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CX2ACB > SAT 20.07.03 05:50l 47 Lines 2132 Bytes #999 (0) @ AMSAT
BID : ANS-201.06
Read: GUEST
Subj: P3T Upgraded for AO-40 FEC Telemetry
Path: DB0ZKA<DB0GPP<DB0LX<DB0RBS<DB0SEL<DB0ZDF<DB0GE<LX0PAC<LX0HST<HA3PG<
IK1ZNW<VE3FJB<F6GGY<ON4HU<CX2ACB
Sent: 030720/0336Z @:CX2ACB.MVD.URY.SA #:796 [Montevideo] $:ANS-201.06
From: CX2ACB@CX2ACB.MVD.URY.SA
To : SAT@AMSAT
AMSAT News Service Bulletin 201.06 From AMSAT HQ
SILVER SPRING, MD. July 20, 2003
To All RADIO AMATEURS
BID: $ANS-201.06
If you have been following AO-40 telemetry on the Goddard server recently,
you may have seen curious A-blocks with the message:
+--------------------------------------------------------------+
| RECONSTRUCTED FROM DECODED FEC BLOCK |
+--------------------------------------------------------------+
These blocks were decoded by Stacey Mills, W4SM, using a modification of the
G3RUH MK II 400 BPS PSK demodulator, and a new version of the P3T telemetry
decoding software program. 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).
[ANS thanks Stacey, W4SM, for the above information]
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