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DIGU mirrors LSB sideband in bandpass in v4.1.3

JamesW7EY
JamesW7EY Member ✭✭
edited December 2025 in SmartSDR for Windows

I had problems working a DX station that was just above the normal FT8 window. In the SSDR waterfall I saw very few calling stations but in WSJTX it looked very busy but none of the signals were decoding. I noticed that when I switch to DIGL and moved below the FT8 window where there were no signals, I could hear and decode everything from the opposite sideband which was the FT8 window. If I switch to USB or LSB this doesn't happen so it's only DIGU and DIGL. It degrades the FT8 decoding for me if there is any noise or signal in the lower sideband. I opened a support case but was wondering if anyone else is experiencing this.

I made a video to show as an example: https://www.youtube.com/watch?v=wj-JrfTNEU4

Best Answer

  • Mike-VA3MW
    Mike-VA3MW Administrator, FlexRadio Employee, Community Manager, Super Elmer, Moderator admin
    Answer ✓

    If you have your digital audio filters set to low latency, you will see this as the filters are not as high Q.

    Low latency filters are not required for FT8 at all, so just go to Auto mode. This is not a bug but a trade off by going to lower latency.

    From Dave WO2X:

    When he goes up 3 kHz the FT8 signals are being heard on the LSB side of f0 so the tones are exact mirror of what they should be and it will not decode. When he goes top DIGL and is again hearing signals but on USB side of f0, it decodes. The bandpass filters are not 100% brick wall. He will hear signals past 0 and 3 kHz but there is naturally a rolloff of filter skirts. By changing RX filters from Auto to sharp, it will roll off the edges of his RX passband sharper.

Comments

  • JamesW7EY
    JamesW7EY Member ✭✭

    I fixed it with a factory reset and recreating all my profiles. Kind of a pain but it worked.

  • WX7Y
    WX7Y Member ✭✭✭✭

    James, just a hint on what I do here, I save my Profiles about once a week or two and make a copy and save it in another Subdirectory on my desktop just in case, about every 3 months I delete the older ones but this way I always have a good backup or 4 to choose from. They are all named using the Date so easy to keep track. Of course I am doing this with SmartSDR not on the M or Maestro.

    With version 4.0 I had to use these several times on the 8600 before I got things stabilized.

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