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Re: [TowerTalk] Antenna/Tower Grounding (Lightning Protection)

To: "'Jerry Keller'" <>, <>
Subject: Re: [TowerTalk] Antenna/Tower Grounding (Lightning Protection)
From: "Dick Green WC1M" <>
Date: Thu, 4 Jan 2007 11:49:16 -0500
List-post: <>

I believe the idea is to ensure that there's not a voltage differential
between the top and bottom of the coax. If there is, a charge could travel
from one end to the other, damaging the coax. 

In the typical amateur installation, the coax shield is probably grounded
inside the shack, but nowhere else. Many antennas, such as yagis, dipoles,
vees, etc., don't ground the shield. It's likely that a surge picked up by
the element connected to the shield will travel all the way to the shack,
causing damage.

In a better installation, the coax shield is connected to a single-point
ground outside the shack. That may save the equipment in the shack, but a
surge will still travel from the antenna to the single point ground,
possibly damaging the coax (many have found "pinholes" in the coax jacket
from this.)

An even better installation will ground the coax shield at the base of the
tower, perhaps where it connects to a switch or to a set of lightning
suppressors. But the charge can still travel from an antenna at the top of
the tower to the base, damaging the coax.

The solution is to ground the coax shield at the top and bottom of the
tower. Special grounding kits are made for coax and heliax for this purpose.
You strip off a section of the jacket and wrap a copper strap around the
shield. The strap has a wire that clamps to the tower. You have to use vapor
wrap and tape or special booties to waterproof the area where the strap
connects to the cable.

Professional installations are done this way. I'm not sure, but I think the
coax may be grounded at several places on the tower when the runs are very

Of course, a charge can still travel down the center conductor, even if
there's a lightning suppressor at the bottom of the tower. It's always
puzzled me that companies like Polyphaser don't recommend mounting
suppressors at the top of the tower, too.

73, Dick WC1M

> -----Original Message-----
> From: Jerry Keller [] 
> Sent: Thursday, January 04, 2007 10:26 AM
> To:
> Subject: Re: [TowerTalk] Antenna/Tower Grounding (Lightning 
> Protection)
> In his well-stated list of grounding advice, Gene AD3F 
> includes: "3.    You 
> ought to ground each coax cable shield to the tower at the 
> top and at the bottom of the tower."
> I've seen this advice before, but have never understood the 
> reason for it, or what the adverse consequences might be if 
> everything else Gene recommends is done, and this is not (as 
> is the case with my system).  Can anyone explain this for me, please?
> 73, Jerry K3BZ
> ----- Original Message -----
> From: <>
> To: "Richard W. Solomon" <>; 
> <>
> Sent: Wednesday, January 03, 2007 11:52 PM
> Subject: Re: [TowerTalk] Antenna/Tower Grounding (Lightning 
> Protection)
> > Dick:
> >
> >     Below are some nuggets of wisdom I've gathered from reading the 
> > postings on this reflector over the years.
> >
> > 1.     You cannot protect the tower, antennas and rigs from 
> a direct 
> > lightning strike.   You can only attempt to minimize the 
> damage if that 
> > happens.
> >
> > 2.    Your tower ought to have at least one ground wire, 
> minimum of #8 
> > gauge wire, to one ground rod within two feet of each tower 
> leg.  The 
> > latest version of the National Electrical Code mandates two 
> ground rods 
> > and two wires at each leg.
> >
> > 3.    You ought to ground each coax cable shield to the 
> tower at the top 
> > and at the bottom of the tower.
> >
> > 4.     You ought to install lightning suppressors on all 
> wires and cables 
> > coming into your shack.  Polyphaser makes these as do ICE 
> and Delta.  <All 
> > cables> includes the coax runs, your control lines to your 
> rotator and 
> > antenna switch(es), and any DC or AC supply lines going up 
> the tower.
> >
> > 5.      You ought to install these suppressors immediately 
> outside your 
> > shack entrance onto a single-point ground (SPG) panel.  
> This panel ought 
> > to be connected to another ground rod via another #8 
> minimum ground wire. 
> > The ground connections from all the electrical systems 
> within your house 
> > (electrical supply panel, cable TV, telephone, etc.) should also be 
> > connected to this SPG panel.
> >
> > 6.     You ought to search the TowerTalk archives for 
> details on how to do 
> > all of these things.
> >
> > 7.     When you have finished reading all you can stand, 
> come back to this 
> > reflector again and ask some more questions.  We're only 
> too glad to help.
> >
> >     What did I miss mentioning, gents?
> >
> > 73 de
> > Gene Smar  AD3F
> >


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