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Re: AO-40 S band telemetry / reception report

Hi Roger,

Interesting observation about centre frequency, ... its around the same as
measured by Viktor, ... and you are both using 970 + 2.4 module, ....

... I'm using a 970 + SSB UEK-2000S converter, and I measured centre
frequency to be (yesterday and today) to be 2401.317 to 2401.318. That was
working back from radio dial (controlled by G3RUH MkII demod using up/down
key clicks), using range-rate of the time, to calculate what beacon freq
would generate that amount of Doppler. You can't just add/subtract RIT, you
have to add/subtract RIT without Doppler, a 3kHz RIT is not a 3kHz
difference in beacon freq!

Interestingly I received info today that the S2 MB beacon was measured
pre-flight in Kourou to be 2401.318MHz, ....

I didn't get a chance to calculate Doppler on todays pass, but plugging in
the 2401.31724 got me within a few hundred Hz at AOS at MA3, ... so its a
pretty good number for my RX + Converter, ... we just need some more
observations now.

Thanks for the telem you added 6 new A blocks to the collection, ... in
total we got 25 this pass.

Paul, VP9MU

----- Original Message -----
From: "Roger Rehr W3SZ" <rrehr@epix.net>
To: <amsat-bb@AMSAT.Org>
Sent: Sunday, December 31, 2000 10:03
Subject: [amsat-bb] AO-40 S band telemetry / reception report

> Hello all!
> I was able to hear AO-40 today and post this to share my observations.
> My station is in FN20ah, Reading, PA. (40.3316N, 75.9870W).
> I am using 2 Directive Systems Blowtorch loop yagis in a 1 x 2 array.
> are cut for 2304 and are really for terrestrial weak signal work.  The
> rotors are M2 MT-3000 and RCP2800.
> I have an SSB Electronics preamp on the mast near the power divider; also
> centered on 2304.
> I run 100 feet of LMR-600 UF to the house where I have 50 feet of 7/8 inch
> hardline bringing the signal to the shack.  Then I have 10 more feet of
> LMR-600 to the rig.  (Its a good thing the SSB Preamp has lots of gain!)
> The rig is an ICOM IC-970H with the ICOM 2400MHz module installed.
> Frequency control was via Wisp, using a homebrew visual basic program to
> pick off the doppler info from Wisp's DDE output,to control the 970H via
> CT-17 system thru COM5. (Keps Set #18)
> I used a center frequency of 2401.317.240 and found that I had to use
> 3.6-4.6 KHz of RIT. This would suggest that the center freq is on the
> of 2401.321-2401.322 MHz, if the ICOM is on frequency.  I suspect that it
> is, as UO-11 center frequency was right on at 2401.500 MHz for me today.
> The TNC was an AEA DSP-2232 with the new AO-40 400 B DSP modem loaded.
> Results:
> UO-11 is Q5 copy here but S meter moves little if at all with it.
> AO-40 AOS here was 940 UTC today. Initial range was 7622.6 km, phase 4.2,
> squint 41.  Squint minimized at 28 at 0950 UTC when distance was 9462 km.
> (I used Nova which I believe gives the correct squint with alon 2 and alat
> 260).
> Initially AO-40 was peaking at S8 (meter is at 0 with no signal), with a a
> good bit of fade.  The DSP-2232 was able to copy telemetry out to 1120 UTC
> at a range of 29000 km, but I got no good CRC after 951 UTC, just after
> optimal squint time noted above.  AT 1120, beyond which the DSP-2232 lost
> lock, the squint was 63.7 degrees.
> Once the bird was a ways out (between 35 and 40K km) I was able to check
> pointing of my antenna as I lost the signal with just a few (less than 5)
> degrees of mispointing.  The antenna was 'right on' with Nova doing the
> tracking.
> At 40 K I essentially lost the bird in the noise, not hearing it at all,
> although I could still see the traces at times using AO40r, which I also
> found helpful for getting the signal frequency centered at first.
> I am sending my telemetry files (mostly bad crc) to the repository.
> Thanks to all who helped me with this...I hope this helps someone else who
> is like me just getting started at S band satellite work.
> PS I used the loop array because it is already up there on the tower.  I
> also have one of the barbeque grill dishes, but with stock feed it won't
> handle the 50 watts I use for terrestrial work on 2304, so it is currently
> not being used.  I may or may not end up putting it up for AO-40,
> on how this setup works.
> 73,
> Roger Rehr
> W3SZ ex AA3QK, WA3JYM  FN20ah
> 2 Merrymount Road
> Reading, PA  19609-1718
> http://www.epix.net/~rrehr/w3sz.htm
> ----
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