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[TowerTalk] Interconnections

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Subject: [TowerTalk] Interconnections
From: (Bob Wanderer)
Date: Fri, 10 Dec 1999 11:57:21 -0800
You should connect the power ground to the tower ground via
the single point ground system established where the cables come
into the building.  

Whether or not the grounds will "see" one another is a different issue.
The PolyPhaser position when I was there was that after about 50~100
feet, the inductance of the earth would have "swamped" the surge current.
That is why the radials extending from the tower were no longer than that.
Once the distance between grounds (i.e. tower and power in this case)
significently exceeded this distance, they should be treated as separate
systems.  What value(s) qualify as "significently exceeds" is a matter of
opinion; mine has been 100~150  feet.  While nothing is lost (except
time and money) installing a tie when the distance is excessive, I don't
believe that anything is gained.  Of course, everyone is entitled to their
opinion and the person paying the $$ has to decide on what course of action
he or she will take after perusing the various opinions, the qualifications of
the person expressing said opinion, their own thoughts on the matter, and
whatever other parameters are involved.  As an alternative, consider wider
strap or larger round members for these distances to make the inductance
(impedance) as minimal as possible.

Realize that the coaxial cables carry only a small amount
of the total surge current and that this value will decrease as more
and more coaxial cables are added (i.e. the worst case scenario
occurs when there's only one cable).  Read the PolyPhaser 
tutorial "The 'Grounds' for Lightning and EMP Protection" and you 
will understand the dynamics of this situation.

Ham installations usually involve a tower fairly close to the house and a
shack in the basement or ground floor.  These are usually straightforward
because "excessive" distances are not involved and all the locations which
have to be tied into a proper single point ground are reasonably close to
each other.  The ham is also not faced with providing 24/7 services.

The tower and single point entrance panel (ground) are usually tied together 
one of the radials.  The power ground was ties to the single point entrance 
(ground).  This generally allows every ground point to "see" every other ground

Anyway, I am in the process of moving to the Philadelphia, Pa area, so soon I
will have little time to really get involved in these discussions and for a 
while I
will be QRT.  Once I am established there, I will once again provide my point 
of view (opinion) for folks to agree or disagree with.

Kent, Wash (near Seattle)

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