[TowerTalk] Wire grounding question

john at kk9a.com john at kk9a.com
Wed Nov 20 20:42:12 EST 2013

According to Jeff, it is not necessary to shield the pulse wires when using 
a Green Heron Controller, however I also use a shielded sensor cable with my 
prop pitch motors.  One of the rotators has 450' of control line and it 
great.  I did ground the shield to the tower and used MOV's on all of the 
other wires. It has survived multiple direct lightning strikes without issue 
except the MOVs start leaking slightly.  This messes up the Green Heron ramp 
feature. I replace some of the MOVs with 75v GDTs which do not leak.  I am 
not sure what the failure mode is or the amount of protection gas discharge 
tubes have compared to metal oxide varistors. Perhaps someone on the list is 
knowledgeable in this area.

John KK9A

To:TowerTalk <TowerTalk at contesting.com>
Subject:[TowerTalk] Wire grounding question
From:Ray Benny <rayn6vr at cableone.net>
Date:Wed, 20 Nov 2013 00:08:50 -0700
List-post:<towertalk at contesting.com">mailto:towertalk at contesting.com>

I am using a K7NV prop-pitch rotator for my almost completed tower project.
For the encoder (magnetic pulse counter) that is mounted inside the PP
motor, I am using a 2 pair small wire cable that has an aluminum foil
shield and ground wire. I will be installing a lightning arrestor at the
base of the tower for these two conductors.

My question, should I ground this foil shield or leave it floating at both
ends (PP rotator and rotator control box)? I would think that it should be
grounded, but does it matter?  Any consequences if I do or don't?


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