[amsat-bb] Polarisation Switch

[Alan]

Hi Simon,

Yes, having DSP is the way to go.  I have a Flex VU-5K which gives you all the functions, and eliminates the hassle of switching antennas.  To bad it was discontinued so quickly.  Of course, it is a bit pricier than a FCD with a conventional TX rig.  :)

73s,

Alan
WA4SCA


<-----Original Message-----
<From: amsat-bb-bounces at amsat.org [mailto:amsat-bb-bounces at amsat.org] On Behalf Of Simon Brown
<Sent: Thursday, December 25, 2014 10:27 AM
<To: 'Wouter Weggelaar'
<Cc: 'AMSAT BB'
<Subject: Re: [amsat-bb] Polarisation Switch
<
<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
<http://v2.sdr-radio.com
<
<
<
<From: Wouter Weggelaar [mailto:wouterweg at gmail.com]
<Sent: 25 December 2014 11:11
<To: Simon Brown
<Cc: AMSAT BB
<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
<http://v2.sdr-radio.com
<
<
<
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<_______________________________________________
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