[amsat-bb] Re: ARISSat TLM test WAV file pointer

Mon Aug 8 16:27:04 PDT 2011

Hi Henk and David,

If you want to try out some larger WAV recordings of the BPSK-1000 beacon
you can get some from the oz7sat system.
Start at
http://www.amsat.dk/oz7sat/sched.php?gs=oz1kte&sat=ARISSAT-1&status=All then
select a particular pass and download the recording.  The files are about 65
MB each. Our system starts recording about 90 seconds before AOS and
continues to a bit after LOS as calculated for our station in Copenhagen.

These files are received using a USRP fitted with a WBX module. A piece of
GNU radio code splits the 256 KHz wide stream from the USRP into separate
streams for the BPSK beacon, the linear transponder area and the FM channel.
The GNU radio code also performs doppler adjustment of the whole signal.
The BPSK stream is saved to disk and in parallel fed through Phil Karn's
demod program to extract the telemetry frames.
The telemetry viewer is currently only capable of showing the first few
fields of the packets.

The telemetry decoder seems to be a bit sensitive to sudden jumps in
frequency. We have tried manual tracking with 100 Hz steps but that did not
work very well. Using 50 Hz steps was much better. Our system is now
adjusting the doppler offset once a second which gives a good result.

Regards
Scott, OZ2ABA

-----Original Message-----
From: amsat-bb-bounces at amsat.org [mailto:amsat-bb-bounces at amsat.org] On
Behalf Of PA3GUO
Sent: 8. august 2011 19:06
To: g0mrf at aol.com; amsat-bb at amsat.org
Subject: [amsat-bb] ARISSat TLM test WAV file pointer

David

https://svn.sarpeidon.net/viewvc/suitsat2/ground_station_software/ARISSatTLM
/install-staging/Sample_ARISSat_Recording1.WAV?revision=3003

this is a test WAV file, and my install of ARISSatTLM is able to decode
this.
9.6MB, 1:45 minutes.

would be useful to place this on www.arissattlm.org

Henk, PA3GUO

Hi Henk.

I've had some issues with decoding BPSK too.  Worked fine on the first day,
then unable to decode anything.
Eventually I reloaded the software and played a wav file through the system.
Finally it began decoding again. I don't really know what the problem was.
It still will not send tlm via the internet and I can't get sound
out...Hence the wav files.

Problem is the wav file I have is large so I cant send it to you to try.
Perhaps some one has 30 seconds worth that does decode, then we can use that
as a standard to check our systems.

I've been tracking doppler by hand. Seems to work OK but it's very important
to keep the CW in the 'blue' window.
I would think jumps would not be good. Perhaps frequent doppler updates.  -
So very small jumps.

I also heard HB9 last night on the transponder, but in low power mode (45
sec)that is difficult. - I'll wait for some daylight passes.

Good luck

David G0MRF

-----Original Message-----
From: PA3GUO <pa3guo at amsat.org>
To: amsat-bb <amsat-bb at amsat.org>
Sent: Mon, 8 Aug 2011 10:41
Subject: [amsat-bb] ARISSat TLM decoding using FCD Just sharing the results
of my recordings of last night:
(using the FCD + HDSDR)

-          FM voice works fine

-          Xponder works fine (HB9AOB was very clear)

-          CW decoding works fine (the Tuning indicator locks on the CW
bump)

-          BPSK decoding did not work (I hear & see the signal, but no
decode)

Is the BPSK decoding very sensitive to doppler / freq hops ?

Henk, PA3GUO

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