[TowerTalk] Wire grounding question
rayn6vr at cableone.net
Thu Nov 21 01:32:57 EST 2013
Mark and All,
I have no problem grounding the foil and ground wire in this encoder cable.
I am puzzled though, inside the Green Heron Controller, each terminal lug
going to the PP and encoder has an MOV across it to ground. In one
discussion of where to place MOVs, it was highly recommended not to place
additional MOVs anywhere but at the base of the tower or at your SPG.
I did not fully understand the explanation but if this is so, then the MOVs
in the Controller should not be there but at the base of the tower either
attached manually or through a lightning arrestor device. For Green Heron
controller, they probably provide MOVs since many non-serious installations
may not have any lightning protection at all.
Just my thoughts.
On Wed, Nov 20, 2013 at 6:42 PM, <john at kk9a.com> wrote:
> 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
> 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
> except the MOVs start leaking slightly. This messes up the Green Heron
> 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
> 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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