[amsat-bb] Polarisation Switch

Wouter Weggelaar wouterweg at gmail.com
Thu Dec 25 11:11:28 UTC 2014

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
> http://v2.sdr-radio.com
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