I asked about these radio functions in a newsgroup message not long
ago and would like to thank those who responded. Very helpful
information. I think I've been able to see the practical use of these
functions while listening tonight. I tuned in a frequency only to
hear an annoying whistle. Since the interference was very close to the
carrier I wasn't able to bring the filter in small enough. I was
able to get rid of this sound with the notch filter and the listening
value was dramatically increased. I could have shifted the IF up to
lose the interference but would have altered the sound - not so
appealing. On a second occasion I was trying to dig out a signal that
had only a low S/N and was only 5kHz away from a strong signal. I was
able to shift the freq up and away from the higher sig. Not great
audio but I could get an ID. Fun stuff.