Heterodyne when off-frequency on weak AM stations

Really enjoying the radio, great work.

I just updated to v1.19 of the software.  When I tune in an AM (modulation, not band) station a few kHz off center using the AM demodulator, with the carrier inside the passband, I  hear a heterodyne between the center frequency selected and the carrier.  I don't think this happened before.  It makes tuning really critical which I hadn't noticed previously.  Has there been any change in this area?



  • This problem was fixed back in the v1.13 release. The full story is here: https://github.com/jks-prv/Beagle_SDR_GPS/issues/23
    On the Beagle check the file /root/kiwi.config/kiwi.json and make sure there are the parameters
    towards the end of the file. The values will be different if you have performed the IQ balance procedure.

    If you still have problems try the following. Disconnect the antenna. Bring up the IQ extension. Tune to some frequency, zoom all the way in and verify that there is no signal on the waterfall. Bring up the IQ display gain until you get a circle of noise. Switch between sideband and AM modes. The circle should remain centered in the crosshairs when AM is selected and not offset.

  • All fixed, thanks!  Somehow the values were more like 0.5 and 0.6, but I set as you recommended and it's fine now.

  • Large, unbalanced values like that might have occurred if you had ever run the IQ balance with a signal present. Right now it requires admin privileges to run the balance. But there is no other checking or a confirmation panel telling you the consequences of what's about to happen. There probably should be.

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