[Elecraft] Field Day and FT-8

[Andy Durbin]

I have operated WSJT-X modes for many years HF-6 meters.  I'm in a very large metro area with lots of active FT-8 users.  I have learned that stations with perfect signals on the HF bands can show all sort of artifacts on 6 meters.  For many of these stations it is not because the signals are not clean.  The various multiple signals can be caused by multi-path propagation sometimes with associated Doppler shift.  I'm not only in a signal dense area but under a busy airport arrival route.

The most common FT-8 signal defect is the presence of audio harmonics (harmonics of the tone modulation frequency).  These are usually caused by driving one or more audio stages into non-linearity and by refusing to use WSJT-X split mode.  These signal look very different from 6 meter multi-path.

73,
Andy, k3wyc