WSJT-X/doc/source/utilities.adoc
Joe Taylor 7324ece8a7 Forgot to put utilities.adoc in SVN. Here it is.
git-svn-id: svn+ssh://svn.code.sf.net/p/wsjt/wsjt/branches/wsjtx@3675 ab8295b8-cf94-4d9e-aec4-7959e3be5d79
2014-01-30 19:09:14 +00:00

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// Status=review
Utility programs +jt9code+ and +jt65code+ let you explore the
conversion of user-level messages into channel symbols or ``tone
numbers,'' and back again into user-readable text. These programs can
be especially useful to someone designing a beacon generator for JT9
or JT65, or for studying behavior of the error-control codes.
Channel-symbol values for JT9 run from 0 to 8, with 0 representing the
sync tone. The total number of symbols is 85. To run +jt9code+,
enter the program name followed by a JT9 message enclosed in quotes.
In Windows the result might look like this:
C:\WSJTX> jt9code "G0XYZ K1ABC FN42"
Message: G0XYZ K1ABC FN42
Channel symbols:
0 0 7 3 0 3 2 5 4 0 1 7 7 7 8 0 4 8 8 2 2 1 0 1 1 3 5 4 5 6
8 7 0 6 0 1 8 3 3 7 8 1 1 2 4 5 8 1 5 2 0 0 8 6 0 5 8 5 1 0
5 8 7 7 2 0 4 6 6 6 7 6 0 1 8 8 5 7 2 5 1 5 0 4 0
Decoded message: G0XYZ K1ABC FN42
For the corresponding program +jt65code+ only the information-carrying
channel symbols are shown, and the symbol values range from 0 to 63.
Sync synbols lie two tone intervals below data tone 0, and the
sequential locations of sync symbols are described in the
<<JT65PRO,JT65 Protocol>> section of this Guide.
A typical execution of jt65code is shown below. The program displays
the packed message of 72 bits (shown as 12 six-bit symbol values),
followed by the channel symbols:
C:\WSJTX> jt65code "G0XYZ K1ABC FN42"
Message: G0XYZ K1ABC FN42
Packed message, 6-bit symbols: 61 36 45 30 3 55 3 2 14 5 33 40
Information-carrying channel symbols:
56 40 8 40 51 47 50 34 44 53 22 53 28 31 13 60 46 2 14 58 43
41 58 35 8 35 3 24 1 21 41 43 0 25 54 9 41 54 7 25 21 9
62 59 7 43 31 21 57 13 59 41 17 49 19 54 21 39 33 42 18 2 60
Decoded message: G0XYZ K1ABC FN42
For an interesting illustration of the power of the strong
error-control coding in JT9 and JT65, try looking at the channel
symbols after changing a single character in the message. For
example, change the grid locator from FN42 to FN43:
C:\Users\joe\wsjt\wsjtx_install>jt65code "G0XYZ K1ABC FN43"
Message: G0XYZ K1ABC FN43
Packed message, 6-bit symbols: 61 36 45 30 3 55 3 2 14 5 33 41
Information-carrying channel symbols:
25 35 47 8 13 9 61 40 44 9 51 6 8 40 38 34 8 2 21 23 30
51 32 56 39 35 3 50 48 30 8 5 40 18 54 9 24 30 26 61 23 11
3 59 7 7 39 1 25 24 4 50 17 49 52 19 34 7 4 34 61 2 61
Decoded message: G0XYZ K1ABC FN43
You will discover that every possible JT65 message differs from every
other possible JT65 message in at least 52 of the 63
information-carrying channel symbols.