On Sun, 30 Oct 2005 23:41:29 -0500, TRABEM wrote:
In general, no rf stage is needed (or desired).

In general, no rf stage has been designed into a receiver for a
quarter century. Hence touting it as a hallmark is rather pedestrian.

But, recovering the audio without DSP based software (usually
a sound card) is very difficult, needing large amounts of selective
audio filters slowly tailor the audio response to an appropriate
selectivity.

Even there, bi-quad active filters have been doing this for those same
25 - 30 years, and quite smartly too.

You need to return to basics a la Robert Pease who does a lot of
informational multimedia for National Semi these days. He properly
offers that so much that has been handed over to binary twiddling is
such a step backwards to accomplishing a job better handled in the
linear domain.

73's
Richard Clark, KB7QHC