wrote:
If cutting the vario when the mic is keyed is the objective, could the
PTT be wired to cause a relay to open the vario speaker circuit? Then
the technique could be used with any radio?

Sure! I'd suggest using a small DPDT ("double pole, double throw") relay
(check Radio Shack) behind the panel. One set of contacts would key the
radio; the other set of contacts would open the lead to the vario speaker.

The coil would be driven by the PTT switch. A 12 volt coil would work as
long as it closes with 10 volts or less, because you don't want the
radio to stop working just because you can't key it. If you are
concerned about this, you could mount a PTT switch on the panel that is
in parallel with the contacts to the radio, for use if the relay fails.
You might have to use a relay with a lower voltage coil and use a
resistor in series with it, or carefully adjust the metal tab holding
the contact spring.

A small diode should be placed across the coil to protect the PTT
contacts. Connect the diode so current does not flow through it when the
PTT is keyed; i.e., the band on the diode body should connect to the
positive side of the coil.

Undoubtedly, your club has a member that can assist you, if needed.

--
Change "netto" to "net" to email me directly

Eric Greenwell
Washington State
USA