[Elecraft] Noise Blankers

[Richard Lamont]

On 03/09/17 20:38, Wes Stewart wrote:

> The K3S blanker is slightly better than
> useless. When I set it aggressive enough to be audibly useful, FT8
> decodes multiple signals at 120 Hz intervals, which upsets sequencing.

That's an inevitable consequence of how a noise blanker works.

It removes power line noise by muting reception 120 (or 100) times a
second, corresponding to peaks in the power line voltage when the arcing
occurs.

If you chop an audio tone up at 120 Hz, you are amplitude modulating the
tone with a 120 Hz waveform. That produces sidebands either side of the
tone 'carrier'. This is why you should never use a noise blanker with
FT8 and similar modes.

The best way to use a rig with WSJT-X is, generally speaking, to make
the computer do as much as possible and make the rig do as little as
possible. Treat it more or less as a dumb transverter. Don't use the
noise blanker, don't reduce the bandwidth below about 2.5 kHz, don't use
the notch filter. WSJT-X's decoder works best if you just get the level
about right and let it deal with the QRM.

73,
Richard G4DYA