Bill,
I've never seen any hard data showing that coax should be installed one way
or the other. I can only report that many years ago a professional antenna
engineer (and ham buddy) in Dallas strongly recommended that I route all of
the coax and control lines inside the tower. His reasoning: coax outside
the tower becomes part of the radiating element when you load the tower,
and applying high power can physically stress and damage the coax. At a
more practical level, having the coax inside the tower offers some
protection from surges in the electric field around the tower when
lightning is in the area.
73,
Brad KV5V
On Tue, Aug 9, 2016 at 10:34 PM, Gene Smar <ersmar@verizon.net> wrote:
> Bill:
>
> In my shunt-fed (gamma-matched) 64 foot tower I did option (d). I ran
> the coaxes up inside one tower leg angle iron. I used insulated #12 solid
> house wire (Home Despot 500 foot reels) to tie the cables to
> factory-drilled
> holes in the legs all the way to the top.
>
>
> 73 de
> Gene Smar AD3F
>
>
> -----Original Message-----
> From: Topband [mailto:topband-bounces@contesting.com] On Behalf Of Bill
> Hein
> Sent: Tuesday, August 09, 2016 4:01 PM
> To: Topband@contesting.com
> Subject: Topband: Gamma Match Tower Question
>
> I want to get back on Top Band this fall and am planning on Gamma Matching
> one of my free standing towers (and plant a few Beverages).
>
> The tower I'm planning on using is an AN Wireless HD-70 (70 foot tall, wide
> base that tapers as it goes up) grounded tower topped with a 15 ft mast and
> a Force 12 Magnum 340 620 Yagi, the later should make a nice cap hat.
>
> My question: I have two hardline coax cables running up the outside of the
> tower held in place by Andrew non-conductive clamps. Should I (a) move the
> cables inside of the tower, (b) ground the cables at the top of the tower
> (they are gounded at the base now), (c) do something else, (d) do both, or
> (e) leave it as is.
>
> I am also planning on grounding all the parasitic elements on the big F12
> dual bander to the boom at the element center.
>
> 73
>
> BIll AA7XT
> Glade Park CO
> DM59pa
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