[BC] Mono Expands on the FM Band

[Robert Meuser]

Dave

You should discuss the vsb ssb FM stereo issue with Bob Orban as I know he has 
run the numbers and they are not really favorable. As for the implementation 
part, it sounds like Motorola AM Stereo.

R

Hershberger, Dave wrote:
>>  A old time engineer told me that the FCC made a major 
>>mistake in choosing
>>the GE/Zenith FM stereo system over the Murray Crosby system. 
>>  The Murray
>>Crosby system worked better and had much less hiss at low 
>>signal levels but
>>it was opposed by broadcasters because it interfered with 
>>67-Khz SCA music
>>services which was a major revenue source for FM broadcasters 
>>at the time.
>>A short-sighted decision I think in retrospect.
>>
>>-Nat
>>
> 
> 
> I heard a bit of folklore a long time ago about how GE/Zenith was chosen
> over Crosby.
> 
> Most people have heard of Occam's Razor. Well, the FM stereo system was
> chosen by Harold Kassens' razor.
> 
> One day Harold Kassens (then a FCC staff engineer) brought in his electric
> razor. He held it near the Zenith prototype FM stereo receiver and turned it
> on. The Zenith receiver went, "bzzzzt!" Then he held it near the Crosby
> receiver and turned it on. The Crosby receiver went, "BBBRRRRRRZZZZZTTTT!!!"
> (Much louder QRN than with the Zenith.)
> 
> Crosby protested that this wasn't a fair test, because the prototype
> receiver used a slope detector for L-R, and as such, it was much more
> susceptible to impulse noise. Crosby correctly pointed out that this was not
> a system problem, but rather an implementation problem that could be and
> would be solved. If he had time to replace the slope detector with a "real"
> FM detector, the impulse noise problem would go away.
> 
> Harold Kassens was not persuaded. So Kassen's razor tilted the odds in favor
> of GE/Zenith.
> 
> Crosby did have better stereo S/N, but as others have pointed out, it was at
> a cost of mono loudness and fringe and multipath effects that would cause
> noise bursts and distortion as the L-R subcarrier dropped below threshold.
> 
> L-R on a linear VSB or USB subcarrier at 19 kHz would be a much better match
> to the triangular noise spectrum of FM.
> 
> Dave Hershberger 
> Principal Engineer 
> AXCERA
> Tel: 530-272-HDTV (4388)
> Fax: 530-272-4505 
> dhershberger at axcera.com <mailto:dhershberger at axcera.com> 
> AXCERA. Axcessing the new era of digital communications. www.axcera.com 
> 960 McCourtney Road, Suite C, Grass Valley, CA 95949-7423
> 
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