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Laptop problem distorting digital

Ross Biggar
Ross Biggar Member ✭✭
edited April 2020 in Third-Party Software
I have an HP i7 laptop that I would like to use for digital modes in our house, to save me a 50 yard walk from the house to the shack.
My problem is trying olivia or similar modes the output out of the laptop is distorted.
I am testing using my 6600M which is connected via the network to a wifi router and then to the Laptop. The laptop is running 3.1.8, the signal from the 6600m is being transmitted (at low power) and being picked up by the 6700 which is on a dummy load.
Looking at FLdigi on the laptop the transmission does not looks similar to an Olivia signal but is unreadable on the 6700.  (All radios are running 3.1.8)

So my problem is what can cause or is likely to cause the distorted signal from the Laptop and also any incoming signal (on receive) cannot be decoded.

I checked Device manager and all the DAX audio look ok.

Ideas please
Best wishes , I hop all are having a good Easter and staying safe.

Ross ZL1WN


  • KD0RC
    KD0RC Broomfield, COMember, Super Elmer Moderator
    edited April 2020
    Hi Ross, One thing to check is if you are over-driving the transmitter.  In FLdigi (or whatever you are using to transmit), try cutting back the drive level to see if you see any change in the sig quality.  You can also try the mic gain on the Flex.

    Len, KD0RC
  • Ross Biggar
    Ross Biggar Member ✭✭
    edited April 2020
    Thanks Len, that could explain the transmit, but it doesn,t explain why the Laptop doesn't receive 
    correctly the signal seen on FLDIGI on the ;laptop is obviously distorted, even though the transmission from the 6700 is perfect.
  • Bill NE1B
    Bill NE1B Member ✭✭✭
    edited April 2020
    Also refer to the forum notes on DPCs and DAX Distortion. Different PCs or laptops may not exhibit these issues.

    from K3TIM:
    "If having problems with decodes after nnn hours, suggest running a DPC latency check program.  I've observed the PC can pass the "Real Time" criteria and have zero issues with decodes.  With Chrome browser open with 5 windows and 40 tabs each, the DPCs fall out of RT support. Be that as it may this particular PC never seems to have DAX buffer issue.

    also from   
    Ken Wells (FlexRadio Systems) 

    Oct 16, 3:58 PM CDT

    Hello Michael,

    Some stations seem to have more troubles with DAX Buffer Corruption than others.
    The issue has multiple causes, but a major contributor is DPC's (Deferred Procedure Calls) on your computer.

    Here are two articles that Tim has written that can help explain some things.



  • Pat W5VY
    Pat W5VY Member
    I'm having occasional problems with distorted TX audio on WSJT-x modes with my F6700 on 3.1.12. It seems to happen when the F6700 and DAX have been running for more than a day without restarting DAX. It happens with the SSDR Windows Client and with my Maestro. Restarting DAX heals the problem. My Windows PC is a i7-8700 running W10 Pro 20H2 with 16Gb DRAM. I don't use Chrome and the DPC Latency Monitor check passes with no issues. Is this a DPC issue or DAX issue? Any know issues with Maestro and DPC Latency? I was on 160M FT8 tonight and got an email from Victor, WB0TEV, telling me I was wide and distorted. Restarted DAX and everything returned to normal. I was running the Maestro with two slices active.
  • WX7Y
    WX7Y Eastern Utah, USAMember ✭✭✭
    edited January 2021

    This is a known issue with DAX, I am pretty sure it is in Flex's problem data base.

    Best thing is to just shut down DAX and restart it for temporary relief until Flex comes out with a fix.

    Makes sure your not overdriving the Audio going into DAX as well.

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