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!



--
Email sent to is never read, unless it is in
response to an issue that interests me.

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!



--
Email sent to is never read, unless it is in
response to an issue that interests me.

On Tue, 11 Nov 2003 17:07:22 -0500, "Doug Dotson"
wrote:

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!



--
Email sent to is never read, unless it is in
response to an issue that interests me.


Doug,

Please keep us (myself and other 502 owners) apprized of what you find
out. I purchased the 502 with the thought that it was one of the best
VHF radios on the market.

Before my install I replaced the entire coax run, as well as a new
antenna. I did have one incident were there was some reported
break-up. I have yet to have the set up checked with a meter. I'll
have to wait until next spring as I am out of the water for the
winter.

Thanks,

John P
You helped me pick Amplepower for my charging needs.

On Tue, 11 Nov 2003 17:07:22 -0500, "Doug Dotson"
wrote:

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.

I saw a report on a mailing list that the 502 (or 602?) must be turned
off when attaching the remote mike. Have you found this to be true,
and what happens if you do attach the remote mike with the radio
turned on?


--
Peter Bennett, VE7CEI
new newsgroup users info : http://vancouver-webpages.com/nnq
GPS and NMEA info: http://vancouver-webpages.com/peter
Vancouver Power Squadron: http://vancouver.powersquadron.ca

Same problem with the 402. Remote mic doesn't work if you attach it with the
radio turned on. Usually cycling the power fixes it for the 402. I think the
audio quality is actually pretty good; works well outdoors.
Peter Bennett wrote:

On Tue, 11 Nov 2003 17:07:22 -0500, "Doug Dotson"
wrote:

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.

I saw a report on a mailing list that the 502 (or 602?) must be turned
off when attaching the remote mike. Have you found this to be true,
and what happens if you do attach the remote mike with the radio
turned on?

On Tue, 11 Nov 2003 17:31:33 -0800, Peter Bennett
wrote:

On Tue, 11 Nov 2003 17:07:22 -0500, "Doug Dotson"
wrote:

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.

I saw a report on a mailing list that the 502 (or 602?) must be turned
off when attaching the remote mike. Have you found this to be true,
and what happens if you do attach the remote mike with the radio
turned on?

We have the Commander mic on an Icom M602 aboard Lionheart. Plugging
the mic in while the radio is on doesn't hurt anything, but the remote
mic doesn't control the radio because the radio's computer only tests
to see if it's hooked up when it boots from off so ignores its pleas
for commands.

Hook the remote mic up FIRST, then turn the radio on. If the radio is
already on, turn it off, hook up the remote mic, then turn the radio
back on.

Damned stupid computers, anyways.....(c;



Larry W4CSC

"Very funny, Scotty! Now, BEAM ME MY CLOTHES! KIRK OUT!"