[BC] Mono Expands on the FM Band

[Mark Humphrey]

There was another drawback to Crosby's proposal, though.  He proposed
relatively high injection of a wide FM subcarrier centered at 45 kHz to
carry the L-R signal.  This would have required the L+R main channel to be
backed off about 6 dB, so the FCC considered the system somewhat
incompatible with existing mono receivers.    The approved GE/Zenith system
only requires about 1 dB main channel penalty to accomodate the pilot tone.

In his patent application, Crosby mentions that the L-R signal might only
acheive a 40 dB signal/noise ratio, but it probably wouldn't have degraded
as much as GE/Zenith's in fringe coverage areas.

Check the uspto.gov database for his patent, it's number 2,851,532.

Mark


On 1/17/06, nakayle at gmail.com <nakayle at gmail.com> 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
>
> On 1/16/06, R J Carpenter <rcarpen at erols.com> wrote:
>