Hi Paul,
I had trouble with the my Icom 746pro send relay when using the rig directly
with an amplifier or receive preamps, changeover tx/rx followers that use
relays for switching.
The send relay in the rig is a delicate reed relay. It seems to not handle the
make and break currents of driving the inductive load of a slave relay in an
attached device. I haven’t looked at the circuit of your rx antenna input
protector, but if it has a relay coil on it’s control input, that may be the
problem.
My send relay would stick permanently closed after a tx over, randomly. The
contacts seem to micro weld themselves closed in this situation. Giving it a
physical tap with a screwdriver would release the contact. I replaced the reed
relay and the same thing happened with the brand new one.
I cured the problem by building a fet relay switching circuit that drives the
amp etc control inputs from the rig send relay. The input current controlled by
the send relay is now only a few microamps and I have had no further problems.
A 2N2222 fet relay switching circuit, (switching 500mA max) is easy to build
and will isolate the send relay from the attached device’s higher input
switching currents.
I hope this helps you Paul.
73’s,
Ian VK2BJT
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UR RST IS ... ... ..9 QSB QSB - hw? BK
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