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Re: [TowerTalk] superflex for rotor loop?

To: <towertalk@contesting.com>
Subject: Re: [TowerTalk] superflex for rotor loop?
From: "K8RI on Tower talk" <k8ri-tower@charter.net>
Date: Sun, 30 Apr 2006 13:29:28 -0400
List-post: <mailto:towertalk@contesting.com>


>
> On Apr 30, 2006, at 5:28 AM, <radio_k4rv@peoplepc.com>
> <radio_k4rv@peoplepc.com> wrote:
>
>> Is Andrew 1/2 inch superflex continuously flexible enough to be
>> suitable for
>> use as a rotor loop?
>
>
> No.  Use coax with a braided shield and stranded center conductor
> instead.  It will flex fine for a while, but eventually the
> corrugated copper outer conductor and/or the solid center conductor
> will fail.

However a well designed rotator loop will minimize the flexing.  I have mine 
set up to form a fairly large diameter (roughly 18"), two-turn coil that 
lays on the tower top plate.  A 360 degree rotation only causes the coil to 
change size a bit.

It also gives a bit of a fudge factor if the mast slips in the rotator.

Roger Halstead (K8RI and ARRL 40 year Life Member)
N833R - World's oldest Debonair CD-2
www.rogerhalstead.com

>

> About 30 years ago I was working on an application for feeding an
> antenna on a gimballed platform at Hughes Aircraft and we were
> concerned about the effects of flexing the coax.  We did a life test
> where we continuously flexed the cable and measured return loss,
> looking for changes.  We first tried RG-142B, which had a copperweld
> center conductor.  After several hours it failed and the autopsy
> showed that the copperweld had broken into several small pieces in
> the region being flexed.  We tested again with RG-400, which is
> similar except that it has a stranded copper center conductor and
> that was still going fine after several hundred hours of flexing.
>
> 73,
> Bob Nielsen, N7XY
>
>
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