[amsat-bb] Leveraging Satnogs recordings ( was: request detailed system diagram for remoting a satellite station)

[Douglas Quagliana]

On Fri, Jul 17, 2020 at 4:49 PM Peter Goodhall (2M0SQL) via AMSAT-BB <
amsat-bb at amsat.org> wrote:

> Sadly Satnogs isn't suitable for the job being it's for telemetry only,
> also I don't believe it forwards telemetry to AMSAT-NA or AMSAT-UK so radio
> amateurs would be better off with a different solution.
>

Friends,

Satnogs is an incredible and incredibly underutilized resource for AMSAT.
It doesn't automatically forward telemetry, but you can go to the
appropriate Satnogs site, filter on the satellite you want and download the
audio recording of the pass (or passes) that you want. Then
lather-rinse-repeat for as many passes as you want. I would never have been
able to create as many recordings myself at my home QTH as I can get by
downloading them from Satnogs.  You can get recordings from anywhere on the
planet where there was a ground station that made a recording. (If you're
fully onboard you could even schedule somebody else to make a recording for
you on a particular date/time in the future. Think about that.)

A while back I downloaded several months worth of old Falconsat-3 audio
recordings so that I could run the recordings through my own 9600 DSP
demodulator and see if I could recover any data from the recordings, and
improve the demodulator as much as possible. I wrote some scripts to
convert and filter each ogg recording and then run them all through my
demodulator.  This whole scheme actually worked too well, as I now have
more than enough recordings to keep me busy for a long long time because it
takes my old computer DAYS to process through ALL of those recordings
[footnote 1] and to decide if the latest tweak was an improvement or not.
(Think about your last visit to the eye doctor where you watch the eye
chart through the phoropter [footnote 2] while the eye doctor makes
adjustments to the lenses and asks you if this one is now "Better? Or
worse?" -- well, this is almost the same thing but it takes three days to
find out the answer for each change. But, I digress...)

So far, of the recordings that I downloaded, the most extreme pass is

https://network.satnogs.org/observations/180707/

the audio recording is eighteen megabytes and is online at

https://ia902808.us.archive.org/7/items/satnogs-observation-180707/satnogs_180707_2018-07-12T00-08-11.ogg

The satnogs webpage for this pass shows 644 valid 9600 baud AX.25 packets
this recording so you know it is a good pass with plenty of frames in it.
By throwing everything I can think of at this recording, I can now get over
1000 good frames out of it. Oh, and, hey, if anybody else tries this
recording against their own demodulator, then whatever results you get
please send them to me so I can look for any valid frames I am missing.
And the advantage of the satnogs recordings is that you can keep tweaking
your software iteratively by running the recordings against the "new"
demodulator again, and again, and again, and compare the results.  You
could never achieve this or iterate this many times with live satellite
passes.

73,
Douglas KA2UPW/5
[1] If the whole process doesn't get interrupted... Actually, this says
more about my old slow computer than it says about the speed of the
demodulator.
[2] If you get your eyes checked then you know this device. You just might
not know the name for it.  Consider "phoropter" to be today's new
word-of-the-day.  See https://en.wikipedia.org/wiki/Phoropter