> On Apr 30, 2006, at 5:28 AM, <email@example.com>
> <firstname.lastname@example.org> 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
> 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.
> Bob Nielsen, N7XY
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