[BC] Analog AM bandwidth: tail wagging the dog?

[Kevin Tekel]

Radio World reports that the NRSC has revised its voluntary standards to
accomodate reduced-bandwidth analog AM audio, and has also officially
retired the failed "AMAX" wide-bandwidth AM Stereo receiver guidelines:

http://www.rwonline.com/pages/s.0101/t.8737.html

Based on a study of 30 receivers, the NRSC recommends an analog AM audio
bandwidth of 7 kHz.  But what if they did a study of FM reception on car
radios?  Would they recommend FM stations drop to mono because it would
improve coverage and because the stereo-blend in most modern car radios is
so aggressive that the signal practically needs to be melting the antenna
to be heard in full-separation stereo?  Not to mention that many radios no
longer have an "ST" indicator for FM?

Anyway... for the sake of argument, let's say that 15% of AM radios in use
today have some kind of useful audio response above 7 kHz.  (Which I think
is actually a low guess, since AM tuners are being made cheaper than ever
today, and cheaper means less selective, and thus wider bandwidth.)
The NRSC is telling us we should forget about that 15% and just cater our
broadcasts to the majority of receivers.  In that case, MTS TV Stereo
sound should also be abandoned, because it is fact that only about 15% of
analog TV sets in use today are stereo -- and besides, DTV will make
analog stereo TV obsolete anyway, just as IBOC will make wideband analog
AM obsolete.




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