Constant tone in LimeSDR Mini output

  • Dear OMs

    I have encountered an issue but I don't know what's the reason:

    When transmitting with LimeSDR Mini, I see a constant tone in the background of my signal, but I don't have the same with PlutoSDR. To show you the difference, I made screenshots with a muted microphone while transmitting. As you see Pluto has a clean signal, but LimeSDR Mini still has that tone (although the mic is mute)

    All the hardware and software setup are the same (SDR Console latest version with the same config, CN0417 pre-amp and also the same PA)

    Have anyone else made a similar observation? Do you know what's the source?

    I have also attached 2 pictures of the output of the two SDRs connected directly to spectrum.


    Pluto connected to spectrum:

    LimeSDR Mini on spectrum:

    Pluto on QO100 WebSDR:

    LimeSDR Mini on QO100 WebSDR:

  • Hi,

    I have made the same observation and was told, that if you reduce the gain to 40 - 50 the signal should disappear. In this case, of course, you need to amplify the LimeSDR Mini externally to compensate for the attenuated signal.

    For my setup (LimeSDR Mini on 50 MHz to feed a BU500) it also worked to calibrate the TX-section of the LimeSDR Mini. in SDR Console, for example, you need to press the TX button and then, on the left side of the pane, press the „TX Calibrate“ button (be careful, you should disconnect the PA before calibrating to avoid damage).

    Best 73

    Holger ‚Geri‘, DK8KW