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