There really is no such thing as a 'noise filter' - noise usually
occupies the whole band, so a noise filter would remove all of the
signal !
there is definitely such thing as a noise filter. i know i had a
couple dozen VSTs in my 'filter/noise' folder on windows...
whether they were noise-reduction filters (like you might see in
photoshop, or FFT based (take a snapshot of a quiet portion and use
as a convolution mask) depended on the plugin
The only thing you can do is remove the noise in those
parts
of the spectrum you don't want to hear.
For Morse, a bandpass will let through the tone you want and attenuate
for morse, theres plenty of ham-radio utils on linux..
for morse, you could easily resynthesize it as a pure sine-tone with a
simple pd patch, getting rid of all the noise..although a combination
narrow-bandpass and gate would work wonders (and be done w/ pure LADSPA)
you also might want to check out GNURadio. which allows you much more
control by not limiting yourself to the 'decoded' RF data as audio..
c