G’day
One way to get around the problem Frank W3LPL outlines below is to have one
general/TX 160m antenna that you switch between vertical and horizontal
polarisation.
If you can get up an inverted-V or flat-top dipole at 60 to 120 feet and feed
it with open wire that runs away from the antenna feedpoint vertically, the
feeders can be switched at ground level (using a double pole vacuum relay or
similar) so they are shorted and fed against a counterpoise/ground system, with
a separate coax feeder/matching unit.
For many years an east coast VK friend used this system, where he had a
‘shallow’ inverted vee 160m doublet about 90 feet high and took the open wire
feed to ground. The inverted vee made a great capacity hat to the shorted open
wire feeder/vertical radiator and I think he used to tune this against his
ground system using an L-network or a series capacitor
I also recall KK4TR – and several others – successfully using similar antennas.
Vy 73
Steve, VK6VZ
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Corollary: You can't have too many antennas except when they
interfere with each other which they often do on Topband where
a wavelength is approximately 500 feet...
Even on 20 meters, the pattern of a Yagi is noticeably degraded
when it points through another 20 meter Yagi or tribander 500 feet
distant or more.
Fortunately most Topband receiving antennas don't interfere with
each other -- except at extremely close spacing -- because their
mutual impedance is negligible. But transmitting antennas and
other antenna-like radiators such as power lines -- even 1000 feet
away or more -- can significantly degrade the directivity of
Topband receiving antennas.
73
Frank
W3LPL
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