[TowerTalk] Grounding an Insulated Tower

[David Robbins K1TTT]

Why not connect the coax and radials to the lower tower sections and to
ground through them??  

For static bleed you can use a shorted quarter wave stub, a high resistance
bleeder, or large inductor.  The stub has the advantage of acting as a
bandpass filter.  Lightning protection on commercial towers is typically a
spark gap.

If you don't ground the radials at the tower you also have to worry about
lightning protection for them, they could be hit or take a sideflash from
the tower if it gets hit.  Either way would put high voltages on the shield
that would have no where to go except toward the shack.


David Robbins K1TTT
e-mail: mailto:k1ttt at arrl.net
web: http://www.k1ttt.net
AR-Cluster node: 145.69MHz or telnet://dxc.k1ttt.net
 

> -----Original Message-----
> From: towertalk-bounces at contesting.com [mailto:towertalk-
> bounces at contesting.com] On Behalf Of Richard L. King
> Sent: Sunday, January 06, 2008 13:10
> To: towertalk at contesting.com
> Subject: [TowerTalk] Grounding an Insulated Tower
> 
> Hi everyone. HNY.
> 
> I am near completion of a 155 foot 25G tower with an insulator 30
> feet above ground to use on 160M. I am interested in techniques for
> grounding for lightning protection and to bleed off noise from rain
> static, etc.
> 
> The tower will be fed directly with the coax to the upper insulated
> part and the coax shield will be connected to several raised radials.
> The coax and the radials will NOT be connected to earth ground at the
> tower.
> 
> I am worried that a direct lightning hit might cause me sever
> problems if I cannot bleed it off somehow. I have thought about
> lightning spark gaps and maybe a large inductor between the insulated
> section and the lower part of the tower, but not sure how that will
> work and what should be the values of those components.
> 
> I do plan to ground the lower, unattached, section of the tower with
> ground rods.
> 
> Thanks.
> 
> 73, Richard - K5NA
> 
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