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Re: [TenTec] OT 75 Ohm twin feeder

To: Discussion of Ten-Tec Equipment <tentec@contesting.com>
Subject: Re: [TenTec] OT 75 Ohm twin feeder
From: Steve Hunt <steve@karinya.net>
Reply-to: Discussion of Ten-Tec Equipment <tentec@contesting.com>
Date: Thu, 12 Jun 2008 23:05:49 +0100
List-post: <mailto:tentec@contesting.com>
Jerry,
Two pieces of 75 ohm coax in parallel (corresponding conductors
connected together at each end) gives 37.5 ohms. Two sets of those in
push-pull gives 75 ohms shielded balanced. Or the same with 50 ohm coax
gives 50 ohms balanced.
That would work, but using four lengths of coax to replace one seems a bit OTT
The jacket is the least consistent part of the coax and I believe it to
be loaded with carbon to make it black and UV resistant. That would make
it lossy (and slightly improve the shielding properties) to some extent.
I've just ordered a short length of RG-400 to try in place of the RG-58. It seemed to me the outer jacket (FPE) would have better RF characteristics than the PVC.

Tried the RG-58 option on my Hexbeam today and it took the max I could throw at it - 400W.

Steve G3TXQ


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