impedance match the author fails to ind icate that in his trans- between t he fi nal amplifi er a nd t he Class A Amplifier pla te. Even t hough we may be able to select suit a ble modulator a nd final amplifi er TO FINAL ",PUFl[R tubes whose electr ical char acteristics will pro vide a n impedance match we would not be able .. to achieve 100 per-cent modulation without I«lOULATOR severe di stortion unless resistor R1 a nd capa CLASS A AUOIO ...P\.IFIER cit or C1 were included in the circuit. T his is because, with ident ica l plate voltage on both the final amplifier and modulator, the audio frequency voltage developed by t he modulator cannot swing to the 100 per-cent modulation --- level ( Zero to twice the pl ate voltage) with out causing d istortion as it ap proaches zero. R1 provid es the necessary voltage drop be .. tween t he modulator and the fi na l amplifier to make possible a suffic ient a udio f requency Fig. I. Cheke coupled or Heising modulator. voltage s wing to permit 100 per-cent modula C I-Audio by - pass ca pacito r. C HI-Audio t ion with lower di stortion. The capacitor C1 choke (high impedance at a udio fr equencies). provides the necessar-y audio by-pass across RI -Dropping resistor (adjusted for 100% mod resistor Rl. T he reactance of C1 should not ulat ion by co nsulting tube charts). be more than one-tenth the resistance of R1 at 100 cycles. The value of R1 must be cal mittel' design he may have only 70 to 80 per culated by using the published family of curves cent modulation with low di stortion or 100 per for t he modulator tube use . \Vit hout R l and cent- modulation with Revere distortion. The C f , t he mod ulation percentage is limited to usual circuit arrangements for "choke-coupled" between 70 and 80 per-cen t to minimize di s modula tion do not per mit one to achieve a hap tortion in the case of t he averuge vtransmitt er, py medium between t he t wo extremes. T he It can be seen, by t hese f ew facts, that t he proper use of R eisi ng mod ul ation can result desi gn of t he circuit ent ails a certain a moun t in maximum simplicity, minimize expense and of calcula tion in order t hat satisfactory opera- 14 73 MAGAZINE t ion may be obtained. lat ed. Capacitor C1 should be of the oil type The circuit of F ig. 2 shows a syst em of and have a r eact a nce much lower than t he shunt feed that virtually eliminates t he need Class C rf amplifier load impeda nce at the f or extensive ca lcula t ions. One can usua lly dig lowest audio frequency t o be transmitted.In up a n extra choke in the " J" box, especially most cases anything from .5 t o 2 mfd. wiII do the sma ll, low cu rrent capacity receiver type. the trick. It can be seen that a difference in voltage can T o make t hings a lot si mpler when you start he obtained for the modulator and final a m laying out tha t low power r ig, F ig. 3 provides plifier either by t he use of t he dr op ping re sistor R1 or by the use of two separ a t e plate su pplies. For the sa ke of economy t he use of TO''''''-.no the dropping resistor is to be prefer-red . \Vith a means of obtaining two different vol t ages, the plate voltage for t he modulator tube may be kept hig her tha n the voltage on the fi nal amplifier thus per mitting the necessary a udio f requency voltage swing a t a lower dist ortion r-'IICHZ level. T he usual simple r f a mplifier plate im pedance calculations s hould be ma de and the amount of audio r equired f or 100 per-cent modul ation should be determined. Since the arrangement provides a I -to-l coupling r atio, t he tube select ed for t he modul ator should be .. capable of deliver ing the necessary a mount of a udio power (usually one-half of the rf am Fig. 2. Choke coupled or Heising mcduletc r plifier inpu t de power) at the same plate im using sh unt feed. CI-Coupling ca pacitor (oil). CH 1 & CH2-Audio chokes (filter 10 to 30 pedance a s the final amplifier . So t hat the Hy). Rl -Dropping resistor (adj. for correct af voltage on the plate of the modulator may fina l amplifie r plate volta ge ... see text) . swing su ffi cien tl y to produc e 100 per-cent mod C2-Filter ca pacitor (use only if RI is used.] ulation without t he swing reaching zero, the tube used in the modulator should be one a listing of t he most popular t ubes which can which r equires a somewhat hig her operating be used f or Class A Amplifier service at low plate volta ge than t he final amplifier. T he power output s. Many of t he portable r igs and audio chokes in Fig. 2 ma y be regular filter most of the Citize n Band units make use of chokes of the 10 to 30 henry variety. The a fi nal a mplifier tube which runs at a ppr oxi inductive reactance of choke CH2 should be mately 250 volts at 20 ma for an input of 5 at least equal to the Cla ss C am pl ifi er load watts. T he plate input impedance runs ap Impedance at the lowest frequency to be modu- prox imately 12,000 ohms.A ppr oxi mat ely 2.5 ,l:. ' watts of a udio are required. A 6AG7 woul d Power do a s plend id job in modulat ing in this ca se . Plat e Load Resi stance Output The 300 volt s on the plat e would permit suf Type Volts Ohms watts fi cient af voltage swing without d istortion, t he 6AG7 300 10,000 3.0 audio power is more than adequate, t he plate 6AK6 180 10,000 1.1 impedance is close enough to f u nction properly 6AQ5 180 5,500 2.0 and the 300 volts can be drop ped to 250 for 6AQ5 250 5,000 4.5 t he fi nal amplifier tube with no great difficulty. 6AR5 250 7,600 3.4 Another combinat ion might be a 6L6 fi nal 6AR5 250 7,000 3.2 a mplifier running at 325 volts and 70",ma for 6AS5 150 4,500 2.2 a n in put of about 22 ~ 'watis:: Th-e':'pli:it e : im 6BK5 250 6,500 3.5 pedance would he a round A,600 ' ~ hm ~" .and _the 6CL6 250 • 7,500 2.8 required audio power torfuu.per-cent rnodula 6F6 285 7,000 4.8 tion- would -be near 11 w'atts': > ' Another ~ 6L6 6F6 250 7,000 3.2 with' 350 volt s on t he pl at e woulddofhe "job GG 6G 180 10,000 1.1 quite well as t he modulator. 6G6G 180 12,000 0.25 The sh unt -f eed syst em ha s been used by 6K6GT 315 9,000 4.5 the aut hor in sever al low powered t r ansmitters 6K6GT 250 7,600 3.4 a nd ha s proven to be quit e successf ul. It is 6K6G T 100 12,000 0.35 always a pleasure to have other hams tell you 61.6 350 4,200 10.8 t hat your low power . r ig is ~ ,t he' besf'sonnding 6LG 250 2,500 6.5 one that-they have heard o'n the a ir and that 6V6 315 8,500 5.5 you have the a udio p u nch that most low power 6V6 250 5,000 4.5 rigs lack. The next time you start laying out 6V6 180 5,500 2.00 that simple modulator for t hat portable or Fig . 3. Typical Tube Types Useful in Class A mobile u nit g ive shu nt-fed Heising a t ry.' You'll Amplifier-Low Power Modulator Service be glad that you did. , . ., K4ZGM , " • APRil 1961 IS , • • Fig. I that t he only groups seriously interested in the problem are hams and citizens-band op erators, and neither group is large enough nor vocal enough to demand improvement. However, our British cousins have been forced to deal with the problem, since TV sound in Great Britain is carried on an AM cha nnel instead of the FM used here. At the f requencies u sed, impulse noi se has been a ser ious situation for them-and the video au dience 13 large enough and vocal enough to demand improvements. As a result, at least one British writer has declared that (under the proper conditions) AM sound may even be superior in signal-to noi se ratio a nd in general quality to FM. Be that as it may, they have developed some excellent noise limiters. The one shown here was described in the November, 1960, issue of Electron ic T echn ology (Television Noise Lim A New iting in AM Sound Channels, by H. D. Kitchin) and is capable of virtually wiping out all ordinary impulse noise from a com Noise-Limiter munications r eceiver. The circuit as shown has been converted to use standard American tubes Circ uit and part values. Jim Kyle. K5JKX/6 This li miter , though it appears simila r to our conventional ser ies-diode gate at fir st H E a utomatic-noise-limiter circuitry is to glance, operates on a completely different prin T day one of the weakest design links in a ciple. Rather than rejecting noise pulses be good communications r eceiver. While modern ca use of their amplitude, it rejects t hem be A NL circuits do remove some t ypes of impulse cause of t heir rapid r ise time. This enables noise, t hey still leave an appreciable amount it to detect even t he sma llest noise pulses and in the signal, and it's a r a re new-product r e to wipe them from the audio signal. port t hat fails to condemn the ANL with faint To get an idea of how it works, look first at praise. Figure 1. This shows (to accurate scale ) a Most of today's receivers still use gating 3000-cycle sine wave modulated on a 100-kc diode noise limiters, which eit her short the car r ier wave, a nd badly distorted by noise noise pulses to ground when a certa in level is pulses of approximately 10-microsecond dura exceeded, or open t he audio signal path for tion (most troublesome noi se pulses last from t he duration of the pulse. In neither case is 1 to 10 microsecond s, so this is the worst a nything done about no ise pulses which do not usual case) . Note that t he noi se may eit her reach limiting level. add to t he signa l, or cancel it out. T his signal In fact, most communications-receiver users exists at the detector input. habit ually set t he limiting level to operate at Figure 2 shows the same signa l as it would t he 50-percent-modulation point, thereby se be seen at the detector load r esistor. Note that verely distorting t he audio signal, in an effort t he only noise pulses which survive the detec to mi nimize noise leakage. tion process a re those which momentarily T he reason for lagging development of increase signal strengt h. noise-limiter circuitry in this country may be Figure 3 illustrates the action of the con- r-"?"-...._-... •,•• -----rr 16 73 MAGAZINE venticna l full-wave ser ies-diode noise limiter, Three cr itical points must be checked dur used in most mode rn communications receivers, ing construction. The volume control's total when t he limiting level is set to clip a t 100 resista nce must be 1 megohm, as shown. Any percent modulation. w hile t he high noise peaks different resistance will vary the load on the are eliminated, fai rly large " st umps" remain limiter, requ iring a change in limiter t ime and are f requently clearly a udible. consta nt (determined by t he 330K resistor and t he 80 mmfd ca pacitor from cathode to ground ). Connections to the last if t r ansfor mer mu st be as shown ; the existing diode r 8145 load resistor a nd fi lter must be disconnected. Frequently, these componen ts are located AF OUT inside t he if transformer case. If in doubt, T contact t he manufact urer or check service in formation. Finally, note t hat a ll signa l-ca rry - ~ -- ~-- ~, - - --~-~ ing lines are a t high impedance to ground .. ,~ , ~ '/ .. ,, ,, and are therefore subject to hum pickup fr om ,, ,, hea ter lea ds. T wist t he heater leads together , ,, a nd keep them away from all components. As shown, t he limiter will handle 100-per "., cent-modulated signa ls without distor tion, a nd will suppress most noise pulses more than Figure 4 shows t he r ate-of-cha nge limiter. 40 db below t he signa l level. If you should Incoming audio, conta ining noise pulses, is a p want to suppress t he noise more than t his, plied to the diode pla te. Negat ive bias equal a t a sacrifi ce in distort.ion, you can change to the peak-to-peak signa l voltage is applied the ratio of the 18K a nd 27K resistors which to the cathode.T he t ime constant of the bia s make u p the detector loa d resistance,Total resistor and the output capacitor, together va lue of the two, however, should be main with the bias voltage, determine the opera ting tained bet ween 45K a nd 50K ohms for proper point. detector action. Incr easing the 18K unit while w hen the time constant is proper ly chosen, the voltage ac ross the capacitor follows t he audio signal envelope which passes t hrough the diode, and the output is a replica of the • input. -;-- "" However, when a noise pulse causes a rapid ec cha nge of the input signa l va lue, the diode is m "" " suddenly driven into r everse-bias condi tions r- ~~ • and cuts off. The capacitor voltage t hen rises l\ '" [f -..-' 1,... towa rd the bia s value a t a r a te determined 16K ;: f' eo "'; ::::: AUDIO by t he time consta nt (dotted li nes in F igure 4) . As soon as the input signa l r eturns to a value low enough to reestablish forward-bias '- conditions, t he ca pacitor discharges to the audio-signal level and output once more fol decreaain• g t he 27K res•istor W•ill lower t he lows input. effective bia s level, t hereby suppr essing the The noise pulse is limited to a n extremely noise even more. . .. K5JKX/6 sma ll value by this process, if bia s voltage is a pproximately equa l to peak-to-peak signa l in Pul se Su ppression Below Signal Level pu t. However, if fixed bias is used t his will Pulse Width Series- Modifi ed ra rely he t he case, since signa l voltage varies (in microsec ) Diod e Rate-of-Change from instant to Insta nt , I 48 db 85-90 d b By ta king t he bias voltage from t he detector 30 db 55 db loa d resistor (through a fi lter) and obtaining 5 the audio-signal input from a tap on t his re 10 24 db 43 db sistor , insta ntaneous bias voltage can be set 50 10 db 15 db a t the proper va lue for minimum noise a nd 100 6 db 6 db zero distortion.A comparison of noise-pulse 300 a db a db suppression achieved by t his lim iter and by t he above not not series diode is shown in Table I. 300 effective effective T he circuit ca n easily be added to any re N OT ES: T'hcsc values ueaume a udio cutoff f requency ceiver now equipped with a diode detector. of :1 kc following limiter ; hig her cutoff frequency wiU ,ll'g l·ade absolute vnluea but w ill 1I 0t a lter r-u t io between T he schemat ic diagram is shown in Figur e limite rs. 5. The complete limiter circuit can be as Most noise pulses r a nge f rom 1 to 10 m icr o seconds sembled on a Vector 7-pin turret and substl in length. Suppresaion of 40 db or m or e effec tively eltmtnetee the t uted for t he existing detector . pulse tor most ltsteners. APRIL 1961 17 to set the little radio to 890 kc to get the sta tion on 900 kc-so the little $24.95 ec-de set is off a little, what do you expect, Collins WHAT IS dials? Joe tries to turn the shower completely off but knows it will still leak a little. He has never stopped to think that he may never get a good gasket for the water valve because CALIBRATION? there is little calibration at the gasket fac tory and all their little washers are just a shade small. Joe finally dashes to the car to head for work and notes the gas gage shows % full-Jr. must have used the car again last Ccnwev l. W il son W4WQT night. He dares not try to make it all the Route 3. Boll. 39 way to the job because that gas gage has Madison, Alabama never been quite right. The great mystery of America-who calibrate gas gages? Joe stops E Hams are a lucky group. 'Ve all have by the service station and buys 10 gallons of W the National Bureau of Standards right gas plus or minus a few pints (usually minus in our Hamshacks. We tune in W'VV and use a few) and finally gets to work. it to calibrate a "built-in" transfer sta ndar d Joe has to make a measurement or two crystal oscillator in our receivers. 'Ve transfer today, he is a part of a test laboratory. He this calibration right down or up to the band is going to test a little gadget that his com we intend to operate on. "re set a dial indi pany sells to a big Government Prime con cator or slightly change the VFO (local os tractor. He has to look at a waveform or two cillator) frequency and oper ate all evening on a scope and make a few de voltage meas on our pet Ham band within a few c~rcles of urements. Ask Joe about the calibration of his the frequency shown on the receiver and trans equipment and he will tell you right quick. mittter dial. To prove our abilities as calibra "Old boy, look on this meter, it has a calibre tion experts it is not uncommon for us to tion sticker on it-why it is due for calibra argue with each other over our operat ing fre tion' tomorrow, one of the boys from the quency-why to miss it by 50 cycles is often sta ndar ds lab should be around sometime today a complete disgrace. 50 parts in sever al mil to get it and supply him with another that is lion is good and we know it. Yes, we Hams calibrated." The sticker shows that the meter are a lucky group but ... alas, the next was, indeed, calibrated last summer sometime. morning we go to work and forget our sense Sure enough the calibration expert shows up of accuracy completely. On the job we are and takes his meter for calibration. Noone an omphaloskepsis (you had better look that has ever calibrated his scope because after one up). all it is the latest model "Technetroonix" and It is the purpose of this shor t article to get the book says it is accurate to 3%. Old Joe just a few of you, at least one in every factory, has never stopped to wonder if the book meant one in every part of industry, to go to work it would always be 3% until somet hing went for better calibration on the job. Just ask wrong with it or if the book meant that it yourself if someone on your job is being as should also be calibrated periodically. exact with calibration as you are when you Old Joe Ham decides to ask a few questions set your receiver f requency. Ca librat ion is about calibration. When the expert comes for important no matter what you do for a living. his meter he quite casually asks him. "What If you make shoe laces, wor k at a ser vice do you check my meter against when you station, a meat market-yes, even dig ditches calibrate it?" He is told, "'Vhy anyone should you or someone makes measurements of one know that, it is carefully calibrated against sort or another. If you cannot trace that meas a 0.25 % Standard meter, a real expensive urement back through a ser ies of calibrations job. Boy, you are lucky we have such good to the National Bureau of Standards you don't calibration in our factory ... and besides, we have calibration. Somewhere up the line there do this for you every G months." Joe decides is an omphaloskepsis that needs to be awak to press the subject. "Hey," he says, "how ened. about that Standard meter? Where is it cali Let me outline a t ypical case. Let us follow brated?" The meter expert looks down his a typical Ham through a not too typical day. nose and says, "Arc you kidding old boy, Let's call him Joe Ham and heaven bless the that's a Standard meter, the manufacturer real life Joe Hams who may read this. Old rates it a 0.25 0/0 full sca le and it doesn't need Joe wakes up at 6 AM, plus or minus a minute any calibration. who do you think we are, or two. His alarm clock is always off a little the National Bureau of Standards?" And so but the local broadcast sta tion blares out the it goes. Joe Ham is happy so is the meter ex time sever al times as he t r ies to sha ve and pert. Joe thinks he has good calibration and catch the morning news at the same time. In t he expert goes back to the lab and brags to cidently, he hasn't noticed that his XYL had the boys how he got that jerk J oe Ham all II 73 MAGAZINE squared a wa y about ca libration. Actually, of course, it is not this bad a t most of the factories. I have, however, seen some t hat are much wo rse. Figure 1 depicts - a good calibration path to the National Bureau of Standards. It is a series of closed calibra tion loops, each a link in the path to N BS. J ust a s with a ny ot he r cha in, it is only a s strong a s its weakest link. Can you t race every measurement you make along a chain of this type? If not, your job may not be turning out a good produc t. T he wonderful thing about t he sit uation is t hat it only takes one good wide awake J oe Ham t o make a vast improve ment in t he a ccura cy of the measurements being done on your job. J ust how impor ta nt measurements are can be shown by a typical example". Did you ever stop Io t hink about the mea surement t o an a ccuracy of a m illionth of an in ch? Measurements of this t ype are often made in t he missi le in dust r y. Pluck out one of the hairs from your head (or from the xyls if you have no hair) . Now t hat little hair is about t hree t housands of an ards and calibration are considered at t he de inch thick. If, somehow, you could split it 3000 sig n and engineering phases, a s well a s the t imes, into 3000 lit t le slices you would ha ve quality control a nd test phases of production. a millionth of an inch. Same thing as com The Army is doing somet hing about cali paring t he width of a dime to a stack of dimes bration in the Army missile business.T he twice as hig h a s t he E mpire State building. Atomic weapons business is, perhaps, leading Now if you mi ssed the measuremen t of certain the na t ion with t heir alert calibration pro bore sig hts in t he missile business by j ust g ram. These a re two areas tha t I can speak t hat much , t hat missile would miss t he moon for because I ha ve been up to my neck in t heir by 1000 miles.Yes, calibration is extr-emely programs but how about all the countless thou important and our nation is sadly lagging. sa nds of other major industries in our na t ion. The N BS is always f aced with a backlog and 'Ve know that the Russia ns couldn't have pr o ca n't find the necessa ry t ime to develop new duced the A-Bomb even wit h a shi p loa d of st a nda r ds and measures. our secret bl ueprints unless t hey had ex t reme A lot of companies la ck adequate lab or competence in the art of measurements based plant facilities and controls to house a cali upon a broad foundation of scient ifi c educa bration program. Many keep inadequate cali tion and research. A re they concerned with bration records with r esult ing loss of control t he science of measurements.You bet they over calibration intervals. Some , a s in Joe a re. Their Counc il of Ministers headed up by Ha ms case, don't even know when their local Khr ushch ev himself ha s a special Committee sta nda rds ha d last been recalibrated. The im on Standards,Measurement and Mea surement portant thing for J oe H am to r emember is that Apparatus . There are five r esearch instit ut es rf a nd microwave measurements is on the devoted to improving new techni ques of meas problem list. Specific areas in need incl ude: urement and ma intaining precise standards . average and peak values of pulsed microwave T hese institutes supervise the wor k of a lar ge power, attenuation, voltage standing-wave net work of ca libration center s, a bou t 129 of ratio, unmodulated microwave power. P ower them. The new Seven Yea r P la n to the twenty and attenuation measurements a cross the fir st Congress of the Communist Party calls whole rf spect r um actually la g t he state of fo r more than doubling these efforts by 1965. the art. P r ecision measurement of 8-C voltage Now, Joe Ham, this is some pretty stiff com a nd capacitance is another big trouble a r ea. peti tion. \Ve have about 1600 scient ists and 'Ve can't shoot for t he moon with a flintlock engineers, a ssisted by a simila r number of rifle. I mpr ovements in measurements capabili technicians, skilled artisans and mechanics t ies will ult imat ely be reflected in sa vings of within the U. S. Dept. of Commerce, called the many millions of dollars for our nat.ion.J oe National Bur eau of Standards, trying to offer H am can, perhaps, help more t han a ny other t his com pe t ition. They need J oe Hams help. seg ment of our nation. Go out to your job with If you will just take t he same care as you do a solid determination to really find out if all in getting on frequency out to your job the measurements show traceability to NBS. Even r esults wiII surp r ise you. If you know a better if you think you know, prove it to yourself. way to measure somet hing, tell someone a bout If there is a missing link, a broken link in the it. Become a "calibration crank" on your j ob chain--do something a bout it. See t hat stand- - your help is needed. . . . ' V4WQT APRIL 1961 19 The Big Connon t J e ck H oll oway W6VVZ 14607 Blythe Apt. 7 V"n Nuys, C"liforni" NOT lon g ago, several locals were holding a so we designed a K 'V amplifier which could be postmortem following- a OX phone con. built at a reasonable cost. In order to achieve test, when one of the gang insisted t hat we the reasonable cost st ipula tion, we sca nned the should build a BIG CANNON on 20 meters sur plus market seeking components for our for future contests. With maximum power, we vendon of a 20 meter BIGCANNON. could challeng-e the antenna farm and moun W hen we fi na lly unveiled the CANNON, tain top locations for difficult to get E uropean some of t he locals expressed enough interest multipliers, without having to move to an to cause us to believe that hams elsewhere antenna f ar m ourselves. Twenty meters, con might be interested too. Here it is. tinued our friend, allows the best reliable long Insofa r as a choice of a tube is concerned, haul communications most of the time. As a the once very popular 304TL still offers the result, it is the most competitive band with most plate dissipation, a nd the most long term t he most QRl\I, as every ham realizes. Ther e r eliabilit y due to its electrical and mechanical fore. power is the only practical means by ruggedness, of a ny tube on the market for the which we can hope to crack the QRl\1 and price.Wat ts per dollar it cannot be beat. That thereby increase our number of European con fact still holds true. Its 300 watt plate dissipa tact s. tion can withstand a terrific beating, and so Some of the gang wen t along with the power can the fi lament due to its tremendous reserve idea, a nd decided to build a new big- final-final. emission. It has the advantage, too, of not re At fi r st , t hough, it appeared as if we would quiring specia l consideration for easy to de need far more money for t he project than was st roy grids, as in a tetrode. However, since we a vailable to us. But we slowly ca me to realize worked unsuccessfully with the 304T L on nu that day dreaming about vacuum va riables, merous previous occasions, we were hesitant 1000 watt plate dissipation tetrodes, and silver to try it again; particularly in a single-ended plated band switching inductors is a luxuri final. Ti me and again we built single ended ously fascinating pastime, which does not get 304TL fi nals, only to have it operate errat any final amplifier on the air. We also came ica lly due to uncontrollable paresitics, and to the conclusion t ha t a DX st ation cannot de never did there seem to be enough available termine if the incoming signa l emina tes from drive power. Always, too, was the ever present silvered inductor s or just pla in copper. If the problem of attaining neutralizing that would signal is clean, it doesn't matter one decibel to hold from one band to another. So in the BIG the other end of the line, nor should it to you. CANNON we decided to try our luck with a Therefore, we decided t hat it is not necessary t ruly balanced push-pull final. By going push nor mandatory to spend a great sum of money pull, we figured that physical and electrical to build an effectit'e high powered amplifier; symmet r y would ca ncel out the st ra y inductive 20 7J MAGAZINE and capacitive effect s that caused ou r previous f or a n expensive ca bi net , and at the sam e t ime single ended fa ilu res. Two 304TLs seem like allows t he u nit t o be placed on a t able t op if an awful lot of wasted plate dissipation, but it should be decided to operate in that way. if one anticipates going- SSB, a push-pull class The t wo side panels, t op, bottom, and r ear AB, linear amplifier with s uffi cient power han s hield piece f or t he driver a re cut and folded dting capability is an attract ive id ea, especia lly from su r plus aluminum stock. The driver panel if this high powered capability can be had at and fina l panel are joined rf-tight by per minimum cost. ma nently secur ing a right angle strip of alu Another neutralization headache w ith t he mi num to t he bot t om edge of t he fi nal chassis 304TL is t he difficulty of obtaining neut r aliza so that t he t op back edge of t he driver panel t ion ca pa citors of suffi cient ca pacit y a nd vo lt ca n be secured t o t he r ight ang le st rip with ag e breakdown, yet compact in physical size, sheet metal screws. t hat wi ll perform without failure. W e pr e In t his fi nal-drlver unit, inexpensive wire viously attempted to use ever y kind of known sc reen mes h purchased from the ha rdware air g a p capacitor with no success, but t hi s t ime stor e is used for shi elding the back side of t he we tried ceramics, and t hey cont in ue to work fi na l compa rtment, wherea s the back side of perfectly. We f ou nd j ust what we needed on the driver com partment is closed in wi t h alu the su r plus market in some 7500 working volt, minum sheet so the unit ca n be pressurized . A 50 mmfd ceramic doorknob ca pacitors. W hen su r pl us blower from a Beachmaster amplifier six of these are screwed end to end in a pile, is used f or the forced a ir cooling. Not e that the total capacity is 8.3 mmfd which is within holes a rc drilled into the final chassi s deck di 0.3 mmfd required to neutralize the 304T L. rectly over t he 4E27, above the final a mplifier We figure t he 45,000 volt breakdown is more g rid leak r esi stor, a nd around t he porcelain than adequate. It is possible of cou r se to stack feedt h roug h bushings which su p port the stacks ot her combinations of ceramic ca pacitors t o of ceramic neutralization condensers in the attain the required neutralization value. For fin al. These holes allow ail' escape f rom the example : three, 10,000 volt, 25 mmfd ceramic pressurized d river ca binet sect ion and at the doorknobs would be a sat isf actor y s ubst it ut e, same time cool final amplifier components. a nd would be less expensive be sides being Cooling t he fin al a mplifier is not a necessi t y mechanically more convenient. I nsof a r as ob ,I taining s uffic ient drive power f or the 304T L, we decided t his t ime t o build the d r iver as an integ ral part of the fin a l, and to use an easy • ! t o drive tube t hat wou ld ha ve more than , . enough reser-ve plate di ssipation . \Ve f ou nd , ou r tube, a gain on t he su r plus market, in the 1 4E27. A tube that can be d riven t o full output • with one watt drive. A nother reason f or choos ing this tube is that it ca n operate at t he sa me plate potential a s the final, thus eliminating the requh-ement for an additional power s up ply. An a pproach toward solving t he 304T L parasitic problem is made in t he same manner, • a nd with the same degree of caution, as is done with t etrodes. First, the 304TL grid cap and internal grid leads are mou nted below the chassi s deck t o achieve isolation between grid and plate circuits. The internal grid collector To p view-304TL final. Fe ma le coal connectors ring is at chassis level at cor r ect mounting are hanging fre e from inside top of cabinet. depth. Second, the incoming and outgoing Bla ck knob on c hassis to!, is grid d rive balance power leads are isolated to minimize external control. coupling between grid and plate ci rcuit s. in any event, but it was spec ulated that cool Third, adequate shielding is used between grid air a round the 4E27 might prolon g tube life. and plate circuits. Last , the plate tank to H the u nit is t o be operated in a normally ground impedance is lowered to a minimum cool op erating room, 4E 27 cooling precautions value a t parasitic frequencies by shu nting each ar e unnecessa ry. end of the plate tank circuit t o g-r ound with a Because we had decided t o make it possible sur plus vacuum padding capacitor. These pro t o change final t a nk coils f rom t he front panel cedures ser ve another purpose, such a s the a n in order to f acilitate rapid ba nd change, a door nihilation of possible TVl, a nd t he improve is cut into the front panel a s illust r at ed. Snap ment of overall circuit effi ciency. clip s which r etain t he door are taken f rom a Mechanically, the final a nd driver are hou sed sur plus BC-375 tuning drawer, and t he re in one RF t ight housing t hat can be hung in taining r im for t he door, which is bolted t o an open frame rack. This eliminates the need the r ear side of the front panel, is cut f rom a APRI L 196 1 21 J discarded panel. The r ight angle reduced gear ends of the split winding coil. This is accom drive assembly for controll ing t he fi nal tank plished by removing t he two center banana swing -i ng link assembly is also taken from the plugs, placing a * inch wide st r a p of copper same BC...175 surplus item. unde r t he two center coil suppor t stra ps, bolt Since the sha f t for the final plate tank tun ing t he coil st ra ps and the copper st.ra p to inJ{ capacitor would appear through the front gether through the steatite bar, a nd using one panel wi ndow when conventionally mounted, of the removed bannana plugs as a B+ con a n around the back fence tuning system was nector to t he center of the coil. The modified devised using a pair of broadcast r eceiver dial coil is illustrated in fi g-ure X. \Ve are so satis string drums.Despit e a few raised eyebrows fied with t his more effi cient coil ar-rangement a t t his "antiquated" string drive technique, that coils for all ba nds have been similarly no fa ilure has been ex perienced since we first modi fi ed. accomplished a good tight st r ing ing j ob. ABe The 4E27 driver tube is mounted so that its drive wheel for t he shaft end of the B & \V plate ca p is located close to the final grid tank butterfly tank condenser has a %" diameter circuit. The perfcrnted shield around two sides hole, and is sweated onto t he brass shaft of the of the driver tube is mandatory. \Vithout it, bu t terfly ta nk condenser. The 'iV' thick alumi the stage is ex t remely difficult, if not impos num hracket supporting t he bushing and dr um sible to tame down parasitic-wise, and neu wheel, mou nted towa rd the rear of the left tralization is difficult to maintain. Although hand cabinet wa ll, is bent from an old panel. this was originally to be a 20 meter final ex Also, note t hat t he shafts used in bot h t he fi nal clusively, a B & W band switching turret as tank t uning and swing ing link systems a re of sembly is used in t he 4E27 grid circuit. and high grade insu lating' material. ::\l etal could the right a ngle drive for front panel control is be used, but the less power consuming material again taken from the BC-375 t uning drawer. nea r the final tank coil, t he better. The 4E27 grid turret assembly has a separ ate Plate tank coil s are modified from the or-igi a ir trimmer placed in parallel with each in na l to insure the highest possible efficiency. dividual grid coil. T he grid circuit is so loaded This type of im provement was discovered once by t he two series input g rid r esistors, that while working on a push-pull tetrode amplifi er, once the trimmer condenser for ea ch grid coil a nd t he measured increase in output power is is adjusted to resonance in t he center of each well worth noting. Usually, plug in tank coils band, no further t uning adjustment is neces are constructed so that t he high circulating sary when shift .i ng frequency across anyone current which fl ows within t he parallel t a nk of the phone bands. circuit is routed external to the coil right in Switching bands'? Yep. When we ventured t he high cur rent center point through two ba forth on this project, we kept in mind the idea nana plugs and jacks. Here, the circuit is more of adapting this basic design for use in other often than not completed wit h some small bit fi nals t ha t would be all band. F or that matter, of wire without regard fOI· the losses caused by we wanted a design which could one day be the high circula ting current. The net result, switched over with a minimum of lost invest of course, is loss of output power. In t his fi nal, ment to a fi nal t hat might use 4-250A's, or however, a copper stra p j oins t he two inside 4-400A's. Our foresight seems to have paid off, '. N... N • ~ , • M . .. _. ~ , .s:--:; -- •• t , _.• ~~- -_. '"";). -"_.. •_. - - p .. '. , _.• , , ,. , --, .- " - r._. .. :e."'" , _.• -, , - ~ :::.:- - , .J. , .., . ,. ~-ti • - -.. '" • -,. ~.. .,. --- U .. g;; •-• - -~ -_. .- _. ';; ..oo '" -- ,.. ... ~,T '" • " -.. - , , -;L ,iii- •• • • • -'" -.. " ,-'00 ' - , , _. ..-'!,... 00' _. .. s: - 1.'-' -... - • _. ~' --, II ...... _-.._-' ''' ,.....- ~ - ' _M O. • .. ... '_M .. "' -, -.. .. -__- - • • • .... _... --,...... --..- -- ...- ,-- ... ' 0 ' 10 - . -= 22 73 MAGAZINE since t wo other finals have been built utilizing t his identical approach. One of these other finals uses a pair of 304TL's, and is a truly all band rig with a n l\IB-150 all band tuner for the grid circuit. In another version, the driver stage is eliminated and a pair of 4-250A's is used in layout identical to the 304T L rig, but with an MB40 all band tuner for its grid cir cuit. The 4E27 driver in the 20 meter only BIG CANNON is neutralized for stabilit y, but in the all band version of this rig, it was found to be unnecessary. Parasitic suppressors a re r equired in both plate and gr-id leads of t he 4E27 stage for absolute stability. The RFC in t he 4E27 pla te circuit is homemade and functions without r esonant effects on all ham bands. Its specifi ca tions are given in the schema tic. Screen voltage for the 4E27 is supplied through dropping resistors R1 and R2 from the 3000 volt plate supply. The adjustable t ap on Rl not only controls screen voltage, but also final amplifier grid drive power. Once the slider tap is set for adequa te final grid cur rent on 20 meters, it need not be adjusted further. Since this is primarily built as a class C A::\I rig, no fixed bias supplies a re used. • • • Consequently, in order to protect the 4E27, a ....L '~ ... ,>,- .. 6L6 clamp tube is used with a 2500 ohm r e Front view- 304TL final. Coil access door is re- sistor between screen and plate to give im moved to show 20 meter coil in place. C ontrols. proved clamp tube operation. The final is pro top to bottom, left to right: plate tank tuning. swinging link control, grid tank tuning. and un tected from loss of exitation by an overcurrent used grid bandswitch in the 4E27 driver. relay located in the HV power supply. Grid and plate meters for both driver and Achieving' equal grid drive to push-pull cir- final are mounted in a standard meter panel cuits is imperative in order to r ealize t he full external to the driver-final unit. Therefore, as benefits this circuit has to offer . To attain bal. a safet y precaution, 100 ohm r esistors com a nce, a 15 mmfd variable capacitor is con plete meter to ground circuits. within the en nected between ground a nd t he grid of the closed cabinet. These are needed in or der to 304T L which is not ca pacitively coupled to maintain completed circuits even if the cable the 4E27. T his adjusta ble capacity allows the interconnect ing the meter pa nel and driver input capacity to the 304T L's to be balanced final 'cabinet should be inadvertently discon by offsetting t he output capacity of the 4E27. nected. "~ithout these resistors, for example, In t his manner , drive power to t he final may full plate voltage would appear between final be equalized. Approximate ba lance may be ob filament transformer center tap and ground tained by noting the color of the t wo final plate should the final amplifier plate current meter t ubes, and adjusting the capacitor in sma ll in be accidently removed from the circuit. crements until their relative color a ppea rs to Because the stack of ceramic capacitors does be equal. A more precise way would be to in not supply quite enough capacitance to com dependently meter the cathodecurrents of each pletely neutralize the final circuit, a slight ad 304TL, and balance t he t ubes "by ' obta ining ditional amount is gained through the addition equal plate and grid current readings. ' of alumnimum trim tabs. These tabs have a The 50 mmfd vacuum padder con-densers 6/ 32 inch hole drilled through them which shunting each side of the fi nal ta nk butterfly allo ws the tab to be held in place between t he condenser to ground ser ve severa l pur poses: ceramic feedthrough insulators and the bottom One, t hey help keep high order ha rmon ic fre of the ceramic condenser n eutralizing stack. quencies bypassed to ground-thus helping eli The size of the tab is not critical, and may be minate possible TVI. Two, they serve to keep cut to approximately 2 inches tall by 1* the plate ta nk circuit balanced in r espect to inches wide. Fine neutralization adjustment ground. Three, t hey add enough ca pacity to may be had by slightly unscrewing the ceramic the butterfly condenser so that it is possible condenser stack from the ceramic feedthrough to attain a loaded Q of about 20 on twenty insulator screw, and changing the relationship meters. A Q of 20 is about optimum for ease of the flat side of the tab in relation to the of loading and for allowing some degree of 304TL plate. harmonic reduction. APRIL 1961 23 Note that two 4700 ohm, 2 watt resistors are line and fi nal tank. The improvement in out a dded in parallel with the final plate tank put power transfer is well wort h the trouble, RFC. The only RFC we had was a n old Na but for all-band operation, t he technique is ob tional R-175 ; due to its poor design, and circut viously too cumbersome. Length of t he lh conditions, it was necessary to dampen out an wave, 52 ohm coax balun is 22'-9%". erra tic pa rasitic voltage that a ppeared and This final has operated many continuous burned out t he bottom segment of the wind hours without com ponent failure or break ings. It is probable that this would not happen dow n. More important, even though operated with the newer versions of the R-175. on the shadow side of a hill a way from TV Neutralization circuit parasitics always seem stations, t here has never been a recorded case to be present in 304TL a mplifiers, and in this of ha rm onically ca used TVI. Washout cases one it is necessary to have both t he 40 ohm have occurred, but t hese have been easily cured non-inductive resistors and t he Ohmite PC sup with a high-pass fi lter. Operation-wise, like pressors in order to completely clean up all the two subsequent copies refer-red to above, tendencies for t he fi nal to take-off. In t he it is a dream. Loaded and tuned in t he middle 304TL all-band version of this final using the of the 20 meter band, no further adjustments ME·150 grid circuit, only the P C suppressors are necessary when moving from one edge of are needed. the phone band to t he other. Testing of the driver a nd fina l for stability As fur t her comment on the practical ver and la ck of pa rasit ics is accomplished as fol satility of t he finals' design, owners of com lows :T hree, 200 watt, 1000 ohm r esistor s are mercially built 100 watt output exciters can placed in series bet ween a 300 volt power sup use t he 304TL amplifier without need for t he ply and the drive r a nd final (driver and final 4E27 driver stage. The fi nal can be driven to HV inputs wired together) . The cabinet is of full legal input by 100 watt of exitation and course, grounded, no rf input is applied to the high level modulated in class C, or operated driver stage, a nd no dummy load nor antenna as a class AB 1 linear amplifi er with negligible is coupled to the final output link. Actual fi nal required driving power. plate dissipation under these conditions will be near 300 watts per tube. A sensitive inst r u For Linear SSB Operation ment such as a n oscilloscope, or an a ntenna Li nk couple di rectly into the fina l grid tank. scope, is connected to t he fi nal output link as As is the case with my particula r final , a separ an indicator , and the fi nal plate tank tuning ate link must be wound with insulated wire and final grid tuning are carefully t uned and inserted into the final grid tank. When through all possible t uning combinations. No an MB-150 grid tank circuit is used in t he output signals will be indicated when all is final, the problem of link coupling is simplified. functioning correctly. Use regulated fi xed bias on the 304T L's.Re As t his is conceived as primarily a 20 meter move all power from the 4E27 driver stage. only fi nal, we decided to add a lh wave balun Operate the final in class AB·l, and it will across the output link to improve loading and drive with negligible drive-power required. matching conditions between t he 52 ohm coax ... W 6V V Z New Use for Crystal Socket Roy E.Pafenberg Despite sever al years popularity, power tra nsistor sockets a re still difficult to locate. A socket which is ideal for power transistors The power transistor is not strictly a "plug-in" is widely available. This socket is designed to device since the mounting screws and insula accapt t he small, hermetically sealed crystal tors are required. However , socket connection units that have become so popular in Citizens to the base and emitter is a convenience and Band and other equipment. These holders have worth the cost of t he socket . a pin spacing of .487" and pin diameter of Photo . .. Jim Gardner .05". This is in fa irly close conformity with t he t ransistor pin spacing of .43" and pin dia meter of .04". The socket easily accom modates t his small disparity and snug seating with good electrical contact is obtained. The photograph shows a crystal holder socket installed on the t ransistor and a view of the socket. It will be noted that the unit is designed fo r under chassis mounting.The socket will flus h mount in a 3/32/1 chassis, al though its use is not limited to this t hickness. Many manufacturers make these sockets a nd the Millen Type 33302 is typica l of those avail able. 24 73 MAGAZINE Eight Little - Nine Little Groy Berry K2SJN Communicotio ns C lub of Tenne ssee Indians New Ro chelle , N. Y. NE of the hardest-working- committees of hearing- your CQ over Mel Allen's mellifluous O T he Communications Club of New Ho tones. Tell him what's and why's in words of chelle is, unfortunately, the TVI Committee. one syllable. Lose his train of thought and In a way, we've a sked for it by carefully plac you' r-e on the way back to an angry neighbor . ing stories in t he local press from ti me to ti me So much fo r the first of our ten little in telling fellow-residents how and where t o r e dians. port Ten nessee Valley I nd ia ns- not t o mention "You're an anuiteur; my profeeeionnl eer oice their close tribal cou sins, the hams that breaks mnn told mc...... into a hi-f set , or is picked up on the telephone Now here is a r eal curve ! Because the ser without benefit of hybrid patch. Which means vice man told the TV set owner that nothing that our committee has been able t o compile could be done a bout interference (Don't laugh a fairly fat file of case histories on interfer - plenty of them wiJI do just that !) you are ence. now on the spot doubly. In the mind of the set T her e have been many articles, more t han owner , you are at fault (naturally) a nd Mr. a few books, a section of the ARRL Handbook Paid-for-what-he's supposed-to-know has sa id and so on a ll dealing with mechanics of in ter nothing ca n be done about it. Of course, you ference su ppression at the transmitter, or in know better, but how to tell the TV set owner the TV set. Most hams aren't on the air very without r efl ecting on his judgement? long before t hey r un into the need for this ma w e've found one helpful come-back to t his terial. There is no intent in the present arti one. "Mr. Madguy, the Olympics were just cle t o deal with such matters as low and high held in Rome (or the tennis matches at Forest pass filters, shieldi ng, st ub antennas and so Hills, the Golf Cha mpionships at the local forth; what we think may be helpful is a list count r-v club or what have you.} Those com of some of the remarks that are thrown at our petitors wer e all amateurs simply because they Committee by more or less (usually less with a don't g-et paid for their skills a nd knowledge. capita l " 1."-1) understanding- neighbors-and As a matter of fact, amateurs developed TV possible ways t o cope with them. in t he first place. A mateurs made the first Probably t he most common accusation is cross-ocea n shor t wave contacts, first coast-to worded more or less like this : coast short wave, etc., etc., ending up with "Yon're delib erately interfer ing w-it h my "Moonbounce" and " Project Echo". The only llU 'l game" This usually occurs in the last h alf reason we're called amateurs is because t he of the ninth, score tied and t he winning run Fede ral Government that gives us our licenses on base-no matter what the hour.) says we ca nnot be paid in any way for what Assuming that the TV ow ner is willing to we do. (Careful, now!) We have to pass an listen, we find an answer like this 11I u-y calm examination before we ca n go on the air; not the sit ua tion. very many ser vice men take a ny test at aIL" The ham sa ys : " Mr. l\-Iadguy, look a t it this So now you know something after all, in t he way. We hams are on the a ir to try to reach mind of your irate neighbor. Next step is to ot her hams. They.. are listening on the parts convince him somet hing can be done about his of the radio bands where they expect to hear TVI. By the tim e you've had even two com other hams. And that's where t hey are send pla ints, you'll find one t ha t has been cleaned ing out their calls. So why would a ham go on up to the complete sat isfaction of t he set the ail' on a frequency where no one can hear ow ner. It's a sma rt move to ask him if you him or call him? Besides, if we g-o on any ot her ca n have a ny other set owner check as to the freq uency except those that the F CC assigns success.If you once have one or two pleased to us, we face loss of license, a fine and even a complaints, the r est is easy. Just refer your jail sentence." latest TV owner to one or two other s in t he So he ask s " Then how come I hear you?" neighbor hood . . . a nd to the sets you know And you have the cha nce to expla in qui etly a re clean next door, or in t he sa me building. a nd cal mly (because he m.ay be honestly in " See, t here's proof of what I 've been saying; terested in fi nding out !) all a bout signa l r ej ec somethi ng- can be done." t ion and so forth. But a word of warningc- Indian N umber Three-HOf course, it's YOllT shun t he "snow job" to show how much more f au lt ; I never had any interference before 2/0U you know than he docs! He still doesn't like ]Ju t f ha t fhilly on til e uirl" A PRI L 19b1 25 Ask him to think about it this way; suppose job. Use the first fact to avoid the second. he has a hole in his roof. So long as the sun Don't get your fingers into the goodies. Leave shines, he doesn't even know it's there. But let it to the ser vice man. And if your neighbor is the rains come, and that self-same hole lets adamant about not spending a cent, tell him in the water. If it doesn't rain for months, the you'll see that he gets the fi lter as a courtesy, roof is still going to leak as soon as the rain and that your responsiblity ends there.E xit does fall. And a TV set that will let Inter gracefully (if possible) and go on the air when ference creep in is just like that roof. If it you please. E ventually, he'll fi gure that he has isn't your station, it will eventually be some the fi lter, and he might as well install it. As a one else's. What you want to do is to plug ma tter of fact, if you show him how easy it the hole before the rain comes. is, Mr. Madguy just may do it to save the At this point, you're ready to talk about the dollar or two he's so wor- r -i ed about! But don 't set makers and the way they will supply a HP you do it for anyone less closely related to you filter. So you tell the TV owner you can get than your landlord or your wife's Cousin him the filter by working through a r egular J ake. service man or your Club TVI Committee (you Fifth Lurking Redskin- "You must be in should have one-both a club and a commit ierierinq; my TV loo ked (solwded) awful last tee) . This invariably leads to Indian Number nightl" Four. J ust maybe you'll be lucky.Last night may uTI'hy should I spend a cent? You do it." have been the night you fried your fi nal (these (Pay for the service call, or install the filter.} things do happen) Or maybe it was meeting You see, the TV set owner has, in his own night at the Club. Anyhow, quickly explain the mind, pa id the last cent he expects to for the log and wha t it must show by law. Prove you best TV he can buy. Now you're telling him weren't anywhere near the mike or the key if in effect that he's been had-c-or so he thinks. you can-and half your battle is won. Then And wait until your TVI complaint comes from try this. " You know, there are many things a man who works for the set maker! besides ham stations that can interfere with a You have to assume (dangerous!) that 1\1r. TV set, but hams usually get the blame. (You Madguy can still be logical about this, but can't duck it if she or he has heard your call here is a tried a nd trusty answer. " You can signal, bub :) I'd like to help you find out what see from what we've been saying that the fault is interfering with your set . w hat does the isn't with my transmitter, because the FCC interference look (sound) like?" Many times would clobber me in a minute if it were. So you can identify its source-like a fluorescent what you're asking me to do (pay for a service light in the next room that drove our commit call) is not only to get you free a $5.95 piece tee bats for a while, or cars goi ng by. Look of equipment, but then to pay for putting- it around for a second set in the house that's where your set maker should have in the fi rst beating against the one complained about----o r place. You see, the FCC (the more you can men an F M radio. And try to describe "typical tion Fox Charlie Charlie the betted) says that amateur interference patterns" so they can the TV set makers knour they should do this, but compare your description with what they have they take a calculated risk. Out of the thou on their set.You may end up with a clean bill sands of sets they make, how many do you of health. (The ARRL publishes " Patter ns suppose might land, like yours did, near one of Interference"- a chart you can get for the of the 200,000 ha ms in the country? And a asking.) filter that might cost $3.50 at the factory, Sixth Indian from the neighborhood war installed, could raise the final cost of the set as path is " lVhat d'ya mean it's my set?" much as $25.00 or so by the time you figure " Well, 1\1 1'. Madguy, I have two sets home. in labor , mark-up for the Distributor , the One is right in the same room with my t rans Dealer and all the other people who get into mitter and nothing interferes with it. I'd like the sale.That's why your set needs this fi lter to ask you to come over and see for yourself. -just l\ matter of economics. And since you (Better be sure your own TV is clea n !) And are going to get the filter free from the set I'd like to show you how a ha m station is built maker, doesn't that prove he knows his sets and filtered so that it won't cause inter ference. are not as perfect as they might be? P utting (In the rare event t hat he does come over, the filter in only takes a couple of minutes, con trast the shielded chassis of your rig with and there won't be a ny parts charge, just a the open constr uction of TV sets. Compare co service call." ax with TV wire and lead-ins. Show him your This leads to the other related question; low-pass filter and explain it in layman's lan " well, why don't you install it?" If you want guage--of course you have an LP filter in the to take a chance, go ahead. But we don't rec line, don't you?) If he won't come over-quite ommend it. First of all, let anything go wrong likely- talk him through what you would show with that TV set for the next six months, and him. Then add on as many cases as you can who do you think will be blamed? Second, f rom the neighborhood of TV sets tha t aren't your neighborhood servicemen get touchy if being interfered with while h is is bothered. they think you're doing them out of a service (Continu ed on page 59 ) 2b 7J MAGAZINE Bill Roberts W9H OV House of Antennes I r53 Eest 82nd Street Measuring Chlceqc 19. Illinois Co Ax Feeders and Stubs ECENTLY a brainstorm sent me into inti 11 feet 4 inches. A quarter wave st ub would R mate consultation with a full set of ha nd be 5.68 feet (5'-8"). It is interesting to note books and a slide-rule. This resulted mostly in that a line 45'-7" would be 4 % waves on 10, sever a l pages of calculations and a desire to 3% waves on 15, 2 half waves on 20 and one do something else less mathematical. The half on 7 me, antenna never did emerge from the confusion In multi-band antennas it is often advan of figures, but an interesting chart did. tageous to have a feed line t hat is % wave This chart shows the length of a half wave long. If you can choose a feedline that is % In free space, the length of a half wave of wave long on each band you may solve many co-ax such as RG8/U. RGll/U. RG58U. or problems. As you look down the chart you any other co-ax having a velocity factor of will see that there is a length around 45-46 0.66, the length of a quarter wave of co-ax feet that works out to be a half wave mult iple (half the former, of course), and a multiple of on all bands. The C\V operator would be more half ' ..-av es that will give you an all-band co-ax interested m the 46 foot length, the phone feeder. man around 45.4' or so. Now let us take a hypothetical case and see This chart is for co-a x, not for open wire what the chart will do for us. A half wave lines or twin-lead. feeder for 28,600 kc would be 11.35 feet, or ... W9IlOV 28000 28100 28200 28300 28400 28500 28600 28700 28... 28900 29000 29200 2.... ~ 2 Wave . . • . . 17.57 17.51 17 .45 17.39 17.32 17 .26 17.20 17.14 17.08 17.02 16.96 16.90 16.84 ~ !l W a v e Coax 11.60 11.56 11.52 11.48 11.43 11.39 11.35 11.31 11.29 11.23 11.19 11.1 5 11.11 ~;. Wave Coax 5.80 5.78 5.76 5.74 5.72 5.70 5.68 5.66 5 .64 5.62 5 .59 5.57 5.55 4!2 Waves . • . 46.40 46.24 46.08 45.92 45.72 45 .56 45.40 45.24 45 .08 44 .92 44.76 44.60 44.44 21000 21075 21150 21225 21300 21375 21450 ~ 2 Wave . ... • 23.42 23.35 23.26 23.18 23.10 23.02 22.94 % Wave Coax 15.45 15.41 15.35 15 .30 15.25 15 .19 15.14 ! ;. Wave Coax 7 .73 7.70 7 .68 7.65 7 .62 7.60 7.51 3!!l Waves . .. 46.40 46.24 46 .08 45.92 45.72 45.56 45.40 14000 14050 14100 14150 14200 14250 14300 14350 ~2 Wave ..... 35.14 35.02 34.90 34.77 34.65 34.53 34.40 34.28 !:z Wave Coax 2.1 .19 23.11 23 .03 22.95 22.81 22.79 22.70 22.62 !~ Wave Coax 11 .60 11.56 11 .52 11.47 11.43 11.50 11.35 11.31 2 \2 Wave ... 46.40 46.24 46.08 45.92 45.72 45.56 45 .40 45 .24 7000 7025 70'0 7075 7100 7125 7150 7175 7200 722' 7250 7300 7350 ~2 Wave .. ... 70.28 70.04 69.80 69.54 69.30 69.04 68 .80 68.56 68.33 68 .08 67 .84 67.60 67.36 ~ 2 Wave Coax 46.38 46.23 46.06 45.92 45.72 45.56 45.40 45.24 45.08 44 .92 44 .76 44 .60 44 .44 !:a Wave Coax 2.1.19 23.11 23.03 22.95 22 .81 22 .79 22.70 22.62 22.55 22.46 23 .38 22.30 22 .22 Ohmmeter Polarity Test Moat multimeters are wired so that the swit ch to the de voltage range, and reconnect black lead is positive and the r ed lead negative the capacitor and see which way the meter when measuring ohms. But not all are wired needle ki ck s. that way. \Vhen testing diodes and electrolytic This sa me charged capacitor is frequently capacitors, it helps to know for certain which used to a dvantage to measure de voltages in way particular meter you grab is wired. If ext remely high impedance circuits. The capaci you don't happen to have a second meter to t or is connected t o the circuit ( throug h an test the polarity, you ca n use a common potato isolating resistor if needed) and allowed t o to determine which lead is plus. The plus lead build up to a full charge. Then a VTVl\I or area turns bluish after a bit if you stick both de Scope is connected to the capacitor and the leads into the spud. rea ding quickly made before t he charge leaks A much better method is to si mply use the off. Natura lly a good capacitor is essential, ohmmeter to charge up any capacitor, 0.25 such as a mylar or polystyrene type. mfd or larger, then disconnect the capacitor, ••• KGEAW APRIL /96/ 27 Automation Jim Kyle, K5JKX/6 Il'itl. a V'enq eance l ! 1\ s I opened the door t o the shack, Joanne 1. T u rns itself on and off. ./"""1. put down her well-chewed pencil and 2. Monitors for Conelrad alerts continu turned off the big' s witch. " Yes, inventor," she ously. said , "I see you're home." 3. Takes care of all transmit-receive "Rough day at the salt mine," I grumbled, s witch ing. si nki ng my lank)' frame down g inger ly on a 4.Cha nges bands a ut omatically. box of old a04T Ls. "Too nin ny computer cir 5. Tells you what's ha ppening at all cuits... .." t imes. "You'd think," mused friend wife to no one and G. Keeps the log. in particular , "that with all the g ray matter Those were t he design s pecifica ti ons, and this eat's supposed to have, he could fi g ure out they were all met. It took a bi t of doing, and a way t o make a st at ion do all its own d irt y many of the circuits a re not t he familiar ones work. After all, they ha ve machi nes t hat build yo u're used to seeing. more machines. ..." If you're ready for the s hock, t hough, take " Yeeow!" I cried, leaping to my f eet. A a peek at F ig. 1. It's a combined block and 304T L had given way. B ut even after the log ic diagram which shov..-s t he overall pict u re su rgeon removed the last splinter of g lass from (and when one of t hese is finished, overalls my posterior, the memory of J oa nne's sug will be the on ly t hing; you could afford, but g-estion stayed with me piercingly. that's ahead of the st or y . ..) in a more-or Three reams of scra tch paper, two g -ross of less underst andable way. pencils, half-a-d ozen editions of T er man (and The big X in t he upper left ma rks the s pot t wo jobs) later, t he evil deed was done. A where a switch goes. This is no ordinar y complete ci rcuit for a fully-automated ham swit ch, though.You kno w these mat-type f oot station repcse d in my mind. It ha sn't ye t been s wit ches that work by pressure ? T ake one of transposed to r eality ... for reasons which t hose and put it under t he cushion of t he chair sho r tly will become clear. But it ca n be done, in the shack.... Now, whenever you sit down, a nd you're welcome t o it if you want to try. t he st at ion t urns it self on. Before I send you muttering; back to t he There, t hat was n't too painful, was it? Now crystal-set lea g- ue, t hough, (and above all r ead on to the right unt il you come t o t he box don't dare look a t t he schema t ics yet!) I marked "20 sec 'I'D." This houses a zu-second guess I'd bett er outline what this su per-du per time-delay relay which dela ys ope rat ion of the station will do for you. Like she said, it does t ransmitter bia s su pply until a ll filament s all its own di rty work. E .G .: have had a chance to heat. Skip t he box marked u'vwv Revr" for the mo ment and concentrate on the one labeled " C. R." In its con fi nes nestles the Conelrad aler t monitor . I nstead of t he ordinary system of buzzer or pilot light, the ou t put of t hi s alarm is j ust a. S P DT relay. When a ll is we ll, the " G" outp ut line is con nected to - 12 volts. When t he aler t sou nds, the - 12 voltage is switched to t he " R" line. Now move on t o the "Tape Log" box. This hou ses t he much-modified tape r ecorder.The tape recorder has t wo in put s, as well a s an aut oma tic stop to halt it when it r uns out of tape, and a r elay in its B + line which switches - 12 volts to eit her the "On" line if a ll is working 0 1' t he " Off" line if somet hing f ails. Back to the bias su pply. It, too, has one of these little r ela ys, con nected in a voltage-sens i n ~ circuit so t hat - 12 volts is on t he " On" output line u ntil bias rises to rated value. At that point, the sig nal swi tches t o the "Off" ou t put line. We ski pped the "WWV Rcvr" before. Go back. This ca n be any addit ional receiver (a command set will work but a 5t.} is r ecom mended) which will pick up WWV. With it s own antenna , it is permanent ly tuned to 28 13 MAGAZINE - :x 1=1 D. lsa 1m - ~ ;,;;, " I --$t I ~ ~ I ~ Il '" '-- -~ III (l ~ ~~ , . , ,- ~ s ' (J o o o o @ @ @ ,,'wv. Output feeds one of the inputs to the The fault locator panel consists of red and logging tape recorder, providing time markers. green pilot bulbs slaved to the enabling-signal We're almost up to the transmitter itself lines. .:\ly out-of-this-world dreaming did it by now, and the whole confusing mess is about with transistor switches at each of the 13 to get really uncomprehensible. At this point, bulbs, but it might be cheaper to use DPDT you have to open or close the gates. relays instead of SPDT in each signal line and The gates, that is, which control the trans control 6.3 VAC for t he pilot bulbs with the mitter.They're "and" a nd "or" gates, swiped other relay pole. from digital computer circuitry (it's cheaper The "Operate" section on the panel, you may to swipe them-the commercial models cost notice, is connected to the out put of the big $25 each!). The smaller "and" gates can be "and" and the "or" gate. If all is ready to built in the sa me manner by omitting two legs. transmit, the "oper-ate" bulb lights green. If Note that each gate includes a -6 vdc sup there's any failure, it lights red. If this bulb ply, so that in the "and" gate you have to is red, at least one other will also be red, have - 12 at each of the input terminals be pinpointing the t rouble. After a few months' fore output voltage will rise to - 6 from zero. practice, fault location with this system should I n the small gate driven from the la rge one, be almost as fast as by the old try-everything replace t he 6-volt battery with a 3-volt one. until-you-fi nd -wha1'8-wrong technique. Now, after J-·OU sit down (automatically So far, we haven't looked at the " Band starting the cycle), the bias supply comes on Switcher." It 's a flip-flop connected so that after 20 seconds and the Conelrad and Tape when the transmitter is on, no signa l can get Log equipment sends out "G" and "On" sig through to a stepping relay which oper ates nals respectively as soon as warmup is over. sla ve relays in each stage of the transmitter. Assume that the "Band Switcher" also has If the transmitter is off, the input "and" gate -12 volts on its "Locked Sig" output line, and is enabled, and you can pulse the stepping you can see that the first "and" gate in the relay (approximate cost, $45) with a push transmitter control chain is enabled. T his puts button on t he arm of your chair. This steps - 6 volts at t he input of "and" gate No.2. you from band to band. An a dded r efinement \Vhen it gets another - 6 volt signal from the would be a series of pilot lights to let you vox unit, you're on the air. know what band you're on, but I felt it would On the other hand, should Conelrad sound be a useless complication. an alarm, the bias supply fail, or the tape log Note that the "Band Switcher" is connected unit run out of tape, one of the enabling sig to the transmitter coming and going, so to nals will be absent. In addition, a failure spea k, so that the transmitter must be off signal will go to the "or" gate in the disabling before it can be turned on. This is a precaution side of the transmitter control, a nd you're against accidental doubletalk. For intentional silent. (Continued on pag e 58) APRIL 1961 29 Art Korn K8 HDR 4212 17th Street W yandotte. Michigan Audio Boosting The Command Receivers OME time ago I needed a receiver that was Do It Yourself S light weight and portable. Not wanting to carry around the 60 pounds of station receiver, Remove the screws that hold the two mul a BC-779, I decided that if the audio of a tiple condensers C20 (2X.05) and C16 command receiver could be improved enough (3X22mfd) and the audio choke (L15). Lo for spea ke r operation that it would be the cate R19 (lOOK) and R18 (5l0K) under the right size and weight. Al so, the BFO was two condensers on the terminal board and r e needed for C'V reception. A check thru all move. The green lead that goes from these the old magazines and handbooks brought little resistors to C29 (.OOGmfd) should also be re of help to light. moved. Solder a shielded lead to this con For portability the power supply had to denser, ground the shield, and loosen the be on the dynamotor well and be transformer screws holding the other condensers on this opera ted for sa fe t y. This left no extra r oom side of the chassis to run the lead to the front for an additional audio stage. panel. You might a s well take out the coil It didn't take much sta r ing at the circuit box across the front of the receiver at this .dia gram to see that the reason we were not time. Leave this lea d long enough to fasten .get ting much audio out of t he receiver was to a volume control which will be on the f ront that it was designed to feed a n external audio panel later . The af choke (L I5) a nd its wir .system or a pair of head phones. Simply by ing might as well be taken out completely too. .cha nglng t he output circuit a bit and using T he black lead at the j unction of the resistors .a regular output transformer we could have should be pulled back to the if can pin and .plent y of decibels. removed. Replace this with a shielded lead, • The only changes necessary are where new leeds should be connected at points A-B-C . ",. --- 0<>< --- T2 eoooJ\ TAP = TO Ll2 .'",. ~- 1.~1( 12$R7 "" "*'0.'''' ."100 12A6 = .••~ , TEL LINE TO J3 @-:;r-r, I PARTIAL NEW SCHEMATIC ., 5000 TO , 7500.n. 12A6 0 - -&• - -+ ,. = 73 MAGAZINE ground the shield at t he term inal board, a nd thru a convenient hole or to the unused run t his lea d t o the f ront pa nel also.T hese pins on the power socket. Mount a one meg leads should be insulated f rom touching t he pot on the front panel a nd solder one lead sockets and ca using an a ccidental shor t and to the center post, one to t he end post, and onl y need to be insulated because there is no the shields to t he thir d post.T ighten down voltage but some BC pick-up due to the leng th all condensers, coils and BFO can securely. a nd broa dness of the if's. 'Vhile you are under the chassis it might Re-fa st en a ll the condensers and go to the be well to take out the neon bulb across the other side of the receiver.Loosen the screws antenna trimmer. I found this helped con that hold t he BFO(Z4) and C I5 (3X.05) a nd aider -a bly. I left the old gain control in :'1 3 output t ransformer Tl. Remove t he plate lea d this helps to cut down background noise .m a t t he socket of t he 12A6 and B plus lead CW reception, but it can be taken out if f rom the power connection, and C31 (.001) . desired. Remove the w ire to t he phone j ack, move all grounds f rom the phone jack to a direct Did it Work? chassis ground installed at this time in any convenient spot at the side of the chassis, and Now tie on a speaker , turn on the power, remove the phone jack. T his is where you will and grab somet hing for an antenna. As soon put your volume control. as it warmed up, sig na ls began to bounce Now start put t ing a few parts back in! A thru t hat I had never hea rd with t his r e sma ll 5000 to 7500 ohm to voice coil out put ceiver before. I tuned t hr u t he 80-75 m eter transformer should fit in where Tl wa s t aken band and found t he results of this little out.Be ver y careful when you move t he BFO change were most gratifying for the time, can and the condenser out of your way since parts, and effort consumed. For a sta nd-by these leads break very easily. Solder in the receiver or for the Novice just getting st a r ted plate lea d of the output transformer to the it is a truly fine receiver to work with.I t plate of the 12A6 a nd the B plus lead to the is a little broad in the if , but curing that is power socket. Run the voice coil leads either a nother story. . .. K 8HDR APPRQlW.. 4.T ELl S<; PE W. L YES OR 3FOOT ~'P'E OR / E l'E BOLTS WOODE N OOW'EL EXTENSION TO ~ ....sr . ./ "..YLON GUY ,r ,/ CLAMPOR Pic k Up the INSUL ATORS ..: : EYE BOLT/~ RADIATOR " ;~~~~~ ;; ~f- c:: <;CONVENTIONAL ELEMENT "MOOP" 'D I roop • MAST ETTIN'G a bit t ired of the "down-in-the G mouth" look of the drooping elements on your rotary beam antenna? Next time you have to service it or when you erect a new one, put a short extension (approximately 3 Use Nylon g uy cord (any radio distributor) feet ) on your supporting mast. This can be which is non-shrinkable, non-stretchable and of metal or wood, as you elect. Most lumber of excellent t ensile st r eng t h. Avoid wire of any yards car ry wha t is known a s "full r ound" kind for such g uys; it could upset your radia stock in several diameters ; one will probably tion pattern! B reak the Nylon cord with a fit your mast. If not, a little shavi ng will fix sma ll 'goose-egg' insulator close to the ele it. ment. Inser t a small galvanized turnbuckle, if Ordinary screw eyes (galvanized) in a you like, close t o the t op anchor of the guy wooden extension or t he eq uivalent in eye lines. Glass line is also excellent for this. bolts for a metal pipe, placed at the top, will Pick up the d roop in each element this serve a s t he upper anchors for t he g uy lines. way; your beam will present a much m ore Drill through t he rod elements nea r t he outer workmanlike appearance and the addition of ends to provide a n anchorage for the guy lines such guys will stiffen the entire assembly sur by means of a n eye-bolt or use a wrap-around prisingly. It's weight is negligible and the cost clamp such as sold by most hardware stores is peanuts. for plastic pipe. Heward S. Pyle W70E APRIL 1961 31 Transistor Modulator Forty If/t/!!s Monroe McOoneld Kl7DlC T H E unit I a m going to describe in t his ar- micropho ne, converted to us e a \Vestern E lec ticle is a very effi cient audio amplifier sui t tric Fl telephone button. able for use as a plate modulator for a mob ile The modulator and power su pply, plus all or portable medium power (sixty to ninety the a ssocia t ed relays, fi lters, etc., are mou nted watts r f ) t ra nsmitter. T he audio output is in a box about ten by fi ve by fo ur inches, wi th rated at fo rty wa tts, but the u ni t has delivered t he modulation t ransfor mer sticking out on in excess of sixty watts to a dummy load. No top. The driver transi st or and microphone a udio quality tests were made at this power transformer are included in the r f section of level, though. Wit h no filaments to heat, the my rig, however, because t ha t is where the unit need not be energized during st a ndby mike plugs in, and I wan ted to reduce mike ( receive) periods, so there is 110 standby drain. lead line pi ck up. When the unit is energized during transmit The mod ulat ion circuit is very simple, a nd per iods, t he idle d ra in is less than half an t herein lies one of its virtues. The construc ampere at twelve volts, and the drain at full tion is nearly all mechanical, with not much r ated output (forty watts) with a sust a ined wiring to do once the transformers and tran tone is less t han eight amperes. sistors are mounted.I did mount a termin al The u nit as I use it is built into a power str ip near t he driver t ransistor to provide tie supply-modulator unit , with a 600 volt 200 mil points for t he components in t hat part of t he transistor power s up ply, so that plenty of circuit . "punch" may be su pplied to a single 6146 rf One unfortunate a spect of this u nit, or a ny section wit hou t st ra ining. The power su pply using recently developed components, is that uses a Tr iad t oroid a nd the cir cuit supplied the parts must nea rly always be purchased by t he manufacturer, so I won't concer n my new. F ew people have t ransistors or transistor self wit h it in this article, except to stat e that transformers in the high po wer ca tegor y in the power su pply puts two kilocycle noise onto their junk box. Using all new parts t his unit the twelve volt line that takes severa l thou will cost around forty dollars, a nd t his might sand microforads of filter capacity to keep discourage those a fter economy. out of t he modulator. T he most important part of this modulator Although t he modulator was designed with is t he ou t put stage, which may be used wi th effi ciency and power out a s the main goals, I any s peech amplifier capable of delivering was pleasantly su r p rised to find that the a watt or so. This way, microphones other audio quality is quite good, and compares with than carbon may be used, or screen-modula ted fixe d stations in "na tu ra lness." I use a carbon transmitters, such as the Heathkit mobile, 0' 0 5506 ,--11' (DELCOl TRIAC"TY·66A CARBON MICROPHONE 2N301" • e lOOO",fll~ v • 'n 150.1'1. " 112 n • ",. 05506 {DELCOl ''0 • • ,. 150/ 15. 500/15. 0' '"---il---t-+---.+--<--+------...... -f--o . 1000/15 12VDC POWER 12 73 MA6AZINE could be converted to plate-modula tion, effec transformers should be located according to tively incr easing the power output four times. good audio practice to minimize magnetic A driving transformer should be used to coupling.In my unit, the mic transformer is match t he driver tube or transistor to sixteen in t he rf unit with t he driver transistor, the ohms center-tapped (due to t he impedance d river and output transformers are at op ma tch squa re law, the center tap fo r sixteen posite ends of the modulator unit and at r-ig ht ohms is four ohms.) angles to eac h ot her, and the power supply Confused by all t he complicated bias net tumid is neal' the output end, as far as pos works I sa w in transistor amplifier circuits, sible from the lower level transformer. The I ex per imentally determined the cha r acteris out put transistors a r e mounted t hro ugh the t ics of the t r a nsistor s I had decided upon, outside of t he box using t he mica insulator s and designed the circuit over two years ago. and ha rdware supplied with t hem. T he dr iver I ha ve since seen simila r circuits in lower t ransistor is mounted on the back sheet of power applica tion with t he name zero-bias the rf section's metal shell with a mica in class-B amplifiers. The out put transistors are sula tor I made from material kept by hard biased slightly below cut-off by returning the ware stores for stove windows. T he transis base circuit to the emitters, making f ull class tors must be insulated elect rica lly, but not B oper a tion. This is supposed to int roduce thermally, from ground, as the transistor shell some distort ion, but it is not noticeable in my is the collector connection, and t he heat-dis unit. The driving impeda nces of the t ransis sipa ting element. tors were al so determined experime nta lly, as I use a n Fl telephone ca rbon button for a Delco would supply no in formation on the microphone, and any other mic. might have use of their tra nsistors in such applications. d ifferent gain or other circuit considerations. The driver circuit was designed as a class T his telephone button has ver y good gain A amplifier using RCA characteristics, a nd a nd fid elit y, but has the disadvantag-e t hat it input and output impedances. Since the input tends to pick up traffic noise. The " communi impedance of the driver and t he out put im cations" ca rbon mics. pick up less noise, and pedance of t he ca rbon mic are about the sa me, require louder ta lking. I first tried ca pacit y coupling between the I got the driver transformer on a special two, but found the sta ge tended to oscillate sale, and it might be difficult to duplicate ex beca use of collector-base coupling through actly. It is much la rger than necessary, how t he t welve volt line, even though that line ever , so a smaller subs titute might be a n was well-filtered.With a mic. t ransformer, improvement. T he r equir ements for the driver • t he phase may be r eversed to cancel this feed tra nsformer a re a couple of wat ts power back. The rnic. transformer by-pass fil ter ca pability, a sixteen ohm secondar y with a ta p ca pa citor must be returned to t he emi tter sup at four ohms, and a primary to match the ply line, and not ground, to prevent oscillation. driver used, in my case thirty-two ohms, with The base resistor was selected to give a pproxi a half-a mpere rating. mately 375 mils idle collector current, a nd The input impedance of the driver transistor t ur ned out to be 2200 ohms in my unit. is about sevent y-fi ve ohms, a nd as the carbon No gain controls have been provided in t his mic. out put impedance is nearly that, a one circuit , as I believe none are necessary in to-one transformer with as near to that im mobile operation, where the sa me operator uses pedance level as possible is used to couple the rig all the t ime.T he over a ll gain may be them. The primary must handle fifty mils mic. initially set up by j ugg- li ng t he value of the curr ent. mic. bleeder r esistor , so long' as the mic. button It should be borne in mind that the output cur rent does not exceed a bout fi fty m ils.I stage of this modula tor dra ws fairly heavy use about fort y mils but ton cur rent , to get current, and the power leads, relay contacts, full modulation with my normal speaking, ground connections, etc. should be of suffic ient a nd t he 150 ohm r esistor was selected for size. t hat purpose. I hope that this modulator will work for Ver y heavy fil tering is required across t he other builder s as well as it does for me. power input to the a udio output sta ge because ... KL7DLC the current drain varies greatly with modula tion, and unless the modulator is connected to a battery with very shor t, heavy leads, a n unfil tered modulator can modulate the twelve volt Very Short Article power line, causing ser ious circuit inter actions. Toroid Tip H eavy filtering a cross t he driver is r eq uir ed to red uce r eceiver a nd transmitter power sup ply noise fed into the a udio from the t welve A wafer octal socket makes a nice tie point volt line. At power transistor impedance levels, st r ip if you are bu ilding a toroid core trans heavy filter-ing means capacit y in the t hou for mer for transistor power supplies. Just sands of microfarads. bend t he solde r lugs down and attach the leads In construction of this modulator unit the from the windings. • •.. VE6WT APRIL 1961 ~ . ~ ...... " • ",0 ... ,,. .. f' you'd like to know more about a complete I 2 meter st at ion for less than $45.00, read on! La t est in the Heat h Companys' line of ...... ,...- low priced transceivers is t he HW-3D , a two meter model, similar to t he ten a nd six meter models. T he size, shape a nd color of a ll t he • u nits a re the sa me, t hough the insides of the • Twoer arc somewha t, different. Transmitter Regular 8 me crystals with st a nda rd .500" pin spacing (FT-243 holders), are used in the - oscilla tor. The pentode half of a 6BA8 tube is used a s the oscilla tor in an electron coupled, Pierce oscillator circuit. The plate circuit of the oscilla tor is tuned to 24 me, thus tripling Donald A. Sm ith-W3UZN in the oscillator. The second half of a 6BAS Asscclete Ed itor (triode) takes the 24 mc output from the os cillator and triples it to 72 me, The 72 me signa l is t hen fed to the triode half of another 6liAS tube which doubles the signal to 144 me and drives the final. The pentode half of a 6BAS is the final, operating straight through on 144 me. Bypassing in the transmitter is extensive, with over two dozen ceramic disk capacitors being used! All tuning in the rig is done with 73 slug tuned coils, with the exception of the fi nal, which is tuned with a 2.5 to 6 IiJdd trimmer capacitor. T he final coil is mounted right on the trimmer proper, to keep the lead length a s short a s possible. P la te modulation is u sed, which gives you more "punch" than other types. • Tests Receiver The receiving section is very sensitive, even though a super-regenerative detector is used. Heath ha s improved on t he standa rd super regen by adding a tuned rf stage. A low noise 6B88 t ube is used in t he receiver. One triode of the tube is used a s the rf amplifier and the other triode a s the super-r egen detector. Some Amateurs have never used the super-regen, HEATHKIT so I will mention t hat one of the problems with them that has always been annoying, is what "Twoer" .....HW·30 is known as " suck-out." That is, a s the receiv ing f requency is changed, the detector will Two Meter Transceiver drop out of oscillation. Size: 7" x 9%" x 6" deep. Weight: 6112 Ibs. Power: I 15 vac @ 45 watts. Transmitter: 8 mc xtals. 5 watts input. Receiver: Super-regenerative. RF amplifier. Tunes 144-148 mc (CAP .I & MARS). Assembly Time: 7 hours, average. Price: $44.95 (including mike). • 34 73 MAGAZINE • .,. ... :":1 w _ ~ - • •• i: ' ra , 1 - ~ ~ TTTY T .. ,/0 " "U I ., I ~ O , I --"- I .•..•. I _-_,_.. _.... _- " -" - ' ~--~ , _ , '~-_H_"' _ _ .. - -~ _ ·_ W_W ...... _'..__ - _ _· _ · ~ W _ ·· W ' · _ _ _-_·__._-·W._._-·__....·-,..__ '.. _·K._.... _._~ _· . _ ..---=.- ~- - •..,~' f'.'" • ' M",_ ,___ . _ W _ <,0. ...) - , _ _ --~- ~...--'_.. .. ,,~.• 0 2 METER .o.lO.o.n UR TRANS CEIVER -~ ~ _. ~ _... _ - -- ._.-- __.. .. 0_- _. _._- -_---. • • ;:,-::1::::::,:"-:::::-.=:':,- :it~" ! - .'.. . _K,,-_.. _K._- -- .. . . _--- ~ .. . . ~ .--,,,_-._...... _.-_._..... ,... Heath has eliminated this problem in two A full-wave voltage doubler circuit is utilized, ways. First, they use impedance coupling be using two silicon diodes. B+ out put is ap tween the rf amplifi er stage and the detector proximately 260 vdc @ 90 rna. The supply is a nd secondly they ma de the f eed point of the wired in such a way t hat an external de sup detector a very low impedance. Thus when the ply can be plugged into the r ear of the unit regeneration control has once been adj usted a nd all necessary changes in the rigs circuitry properly, you can tune between 144 me and a re automatica lly changed over when the 148 me without any further adjustment of t he proper cable is plugged into the rear of the regen cont rol. It should also be mentioned that unit. the super -regen is famous for re-radiating Bu ilding the Unit signa ls from the receiving antenna. The rf st age minimizes this r e-r adia tion. Building t he rig r equires 6 or 8 hours to complete and should NOT be hur ried. The de Audio sign and layout has been ca refully thought out, as long leads, par ts placement a nd gen On receive, t he audio section includes one eral layout become quite critical at t hese fre half of a 12AX7 as a voltage amplifier, f eed qu ency. A ll capacitors used in t he rf circuit s ing a GAQ5 output tube. A 3% inch speaker ( bot h receiving a nd t ransmitting sections), is mounted on the f ront panel of the unit. One are disc ceramics and even tube sockets a re wat t of undiator'ted audio is available in t he of t he cer amic, shielded types, for low loss. r eceive position. Note in the photos, that the bottom of t he unit On tra nsmit, the audio section becomes the looks like there a re hardly any parts used in modulator. One half of a 12AX7 tube is used t he unit. It gives this appearance because t he as a mike pre-amplifier a nd t he second half lead length was kept as sho r t as possible. of t he 12AX7 is used as a voltage amplifier, Actually t here are 42 ca pacitors, 25 resistors, driving the 6AQ5 out put t ube.A tap on the 8 terminal st r ips, 2 contr ols, 1 rotary switch, ou t put transformer is used to provide the 6 rf coils a nd 6 rf chokes under t here! proper impedance for t he fi nal rf amplifier, The filament circuit and t he B+ wiring is pla te modulation being used. An rfc and .001 done first, with the t r a nsmit ter section follow disk cer a mic capacitor are used in t he mike ing. T he receiver section is t hen wired, with input to the modulator, preventing rf energy the power supply and front panel wiring done from re-entering the audio section during last. Parts are furnished for making one ac tra nsmit. and one dc (6 or 12 volts), power cords. Power Supply Tu ne Up A built-in ac power supply is included with The rig, as mentioned before, uses 8 me xtals the t ransceiver, using a power transformer. and when it comes to tuning up t he ril:', you're APRIL 1961 3S ------the other side of 1200 foot mountains and the sig nal repor t was 59! To top it off, I was , using a six meter beam at the time !Lat er , working the sa me sta t ion with a two meter beam, sig nal reports were 59+ + +. There is no drift with the rig, nor any FM and modu lation quality is excellent. T he receiver section is ve ry sensitive a nti sirma ls 'were hea rd often from Wa shington, D.C., Alexandria, Va., etc. Selectivity is nothing to r ave about, as would be expected with this type of receiver. On the VHF bands this is seldom impor t ant. And fo r mobile use the rig really fills t he bill. The VP-1-G (or 12), vibrator power sup ply g lad it does a s there a re no t r ick y cr yst al feed is designed for Hea t hs' line of transceivers back adjustments, or troubles with lack of and one of these su pplies will operate the 6 "drive:' To make the tune-up even easier for or 10 meter models from a six or 12 volt ba t those not too familiar with these frequencies, tery. T he Twoer requires two of t hese su p approximate set t ings of all t he coil slugs and plies, however, a s the B+ current r uns about t he final tuning ca pacitor are given in the DO mils on transmit, while the other models tune-up procedure. runs about 60 mils. The sup plies are quite in (See d iagram.) The oscillator is tuned to expensive, at 7.95 each in kit form, complete 2-:1 me with the slug' in Ll being used to make with tube and vibrator! the adjustment. The triplet' is t hen brought T he six a nd ten meter t ransceivers can be to resonance with the adjustment of L2. The bolted together, along' with t he T woer to pro doubler ca n then be tuned by adjusting L3. vide a complete 10, 6 and 2 meter VHF st a The fi na l is d ipped by adj ust ing the final tun t ion for about $130. A single meter can be ing' capacit or, C16. There is only one dip pos used for all three units when they are con sible in the final ! The two meter model ha s a nected together. lit tle different set -u p on the meter plug than All in a ll, there is a lot of f un to be had the other two models. T he T woer uses a two with the little T woer . At $44.95 it su re is an circuit j ack, t he first position being used to inexpensive way to get on two meters. It is measure t he rf output voltage with a sta nd my personal hope that the rig will encourage ard de VOl\l or VTVl\1. When the unit is tuned ot hers to come up on the higher bands. properly this voltage will be about 14 or 15 .. . W3U ZN volts on a 20,000 ohms/volt meter. A d iode and filtering circui t is built into the rig to provide this reading, which is helpful in tun ing u p the rig'. When the meter j ack is pushed all the way in, (to the second position), the meter is placed in series with the fi nal amplifier, per mitting the final plate current t o be r ead. Please NOTE that the meter can not be left plugged into t he second position of the meter jack, u nless the rig' is actually switched to transmit (o n t he front panel), a s t he meter complet es the final cathode circuit to ground and the final will be operating regardless of t he f ront switch setting. Recei ver t une-up is very easy and a GDO, sig nal generator, or an on-the-air, two met er sig na l can be used. The adj ustments include rf amplifier tuning, detector tuning and re genera t ion control adjustment. The receiver a dj ustments a ffect each other slig ht ly, so the other adj ustments must be checked after mak ing any adjustments to the receiver coil s or the regen con t rol. Check ing Out th e Rig I have to admit, f rankly, that I was really su r prised at what the rig will do. T he first station worked was about 45 miles away, on 36 73 MAGAZINE Chrome-Plated I , 24 HR. WALL , 'I CLOCK SI:'IC·Slar tin&, Projt'dion Map of thl:' World MOBILE MIKE #As Long As They Last Just $395 SPECIAL $10\'a lu.. . 95 fo:IC t"I:'Il !!'nt l ''''..d e e r a m it" $14 Pu..h -to-T a Ik _\I k r u p h u n " SW-59 $ ~.l"" Exclusive!!! Super Sav ings e lf.Supporting SHORT S Round Hole WAVE WRL 5pire Tower Punch Set A ;12 h . Tower RECEIVER V Con erete Moun t Wt. Only 150 I.h!4 . C lean and * Transform !!'r I· " wl' r l:'d E Acr u ratl:' lIo les w ei t e f., 95 * Be nds pread T Un' lIlr $3995 Beechu r e 7A $49 ~ . 11/1 6. %0. Covers 540kl'. • ar me. * $ I. 1-3/ 32" * "S" Meter Prepaid Anywhere T- HandJe and Ca m p a r eo< 10 R evr». at Dou b le P efee $ (Cuntinl'ntal U .S.A . ) T aperl:'d Heamer BARGAIN NO. 9A . BARGAIN NO. lOA Amazing Low Citizens Band Price ~;::::;'l Complete 80-10M ~ New Transmitter RECONDITIONED J 40 w . AM CB-l00'S 1'- -.-... ."- ) .. '" ~ E %::: · . 50 w. CW Io'a ('t..r) R ~ondition",d • - .. - - ~ 9, r-:C/ 100 w .( P . E.P ) n SB (:Iohe's f amous U 8H.IOO ~I~~'~~'IX~~;:'~;~;: $69 $69 3-!1 m e a nd 12-30 m e with Cheek"'. Xlal. f., o~. Now 95 I Only 95 built_in powt'r lI u p p ly . C han nel. !I 0 Va)- W arr a n t y . l.:tn efll most MARS. CAP. de. - --- WOiUDRADl(rLiioTAroRiES-73 '~ 3415 W. BROADWA Y• PH ON E ] 2 8-1B5 1 • COU NCIL BL UFF S, I OW A I PLEASE SEND M E THE FOLLOWI NG BARGAI NS: I o CHECK o DOWN PAYMENT o 3D-DAY CHARGE I I NAME: CALL _ I ...• A DDR_------_ESS: CITY & STATE: .._ • APRIL 1961 37 a Rad io Frequency Noise Suppression 6;11 A,hby K2T KN impedance and is a very effective short cir Box 97 cuit for noi se from the low frequencies to the Pluc kemi n, N. J. very highs. r----' : .- \ I I Y -- c NY electrical circuit that has a load that A is alternately connected and disconnected from the supply voltage can be a source of radio frequency noise. Unless precautions in Radio Frequency By-passing design a nd installation of t his equ ip ment is DC or low frequency ae current t ravels thru taken, severe radio and television interference out the area of a conductor, but high fre may result. Units that use a brush type motor, quency ae current travels closer to the surface. vibrating load contacts, or neon-fluorescent At frequencies above approximately 500 kc lamps arc good examples. This rf interference all energy is traveling on the outer sur face may be radiated from the unit or its supply of the conductor. lines or both. Bypassing of rf energy to ground (st ripping The radiation of this interference from the noise components from a conductor) has been supply line can be reduced by installation of done in the past by use of a by-pass capaci a capacitor across the line as close to the gu'ilty device as possible. tor. ,...--, I I I I:g; I , T=-~I:---=~_ L~..J 1 This capacitor acts as a shor t return path This is only partially effective, and is very for the noise and helps to isolate the line. dependent upon actual circuit conditions, par ticularly t he actual impedance to the rf ener gy at the point of b:~rpass. r--' r-----.., .11 "li1-AI .:g; I J:-~ C \ 1 I T Y 1 L.__:J'f---....:¥iLu_u-.J ".."" Complete sh ielding of the unit plus two capacitors will reduce radiation from both the line and the offending load unit. Notice Given a by-pass capacitor that has a 10 that the use of tv...o capacitors allows both ohm impedance (this is the sum of the ca sides of supply line to be effectively shor ted pacity and its leads) and a load impedance to out to the shield as far as the noi se is con rf at this point of 100 ohms, then approx. cerned. At very high frequencies radiation 90 % of the rf will be bypassed. If the load may occur from even a very short length of impedance to rf is 1 ohm, just as likely, then ,vire. Capacitors that appear as low imped the bypass is only 10% effective. ance shunts at low f r equencies may not be on A co-axial capacitor is so designell t hat it VHF due to internal impedance. A special completely surrounds t he conductor carrying type of capacitor called the co-axial capacitor current. Thus, all rf currents traveling on the has been developed that has very low internal sur face of t he conductor flow to ground. 38 73 MAGAZIN~ • I 'P~STROM ) I I ' ,, ~ \ // \, , ;/ ,,-, - HERE'S A NEW HEATHKIT" GROUNDED GRID KW LINEAR ... JUST $22995 The new Heathkit "Warrior" is a completely self-contained, desk-top kilowatt linear, loaded with special features, at half the c ost of comparable units! Compare featu re for feature, quality component for Quality component, you'll find no shortcuts . . , only the finest watt-per-dollar value in a linear amplifier on the amateur market today! - M..lm u m power Input: 558- 1000 w a tt ~ P.E.p., CHECK THESE FEATURES ,• • CW- ICKX> wetts. AM -400 walts (500 walts usinQ ca rrier Compldel!! eetf-contaiued • • . HV, Fil. and Bias supplies built in. controlled modulation). RTTY--650 wall s . Driving pow.r requlr.d: SO to 7S wa!ls-deO('nding Otl Ir... Versatile . .. .Ma y be driven by any 50 to 125 watt transmitter Quenc .... Dut put c irc uit: Variable Ol·n('twor~ {SO to 15 or exciter-s-no matching or swam p ing network required. ohmsJ. l nput circuit: Broad banded-rPQu;res no Iue Effid nd . .. Stahle grounded grid circuitry a llows most driving ino . In out Imped.. nce: Aooro>. 10 ohms. Ba nd eee erao.: 80. 40. ::>0. 15. 10 meters. P ilne l metering: power to appear in output for up to 70% efficiency. Switch-selected. grid cu rrent. olale cu rrent, h''Ih vert Oil-filled capacitor • •• And 5-50 hen ry swi ngtng-c hoke provide age and rel ative power oUloul for caso of 10adinQ. the excellent dynamic regulation req uired for high peak power T ube com ple m ent: 4·811A . 2·8f,6A. S ire: 19X" W output with low distortion. J( 11 Y-" H " 16" 0 .,._ .. I l1~ :r Jl f' ''1( i r f' tllbf'1( • • . --I paralleled 8 11A's nnd 2-866A's. forced air cooled hy s jle n t built-in fan. Stable . .carefull design provides a h igh degree or over-all era hility in conjunction with the grounded grid circuit conflgur ation. E rrlueire .. . Interna l RF shielding of plate circuit for maxi m um T VI suppression. l nterlockcd flll'itrhilig . . . prevents accidental a pplication of HV before swi tc hi ng o n filament and bias. RII(Jgf·(J ranetrurtion . .. 16 gaut::p stf>Pl r-hasa..is - ! -;'''' a luminum This inside view shows the neat circui t layout front panel-s-welded one-piece cabi net. and husky components that emphasize quality. Kit Model HA-,O • • . 100 lbs, $23 d n., $20 mo•.....$229.95 Note the internal shielding of plate circuit for Assembled Model HAW·10 . maximum protection against TV!. 1------100 Ibs . $33 dn., $28 mo $329.95---- FREE CATALOG IHEATH COMPANY I Benton Harbor 11 , M ichigan nd t oday fo r I D Please send my Free copy of the complete Heathkit Catalog. Jr Free Catalog scribing over I different : NAME athkit products Hi·Fi, Test , I ADDRESS r ateur Radio, rine and General I -tsumer fields. I CITY ZONE STATE u nit to facilitate mounting. Occasionally a heavy ground wire from a well in stalled external ground, bonded to the s hield a round t he interference ge nerator wi ll hel p, but many m isconceptions exist about g rounding equipment and its effect on noise su ppression. T he rf im pedance of t he load has very little When t he su pply line is radiating the noise, effect , the amount of rf removed depending a ground connection to the unit may increase only on the quality of the co-axial construc the radiation. t ion and the capacitor in stallation. I n unusually severe cases of rf "in ter f erence or where s uppression must he complete, a 7/ Pi t ype noise fi lter can be used . This consists EOUf'UENT of t wo s pecia l capacitors and an rf choke coil, 50 a rranged t hat noise is effect ively shu nted inside the shield, isolat ed from the line, and the sup ply line is bypassed. These filters are su p plied a s sing le unit s a s shown or as a dual Any lead carrying noise currents will radi ate, unless completely shield ed, and this in cludes long ground leads. The offending device - must first be isolat ed at radio frequencies from -- its su pply line; t hen f ully enclosed in its shield ; t hen a good ground may help reduce the remaining direct radiation f rom t he unit and very low frequency noise. . . . K2T K N 432 me Transi stor Con verter, Pa rt II . .. W3HIX (printed 05S 05 public service for t hose few hams t het have to have 05 d iag ramI TlnV1Jo1l741 TlnUI:HIT4t T-l8n/2NITU "-"U ~ ... -t ~ .. L' I_U Tl11l9l2Nl144 .Tlll9ltNI1'44 ''f- "I-:: ~ ,,,1" ." .'" n . 40 7J MAGAZINE U ;//l/ TMC COMPLETE COMMUNICATIONS SYSTEMS a/tal EQUIPMENT• CAREFUllY PLANNED. THOROUGHLY TESTED. COMPLETELY INTEGRATED to meet your most exacting performance standards . . . to meet y our every requirement for HF Telecommunication systems. TRANSMITTING SYSTEMS. RECEIVING SYSTEMS. TRANSMIT/RECEIVE STATIO NS Po int-fa-point .. . Ship -fa-sho re . .. Shore-fa .ship . .. Mobile . . . Fixed . . . Transportable . . .HFly.oway." Eng i neered by men w ith many years dudes all p ho se s of layout, inslo llo o f p ro ctica l e aperfe nce and (I voat t io n, operation and maintenance fa knowledge of those co mmunico ti on ouure o p timum pe rfo rma nce unde r proble ms p e culiar to every p o ri o f a ll cond itions. Full detcits o re ovett the world, TMC systems plan ning in- a ble upon request. THE TECHNICAL MATERIEL CORPORATION IN CANADA: TMC (C AN ADA) LTD. MAMARONECK, N EW YORK APRil 196 1 41 Ta ke Your Pick or Gelling )'ollr fill of F ilters Staff NE of the most fascinating things about cxis ti ng receiver. And, let's face it, most of O this business of ham radio (it sa ys here the brand-new receivers in the under-$500 in fine print) is that you can take your pick class could st a nd some improvement in the of conversations-with Europe, Asia, Africa, selectivity line. Australia, the Far North, Antarctica, or near Literally hundreds of articles have been ly any state of the 50. All you have to do is written in t he past 10 year s on impr ovement turn the dial of your receiver.. . . of selectivity. It's not possible to cover the con And if you've been in this game for more tent of all of them here. All the major points, th a n 15 minutes, you've undoubtedly wi shed to though, are included-as well as some which hig-h heaven )"OU n-e re able to take your pick seem to have been unduly neglected. of the umpty-odd sta t ions roaring through For a sta rt, let's look at the various ways of your receiver's selectivit y curve and clobbering achieving ideal select ivit y. None will be success shma ls you're trying to copy! f ul in obtain ing t he theoretically-perfect 2 In this country a lone, t here are nearly 300, t o-l "shape factor " shown in Fig. I, but some 000 hams and at any given time it's safe to of them come pretty close. a ssume 10 percent of them are on the air. The The first thing that comes to most hams' "popular ba nd s"-75, 40, 20, 15, and lO- -have minds when you mention selectivity is a filter. a total of 1,650 kc of space allotted for A3 But there are filters and more filters.. .. emission. That theoretically gives each ham There are cr yst a l filters and L-C filters, something like 5.5 cycles all to himself. ceramic filters and mechanical filters, costly Of course, there are severa l simple answers fi lters and costlier filters, and so forth into the to t he problem. They all add up to t he same night. And any of t hem, properly used, will do thing: increase your receiver's select ivity. the trick. However, the de tails of each answer differ. Besides filters, though, the list includes Q By far the simplest answer is t o rush out multipliers (either out boa rd or built-in), and buy a new r eceiver. 1\0 fuss, no muss, no "Q-Fivers" and other multiple-conversion de bother. But be sure to get one which has no vices, and the IIsig nal slicer " line of gadgets. ticeably better select ivity t ha n the old rig Properly used, any of these devices can cure a nd be prepared to shell out more t han half t he trouble of too many signals. Frequently, a kilobuck for it! severa l of them may be used together to take Most of us, for financial reasons alone, are care of the most st ubbor n problems. But if forced to do somet hing about improving the they're not used right, any of the gadgets can introduce more troubles than they cure. , 0 , Oldest aid to selectivity in t he list is the •o , single crystal filter, making use fo both series ------.. --- ,,,-'4 -- and parallel resonances in a single quartz ' 0 - - " -- crystal at the receiver's if frequency to '" achieve a passband peak and a rejection notch some 40 db deep. Its principles are gone into ' 0 TYPICAL 'GOO!>' PERf"E~ ." quite thoroughly in all the ham handbooks , ATTAJN...., ""'"o and won't be repeated here. Just one thing 30 "'"'' .. ~ 42 73 MAGAZINE graph. You can add a crystal filter to almost a ny receiver, easily and successfully. H ow. ever, it won't be the simple, basic circuit. T he crystal filter most favored for homebrew in sta lla tion is the lattice circuit of F ig. 2. :\Iany --- • •• Fig. 2. Fu ll la ttic e crystal filt er. X I a nd X2 shou ld breeket the receiver ;f frequency and crystals of the same frequency must be within 50 c ycle s of each othe r. variations of this circuit can be found in the literatur e, but t here's lit tle basic diffe rence in the performance of a ny. Bandpass is deter mined by the frequency sprea d between Xl The 80 th ru 10 meter band-sw itching pi network is and X2, and will be roughly equal to twice designed fo r 800 watts PEP SSB, 400 wotts CW, FM the difference in frequency of the cryata ls. All or FSK and 200 watts Linear AM with 50 - 70 ohm crysta ls of the sa me frequency should be with output. Popula r 100 wott SSB ex citers req uire no in a few cycles of each other.Don't trust t he swamping or mafchil)g ne tworks to dri ve the low Z markings-rig- up a simple oscillator and listen untuned input. Grounded grid ci rcuit uses four 1625's to the 3rd or 4th harmonics with a BC receiver. or 837'5 o n customers request. Meter rea ds RF drive, You may have to check a half-dozen simila r- ly pla te current, RF amps oUfput. New modern compa ct 9" X 15" X 10 ~, " g ray cobinet also conta ins power marked crystals to find two close enough to sup p ly using 8 16's . TVI suppressed, Porasitic Free. gether for use in this circuit. Advantages of t his circuit include ease of SEE THE NEW LA-400C AT YO UR DE ALE RS construction, inexpensiveness if surplus FT LA·400·CKit Complete w ith tubes . .•. •• • • • • . $164.95 241 crystals are used, a nd general reliability. LA·400·CWired and tested .. • • •• • • •.. •... •. $21 9.95 Disadvantages are t he fixed passband and the trickiness of receiver alignment after such a filter has been added. Points to watch in con 1?& ELECTRONICS INC. st r uction are these: Keep the input and out ~ 424 Columbia, lafayette, 'nd. put of t he fi lter well-separated to a void a capacity pa th a round t he crystals, and be sure to put the filter as soon after t he mixer stage TWO METER as possible. Out-of-passband rejection averages OMNIDIRECTIONAL 30 db with good construction technique. This TURNSTILE ANTENNA $3.95 P.P. in is enough to help, but not enough to keep that U.S.A. • Fixed o r ~ Iobile • Can be sracked • Light Weight . Excellent fo r CO & N ets « California kilowatt down the st reet from get Elements, Hub. liard ware. Phasing Section, and ln ting t hrough. struction Sheer Included. Another crystal-filter cir cuit operating on MERCURY ENTERPRISES G': ~ ~ /~~", . • entirely different principles is shown in Fig. 3. This one is a complete substit ute for the if st rip of your receiver, and a ct ually can be used to make a good separate receiver if you JIM CLARK Wl ULU pu t an rf stage a nd mixer a hea d of it and KIT WIRING & TESTING LABS so _ 144 - 220 • 420 me follow it wit h a simple detector a nd some Nuvi stor Preampliflers ...... •.•.•.•..•...... S19.9S audio. With b uilt-in powe r supply ... ••....• ...... •$32.95 This circuit makes use only of the parallel Complete wi th 6CW4-Slug funed 2 Aiken Street Tel.: HEmlock 2-3600 Derry, N. H. (Continued on page 44) APRIL 196 1 43 ~ t .... ~· t icc ~·t ee ~~ t -~ t » 00 ·t ." "" = "" = '" = ='" = "" .co .000 ;;f'; .c. , .00' .* ..* ,,* \ --- "* ------" 6BK7 tz: -.:: , ••1<7 ..:;;V-- --- 'q.I" ',0- ,,,,. HII- .(:0"'" :-ilf- Hlf- , ~ - ~ eeoc ,,.. ., ;; ... i """ - 1';•. - "'" J, Fig. 3. C rystal coupled if amplifier. For CW use all crystals should be wi thin 50 cycles of the serne frequency. For AM reception they can be staggered -+- 1.5 kc. resonance of the crystals. Since the crystals trade-the Hea thkit Mohican. provide the only effective cou pling between if The ceramic filter operates on t he sa me stages, sig nals must be a t or near the crystal's basic principle as the crystal-t ha t of piezo resonant frequency to be a mplified. Using 3.5 electr icity. However, since the ceramic filter me cryst als with a frequency sprea d between is manufactured by a process much like that cr yst a ls of 1 ke 01' less, t he passband will be used in making a spirin tablets, almost an y just about wide enough for an AM phone sig desired characteristic can be built in to help nal. If you drop the if to about 1600 kc and cure selectivity problems fast ... FAST . .. keep the crystals within 50 cycles of each FAST!! other, you'll get an go-cycle passband which One of the fi rst major differences was de is ideal for C'V if your local oscillator is velopment of a "first overtone resonator" stable. W it h a HlOO-ke if but st agg ered crys which shows only a series reson ance, with all t a l frequencies ( ± 1 kc) the passband will parallel resonance effects missing (fundamen again be right for phon e use. tal resonators s how select ivity curves almost This is probably t he simplest of all really identical with those of quartz crystals) . The effect ive filter circuits, si nce out-or-passba nd "first overtone" ceramic resonator is the elec response is nearly 90 db down. Its major dis trical equiva lent of a very-high-Q pi -network advantage is that it requires construction of circuit , and a s such shows much sha rper cut a sepa ra te if str ip. Even so, its cos t is st ill off above its resonant frequency than below. lower t han a mechanica l fi lter-which is the However, by combining resonator elements the onl y other type g iving equa l r esults. manufacturer has d eveloped a six-section filter Closely allied to the cr ystal filter in many with a sha pe factor of 2.25 to 1. ways, but possessing a few impor t a nt differ In application, the ceramic filter is more ences all its own, is the ceramic filter . Devel closely linked to the mechanical breed t han oped by Clevite, t his device has been used in to the crystal. It is su pplied as a sealed com only one commercia l receiver f or the ham pon ent, with input, out put , and common t er- ,"50. ~I ~ ., ~+ I, ,.~ ~~ -+ .,~ I 'EI \ WOUT• 6CBI ; ,I SCBS --- f'; " ------, --- COLLIt CERAMIC F"IlTER REX RAD IO SUPPLY "N.YC.7ORTlA,N.YND T. STREET BLITZ-BUG Fig . 4. Manufacturers re commended circuit fo r COAXIAL CABLE instal lation of a ceramic filter. Tra nsisto rs a re Lightning Arrester RCA type 2N1 39. Model # LAC-l Pat.No. 2.922,913 minals. Unlike ot her filters, it is most tolera nt .2' HAYWARD ST. of variations in source a nd loa d impedance, CUSHCRAn MANCHESTER. H. H. per form ing equally well in a 2700-ohm circuit and a 10,OOO-ohm circuit with no cha nge in BOSTONIANS! cha racter ist ics. Available pa ssband widths Arise ! You're surrounded by Bob Groham W 1KTJ. range from 4 to 20 kc at - 6 db. Skeptical? Well, look fo r yourself. Visit either of the Since impedance levels can be low, t he Groham stcres a nd see nolhing else but new and reconditioned hom geor ot New Eng la nd's ."01,, cera mic fi lter is ideal for tra nsistorized CIr exclusive ham stores. It's w orlh the trip. cuit r y. The manufacturer's r ecommended cir ~orlh o f Ba sion a t So u t h of n a Sion a l cuit for narrow-band applications is shown in 5 0 5 !Ha l n, R ~a d i ng ] ] 0 5 N. I'l a in. n a n d o)I,b Fig. 4. The only fly in the ointment is this: Pbon~ I 944-1000 I'hone I \\"0 3 _5005 they're not readily available through ham sup ply ch annels. F or the nearest di stributor's name, you have to contact t he manufacturer : Clevit e E lectronic Components, 3405 Perkins A venue, Cleveland 14, Ohio. Hambench Hit One of t he most popular filters which ca n be easily added t o any receiver is the Collins mechanical fi lter, which features a 2.5-to-l of IRE Show! sha pe factor . Based on magnetoatriction prin ~ l ASS . ciples, it provides excellent cha r acter istics with BHOCTON, Aldell Products a minimum of adjustment. Its maj or disad Company reports that their ex h ib it at va nt age is cost : somewhere near $50, depend the New York I.R.E. Show has been ing on just which of the severa l ava.luble models you get. Equivalent performance is overr un with ha ms sc rutin izing a nd ex available with other circuits for less monel . claim ing over their Hamhencli. Mr. but they take more time and trouble. .:\I alcolm P artridge K l.i\'FU. speaking If t he cost doesn't bother ) ' OU, the mechani ca l filter can be added t o your receiver by use for the co mpany. pointed out that the of the adapter shown in Fig. 5. Nothing about company was not short o n advertising it is cr itical except t hat isolation must be literature ill cusc any one wus interested maintained between input and output of the filter to prevent leakage around it. Separate in further investigation.He pointed out t ubes instead of a twin-tr-iode are necessary that page 4.':; of the January issue of • for the same reason. H7.~" would give prices and data to hold Last on t he list of filters is the L·C type. W hile it's possible to design a nd build a the curious unti l he can sent] them clussic-Iine L-C filter to work at if frequen literu ture. cies, the simplest and cheapest way out is to use casca ded transformers a s shown in Fig. 6. W it h the average receiver, addition of four ALDEN PRODUCTS COMPANY high-quality if t ransformers a s shown will in- 2186 North Main Street, Brockton, Mass. (Continued on p a g e -46) APRIL 1961 45 meter which can be installed concentric-fash ion with the rf gain control if you desire. Cl is a gimmick capacitor consisting of several ~DIDIDE turns of insula ted hookup wire wrapped around the grid lead, with one end connected TO IF TI re 1 5 T4 T'O GRIO Bl.ACK RETURN to t he tube's plate terminal. Resi stor HI con t rols regeneration of t he stage by controlling its gain. Rl will also a ct as an addi tional gain Fig. 6. l ·C if filter. Use high quality if trans formers for TI through 14. control. This circuit works by t ur ning an if stage int o a r egenera t ive amplifier, which adds crease skir t selectivity noticeably.P erfor mance " nega t ive resistance" to its a ssociated trans won't be up to that of a crysta l, ce ramic, or formers a nd greatly in creases t heir Q and se mechanical filter, but will be well worth the lectivity. It has been successfully applied to the time and trouble in volved. S-38 a nd to the Command Sets. F or best use of L-C filters, conversion to a One popular means of improving select ivit y lower if than the customary 455 kc is neces is through use of a "Q-Fiver." 'Vhile the BC- sary-c-but that takes us into the "Q-Fiver" area.E ven a t the lower i], it's usually cheaper . , ~ and simpler to buy the filter as a ready-made .. component from U Te or Burnell t han to brew '00 it your self. T~ If your select ivit y problem isn't so drast ic 7 as t o r equire addit ion of a super -sha r p filter - a nd eve n if you have added one-the Q-rnul. 1., 12AX7 t iplier may be your a nswer.P opula r ized by .cce Heat hkit since its invention by O. G. Villard, rl llevll t his gadget makes use of controlled regenera ,," )'[11 ~" T OO' I .' • tion to mufitply the Q of a tuned circuit to ,. 7 a stronomical values, thereby multiplying its •• select ivity as well. The resulting peak can be used either to boost or t o null a sig na l, de pending on whether you have one or many sources of interference in the passband. A basic boosting Q-multiplier circuit is Fiq. 7. Basic Q·Multiplier circuit. shown in F ig. 7, and t he full r ig incl udin g 453 is t he original of t hi s idea, it leaves much both peak and null functions comprises F ig. to be desired ( besides having become nearly 8.Since t he cont rols of the Q-multiplier have unavailable at a rea sonable price ). Since the no interaction with receiver controls, you ca n basic idea is to convert t he 455-kc if down to add as many a s you like-c-one in t he plate of 50 kc or so to take advantage of improved the m ixer, another in the first if , etc. The selecti vit y a t the lower if, it makes more sense peak or null will have a width approximately to build a s pecial gadget to do just that. then equal to 0.1 percent of your if frequency, and return the audio to the st a t ion receiver f or can be tuned across the receiver's passband. further amplification. The simplest of all Q-multipliers (although .Ma ny such circuits have been published. the term hadn't been heard of when the trick Some feature crystal control of the second was invented) is that shown in F ig. 9. It re converter, some make use of mechanical, crys quires no outboard circuitry, a nd t he on ly tal, or L·C filt ers in a ddition to t he low-if addition to the receiver panel is a pcterrtic- (Continued on page 48) NlJ~~ '00 •• --- i 12 AX7 1l2AJ(7 --- • ,. ... ,. •• Fiq. 8. Complete O-MuItiplier circuit. 46 73 A\;lATEUR RADIO A COMPLETE 6 OR 2 METER RECEIVER for only $ 95 including built-in I 10 volt AC power supply and loudspeaker • Only 3 inches high , completely en closed in cabinet • excellent se nsitivity with stable, superreqeneretive detector • RF steqe for lnc reesed se nsitivity and antenna isolefion • rece iver muting switch for standby-receive • ful ly t ra nsformer ope ra ted • features de pendability end st" bl e operation • ~ it includes pre-tuned coils for ea se of construction • quality compo ne nts used throughout assure dependability Mode l SOSA (s ix meters) or Mode l SObA (two me ters) kit, complete with step- by-step construction manual . $29.95 Model SOSA o r Model SObA, wired, faclory tested . 49.95 Nei l Model ALPHA six meter transmitter kit , features finest qua li ty modu lat ion, crysta l switching, front panel controls, tuni ng meters, cabinet 3 inches high, 20 watts input, low frequency oscillator not overtone type . 58.50 See your d ealer or ord er from : THE NEIL CO. 1336 Calkins Road, Pittsford, N. V. • Baker 5·6170 • HAIL" COLU~IBIA! • Largest Sture-"rarehotlse in the cou n try Huge s tock o f e leetronlc c-ompollenl8 RT-18 /ARC-l 100 -1.56 mc AM xmtr-rec lOW FB for 2M Ex c . $39.95 OY-9/ARC-l Dynamotor for ARC-I, e xcellent condition ...... • 9.95 TUBES ••• ALL NEW Mounting rock for ARC-l ...... • •...... •...... _• ... . 4.95 ARC-2 Collins Xmtr·Rec 2-9 mc, 10 cha nne l VFO or manual ALL SPECIALS! tuning. Pr 1625 PA, pr 1625 mods, inel 24v dyn. exc...... 49.95 4-65A $7.50 R·28/ ARC-, Rec 100-156 mc 4 channels xtol cant. exc. cond ... . 19.95 4-125A 19.95 T-23/ ARC-5 Xmtr 100-156 mc 4 ch. xtol con t...... 12.9.5 4X150A 7.95 R-23/ARC·.5 eee 190-555 ke. Excellent. " Q-.5'er" •. .. • •. •...... 9.9.5 4CX2508 22.50 R-2.5/ARC-5 Rec 1.5-3 mc. Excellent condition ...... 14.95 4X250B _,...... 20.00 R-26/ARC-5 Ree: 3-6 me, Excellent condition _...... 7.9.5 4-A.OOA 25.00 R-27/ARC_5 Rec 6-9 me. Excellent condition ...... 7.95 4-10ooA _... 65.00 T·18/ARC·5 Xmtr 2.1 ·3 me. 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Try r~.i..in. ....r irr~ .i.'ibl, h ..r ~..in.! • Jre b ..y ...~d ..q ..ipm~n' . TS, (; R'.', P RC, ' ·HC• .,u. I,e' .. . It....r from y o... COI~U~IBIA ELECTIIONICS 4365 W. Pico Blvd. (nea r Crenshaw ), Los Angeles, Colif. • WE 8-3131 APRIL 1961 47 ..-1 tlBES ..-1"6CB6 --- ,--.;;'"";--- '~34 220..: ,. ."" "'" -, 1 .,0 ~ OO ' 820 ~ IAVOIO "NO t.vt 6C4 Fig. 10. 0 -5er. Inp ut line con nects t o last if Ave is desired. C ryst al fr eq uen cy will deter. grid. Audi o goes t o th e top of the volume con m ine which sideband is received. Ba ndwith is trol or to t he existing detecto r loa d resistor if 1800 cps. selectivity. One of the sim plest and most basic which allows you to tune the passband across "Q-Fiver" circuit s is that s hown in Fig', 10. your receiver's if bandpass curve is shown in It can be built into a sma ll Minibox and con Fig. 11. With this gadget, you'll have a tun nected to t he r eceiver through a pair of shor t ing" capability offer ed hy only one commer ci al length s of coax. Though a power su p ply is receiver- the 75A4-and there it's done me s hown, r equired power can usually be stolen cha nica ll y instead of electronically. If you f r om the recei ver. add t he tunable Q-F iver, it's best to use the A more-advanced version of the Q-Fiver receiver's BFO ( readjusted some 50 kc h igh- • EiSEl 6B.l6 SBee --- :: ! OKC --- '::: ~ ..----- ~ "''' ..----- \::-- jll~ - ~- ,. ~~ ,. ; 1=;'" .00' .OO! .00 -"" '" ; i'::., eec '" Too - 0' 0 • N 1., sua -- '" .L,aue p, • I ,001 --- ~- --- 1\ NOTe , \.: LI-CI M50NANT Af 'lOOKC - RANGE · ~OO-.~/(C 00' f UN/NQ 11~~ '" '" '" ." Fig_ I I. Tunable ba nd~au Q- 5er. Pentode por velees which resonat e at the if freq uency 50 kc. tion of the bU S may be replaced by the re All connections are shown wi th reference to the ceiver bfo to provide front-p anel adjustment of receiver's last if tube socket. Remove if tube t he bandpass position. LI and C I m 48 13 MAGAZINE HIGH IMAGE REJECTION HIGH SENSITIVITY LOW NOISE --- C EN TI +---'-{------/-.., 432 me NOISE FIGURE 6 DB CRYSTAL CONTROLLED .001 Fiol Bondpan ( '0N" I~ ll'l'IUI Silver plc ted v '0' ca vities "' ,'". ,. No birdies $69.50 " I!eoutiful L..,. ", •• Also for the some p rke 220 mc Fig_ 9. Simplest O-Multiplie r. AVe line is d is NF: 4/6 DB connected a t point X. See ted for details of or 144 mc CI. Tube is existing if a mplifier. NF : 4DB Outputs 14/18: 24/30. 30/3' mc er-] for the tunable oscillator and substit ute a on ony model. crystal-controlled B FO in the receiver. This 3 Ibs. will give you complete front-panel control FOB focfory. Col if. odd 4% so res tc x. without ha ving to drill a ny holes in t he Other Centime g Products, receiver cabinet, and allow semi-r emote place PS-C pwr. sup ply for converters S24.95 432 mc Tric pler.Amp. Ex citer, you r 2M rig. ment of the accessory. w ith 2C39 _...... _ S84.50 The tunable Q-Fiver works by a t riple-con le ss tube S69.50 432 mc llto l cont. ll mlr. l OW out (2C39) .... SI84.50 version process; signals in the if range of An owful 101 of eng ineering ond core hos gone into the receiver are mixed with t he tunable os our products so ot leost se nd for our dete sheets. cillator a nd converted to the seco nd if. T her e, selective L-C circuits trim t he passband down CENTIMEG ELECTRONICS to 3 kc. The trimmed if is mixed again with 312 E. Impe rial Hig hwa y EI Seg undo. Colifornia the tunable oscillator output and r eturned to the receiver if. From there, the sta tion re ceiver takes over for detection, A V e, and • a udio amplific ation. By varying t he frequency of t he t unable osc illator, the passband's posi MOBILE tion in rela tion to the origina l receiver band pass curve can be shifted some 5 kc up or POWER down from center , allowing ~..ou to push an interfering sta tion "over the side." SUPPLY Last stop on t his selectivity tour is Slicer ville. In the six years or so since the term was MODel coined, the na me "signal slicer" has been ap A12 /600/200 plied to near-ly every type of receiver accessory imaginable. Several Q-Fiver devices have been NOW dubbed "slicers," as have some filter circuits. But st r ictly speaking, a signal slicer is a phas $59.50 ing-t ype detector (and as such, almost outside t he r ea lm of t his roundup). Th is 12V input d c te dc t ra n s i s t or i z ~d converter is T he slicer operates by dual detection, with conservo tive ly rate d for continuous o utput of 12 0 phase shift deliberately introduced into the wotts at 6 00V or 3 0 0 V, or any combination o f 600 bfo channels. Resulting audio is shifted in a nd 30 0 volt loads toto ling 120 wctts, phase again, and finally the two audio chan nels are r ecombined. P hase relationships are High e fficiency, small si z~, ond light weight, plus such that signals on one side of the bfo fre freedom from mainte na nce,COnserve your ba tte ry quency add together, while signals from t he a nd increase the enjoyment o f mobile o pera tion. other side of the f requency cancel out and can't be hea rd. Or in other words, the aignal is sliced in ELECTR ONICS DIVISION half at the bfo frequency.T ha t's where the GLOBE INDUSTRIES,I NC. device got its name. The increase in selectivity is obvious-less than half the original pass 525 MAIN STREET band gets through the slicer to be amplifie d. BELLEVILLE, NEW JERSEY IContinued on page 50) • APRI L 1961 49 Complete const r uct ion information on the J . Kyle, Improve Your AC-()C S hort " ' . ",, Reeer vee. alice r is too long t o incorporate here. It was Popular Electrorrics, December, 19M+ . L. M. Temple, I• .\Iultiplif'f. S.S.8 .. q · Sf'f a nd SOJ. published in GE Ha m News Vol. 6. No. 4 QS r. Sept.ernhe-r, 1956. (.July, 1951 ) and will be rep rint ed in a GE O. ( i . Villard. .' Inibl.. St'h·(" th ity for Co m m u n tca Sideband book set fo r publication in ear-ly lionM Reeelverll, gtectrcnlcs, Aprfl, 1!152 . O r r , Oil. cit. 19G 1. A schemat ic diag-ram but no a lig-n ment Multiplf' C o n " f'r ~ i o n Adapti'f~ infc rmation is on page 15 of "Single Sideband E . P . Alvernae, A So"..1 Side-Ra nd Beleeter Sy~ t(' m , Techniques" by Jack X. Brown, W3SHY. QST, May. 19511 . As mentioned ea rlier , this shor t listing Orr, The Radio Handboo k. 14th Jo:';lition (om itted from 15th;. doesn't include every select ivit y-improving Sign al S ueers t r ick in the book, If it attempted to do so, J . N . Brown, Single Sidt'b-and Te("hniquu . there wouldn't be room for anything else in (IE H am News , Volume- 6, No. " I,July, IllS I, out this issue ,, . or in the next , either! How of l.dnt), eve I ' , \ vith the gimmicks collected here, you can easily decide which route or routes you want to follow with your own receiver, in order to be able to pull the sig na l you want to hear ou t of the normal QRM. Take your pick! C rYli la l . 'i1tH II H , L. (lntHded, An l nexpenaive C rystal·Fllt e- r 1.1-'. A mpli fi l'f. QST. Febr-ua r -y , Hl51t F. L:'\nJ,!' fo n t.smith. Radiotron U"sign"r' s lI andhook, 4th Editiun. W. O r r . The Radio Hand book. 15t h Edition. Am('rican Radio R ela y Leag -u e, Singlt'-Sid"band Hand book. A me rtcnn Radio Rela y IA':lKUe, Th" Radio Amatt'u r'll Handbouk, Ce-fnmk Filtl'f" A . Lungo lind K. W . Henderson, Application or Pteaoelect rie R es cnaturs to :\Iodf'rn Hllnd·PallS A mplifit'rlI. paper Ilff.'t'entt:'d at 1959 I. R. E. con vention, N ew Yo r k City. .\1..C' bRn ica l .'iltnll O r r , cp, cit. ' L-C Filtf'rs Feder-a ] Telephone and Radio Co" Reference Data fOf Radio EnKi n~ l'tll, 4tb Edition. Q-l\Iullipli f' f ~ , , K L, Cnmpbefl, Transi storizf'd Q·l\lultlplif'r. QST, Janua ry. 1\t5S. R, L. 1\' 12'1;, Va riablf' n and W id th Q :'tlultiplier. QST, April, 1957. • with Send for (or, at your distributor), PL 77 Techn l cal Specifications and Performance Bulletin de.. scribing 106 Antennas from 3A throu gh 80 meters incl uding " BALUN"- FED ROTATABLE OIPOLES, MONO. DUO, TRI, 4-BAND AND " SPIRALRAY" ANTENNAS, ROTATOR /INDICATOR SYSTEMS, TOWERS, BROAD-BAND" BALUNS," ACCES· SORIES AND " NICE·TO·HAVE·AROUND·YOUR· 'r . ~_ \ SHACK" INFO. For TOP·MAN·ON· Communication and TV Antennas THE·FREQUENCY results ... SINCE Install a Telrex antenna , . . dollar for 1921 LABORATORIES dollar berter in every way! Antenna rex systems from $6.95 to $12,000.00 ASBURY PARK .0. NEW JERSEY, U.S.A• • 50 73 MAGAZINE BIG MAP DEAL GO FIRST CLASS These DOD (3- D) maps are widely adver tised at $9.95. Unfortunatel y we have been ON TWO unable to make a special purchase of these fine maps and therefore we must bring t hem The LW-S1 to you at full list price: a low, low, only $9.95! Deluxe Perhaps a glowing description of t he maps will arouse your interest. Well , let's see . . . hmmm. Well, first of all they are pretty big . $59.95 28 ~" and 18 !1z" to be exa ct. And they are printed wi th eig ht colors (all differen t ). But Feature s: best of all are those mountains that you can • 45 wa tts input , fully neut ralized feel. They stick right up at you nearly an • Uses inex pen .... h e 8 me xtals or \'FO inc h. They are in the right pla ces too. Amazing • Plat e mod ulated for effi ciency and punch job. They come complete wi th the frame and • Input for crystal or carbon microphone a handy map index whi ch locates all the •In kit form 10 cui ('osls places for you. You can see the maj or highways • All hard parts mounted (over 1(0) on the U.S. Map. • 6 or 12 \'011 filament • Speech clipping & limirlng fo r max modulation Order Direct: LW· 51 Del uxe kit, leu tubes & II tol $59.95 LW-51 Delulle kit_ w ith tllbes & any II tol. 74 .95 LW-51 Delulle kit, w ired & tested ...... 89.95 5hip weight 7 Ibs.: 77c Eosl COl;l sl; $1.59 Western LW -72 AC Power Supply for LW51, wired 49.95 LW·61 VHf Conve rters ...... 18.50 LW -80 Pre-Amplifie rs ...... •. . 12.50 LWELECTRONIC LABORATORY ROUTE 2 JACKSON, MICHIGAN r------I------~ I NEW I I I I I I I I I II C, I I I I I I I I I I I T-R SWITCH ~~~..:~__J ...with selectable bandswitching This compact electronic T-R switch (4%" x 4" x 4 !1 / ) does a big job in automatic break-in operation on C W-SSB -AM-DSB. Bandswitch covers 80 through 10 meter bands. Integral power supply. For com mercial a p plica ------_. t ions, it wi ll handle more than l KW Sir: 4 Enclosed is $9 .95. Please send me one of AM phone and up t o 5K \V SSB. "Fall your 3-D maps immediately. U.S .- Worl d- safe" design a utomatically keeps trans mitter connected to an ten na when Name , Call . unit is not energized. Matches 52-75 Address . ohm coa xia l lines. This is the switch you've been loo k City Zone State . ing for. See it at your local d ea ler, or Pl ease includ e at no charge with th is order a write t he factory direct. one year ( new) ( renew) subscription to 73 Price : $60.00 starting with the issue. (Two yean with two maps.) 13~&~ Send ord er to: 73 Magazine, 1379 E. 15th st., ,Jnt. Brookl yn 3D, N. Y. CANAL & 8EA VER BRISTOL, PENNSYLVANIA A PRil 1961 ; I (Letters, continued from p. 51) •UHF ~.s~~~::-i~~6B Grandpa VHF FAIRFIELD, CONN. U('ar " ·8 )" n f' . Refer ence your J anuJlr y Issue, p fl ~ e fl, " A Let ter from DIRECTIONAL POWER COUPLER Mamn," Tch, tch, tch ! w ayne. I r-e membe r- h "lir in R' 50 TO sao MCS - 10 TO 1000 WATT~ Wr,SG P and I ha ve h('lird h im do the " (;rtUidpll" bi t on 41NSTRUMENTS IN the a ir, but his name i~ n ' t Cliff Arkett. it:1I G. W, Rich" r t , ONE Paul Hud..on W A liAVJ STANDING WAVE RATIO n o ~'OIl "ray that If'{tllF1\ 1 ]'oll 'yr fi led. MODULATION MONITOR fiELD STRENGTH METER LINE LOSS 52 ohm model: L,5 2 Grf'f'tines O ~I: 75 ohm model: l75 December issue, paee 30. fiR" , 8. pot Rl w rper- shorted BULLETIN E-527 :5 to g round. P a ge :1:1. fi R". I, 12AT7 p in 7 shorted to 8. 24 SO Each unit individvcltv ol igned fa .Ja nuurv Isaue, J IIl ~e 41. t he lnat Pllra KrUph should have $ • in sure perfect meter ca lib ra t ion. read liS f" llow II : " Instead of hein ll patter n ed a fter a NUVISTOR PRE·AMPLIFIER half-wa\'e recttfter, thill circuit is a n adaptation of t he EXCEllENCE IN PERFORMANCE h a lf ""' 1\\". voltaae doubler, Since it is a yo lta... doublf'r device it u tilizes both h alves of the input sig na l cycle MODELS TO COVER: rnt. hor- t han only 011\' , wit h t he r esutt tne Increaee in 48·60 MCS- efftctency." MODEL G-SO A I S t'w land W21HW 140-1 SO MCS- 011 /,s 'za~," MODEl G-144 210·240 MCS- MODEL G-220 410·450 MCS W2N8U MODel G-432 You r Ma reh covet- s u re frilthtene,1 m e--I thought you'd moved to unotber- planet ! tot ,.. cell-mate explained it to BULLETIN E-5 124 me : the stone face is a California tool shed wh ich ill E o c ~ i~ dividu o lly 19 9S unit aligned for disguised all an Atlas launching pad ; the stone blocks $ • op timu m nOIS e fig ure. canlOufla ge the etr in take for the CD sh elter and t he 417_A GROUNDED GRID PRE-AMPLIFIER litt le ham shu ck in t he center is n neat ham shack j u~ t $2 1.95 LESS TUBE $39.90 WITH TUBE like t he ones we ha ve h ere in Virginia . I sur e f. el Elimino te t he guesswork from your matching prob better now lind look forward arrxicualy to all f uture lems. Quorter w ove line ar bolun transformer. coctes of n . Any frequency from SO to 500 me Any imped o nce rotion b etween SO ClOd 600 oh",s Lyn n Wi1801\ W 4JXD Write for bulletin E50-600 Alexandria. Vireinla e YiNs! CI u b Subscriptions Quite a fe w fellows ha ve been clubbing us to announce a cut rate subscription deal. \Vhile t his is against ou r basic policy of trying to break even, we mu st bow to t he pressure and star t some r ustling among t he club secreta r ies.Here's the deal : send us the names, calls and ad dresses of fi ve or mor e members a t $2.50 per member.. These subscriptions must start with t he next published issue. Individual Subscriptions The best wa y to get j3 is by subsc r iption. F ill out form below. How about sur pr ising a friend! T welve monthly surpr-ises a re only $3.00. Nume ...... , ...... , ...... , ...... Call • • • • •• • • •••• • $3 yr. Add ress ...... , ...... $5 2 yrs. City ·... ,, . ... . ,, ...... , Zone • • •• •• State ...... , .. . $4 yr. DX • • •• year-s. Start : Oct. Xov. Dec. Jan. F eb. ) Iar. (Check one) 73 Magazine ; 1379 East 15th s i., Br ooklyn 30, N. Y. Name . .. , ...... Call ...... , $3 yr. Address . , . . , ...... , .. , ...... $5 2 yrs. City • • • • •• • • • • •• • •• ••• • • • • • • • • • • • •• • Zone •• • • •• State ...... $4 yr. DX • • • • yea r!'. Start : Oet. Nov. Dec. Jan. F eb. Ma l'. (Check one ) 73 Magazine; 1379 East 15t h si., Brooklyn 30, N. Y. 52 13 MAGAZINE J)tar W a yne. To answer your queation in reeard to MM operation. I see no r eason why a passe n ge r could no t ob ta in permis_ eton to operate MM. There are som e prac tical eonaider-a u. S. #1 ELECTRONICS nons. It would be next to impossible o n a normal pas seng er s hip due to t he entennad needs, however it cuuld a division o f AMBER INDUSTRIA L CORP. Dept• .607 be done on a f regihter, You would have to co nside r t he 1920 E. EDGAR ROAD (Rig ht on Highway U.S. 1) leng-th o f the trip. of cour se. It would be worth while LINDEN, N . J.-ou ou from ESSO RESEARCH LABS o n 10nR" t rips such as JA, ZS o r rou nd-t he-world. First yOU s hould a rrange w ith t he passenger to m eet t he A N 'CRT. ' 1"onoouny Xml r . ; 0 · 90 me•. w/pua- ,·h · t~ .. _. .... •... .. • . . .•. ..•• .. . nt ... 12.95 ;\I a ster a nd get his OK. This is a good time to find out BC· GO] R~ . 20-2;.11 mes 10 I'rC5tt pushbut· it rou w ill have to bring you r own ac so u rce. Then yo u ton cIl, $11 .9 5 must notify the F CC that YOU have the Master's perm is BC·68l H ,·{'. ~ R l ll e K" lU ' , tlO:1 ex,·.']>t 2 j · :j ~f . t "io n en.t g ive t hem you r itine rary. The a ntenna w ill still 111('~ •• •• •.• .•• .• , ., .. •,• .• .• •.••. ••• 29. 50 he a p roblem, but o ne good solu tio n is a verttea t whip BC· 659 ~-" H,>(' , - X llli t . XI.1. ,·ontr.: ~o ..II.: fuate n ed to the rail o n the flying bridR"e ... coax ted, 2 j - 3~ . !l Ill . 10.9 5 P a t ;\lilllI' r K V.jC I BC -620 20· 2 7.9 OWl ••r,,1I' •• 1 l( ' · 6 ~,! 1 , hut no ~l'k r. . . 10.9 5 SCR · 522 X m fr .n l. 4 en., xtll ('< mH. :10 "'. I~ (;entlernen: tul "... H'ty p R'd .. . , ...•...... , .. 22.50 We w ould like to have y ou a nnou nce our f or-t hcoming BC· 6G4 xnn r . :W -27.!1 HI.· S, :1II \\', 10 -<'11. xld OirminR"hamest o n May 6 th a nd 7t h , ou r E ighth Annua l ('(lill I'''' .•• ..•• ...... •..••• • , •. ..u"" 8.50 Affllir . The m a in event will be, a s u sual. at t he A la bama BC. 6lW l'.mt> u Iu · - "n~ . t x....l'\ 27 · ;19.1 m{'~. 8.50 State Fairgro unds on Sunda y. w o nder- if it wou ld he DM·l ,5. 12T J))·n. mn l nr fot 111 '-;;"14 or 11t ·- r,,.; . 4.95 posllib le fo r you to co me down '! lUll Bankston W.jDf' f: Be-U8 Xmtr :>.3-7 IIl rS...... '"\>1<·1... u /lulJts &. xtal •• .•.. .••. . .•. .•• .••...... , ••• 1. 50 I.M'l' to R ill. bllt I'm tile [llI rst s/,.'aker at th e H'e,ft,.,n BC- 1206 He", 1 ~15- ·1:!1I k "K wi .; 1 1Ih{' ~, \I"rk. un ;\'en' York Hmnjcst on ,1lay fith in Rockcster, The Rirm in!l' :!4-:!~ vdc " .. 8.9 5 Ilumlcs! is OIl(' of Ill.\, [aooritcs , 1'/1 snrc tr)' to be there R·8/ARN · 8 n ...,. b.' II , ;~. I llI"S, ; l u b.,• • ",'lisIIh e I/ex t )·cor. , ..ill)' t""1 d .lI)· ~ u~ l~h l e f"r rt.'lllUle cont rol. tlo"'· " n..r. ere... 6.00 MN · 26 H ifl't" t1nn fI ,,,I... a.lal'l. om;a U I"rat!. I)t ar " ' a ynll', \\ I ....·ess : :\ 1~ ·: 6 f ,"r 150· 1:;00 ktl. & Conarututattnns on your edttortal in the Feln-ua ry is ~ll I'. Ie th n_ . ) I :-; · ~ U rot. 10"1'. ) I :">" - ~ Ii rem. l'onl r..l. ) 1:\' - ~ 2 .\ .1.. h "lI".. sue I At last the re ill a n editor- with a ut s enoug-h to 1'a1J1 .. ~ & In.l r. buok . • • ,. , ••• , ., .. • 89.50 I'! • •• s ta nd out BR"ai nst the liars and t.he c hea t even if it RT4 5!ARQ., lire. xmtr H ·50 111"1. w/eou.. Il'r &. rna}' cost him a subsc r-i pt fon or two. O -~1I0 m' met ..r on tr..n t 1'1111"1 . U I'<" t . You can imagine how a bridR"e or poker c lub would m it. SO or I I.'> . ~uO · ::;OO 1"1'" •••• ,. 29.50 tol er ate a ca rd c heat: that is exactly the a ttitutle decent P E. lOl um. : w /tllftr.•tart. ",I. )'. hal. ... hle in ';'-/1:" (ot :Ia/lla; OU! ~>oI) I' (" amllteur l( s hou ld exhibit towa rd the cheats who lie their 111 0,,(a, ... .,. ..•...... 12.50 way into t he r a n ks ( but not t he s p id t ) of a mateur PE.I04 I'.!ol . vlh. lI /\\' IIC- I1 ;, 1 In li / l~I': nut ra dio. Ilh' & 15,' .. , . 4.95 If a nyone ch er-ishes any P ollyannaish illusions. let him P E· 11 7 1'.:0: . 1·lb.; \'n lt ree : \\/llIhll' '" ha ll u t eompe re fig-u r-es o n the percentage ot flu nke rs o n In 6 /1 2 / 2~" ." L;;~ .;' /I.:; a; ,1 11:./ rcc !'O/1..'>v @ ; :; / ~ 0 / ; 5 " n ...... ,. Conditional C lasll code vs, General Class cod e o r T ech-, P E -2l 1 I' .~ , r ib.: w /luh~ .\ ,- Ih. In 6 /1 ~ /:!h nician Cl a ss t heory VII. General ClaHS t heory. One w OII I.I (~ Z1/13.Zn.: o ut 52.i/ l0.·,/ 6. 5/1; / I. :1 1 hnve to be nuive i n deed to belie ve that ho nes ty is a n 130v «,; tlO /42 ma/ Za / :iHO/ 4.i O/I ; rna . 7." att r- ibute of tho vast majority of the takers lind the MP -22 mast h 8. .. fur mohll.. !llIUm l ••.•. . lit'\\' 1.95 !C hen of " m a il o rder" license exam inat io ns. The-ir- in T . 26 moh ll.. rlwsl n,lk n,·\\' 1.00 l~ri t}· s ta nds self-conde m ned b}· the utte r l}' inc r edib le 5 f or 56 Synehro motor. g r.I t:.'·. I,Ot· I'O. II..... 15.00 numbe r o f pa ll"ing grades. DY ·11 dHI."",H>r 2; ...I.. 10 ; 50 /if' 3:;0 12.95 Again. wayne, cong-r a t ulationa a nd g no d luck. It ma y ma ...... •... , ...... •. I/ n,'" he that if you keep po unding long enoug-h you ca n per _ 800· 1 <1 )11. 2 1 ...10: to l1.i 1'91'. SoO I"I'S, I k va . .• ,., ••. .. .• ,., •.• . ..•• ,• .•• IIt'\\' 9.9 S s unde t he FCC to return a m a t eur radio to r n.lio amn t eurs. Car l C. Drumt'lln . W SEIIC TERRifiC B4RGAIN ! GO·9 TR4NSNIITT ER, $59 50 100 W . D.3·1B NICS. BRAND N EW ...... • D ea r ,,' a ynll' . All m y past issues of c u rrent hum jour nals a ttest to II TH OUSAN DSOf ITEMS-TH OUSAN DSOf BA R6AlNS fniling that I would s u relv like to see yuu correct with Wrlttl fot tree ll sl lnlt- :!i % <1 "I'nsll 011 c.o.n. ord.'I I 73. My cove rs a re well ma r ked w ith notntiona liS to the :\Un lmum order t ,i.OO . All I'rl..... r.o.h. 1.llllll"n. X. J . :O: ome conte nts. Now if one put the conte n ts on the cover, quantltle1 110111 e <1. J' rl ~ :-:ubJI'Ct 10 (' hange Wlllluut Xot kll'. I More on peqe 55 ) MOBIE JRANSMITTfR RCA PRECISION SOD KC VHF JRANSMITTER BRAND NEW ~ Un. 5&11 c.,.. t al P.rl.cl for i me'er .." w...t or InIO CRYSTAL OSCILLATOR _ lor I·t! t meie r em ~51' .tPP11· " 1.... Lale. t ie r . Mod.rn da · mod d..l p. tI... .Im. 0D17 , u... two 1201'. Llno fliK . ' lIbt illdlMl' 'lnpe A_rill nlo inC buUI-ln' V. Iwln Telro APRil 196 1 Sl ALASKA ARGENTIN A AUSTRALIA CANAL ZONE ENGLAND GERMANY HAWAII INDIA JAPAN ME XICO PHILIPPINE 'S PORTO RI CO SOUTH AFRICA U.S.S.R . Propagation CITIZEN BAND TEXAS CLASS "D" CRYSTALS All 22 Fre-quentie, in Stock Charts """ 3rt! oeeetcee. .005'X. tolennr_to meet .11 10' C C requlremen LJ . lI The bands li sted are MUFs and a higher The followl"8 Clnl " 0" Cltizn Ba nd frt Quene ~ .. In Itock If-eQulllcies lil ted In mlgacyc les ) : 26.065, 26.975. 26 .~a.5 . band will not work for the time period listed. 2700::; , 27.01.5, 27.025, 27.035, 27.055, 27.065. 27.075, 27.085. 27 .10 ~ , '7.115, 27.125. 27.135. 27.155, 27.165. Lower bands will work, but not nearly as well. 27.17.5 . 27 las . 27.205. 27.215. 27.225. Times are G:\IT, not local time. .\Iar t"l 'ed l· r)·,t,,1 i etl Inr G fuue, uooser. C iti·Fone and lIa1ll c~ a ll ers Units . .. $5.90 per let. S iledly euutp nen l make. These charts are to be used as a guide to •••••••••••••••••••••••••••••••• ham load ope ni ngs for the mont h of April, • RADIO CONT ROL CRYSTAL S IN HC6/U HOLDE RS • 1961 to t he various coun tries list ed. I will be • f' peclly frc'lueney. 'A:" pi n Ipuinl, . . pi n diameter .05 • • (.on nln tll.mete r, atld 15t) ...... •...•...... $2.95 u . • interested to hea r of you r results in using • FUNDAM ENTAL FRE Q . SEALED CRYSTALS • these charts and to know what ot her areas • In II CG/ huMen • • lo'rolll IfllO K C to 4000 riC . 0115"" 'rcteeenee ...•..$4.95 ea. • you might wish included in future charts. • From 1000 I\C to 15.000 I.; e an)' fre' IU en, y • • .00::; 1<> Tolera or e $3.50 ea. • • SE ALE D OVE RTO NE CRYST AL S • • ~\I ]>p lle tl In IIl t·tal llC6/ U h" ldeu • • t'tn 6 11~ .. llIg .4"; 6, di amet er . 050 • Advanced Forecast: April 1961 • 15 to :J O -'IC .00::; 'roteeen ce $3.85 ea, • • 30 to f5 -,IC . 005 Tolera .wf .•...... •.•....$4.10 ee, • • 4;:; to 60 -,IC .00;) Toler ance $1.50 ea. • Good 1-4, 2 1-30 •••••••••••••••••••••••••••••••• QUARTZ CRYSTALS Fair 5, 8-10, 18·20 FOR EVERY SERVICE All cryolals made from Gra,le " A" Im DO rted lIuaTlz.-ltrountl and "Iehed 10 Bad 6-7, 11- 17 exact Ir e ', uen r l e l . Vnrondltlonally l ua ranlel'd : S Ullp lled 10: FT-2 13 holden MC-7 holden P tn opaclnl 'A: " r'tn sp.cln. ~ .. P in diameter .003 }' In diameter .115 (Letters fro m page 53 ) DC· 34 holden FT -1 71 holdera rimjlar- to the Rea der 's Dt srest, it would eliminate the P i n . p~c l n g %, •• P in spacln l %, •• neceasttv of slw nding Ion " hours ope ning covers ami r'tn dia meter .156 Banana plni lookinl( for some par-ticulu r idea t hat is ha lf h idden from MAD E TO ORDER CRYST ALS • S peci fy holder wanted t he longpaat, 1001 KC 10 2600 KC: L. R .S ha ... krlford KS II SW . 61,% 10Ier8ncf. • .• . •...• , • . • . •.• . • .•... .• . •• . .•• .•. $2.oo e• . .005% to lfr.nICe . •• •. ... .•...• • • ...... _, • .. .•• "• . 52.75 e• . R oy oh bo)' 011 011 011 t('e flO 10 )'011 '11 2601 KC II 9000 KC : boy bo)' bo)'. line .00::; "" te teeenee • . • .....• .• . •.• ...•...... •• • . • • ••• . $2.50 ea. IUTer j",urlill c 1I0w milch t r oubl e 10 Iry ' 0 makc t he cen'er sen KC t. 11 ,000 KC of each: iss ue of 73 d ifferc,,' [rom UII )·tlli" [1 )'OII'f'e .fN'1I .00:;% ' "lennI''!' . •.• ,., _ $3.00 e'. before alir! artistic ... alid rd w t do rt'C yt't ! Rcts t Look Amateur, Novice, Technicia n Bond Crystols lu -re, 1. , R. , if :\,{)U don't mind hOfl;Il Y lIlo!!o::illl's 1('it h CO!' .01 % Tolerance . , . S I.50 e8.-1l0 meters (370 1-3 149 I{C). crs lik(' that rdry !l ot just rip off thc [ronr CO f'Cr and pagc 40 meters (1152· 1108 K~ l . 1:1 ureters (.0:.\f ·701l2 KCl. 6 meters one of 73 and thn l you'll /r Ot·c tlrc T'able of COff tCllts f or (S335-8650 I';C) "'Ilhln I I":C I ~ q ur n c l tl ;\'OllY C01 ·cr. I IIO I'C someone apprcciatcs OIlY corers. Iliad Jo"T -2H I.attl<-e Cr)"Jt. 1s In . 11 trom 3iO KC to f or sercrot years made ",idgcI 'IOtes all t ill' bindin.Q cdge 5 10 Ke (.11 n IC ept 45" KC . nd 500 I..CI 50¢ ea. I'ln Ipad oc 'A: " I'ln d lam" te r .0:'3 of III)' QST's alld CQ's of tllc m ore illtcrcstillg contents, -'h.t..lte-tl p.ln + 15 eycl ts $2.50 per pair • It r('as onlv IlatllYal rhew that I shollfd irrst;t llte tk is S clll'Plli' 200 J..:C Cr,. ltal• • $2.00 n .. : 455 1":C CU·l tall . $1.50 e~ .; 500 hC r..llc/l I b"ca",,, editor of CQ. S i ,ICfO 73 'U';II IIOt be hllt';119 CfT"t als , $1.50 ca,; 100 KC Freqllen<:y Standard Crystall In this bilrdiuf/ cdae due to till' saddle .ftitch bi"di".i1 7( ~' arc IIC6/V holden $4.50 ea.: Socket fur Jo"T - 2 ~3 eryual 15¢ ea. : I' ,, ~ I -ocket t nr ~"r - 24 3 cl'nlal,. 15¢ ea.: l'ocketl for MG·1 and luiu!!. tlris S)·.f/cm is not /,ractical. I bd iel '" that tJr c con FT-l71 cry,tata 2.5t! ea. : Ceramic Bot ke t for H C6/ V cry, tab ! 'I' lI i CI1CC of beillfl able tv /a \' your m a{lo::i llc [lut all the 20t!ea. tabtc is of more i lll p o rtO lrCl' tl' OII //(/t';Il!I all ('diU' stick Oll t Write for new free tatalng #860 eomp lete with oscillator cl re uih of fM bookshrlf f or )'0" to rcad ... rartiCll/ad)' since we 1I0':c so t'("r)" mallY ("OIlSlrllClioll ertictes , ASK YOUR PARTS DEALER FOR TEXA S CR YS TA LS see bl . r ed dllplaY . .. If he COtin't ItOd l Ihem . •eod u, Df'a r " .a)·nf'. hil name and ord er dlrtl'1 from nur n orid,. luto,.,.. The Fiat 500 isn't much o f a sports ea r . but vou NOW I Jo;nl lneerlnlt IImplel and sm. 1I 'l lI . nUt lts lor proto mig'ht be able to direct me to someone who has cleaned trpee now made either at Chicago or ~·t . "Iyen P lant. 24 t he 2 meter ignition noise out of one. I' ve Kot one o f the Hour Ser\'l ce! IN CH ICAGO,P HO N E G L lI" st ~n e 3-355.5 little monste rs, w ith a G"n l< et and It Hi-Guin whip, which is fi ne w hen rhe motor' s off. but un ear-basher in mo RUSH YO UR ORDER TO OUR NEW PLAN T tion. (That Gonset is Ketting a Lamb-eircuit nuvistor Use coupo n below flW lit Cia.. I hipment. prffi m p shor tly.) The iKnition leads are pretty close to ~2 wave, which improves the streng th con! Jim Kyle H A V f<: you designed or built an or ig ina l item difference between good results and none at or equipment'? \Vould you like to have a ll for t he guy who duplica tes your effort. cash in pocket to pa y for it? Or prestig e Along t he same line, include a complete parts a mong' your buddies? T hen write it up for 73. list, with ma nufa cturer's type number of each T he only way in which we can continue to pa rt if available. offer more construction articles per issue t han Remem ber, a lvv-a ys, that you're writing for any ot he r ham magazine is for you, dear read other hams. T his means t hat acceptable ab er, to descr-ibe your design and construction breviations and idioms which will be known effort s. To encourage you in t his endeavor, we to everyone a re acceptable. On the other hand, pay legal tender for your words. But to make it's no excuse to be cute wit h excessive use certain t hat you accomplish what you set out of Q signals a nd such (73 is printed, not tele to do, here are some hint s on how t o write for g-raphed to its subscr ibers) . If your ar ticle J:l. includes technical discussions, watch the level. The best guide to the type of article, we Don't explain Ohm's La w in one-syllable want, naturally, is the group of articles pub words, but on the other hand don't take for lished in each issue. H owever, don't carry granted a detailed knowledge of rada r-scat this to extremes. After we have three articles tering principles either.Let common sense be on the sa me type of equipment, we'd sort of your guide here. like to concentrate on other areas for a few Now, let's look at the mechanical details of issu es. But ca reful st udy of t he published ar your article. F ir st, it should be typed-c-pref ~ ticles with attention to t heir organizat ion, era bly with a typewriter, not a Model 26. wording, a nd RPPI'O Rc h will pay dividends. T he manuscript should be double-spaced, on Ha mming is a hobby, not a business (though white unruled paper. Keep a car bon of it , many BF s would question t his statement), but submit the origina l. T he r eason for this is and your article should read interestingly t hat t he carbon tends to smudge during edit rather than like a business report.In general, ing, and becomes difficu lt for t he pr inter to try to describe the equipment as if you were read. telling your buddy down the block how to build Include your name and address on each page it-for in essence, that's what you're doing. of t he article, preferably near t he top. T his So far as organization of t he a rticle goes, lets us put it ba ck together should a gust of a good r ule is to tell your story t hree times wind mix it up with others. For t he same rea or in the words of a n excellent ba ck-country son, pages should be numbered consecutive ly. orator, " First I tells t hem what I'se going to With t he article complete, you'r e only half sa ).', then I says it, and then I tells them what done. Illust rat ions are a must. I sa id." At t he very least, a schematic is necessa ry. By this, we mean to give a summa r y of the If chassis layout is critical or important, a entire article in the first couple of paragraphs. sketch of this is needed too. All such line art This lets the eventual reader know if he's go can be submitted as neat sketches, since it will ing to be interested in it or not. T hen go into be redrawn to 73 style by our draftsman. The the detail. Finally, sum it up briefly at t he end. key point is to make sure that t he sketch is Speaking of detail, be sure not to leave it not subject to misreading beca use of crowded out. Not too long a go, one writer (a staff lines. member at that ) wrote a long antenna piece Last but not least are photographs. While - a nd after doing so, discovered t hat nowhere we ca n and sometimes do print cons t ruction in the article did he give any dimensions or articles without photos, we 'prefer t ha t pic tell how to build the skywire ! Luckily, this tures accompa ny the article. error was caught in t ime-if it hadn't been, F or one thing, a good photo makes more the mailmen would have been del uged (if t he people want to build t he item. For a nother, article had seen print in such shape). it's proof to the unbeliever that the equipment Include all ca libration a nd a djust ment in was actually built. And finally, a clear photo structions where necessary. This can make t he will show many details which can never be 56 13 M A GA Z IN~ shown on dra wings or expla ined in text. Photos must be sha rp, clear, and well-light PE-162 GASOLINE ed. If photogr-aphy isn't one of your other hobbies, t he best bet is to locate a friend who ENGINE GENERATOR knows it well a nd enlist his help. We prefer FOR POWERIN G, RT.77/GRC·9 that prints be 8 x 10 glossies, but good 5 x 7 BC·l106/ SCR-694 COlnl'llrl. liJ:'hl \\I' lJ,;hl. Il"n ahll' 1'! l'ft rh' prints are usable, as are prints on smooth f/.l'll l'nllng ~ ~ I fo",btl ,,!: IIf a 1 II I" :1000 UI' ~I I fJ-IIIl''''r. a ll' ...... 11'<1. e f )·d l'. semi-gloss paper. manual rtlPf' ~U rllllg l:a..olll,1' png illp 'Ur....II)· 1"<""' 11'<1 to a III'••hllnt "-"'111<1 .•" It I'vlll'd. tour pole ;: ~I'ral"r ntatned til Technically, you should either "paint with a framl' of I"" ub r MnUmrtl"" n""llllp,1 on r uhl...r . h,,,,·k light" or use bounce-lighting in making equip m"IU' tl n J:" . (;'·'1O'ral or .. lie 511 u"l \"lur" t. .flf fwll...-l. 4 t>ol l'. hall h..ar lftlil. "1110 flUllllIl ot G.:!/' " I ~I ' 3..j " tIlll and ,,!Ill ment photos. Cameras smaller than 6 x 6 eM ' · llC ~ :IO / ~ .j O ~ I.\. I.·" il h a ~ .I"nfllon II ,, ~ t"r " " "' '' ~' l h 'lI: fahlt-s r" r us,, wil li vartous r adl " euu tp. It'hl I~ l"<)ln t,ldp \\'1110 t "" l~ negative size seldom give acceptable result s. ."- III .lrlletl'lII ho" k. ~i 1,1" : 17'f., x l ro l;< ll' I I". wr.: $34 50 And if this paragraph leaves you cold, fi nd 57"1! Ihs. ~hl' l( . \\"t.: 12,"; II ". I· r lfl'-,!tl,.:r-; ,·,.. : . .. • ('1I ·1 1l~ 1 ' 1' .\ HL.: ~ f " r '· "Il ll ,~'tl ll l( ailo\',. l'''" ''r 1·1111 I" IH:' I:lU n a friend as advised earlier. (Maybe la ter we'll Ind lIT·" n er . -Tran•...... 55.95 have an article on the taking of equipment RCA RECEIVER photos. want one?) With all things accomplished, you're ready R-320/AR-88 II Tuhl' s ul...·r hflr"'I)- Il.. " 11h .. to send your manuscript in. Wr-ite a shor t f r"'I"l'lIf)' r ll lll: l' 11'''111 " In to :1 :!. Ullfl KC In si ll' " a u " ~ rI .,.ll:'''''\ note explaining what it is, enclose return ror fL"" 'pll" n IIr .DC ~ w\\" & ('W " I l(nllh ; 011 111111 lmlll'da,u-f 2,:; .'I< ronn ohms. Om' postage if you wa nt it ba ck in case of rcjcc lllninlo: enlll r,,1 wllh hawl 81>1'l'a'\ 1,lu. 0 ,.. r"II"",1111o: ton tion (unhappy thought-but it sometimes hap t r ols ; n . •' I Ja lll..\ . 1" rla tn , IIn-Tnlll. - It,·,· )1\\' ·11,·,· I·\\'. Ill-' T I> lIe . ..\ nl -.\;lj.• Hau,1 l"I llllllo:l' . ,,·It'('l hll.\'. llFIl II IJ.I.•\ VI' · pens) and mail it in. Before very long (the ~ la "" :1I-) l a ll" lt l ~ nl ~ e 1,1I11 11 ,·r-.\\·C :-O n.... T.l 'll ll ..r. ~ " I . ~ J.l m lt pr ; .bo 1'1",,"1' J efk. ('oml,Jel p wll h TlI hl's : a / Il l"(; 7. exact time varies with the other activity in ~ / r,Jo; . 21t.11t1. l / f$ .\7. l / IlKI; . 1/ ,,\"3. 1/;;:-:J7 • •\ I /V It -1511 : l ~, ;; KC IF. Ooe rates fm m 1 1~ /230 "olts flO n ']p. Ih ck p. m-I the office) you'll either get a check of a re mOllnllng . 1 ~,1~); n x 19'.. .. ( ~" ulolnd) W I. : !I ll 11>,. 1:51'<1 . j ection alip. If you've followed the advice Ch...·kl' I"ong Join. A.denn.. for 6 lU e . e r s fEATURES Designed fol' m ClXimum forword g ain. Gommo Moteh fol' co- ax f e eder. Finest g ra d e oluminum tubing . Exceptionolly st ro ng s ince thel'e are no drilled hole s . All aluminum const ructi o n e lim ino tes e le ctrolysis. Entire b eom and su p p orts con b e grounded for S PECIFICATIO."iS )IOD F:L 1.J.6 light ni ng protection. Dr li"" Cr,,'rr . •...... • , • •.••.. 50.5 ~IC Coin • •••• • ••••• • • • •• •• . .• ••• •.•.• •• ••• 1 3 DB We o re proud o f this new Lo n g John Antenno. We' ve tried to put in every f eature you could wont. The reo FIB Ro';o • •••. • . . •.• . ••• . ••• • • • • . • . • • 2 3 U B suIt is 0 reosonobte cost hi gh gain beom which con J!' .S.W' . R • •• •• • • •• • . 1 : I , Ir u Ih." 1.5 ; I .. lIhln 2 MC Q ea,ily be put up ond which will stoy t here proctieally 1I0r• • # .. 0 ..' JI';,/lh . •. • • . • • • •• • 4 5 ( Ih I'''''f HI-PAR PRODUCTS CO.+ FITCHBURG, MASS . APRil 1961 57 (Automation from pag e 291 doubletal k, t he circuit ca n be by passed by a switch. Be ext remely careful to locate t he switch properly. Incorrect positioning in the circuit could destroy much of t he transmitter . Ha ving described a spiral of ever-decreasing radius, we a re now ready to sta rt over a t the microphone. Note that it feeds a three-way splitter . This consists of three t riodes whose g -r-i ds and ca thodes are in parallel, but whose plates feed three sepa rate out puts. One out put goes to the tr ansmit ter itself, one to the vox unit (together with sta nda rd a nti-trip sig na ls from t he receiver) and t he t hird to the Ta pe Log Unit. Since t he microphone is on at all times in " We have fOIOld t he Rider S ound-N-Sight Code t he Log circuits, a per manent and complete Course to be a successf ul training me thod. W e are log is ma intained. Exact time of ever y word currently employing this method with modifications to fit our t rail/ ing reouiremente, lVe have found you spea k can be determined by comparison that this method of teaching code saves an appreci with t he WWV signa l recorded at lower level able amoullt II f time ill our training program." Thus on the same tape. While not checked out with s t a t e d t he C omm a n d i n g Officer, U. S . Coast Guard the F CC, there appeal's to be no reason why Training S t a t ion , Groton, Con nectic u t . .. Proof o nce agai n t ha t th e Rid e r SOU N D-N- S I G H T this log could not be used instead of a written CODE COU RS Jo~ is t he easiest, f astest wa y ever document. (If the Radio Inspector rules other developed to learn code. wise, you ca n always hire a stenogra pher to T he NAVY TIM ES gives details o f t he successf u l transcribe it for you.) Coast Gua r d test that led to the adoption, at the Coast G uard G r o t on, Con n. Train ing S t a t ion . "The That's it- the whole incomprehensible mess. Arm y at Ft: . .lJonmouth, N ew J ersey, adopted t he With care, it could be built in a standa rd six radio cou rse. The CoaHt Guard was impressed with foot relay-rack cabinet for something less the A rmy result» au d gave the method a tr y . . . t ha n $1,568 (if j udicious selections a re made A ccording to t he Cuast Guard t rial runs, the men ta u gh t by t he 11ew method take a lead immediately from sur plus ) . That's why it's never been built in building speed a1ld remain ahead by nearl y 100% here, and probably won't be in t he near f uture. throughout." But if you have a pair of oil wells in t he " Alter 30 hours for example, the first e%perimental back yard, and don't mind a lit tle tinke ring, group alJcraged 19 wordH per mitlltte, the second averaged 16.9 and the third 18.5. Men in the first you too ca n have a completely automated class under the old method were clocked at 9 w ords sta tion (and w ith a little more engineering, per minute fI t this lw illt and those in the second it can be made to operate itself, freeing you hfld 9 .,$," words. There w a ,~ n o comparison in the from the drudgery of contests and the like third class, since all were o n t he new met hod." a nd leaving you free to read.. .. 73 HERE'S WHY YOU LEARN FASTER WITH THE RIDER SOUND-N-SIGHT COURSE ~ • applies Reinforced Learntnz-c-peycholoztcal principle IIroved successful by A rmed Forces. II 1 • USl'S LP records to teach you to hear si gnal pattern cor II I II1 rectly and ident ify it-how to tra nsmit. • uses iden tification "nash" cards to teach you the cor- o 0 000 I I 1 I II II I rect letter usaoelatton wit h each t;i g na l pattern. o~o • has " check yourself" progress cha rts, · . . plus a n imllR'i nary inst ructor (in com plete a nd novice courses) p rovides correct a nswers to speed code learninK. III I11 I1 1 Ma ny people have learned to receive 5 words per minute withi n !.l~!l bc u rs. Eliminates code plateau barrier! 3 INDIVIDUAL COURSES- There', one for you II1I11111 COMPLETE COU RSE (0-20 words per minute) - S ix 10" LP o 0 o 0 records (192 min utes of recordi ng, 2K recordings) . 47 0 0 0 0 0 0 00 0 0 00 ~:: identification cards, book ,# HEC-020, $ 15.9 5. o ::: II 1II I 11 1 o 0 0 0 o NOVI CE COURSE ( 0-8 words per minute)-Thrl'e 10" LP ~ :~ 00 0 records (9G minutes of record lnsr, 28 recordings) , 47 0 0 0 ~ :: I identification cards, book #REC· 08, $9 .50 . I I1 111 00 0 I I ADVANCED COURSE (9-20 words per minute) -Three 10" 000 LP records. ( 96 minutes of recordi ng, 28 recordings), o book :REC-920. $8.95. Rider has many titles that spell more a mateu r radio en joyment- GETTING ST ARTEDI N AMATEUR RADIO, B UILDI NG TIlE A MAT EUR RADIO STATION, R ADIO OPERATORS LIC ENSE Q & A MANUAL 6th E DI T ION-to name just a few. They' re available at book stores or electronic distr ibutors, or order direct. Write for new 1961 cntaloa. P rices subject to change without notice. "I got on the air alright Ma x, but '1010 I can't tu rn it off." 58 13 MAGAZINE A IR FORCE MARS Technical Broadcasts Give Your Shack Ve ry interesting te fks given eech Sundoy f rom 2-4 p .rn, (EST) o n 3295- 7540-15715 kc. That Professional April 2-No broadcast todev. Look April 9- C <'l pt. J ohn D. Griffith s: Th eory of Really dres ses up the she ek. Wall o r table m ou nt. Steel Spe ech Commun icotio ns. ca$e in b lack o r g rey. bright red letters a n w hite b a ck. Ap ril Ib-C <'l pt. J ohn D. G riffit hs: Mode rn g ro u nd. 10V2" x 3 112" x 3". Ava ila b le in ot he r Ian. gaug e $, with you r call lelle n , or w hat d o yo u want it to Techniques in Speec h C ommunicotio ns. $a y ? . .• a d ollar extra. AC/DC 6 · 12 · 120v l $pe cify). April 23- Phill ip E. Hetfi eld : Ba sic Electronics Ca n $hine o ut b ock w indow of your car 01 night, for the Radio Amateur. m ou nt o n your r ig , ouhide shock d o or, or w he re ha ve yo u . April 30-EdwiHd A. Neal: C ustom Building vie Home Cons truction. at your d istributor May 7-W fH re n Bonne y: Telece try; Its Pur pose, Its Function . (Indian s from page 26) STELLAR ELECTRON ICS, Box 82, Garland, Tex. :\Iak<,s him think, anyhow. Tell him you actu ally gave your phone n umber over the a ir and • asked f or interference repor-ts (if you d id SAVE TIME AND MONEY INCR EAS ED VERS ATIL IT Y EL IMINAT E OBSOLESCEN CE remember he hears your transmissions !) T ell BUI LD YO UR EQUIPMENT him how you checked various neighbors and W IT HVANGUARD " PCM's" .. they said " No interference" , . , mentioning " p r inte d circu it modules, makes of sets and a pproximate age if you can. • l argest $elul illn of etr A mi another redskin bit es the dust! Now f or uit$. n umber seven. • l ow ut eost. • Ev ery mlldule i$ teated, " ,1fy neighbo'r says. . , ." or h is w ife's U ncle lual1lntnd and tompiehl wit lJ tub e s. t ransi stors , Lou ie . .. or the man who checks his wife out a n d crY li ta l1i wlJere reo a t the Supermarket , .. or any other competent 11II ired . $ 14 .99 li$t and quali fi ed expert. SPECIAL THIS MONTH NOW $7.49 10 MET ER TRANSMITTE R thi$ month only H er e's where the F CC is a r eal friend ! T ell Jol I"...UkaU" m: t >r)'stal eont rortea , ::; watts Inl 'ut 10 tiA l:S fina l, you r neighbor that you don't doubt that he ,j :! " hill link outl>U 1. I'''''..r r....luh ..m..l1t. : 2.j O " . He @ 30 rna.. fl.3 ' •• ~'i . 4,'; a. has been told thus and so for a minute, B UT Send li tam ped st lf. addrtued enveill pe fllr Cll mplete li lit of , , , and cite the }m hli.'{h ed etatement. of the VANGUARD PCM ·s. F CC that about 95 % of ALL TVI complaints VANGUARD ELECTRONIC LABS De>:,t. H-4, 190-48 _ 99th Ave., Holli$ 23, N . Y. t hey have investigated turned out t o be due to r eceiver mal-function ( W. L. Kiser, Chief Fresno Hamfest Ma y bth E ng ineer, F CC New York a mong ot her s have publicized t h is fact .) T hen you can lea d into Regis t ration a t 8 am, Tow ne & Country t he filter st ory and take it from there. Lodg e in F r esno. Tech nica l talks, demonstra Two more lit tle indian s alwa ys come in t io ns, swa p table, mobile field intens ity meas pairs. " I'll have th e FCC run YO lL off the air" u rement s, h idden t r a nsmitter h int s, ladies and " L'Il epoak t o my broth er w hose 011 t he Ciiy luncheon and specia l entertainment. The ban Cou ncil a nd tunic yon l'ut out of business." quet at 7 pm is included in t he $5.50 r eg ist r a If you g et t his pa ir, r oll w ith the punch tion f ee. R eservations : Box 78a, F resno, (Now turn the page I California. • WEST· It'. IN THE ••• _'. ", r.==:o... V\VIE S~~I ElliiN I~IDIIO and ftLEVISION SUPPLY J.CO. -'~& '. I " _ ' -~_ -c - ~ fOR OVER 25 YEARS ONE OF THE WEST'S OLDEST AND LARGEST fiRMS DEVOTED EXCLUSIVELY TO AMATEUR AND' ELECTRONIC EQUIPMENT. 1331 India St. San Diego 1, Calif. P. O. Box 1728 BElmont 9-0361 APRIL 1961 59 80- SURPLUS RADIO CONVERSION MANUAL VOLUME NO . I (second edition). This book g ives circui t dia Radio Bookshop grams, photos of most equipment, and rather good and complete conversion instructions for the following: 8C GOOD G RI EF. don't you ever get the yearn to 221, BC -3-42, BC-312, 8C·3-48, 8C·-412, 8C0.6-45 . BC -9046B, I ~ Mn ? SCR -27-4N -4 53A series recelvers conversion to 10 meter RB shi pping dept. is o!l nx iousl y eweltieq your receivers, SCR -27 -4 N -457A u riel transmitters (conver sli q htest stir. You know, jf you buy one book" sion to VFO), SCR-522 (8C-624 a nd 8C·625 cc nverstc n month you might end up with " fll irly d ecent ref '0 2 meters). T8Y to 10 and 6 meters, PE-103A, 8C erence li brary? By the way. RB policy h <'J 5 elwe vs 1068A/ 11 61A receiver to 2 meters, Surplul lube indeJt. been Money Back, no questions asked. cross lndex of A/N tubes VI. commercia l types, TV & FM channels. $1.00 I-ELECTRONICS & RADIO ENGINEERING-Terma n. One :)f the mod complete text books ever p rinted. 1078 81-SURPLUS RADIO CONVERSION MANUAL VOLUME poges, Theory, but ecay on the malh. $15.50 NO . II. O rig inal a nd conversion circuit d ia grams, p lus photos of mosl equipments and full conversion d is 2 - ELECTR IC AL EN GINEERS' HANDBOOK cussion of the following: 8C·-45-4/ARC-5 rece ivers to 10 Pender-Mcllweln. Th is huge book should keep yo u melers. AN/APS-13 Jtmtr/revr to -420 me, IlC --457/ARC-5 busy for mon ths just re edinq the interest ing facts it Ilmtrs to 10 meters, Selenium rectifier power units, ARC -5 contains. The re is hordly any p roblem in communi power and to include 10 meters, Coil data-simplified ca tio n or electronics th M you can't find cove red VHF, GO-9/ T8W, 8C-357, TA-12B, AN/ART -13 to c e he re . Excrucia ting ly thorough. 161 8 peqes. $10.00 windi ng charts, AVT -112A. AM-26/ AIC, LM frequency meter, ro tators, power chart, AR8 diagram. $3.00 5-ANTENNAS- Krau s (W 8JK). The most complete book 82-SURPLUS RADIO CONVERSION MANUAL VOLUME on onlennas in print, but largely design and theory, NO . III - Origina l and conversion diagrams, plus some complete with moth. $11 .50 photo of these : 701A, AN/APN-I , AN/CR C-7, AN/ UR C-4, CBY-291 2S, 50083, 50141 , 52208, S2232, 52302·09, FT 13-REFERENCE DATA FOR RADIO ENGINEERS. ARA, 8C--4-42 , ,",53·455. -456 -459, 8C·696, 950, 1066. 1253, Febles. formulas. graphs. You will find th is reference 2-41A for Jt tol fi lter, M8F (CO L--43065), MD-7/ ARC -S, book on t he desk of elmost every electronic en R-9/APN--4, R23-R-28/ARC-S, RAT, RAV, RM ·52 (S3), gineer in the country. Published by lntemeficnel Rt -1 9/ARC_4, SCR-27-4N, SCR-S22, T·15/ ARC·5 to T Telephone and Teleq reph. $6.00 23/ ARC -S, LM, ART·13, 8C·31 2, 3-42, 3-48. 191. 37S . Schema tics of APT -S, ASB -5, 8C-659, 1335A, ARR -2, 20-RTTY HANDBOOK-Kretzma n (W2JTP). A-Z of ham APA10,APT-2. $3.00 Teletype. Very popular book, low supply. $3.00 83-THE SURPLUS HANDBOOK, VOLUME I- Rece ivers a nd 21_ VHF HANDBOO K-Johnson (W6QKI). Types of VH F Tronsmitters. This book consisls tmtirely of cirevit dte propagation, VH F circui try, component limitations, on gram$ of lurplus equipment and photos of the gea r. lenna design and construction, test eq uipment. Very One of th e fir$! thingl yo u really have to ha ve to thorough book and one that should be in every VHF even start considering a conversion of l urp lus e q uip shack. $2 .95 ment is a good circui t diagram. This book hal the fo llowing: APN·1 ,APS·13, AR B, ARC --4, ARC -S, ARC -S 22-BEAM ANTENNA HANDBOO K- Orr (W6SAI). Ba sics, VHf, ARN-S, ARR -2, AS8-7, 8C-222. -312, -31-4, -3-4 2, theory and construction of beams. tra nsmission lines, ·3-4-4 , -3-48, -603, -6 11, -62-4 (SCR- 522), BC-652, -65-4, matching devices, and test equipment. Almost a ll ho m -659, -669, -683, -728, -74S, -76 -4 . -799, -794, 8C-923, stotions need a beam of some sort • • • here is the ·1000, -100-4, -1066, _1206,-1306, -1335, BC·AR-231 . only source of basic info to he lp you decide w hat beam CRC-7, DA K-3. Gf-Il, Mark II, MN-26, RAK-S, R A l -5 ~ to build or buy, how to insto ll it, how to tune it_ $2.70 RAX , Super Pro, TBY, TCS, Resistor Code. Copocitor Color Code, JAN/VT tube index. $3.00 23 _ NOVICE & TECHNICIAN HANDBOOK - Stoner (W6TNS). Sugar coated theory: rece ive rs. tra nsm itters, R235-RADI0 CONTROL fOR MODEL BUILDERS-W inter_ power supplies, a ntennos; simple construction of a One of the best a nd newest books available on RC . $4.25 complete station, converting surplus equipment. How to get a ham license and build a sto tion. $2 .85 R245-HOW TO USE GRID-DIP OSCillATORS-Turner (K6AI). Construction & uses, on important book. $2.50 24-8ETTER SHORT WAVE RECEPTION-Orr (W6SAI). How to buy a receive r, how to tune it, olign it; build ing occessories; better onlennas; QSl's, mops, aurora zones, CW reception, SSB re ception, etc. Ha ndbook for short wove listeners and radio amateurs. $2.85 Order Form 28-TELEVISION INTERfERENCE- Rand (WIDBM). This is the authoritative book on the subject of getting TVI out I 2 5 13 20 21 22 23 24 28 32 33 of your rigs and the neighbors sets. $1.75 40 52 57 80 81 82 83 R235 R245 32-RCA RADIOTRON DESIGNERS HANDBOOK-15oo pages of design no tes on every possib le type of circuit. Fa bulous. Every design engineer needs this one. $7.50 Name ." '" . Call . 33-WAVE PROPAGATION & ANTENNAS- We lch. Hig hly recommended by the propagation ellperts as the besl Book on the subject. $5.75 Address . 40-RADIO HANDBOOK, 15th EDITION-Orr (W6SAI). This is for and away the best amateur radio handbook ever printed. Over 800 pages_ $8 .50 Cily ...... Siale . 52-HOW TO READ SCHEMATIC DIAGRAMS-Marks. Components & diograms; electricol, electronic, cc, d e, audio, rf, TV. Storts with individual circu its ond carries Ihrough complete equipments. $3.50 RADIO BOOKSHOP 57-QUAD ANTENNAS- Orr (W6SAI). Theory, design, 1379 Easl 151h Sireel, Brooklyn 30, N. Y. construction and operation of cubical quads. Build-it yourself info. feed systems, tuning. $2 .85 (N.Y.C. add 3% lax) bO 73 MAGAZINE (TVI from page 59) 50,000 SOLD IN 6 MONTHS! LEKTRON EXCLUSIVE and don't argue. J ust give the neighbor the ad MONEY dress of the F CC and relax. After all, you JUMBO PAKS by the POUND ~~ ~ :'o " tee know your rig is clea n (you'd better!) and t he RADIO.T V PARTS -SOO t o 1.000 p es pe r poundl FCC is on your side _ .. so long as you are o ON E POU ND o ONE POUND only cutting up one or two TV sets in the Dil el &. Ceram its o 18e1. Cerllmies. WUIt"fll $7:"> Precilionl neighborhood and t he rest are not bother ed. $ ,,"OUTII no o ONE POU ND e , 0 ONE POU ND Rip 'em all up, and you'r-e in for t rouble with Prechion Ruiltorl P d Crr-mie C ond e n ~fI the F CC inspectors. ,,"UHTII SloO poun \H lItTIl $.~5 n ONE P OU N O ( ' lIp out o ONE POUND If the Councilman is a lawyer , he knows bet Di le 'Cnndenlerl & mall Tub ular Condenurl ter than to try to step into an a rea that be \\"011"1"11 $!';O \\" 011 '1'11 $1l5 longs to the Federal Government .._ the BUY 4 PAKS & PICK THE 51h FREE regulation of radio activities is constitutionally Free ::::":."; ' \ , ~i "~\'''~ ' . :~~',~~; in the hands of U ncle Sam. So relax. E ven if cotolo g 1"'''U l:e ; ..X'~I returned. W r iteI C.O. I). <> nlera, 2.;% <.Io"n; t he local legal beagle politician does make big LEKTRON ratt·,l. Iltt :10 APRIL 1961 61 --- ...... • • KEEP CANDEE HANDEEI FAM OUS Q :I'ER ! I I Advertisers Index Thll II the tantabuloUi one l 190-550 Ilo_ The r .. relr or J'ou've been look lnll: for . t only •• •• •• .••• •. •. 59.9:1 BC·..:I": 3-6 )Ie•... ..•.•..•....•.•• .•••. .• • •• .•••• 7.11:1 Alden ...... 45 BC·U5: 6 -9 ,1 )I ~ ...... •....•••. .• ... •••• 7.95 MD _7 MOD ULATOR : SPfilal 3.95 Alltronics-Howard 63 Arrow Electronics, Inc. 64 A TRIO OF HEADSET BARGAINSI HS -23 : H I Imuedan re. Leather covered h e . ~ ba n d . Barker & W il liamson 5 1 Bnml new. Orea t buj-. Only ...... ••. .••.. .. 54 .115 HS -33 : 1.0\1' Impedarxe. I.,'ather rOI'eret! he'd- Barry .... 53 hand. Urand new. A. J. J . (' andee !'ll'l'clal .. ... :1.9:1 HI F I H ~ . :I s o t : 1:1.000 nclu! Brand new II lth Call-D -Cal 63 ehamol. rll' hl"n~. II', t..n lllel Ouly ...... •• . 8.9:1 CD- 3 ~7 A Headset Ellten, lon Cllrd : Brand new. Candee 62 ~Illlrn " !ma leiy :I fl . len ~lh , flnlr . . .49 Centimeg 49 AP N· I FM TRANSC E IVE R Central Electronics I 4.~0 ·450 U r . Comlll. ,,'Ith tunes. xse. ~: a . .•....•... $2.95 Apl'rn:r . ~ h p. wt. l'n unit 2:; 1111 . _ TWO for 5.00 C lark 43 Clegg . .. 2 YOU GOT III WE WANT IT! LET'S DEAL? we're paying top sn tor uuc-e. i-nc-e . -8 , · 9. ·10; Columbia 47 ON -"IIA : All e t.."trflfllc test e'luil'. Cush craft 45 R .4A/ARR · 2 REC EIV ER Editors & Eng ineers 4 1 23j - 2 .j~ lIe. : 1 tunes. (;Il~" . lunallie renlHr. ~ ee EICO 8 Au.../511 C.Q. M,., lIne for eomertlon. EJit"f! lt ent eend, : TW O tor 55.00. ~: , e h $2. 11 5 E-Z Way Towers ...... 6 ; Fa ir Radio ...... 57 1-208 F M S IG NAL GENERATOR I·"rl''!. ra nges : U I- 4.5 xrc. and 19-45 xrc. I<'r c'!uem':t' Globe Ind ustries .. . .. 49 In six attractive, permanent dlrections 1::::~~~~ ~~~~~~~'=:~ Price for either design $ 1.95 colors with simple ~ for applying. Unequaled in1 each. Add 4% tax in Calif . Approx. size 3 ~4 - x9··. Ma iled appur.ance. Ideal gift. For cln, doors, equip., boats, P.P . within 7 days. No COO 's pltnes, etc. Beautiful design please. Enclos e ch eck or M.O. Designate wor ld design of world available In place '=='::i~~~ A~ k of state for Canadian and e if desired. for quote on re produci ng yo ur club insignia. DX Amattv,.. APRIL 1961 63 • at ZIMCO 2 & 6 METER THEFT ALARM CONVERTERS 'p n trtt ya ur r, lIi, lur Cnu.•' Conlrollt4 In cars, hats and trucks , Odn : over 30 db ... ~,.....""",,~ witll l imeo's blrre'" . Nolle F llure : better than 4 db " proof siren alarm, Unit ~J m pe r Tube Lineup ' l! meter Convnter h.. new, ImDOrted 6ES8 b1lh cOlsisls of pra ot siru and " tell inr relay, key...perated lain, low Mite. t11lcode tIL RF Amp ., 6t'8A 2nd RF Amp. ... 'I/Iff I sW ltell 3D d Ii pIsll httlll alarm swi tclles. See aST )1I11: e1'. 6J6 Oac.-}lultlplln. Ja., 'st. Ul e 27. 6 met er Com m er h.. 6 B!i!l ('ncode RF Amp and et 'SA lUlu and Ol e. Compl ete kit, 12 WDe 5995 6 mater :2 mat., Converter cemprete with tu bn and It,l 6, 24, 32 VOC & 115 VAC mollels for 1·11 or 14- 18 me. U' Qutput I n CB·I 'nilable on ~Ie ci l l arder. Kit fo rm with !nltru e:t IOfIl ' I !U~ W ired and tested 127.50 PRECISION PLANETARY-VERNIER for exceptionally fine tuning Superb craftsmanship by Jackson Bros. 24 HOUR CLOCK of Enlland. Ball bearinl dr ive, V4" 24 hr. chrom. plated I " dla. shaft, 1Va" lonl, 8:1 ratio, metal wall clod. Inner dial ., Y ra for fine tuning. Eas U, adapt· with south polar projection able to . ny sh.ft. Comparable map of world IndIcates time ~::~~.:":": Iround world. Polar proJec· .. - Amat$5.95.eur Nel $1.50 ea. tion dial adjustable for warl· ous time lanes. Shp,. wt. Show n 10 for $13050 2 Ibs. approximatelyactual Amateur nel 58.47 tax inc• • 50 cycle model. .•• • ••• . . ..9.95 AMER ICAN CElOSO PI TUN IN; COILS Units la" • ,nit. Up switdl luuated II etralllic ceil ft,.. " Wonder Bar" 10 Meier Antenna Mod. 4/ 111 desiped ftr lSI win twl 'Ol's or 1141', (i, 'If As featured In No y. 1956 QST. Co mp lete with B & W ali el). FUIf . Rani' 3.5 to 21.1 ee: 3013 Miniductor. Onl)' 8 fl. long for 10 meters. Mod. 4/112 is dui,ned for us. Wt. 5lbs. wit!! sin,l' 101 or 8141. Handln Amaleur Net $7.85 0' tl SO w. RUII: 3.5 II 21.1 tnC . Mod . 4/111 If 4/ 112. tldl JUS Versatile MinIature Transformer Same .s used In W2EWL SSB R I~ - M.rch 1956 QST. Three selS of CT wlndlnls for • combination of Impedances: 600 ohms, 5200 ohms, 22000 ohms. (B, uslnl eenter taps the Impedances are Quartered.) ne Id eal transformer for a SSB transmmer. Oth er uses: lnterstale, transistor, hilh Impedance choke, line to grid or pl.te, etc. Size only 2" h. x '14" W. x '14" d. New and full y shielded. 3 for $3.49 Amaleur Nel $1.39 10 for $10.7S AR ROWAuthorized dlstribulD r of HEATH KIT equipment TO SAVE C.O.D . CHARGES. PLEASE INCLUDE SUFFICiENT Pl1STAGE WITH YOUR ORDER . ANY EXTn MONEY Will BE RETURNED. All PRICES ' .O.B. N. Y. C. Arrow's Export Dept. ShlDs To All Parts Of n. World! Prices Subject To Change Without Notice. IS THE CHEAPEST THING YOU BUY! There is a deep, understandable set isfaction in owning something truly fine. It can't be exactly measured in dollars or in words. Maybe it boils down to this: A good thing is worth a hundred times its price: a poor thing isn't worth having around. It's this way with Crystals. When you buy PRs you know you're gelling many times your money's worth. You're buying the finest precision frequency control that modern science has made .. . you g e t (in super-abun dance) the things you want most ... dependability, accuracy, long life, freedom from drift, unfailing activity. Yes-you can be proud to own PRs • , • everybody is! FUNDAM ENTAL, PR TYPE Z-2- Frequency Ra nges in Kcs.: 3,500 t o 4,000 (80Mt; 7,000 to 7,425 C40M I; 8,000 to 8,222 12M) ; 8,3H to 9,000 (6M). + 500 Cycles ·······-S2 95 Net (All Z -2 Crystah calibrated with a load copaci ty of 31 mmfd. l 6 Meters, Fifth Overtone, PR Type Third Overtone, PR Type Z-9A, Z-9A, 50 to 54 Me ., -+ 15 Kc. 24,000 to 24,666 ood 25,000 to S6.95 Net 27,000 Kc ., + 3 Kc S4.95 Net Cltleens Band, PR Type Z · 9R, .005% S2.95 Net EXPORT SALES: Royal Natio n al Corporalio n. 2; 0 \V. 57th Strut. New York 19 . N. Y•• U. S. A. . -jlh built-in PRODUCT DETECTOR THE "COSMIC BLUE" NATIONAL'S NEW HAMBAND RECEIVER This newest and finest precision double conversion amateur receiver with 6 meier coverage. brings you an ease of sideband luning previously available only in the most expensive equipment. The NC·270 features an exclusive "Ferrite Filter" for instant upper-lower SSB selection and a degree of selectivity to conquer even the toughest AM and CW signal conditions. The solid yg" steel panel, ceramic coil forms, double-spaced tuning gang, and full ventilation cabinet combine to give mechanical and thermal slability that will surprise even the most critical operator. Even the color of the NC-270 is outstandingly different, ational's new duo-tone "Cosmic Blue:' Write for detailed specifications. Only *24.99 down* Suggested cash price: $249.95. NTS.J Malchinl Speaker. $19.95 tsli&htly higher west or the Rockies and outside the U.S.A.). "Mcst National distributors offer budget terms and trade-in allowances. NATIONAL RADIO COMPANY, INC. AWMOU.Y OWNlD sa.SIDI....' OF U TIONll CD•• lilt. MELROSE 76. MASS. A,J NmbwJ RDdio', pDt. tlfu tl "Flip Foo," pUllen Export: AD AURIEMA. INC.. 85 Broad 51.. New York. N. Y. (Jpr~DlI1l6 lA, /'o'C-l10 '1>'(11'. Canada: CANADIAN MARCONI CO.• 830 Bayview Ave., Toronto 17, Onto