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Spontaneous Mode Change in FT8

Bill Member ✭✭
edited June 2020 in SmartSDR for Windows
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
    Ted VE3TRQ Member ✭✭✭
    edited December 2019
    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
    Mike-VA3MW Administrator, FlexRadio Employee, Community Manager, Super Elmer, Moderator admin
    edited April 2019
    This is a WSJT configuration issue.  If the radio changes modes, then something commanded it to change modes externally.

    This is one of my setups.  Make sure you have Mode set to None.

    Mike va3mw

  • Arvind Mallya
    Arvind Mallya Member ✭✭
    edited June 2020
    Can someone explain what is "fake it"
  • Ted  VE3TRQ
    Ted VE3TRQ Member ✭✭✭
    edited March 2019
    “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
    Bill Member ✭✭
    edited March 2019

    You nailed it!  Mode in WSJT-X was indeed set to USB, so the 6400 was just doing what it was told to do!

    Problem solved....

    Thanks and 73s
  • Al K0VM
    Al K0VM Member ✭✭✭
    edited March 2019
       What are you using for rig in WSJT-X? 
       1) There should be no reason to use anything but 'None'  with Flex..  The total digital audio stream does not generate audio harmonics and the TX passband is flat, and thus no need for keeping the TX tones in the 'sweet spot'.

       2) The bug in WSJT that effected the 'Flex 6xxx' interface was fixed in WSJT V2.0.1 and has been very reliable.  However you may need to use the Kenwood TS-2000 rig type is you're running CAT through Smartlink.

      3) I prefer to use PTT via CAT  for PTT method. PTT via RTS has no advantage when using virtual  serial ports ( the data is never converted to a serial stream with virtual serial ports and thus there is no serialization delay ).

    AL, K0VM

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