When do you find the BOP useful - is it useful for DX contest?
To: towertalk@contesting.com>
Subject: Re: [TowerTalk] VE3GK stacking drawing
From: "Tim Duffy K3LR"
Reply-to: k3lr@k3lr.com
Date: Sun, 7 Oct 2007 23:38:40 -0500
List-post: <mailto:towertalk@contesting.com>
Hello Stein!
Starting on page 130 of Volume 7 of the ARRL Antenna Compendium shows the
mono band stacking schematics I use. They are built from 1/4 wave sections
of RG213, RG11 and RG83. The book is available from the ARRL.
My two high stack switch design is simple using only RG-83 (35 ohm coaxial
cable) to match 2 parallel 50 ohm loads and another 1/4 wavelength of RG213
is used when feeding the single Yagi's so that the line length to the
amplifier is not changed regardless of antenna selection. This keeps the
VSWR at the same point which keeps the amplifier happy regardless of antenna
combination.
I also have a design that incorporates a both-out-of-phase (BOP) selection.
This creates a high angle lobe. We use this feature on 40 and 20 meters.
I use these designs for all of my 2,3 and 4 high stacked Yagi arrays.
The secret to good Yagi monoband stacking is using exact ODD quarter
wavelength feedlines (current forcing) to feed the individual Yagis.
I would be happy to scan my two high design and email it to you if you like.
73!
Tim K3LR
http://www.k3lr.com
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