[Earl Kiosterud]

"Robert Orban" wrote in message
...
In article ,
says...



"SFTV_troy" blabbed:
... this new receiving technique would not improve the sound
(it would still be limited from 100-6000 hertz), but would only reduce
interference.

At least in the States, AM & FM broadcasting is limited to 50 Hz to 15KHz.

There is no low frequency limit for either AM or FM; 50 Hz was the minimum
performance standard that would meet the now long-deleted FCC Proof of
Performance measurements.

The effective HF limit on FM is about 18.5 kHz; this leaves a +/- 500 Hz guard
band for the stereo pilot tone. Again, 15 kHz was the minimum spec that would
pass a Proof of Performance, not a limit on bandwidth.

Currently, the legal FCC-mandated HF limit on AM in the US is a hair less than
10 kHz, which almost completely protects second-adjacent stations from
interference. This was changed around 1990 as a result of work done by the
National Radio Systems Committee (NRSC). More recent work by the NRSC has
indicated that 7 kHz is probably the optimum compromise between causing
interference and loss of audio quality on typical AM radios (which are down 3
dB at about 2.6 kHz). However, limiting bandwidth to 7 kHz is voluntary.


Robert,

Was AM radio ever allowed audio to 15 KHz? I read many years ago that it was, perhaps
before the NRSC recommendation was adopted by the FCC. I presumed that the stations either
were allowed to overlap 5 KHz (doubtful), or that stations in a given area were separated by
at least 30 KHz.
--
Regards from Virginia Beach,

Earl Kiosterud
www.smokeylake.com