Spontaneous Mode Change in FT8

Bill

I am running a Flex 6400, SmartSDR 2.4.9, WSJT-X 2.01 and JTAlert 2.12.1.  No additional control software loaded, although I do use HRD logbook running without the HRD control module. Lots of contacts on FT8, but I continue to have spontaneous mode changes from DIGU => USB.  The net impact of this change is likely minimal, probably the last .300 khz of band pass, but I don't understand why this continues to happen.  There are some much older posts regarding this, but none seem to apply to me.  Is anyone else experiencing this phenomenon, or understand why the SDR mode will not stay where it is set (with no change in band) using WSJT-X?

Ted VE3TRQ

Are you running with “None”, “Fakeit” or “Split”? I suppose it would be possible that if you were using “Split”, the switch to a second VFO/Slice by wsjt-x could be triggering the change. What happens if you force “None”, or “Fakeit” (that is assumeing you are not already doing that)?

Mike-VA3MW

Arvind Mallya

Can someone explain what is "fake it"

Ted VE3TRQ

“None” means leave the frequency alone and just send the audio tone. “Fake it” means adjust the VFO frequency AND the tone so that the resulting signal is in the middle or “sweet spot” of the passband, preventing transmission of nasty harmonics of the audio signal. “Split” means do what “Fake it” does, except use a second VFO / Slice, instead of adjusting the frequency of the VFO in use. In all cases but “None”, wsjt-x sends CAT commands to the radio to adjust it.

Bill

Al K0VM