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Re: [wsjtgroup] JT9 Coding

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  • Joe Taylor
    Hi Andy and all, ... Possibly you still want to do it yourself, for educational reasons. But if you just want to see how a particular JT9 message is encoded
    Message 1 of 2 , Nov 28, 2012
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      Hi Andy and all,

      G4JNT wrote:
      > Can anyone give me a pointer (or better still a listing) for the JT9
      > encoding algorithm? I can't seem to find it on the Sourceforge site.
      >
      > The time has come for a PIC / DDS implementation, and to do that I need to
      > be able to generate the raw symbol data. So the first step is a complete
      > understanding, and writing my own prog to convert input text to symbols.
      >
      > Already done for WSPR, JT4 and ISCAT http://www.g4jnt.com/JTModesBcns.htm

      Possibly you still want to do it yourself, for educational reasons. But
      if you just want to see how a particular JT9 message is encoded into 85
      tone frequencies or "channel symbols", I have written a program jt9code
      (analogous to jt65code, with which you are familiar) that does just that.

      You can download jt9code.exe from the following link:

      http://physics.princeton.edu/pulsar/K1JT/jt9code.exe

      Here's an example of the program's execution and output:

      C:\WSJTX> jt9code "CQ K1ABC FN42"
      Message: CQ K1ABC FN42
      Channel symbols:
      0 0 6 2 0 3 5 3 4 0 1 7 2 6 8 0 1 7 8 7 3 5 0 1 7 3 3 3 3 7
      1 6 0 5 0 6 7 2 6 7 7 4 2 3 4 6 8 1 5 2 0 0 8 4 0 6 7 3 1 0
      1 5 7 7 1 0 4 3 6 6 6 4 0 7 1 5 6 6 3 5 8 5 0 4 0
      Decoded message: CQ K1ABC FN42

      Tone frequencies 0 through 8 are translated to audio frequencies
      separated by 12000.0/nsps, where nsps is the nsps, the number of samples
      per symbol as given in a table in the WSJT-X User's Guide,
      http://www.physics.princeton.edu/pulsar/K1JT/WSJT-X_Users_Guide.pdf.

      Finally, if you do want to do it yourself: my source code is all freely
      available. It's on Berlios, not SourceForge. If you have SVN
      installed, you can download all code releted to WSJT-X and JT9 with the
      command

      svn co svn://svn.berlios.de/wsjt/branches/wsjtx

      I hope this helps!

      -- 73, Joe, K1JT
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