v1.391,392,393,394: New noise blanker and filters

edited May 2020 in KiwiSDR Discussion
From the CHANGE_LOG file:
v1.391  May 23, 2020
    User interface changes:
        SAL, SAU mode passband image will only show single sideband (just like LSB, USB).
        Ctrl/alt-click on mode button toggles modes backwards (most useful with SAM modes).
        Same works with keyboard shortcuts, e.g. ctrl/alt-A toggles SAM modes backwards.
    Noise blankers and filters:
        Reworked the audio tab user interface to support multiple blanker/filter algorithms.
        New algorithms planned but not yet available are greyed-out in the menus.
        From Warren Pratt's wdsp package added the variable-leak LMS algorithm.
    Merged Howard Su's RPi changes.
        Note: RPi is not officially supported by KiwiSDR. Ask for help on the KiwiSDR forum:
    Bug fixes:
        Audio recordings made in SAS (synchronous AM stereo) mode now work.
        Fixed problem with ITU region 2 Kiwis and shift-clicking waterfall in 75/80m band segment.
        from lazywalker: fixed problems with frequency memory and reload value when transverter offset used.


  • jksjks
    edited May 2020
    From the CHANGE_LOG file:
    v1.392,393  May 28, 2020
        Noise blankers and filters:
            Added the Michael Wild noise blanker. Not a lot of operating experience with this yet.
                It seems not to work on some noise sources compared to the standard blanker.
                A good test source is 100 kHz Loran-C in AM mode using a UK Kiwi.
                Increase the gate time (standard blanker) or impulse samples (Wild blanker) to
                account for the longer Loran-C pulses compared to the usual impulse noise.
            Fixed wdsp filter: the control sliders had no effect previously!
                Now it works quite well. You have to adjust the gain carefully to prevent overload.
            Added test pulse gain and pulse width controls. And also whether the pulse is
                applied before or after the passband filtering. The Wild blanker seems only
                effective on post-filter pulses. Probably because the filter is turning the
                pre-filter step function pulses into nicer band-limited pulses.
  • jksjks
    edited May 2020
    From the CHANGE_LOG file:
    v1.394  May 31, 2020
        Noise blankers and filters:
            Added the spectral noise reduction filter by Frank, DD4WH and Michael, DL2FW, via the
            Teensy-ConvolutionSDR and UHSDR projects. See: github.com/df8oe/UHSDR/wiki/Noise-reduction
            This noise filter works really, really well. Especially for voice signals.
            A good alternative to the LMS filters.
        Note that the Wild blanker and all the noise filters (wdsp, LMS, spectral) don't currently work
        with the modes: IQ, SAS and DRM (i.e. the 2-channel IQ modes). This will be fixed at some point.
    This filter is on the main control panel, audio tab, "noise > filter" menu. Click the "more" button to the right of the menu to adjust the filter parameters, although the filter works well with the defaults. In some cases you might have to increase the filter gain to match the filter-off level, especially during A/B comparisons. Try it with a weak station on the AM broadcast band or ham band SSB signal.

    Note that some noise filters always require their sections be enabled via the "more" panel. Otherwise simply selecting their menu entry does nothing. In particular the wdsp and LMS filters since they have independent denoiser and autonotch sections that are enabled separately (or both simultaneously).
  • That spectral filter makes distant stations so much less tiresome, excellent stuff.
    Just been listening to some interesting other viewpoints to the uniform UK MSM.
    I'd forgotten one of the pleasures of SWL.
  • Wow! that Spec filter is great. Really cleans things up for listening.
  • very nice!! SAS+SPEC on SWBC makes it sound like FM
  • Do you mean SAM+spec? SAS should give you an error message in the extension control panel since it is an "IQ or stereo" mode that cannot be used with the real-only filters currently (Wild blanker, wdsp, LMS, spec). This limitation is mentioned in the CHANGE_LOG file but was accidentally omitted from the CHANGE_LOG copy/paste above (now fixed).
  • OK... I didn't see any error messages but maybe missed it
  • If you enable the Noise stuff from the extension panel you see it but no error messages if you use the buttons/pulldown directly in the main panel
  • I can't replicate this. I always correctly get the error message. Can you be more specific about exactly what you do to reproduce this?
  • I just hit the audio button in the main panel, thus select spec on NF, while in SAS
  • Okay, the issue is that the extension panel on the left will not popup just because you are in an IQ/stereo mode (e.g. SAS) and you hit the audio button. You still have to click "more" to get the panel to appear. The presence of the error is not enough to get the panel to popup.
  • OK, not a big deal for me. Thanks for explanation
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