Now that it is summer, I need to make some improvements to my station on
the low bands - particularly 160m and 80m.
Right now, I've got a 15m tower with an A3S on top. I have a shunt feed
made of two #14 wires spaced 10" apart that goes from the base to the 12m
level at a spacing of roughly 5". I have 13 60 foot (.22 wl on 80m)
radials installed, and feed it with an omega match on 80m.
So far, the shunt works, although not noticably different than my low 80m
doublet at 10m. I plan to add 12 more radials, but I don't know if that
will improve the antenna that much.
For 160m I've considered putting up an inverted L, which I can run to the
12m level and then down into the front yard. The advantage is that I can
share the radial field of the shunt. The inverted L would run on the
opposite side of the tower from the shunt, but would be only 1/2m from
the tower.
I'm worried that the 160m inverted L may seriously detune the 80m shunt.
Another idea is to put a 1/4 wave sloper at the 12m level. I already have
a 40m 1/4 wave sloper at the 11m level.
Another ham had suggested I just put in a matching network to run the
shunt feed on 160m. I've experimented with a few different capacitor
values in the omega match, but I haven't been able to achieve at matched
condition.
One limitation I have is that the tower is the highest support on my
property, so just about any antenna has to be mounted to the tower, or be
substantially lower.
Anyone had any good advise, suggestions? Will the Inverted L work, should
I try a sloper, or how to I figure the matching network for the shunt?
Bill Coleman, AA4LR, PP-ASEL Mail: aa4lr@arrl.net
Quote: "Not within a thousand years will man ever fly!"
-- Wilbur Wright, 1901
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