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[TowerTalk] Stack

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Subject: [TowerTalk] Stack
From: "Mel Martin" <>
Date: Mon, 17 Nov 2003 10:15:07 -0500
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I use 3  5 el yagis stacked in a tree...

With 7' between the 10 and 15 and 10' between the 20 and 15 the performance
is as follows.

20M... virtually unaffected...

15M... loss of about 1DB forward gain and some deterioration of F/B and a
lot more high-angle scatter

10M... loss of slightly more than 1DB and some deterioration of F/B and a
lot more high-angle scatter

On 10M and 15M the F/B at high arrival angles is very poor in a stack, but
in practice... not many signals arrive at such high angles.

This was modeled using EZNec, and seems to be borne out in practice

Quite frankly, Tree installations are pretty well discredited. In a stack,
they are no longer monobanders, but create a 3 dimensional tri-bander.
Better to use the new interlaced designs where the interaction is accounted
for in the design and there is less upward scatter from the lower frequency
antennas below.

I installed the Tree because I already had the beams... but I wouldn't do it
again... I'd rather work with 2 dimensions with the same or better
performance...There is nothing wrong with Tree performance... just
unnecessarily complex and a bear to install.

BTW, don't even think about putting anything for 12 or 17 anywhere near


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