[Elecraft] K3 and Preamp

[Jim Brown]

On Sat,9/6/2014 2:28 PM, W2RU - Bud Hippisley wrote:
> I believe that whether one observes monotonic improvement in ability to decipher the intelligence carried in a very weak signal as one reduces receiver BW will be a function of_how_  the BW is narrowed in the various electronic circuits and/or digital algorithms, as well as a function of our own individual hearing characteristics.

Yes. Especially if the noise is impulse noise, ringing in the filter 
skirts can make copy more difficult for me if I set the bandwidth too 
narrow. This is, of course, strongly dependent on the shaping of the 
filter.

 From Psychoacoustics (the science of how the human ear-brain 
combination works), we know that we process sound in narrow chunks of 
bandwidth called "critical bands." The ear tends to process sounds 
within that band together, so when the filter gets too narrow, the 
filter skirts fall with the critical band and ringing begins to obscure 
the desired signal. The width a critical band varies with the sound 
spectrum, and is in the range a 1/3 octave to 1/6 octave. An octave is a 
2:1 ratio of frequency.

73, Jim K9YC