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AO-40 Mode S Reception MA 249-253 - AO40RCV



Hi Doug,

Well the pass just finished for me at MA 249, which is where yesterdays test
started. Yesterday and today had a good elevetion of 45 degrees at the bird
at start of pre-perigee pass, .... today I could hardly hear anything, it
was just above the noise, ... listening MA 222 to MA 249, .... the excellent
AO40RCV sound card program was able to detect the signal but couldn't get
the sync vector. Yesterday I was using my hardware G3RUH modem, and the pass
was MA 249 to MA253, so much close yesterday. The signal yesterday was very
good and the modem decoded 13 blocks, none CRCC OK but readable. LOS on both
passes were exactly on the button for my week old keps.

I can't say what the squint was as I wasn't looking, ... I'd guess that it
was well over 80-90 degrees, ... I think what we get pre-perigee is a side
lobe, as Frank as speculated, ... therefore squint isn't meaningfull anyway,
... squint only refers to main lobe.

Anyway from 2 quick tests, I'd say that if you get a pregee pass from MA 249
onwards try it, ... the AO40RCV sound card decoder was able to detect a
signal where the G3RUH demod didn't even flicker, ... this is the first time
I've tried the program and I like it, especially as it now writes log files
in the correct AMSAT Archive format.

Tomorrow morning I have a post perigee pass, ... I'll run the hardware and
the software demods at the same time see which one wins!

Cheers
Paul, VP9MU
----- Original Message -----
From: "Doug Braun NA1DB" <na1db@yahoo.com>
To: "Paul Willmott" <pwillmott@northrock.bm>
Cc: <amsat-bb@amsat.org>
Sent: Sunday, January 21, 2001 11:19
Subject: Re: [amsat-bb] AO-40 Mode S Reception MA 249-253


> Well, right now (Sunday 1500Z) at MA 247 I hear nothing at all.
> What was the azimuth+elevation for your QTH at that time?
>
> During perigee, different stations a couple thousand miles apart
> could have very different squint angles.
>
> My QTH is Princeton, NJ and at the moment the sat's
> azimuth is 105 degrees (elevation rapidly approaching zero...)
>
> Doug
> NA1DB
>
>
> At 05:28 PM 1/20/01 , you wrote:
> >Hi All,
> >
> >Today as the bird was setting I had a go at hearing the bird before
perigee,
> >... it was on the spur of the moment, ... but I found that I found it
> >straight away at MA 249 and pretty strong, ... I quickly turned on the
> >telemetry capture program P3T just in case. The Doppler was very very
fast,
> >... too fast for the G3RUH demodulator to keep up, I had to keep turning
the
> >radio dial very quickly to keep the demod centered. Anyway I lost the
signal
> >as predicted by my week old NORAD keps, .... I caught about 13 blocks of
> >telem between MA 249 and MA 253 (LOS) (none CRCC OK but readable!), ...
to
> >my ear they sounded as good as those I hear from MA 3 onwards, .... what
> >killed any CRCC OK capture was the Doppler, .... anyway for those waiting
to
> >test your new S band converters start looking at MA 245 now, don't wait
for
> >MA 2 onwards passes. .... lets see who can be first to capture a CRCC OK
> >block BEFORE perigee, ... it is now possible!!!!!! Given that the bird
moves
> >almost 180 degrees around the planet between 253 and 3, ... this gives
all
> >of us more chances to hear the bird, test our equipment, and more
important
> >capture telemetry!
> >
> >Please post your reception attempt results to the BB to let us know! ....
> >who will be first!
> >
> >BTW the spacecraft MA indicator is reset regularly, the MA's I quote
above
> >are from the tracking program not the spacecraft!
> >
> >Cheers
> >Paul, VP9MU
>
>
> _________________________________________________________
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>

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