[amsat-bb] Re: WX-proofing a Helix Feed

["Bill Acito" <w1pa@xxxxxxxxxxx>]

I little searching in Google...

Howard offers some practical experience on this here.  Thanks!

http://www.g6lvb.com/radcomclarifications.htm


----- Original Message -----
From: "Bill Acito" <w1pa@hotmail.com>
To: <amsat-bb@amsat.org>
Sent: Monday, October 21, 2002 1:56 PM
Subject: WX-proofing a Helix Feed


> Thanks to all of you who answered my questions about flexible coax;
now
> I have another.
>
> In my continuing saga to Elmer another ham getting a satellite station
> up, I was looking for suggestions on how to weather-proof a homebrew
> helix feed for an offset dish going on a tower installation in New
> England climate and weather conditions.
>
> We've talked before about white PVC, but I wanted to get practical
> experience, especially since I have read that the PVC might detune the
> helix slightly. The DEM helix and some of the commercially available
> helix feeds are in PVC...  how much should I scale the dimensions to
> account for the detuning? I have no SWR, return loss, or analysis
> equipment that goes over 500MHz.
>
> I asked about Tupperware before, and most commented that it will not
be
> UV resistance and crumble in a year or so.
>
> I know many of you have also gone without any additional coverage over
> the feed, and I'm wondering what "hardened" hardware you have used in
> the construction (materials, paints, coatings, sealers -- diameter of
> the tubing, matching plate materials). I assume the same question
would
> pertain to patch feeds, but everything I have read says I should be
> using a helix for an offset dish and a f/d greater than .5
>
> I'm still running portable, so my
copper-coil-over-electrical-box-cover
> feed works fine...
>
> http://webpages.charter.net/acito/dishandboom.jpg
>
> what are you guys with dishes on towers in northern latitudes doing so
I
> can steer this ham right (especially, since I have to build the feed)?
>
> Bill
> w1pa
>
>

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