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Re: [TowerTalk] Coax Lengths for Stacked Yagis

To: towertalk@contesting.com
Subject: Re: [TowerTalk] Coax Lengths for Stacked Yagis
From: Jim Brown <jim@audiosystemsgroup.com>
Reply-to: jim@audiosystemsgroup.com
Date: Sun, 6 May 2018 23:12:38 -0700
List-post: <mailto:towertalk@contesting.com>
Yes.

Another point -- a length of line that is a quarter-wave at 14175 is NOT a quarter-wave at 14000 and 14350.

To answer both points, it seems best  to build as complete as practical NEC model of the antennas, including their physical relationships in the stack, and all phasing and matching cables, then studying patterns and gains over the needed bandwidth. There's a good discussion of this, with examples, in the ON4UN book, credited to Al Christman, K3LC.  I used his design method (and built the NEC model) for a 2-el 40M array that we used for a couple of CA QSO Party expeditions.

The antenna seemed to work well, but required a lot of work to string out the 32 radials we used for each element, which is why we stopped using it.

73, Jim K9YC

On 5/3/2018 9:06 PM, Wes Stewart wrote:
Another point or two and then I'll shut up.

1)  The expected phase shift in a line is only achieved when the line is matched.


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