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Re: [TowerTalk] Routing Ladder with Parallel Coax?

To: "Richard Cariello" <rcariello@tampabay.rr.com>, "Tony" <dxdx@optonline.net>
Subject: Re: [TowerTalk] Routing Ladder with Parallel Coax?
From: "K0DAN" <k0dan@comcast.net>
Date: Sun, 6 Apr 2014 12:21:21 -0500
List-post: <towertalk@contesting.com">mailto:towertalk@contesting.com>


-----Original Message----- P.S. Two lines of RG-11, 75/2=37.5 ohms. Two lines of RG-8, 50/2=25 ohms. Not much of a difference to worry about.


           ------

If you don't tie the coax shields together you basically have parallel feedline at higher Z all the way through. The goal is to preserve the 400 or 600 ohm ladderline impedance all the way through. The coax is gonna effect that, but two 70 or 50 ohm lines in parallel is a bigger Z-bump than if you just leave the shields floating.

Also, if you're using a T or Pi network tuner, it's not truly balanced. Should work except with most extreme Z's, but another variable to keep in mind.

At least that's been my experience, YMMV.

73
dan
k0dan
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