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Re: Topband: Assistance Needed

To: "Topband Reflector" <topband@contesting.com>
Subject: Re: Topband: Assistance Needed
From: "Greg - ZL3IX" <zl3ix@inet.net.nz>
Date: Sat, 25 Oct 2003 08:25:38 +1300
List-post: <mailto:topband@contesting.com>
>
> Are there other wire antenna choices?
>
Hi David,

Another one you may like to consider is a version of a half sloper.  These
conventionally use an existing tower.  The braid of the feed coax is
attached to the top of the tower, an approximate quarter wave of wire is
attached to the centre conductor and the free end of the wire tethered to a
post on the ground some distance away.  I have used one of these in a couple
of locations with great success.

In your case, where there is no tower as yet, you can hoist the coax feed up
into the trees, having attached the sloper wire in the usual way.  Cut the
outer jacket of the coax close to the ground and attach as many radials as
you can to the exposed braid.  Run the radials away in the normal fashion.
Waterproof the exposed part of the coax with silicon sealer or the
equivalent.  Adjust the length of the wire for minimum SWR (You may still
need a tuner)

The advantage of this arrangement over a conventional inverted L (in my
opinion) is that the feed point is above the ground, which raises the
impedance and improves the efficiency.  The coax braid forms a top-fed
vertical element.

Just another idea to try.

73, Greg, ZL3IX


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