Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!uflorida!gatech!mcnc!unccvax!dya
From: dya@unccvax.UUCP (York David Anthony @ WKTD, Wilmington, NC)
Newsgroups: sci.electronics
Subject: Re: Stereo vs. Mono: Q about AM Stereo
Message-ID: <1487@unccvax.UUCP>
Date: 4 May 89 18:26:57 GMT
References: <4046@bgsuvax.UUCP> <21000021@m.cs.uiuc.edu>
Organization: Univ. of NC at Charlotte, Charlotte, NC
Lines: 41

In article <21000021@m.cs.uiuc.edu>, irwin@m.cs.uiuc.edu writes:
> 
> /* 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:

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

	However, the allocations plan ensures that there is at least a
20 dB carrier to carrier ratio for the first adjacent channel, not
counting the tuner's rejection (assuming you are talking about the
5 mV/m city grade signal of the desired station vs. 0.5 mV/m
protected contour of the next station.) In reality, the protection
is much more. 10 kHz removed stations may not overlap their 500 uV/m
contours.

> Why not SSB?

	Actually, there is a product which you can buy and is street
legal that is the next best thing to SSB, called a "Power-Side." This
device transmits the carrier and **one** sideband using ordinary
AM transmitters.

	The use of SSB+carrier to eliminate AM interference is at least
as old as 1953 or so, when there was much work in this area.  Leonard
Kahn advanced this idea originally to deal with the (then unbelieveably
nasty) harmonic radiation from television receiver horizontal oscillators.
The local station would choose the sideband which fell between horizontal
frequency harmonics.  I don't know of two co-channel AM stations who
have used Power-Side to eliminate interference, although there are 
10 kc removed AM stations who have installed them.

	Since the Power-Side is essentially an STR-87 Kahn exciter with
one channel muted, it is indeed type accepted and legal for use in your
AM station. There is no law which says you can't transmit just the left
or just the right channel.

	Score another round for Kahn ISB.....

York David Anthony
DataSpan, Inc