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Old 22 May 2008, 13:05   #1
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Microphone or something else?

When I was out chasing fenders the other day I was trying to use the base set on the Destroyer (Icom IC-M402 into a Rib Raider antenna) the folks back in the office reported just being able to hear a loud hum rather like background engine noise when I was transmitting. I used the handheld to talk to our launch for the rest of the trip and that was fine so the prevailing conditions (a bit breezy and bloody rough) had nothing to do with it.

On further investigation the microphone seemed to have a bit of water in the diaphragm or at least a small amount of water came out the grille when I shook it and then banged it on my hand. I assume the mic is a waterproof item as the radio is supposed to be waterproof, but how susceptible are they to water ingress screwing up the audio? Having shaken out the mic, I was just talking to the office (from about a mile away parked at the house) and now it appears to work fine but I don't know if the problem could be that simple, or if there could be something else.

Would water inside a mic like that cause symptoms like that? I wondered if it might also have been interference from the engine but the receive is certainly fine when running and if you have alternator hum on my other VHF amateur sets, it normally comes through on receive as well. I can't really test it until next time I am out, if I run the engine on muffs whoever I am trying to talk to won't hear a damn thing anyway

Just wondering if anybody knew if this was a common problem - I would have thought the microphone grille would be designed to drain any water away when it was hanging in the normal position from the proper mic hanger, but maybe not? It hangs in the proper vertical orientation on the console so it didn't fill up because it was lying face up or anything.

Can you change the mic on these sets? The handbook makes no mention of it being removable and I can't immediately see how it is supposed to come off (maybe it isn't!)

Ta
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Old 23 May 2008, 06:03   #2
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stephen - the new icom has a special feature which as I understand it uses sound from the mic/speaker to "shake/blow/vibrate" water out when it gets wet... they call it something cheesy like "aquaquake". no idea if it was your problem or if its actually common (or a clever bit of marketing by icom) - but I bet you will give it serious consideration over the SH (which doesn't have the feature) next time you chnage fixed sets!
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Old 23 May 2008, 07:29   #3
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Stephen

I had exactly the same problem a few weeks ago with my IC-M603 which is running a standard Icom mic (as opposed to the Commandmic with which it is compatible) and which I suspect is the same mic as yours. The symptoms were identical: receive perfect, transmit reported as unreadable at even close range where h/h worked fine. What prompted more urgent action was that channel changing became difficult and didn't always go to the required one.

I am not sure how your mic attaches but mine simply screws in (so as to be easily interchangeable with the Commandmic) and it was therefore a simple job to unscrew it to take home and work on in the warm and dry.

Upon unscrewing the mic (four Philips screws from memory) I found small beads of water in the bottom and considerable moisture throughout the inside. It was a relatively easy job to dry it out (tissues, cotton buds etc.) and then reassemble having left it open in the airing cupboard overnight. Problem solved.

Quite why a highly waterproof transceiver should come with an apparently unwaterproof mic is odd. Interestingly, there was no salt residue inside the mic and I therefore assume it was fresh (rain) water rather than sea. Perhaps one more sign of the wetness of last summer!

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Old 23 May 2008, 07:48   #4
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David,

Thanks. Mine goes into a (presumably waterproof) fitting on the RH side of the radio front panel and there is no immediately obvious way to take it off, the radio is sealed into the console so I don't want to take the whole thing out and disturb the sealing. Does anybody know if/how the mic can be removed? The boat is outside so if it leaves the radio open to moisture ingress it might not be an option, but I just wondered.

It is amazing what you can fix with an airing cupboard - at the same time I got my phone wet with salt water (in a pocket on the suit and the flap was inside not outside) took battery out immediately then later rinsed it under a cold tap for a while to wash the salt out, put it in the airing cupboard overnight and it woke up happy

cheers

Stephen
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Old 23 May 2008, 07:52   #5
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Mine looks like the attached pic I just found on Google, same mic as well I think
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Old 23 May 2008, 08:01   #6
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If you can get one, its often worth dropping a desiccant bag into something like that when you put it back together.

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Old 23 May 2008, 12:44   #7
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Now that is a good idea - ta
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Old 23 May 2008, 15:30   #8
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The same thing happened on my M-601. A drop of water had landed on/in the microphone hole - but it took ages to work out what was happening.

A quick blow into the mic 'hole' and it cleared - and each time it has happened since, it's always been the same solution. It's only happened 3 or 4 times in 4 years. Hope this helps!!

D...
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Old 23 May 2008, 15:33   #9
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Quite a lot of what Raymarine has built has a bag sealed inside to soak up any condensation, or VERY minor leaks.
The same is true of McMurdo products.

I've not tried sourcing the bags in small numbers, only in 5K lots for work, but I'd imagine they are available somewhere.

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