[Moon-net] Hot discussion about CP on 10GHz EME

[DF6NA Rainer]

Hi Vladimir,

my last word:
KISS - don't worry - use linear and be HAPPY !

73, Rainer

vladimir.masek at volny.cz schrieb:
> Hi all,
> allow me a small note from one who participated on the CP vs linear tests
> so deeply discussed.
> Would be happy if a piece of enthusiasm spent here was present in the
> spring time when we did the tests.
> I highly appreciate the effort of Brian, G4NNS, who initiated the tests
> with the aim to collect practical data to evaluate the recommendation
> for CP on 10 GHz approved by many of us already at 10th EME Conference
> in Prague 2002.
> To help better understand the issue, please, if interested, read the
> short review as follows (directly from my mind so sorry for some imperfections):
> Brian, G4NNS arranged several tests from Feb till April 2006 with LX1DB,
> DK0SB (2x) and IQ4DF.
> Unfortunately, regardless there were several listeners to these tests,
> only G4NNS and OK1KIR recorded usable audio files rotating RX linear
> polarization in 10 deg steps.
> All recordings can be found on G4NNS web page and of OK1KIR on [1]http://www.qsl.net/ok1vao/10GHz_pol_test/
> as well.
> Luis, CT1DMK made some audio processing and published it among description
> of CP feed designs for 10GHz already in DUBUS 2/2006.
> If anyone can continue DSP analysis of the rest of recordings, it would
> be great help.
> There are available recordings of signals from TX sides:
> DK0SB 20 m dish BW3 ≈ 0.1° and 800/700 W of rf pwr (continuous signal
> LP)
> IQ4DF 7 m dish BW3 ≈ 0.3° and 200 W of rf pwr (only cq and dots transmitted
> with LP)
> LX1DB 10 m dish BW3 ≈ 0.2° and 60W (cq transmitted with CP and LP)
> downloaded at RX sides:
> G4NNS 3.7 m dish BW3 ≈ 0.55° (LX1DB, DK0SB, IQ4DF)
> OK1KIR 4.5 m dish BW3 ≈ 0.45° (DK0SB, IQ4DF)
> Audio recordings are available for each 10 deg step when rotating linear
> polarization of RX feed by +/-90 deg.
> Reflected signals were received with BW of cca 0.5deg angle (i.e. full
> “Moon” in picture).
> I did some (time consuming) “hand” processing which gave me the maximum
> avg ratio co- vs cross-polarisation in the range 10…12 dB at DK0SB
> signal (accuracy of pointing was better than hundreds of deg !) and
> 8…10 dB at IQ4DF signal.
> This clearly indicates that linear polarization very well sustains after
> reflection from the Moon, especially when its “plain” central area
> has been illuminated.
> Anyone with better DSP SW could help with more complex outcome similar
> to what Luis,CT1DMK, presented yesterday on W7QX web page and is available
> on Brian’s web as well.
> Nevertheless what is missing to finalize the story is a test between
> two medium size dishes of approx. 4m with BW of 0.5 deg and rf power
> of at least 40W on TX side with TX, which can survive continuous key-down
> and NF<1 dB to get reasonable s+n/n ratio on RX side. Stations with
> SSPA can be in favor, hi.
> I hope that no one believes that the polarization plane will completely
> disappear just for the reason that antenna beam will be extended from
> 0.3 deg to 0.5 deg to hit the whole Moon !
> If that is true, and I believe that it is, there is only a question if
> we all are able to agree a common proposal for new designs and/or newcomers
> to 10G EME to ease the new projects or we want to stay glued to existing
> positions and discussions and have futher both polarization in use.
> I understood there is a lot of different arguments. But I remember similar
> situation some time ago at 23 cm and 13cm as well before the septum
> feed came in.
> At the end let me drop a provocative EME jingle:
> As higher the frequency,
> as bigger the dish,
> as more CP is wanted
> for another party small dish.
> Have a fun on EME and GL on new 10G projects !
> “Viel spass” !
> Vladimir, OK1DAK (OK1KIR)
> References
> 1. http://www.qsl.net/ok1vao/10GHz_pol_test/
> 
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