ICOM M502 and remote mic problem

[jmcaleer]

Hi all!

First, I'm cross-posting from another forum so apologies if you've already read this. Here's my issue:

We currently have, as listed above, an Icom IC-M502 on the "good old boat" we purchased a couple of years back. Since we got the boat the hand mic was a problem. All of the functions of the transceiver mounted down at the nav station seemed to work fine.

I replaced the hand mic because it was cutting in and out and traced it to some bad connections in the coil cable between the navpod and the mic itself. However, the volume is extremely low with a lot of what I can only describe as "interference"(I don't know if I'm using the correct terminology- sounds a bit like a 60 cycle hum but not quite).

I thought that maybe the cable between the transceiver and mic was shot and since the new one came with a new cable I tried that. No change. Very low audio both receiving and transmitting. Tested with a friend to his handheld and he could barely hear me.

Thoughts? What else could I troubleshoot? Is it possibly the connector at the back of the transceiver? If so, is that repairable?

The admiral is pretty annoyed with me after spending the $$ on the new hand mic and still having problems.

 

[Don S/V ILLusion]

It could be a myriad of causes but rather than guess, can we start by eliminating the antenna, all connections including the 12 v ones and an idea of what the voltage is while 'keying' the microphone?

 

[jmcaleer]

It could be a myriad of causes but rather than guess, can we start by eliminating the antenna, all connections including the 12 v ones and an idea of what the voltage is while 'keying' the microphone?

I'm sorry, I may need to clarify. Transmitting and receiving from hand mic at the transceiver down at the nav station seems to be fine, it is only the remote mic that is an issue. By swapping the 25' extension for a new "out of the box" I thought to isolate that and the brand new remote mic. So I seem to be back to the radio itself. Am I thinking about this correctly?

Could the antenna impact this? I wondered about the antenna but ruled it out as everything is "five by five" from the main unit itself. I presumed that if there was a problem there that both microphones would have issues, but my knowledge of radios is pretty thin.

As for voltage, would that be whether the entire unit has enough juice?

 

[jmcaleer]

and I just realized that I posted this in the wrong forum. Can anybody guide me on how to move it to the correct forum?

 

[Don S/V ILLusion]

Didn't understand the issue is limited only to the wired mic. Ignore my earlier comments.

 

[Kestle]

Sounds like you need a choke on the radio's power cable.

 

[jmcaleer]

Sounds like you need a choke on the radio's power cable.

Doing a little reading, I was wondering about this. Wouldn't that affect the transmit and receive from the mounted unit as well? The issue seems to be confined to the remote microphone.

 

[Kestle]

They are cheap, and don't impact transmission/reception.

On Volume, if you can open the unit, look for corrosion on the speaker wires. There is also usually a external speaker output you can use to check the speaker itself.

 

[kbuckley]

Get in touch with ICOM technical support. It is possible the old defective cable caused damage in the base unit that is affecting present performance and the unit needs to go back for repair.

 

[salishmermaid]

Get in touch with ICOM technical support. It is possible the old defective cable caused damage in the base unit that is affecting present performance and the unit needs to go back for repair.

I recently called ICOM customer support about low transmit volume.

I found that the cause was how I was holding the mic. I typically held it in my right hand and partially covering the lower face of the mic.



The microphone is actually the small hole above the HI/LO button, so I was covering the microphone and talking into the speaker.



I have mixed feelings about discovering this as now I have lost my excuse to upgrade to a new unit with AIS capabilities.

 

[woodster]

I recently called ICOM customer support about low transmit volume.

I found that the cause was how I was holding the mic. I typically held it in my right hand and partially covering the lower face of the mic.

View attachment 91219

The microphone is actually the small hole above the HI/LO button, so I was covering the microphone and talking into the speaker.

View attachment 91220

I have mixed feelings about discovering this as now I have lost my excuse to upgrade to a new unit with AIS capabilities.

live on the wild side ...go ahead and do it ya know ya want it and will get it eventually

 

[bawlmer]

If you think interference is the slightest possibility then you probably need to install a ferrite collar on the remote cable. It clips around the cable as close as possible to the back side remote mic jack. When I bought a SH with remote the instructions said it was extremely important that you use it. Get one and install it before you spend any more $$$.

 

[JamesG161]

I have the same unit you have. I am also a ham.

Radios normally come equipped with a internal noise filter that sends low frequency "hums" to ground. Since it is an FM, most nature made noise is AM and should not be the problem.

So...

My guess is the remote mic cable shielding in NOT grounded to the ICOM's ground.

Or...

The antenna or ICOM has a lose or bad ground (less likely).

Do a radio check on non 16 channel with a friend. If your friend doesn't hear the "hum" then it is the cable.

The ferrite coil is good attempt at filtering "hum", but the fact that the Nav Station mic works says the cable has lost it ground to remote mic.

You can check your grounding with a Volt meter in continuity mode (resistance ohms).
Jim...

PS: I wanted to upgrade too integrate with my new 2015 electronics, but decide for my ±200 mile cruising range the AIS would at best be a "Friend Finder". My iPad has an app for that!