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RE: [TowerTalk] Station Ground

To: <>
Subject: RE: [TowerTalk] Station Ground
From: "Keith Dutson" <>
Date: Fri, 14 Jan 2005 23:22:35 -0600
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Would you care to define "ground loops between pieces of equipment"?

Here are my thoughts:
An equipment ground loop is a condition where potential (voltage) can be
measured between the chassis of two pieces of equipment.  If this voltage is
under .0001 volt, is it still a ground loop?  Perhaps.  Will this voltage
have a detrimental effect on equipment operation or protection?  I don't
think so.  This is why instructions are often seen to keep ground straps as
short as possible.  To me, the ground loop that is a real problem is where
two pieces of equipment are connected to two different grounds.

The grounding window entrance (bulkhead) to my shack is shown here:
Note it is only partially populated, with expansion planned for more
antennas and another tower (in progress).  The coax cables are connected to
Polyphasers.  The control cables are also connected to Polyphasers.  To the
far left you see a large grounding braid.  This goes to the station ground
bar (Harger) located about six feet away.  All equipment chassis are
connected to this bar using smaller ground braid.

Here is an older shot of the bulkhead from the outside:
Note the large copper wires at the lower left and right corners.  These
wires are each connected to separate 8ft ground rods located straight down.
The two rods are also connected together and this connecting cable runs to
the tower ground system (another series of rods) and to the ground rod
located at the power and telephone service entrance points.

Thus, in my system, all equipment, antennas, towers and power see the same
common ground point.  Granted, there IS some potential between these
components, but it is far less than if each had its own separate earth
ground.  I feel pretty good about the lightning protection provided here.

Keith NM5G

-----Original Message-----
[] On Behalf Of Gary Schafer
Sent: Friday, January 14, 2005 9:26 PM
To: Frank Donovan
Cc:; N6KJ
Subject: Re: [TowerTalk] Station Ground

Frank Donovan wrote:

> The modern design practice is to bond all RF cables, rotator cables 
> and control cables to a common grounding "window" at the entry point 
> into the home.  All other cables (AC power, telephone, cable TV, 
> satellite, etc) penetrating the wall of the building
> should be bonded to the grounding window.   While a heavy
> ground wire could be run from the grounding window to the station 
> equipment bus bar and then to each station equipment, it is likely to 
> have such high impedance that it is highly unlikely to perform any 
> useful function.
> 73!
> Frank

With a proper "grounding window" using a buss bar to connect equipment to
can actually be a detriment. It is best to run individual ground lines from
each piece of equipment separately to the ground window.

With a common buss bar you have ground loops between pieces of equipment. If
a surge, lightning etc. should get through to one piece of equipment it will
hopefully exit via the ground to the ground window.

If there is a common buss bar the surge can enter another piece of equipment
and go through it via the ground connection on it's way to ground. The
ground lead from the buss bar will always have some impedance so it will be
somewhat above ground with a surge.

With individual ground leads to the ground window there is no loop through
other equipment. Not always doable but it is the proper way.

Gary  K4FMX


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See:  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.

TowerTalk mailing list

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