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Re: AO-40 performances



Howard,

While looking at several different things in the tlm something finally
clicked about your question.  One difference is that at 27/2300z the
transponder was on and at 28/2300z the transponder was off.  I'm starting to
think you were seeing noise coming from the U/L receivers.

Last week I was testing a new 36 inch offset fed dish when I noticed the
noise floor was about 6-7 db above what I expected.  My first thought was
that it was ground noise due to a bad feed pattern or something else related
to my setup.  Then I noticed that the noise peaked at the same az/el as the
beacon.  Next I tuned from just above to just below the u/s passband and
found that the increased noise was only within the frequency range of the
transponder.  This was observed with the squint at about 5 degrees and a
range of 58k km.  I'm using a Millicom d/c which is quoted as having a 3 db
NF.  If that NF is accurate, I would have expected the transponder noise
floor to be some 6 db below my local noise floor at that range.

Now that the MB is staying one during the RUDAK period we could make s/n
measurements just before and after the u-rx is switched in and out of the
matrix at each end of the RUDAK period.

Lee-KU4OS

----- Original Message -----
 From: "Howard Long" <howard@howardlong.com>
 To: <amsat-bb@AMSAT.Org>
 Sent: Wednesday, August 29, 2001 10:23 AM
 Subject: [amsat-bb] AO-40 performances


 > Folks,
 >
 > I've been wondering for sometime whether AO-40 is as good now as it was
 back
 > in May. On Monday and Tuesday nights I took some readings on the same
 > standard AO-40 antenna (WIMO 30 turn) I've been using since February.
 >
 > Date      Time    MA  Range   Squint    S2 S/N
 > 27 August 2300Z   85  56,600   4.7 deg   10dB
 > 28 August 2300Z  150  60,000  15.5 deg   24dB
 >
 > My ALON/ALAT are set at 350/2 and I'm using NOVA & InstantTrack to
 predict.
 >
 > So any comments on why I'm getting seemingly bad signals on Monday with a
 > squint of 4.7 degrees but on Tuesday at 15.5 degree squint things are
 pretty
 > loud? These are pretty indicative of some subjective observations I've
 been
 > having for a while.
 >
 > 73 Howard G6LVB
 >
 > ----
 > Via the amsat-bb mailing list at AMSAT.ORG courtesy of AMSAT-NA.
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