Force12 does something similar with its rotatable dipole. Each side of the
dipole went to box and had 3 coils in series to the feed point. There were 3
DPDT relays. Each side of the relay would short out a coil on one side of
the dipole feed. One coil could shift the low SWR point 240 kHz, another
about 80 kHz, and the last one about 40 kHz (a bit hazy at this point). At
the input to the box there was a fixed coil across the input terminals and a
balun to coax. With 3 switches you could adjust the low SWR point to 8
different places on the band. By default, all coils were inline putting you
at the bottom of the band.
73, Larry W6NWS
-----Original Message-----
From: Richard Karlquist
Sent: Monday, October 21, 2013 1:17 PM
To: towertalk@contesting.com
Subject: Re: [TowerTalk] 80M Inverted V - CW and SSB
On 2013-10-21 02:50, Doug Scribner wrote:
I'd like to find a quick way to switch between the CW and Phone
portions of the band. I know I could just set it for SSB and then add
a short section to each leg for CW and that works for dedicated
contests but is a little inconvenient for everyday use.
On my inverted vee, I cut the wire to tune the antenna to the bottom
end of 80 meters. I have a box at the top of the tower with 3 relays
in it that switch in series capacitors in each leg. The series
capacitors
tune the antenna upward in frequency. There are 8 combinations
of relay positions that give me eight capacitance values covering
3.5 to 4 MHz with low SWR. The capacitors are a pair each of 470 pF,
1000 pF, and 2200 pF power mica. I also have a 40 meter inverted vee
at right angles to the 80 meter inverted vee. The feedpoints are
connected
in parallel to the capacitor box. The switched capacitors also
work on 40 meters to cover the whole 40M band with low SWR.
The advantage of this is that you get a really low SWR over the full
band.
Passive matching networks can only give you a mediocre match and only
over part of the band. Then you end up using a tuner in the shack
anyway.
Rick N6RK
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