Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!iuvax!uxc!uxc.cso.uiuc.edu!m.cs.uiuc.edu!irwin
From: irwin@m.cs.uiuc.edu
Newsgroups: sci.electronics
Subject: Re: Stereo vs. Mono: Q about AM Stereo
Message-ID: <21000021@m.cs.uiuc.edu>
Date: 3 May 89 18:26:00 GMT
References: <4046@bgsuvax.UUCP>
Lines: 42
Nf-ID: #R:bgsuvax.UUCP:4046:m.cs.uiuc.edu:21000021:000:1984
Nf-From: m.cs.uiuc.edu!irwin    May  3 13:26:00 1989


/* Written  3:41 pm  May  2, 1989 by robert@hp-sdd.hp.com in m.cs.uiuc.edu:sci.electronics */
In article <4046@bgsuvax.UUCP> klopfens@bgsuvax.UUCP (Bruce Klopfenstein) writes:
>He wants "proof" that stereo is superior to mono.  You can laugh, but I have

>>   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!!!!

>>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. 

>>Robert Navarro
>>Hewlett Packard, San Diego

/* End of text from m.cs.uiuc.edu:sci.electronics */

In the above, Robert indicates that AM radio is restricted to 5KHZ.
The way I figure it, it is 10KHZ.

On the AM broadcast band, there is a station frequency every 10KHZ, starting
at 550 and going up in increments of 10 to 1600. If a station were at 760KHZ,
they would have space 5 below center frequency and 5 above center frequency
for their lower and upper sidebands. This is a total of 10 in width.

True, each sideband is limited to 5, so, they need to used single sideband
and gain 5MHZ in band width, they have the space there, it is just not
being utilized to the best advantage. SSB is still AM, I wonder if the
FCC would allow it? It would take several years to junk out all of the
old AM receivers, maybe 25, but, they would eventually disappear, and,
if you wanted the home radio to get either mode of transmission, you
may be inclined to upgrade sooner, as the SSB receiver has to reinject
the carrier locally, so demodulation can take place.


Al Irwin
irwin@m.cs.uiuc.edu