Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!cs.utexas.edu!uunet!littlei!reed!omen!caf
From: caf@omen.UUCP (Chuck Forsberg WA7KGX)
Newsgroups: sci.electronics
Subject: Re: Stereo vs. Mono: Q about AM Stereo
Keywords: AM,radio,stereo,mono,FCC
Message-ID: <755@omen.UUCP>
Date: 4 May 89 17:03:14 GMT
References: <4046@bgsuvax.UUCP> <1968@hp-sdd.hp.com>
Reply-To: caf@omen.UUCP (Chuck Forsberg WA7KGX)
Organization: Omen Technology Inc, Portland Oregon
Lines: 48

In article <1968@hp-sdd.hp.com> robert@hp-sdd.hp.com.UUCP (Robert Navarro) writes:
:   I'm not laughing at the person who asked for proof that stereo is better
:than mono because in one important way it's NOT. The signal to noise
:ratio for Stereo is lower than mono. This means the signal sounds more
:noisy for stereo. To see this just tune your FM radio to a station that
:barely comes in in stereo and then turn the stereo off. (This is why
:most FM receivers have the mono switch ! -- to allow weak stations to
:be better received.)

The CQUAM AM stereo system does reduce the effective listening
area due to a loss in s/n ratio and increased sensitivity to
interference.  Even so, CQUAM is not as bad as FM Multiplex
stereo in terms of s/n degradation.

The Kahn independent sideband AM atereo system does not reduce
a station's coverage area, and does not suffer from CQUAM's
platform motion problem.

ISB stereo systems are also used for "power side" operation, a
signal enhancement method that places most of the audio in one of
the sidebands to give a signal to noise improvement over conventional AM.
Since only a small amount of stereo effect can be used with Power Side,
one could say that even ISB AM stereo reduces s/n compared to the
optimal mono situation, one could say stereo reduces s/n, but that's
begging the point.

Some AM stations use Kahn stereo by day and Power Side by night
when they need max s/n.

:
:   Furthermore, AM is badly bandlimited. The baseband signal for AM is only
:5KHZ! Most music requires at least twice this for decent sound 
:reproduction. To include stereo into AM would require more bandwidth.
:And, unless you use single side band (which usually adds some noise 
:in practice) the 5Khz for the baseband signal now must be divided
:up into two channels for stereo. Can you imagine what a 2.5Khz bandlimited
:signal would sound like!!!!

Perhaps your junk radio has only 5 kHz b/w.  That's not a limitation
of AM.  The soon to be mandatory station filtering allows at least
a 10 kHz to 12 kHz audio freq response.

:
:So, while stereo AM may sound more like an original stereo music 
:recording, it will also sound noticably noisier than mono 
:no matter what AM stereo standard is picked. 

Essentially wrong.