Date: Wed, 13 Apr 2011 15:55:15 -0600
Reply-To: "John C..." <jcarp1910@GMAIL.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: "John C..." <jcarp1910@GMAIL.COM>
Subject: Re: radio whine - success, failure, success
In-Reply-To: <4da60cee.9247e60a.55f3.1d7a@mx.google.com>
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What is that grounded Shield Cylinder
around some of the Distrubutors?
I thought that was for the radio reception.
but that's just a wild guess on my part.
On Wed, Apr 13, 2011 at 2:35 PM, David Beierl <dbeierl@attglobal.net> wrote:
> At 08:07 PM 4/12/2011, Alistair Bell wrote:
>
>> So now I have determine if that kind of grounding through antenna is
>> normal, or a fault.
>>
>
> I don't actually know for certain, but I'd be fairly surprised if the
> shield on the antenna lead weren't connected to the mount. It's
> certainly not *meant* to be a power ground, and it might shield the
> lead as well or better if the mount were isolated - on a transmitting
> antenna this would be a crucial difference but not as much on a short
> receiving whip. One of the VHF hams would probably have a good
> opinion about how badly it's expecting to see a ground plane on FM;
> it's so far out of resonance on AM that in my ignorance I doubt it
> makes any difference. Back when people cared about AM car radios
> used to have trimming capacitors for antenna tuning (and they had a
> strong peak, too) but I haven't seen one since the '70s.
>
>
> You said you moved the supply/ground but didn't make entirely clear
> whether you've got a big fat ground connection directly between the
> two units. I don't think we got to the scribbling stage in that
> conversation, and there are a number of interrelated issues (and I'm
> not an expert by any means). I'm enclosing a diagram showing how one
> boutique manufacturer (Milbert Amps) thinks about grounding. It
> won't show up on the list and I don't see it on their site to point
> people to it but I'll send it to people who ask.
>
> As a practical matter though, I think the isolation transformer (aka
> ground loop isolator) we talked about in the signal grounds should
> take care of you.
> http://www.radioshack.com/product/index.jsp?productId=2062214
>
> :)
> d
>
--
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