[Elecraft] Dummy's Guide to Noise Reduction

[Stewart Rolfe]

To all NR 'confusees',

Since getting my K3 #145 I've seen the discussion about Noise Reduction 
go round the block 2 or 3 times and I have to wonder if folk bother 
reading the FAQ which I've copied below...

<<<<<<<<<<<<<<<<<<<
How does the Noise Reduction work?

NR depends on correlation of the present input with previous input. The 
system does not actually provide Noise Reduction; it provides Signal 
Selection. In other words, its default is to pass nothing at all. It has 
to believe there is a signal present, and then it builds a filter, or 
set of filters, around the spectral components of the signal it thinks 
is there.
Random noise has no correlation, voice has moderate but not perfect 
(unless you whistle a pure tone) and CW has excellent correlation.  As a 
result, noise is heavily suppressed (no filter is built to pass it), 
voice is partially suppressed (hence it needs some additional gain to 
compensate for this effect so the same AF level will produce about the 
same audio level with a moderate S/N speech signal) and CW is hardly 
suppressed at all (hence it does not need any gain boost).
NR is not recommended in Data Mode.  Data is already getting a matched 
filter in the demodulator. You might lose a few symbols as the NR 
settles around the signal, and it might suppress a very weak signal that 
you could otherwise copy.
NR in the end is intended for modes you listen to.
 >>>>>>>>>>>>>>>>>>>

Seems clear to me; I'm no expert (DSP 'dummy') but it tells me for one 
thing that adaptive dsp filtering is going to work better with cw than 
phone. There is more on it in 'Operating Tips' and somewhere Lyle gave a 
good explanation of the different settings available but I can't find it 
now - anyone know whether it's lurking somewhere on the web site?

Have fun (I am.....!)

-- 
73, Stewart Rolfe, GW0ETF (K3 #145)