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Re: [TowerTalk] Grounding control line shields at tower base

Subject: Re: [TowerTalk] Grounding control line shields at tower base
From: Steve Gehring <>
Date: Fri, 30 Jul 2010 20:07:23 -0800
List-post: <">>
  Hi Jim,

If you have the financial means, the shields of tower coaxial 
transmission lines should be bonded to the tower at or near the top AND 
bottom. The idea here is to shunt as much of a strike's transient 
current to the tower as possible (the metal conducting mass that can 
handle the current), then effectively drive as much of the transient 
current into the bonded tower and building ground system as possible -- 
before it enters the building and contained electronics.

Following these premises, again the shields of the coaxial lines should 
be bonded to an external building ground buss bar, which (in turn) 
should be grounded/bonded to the nearby building services' entrance 
panel ground (electrical, phone, and cable entrance/ground). Note the 
coaxial surge suppressors are typically mounted nearby the building's 
cable entrance panel and ground buss bar(s), since the are also bonded 
to that ground.

Moreover, the tower(s) ground system(s) should be below-grade bonded 
with a large conductor (2 AWG or larger) to the building's services 
entrance/ground (since these two should be close to one another and 

I believe the site tower and building bonding idea is to have any 
potential transient rise/fall times to be equalized (through bonding) as 
much as possible, thus reducing the potential of differential voltages 
from taking out equipment. Concurrently, the other idea is to shunt as 
much energy as possible to earth-ground before it enters the building.

Motorola's R56 is far more detailed than this... it follows/meets Code 
and goes way beyond it. What I've said is a rudimentary summation of 
external grounding/bonding -- of which I suspect more than a few will 
criticize and/or expound upon. I suggest reading R56 for yourself. It is 
commonly available in PDF format (about 21 MB).

Follow local Code, but know there's much more you can do to further 
abate potential lightning damage. You can go beyond it for added peace 
of mind. It boils down to how much you want to spend. ;)

73 de Steve, NL7W

Reference: Bonding to the External Grounding Electrode System, 
Motorola's Standards and Guidelines for Communications Sites (R56), 
68P81089E50-A 3/1/00 — UP, page 6-5 and others.

On 7/30/2010 9:42 AM, Jim McDonald wrote:
> I am trying to improve my grounding system, which I thought was pretty good,
> after a lightning strike in April.
> I now have Array Solutions control line arrestors at the base of the tower
> for my SteppIR, rotor, and DX Engineering remote antenna switch.  The
> SteppIR and antenna switch lines are shielded.  Should those shields be
> grounded at the bottom of the tower?  How about at my grounding panel at the
> entrance to the house, where I have ICE arrestors?  (I would assume so to
> both.)
> Jim N7US
> _______________________________________________
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