Posted by
Vic K2VCO on
Dec 08, 2005; 1:15am
URL: http://elecraft.85.s1.nabble.com/Clever-antenna-tuning-ideas-wanted-tp384403p384411.html
Darwin, Keith wrote:
> My antenna is similar. 28.5' tall, ground mounted over twelve 28' long
> radials. Fed with 30 feet of RG-213. With a tuner the system works
> well enough on 40, 30, 20, 15. 80 Meters is the pits. Dummy Load City!
>
> I'm considering putting a remote ATU at the base of the antenna.
> Basically, eliminating the 30 feet of coax feed line and all the high
> VSWR losses it entails.
I thought of this. A tuner would help by reducing the coax loss, as you
say, but at 80 meters the radiation resistance of the radiator is very
low, and so it's necessary to improve the ground system -- either by
making it more extensive, of resonant length, or loading it to
resonance. Since the effective ground resistance is in series with the
radiation resistance, the efficiency suffers when the ground or
counterpoise system is poor. Also, the usual autotuner is not very
efficient when loading a short whip -- that's why the mobile guys use
big bugcatchers.
--
73,
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco_______________________________________________
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