"R J Carpenter" wrote in message ...
"Steve Nosko" wrote in message
...

Low IF for reduced BW can be done in any radio, but size and Q
and frequency are not independent, so lower freq IF means bigger coils and
more "R", so "same Q - lower IF" is not that simple.

It must be a couple of decades since IF bandwidth depended on "real" IF
coils and their Q. Since then mechanical [ceramic] filters have set the
bandwidth of essentially all consumer radios known to me. OK there are now
a few high-end DSP-based radios. Those too-narrow IFs in today's AM radios
come from ceramic filters, not low freq IF.

A decent car radio in FM isn't anymore selective or sensitive than a
decent home stereo tuner or receiver in FM. The reason a car radio
sounds cleaner on weaker FM stations has more to do with the stereo
mpx circuit. All car radios have a circuit in the mpx circuit that
blends the stereo-to-mono and mono-to-stereo mode. When manually set
in FM mono mode on a home stereo the SNR is better than in stereo mode
on weak stations. The same holds true for an FM car radio. The only
difference is car radios don't have mono switches. Instead, internal
to the FM car tuner is a circuit that blends the stereo/mono mode so
when the car is in motion and signal strength is varying all over the
place the tuner isn't constantly and abruptly switching between stereo
and mono. Also in this blend circuit is an RC time constant that
"smooths" out the blending action. So somewhere a happy medium is
established and a relative slowly changing SNR takes place slow enough
to be unnoticable. In other words, if far enough from a station the
car radio isn't in 100% stereo mode. It's some where between stereo
and mono. If you're right near the broadcast antenna SNR is best as
well as full stereo separation.