[Moon-net] 432 conditions.

peter blair g3ltf at btinternet.com
Sun Nov 16 12:43:59 CET 2008


 Conditions on the first pass on 432 here were what I call good , polarisation was sharply defined, but the fading was very long with shortish strong  peaks sometimes as much as 40 seconds apart and long periods of weaker signal. It was not a polarisation effect because I was able to check this with the fully rotatable feed.  In the fades the signal remained low despite rotating the feed. This is a similar effect to that which was observed last year ( 2007) and in October 2008  but then the effect was only at moonrise plus a few hours. This time it seemed to persist for much longer, up to 6 hours.  
I dont recall encountering this before  and years ago there was more 432 activity so one would expect to have seen it more easily.
By contrast on the second pass here, from moonrise on, signals were definitely  weaker... because the polarisation was badly spread with little change over large rotation angles... The same fading effect was still present but much less marked. 
Bill W4TJ and Doug VK3UM have both commented on " difficult / unusual" conditions.  Does anyone have any rational explanations for this? 

As I see it, there are three effects,  Faraday rotation, Absorbtion and Libration, all with different periodicity. I think  I can largely eliminate polarisation. Can it be that the libration and absorbtion rates of change are similar at this period of the solar cycle for some reason and so we are seeing the interactive effect of two slowly changing periods?
I gather we are in the quietest period of sun activity  since before amateur EME began, could this be significant? 

73 Peter G3LTF 
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