[Elecraft] K-3 Noise Reduction

[Lyle Johnson]

The K3 NR algorithm is a trade-off between noise reduction and stability.

The wider the dynamic range of signals presented to it, the more 
aggressive it must be, which in turn makes it less useful for applying 
small amounts of noise reduction.

The NR pays some attention to the settings of AGC Slope and AGC 
Threshold.  The higher the Threshold, and the steeper the Slope, the 
more aggressive NR must be at its lowest settings to prevent instability 
(SCREECH!!!!).  We have chosen to make the NR somewhat more aggressive 
in all cases to prevent instability.

Thus, if you have AGC Threshold set low and the Slope set to flat, the 
NR will be more usable on weaker signals.

In the end, NR is a filter, and like any filter it will affect what is 
being passed through it.  The weaker the signal, the more it appears 
like noise and the harder it is to separate the two.

Finally, NR is part of a general field of psychoacoustics.  What some 
people like, others barely tolerate.  Somewhat like tastes in music...

We are always looking at ways of doing this better, and went through a 
very lengthy several months ago to improve NR.  You can be sure that we 
will revisit it when we review the status of the K3 firmware and operation.

73,

Lyle KK7P (your friendly K3 DSP guy)