[amsat-bb] Re: Antenna Polarization Question

Thomas Doyle tomdoyle1948 at gmail.com
Sat Sep 15 13:34:53 PDT 2012


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.

 "In 1911, Albert Abraham Michelson discovered that light reflected
from the golden scarab beetle Chrysina resplendens is preferentially
left-handed." After reading this I wondered if it is possible to
create a reflector for RF that would do something similar to what this
tiny insect does without even trying. When I asked how to change the
polarization sense of a lindenblad antenna I was going to build the
author of the article told me that it was not necessary to switch it
because there were so many reflections it would not matter. Perhaps a
controlled reflective surface would work.

tnx & 73 W9KE Tom Doyle

On Sat, Sep 15, 2012 at 3:00 PM, i8cvs <domenico.i8cvs at tin.it> wrote:
> ----- Original Message -----
> From: "Thomas Doyle" <tomdoyle1948 at gmail.com>
> To: <amsat-bb at amsat.org>
> Sent: Saturday, September 15, 2012 8:47 PM
> Subject: [amsat-bb] Antenna Polarization Question
>> I was listening to a couple of guys on FO-29 having a nice chat about
>> satellite antenna polarization. They were trying to figure out what
>> type of polarization FO-29 used. They looked at the picture of FO-29
>> on the AMSAT web site and decided that it was not circular. Someone
>> told me that it was circular so I started looking for information.
>> Found this page by WD0E which is quite nice.
>> http://www.amsat.org/amsat-new/information/faqs/pswitch.php
>> Is there a more current page that contains this type of information.
>> tnx W9KE Tom Doyle
> Hi Tom, W9KE
> For the antenna polarization of FO-29 please read belove:
> -------------------------------------------------------
> FROM AMSAT HQ SILVER SPRING, MD, September 10, 2012
> BID: $WSR-254.S1
> FO-29 JAS-2
> Catalog number: 24278
> Launch Date: August 17, 1996
> Mode and Antenna Polarization:
> --------------------------------------------------------
> i8CVS Note:
> Following my experience on FO-29 I can add the information
> belowe:
> FO-29 is RHCP circularly polarized  both in uplink and downlink
> and has a fixed sense both up and down, but because of its orbit
> geometry and motion, continuously good signals through it for an
> entire pass can only maintained if the antennas ground station sense
> is switched, RHCP to LHCP and vice versa in 70 cm and 2 meters
> usually several times and on both uplink and downlink and so
> polarization switching relays on board of both up and down antennas
> are recommended.
> Read please my articles about polarization switching published on
> the AMSAT-Journal March/April 2007 and May/June 2007
> 73" de
> i8CVS Domenico


Sent from my computer.

tom ...

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