QRN reducer ? For those with a computer near their Ham receiver

[K1DEU]

Eventually I will run an audio cable across my ham shack or ask KC2IFR to e-mail me a mp3 recording of some AM'ers talking while the Lightning static crashes are more than fatiguing to listen to.

By Googling " vinyl record scratch click filter* freeware " or " vinyl record scratch click filter* shareware " (or with less words) there are several interesting apps, either free or $25 or less that might be very usable. Obviously we should do our processing closer to the receiver antenna and not at the speaker/headphone jack. But any thing that might help 10 Db or more I'll use.   

We still have QRN in the northern Hemisphere Click here http://thunderstorm.vaisala.com/explorer.html

If I Owned a SDR it would be a quick experiment.

Then we could try Sibelius or Sound Forge 9, but not only for QRN reduction !  Any thoughts Dan (W1DAN) or some of the other sound engineers ? John, K1DEU

[WBear2GCR]

 Yeah John, good idea!

You might try the Soft Rock Lite or the Japanese (?) kit that AB2EZ found with it??

dunno that both can run concurrently or not using the same soundcard??

But I was thinking that it might not recognize static as the sort of noise it is looking for... although it might. Wonder if it applies a spline and tries to "carry through" the periods of click & pop noise or just acts as a noise gate?

                           _-_-bear

[AB2EZ]

John
Bear

I agree with John that adding sophisticated signal processing methods to remove (or significantly reduce) static crashes is an old idea whose time has come. I'm not into designing DSP algorithms or bringing them to life in software... but I'm sure that there are many people among the SDR gang who are.

Of note...

1. Although we prefer to have negligible delay... our simplex mode of operation doesn't suffer that much from delay in the receiving direction. So... there is plenty of time to store the incoming I and Q waveforms while examining them for signatures of static crashes... which would then be adaptively subtracted out, if possible... or muted* if they can't be usefully subtracted out.

2. It should be possible to use such techniques as monitoring adjacent frequencies or a wide band of frequencies (easy to do with SDR) to help detect the arrival of a static crash whose in-band amplitude is comparable to that of the signal you are trying to receive.

3. It is important to have enough dynamic range in the receiver, up to, and including the A/D converter... to make it feasible to adaptively subtract out all but the largest static crashes (which will be muted*). Things like fast-acting AGC's may have to be modified to achieve sufficient dynamic range/linearity for the subtraction process to work well (i.e., the fast-acting AGC functionality may have to be implemented after the adaptive static crash subtraction process)

*What I am referring to here as muting would actually best be done by removing each segment of the waveform that is corrupted by a static crash... and then "interpolating" between the start and the end of that segment with a surrogate (replacement) segment of waveform that causes minimal subjective degradation.

These approaches/ideas are not new... but computers with abundant, cheap memory and abundant processing power make them practical to implement in consumer/amateur radio applications.

As an aside... adaptive interference cancellation (noise and signals) using multiple antennas... is also an old idea whose time has come with the advent of SDR's.

Stu