Pete:
I wound a few turns of my rotator cable into a solenoid form about 2
inches in diameter just below the rotator plate. Held it into shape with
some tape and cable ties. Did the same thing with the cable at the base of
the tower just before it entered a metallic box to go into the shack via a
conduit run.
My theory (ok - my guess) is that this bit of inductance would buck a
nearby lightning strike somewhat and reduce the energy that actually makes
it into the rotator (via the top solenoid) and into the shack (via the
bottom one.)
However, I still have a Polyphaser shunt arrester for the rotator lines
in another metallic box outside of the shack at the opposite end of the
conduit run, where I also have my single point ground (SPG) panel. Here,
the coax shields and the arrester are tied into an aluminum angle piece that
is bolted to the ground wire (#2 solid tinned copper) that goes to a ground
rod. One of my tower's ground radials (one of three buried 18 inches deep)
also connects to this rod, so I have a continuous conductor from the tower
to the SPG. The conduit and this radial are in separate trenches about 12
feet apart to reduce the amount of lightning energy coupling into the coax
shields in the conduit. The two meet just outside the SPG box.
I completed the tower installation late last year, after the summer
lightning season, so we'll both see how this technique works this summer.
GL es 73 de
Gene Smar AD3F
-----Original Message-----
From: Pete Goudreau <goudpj@mac.com>
To: towertalk@contesting.com <towertalk@contesting.com>
To: <towertalk@contesting.com>
Date: Wednesday, March 20, 2002 10:42 PM
Subject: [Towertalk] rotator cable lightning protection
>After some research, including towertalk archive searches, it looks
>like the only protection units out there for control and rotator
>cables are shunt types - Polyphaser and I.C.E. come to mind. While
>researching the topic, there also seems to be a goodly number of
>stories of lightning surges getting past exploding MOVs in said
>protectors and blowing up most of the equipment in the shack.
>
>Not being much of a fan of MOVs in the first place, I figured there
>had to be some series type protectors out there somewhere but I'm not
>finding them at all. Design is relatively easy but extremely
>difficult to test correctly.
>
>Anybody have any suggestions as to the safest way to keep the lines
>connected but well suppressed?
>
>Thanks in advance,
>Pete, AD5HD (ex-WB5RKC)
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