[Kenwood] HELP-Ken mc-60

Sat Apr 9 17:25:58 EDT 2005

...you can do either of 2 things to kill that kind of RF feedback:
1) improve ground between the mike and the rig , so that RF from the antenna
will go to GND instead of going through the mike. You might go so far as to
replace the mike cord with a shielded one.
2) use what was an of course inclusion in old military equipment: 220 uH
chokes in series with every lead from the mike to the radio, INCLUDING one
for ground. There were 1 nF capacitors connected from both ends of the choke
to ground, the ones on the mike side to the mike ground and the ones on the
radio side to the radio ground. This setup killed every possible signal path
between the two and removed all possibilities of RF feeding into the low
level stages of the radio. It was standard in high powered radios made for
the American Army, like the GRC_106 family. In that case the small board
carrying the components was installed inside the transceiver case close to
the audio connector.
Alex	4Z5KS
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