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73 Magazine Staff Field Strength for Free - a home-brew conversion Pro bably many amateurs have ol d VOM s th at have out lived their usefulness or have been replac ed by better test eq uipment. In our ca se, a ten-year -ol d Japan ese YOM was start ing to develop all sorts of problems- a switch that was acti vated w hen t he pin tip from a test lead was inserted in the Oh ms jack made erratic contact; resulting in fa lse resistance readings, jacks on various other functions were worn out, and two current ranges we re bu rned out. The YOM had a goo d meter movement and case, however, so rather than sim ply di scard it, we turned it into a very handy and sensitive fi eldstrength meter. Undou btedly, the same can be done w it h many other VOMs at minimum or no cost using ju nk-b ox parts. O ne can end up w it h quite an attracti ve looking instrum ent, as good as the one shown in th e pho tograph of t he front of t he co nvert ed YOM. In the case of t his YOM, there was a series of pin jacks running vertically on bo th sides and along the bo ttom of t he space bel ow t he meter. Th ese w ere cov ered up wi th a pie ce of Lexan (the bl ack, wrinklefinish material seen in the photograph) and the pin jack hol es used w it h 6-32 hardware to hold the material in pl ace. Of co urse, any sort of att ractive plastic or meta l can be used as a covering plate. The miniature on/off switch for the a m p lif ier c irc ui t i ncorporated in th e fi eld-strength meter isshown in the center of the plate. You can also ju st di scern (on the right side) the knob for a sensitivity control. "The instrument's meter originally had die usual YO M scales. However, the scales we re on a plate which could be unscrewed and turned around to reveal a black surfa ce. This surface was painted gray and the numbers shown w ere placed on it using a rub-on lettering/numbe ring transfe r sheet. The method of dressing up an old YOM w ill var y w ith t he instru ment invo lved, but with a bi t of im agination o ne usually can find a method that w ill resul t in a newlooking instrument rat her than one which is a reminder of a discarded YOM. The YO M had a 250-I'A movement, so it was al- I "IJ 'I om '" '-l1--4 ""'0. on S IMILAR 0 -1-" Photo A. The front o f the YOM as it originall y appeared. It st ill lo ok s good, but electrically it was falling apart. Fig. 1. Broadband vo ltage-do ubler/rectifier and de am p li fier used in the converted YO M. 82 73 Magazine · October, 1980
ALPHA 76A Two 8874 Tubes 1.5 KVA Heavy Duty Transformer 2.5 K.W. PEP, 1 K.W. CCS Average Efficiency better t han 60% ALPHA 374 Wit h " No Tune Up" convenience Instant aneous band switching 2+KW. PEP Two 8874 Tu bes 1000 watt DC "No Time Li mit" Power Supp ly A LPHA 78 T he new Alpha 78 combi nes the best feat ures of all previous A LPHA's : More qu iet bru t power than the or iginal A lp ha 77··· A new " no t une up" system even better than t he 374A ..· and t he same superb OSK system used in t he A lp ha 77DX. A NTENNAS HY·GAIN R...... Sptci.l THfOx :o: 5YP
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Ii Gift to , enty Years of 73 o 174
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Rack Attack from DenTron Components
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Escape from Mt. St. Hel e ns! .....
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Small wonder. TRIO-KENWOOD COMMUNIC
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Afresh idea! Our new cro p of to ne
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All new, all nine hf bands and only
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1. SENSITIVITY: Superb amp lif ier
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Touch-Tone Decoders . SJ.' ·_ M·
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WHEN OUR CUSTOMERSTALK•.• WE LI
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STOP RF SPILLOVEI You may be losing
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( LEAKY LINES Dave Mann K2AGZ 3 Dan
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73's ICOM IC·720 DEAR OM: There ar
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MEMORY KEYER BREAK THROUGHI New l
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INTIMIDATED BY MORSECODE? THE NEWAE
Page 31 and 32: Solid-State H.F. Kilowatt Amplifier
Page 34 and 35: Escape from Mt. St. Helens! M arian
Page 36 and 37: dwarfed everything by its magnitu d
Page 38 and 39: Edward t. M ulvin WBQI FF 34()()54t
Page 40 and 41: Phot o E. The AB C " That's Incredi
Page 42 and 43: W erner M . Ma urer W1QMS Kefl y Dr
Page 44 and 45: MEMORY KEYER BREAKTHROUGHI The rema
Page 46 and 47: -WILSON SYSTEMS, INC.---.... the SY
Page 48 and 49: WILSON SYSTEMS TOWERS !i ~ ' ''0.0
Page 50 and 51: Joseph D. Novak K40VK 2420 Luckett
Page 52 and 53: Antenna azimuth for ATS·3 from Was
Page 54 and 55: ---SCR1000VHF-SCR4000UHF---- 7i?
Page 56 and 57: Joe wesrennaver W4FE:. C 155 Wood f
Page 58 and 59: f MEMORY KEYER BREAKTHROUGHl The re
Page 60 and 61: The Arcane Art of ATV the transvert
Page 62 and 63: Th e 2N2219 t ra nsistor specif ied
Page 64 and 65: Photo E. l eff WB8 RIY, about 5 mil
Page 66 and 67: Pho to G. Rack-mount installat io n
Page 68 and 69: Robert B. Grove WA 4 PYQ Grove Ente
Page 70 and 71: proveme nt over the origina l To uc
Page 72 and 73: channe l l ; ente r 139.1 MHz into
Page 74 and 75: detector. Be sure receiver is sw it
Page 76 and 77: Joseph H. Cowen WA 5TUM P.O. Box 76
Page 78 and 79: an advance piece and aft erthe-fac
Page 80 and 81: School and ret ired surgeon Dr. N i
Page 84 and 85: Photo B. Front of th e con verted Y
Page 86 and 87: TE1: ANTENNA SYSTEMS l-BoO-654 -}2}
Page 88 and 89: Robe rt M . Brown W9HBF 561 1 M idd
Page 90 and 91: c o u ra g i n g a n d wo r th repo
Page 92 and 93: elay (I used a 3PDT type) . When th
Page 94 and 95: '" '" 117 VAC NEON DIAL LITE .l 117
Page 96 and 97: Fig. 9. This view sho ws how the ra
Page 98 and 99: ~ ''' ' '' '' '' -- sli de the cap
Page 100 and 101: "' 0." -t ee' I CONNECTOR~ TO IlR M
Page 102 and 103: 1'::1" ~~4 ""ATTENTION MOBILE HAMS
Page 104 and 105: Patrick M cGuire W BSHGR 102 Dunca
Page 106 and 107: SECURE THIS END TO BOT TO M PL ATE
Page 108 and 109: Then buy a small can of red spray e
Page 110 and 111: Description a) Print frame (same as
Page 112 and 113: MEMORY KEYER BREAKTHROUGHI The rema
Page 114 and 115: INTIMIDATED BY MORSE CODE? THE NEW
Page 116: RTTY Demodulators ~~;~~ e $449. 00
Page 119 and 120: BUU Directlromthe Tri·EK@ Factoru
Page 121 and 122: • CALL 1 N8AD 2 KB8/>J'1 l WAlDCS
Page 123 and 124: • •• Computerize your log boo
Page 125 and 126: is sim p lif ied and refined t o al
Page 127 and 128: upts but often gets in the last wor
Page 129 and 130: signals. It decides tra nsm itter o
Page 131 and 132: .... Reader SelVice- see page 274 7
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IIEW IIIFFEIEIiT FROM BARKER & WILL
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Have you ever wondered why the best
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P ~ESCA l£ I NPUT C2 C1 I~ ;;-----
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A 40-pin socket must be used for th
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un til it changed tone and wo und d
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MF.J 941C Versa Tuner II , i i 11f!
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Two fuses are incl uded fo r safe t
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pu shed for th e switch to SSB and
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October 1960 .. .....de W2NSD PI ,a
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A M ATEUR RADIO 73 6' YIO carRad¥
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73 1964 January INCENTIVE LICENSING
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John W . CampbeJl W2ZCU How To Be A
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would simply melt the m selves in
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73 1966 Oc tober de W2NSD/l de W 2N
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162 73 Magazine . Oct ober, 1980 19
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1969 October ...de W2NSD/l rr ay ne
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1971 Decem ber Mean ingf ul Conu cu
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Jean Shepherd K20 RS Some Guys Make
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1973 July .......····n~ 73's HA
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1975 August 1: ~ '3~fr EOi TORJI'\.
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1978 August : :~~. Ir EOITOM'U8USHE
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1979 March ( UJoTOM'V 8USHEII W. ..
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manage o n 4o-mete r phone for the
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Fig. 3. Basic patte rn developed fr
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of-contac t are three: New England,
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32 ' I " 3 2 '" 3 2 ' . " 3 2 ' I "
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Gilding the Lily - FT-101 mod for c
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Mike Mods for the KDK-2016A - impro
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Clock Blocks a compendium of TTL an
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ea BOOK CIIlOS I"lV ERT ER "0001 "
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73 Magazine Staff Build a Better Ba
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TUfTS Electronic Department Store,.
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TUfTS Electronic Department Stor~"T
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TUfTS Electronic Department Stor~.T
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t.a IO,. H r "001 ,j- ± " ~ cs r u
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and 5. The purpose of the divide-by
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3500. To do this division by 3500,
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l i mi t er o utput on p i n twe lv
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Radio Amateurs! Tempo Handh
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79. Late in 1975, as the JARL looke
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QRP ARCI ANNUAL OCTOB ER QSO PARTY
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("----~) FUNl from page 28 5) The "
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you need a friend w ho works fo r M
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held, and the Georgia State CW Asso
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FREE! RADIO AMATEURS WORLD ATLAS wi
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DireCiional RF Wallmeler Dielectric
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control of an amateur radio station
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SatelliteT~ FORTHE HOME Sick of Net
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schematics, formulas, construction
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Th e Comm issio n s tated , " Lo ok
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MFJ RECEIVER ANTENNA TUNER/PREAMPLI
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c lasses are proving that it is pos
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74l SIllITTL IUSooN l4lS0 2N " l50'
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NO BULL SHi", • Over the past thi
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7294 N .W. 54 STREET MIAMi. FLORIDA
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• linear Converters for SS B, CW,
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L.. ....J ...... 28 22 North 32nd S
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ATTENTION IC·2AOWNERS: IC-2ATONE D
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smsat !!!ill. CP'O -.4,,...a_ " N '
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BLAK-RAY Ultraviolet Intensity Mete
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PROUDLY PRESENTS the GLOBAL SPECIAL
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TOLL FREE # (800) 528·0180 (for or
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MICROWAVE COMPONENTS COMPUTER I.C.
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• NOV ICE STUDY GUIDE-SG7357-Here
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= = === = TEST E QUIPMENT =====:::;
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EALER PROPAGATION San Jose CA Bay a
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