FT8 not operating on all bands.

  • 1
  • Question
  • Updated 2 years ago
I have been using WSJTX's FT8 for the last week on my Flex 6500 running Smart SDR v2.0.19.98.  Had some initial issues with DAX so I reloaded Smart SDR.  Now suddenly FT8 only works on 20 meters.  I have tried 40 and 80 and will not show anything under band activity.  I reloaded Smart SDR and that did not help, I then reloaded WSJTX and still does not work.  Could someone point me in the right direction.
Photo of Randy


  • 14 Posts
  • 0 Reply Likes

Posted 2 years ago

  • 1
Photo of Mark - W3II

Mark - W3II

  • 249 Posts
  • 54 Reply Likes
Make sure your slice has its DAX Channel assigned to the one you have configured in WSJTX.
For TX you need to make sure the DAX button is selected on the P/CW panel. 
DAX program must be running and the RX Stream must be enabled (blue)
Photo of Lee - N2LEE

Lee - N2LEE

  • 320 Posts
  • 167 Reply Likes
I am sure Mark has the right answer.

Photo of Ria - N2RJ

Ria - N2RJ, Elmer

  • 2328 Posts
  • 966 Reply Likes
There are a few things I always check:

FIRST AND FOREMOST - Time sync. Make sure you use Meinberg or another time sync software. Make sure it is working. 

Is your mode DIGU? Make sure it is DIGU. Make sure the bandwidth is 3kHz. The default is 1kHz at the center of the channel which doesn't work well for most digital modes. How are you changing bands? If you change it in WSJT-X you likely won't have this issue. If you are changing the band directly in SmartSDR, then you will most likely have an issue because of the aforementioned default setting (which I hope is fixed in a future version). 

Then I would check if DAX is enabled on the slice, that the correct DAX is selected, and the levels are not overloading. Does the level meter on WSJT-X move? It should be around 30-40 with just band noise.

Sometimes DAX has an issue where it starts to stutter. I would restart DAX app and see if that helps. CPU hogs like teamviewer can cause issues on slow computers.

Photo of ai6re


  • 108 Posts
  • 20 Reply Likes
Make sure you are in Upper Sideband on 40m and 80m as the radio will default to LSB and you will not decode any traffic.