I'd like to thank everyone for their suggestions on how to make my 32'
vertical with 8' elevated loaded radials perform on 80 and 30 meters as
well as 40.
It's clear I will have to do some major surgery on the antenna to add 80
meters, such as a trap plus a toploading wire, or a movable wire (N6WG).
Otherwise, the high reactance and low radiation resistance at the base
will remain a problem. AB9CA pointed out that a tuner at the base could
efficiently handle a low resistance if the reactance were tuned out by
some top-loading.
For 30 meters there seem to be some elegant solutions. W3FPR mentioned
that two symmetrical radials are enough, and EZNEC agrees that the
difference in overall gain between two and four is less than 0.1 db!
One approach would be to separate the two pairs of radials and feed them
each through an appropriate inductance (about 11.5 uh on 40 and 1.7 uh
on 30). This would resonate the system on both 40 and 30 meters. I also
noticed (thanks, EZNEC) that with all four radials connected together,
all I would have to do is short out the existing 40 meter inductance to
obtain a low SWR on 30! But that would require a switch or relay which
I want to avoid.
--
73,
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco
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