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FM Stereo Info (Re: Tech question)

     A good question, deserving a (hopefully) good
answer.  The difference between the signal strength or
coverage area between an FM mono and a FM Stereo
station is negligible.  For example, a 50,000 watt FM
station (mono or Stereo) will cover the same amount of
mileage.  It is only when you come to outer fringes of
that signal does the difference between mono and
Stereo seem to be more pronounced.  Before the car
manufacturers started installing "blending" circuits
that "mono down" the stereo signal to get rid of the
hiss (I hate these "blending" circuits with a passion
as they tend mono down the signal in a still strong
area), a Stereo signal would begin to hear hiss as you
leave the local coverage area.
     FM Stereo uses a subcarrier (38 kHz, L-R)
superimposed on the FM carrier with a 19 kHz pilot
tone to activate the Stereo decoder.  The signals will
get noisy and the Stereo light will begin to blink on
and off as you get further away.  In order to get a
good Stereo signal, you first need a strong mono
signal (the main carrier, or L+R).  The Stereo signal
is the first to go when you start leaving the normal
coverage area.  You should still get a useable mono
signal for several more miles before that too goes. 
     So, in answer to your question, Stereo does not
have any indirect bearing on the coverage of an FM
signal.  To tell you the truth, even on mono radios, a
Stereo signal has much more depth and crispness than a
mono one..... (IMHO).  So, there you are.  73!

-Peter Q. George
 Whitman, MA 

--- Marc Lemay <mmkc@mediaone.net> wrote:
> Does an FM mono signal travel better than an FM
> Stereo signal?  If so - why?
> Marc Lemay


Peter Q. George (K1XRB)
Whitman, Massachusetts
                           "Scanning the bands since 1967"

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