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WSJT-X
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20 Commits

Author SHA1 Message Date
Steven Franke 86b0affc56 FST4/W: Disable envelope shaping at start and end of transmission when environment variable FST4_NOSHAPING=1. Works for fst4sim too. 2021-01-18 13:47:54 -06:00
Steven Franke b9d33bc998 Address compiler warnings in fst4/w code. 2021-01-07 10:05:53 -06:00
Steven Franke fb7b751e6d
Remove hmod from command line parameters for fst4sim. 2021-01-04 15:00:03 +00:00
Steven Franke 701d517e6e
For fst4sim, use Lorentzian fading spectrum when fspread is negative. 2021-01-04 15:00:03 +00:00
Steven Franke b087328fc1
Don't waste time on excess BP iterations when doing K=50. Decode a little deeper. 2021-01-04 15:00:03 +00:00
Steven Franke 11b7aa9429
Implements decoding of FST4W messages as (240,50) crc-less codewords. 
By cascading the full 24-bit crc generator matrix with the (240,74) LDPC code generator, create a (240,50) generator that is used to decode with approximately 1 dB better sensitivity than the (240,64) with 14-bit CRC approach that is normally used. This approach treats the CRC bits as additional parity bits and provides no means for identifying incorrect codewords. All codewords on the list generated by the OSD algorithm have CRCs that match the CRC of the message payload. Codewords are validated by unpacking the message and comparing the unpacked message with the list of stored callsign/grid pairs stored in the fst4w_calls.txt file.
 2021-01-04 14:59:56 +00:00
Steven Franke 221ede2903 Remove some unused variables. 2020-09-14 13:07:07 -05:00
Steven Franke b49a90f530 Remove a redundant array. 2020-09-14 13:03:33 -05:00
Steven Franke 1b59d9dc8c Eliminate redundancies from the calculation of sequence correlations. 2020-09-14 12:42:32 -05:00
Steven Franke 5ca81a6507
Use 3rd order polynomial fit to estimate the noise baseline. The 
polynomial fit is done over 400 Hz bandwidth for T/R periods longer
than 15s, and over approx. 600 Hz (10 times the signal bandwidth) for
T/R period of 15s.
 2020-08-29 19:55:23 +01:00
Steven Franke d82b9f5b0e
Speed up decoder by eliminating some complex multiples in sequence detection loop. Add timer calls for doppler spread calculation and sequence detection loop. 2020-08-29 19:55:22 +01:00
Steven Franke b9328b96c9
Tweaks to update the diagnostics that are written to fort.21. 2020-08-29 19:55:22 +01:00
Steven Franke e02850ae5a
Streamline fst4_decode. Add timer for downsampling. 2020-08-29 19:55:22 +01:00
Steven Franke 782c779392
Reconfigure to optimize decoder for MF/LF (high coherence) channels. 2020-08-29 19:55:21 +01:00
Steven Franke bf06193c10
Add timer call for bit metric calculation. Improve some comments. Make fort.21 ntype parameter more informative. 2020-08-29 19:54:38 +01:00
Steven Franke 9d2bde7180
Fix SNR calculation for B,C,D submodes. 2020-08-29 19:49:46 +01:00
Steven Franke cdbe425e56
Use squared metric for fst4 - works better on fading channel. 2020-08-29 19:49:23 +01:00
Steven Franke 5eec869b2c Remove an unused file. 2020-07-23 13:22:12 -05:00
Bill Somerville a7223a5efa
A few more cosmetic 240 -> 4 changes 2020-07-23 19:13:05 +01:00
Steven Franke 085e63e05d Rename fst240 to fst4 in Fortran routines. 2020-07-23 12:48:50 -05:00