I don't know much antenna theory, ask me something regarding human
biology & I might be a better authority.
However, back when I lived in IL in the early 90's, I used to have a
tower and not enough space to put a good radial field down. What I
did to get on 160 was make a shortened delta loop with the apex at
the top of the tower and center fed at the base, held off the tower
by around 7-12".
I had a relatively small, and inexpensive vacuum variable at the
feedpoint at the bottom and ran a wire up the tower held off by
spacers from that feedpoint till the capacitance was sufficient that
at the least capacitance from the VV, I was 1:1 at 1.800.
I had a servo attached to the VV and enclosed everything in a plastic
mailbox and mounted that at the tower. I had the matching servo in
the shack and was able to adjust that small VV to give me 1:1 across
the entire 160 meter band. I believe the VV was a 5KV 300pf variety.
This may not be what you need to do with your setup but it allowed me
to use a cheap VV and surplus servos to give me a perfect feedpoint
match and I had no issues with my old 77SX with this setup. And when
running QRP I had fantastic results. Wish my current Inv-L with 60
130' radials worked nearly as well.
Gary
KA1J
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Topband Reflector
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