Dick:
I bought my Poly's from The RF Connection (www.therfc.com ). But they
are not made to be mounted exposed to the weather. I, like many others here
on TowerTalk, mounted my Poly's in a steel box at the base of my tower. (I
need Poly's at the tower base because they protect the coaxes before they go
into an antenna selector switch that I also have mounted in the steel box.)
There are two kinds of Poly's to choose from: bulkhead mounting and
flange mounting. I bought the bulkhead-mounting models. They are made to
be mounted with the antenna-side connector poking through a hole in the
steel box (or other mounting barrier). They include a rubber gasket to seal
out the weather at this hole.
The flange-mounting units are made to be bolted onto a flat surface,
like a single-point ground panel, and allow the coax cables (antenna side
and rig side) to simply pass over the top of the flat surface. You could
use these inside your steel box if you also used feed-through connectors and
coax jumpers in the box to get from outside to inside.
And you've opened up Pandora's box by asking whether you should add a
second set of Poly's near your shack entrance. Many here on TowerTalk will
say you need this second set on Poly's. I do not have a second set in my
installation. Poly's (and other arrestors for that matter) are designed to
keep lightning energy off the center conductor of the coax. Once the
tower-mounted Poly's take care of that energy, it's awfully difficult for
more energy to get coupled onto the coax center conductors on the (buried?)
run from the tower base to the shack entrance. It might happen that a jumbo
lightning strike to the ground nearby might couple energy onto the shield,
but I don't see a mechanism for that energy to get onto the center conductor
for a downstream Poly to take care of for you.
However, you SHOULD ground your coax cable shields at the top and
bottom of your tower as well as at the entrance to your shack. If your
coaxes come into the tower's steel box through the top without making any
sharp turns to get to it, you can consider it grounded. If, however, your
coaxes bend sharply to get into the box then you need to ground the shields
before they make that horizontal turn. Lightning sees any sharps turns as
an inductance and significant voltages could build up on the shield at that
turn, blowing through the outer jacket of the coax. Grounding the shields
once more at the shack entrance should take care of any coupled voltages
that find their way onto the shields between the tower and the shack.
73 de
Gene Smar AD3F
----- Original Message -----
From: "RICHARD SOLOMON" <w1ksz@q.com>
To: "TowerTalk" <towertalk@contesting.com>
Sent: Thursday, November 01, 2007 1:12 PM
Subject: [TowerTalk] Polyphaser Questions
> Is there a distributor for Polyphaser or does one buy direct ?
>
> What is the best way to mount them ? I didn't find any mounting info on
> the
> Polyphaser website. I think a flat plate bolted to the tower legs with
> U-Bolts ??
> or what ?
> The shack is about 80' from the tower. My plan is to install a set of
> Polyphasers
> at the tower and run the Coax and Rotor Control cable through conduit
> under-
> ground (12" or so). Would it add any value to have another set of
> Polyphasers
> at the shack entrance ?
>
> Thanks for any help,
>
> 73, Dick, W1KSZ/7
> _______________________________________________
>
>
>
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