v1.576: NNFM mode added (6 kHz version of NBFM)

From the CHANGE_LOG file:

v1.576 Feb 2, 2023

  FM demodulator:

    Added NNFM mode which has a 6 kHz passband useful for FM signals with +/- 2.5 kHz deviation.

    Fixed "rough", "crackling" sound of demod. Needed a post-demod clipper.

Note: work on a proper FM de-emphasis filter has not started.


  WSPR extension:

    Added test button. Test result spots are NOT uploaded to wsprnet.org

    Added help panel.


  Restore mode and passband on extension exit from: FAX, FFT, HFDL, IQ, SSTV and WSPR


  By request, right-click menu shows both of these entries all the time:

    "open DX label edit panel" and "edit last selected DX label"

    Previously they appeared in a single menu slot under different conditions

    which wasn't optimal for all use cases (Thanks W4ILM).

  FAX frequency menu updates.


  • Hi John,

    Thanks for looking at the NBFM problem. The new version is a VAST improvement, and as well as making the audio much more pleasant to listen to, it also seems to have improved the squelch action too.

    If you have the time, or the inclination, can I suggest some further minor improvements.

    Have the De-emphasis on by default, even the current settings make a big difference to the audio quality.

    There is a squelch setting difference of about 30 in the slider scale between 12kHz and 6kHz bandwidth. Is there any way of compensating the level setting for the bandwidth in use.

    Would it be possible to use the existing momentary squelch open button to toggle the squelch between open and the last squelch setting. This makes it easier to open the squelch and leave it open if a signal is weak, then quickly restore it back to normal without having to adjust the slider. Maybe a short press could set this, whilst a long press retains the current temporary action.

    Would it be possible to somehow implement a squelch auto threshold setting ?

    If these involve a lot of work, then please don't bother, they were only ideas to improve some of the day to day adjustments.

    Thanks again John, this fix is very much appreciated.



  • Yea, agreed, great fix. FM demod is MUCH better. Thank you!


  • Only today I had the opportunity to listen to how FM works after the update, there is power! Great piece of work, thank you

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