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AO-40 Reception



Good Morning To All,

I inadvertently performed a reception polarization test on the 2.4 ghz
downlink this morning.  Yesterday I put up a Trans System converter along
side a G0MRF modified Drake converter so I could compare the two
converters.  This morning after I was unable to initially hear the signal
with the Trans System converter I discovered that I had put up a LHCP
helix instead of the RHCP I intended to put up.  After discovering that I
carefully listened and I could just hear the signal in the noise at a
pointing angle of near zero with the LHCP.  As the pointing angle
increased the signal from the LHCP antenna began to increase.  At an
angle of somewhere between 25 and 30 degrees the LHCP antenna became
better (although the overall signal strength was down).  By 40 degrees I
could no longer hear the signal on the RHCP antenna.  The signal was
there on the LHCP but it was very weak.  By 45 degrees I could no longer
hear the signal at all.

Even though the test was accidental it was a test I intended to perform
at some time and I think I satisfied my curiosity.  My conclusion is that
although the LHCP antenna is better at higher squint angles (as expected)
it is of little value since the overall signal strength decreases below a
usable level (at least with my setup) at those angles.

Downlink signals were weak for me this morning and they never did change
very much.  It appeared that the increase squint angle just about offset
the reduced range during my best time between 1000Z and 1100z.  I now
consider my 21 turn helix and the Drake converter marginal at best
instead of promising.  Most of the stations I work hear me better than I
hear me and most of them are using dish antennas.  I still have some
tests to make (including the side by side Trans System/Drake test) but I
can already tell I need a dish!

73 de Jess - W4MVB
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