My first step would be to check the integrity of all ground connections...especially anything to do with the radio or the charger. And don't forget the 'heavy' ground connections at the batteries and the engine block.

Old electronics troubleshooting rule: Whenever faced with odd and confusing symptoms, in almost every case they can be chased to a bad ground somewhere. (Anyone ever work on a Lucas electrical system? Lotus? MG? Well, you'll know what I mean.)

If your charger is very old, it may use an old technology that creates the interference. I'd suggest moving up to a newer, multi-level charger. I changed out my old one a while back and it was pretty easy.
-Tom Farr
1986 Catalina 36 #591
Santa Barbara, CA

I had the same issue. (and I have a newer Trucharge 40+)
Found that the radio did not have a ground connected to chassis. (just was using the -ve from the power connection)
Try connecting a separate ground from the chassis to your ground buss behind the panel.

I am curious myself- I have similar problem. But it is not when shore power is connected. It will make awful scratchy sound like the antenna is loose. I replaced the VHF radio for that reason and still have the same problem. The chassis ground is an interesting idea. I will try that too.

Haro, your problem may be from a different cause. "Scratchy sound"? As you are listening to it? Or as other people are listening to you? Or both? You say it is as if the antenna was loose. Easy to check that. Just borrow another antenna and 10 feet of coax cable, hang it over the lifelines, and use the radio, transmitting and receiving, to see if there is any improvement.

Just like the old Peanuts cartoon where Lucy hangs out a sign saying, "Psychiatric Help 5 Cents".

[QUOTE=pmeyers;16135]Larry, you were right, it was a ground issue.
Now I can stop using my iPhone as a cheap portable radio in order to
listen to NPR. [/QUOTE]

Some where along this thread I tought the discussion was concerning the VHF radio, but now I understant it is a FM/AM. The seperate ground to the chassis might help with my AM/FM reception as well as I believe the power is the only connection from the battery on my radio and there is no ground....as I recall, so thanks for the idea.

Note on my icom vhf there is a ground attached to the chassis

I was involved for many years with communications in the Coast Guard, Grounding issues were always the number on thing to check for any type of poor signal/RF problems.
And Larry - those older British cars gave lots of headaches, for sure!! haha

[QUOTE=LCBrandt;16136]Just like the old Peanuts cartoon where Lucy hangs out a sign saying, "Psychiatric Help 5 Cents".[/QUOTE]

Only unlike the Peanuts cartoons, Larry isn't likely to set you up like Charlie Brown with the football....

Howard, I used to have a neighbor who owned an old Lotus, and he called on me regularly for the oddest damn problems. And Gary, I would never think to charge as much as Lucy did.

For sure. But those old hardwood dashboards on some of them were bee-ootiful! ;)

Larry - it is while monitoring, instead of hearing a transmission from someone the speaker will transmit intermittant static then stop. It appears that the squelch control should realize that this is a weak signal and not turn on the speaker - but it does. So I bough a new radio - no luck on the scratch. And I do have a sencond temporaty antenna attached as you suggested - but I have not had a chance to go out with it. The 45 F temperature is keeping at home. More later...

[QUOTE=baysailor2000;16148]Larry - it is while monitoring, instead of hearing a transmission from someone the speaker will transmit intermittant static then stop. It appears that the squelch control should realize that this is a weak signal and not turn on the speaker - but it does. So I bough a new radio - no luck on the scratch. And I do have a sencond temporaty antenna attached as you suggested - but I have not had a chance to go out with it. The 45 F temperature is keeping at home. More later...[/QUOTE]

I had a sort of similar problem, but with a hand held. Whenever tuned to channel 13, there was a constant 'sssssshhhhhhsssss'. The kind of background noise you usually get rid of via the squelch. But the other channels were fine; and if I turned the squelch up enough to silence the noise on 13, only the very loudest of signals would get through on 16 or any other channel. Some days it would be fine, and was the last couple times I used it. The main, installed VHF would always be silent on 13 when the hand held was making noise. Engine running/off, in slip/at anchor, no difference. Guess it could be the radio, but it seems to work fine otherwise.