I have had similar problems with mine. I'm assuming it is the antenna or
coax first since they are pretty old and need to be replaced anyway. Once
that is done, if it is still acting up then I am going to replace it. I did
notice
that if I transmit for a long time, the transistors in the final amp go into
thermal runnaway. The heatsink on the back gets too hot to touch and does
not get cooler even if I unkey the mike. Transmit power drops off sharply
at that point. I have to turn the unit off to allow it to cool and then turn
it
back on. The remote mike does not have good quality audio output in
any case. Receive sensitivity of the 502 seems pretty bad as well but then
again it could be my antenna. Before next season I'll put a meter on it
and check it out.

Doug

"Harry Krause" wrote in message
...
I have an ICOM VHF, model IC-M502, new this past spring, and two
weekends ago, I noticed it was not transmitting properly.

I was "rafting up" with a friend in his boat, and while we were
negotiating the boat hookup, I tried to stay in touch with the VHF. He
could not hear anything at all when I transmitted at the one watt
setting, but could hear me with some signal breakup at the 25 watt
setting. We tried several channels; same results.

It's not the antenna or its fitting, as far as we can tell, because we
hooked up a spare VHF and it did fine.

The friend believes there may be some problem in the M502's mike. My VHF
radio electronics knowledge is minimal. I am going to send the radio
back to ICOM for a look-see and repairs, but I'd like a better
indication from the experts here as to what might be the problem.

Any ideas?

Thanks!



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