This is a good answer but tells only 60% of the story. In the late
60s-early 70s AM radios started to be made with deeply restricted
bandwidth--some as restricted as 3.5KHz. The Hi-Fi magazines stopped
printing AM tuner bandwidth in their reviews, so it remained an industry
secret. Purchasers thought the lousy sound was the stations' fault, but
it was the fault of their newer radios. Why? Because as the FCC
allowed new stations on the air, they were "short spaced". Stations on
the second adjacent band frequency were too close together and their
high audio frequencies overlapped. If you were listening to a station
on 660 you would sometimes be able to hear the splatter of highs from a
station at 680, and the listeners to the 680 station would hear the
highs from the 660 station. Reducing the bandwidth of the receiver
eliminated that problem by eliminating ALL high audio frequencies. This
problem could have been solved by just limiting the bandwidth of
receivers to perhaps 9KHz, but as the AM band became more crowded there
started to be problems with reception from adjacent channels, so the
receiver manufacturers reduced bandwidths to 3.5 or 4.5 Khz. To counter
the dull sounding receivers, stations started boosting high frequencies
using such crap as the Aphex Aural Exciter. That increased the
splatter, and made those stations sound even worse on GOOD radios--such
as those made before 1965.

In the mid 1980s the broadcasting industry came up with a solution. In
addition to the development of AM-Stereo, the broadcasters suggested to
the FCC and the receiver manufacturers, that if the radios would be
REQUIRED to have a bandwidth of perhaps 7.5 to 9 KHz, the stations would
restrict their audio to 9.5 or 10 KHz. That would end second-adjacent
splatter even on wide-band receivers. But this was in the era of Ronald
Reagan and the free-marketplace theory, and he had appointed as the FCC
chair a thoroughly evil character named Mark Fowler. Fowler's FCC had
already destroyed AM-Stereo by allowing the "marketplace" to decide on a
system instead of selecting a specific standard as had been done with
TV, Color TV, and FM Stereo, and now they decided to allow the bandwidth
solution to be voluntary, not regulated. The result was that no radio
station would voluntarily restrict their audio if the receiver
manufacturers wouldn't widen theirs. The radio station industry tried
to entice receiver manufacturers by a certification program called AMax,
but only Denon made a tuner to AMax specs, and Sony made a portable and
a walkman to AMax specs. The Sony's, by the way, are the only radios
ever sold in the U.S. that could receive all 5 AM Stereo systems.

When Bush Sr. came into office, the Dennis Patrick FCC dropped one shoe
by putting the AM transmitter high audio frequency restriction into
place by law. This is called NRSC. They still hoped that receiver
manufacturers would see the improvement and widen their bandwidths. The
hope also was that they would start making AM Stereo receivers. I
actually had an AM Stereo radio in a Nisson Maxima once. I only
discoverd that when the AM Stereo light lit up once!!! The car manual
didn't mention the feature.

This is a long answer, but should explain why AM radio sounds like
crap. It actually also explains why the PROGRAMMING also is crap
because the demise of music on AM and the growth of talk on AM evolved
during the same era as the decrease in receiver quality. It also was
the same Regan-Fowler FCC which eliminated all Program Logging
requirements, which eliminated all station public interest
responsibility requirements such as comparing "promise vs. performance",
and then without any programming ethical standards in place they
eliminated the Fairness Doctrine which opened the floodgates to the
unethical. Then Clinton was convinced to allow almost unlimited
ownership of multiple radio stations which led to unlimited
concentration of ownership, coupled with new technical standards allowing
"unattended" operation of stations without any human being needing to be
present at any time, and you have the unlistenable radio industry that
plagues us now.

Mike Biel [log in to unmask]

Bob Olhsson wrote:
>> -----Original Message-----
>> From Tom Fine: ...what happened to modern AM
>> sound? Is it the broadcast itself
>> or modern AM radios?
>>
>
> Both!
>
> AM bandwidth used to be restricted only by interference with other
> broadcasters. The commonly cited 5k bandwidth specification was only the
> minimum bandwidth that the FCC required. Response to 13kHz. was not uncommon
> for many of the larger stations although not all radios had the bandwidth
> switches that were required to avoid noise problems picking up more crowded
> stations. On top of that the signal wasn't crushed by signal processing and
> there were signal to noise and distortion mandates stations were required to
> meet. "Broadcast quality audio" was considered a high compliment during the
> 1950s!
>
> Unfortunately a bandwidth mandate was put in place in 1989 that reduced
> maximum bandwidth to 10kHz. Today most FM radio sounds worse than AM radio
> did during the '60s. I'm often left wondering if the broadcast and consumer
> electronics industries don't have some kind of a death wish.
>
> Bob Olhsson Audio Mastery, Nashville TN
> Mastering, Audio for Picture, Mix Evaluation and Quality Control
> Over 40 years making people sound better than they ever imagined!
> 615.385.8051 http://www.hyperback.com http://www.thewombforums.com
>
>
>