The most non-invasive method for this is to use an external
HF-RF-capable SPDT relay to switch to the regular antenna upon transmit.
You set it up 'failsafe' by having its N/C (power-off) position
connecting the 'regular' antenna to the transceiver. Easiest way to
avoid timing/sequencing problems with this is to connect the key (or
PTT) as the activator for this relay, and use a second set of contacts
to then key / PTT the transceiver. That way the relay is set BEFORE the
TX can put out RF. You can use a toggle switch somewhere to take this
'offline' (a N/O switch in series with the relay coil will do) for full
time main antenna use. Note I said this was the quick-and-dirty method.
I have a design for a somewhat more complicated unit that allows all
sorts of insertions of preamps and the like, as well as worries about
timing and mode and the like. But this will do the job for you just
fine.
--
72/73
Ed Tanton N4XY EMAIL: n4xy@avana.net TEL: (770)579-3933
Voice/MBX/FAX
189 Pioneer Trail, Marietta, GA 30068-3466
QRP-ARCI#7663 G-QRP#6779 OK-QRP#172 QRP-L#758 AdvRC#140 NORCAL#1779
NCDXF SEDXC
Life Member: ARRL AMSAT IDRA INDEXA QCWA URL:
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