What Jim says is true, but sometimes - as in my case - it's a bit
difficult to put into practice. My station is located in a finished
basement with a series of ground rods at ground level approximately 10
to 12 feet from the operating desk position connected with #0 wire.
However, the service entrance box from the buried electrical is located
at least 50 feet from the operating position. And, due to the location
of the electrical utility's ground rod, I can't get to it as it's
beneath our deck. Yes, the electrical utility installer placed it in
that location. My only option is to run a fat copper wire to the ground
at the service entrance box to bond the grounds together. My next door
neighbor is a licensed union electrician, and he would likely be the one
to tackle the job. However, due to the distance, I'm concerned with the
inductance due to the length required. I suppose the best choice would
be to locate one's shack directly within a short range from the service
entrance box/breaker box, but for the vast majority of us, this is
impractical. I'd have to kick my XYL out of our basement's laundry room
(the location of the breaker box) to convert it into a ham shack!!
Interestingly, our previous house which was built in the '50s, did not
have 3-wire distribution and grounded outlets. I never experienced any
buzz or hum with any rigs at that location. Here I do, most likely due
to what Jim described below. I also have tons (constant S6 to S7) noise
levels from the neighbor's plasma TVs, and the crappy above ground power
lines here. Our local electrical utility is strapped for cash, and they
don't want to hear about leaky insulators, even if it's costing them
distribution efficiency or problems.
Don W9CW
From: Jim Brown<k9yc@audiosystemsgroup.com>
To:tentec@contesting.com
Sent: Sunday, January 22, 2012 1:03 PM
Subject: Re: [TenTec] grounds
It is also VERY UNSAFE, is a violation of all building codes, and
provides no benefit.
A difference in potential exists when all grounds are NOT connected.
The rule, both for safety and best noise immunity (including hum and
buzz and RFI) is really quite simple. You may have as many ground
connections as you like, but they MUST be bonded together, and the
connections should be fat copper, as short as practical.
The concept of a "ground loop" is a fiction.? The REAL cause of hum and
buzz from the AC power system are LEAKAGE CURRENTS that are the result
of capacitance between the Phase ("hot") conductor and the green wire
(protective ground).? Those leakage currents flow in the green wire, and
the resulting IR drop causes a "buzz" voltage to exist between equipment
plugged into different power outlets, and to equipment that might be
GROUNDED better than, or separately from where the AC power line is
grounded.? That difference voltage is greatly reduced by properly
BONDING all those grounds together.
We HEAR that buzz on unbalanced connections between equipment because
their chassis are at different AC voltages (due to the IR drop from
their leakage currents).? These are not "ground loops," they are simply
LEAKAGE CURRENTS, and they are added to the signal because they are in
series with the signal.
The concept of a "ground loop" is simply WRONG -- more bonding is
BETTER, and is the SOLUTION, not the cause!
73, Jim Brown K9YC.
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