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Whistle or tone when not tuned exactly - version v1.397 [fixed in v1.398]

edited August 2020 in Problems Now Fixed
Hi Folks,

Love my KiwiSDR. Had it about 9 months now.

I have noticed recently that I can hear a tone when I tune a station but it's not right on the frequency. I don't recall this in previous releases. For example, 11879.59 makes the tone but 11880 doesn't. It sounds like the beat frequency between the carrier and the offset of where the radio is tuned.

Power cycled and forced a software rebuild. No change.

Anyone else notice this?

Ken

Comments

  • What mode? there are more modes available now so you may not be in the simple AM mode (assuming it is AM we are talking about).
    Try cycling the mode button.
    Stu
  • AM and AMN modes.
  • Well here I can't easily try that frequency as two stations are currently overlapping.
    Things I'd check:
    1. Try it on another SDR elsewhere, same frequency.
    2. Monitor the tone with a phone app like Spectroid see if it changes with the tuning (same ratio)
    3. try another station without any overlapping stations (even a very weak station carrier can be heard, think morse)

    Assuming you are not sufferering overload it may be spikes from ADSL, Network or other clocks.
    To look any further someone would have to be able repeate it elsewhere, on more than one or two frequencies.

  • I just tried to duplicate the reported issue and could not. Is the system you see this on public access? I tried it here locally on jimlill.com:8073
  • jksjks
    edited June 2020
    Your IQ balance is almost certainly off as a result of pushing the "IQ bal" button in the IQ display extension when not tuned to a quiet part of the spectrum (or having the antenna disconnected). There is a topic explaining all this: http://forum.kiwisdr.com/discussion/699/why-a-beat-in-am-incorrect-iq-offset/p1

    Easiest way to confirm this is to check the beginning messages in the log tab on the admin page. You should see numbers for the I and Q balance that are either the default (-0.02) or roughly the same. Example:
    Thu Jun 18 15:46:49 00:00:32.361 ....      using DC_offsets: I -0.020000 Q -0.020000
    
    Powernumpty
  • Thanks John, I think that will take care of it. I am now in the part of the day where there isn't much to listen to. It's not noticeable on stronger MW stations.

    It was at .05 for both, now showing DC_offsets: I -0.020019 Q -0.018597 after following the procedure mentioned.
  • Well, it looks like you found a bug. The value 0.05 was the default a long time ago. At some point code was added to detect this and change to the new default value of -0.02. But this code has a problem that keeps it from working. I can't believe this hasn't been spotted until now. I'm sure I checked it back then (it's been several years maybe). We have changed compilers since then, but that shouldn't have made a difference.

    Anyway, the bug will be fixed in the next release. Thanks for calling it to our attention!
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