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[TowerTalk] Grounding for Lightning Protection

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Subject: [TowerTalk] Grounding for Lightning Protection
From: (Roderick M. Fitz-Randolph)
Date: Fri, 25 Jul 1997 19:37:11 -0500
My tower is located 250 feet from the shack.  I run coax underground
for that distance, including some CATV 1/2" 70 ohm coax with bare
aluminum jacket buried directly in the ground.  There is a Motorola
waterproof steel cabinet mounted on cocrete at the base of the 130
foot tower.  The cabinet has electric power running to it from the
house via underground Romax.  The ground wire is connected to the
electrical ground lug on the outlet sockets.  There is an MFJ RCS-4
relay box mounted near the base of the tower.  The ground plate on
the MFJ relay box is connected electrically to the 1/2" 70 ohm CATV
hardline that runs the full 250 foot length.The tower is guyed with
nonconductive  material on the top two levels and with 1/4" steel guys
at the two lower levels and these are broken by insulators.  I have
6 groundrods at or near the base of the tower.

I have been studying the excellent PolyPhaser book and watching comments
on TowerTalk.  I understand that it is to one's advantage, protection-
wise, to have a common ground between the tower's ground rods, the
PolyPhaser bulkhead panel, and power ground.  However,I have difficulty in
imagining that my running a no. 10 or no. 8 or even no. 6 wire for the
250 feet so that my equipment, the PolyPhaser in-line coaxial lightning
protection devices and their bulkhead panel can all be at a common ground
potential would be of any greater protection than that afforded by the
250 feet of CATV hardline that is run the full length and buried directly
in the ground.  Am I wrong.  Doesn't the common coaxial shield that is in
contact with the ground for the entire length of 250 feet and electrically
is connected to the ground rod at the exterior of the hamshack offer
enough common ground point protection?

Your comments and opinions are desired and welcome.

Thank you,

Rod, W5HVV

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