Ken,
There is a secondary problem.
Even if you don't damage parts, many radios do not have enough antenna port
isolation and the receive antenna will couple back into the low level
transmitter stages and add spurs and garbage to your TX signal.
My ICOM 751A's oscillated out of band when connected to Beverages, I only
knew it because I was watching on a spectrum analyzer. A friend had the
same problem with a Ten-Tec, but his spurs were in band.
Two important things to do are:
1.) Shut off QSK when working wide splits, the VCOs will generally unlock
and click more than normal QSK clicks.
2.) Totally disconnect external RX antennas when transmitting.
I use a pair of long carrier lifetime PIN diodes that short the antenna to
ground on TX as well as opening the lead, switched by a PNP transistor with
the base following the amplifier control line. Relays work also, if you
don't mind the clicks but they are generally slower than vacuum relays or
diode PA switches.
Long before the amp comes on, the PIN diodes are doing their thing. Also
put a bulb in series with the antenna (12 volt 100 mA) and a pair of back
to back diodes across the RX input line no matter what switching you use,
just as a safety in case the protection breaks!
73 Tom
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