[TowerTalk] Ground Windows

[Gary Schafer]

> -----Original Message-----
> From: towertalk-bounces at contesting.com [mailto:towertalk-
> bounces at contesting.com] On Behalf Of Jim Brown
> Sent: Friday, July 28, 2006 10:29 AM
> To: Tower Talk List
> Subject: Re: [TowerTalk] Ground Windows
> 
> On Fri, 28 Jul 2006 14:19:19 +0000, Phil Camera wrote:
> 
> >Also to this SPG, you will run your shack equipment ground out to
> >it and also connect the SPG to your tower ground and your
> >electrical service entrance ground.
> 
> Yes. But:
> 
> There is considerable misunderstanding (and junk science)
> regarding so-called "single point grounds." 


> The ONLY safe place for SHUNT-MODE surge suppressors is at the
> service entrance, where they raise the entire "ground" bus above
> earth by the same voltage. (this is the so-called "whole-house"
> surge suppression).

> The bottom line: We MUST bond our equipment together and connect
> it to "earth" for safety. We do NOT need those connections to make
> our ham stations or antennas work (or work better), nor to reduce
> noise. A "SPG" does NOT mean only one ground rod. Rather, it means
> ALL grounds are bonded together by beefy low inductance paths.


So as not to confuse anyone about "single point ground systems" it is
important to understand that it is a common point that all equipment, power,
antenna leads, phone lines etc. are bonded at.
While all grounds (and many of them) should all be tied to each other, the
equipment should only be connected to the ground system at one point and one
point only (the single point ground). 

The power must have the protection devices at the single point ground. The
antenna system must have its protection devices at the single point ground.
The equipment is only fed from devices attached to the single point ground.

If the power comes into the opposite side of the house from where the
antenna lines come in, the easiest way to handle that is to run a power
cable to the single point ground panel. The power protection devices would
mount on that panel along with the coax protection devices. The panel is
tied to the ground system by a very short wide ground strap. If telephone
lines go to the same equipment they would have protectors mounted to the
same panel. 
Nothing goes to the equipment without first going to the single  point
ground panel.  That is a single point ground.

As far as low resistance ground connections go, it is indeed important.
While low inductance of leads is important it is also important to remember
that even a fraction of an ohm in ground lead connections can allow very
high voltage differences across a poor connection. This is why we cadweld
the ground connections

Shunt mode surge protectors need to be placed at the single point ground
panel to insure everything there goes to the same potential during a strike.

73
Gary  K4FMX