Locked Re: FT8 -- not decoding after transmit. Decodes fine for Receive Only

Al Groff

  I have observed that FT8 does not decode if the total CPU usage is high at the start of a receive cycle.  In my case I had a logging program that had high cpu usage at the end of a RX cycle overlapping into the next cycle and killing the folowing RX cycle.  I am unable to explain why your system has high CPU usage at the end of a transmit cycle.  I would suggest stopping as many non-WSJT programs as you can and see what happens.


On 2/27/2020 3:28 PM, Curt L wrote:

Hello all,


I could use assistance with WSJT-X decoding.  I spent quite a bit of time examining this problem and capturing data in what I hope is an understandable format.  You might be tempted to respond quickly after reading only the problem statement.  Please take a moment to glance over all the data; I've tried several remidies from previous threads in this forum.  Help is appreciated.



Curt / K7ZOO



After I transmit, no decodes are displayed.  The waterfall pauses for a few seconds after transmitting. 

Process "explorer.exe" and one or more "svchost.exe" processes use the CPU after transmitting (during the receive cycle), during 50% duty cycle tests.

During receive-only tests, these processes ("explorer.exe" and "svchost.exe") do not appear to be active at all.

KEY ITEM:  I'm not sure why "explorer.exe" and "svchost.exe" appear very active after transmitting.  They don't appear to be necessary to decoding, as they are not active when I'm only receiving.  Please see below where I've set the priorities of some processing, in an attempt to allocate more CPU to WSJT-X.   My intuition is that something in my system causes these processes to run, and they don't need to run at all for WSJTX decoding.



MAKE / MODEL                 HP Elitebook Folio 9470m

PROCESSOR                        Intel Core i5-3427U 1.9 GHz  2.4 GHz 

RAM                                      8 GB (7.87 usable)



MAKE / MODEL                 Icom IC-7200

FREQUENCY                       14.074

MODE                                   USB

AUDIO FILTERING            3600 Hz wide

DATA                                     ON

RF POWER                           tried both L and 30 watts; same behavior

MoD                                      U

D-MoD                                 U

USL LVL                                50



I downloaded, installed, and used “Process Hacker 2” to examine and set the priority of CPU processes as shown below:

wsjtx.exe            Priority                             Real Time

                             I/O Priority                      High

                             Save for wsjtx.exe           checked

Jt9.exe                Priority                              Above Normal

                             I/O Priority                       Normal

                            Save for jt9.exe                checked

explorer.exe     Priority                               Below Normal

                            I/O Priority                        Very Low

                            Save for jt9.exe                checked



a) WSJT-X does decode normally when I’m only listening

b) After transmitting only once WSJT-x skips (does not) decode for 1 to 3 cycles.  The DECODE button does not turn blue when it skips (does not) decode.  Decoding resumes after 1 to 3 cycles.

c) While transmitting at 50% duty cycle, WSJT-X does not decode.

c) Signals are always present / visible on the waterfall.


Graphs of CPU usage are shown below for (a) RX only, and (b) RX and TX at 50% duty cycle



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