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Path: utzoo!linus!philabs!seismo!rochester!rocksvax!dave
From: dave@rocksvax.UUCP (Dave Sewhuk)
Newsgroups: net.audio
Subject: Re: ``Best'' classical stations
Message-ID: <1188@rocksvax.UUCP>
Date: Fri, 13-Jan-84 12:30:25 EST
Article-I.D.: rocksvax.1188
Posted: Fri Jan 13 12:30:25 1984
Date-Received: Sun, 15-Jan-84 00:07:46 EST
References: <360@whuxk.UUCP> <777@hou5d.UUCP>
Organization: Xerox, Rochester, N.Y.
Lines: 49

All radio stations have at minimum 2 pieces of processing equipment,
one is the 75uS pre-emphasis and the other is the peak deviation limiter.
I am not sure about the 75uS pre-emphasis curve, but a limiter is required
by FCC regulations and assures the station will not splash into the adjacent
channel.   The pre-emphasis is a simple RC filter and helps
to eliminate channel "hiss".  Some stations use excessive compression, clipping
is a form of compression, listen to Roch. local FM station WHFM to hear 
heavy clipping, I like to call their method the "Schmidt Trigger" method.

Someone earlier asked about how good a CD could sound on an FM station.  That
is a really hairy question.  FM stations are allocated 150 Khz of bandwidth
for the L/R information.  In FM modulation bandwidth is consumed up in 2
ways, by making things "louder" and by putting higher frequency information
within the channel.  The mathmatics that allows you to calculate a giving
amount of bandwidth for X amount of audio power @ Y frequency always 
produces an infinite series in frequency.  So for any given modulation
there is an infinite series of sidebands that make up that signal! So
some distortion is inevitable, but usually it is very low, seeing the
total power of these signals is a very, very small percentage of the total power
for the stuff that is usually transmitted.

A stereo FM signal consists of a <18 Khz channel of L+R information
transmitted in FM and a Double sideband suppressed carrier L-R channel
of <18 Khz on a 36 Khz "carrier".  That "carrier" is an 18 Khz FM
modulated tone doubled in frequency to get 36 Khz.  So the upper
frequency limit is 18 Khz no matter what you do because of that 18 Khz
tone transmitted to get you the stereo information.  It would take an
infinite pole filter to get you response to 18 Khz.  15 Khz is usually
the place where designers start rolling off high frequencies so you
won't hear much of the 18 Khz tone. And if the high frequency stuff is
loud you distort it a bit due to clipping of the side bands to keep
the FM channel bandwidth within legal limits.

>From the experiences I have heard here in Rochester on WXXI, which I feel
is one of the best classical stations in the country (I had to say it),
playing a CD and digitally mastered analog disk of the same
material, is that the CD sounds a little better, crisper tones, etc than
the analog counterpart.  The test was to play the same selection and
randomly switch between the two machines a few times without telling
which machine was which until the end of the selection.  

In conclusion the CD due to its more faithful reproduction of lower
frequencies, and lesser noise, should sound better in those departments,
plus no dust/scratch noises!!
-- 
Dave

Arpa: Sewhuk.HENR@PARC-MAXC.ARPA
uucp: {allegra, rochester, ritcv, ritvp, amd70, sunybcs}!rocksvax!dave