Hi Bill, thanks very much, that did the trick. I can now generate perfectly decodable FST4 and FST4W that decodes to something. I made a lucky guess in putting a c28 (callsign) field at the start of the FST4W packet and that works so I shall have some fun being a code unbreaker to try and fill in the rest:) 73 Alan M0NNB
On Wed, Feb 10, 2021 at 3:09 PM Bill Somerville <[email protected]> wrote: > On 10/02/2021 14:40, Alan Hopper wrote: > > Hi, > > I'm trying to write a FST4 encoder without using the source, I'm most > > of the way there using the excellent FT4_FT8_QEX and FST4_Quick_Start > > docs, the latter mentions generator_fst4.dat and > > generator_fst4w.dat which I can't find. Are these available or can I > > extract those tables from the source without breaching the licence? > > Also what BT is used for the Gaussian shaping. I see details of the 50 > > bit payload are 'in preparation', If you want a proofreader, I'll very > > happily proof read by trying to implement it:) > > Thanks again for the great documentation and modes. > > 73 Alan M0NNB > > Hi Alan, > > I though there was a document describing the FST4 and FST4W protocols, > but I can find it right now. Yes you can use the parity generators as > they are part of the protocol. > > Here's the FST4 LDPC generator, a 139 by 26 matrix generating 139 parity > bits from 101 (77 + 24 bits CRC) message bits: > > > https://sourceforge.net/p/wsjt/wsjtx/ci/master/tree/lib/fst4/ldpc_240_101_generator.f90 > > and here's the FST4W LDPC generator, a 166 by 19 matrix generating 166 > parity bits from 74 (50 + 24 bits CRC) message bits: > > > https://sourceforge.net/p/wsjt/wsjtx/ci/master/tree/lib/fst4/ldpc_240_74_generator.f90 > > you will have to take my word for these two specific files being in the > public domain for now. > > BT for the WSJT-X FST4 and FST4W waveform Gaussian frequency smoothing > is 2.0. > > 73 > Bill > G4WJS. > > > > _______________________________________________ > wsjt-devel mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/wsjt-devel >
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