The switchbox is a homemade relay box located at the base of the vertical
about 100 feet from my shack. One relay adds in a loading coil at the
base of the 60' vertical antenna for 160 meters. When the shack switch
is turned off, the loading coil is disconnected and the antenna is then
tuned for 80 meters - the default position. I don't need to detune on 80
since the re-radiated noise on that band is minimal. Another relay can
add/subtract additional inductance to move the resonant point around
somewhat on 160 and from 80 to 75.
I built an "on/off" switch on my desk powered by a 12 v power supply that
controls the power to the relays at the base of the antenna.
I had planned to add another 12v relay which would just control the
voltage from the shack powers supply and it would be controlled by the
TVSU. The TVSU would be used to control a relay that would simply turn
the power from the shack supply to the desk on/off switch off and on. My
plan is to wire the new 12v relay so when I hit the key, the TVSU will
result (ultimately) in the relay at the base of the antenna controlling
the 160 meter loading coil being activated -adding loading coil so the
antenna would be resonant on 160 meters. When I release the key, the
loading coil would be disconnected and the antenna detuned (back to the
75/80 default position). The TVSU would make sure the timing is correct
The problem is the speed of the unknown relay types and how well they take
repeated cycling. Every relay might add anywhere from 2 to 30 mS of time
delay in switching response. This is especially true if something loads the
relay coil, like a low impedance or a diode, on relay release. Just adding a
diode across a relay coil can slow a relay's release time significantly.
I wasn't expecting a homebrew answer, so I still have no idea what type of
relay you have. I don't know relay speed and reliability. I guess the normal
mode is closed on transmit and open on receive.
73 Tom
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