----- Original Message -----
From: "Pete Smith" <n4zr@contesting.com>
To: "Ward Silver" <hwardsil@centurytel.net>; "Towertalk Reflector"
<towertalk@contesting.com>
Sent: Saturday, January 15, 2005 12:16 AM
Subject: RE: [TowerTalk] Station Ground
> Just a sidelight on this. As a legacy of the past, I have a bus-bar
system
> connected to my single point ground bulkhead, but alas, the distance to
> actual ground from my second floor window is several meters and the ground
> lead cannot be straight. Despite my use of copper tubing for the bus bar
> and heavy copper ground leads from every piece of equipment, I found that
> when I tried to use my sound card for contest "voice keying" I had fairly
> severe AC hum on the audio, apparently the result of a few millivolts
> potential difference between chassis. I finally cured it by
experimentally
> connecting the chassis of the computer and radios directly to one another
> with heavy copper (not through the bus bar).
Was the audio transformer coupled, or direct coupled?
Was there a break in the audio ground side? (so that the "ground reference"
for the two single ended audio signals was the busbar)
As an aside, most computers aren't really designed with a heck of a lot of
attention to audio grounding.
So, when are radios going to start using optical links (like TOSlink)? Yes,
the cables are pricey (for no good reason... they're cheap 1000 micron
plastic fibers), but ZERO ground loop potential.
Even wired ethernet is transformer isolated (not to mention digital) as are
most high performance interfaces (MIL-STD-1553, for instance). (and
precisely because of grounding issues)
Jim, W6RMK
_______________________________________________
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
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