Introduction
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JT9, one of the modes of the WSJT-X suite, is very popular on 630 m (and below) for weak signal DX communication.

JT9 uses 9-FSK with a rate of 1.736 baud. Each transmission has a duration of 49 seconds and the cycle rate is 1 minute. The bandwidth is 15.6 Hz. Some early versions of WSJT-X had also slower versions of JT9 such as JT9-2 (0.781 baud, transmission duration of 109 seconds, 2 minutes cycle rate and 7.0 Hz bandwidth), JT9-5 (0.293 baud, transmission duration of 290 seconds, 5 minutes cycle rate and 2.6 Hz bandwidth) and JT9-10 (0.145 baud, transmission duration of 588 seconds, 10 minutes cycle rate and 1.3 Hz bandwidth).

These modes were useful on MF and LF as they had a significant S/N advantage over JT9, but on HF they were too vulnerable to frequency instabities. In later versions of WSJT-X these modes were abandoned.

The aim of SlowJT9 is to revive JT9-2, JT9-5 and JT9-10 on MF and LF in order to get better DX opportunities. For convenience reasons, SlowJT9 also supports the original JT9(-1) mode.

For now only a Windows version of SlowJT9 is available. But as the used IDE has cross platform facilities it should be possible to support other operating systems as well in the future.

 

The aim of this beta version is:

  • To test if the application is working properly.
  • To find out if JT9-2, JT9-5 and/or JT9-10 have a sufficient S/N advantage over JT9(-1) and are useable on LF/MF.
  • To find out if there is sufficient interest in using these modes to continue the project.

Therefore all comments, bug reports and suggestions are most welcome via the Blacksheep RSGB LF Reflector, Groups.io RSGB LF Group, 600MRG discussion list (qth.net) or directly at rik@strobbe.org.

 

This version of SlowJT9 is tested on Windows Vista, 7, 8, 9 and 10.