external FEC_LIB on the function decls alone does not register the
library with ld on FPC/Darwin — viterbi27/rs_8 symbols stayed
undefined at link time. Mirror the working WDSP pattern ({$linklib
wdsp}). This is not static linking: ld prefers libfec.dylib over .a
when both are in the search path.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Full chain now decodes the QO-100 central beacon to 256-byte AO-40 frames
on-air (frames>0, RS errors=0). Builds on M1 (stable BPSK demod).
FEC backend (BeaconFEC.pas, TBeaconFEC):
- AO-40 FEC: distributed sync (65 bit, step 80) -> 80x65 deinterleave ->
Viterbi r=1/2 k=7 -> CCSDS descramble -> 2x RS(160,128). Links system
libfec (Karn) load-time (libfec.so/.dll/.dylib). Viterbi AO-40 [0x4F,-0x6D]
remapped to libfec [0x6D,0x4F]. Validated against gr-satellites reference
vectors (fectest2: exact 256-byte frame, 0 mismatches).
DBPSK Manchester frontend (BeaconDecoder.pas):
- Chip-rate (800) processing: RRC matched filter -> ML signal-times-slope
timing recovery -> Costas -> Manchester combine (block phase select) ->
differential decode -> soft symbols to FEC.
- Carrier acquisition: squaring-FFT estimates the residual (carrier at +-pi/chip
defeats decision-directed Costas), one-shot pulls it to DC via residual NCO.
- Costas frequency offload into pre-RRC NCO (with deadband) tracks LNB drift
without hitting the +-pi Costas clamp.
- ML TED replaces Gardner, which degenerates on the Manchester chip stream.
Temporary on-air diagnostics retained (IQ dump + STATE log) pending wider
signal validation; to be removed before final cleanup.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
ew8bak
