[TenTec] OT 75 Ohm twin feeder

[CSM(r) Gary Huber]

Try common "lamp cord"... the two conductor parallel kind. depending upon 
gage of the conductors, you will find them very close to 75 Ohm.
Obviously not a high power solution.

73,
Gary - AB9M
www.csm-gh.com

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From: "Steve Hunt" <steve at karinya.net>
Sent: Wednesday, June 11, 2008 3:35 AM
To: "Discussion of Ten-Tec Equipment" <tentec at contesting.com>
Subject: [TenTec] OT 75 Ohm twin feeder

> I've been experimenting with ways of constructing 75 Ohm twin feeder for
> a Hexbeam application - it's now very difficult to get the heavier duty
> commercial cable - the only manufacturer in UK has ceased production.
>
> On my website I recommend using 50 Ohm coax for the Hexbeam band
> interconnects, but folk who opt to use the higher power handling RG213
> sometimes have difficulty making off the ends. Twin feeder would be
> easier to use, and as long as its characteristic impedance was  less
> than about 80 Ohms it would work fine.
>
> It turns out that 2 lengths of RG58 taped side by side produce the right
> value Zo, using the braids as  "fat" conductors spaced by the PVC
> jacket. In a final version I would probably hold them together using
> heatshrink tubing. I only need short lengths - maximum 24" - so losses
> are not likely to be an issue.
>
> I wondered what's a good way of estimating the power handling capability
> of this arrangement. What's likely to be the limiting factor - the
> voltage breakdown through the PVC ?
>
> Grateful for any views.
>
> Steve, G3TXQ
>
>
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