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32 ' I " 3 2 '" 3 2 ' . " 3 2 ' I " Fig. 8. Close-up of coaxial 'T' int erconnections. Actual coax length from this point to the dipoles is 32 feet each way. This section is ele vated to a height mid-point between the heights of the two dipole centers. DI R E CTION 0 ' M 4 X IM U ,,", R,- \ " ~:7"'--+-+' I --"'---i.;=:;;;- 1 u' +, Fig. 9. W9 HBF installation, fooking sou th. (In reality, trees, no t poles, are used as supports.) Note that maximum ri di rection is almost opposite to tha t of the live d ip o le elem ents. viewed from the top look in g dow n tow a rd th e g ro u nd . Eq u al 3 2-f o o t lengths of RC-58 are used between the two dipo lety pe elements. This len gth was chosen not scienti fica l ly, but simply becau se it was the length req uired to reach between the tw o antennas whe n th ey we re or iginally space d when the array was cut for 75 meters. But many exper ts te ll me that this coax spacing may have a great deal to do with why this antenna performs so well. I leave it up to you to decide what will wo rk best overa ll. The 1 3 'h -foot offset dipole centers also may help to explain a great num ber of things about this ante nna, but I'm not sure just what at th is po int. I rathe r sus pe ct t hat you could experiment with this 186 73 Magazine . October, 1980 shift co nsiderably with interesting results. O verall , 200 fee t of RC-58 runs ba ck to t he operati ng po sition from the ante nna. I ofte n drive this with 2 kW in, and have yet to have a pro blem . The majority of the coax feeds ba ck to the ho use at the elevated point where the tw o coax dipole feeds break off-so it is a lso possi ble that the effect of the coax adds som ething to the ante nna itself. The coax runs t hro ug h high t ree bran che s m uc h as t he eleme nts do , Fig. 8 shows how the co axia l "T" is interconnected. I simply used black plastic elect rical tape; the connections at W 9H SF are not even so ldered toget her- just twisted. You may wa nt to experiment by reversing the cente r con- du ctor feeds to t he d ipo le elements, just to see th e effect it might have on your pattern. I use a string to hoist up the "T" point into a t re e so t hat t he co ax doesn't droop do wn into a p la y a rea w he re t he yo u ngs ters ofte n congregate . Fig. 9 shows th e installation from t he north, looking sout h. (poles, not trees, are shown here to simplify the d iag ram.) No te th at th e area of maximum radi ation (gain) is quite opposite to where the cente r cond uctors of t he coax feed . I have no w ay to expla in this phenomenon. CuttinglPrun ing I had to do no cutting/pruning whatever. The original 40-mete r cut, to 7.250 MHz, is the o nly cut made, and that was by way o f sta nda rd d ipo le fo r mulae. At W9HBF, du e to exte n sive antenna experimentation conducted with wire arrays , all fee d lines go into a switchbox and then into a DenT ron Monito r Tuner. As a resu lt, I've not had to be concerned over vswr problems, nor have I eve r had any with this antenn a. I can report, however, that th is ante nna mat ches very closel y to the settings u sed fo r t he d oubleex te nded zepp. In fa ct. t he re is o nly 1 .3:1 di f ference between the two . (In other wo rds , if t he transmatch is set for the ze pp, whic h uses a bala nced 30 0-0 h m l ine , switc hing in t he unbalanced coax feed of the array throu gh t he OenTron " coax"I"ba lanced" pa ne l sw itch prod uce s only a 1.3:1 swr on the array. As a result, only a very minor adjust me nt is required to bring the a rray to a pe rfec t 1:1.) This is qui te advantageous, since it simplifies the pr o blem of gett ing qu ick comparative antenna checks over the air. TVI is one fina l aspect of this ante nna that is worth mentioning. No TV! can be noted at a ll. This is not the case w it h t he do uble exte nded ze pp or th e roofmounted ground plane . This Array on Othe r Bands Results on other ba nds are interestin g. However, my comparison standard is a ve rtica l Hv-Cain 14AVQ o nly. However, here's what I get: .20 me ters: The vertica l is better, by 6 dB. .15 meters: The array is better, by 12 dB. .10 meters: The array is better, by 24 dB. Need less to say, this array sees a lot of 10-meter use at W9HI3F . Contacts into Europe and Asia are es pecially good, and my signal freq ue ntly beat s ou t a ll t he boys with big bea ms, as the OXstation invariably comes back to me first. Furt her, OX sta tion co nta cts te nd to be so lid and reliable (no Q5Bl, so half -ho ur-lon g rag chews on 10 meters with Europe are not uncommon. Since my vertical does not functio n be lo w 40 meters, I cannot use it as a comparison standard fo r 75 meters. But the doubleexte nded ze pp does wo rk well there. A comparison he re shows .that the zepp has it over this array by 18 dB. This is prob ab ly because the zepp a pproxim a te s a d ipo le a t 75 meters. However, the array does functi on on 75, which surprised me. Ov erall, though, the array seems to shine best on 10,1 5, and 40. But because of the lack of effec tive ga in-ante nna compe titio n at 7 MHz, it stands out more on th is band than perhaps anyw here else. I hope that others may experience equally satisfying results and thafthey will report refinem ent s that further improve effectiveness.•
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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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INTIMIDATED BY MORSECODE? THE NEWAE
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Escape from Mt. St. Helens! M arian
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Fig. 9. This view sho ws how the ra
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MEMORY KEYER BREAKTHROUGHI The rema
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Page 135 and 136: Have you ever wondered why the best
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Page 143 and 144: MF.J 941C Versa Tuner II , i i 11f!
Page 145 and 146: Two fuses are incl uded fo r safe t
Page 147 and 148: pu shed for th e switch to SSB and
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Page 152 and 153: A M ATEUR RADIO 73 6' YIO carRad¥
Page 154 and 155: 73 1964 January INCENTIVE LICENSING
Page 156 and 157: John W . CampbeJl W2ZCU How To Be A
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Page 160 and 161: 73 1966 Oc tober de W2NSD/l de W 2N
Page 162 and 163: 162 73 Magazine . Oct ober, 1980 19
Page 164 and 165: 1969 October ...de W2NSD/l rr ay ne
Page 166 and 167: 1971 Decem ber Mean ingf ul Conu cu
Page 168 and 169: Jean Shepherd K20 RS Some Guys Make
Page 170 and 171: 1973 July .......····n~ 73's HA
Page 172 and 173: 1975 August 1: ~ '3~fr EOi TORJI'\.
Page 174 and 175: ~ ~ >. :; ....., co t" O) , f "i'
Page 176 and 177: 1978 August : :~~. Ir EOITOM'U8USHE
Page 178 and 179: 1979 March ( UJoTOM'V 8USHEII W. ..
Page 180 and 181: manage o n 4o-mete r phone for the
Page 182 and 183: Fig. 3. Basic patte rn developed fr
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