[amsat-bb] LilacSat-1 and Codec2

Tom Schuessler tjschuessler at verizon.net
Sun May 28 03:25:40 UTC 2017

OK I'm NOT a Linux guy.  Let's see if we can do LilacSat-1 for the rest of

What I have been able to figure out is that Codec2 is a digital voice codec
that creates audio speech out of some input data.  If I read things right,
LilacSat-1's concept here is to take analog FM (PL tone of 67HZ to open it's
squelch), input and digitize the audio and then encode what it hears to
digital data using the Codec2 process.  That data is transmitted on a 9600
data stream BPSK decoded by an application.  I think that is a good basic
explanation of the system.  A unique concept.

Now back to not being a Linux person.  I see the posts on the BB dealing
with folks using GNU radio to decode the data.  GNU Radio which is a Linux
Digital voice program apparently can be ported to Windows, but the install
process is very touchy feely.  My looking at pages about Codec2 I get
references to the "FreeDV" program.  I found they do have a Windows
installer for FreeDV.  Is that the accepted program for this purpose using
CODEC2?  After installing the FreeDV program, I see that there are different
flavors of the Codec it uses, but only some of them seem to match what is
noted as flavors on the Codec2 development page.  Which actual flavor is the
LilacSat-1 system using?

I intend to give this a listen sometime this long weekend to see if I can
decode anything.  Should be interesting. Does anyone have raw downlink data
samples that I could use to test what the FreeDV program can "hear"?

Thanks for the insights.

Tom Schuessler, N5HYP

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