During the month of May (2018) a lot of Belgian club stations can use callsigns in the format OT70xxx. (The xxx is always 3 letters, for example our club station uses OT70TRA.)

In WSJT-X it seems impossible to set this call as 'mycall'; the call gets truncated.

Any clues how we could solve this? Except for making QSOs with all text in 'free text'?


You can't.

The callsign field uses a complicated encoding, different from freetext, in order to fit all allowable callsigns into only 28 bits. Although this encoding covers the vast majority of amateur callsigns in the world, it has restrictions:

  • there must be a digit,
  • there cannot be more than three letters after the last digit,
  • there cannot be more than two characters (letters or numbers) before the last digit.

There aren't bits available to encode any other possibilities. Unfortunately the last restriction means that callsigns with a letter-letter-number-number prefix simply don't have any valid encoding.


According to K1JT himself, the callsign field is rather restricted and must meet the same parameters as the one for JT65.



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