[amsat-bb] Re: Antenna Polarization Question

i8cvs domenico.i8cvs at tin.it
Sat Sep 15 16:18:57 PDT 2012

----- Original Message ----- 
From: "Thomas Doyle" <tomdoyle1948 at gmail.com>
To: "i8cvs" <domenico.i8cvs at tin.it>
Cc: "Amsat - BBs" <amsat-bb at amsat.org>
Sent: Saturday, September 15, 2012 10:34 PM
Subject: Re: [amsat-bb] Antenna Polarization Question

> Domenico,
> Thanks for the reply. I am slowly building my sat station back to what
> it was back in the day when I had a pair of KLM antennas with
> polarization switching. I have recently added a switchable
> polarization 70 cm antenna to my current station and am amazed at how
> often during an FO-29 pass it is necessary to change polarization. My
> memory is not what it should be but I do not remember as much
> switching being necessary when using AO-10 era sats. Perhaps they were
> more stable or the pass was so long that it did not seem like it
> required as much switching.
< snip >
> tnx & 73 W9KE Tom Doyle
Hi Tom, W9KE

Using AO-10 and in general HEO satellites like AO-13 and AO40
switching polarization was less necessary than using LEO satellites 
because most of the time the satellite antennas were oriented toward
the earth with a small squint angle so that the polarization changed
very slowly mostly due only to the Faraday polarization rotation
when the wave passed through the ionosphere.

BTW the above HEO satellites were spinning over the Z axis 
generating the so called "spin modulation" wich sounded like

Only the AO40 downlink at 2401 MHz was less affected by the
polarization rotation due to Faraday effect and less affected by 
the spin modulation.

Hope that some time in the future the HEO satellite P3E will
be placed in orbit !

73" de 

i8CVS Domenico

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