U.S. Tower's remote control package for the raising/lowering motor uses
120VAC to drive the relays at the tower. The control box is nothing more
than a bunch of 120VAC switches and some 120VAC neon light bulbs. This means
that 120VAC control signals run between the shack and tower.
I discovered this *after* running the control cable for the tower in the
same conduit with all my low voltage control cables. I had taken great pains
to run a separate conduit for the tower AC and there was no more room in
that one. Even though the 120VAC isn't present unless the motor is being
activated, the situation really bothered me. It's also against local code to
run high and low voltage wires in the same conduit. Worse yet, 120VAC was
too high (by 40 volts) for the Polyphaser 8-wire rotor lightning suppressors
I had installed.
I ended up building a low voltage (12VDC) relay interface to drive the motor
relays. It took four 12VDC relays to duplicate the switch functions in the
control box and two 120VAC relays for the limit switches (they switch 12VDC
"full up" and "full down" signals running back to the shack.) I mounted the
relay board in a plastic waterproof box and stuck it in the metal relay
cabinet on the tower. I could have modified the U.S. Tower control box to
drive the board, but it was easier just to build a new one (it takes up a
lot less space, too.)
Now the AC stays in the cabinet at the tower where it belongs!
73, Dick, WC1M
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