On Wed, 21 Nov 2007 10:13:26 +0000 (GMT), Jim Lesurf
wrote:

Just to let people know that I have now put up a webpage on the effects of
finite bandwidth on the distortion levels for FM audio broadcasts. Can be
found on my audiomisc site.

The page combines the content from an earlier HFN article with some extra
material I produced a while ago when discussing this issue on uk.rec.audio.

Slainte,

Jim

Just made me think back to my "Ultimate tuner" I built back in the
late seventies when FM stations were over 2MHz apart. I built it with
a very wide, linear phase IF filter to prevent exactly this kind of
distortion. I don't have it any more, but if I did, it would no longer
work because of in-band interference.

Actually, now I think of it, the phase response of the IF filter is
also important here. Square, steep sided filters would seem to be the
best choice, but they tend to have a huge group delay wiggle as you
approach the corners, so you do need to compromise.

d

--
Pearce Consulting
http://www.pearce.uk.com