> There appear to be at least two other solutions:
> 1. a transmission line stub, similar to the write ups for half squares and
> bobtail curtains.
A transmission line stub, other than providing matching, radiates.
We have the very same common-mode current problems we have
with open wire line right into the shack. We just satisfy the SWR
issues and make a single band antenna (at least for a fixed length
stub).
>2. A tank coil tuned to 160 meters at the feed point
> with a tap or link for 50 ohm coax to the radio and the top or a high tap
> for the high impedance antenna feed point. The tank coil approach is in
> figure 12-19 of ON4UN's 1994 edition of Low-Band DXing. Note the inverted
> ground plane is simply the middle part of a bobtail curtain, omitting the
> inverted L portions on either end.
That would solve matching and balance (common mode) problems,
assuming an isolated link is used and the antenna has a ground
system at the ground-level feedpoint. But again, it is a single band
system unless you switch networks outside.
What I used, when I had limited space, was a simple 100 foot long
dipole with balanced feeders down to the ground. I could feed the
antenna as a T on 160 and 80, or as a dipole on 80 on up. I had to
switch networks outside. Of course it needed a ground system, as
all verticals or antennas near earth do if you want high efficiency.
73, Tom W8JI
W8JI@contesting.com
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