[BC] Seedy Quality in IBUZ Ads

[Mark Humphrey]

On 8/26/06, Richard Fry <rfry at adams.net> wrote:
>
> If HD FM sounds better than analog FM, isn't that related at least in part
> to the relative distortion of the modulation processors used to feed the FM
> analog and HD exciter inputs?

That's exactly the problem -- most FM processors must employ some form
of clipping to maintain high legal modulation, as necessary to
maximize the audio signal-to-noise ratio at the receiver.  To me,
clipping is sort of like capitalism -- it has a lot of drawbacks, but
I guess it's the best alternative we've found so far!

Most FM processors can be set up to eliminate clipping, and the
pre-emphasis limiting can also be defeated.  However, if the output is
also set to keep peak modulation within legal limits, the "apparent"
noise floor on a typical receiver will increase *at least* 10 dB, and
with some program material as much as 15 or 20.  This wouldn't be a
major problem if all receivers were fed a nice, strong,
dead-full-quieting signal, but sadly that's not the case in the real
world.

When I was attending high school near Syracuse, back in the early
'70s, the local 107.9 was a "purist" classical station called WONO.
They used no processing whatsoever -- the studio console fed directly
into a pair of equalized phone lines, which fed the stereo generator/
transmitter several miles away -- which meant their modulation
(including stereo pilot) typically hovered around 15 to 25%.   With an
outside antenna and high-quality tuner, their signal could sound
nearly as quiet as the recording --- but on many portable receivers or
car radios, the background noise was quite objectionable.

Nice idea in theory, but it just didn't work in practice.

Mark