Mxsmanic wrote:
Dan Luke writes:

******** again. I have a radio that does actively remove noise--it
has a button to turn the feature on and off, and it works quite well.

What kind of noise does it remove, and how does it distinguish noise
from signal?

One proven way to reduce noise is to repeat the signal N times and the
receiver adds up the repetitions and eventually the noise averages to zero
while the signal does not. Of course this is not what is done in practice
in real communications.

(I once wrote software for a Tunneling Electron Microscope (TEM) that did
the above - the target object is repeatedly scanned and the scans are
basically averaged - the noise falls off. Though IIRC, the amplitude of the
noise drops by a factor of 1/sqrt(N) for N scans. I'm too lazy to look it
up so that might not be the correct factor.)