DE@GODZILLA.SCH.SYMBOLICS.COM (Doug Evans) (03/14/86)
Date: Wed, 26 Feb 86 11:51 PST
From: Stoney Ballard <Ballard.pa@xerox.com>
A recent article in Video Review said that MTS is DBX encoded, hence has
a better S/N ratio than normal FM. If this is so, it implies that
either only the L-R band is DBX encoded and the normal sound band is
used for L+R as in standard FM (but is not DBX'd), or that the normal
sound band is not used for MTS, and two other bands are used instead.
If the latter case is true, it is apparently not necessary that the two
MTS bands be L+R and L-R, they could be just L and R separately. I am
neglecting the SAP band in this, of course.
Does anyone know which way this all works, or am I misunderstanding
something fundamental?
- Stoney Ballard
You're right in the first case. The L and R signals are mixed to
produce L+R (compatible mono) and L-R. Then the L-R signal is passed
thru a non-standard dbx circuit. The opposite process occurs in your
stereo TV - The L-R signal is first un-dbx'd and then the L+R and L-R
are mixed to produce the L and R signals.
There are some real good articles (with block diagrams) this month in
either Video or Video Review magazines on MST stereo. Addition of the
dbx circuits results in a quieter stereo signal over a larger area as
compared with FM stereo.