[amsat-bb] Re: AO-51 S band fades

i8cvs domenico.i8cvs at tin.it
Sun May 9 23:22:12 PDT 2010

----- Original Message -----
From: "Bob- W7LRD" <w7lrd at comcast.net>
To: <amsat-bb at amsat.org>
Sent: Monday, May 10, 2010 1:13 AM
Subject: [amsat-bb] AO-51 S band fades
> Anyon have an idea why we get such deep fades on AO-51 S downlink? Did
work K8YSE & KC9ELU between the fades. Is there something we can do at the
rx end? Switch polarity, bigger dish??
> 73 Bob W7LRD

Hi Bob W7LRD

The AO-51 S band antenna is linear but the satellite is slowly thumbling so
that the antenna can appear to you as oriented  from any possible position
and with any possible squint.

Switching polarity from RHCP to LHCP or from linear vertical to linear
horizontal is complicated in S band and make very small.

Probably it is better to use a linear feed as a dipole in the focal point
be able to rotate it very fast by 360° in 10 seconds or less using a small
DC motor with a gear box as many EME operators uses to compensate
the polarization change due to Faraday rotation.

A bigger dish complicates your life for very small because the satellite
becomes more and more critical.

73" de

i8CVS Domenico

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