[amsat-bb] Re: Decoding wideband recordings

Iain Young, G7III g7iii at g7iii.net
Wed Aug 10 09:20:13 PDT 2011



On 09/08/11 23:54, Phil Karn wrote:

> It's been suggested that I modify my ARISSat-1 BPSK-1000 telemetry
> demodulator/decoder to accept wideband quadrature (I & Q) recordings
> like those produced by most of the software defined radios out there.
> 
> This is fundamentally not that hard, but first I need some information.
> 
> How many people could actually use this? What is the format of the
> recorded files? Is there a standard, or does each make of SDR produce
> its own?

I'd use it. In fact I drive my Funcube Dongle with gnuradio. It would
mean I could simplify my flow graphs, and not have to stick have the
audio out to a loopback ALSA soundcard, and then into your decoder.

(I could then squirt the I/Q stream to a FIFO, and pump that to your
decoder, and save all the blocks needed to do the SSB stuff, and
dropping it down to audio)

In fact, IIRC, its not that hard in gnuradio to do BPSK decoding anyway,
it's just no-one's actually done it. You have to just unhook the
differential part of the decoder AIUI. Easy in python, but not possible
so much in the in the gnuradio-companion, which I use to construct the
flow graphs graphically


73s

Iain


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