[amsat-bb] Polarisation Switch

Simon Brown simon at sdr-radio.com
Thu Dec 25 16:26:30 UTC 2014

Hi Wouter,


Many thanks and also thanks to Ken. I’m currently sorting out the station on the FO-29 passes, mainly debugging the software.


FWIW I am using a NetSDR + Down-converter (from RFspace) on RX and a TS-2000 on TX. Using the SDR on RX is so much better than flying blind IMO J . I need to get some cables ordered to I can easily switch between 2m and 70cms, when I do this I’ll start with AO-73.


Simon Brown G4ELI


From: Wouter Weggelaar [mailto:wouterweg at gmail.com] 
Sent: 25 December 2014 11:11
To: Simon Brown
Subject: Re: [amsat-bb] Polarisation Switch


Hi Simon,

This depends on the satellite and its attitude.

For instance, Delfi-C3 carries circular antennas (canted turnstile) and is free tumbling. So you would need to switch polarisation as the satellite spins. FUNcube has linear antennas and also is free tumbling, so if you listen to it with a circular antenna there is no need to switch.

Note the following:

Circular in the wrong sense gives 20dB of loss (listening to LHCP signals with an RHCP antenna and vice versa)

Circular to linear gives 3dB loss (listening with a horizontal / vertical / diagonal antenna to a circular spacecraft or vice versa)

Now if the satellite is oriented or spin stabalised towards the earth, the polarisation will be known, and matching the apporopriate polarisation on the ground gives you the best signals.

Wouter  PA3WEG


On Thu, Dec 25, 2014 at 8:17 AM, Simon Brown <simon at sdr-radio.com> wrote:

Hi All,

Is there a logical way to know which is the optimal polarization (left,
right) for a LEO?

Simon Brown G4ELI

Sent via AMSAT-BB at amsat.org. AMSAT-NA makes this open forum available
to all interested persons worldwide without requiring membership. Opinions expressed
are solely those of the author, and do not reflect the official views of AMSAT-NA.
Not an AMSAT-NA member? Join now to support the amateur satellite program!
Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb

More information about the AMSAT-BB mailing list