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Re: Prototype FEC telemetry encoder/decoder released



>I agree.  We will need ground station application software that 
>can receive the new format.  If no one can receive it, it will
>be a long time before it's implemented on AO-40.  

I'm also interested in user reports from anyone trying it out via the
transponder, over a terrestrial path or even simply running it in
software simulation mode.  VK2TFG has already been a big help in
finding and fixing a few little gotchas that cropped up when he built
my code on a different Linux distribution with a different version of
GCC.

The modulation, demodulation and FEC techniques I used have been
around literally for decades. Their properties are now very well
understood and I believe they are nearly optimal for this particular
job. So the real fun now is in finding and fixing all the little
portability, usability and integration issues just like the ones Geoff
helped me find.

If this format is accepted, implemented into the spacecraft and
integrated into AO40RCV and other telemetry reception programs, it
will be no harder to use than the present format. The only observable
difference is that performance will be significantly better (by ~6-7
dB) when the beacon signal is weak, and *dramatically* better (by
*TENS* of dB) when spin and bad squint angle induce deep fades and
rapid doppler shifts. It will also be immune to "false lock" and
highly resistant to radio retuning transients.

I plan to add a coherent BPSK demod to a future version of my
prototype.  This will be compatible with the same FEC transmission
format but increase performance on weak, non-fading channels by
another 3-4 dB, i.e., to 10-11 dB better than the present uncoded
format.

Phil


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