----- Original Message ----- From: "Bob- W7LRD" w7lrd@comcast.net To: amsat-bb@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 and 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 traking becomes more and more critical.

73" de

i8CVS Domenico