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Old 05-04-2009, 09:35   #1
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Icom SSB Mod

How can I determine if my Icom M-802 has had the factory clipping modification performed on its transmitter?

Many thanks,
Rich
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Old 05-04-2009, 10:10   #2
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Suggest you contact icom directly as the modification was a running one and they can probably specify the serial # where it went into production. Ditto if you are purchasing the radio from someone else...ICOM can probably trace the serial # to see if it was modified. (BTW...I bought mine in early 2004 and had NO clipping problems). If your antenna system is good...even without the modification, you should have no problem.
The original 2007 bulletin from ICOM on this is reproduced below. Certainly nothing produced before this date would have the modification. Contact them for assistance.
*******

IC-M802 Technical Notice
Updated 3/7/2007

These symptoms do NOT affect all M802’s; these symptoms only occur under certain installation conditions.

For a while now, we have received isolated reports of audio “clipping” during transmit regarding the M802. The exact symptom is when the operator speaks, on certain voice patterns, the receiving party may hear part of the word being cut out and then the transmission quickly comes back. The operator may hear a few more words and then the symptom would repeat. The occurrence of this may be random with some days, no problems at all and others, the problem would return.

When we received units that were reported to have these symptoms here at Icom, we could not reproduce. In September, we received a recording of this taking place and decided the best way to proceed was to visit a customer’s vessel that was reporting these symptoms. In November we were able to do just that and were able to reproduce the reported symptoms.

Currently, we are testing a proposed modification and if our tests go well, we should be rolling out a factory approved modification shortly.

If you are experiencing this particular symptom, we should be able to let you know shortly how you may resolve it.

Please be aware. If you are experiencing any other kind of symptom than the one exactly as described above, pending resolutions will probably not resolve it and you should seek assistance with a qualified marine electronics dealer.

Update
Icom has been studying the isolated reports we have received regarding “audio clipping” during transmit on the M802.

The exact symptom is when the operator speaks, with certain voice patterns, the receiving party may hear part of the word being cut out and then the transmission quickly comes back. The operator may hear a few more words and then the symptom would repeat.

It was discovered that this situation occurred upon voice peaks that were transmitting into unanticipated SWR situations.

When the radio sees these voice peaks into high SWR conditions, it tries to quickly reduce power to avoid damage to the transmitter. Then it brings power quickly back up to make sure as much power as possible is being transmitted from the radio.

This causes the “clipped” condition.

Many vessels have SWR on the bands they use much lower than this so this is never a problem. Some vessels do have antenna systems that are problematic and do have SWR’s that are high enough to cause the radio to attempt to start protecting itself.

The best way to quickly eliminate this issue is to have a qualified marine electronics dealer inspect your antenna and ground system to make sure that it is optimal.

In some cases, it may be very hard to get a better SWR. In this regard, Icom has discovered an improvement that will help the radio not “clip” in all but the most extreme SWR environments.

Please be aware that if you have additional problems after installing this improvement, you will need to improve your antenna system as minor “clipping” you may get is actually the radio trying to protect itself while still putting out as much power as possible!

As always, please ensure your antenna system is optimal. No transmitter is completely safe against catastrophic failure into a bad antenna system. Because this improvement allows more power into degraded antenna systems, you should take extra steps to make sure your antenna system has no worse than a SWR of 2.0 to 1 on the frequencies you transmit on. 1.5 to 1 or lower is preferred.

If you would like to have this improvement installed in your equipment contact Icom’s service department [service@icomamerica.com] or 425-454-7619 for further information.
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Old 06-04-2009, 10:02   #3
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Or you can look inside. With cover off, look down on the main board at the back center just in front of J1901 you'll see three surface mount capacitors in a row. If you see a surface mount resistor soldered on edge on the leftmost capacitor, then you have the mod. Better to look with magnifying glass.

Eric
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