[amsat-bb] AMSAT-BB Digest, Vol 10, Issue 301

Burns Fisher burns at fisher.cc
Fri Oct 9 17:17:38 UTC 2015

One thing that bears repeating, or perhaps has not been said terribly
explicitly.  The issue with decoding low speed data via the audio out of a
"regular radio" is the LOW frequencies not the high.  You need to be sure
that the 9600 baud output does not have a low pass filter even if it can
pass light on the high end.  We need down to only a few 10s of Hz.  Some
radios work one way, some the other.  Nearly all will filter out low
frequencies on the normal audio output.  Check your manual.  I have a
TS2000, but I don't remember the specs on 9600 baud out.  I have used SDR
for my testing.

And another comment for another person re HDSDR and FoxTLM:  I have a very
slow CPU in my shack.  It can't deal with FoxTLM running its own SDR at
all.  It *can* deal with HDSDR piping audio via Virtual Audio Cable to
FoxTLM running just in audio mode.

73 from LAX, heading back to my QTH after the launch,

Burns W2BFJ
Proud to say: Member of the Fox-1 Flight Software group

---------- Forwarded message ----------
From: Brad Schumacher <brad.schumacher66 at gmail.com>
To: <amsat-bb at amsat.org>
Date: Thu, 8 Oct 2015 22:50:09 -0700
Subject: [amsat-bb] Fox-1A Telemetry Results using TS-2000
I've been reading this list for a while, decided it's about time I posted
something.  I attempted to decode the Fox-1A telemetry on 2 passes over
Arizona today (approx. 0130 and 0300 UTC) using my Kenwood TS-2000 without
success.  I configured it for 9600 packet operation, monitored the audio out
of ACC2 connector and could see over 20 Khz of audio bandwidth using
software based audio spectrum analyzer.  Audio response looked good from 0
to 20 KHz so I thought I would be good to go.  Nope.  I fed audio into 2
different sound card devices - one being the RigBlastger Advantage set to 48
KHz sample rate and the other audio device being my Laptop's built in sound
card mic input set to 48K and 96K on different attempts.  Audio levels were
adjusted so as not to be excessive and sounded clean when played back
through the speaker.

When attempting to decode, I could see a very nice eye pattern in the
telemetry decode software but the data square waves were pointy looking as
if some high frequency filtering was being applied to them.  I' not
conclusively saying the TS-2000 won't work but I did everything right and
tested as thoroughly as possible prior to the actual satellite passes with
no success.  I'll try again and see if I missed something and report back.

What DID work for me was decoding the signal via SDR.  In this case It was
an RTL-SDR dongle in direct sampling mode connected to the 10.695 Mhz IF of
the TS-2000.  HDSDR was used with output bandwidth set to 96 Khz.  Audio was
piped to Fox telemetry decoder via VB Virtual Audio Cable software.

Brad, KG7NXH

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