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	id xma006665; Mon, 25 Aug 97 06:19:42 -0600
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To: Tree  N6TR <n6tr@teleport.com>, topband@contesting.com
From: John Brosnahan <broz@csn.net>
Subject: TopBand: Loop antennas
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>In other news, Trey and I put up a MU antenna for 80 meters.  I had 
>heard several people rave about these antennas and wanted to try one
>for myself.  Initial tests show it to have a low angle of radiation
>and effective when compared to my other antennas.  The antenna is
>basically a 2 turn loop, with about 2 wavelengths of wire.   It
>looks like a squished rectangle about 23 feet on the vertical sides
>and 113 feet on the top/bottom.  It is described in the second
>ARRL Antenna Compendium on page 39.  The antenna is mounted just
>a few feet above ground - so no part of my 80 meter antenna is over
>30 feet high.


Tree, interesting to see your use of the loop antenna on 80 and 
proposed use on 160.  The antenna as described in the Ant. Comp.
#2 is misnamed as a magnetic loop but it does work well.  I presented
some additional info on an expanded version at the Antenna Forum
at Dayton a few years ago and K4VX has taken that and other info
and published it on page 18 of the Antenna Compendium Volume 4.

Extensive modeling by K9AN and myself plus testing on 40M by
K9AN indicate that there is no advantage to making it into
a 2-turn beast.  A plain "squashed" quad loop will do the same thing.

If the loop is very close to the ground you can improve its performance
by placing one or more wires on the ground, parallel to the loop
to reduce ground losses.  But if you can get the bottom 15 ft or
more off the ground on 80M the need for ground wires is reduced.

I have been wanting to do a pair of double loops on 160 that are a 
1/4 wave apart and phase them but haven't decided where to put the 
thing.  Have six 65 ft utility poles "in the junk box" (heck of a junk box
--I actually have 25 of the poles) and the wire--just need the ambition.

Currently rebuilding the phase box and the radial system for the
160M 4-square.  (Four 160ft Rohn 25 towers with elevated feedpoints
at 25 ft.)   Your post on the band starting to get better is good
incentive to get serious again (actually, I guess I am already too
late!).

Hope to join the 160M fun again as soon as I repair the coyote
damage to the feedline.  They love to chew on that hardline!

73  John  W0UN



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