[Elecraft] K3 and Noise Reduction

[David Woolley (E.L)]

Tom Wylie wrote:
> Is it possible to get noise reduction working when in Data mode like
> RTTY?

How would data reduction work in such modes and, more importantly, why 
are those techniques not already being used in your data terminal?

Real noise can never be reduced; it is random, and therefore impossible 
to predict.  What I think the K3 noise reduction may be doing is:

- automatic interference reduction, by automatically notching out 
constant carriers - but a marking RTTY signal looks like a constant 
carrier and would also be removed by this;
- squelching when there is no speech like signal;
- selectively reducing gain at frequencies which don't have strong 
spectral peaks from the speech.

The latter two reduce subjective noise, but are only valid for speech. 
They work because speech is a relatively inefficient user of bandwidth, 
but has a lot of redundancy.

The best way of getting rid of interfering carriers is to use a narrow 
passband, either at IF, or in the terminal unit and the best way of 
mitigating random noise is by using a discriminator that is well matched 
to the desired modulation.
> 
> Tom
> GM4FDM
> 


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David Woolley
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