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Re: ao40 today




I think the +/1 200 Hz drift might be due to the rotation of the spacecraft.
A few weeks ago, I recall someone mentioning a similar effect, and the
answer, as I recall, was that the 2.4 Ghz antenna was offset near the edge
of the craft. At large squints, and as the structure rotated, the antenna
would appear to move away, then towards you. This would cause the doppler
shift "flutter".  Sounds like a good way to measure spin rate of the
spacecraft.

73, Ken, W7KKE

----- Original Message -----
From: "Douglas Braun & Nadia Papakonstantinou" <dougnad@BellAtlantic.net>
To: "Bill Hurlock" <bill@hurlock.net>
Cc: <amsat-bb@AMSAT.Org>
Sent: Sunday, December 31, 2000 9:05 AM
Subject: Re: [amsat-bb] ao40 today


> Early this morning (Sunday) I was getting a strong signal. (Oddly,
> yesterday morning I could barely hear it, even right after AOS.)
>
> I noticed a short-term random drift of about +/- 200 Hz, over a
> period of roughly 10 seconds.  This made it hard to keep my demodulator
> locked to the signal.  I know it wasn't Doppler-related, since my
> tracking software tunes the radio in 1Hz increments every couple of
> seconds.  It might have been due to drafts of cold air getting to my
> converter's LO crystal. I will try insulating the crystal for next time.
>
> Has anyone else noticed a random frequency drift like I described above?
>
> Doug
> NA1DB
>
>
> At 02:00 PM 12/30/00 , you wrote:
> >I copied the telm from ao40 but there were no good CRC blocks. I heard
> >it S7-9
> >from AOS of MA 16.5 thur MA 37.6. Signal freq seemed to drift up and
> >down over
> >the period. I could see diffinate spin modulation on the signal uing
> >FFTdsp.
> >Freq started out at 2401.305 and ended at 2401.308. Signal showed heavy
> >flutter.
> >Using Myer's dish, Drake (moded with latest mod's), FT736R IF, Nova
> >Tracking.
> >
> >Bill WA2TQI  EM78qe
>
> ----
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