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5
SECTION 1
GENERAL
INFORMATION
1-1
GENERJl1L DESCRIPTION.
The Belar F
MS
- 1 Stereo Frequency and Modul
ation
Monitor (FCC l
rype
Approval Number
3-146).
Figure
1-
1,
is an all
so
l
id
state stereo
demodu
l
ator
designed
to
operate in conjuinction with
the
Belar
FMM
- 1 Frequency
and Modulati
on
Mo
nit
or
to
provide all
of
the
stereo
monitoring requi1rements outlined in P
art
73
of
the
Federal
Communications Commission's Rules
and
Regulations for
FM
radio stations engaged in multiplex stereophonic
programming. In addition,
the
FMS- 1 may
be
used as a
low distortion, low noise
FM
stereo demodulator for
driving audio monitors and associated
test
equipment. The
FMS
- 1, used
in
conjunction
with
the
FMM-1,
provides
complete monitoring and
test
functions
to
meet
the
daily
requirements for stereo monitoring and provides
addit
i
ona
l
facilities for proof-of-performance measurements and for
making
the
proper
tests
for
weekly and monthly
maintenance che,cks
to
insure maximum performance from
stereo transmitte1rs.
1- 2 PHYSICAL DESCRIPTION
The FMS-
1,
Figure 1-
2,
is
constructed
on
a standard 5¼ x
19-inch rack
mount.
Seldom used
contro
ls and
test
points
are located
under
the hinged
front
cover bar. Factory
adjustments are located wi
th
in
the
unit
and
on
the
back
panel.
The baseband input, power connections, and
monitor
outputs
are located
at
the
rear
of
the
FMS
- 1
chassis
on
individual connectors and rear terminal block as
shown
in
Figure 1- 3.
Th
e
FM
S- 1
is
completely solid state
utilizing all silicon transistorsfor long,
troub
le-free life.
The
individual circuits are constructed
on
three
military grade,
glass-epoxy, plated printed circuit boards. High reliability
industrial
and
military grade
components
are used
throughout.
1
-3
ELECTRICAL DESCRIPTION
The FMS- 1 is a solid state stereo demodulator
to
accurately demodulate a stereo composite baseband signal.
The
pilot phase regeneration system utilizes a phase
discriminator so
that
a null reading
is
obtained with
the
correct phase, allowing
the
phase
to
be regenerated
to
within ¼ degree. Various metering and testing provisions
are contained within
the
monitor
to
measure stereo
output
characteristics. These provisions include a 19 kHz
pi
l
ot
center
frequency
deviation meter; a peak reading
modulation meter; an average reading sensitive voltmeter; a
function switch
to
measure
total
modulation,
(l
+
R)
modulation, (L-R) modulation, pilot modulation, left
channel modulation, right. channel modulation,
38
kHz
Figure
1-1
