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AO-40 Reception



Good evening,

I had a disappointing experience listening for AO-40 this morning. 
Horizon break should have been about 1215Z here but because my antennas
are still on the ground I  have never received anything much below 10
degrees elevation.  I was attempting to compare the RHCP helix with the
LHCP one but after 15 minutes of listening on the RH antenna I had heard
nothing and the satellite was approaching 10 degrees elevation.  I
switched to the LH antenna and was able to detect the beacon right at the
noise level at 1233Z.  IT indicated phase 16, squint 47 and a range of
21K.  I listened for nearly 20 minutes but the signal never came up out
of the noise.  I was able to finally hear it with the RH antenna but the
LH antenna was always a little better.  At 1250Z the signal had faded
into the noise and I could hear it only about 50 percent of the time.  At
that point I could not hear it on the RH antenna at all.  IT indicated
phase 19 and squint 55.  Compared to early January when I last listened
the signal was very much weaker however I think the squint angle was
somewhat lower then and as I remember the range was near 10K.  I also had
tree trouble this morning.  I have a medium sized oak tree in the front
yard and there is a medium size pine tree behind that and the satellite
never did clear them. I believe the last time I listened the satellite
actually cleared the pine tree to the south.

I guess if the squint angles this morning were what I thought they were,
the results under the conditions might have been reasonable.  I have +7,
+68 entered into IT for attitude data.  Can someone tell me if that is
about right?  Are we confident that this data is correct?

I'm trying to determine for those of us who plan to use the helix antenna
will face the same polarization problems with AO-40 S band as we would
with the other birds on VHF/UHF using fixed polarization.  I guess a lot
depends on what attitude AO-40 finally takes but it seems to me that
polarization switching might be at least desirable if not necessary.

Thanks for the forum and I would appreciate any feedback.

73 de Jess - W4MVB
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