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wrapping ssb antenna on kevlar backstay
Oh boy..here we go...laughing.... see below....
On Sun, 13 Jun 2004 01:05:51 GMT, Bruce in Alaska wrote: In article , "Steve (another one)" wrote: Dear all May I pick-up on something mentioned in response to my earlier question. It was suggested that running a wire up a kevlar backstay is a simple soultion and avoids having to insulate a piece of conventional rigging. This sounds very sensible to me and plan to try it, it avoids having to mess with exposed connections to a wire backstay. However then Bruce in alaska said: Then just helical wrap the antenna wire around the Kevlar Backstay and have a really nice "Fully Loaded Antenna with alot of electrical length...... Could someone (Bruce perhaps?) explain this. Would I gain performance by simply wrapping the wire ? Is no of turns per length of backstay critical ? Is 'core' diameter critical ? Thanks Steve Gary has a valid point in that a tightly wound helical wire will tend to trap out the higher frequencies in the HF range. One thing to remeber however, is that if the band is open it doesn't take as efficent of antenna to communicate on these Higher Frequencies, and if the band is closed, no amount of antenna tuning or fooling around is going to allow communications. Where as on MF Frequencies, one needs all the length one can get for an efficent antenna, and the band is what it is, and really doesn't change much as far as open or closed, except for Day and Night. Better distances at night than during the day. A good compromise would seem to be a resonate 1/4 Wave at say 3200 Khz would allow for far efficency at 2182 Khz, by wrapping the helical windings tighter at the top of the antenna, give a reasonable length of wire on the lower part to resonate with the tuner at 12 Mhz, 16 Mhz, and 22 Mhz. Bruce in alaska Bruce has an excellent point re the windings...but I see a problem. Given a kelvar backstay length, how would one compute the pitch of the wrap? A turn every 6 inches for the first 2/3rds? Then every 2-3 inches for the remainder? Ouiji board? This topic is so interesting to me that short of buying a network analyzer, (I'll be honest, I can't afford one), I'm determined to figure out what simple test equipment I can use to evaluate various configurations, and then test them. Any ideas? Norm B |
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wrapping ssb antenna on kevlar backstay
In article ,
engsol wrote: Oh boy..here we go...laughing.... see below.... snipped for brevity Bruce has an excellent point re the windings...but I see a problem. Given a kelvar backstay length, how would one compute the pitch of the wrap? A turn every 6 inches for the first 2/3rds? Then every 2-3 inches for the remainder? Ouiji board? This topic is so interesting to me that short of buying a network analyzer, (I'll be honest, I can't afford one), I'm determined to figure out what simple test equipment I can use to evaluate various configurations, and then test them. Any ideas? Norm B Actually most of the work in this area was done by Ed Zanbergen, while he was Principal Partner and Chief Engineer of MORAD Electronics in Seattle, Wa. MORAD antennas are the defacto standard for commercial vessels in the North Pacific. They build some of the most rugged and effective antennas in the Marine Mobile Radio Service. Ed is long since gone to the Great Radioroom in the Sky, but his legacy is still around and being produced by MORAD today. When I was a beginner in this bizz, I worked for Northern Radio Co. which had a shop next door to Morad, and Ed and I became very good friends. I still have some custom antennas that he built for me, specifically for MF/HF Coast Station installations in alaska. I don't know if any of his notes were ever published, but he spent 40 years designing antennas in these Radio Services. One of the better designs that Ed built for me was a pair of matched Helically Loaded Whips that were resonate at 3300Khz. I mounted them at 60 Ft in a Dipole configuration, with PhosBronze feedwire, connected at the end of the 15 Ft Base tubes. Then feeding down to an Experimental SEA 1612B Autotuner that has twin tuning boards driven by a single CPU/ Sensor System, so that both dipole legs are effectivly tuned by the autotuner. This antenna can be heard, evey summer on the Marine Freqs as KWO-70/WDT-59 and operations on all Marine Bands from 2003Khz to 25 Mhz. Bruce in alaska -- add a 2 before @ |
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