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Re: Helix Feed for a Dish



When I was using AO-13 mode S, I starting with a helical feed and no cup.
Adding the cup seemed to increase the SNR a few dB and cut down on
interference from my neighbor's microwave oven. I didn't make any
measurements, but it sounded better.

73,

John
KD6OZH

----- Original Message -----
From: "Frederick M. Spinner" <fspinner@hotmail.com>
To: <amsat-bb@AMSAT.Org>
Sent: Friday, 01 June 2001 19:12 UTC
Subject: Re: [amsat-bb] Helix Feed for a Dish


>
> >I have a DSS dish that I hope to use a G3RUH design helix (about 4
> >turns?), and a Hammond aluminum box as the cup reflector.
>
> Has anyone figured out if the "cup reflector" cavity makes any difference
at
> all when used as a dish feed?  Obviously a standalone helix is does (more
> gain) but as a dish feed, pattern is more important than gain.  But then
> again, a choke ring on a Chapparrel type feed decreases sidelobes, so
there
> is a strong probability that there will be a difference.
>
> Fred W0FMS
>
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