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FEC version of P3T




P3T upgraded to decode AO-40 FEC encoded Telemetry
--------------------------------------------------

If you have been following AO-40 telemetry on the Goddard server over the 
weekend, you may have seen curious A-blks with the message:

+--------------------------------------------------------------+
|            RECONSTRUCTED FROM DECODED FEC BLOCK              |
+--------------------------------------------------------------+

These blocks were decoded by me using a modification of the G3RUH MK II 400 
bps PSK demodulator, and a new version of my software P3T. The modification 
to the demodulator, developed by G3RUH, involves the addition of an 8 bit 
ADC, with minimal changes. For more details, see:

    http://www.jrmiller.demon.co.uk/products/p3adc.html


With this modification, the MK II demodulator can continue to function in 
standard or "hardware" mode or, with the flip of a switch, can output ADC 
data at 9600 bps, 1 byte per bit of telemetry data.  P3T will also function 
in standard mode as before, but now includes the option for ADC input. In 
ADC input mode, P3T expects a serial port data stream as detailed above of 
one 8-bit byte per bit of telemetry data. In this mode, it will decode 
standard format telemetry blocks and will also handle all FEC decoding 
processes, generating a reconstituted A-block with the header as seen 
above. Eventually, P3T will be further modified to accept ADC data from a 
soundcard.

The performance of this system really has to be seen to be fully 
appreciated. In FEC mode with even a modest receiving setup, every single 
block should be properly error corrected if the squint is less than 90 
degs. FEC blocks that are barely audible or with severe spin-modulation
fading will decode correctly. The P3T software is in final beta testing and 
will be available within a few days.  This system will be demonstrated live 
at the upcoming AMSAT-UK meeting in
Surrey by G3RUH using a solo RHCP patch antenna (no dish).




-- 
  _______________________________________________________________________
  Stacey E. Mills, W4SM    WWW:    http://www.cstone.net/~w4sm/ham1.html
   Charlottesville, VA     PGP key: http://www.cstone.net/~w4sm/key
  _______________________________________________________________________

----
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