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Noise Blanker and Noise Reduction

edited September 2017 in Problems and Issues
Please, concider on building some software plugins like Noise Blanker and Noise Reduction, included of course to "extensions". Eliminating a typical background noise on HF even slightly, will dramatically improve S/N ratio.
Thank you.


  • No answer to this topic until now... Maybe is rather difficult for this kind of a project, I guess.
  • they are on a wish-list already IIRC
  • Hi,

    If you are just having problems with background noise rather than actual interference, you may find it worthwhile experimenting with different receive bandwidths and AGC settings.

    Adjusting the AGC threshold away from its default value (in the extra receiver control panel that is displayed by using the 'more' option), is one setting that can make huge difference to your listening pleasure.

    The default setting is pretty good for most KiWi's most of the time, but depending on your local conditions some adjustment may be worthwhile.


    Martin - G8JNJ
  • Thank you very much for the advice. 
    The problem is a typical one of pulse and/or line noise, that almost everyone can hear when he lives in urban areas. This kind of noise can be handled with internal NB filters that ham equipments use, or with software NB and NR extentions that some SDRs use with their included software applications.
    I also use IC-7300 and Perseus SDR with the very same antenna system and I can handle the noise when it appears very well, but with Kiwi this is impossible. For now, I am using an external BHI NB/NR filter, which is very effective, filtering the final audio from Kiwi, but the listeners do not use such a hardware. That's why, I wonder if a software NB and NR plugin, would be very useful.

    Emmanuel, SV1BTL
  • Hi Emmanuel,

    I had some noise today and I found that turning the AGC off and manually setting the gain seemed to help with impulse interference.


    Martin - G8JNJ
  • That's an old ham trick
  • Well I'm an old ham so I guess that's OK :-)


    Martin - G8JNJ
  • Thank you Martin! I'll apply something like this.
  • less AGC delay can help too
  • I've been thinking about noise blankers, notch filters and LMS noise reduction filters.

    My first thoughts were to process the audio in the tried and true way.

    But after watching the European thunderstorms while trying to listen to 3C0L I noticed how clearly the waterfall marks static crashes. It was fun seeing the storms in Spain on G8JNJ, for example and comparing with the view on closer receivers.

    Anyway, it occurs to me that it would not be hard to detect wide band "static" and use it to blank or interpolate the audio stream. It appears the audio stream is already delayed behind the waterfall FFT bins, so there would be time to handle this in the browser, I think.

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