Advertisement
a)
Standard Control Setup:
Record the
normal
settings
of
the
controls
so
that
they
can
be
reset
after
the
measurements
have
been
completed.
Then
set
the
controls as follows:
L AND R INPUT ATTENUATORS:
CLIPPING:
+
9
RELEASE TIME:
10
BASS COUPLING:
10
GATE THRESHOLD:
HF LIMITING:
LOUDNESS CONTROLLER:
DEFEATED
b)
Skeleton
Proof:
This
should
be
performed
for
both
left
and
right
channels.
1)
Place both PROOF/OPERATE switches in PROOF.
2)
Connect
a low- distortion audio oscillator to the OPTIMOD-TV
input. Set the
frequency to 50Hz, and adjust the oscillator output level to produce 3.3V rms at
the OPTIMOD-TV TEST JACK.
3)
Adjust the appropriate OPTIMOD-TV OUTPUT ATTEN until
3.3V rms is also
produced
at
the
MAIN
OUTPUT [ between (+)
and
circuit
ground,
as
described
above].
The TEST JACK now
serves
as the PREEMPHASIZED OUTPUT,
and the MAIN
OUTPUT serves as the DEEMPHASIZED OUTPUT.
4)
Frequency Response:
Reduce
the
oscillator
output
level
by
20dB ( to
avoid
overloading
the
OPTIMOD-TV
circuitry
at
high
frequencies
because
of
preemphasis). Connect the NdeD set to the OPTIMOD-TV MAIN ( DEEMPHASIZED)
OUTPUT.
Without
changing
the
oscillator
output
level,
measure
the
frequency
response at 50, 100, 400, 1000, 5000, 10,000, and 15,000 Hz. The response should
be better than + 0.75dB with reference to lkHz.
(A
more accurate frequency response evaluation
can be
performed by sweeping
the system with a test set like the Tektronix 5L4N Spectrum Analyzer/Tracking
Generator. If the station has such equipment, see paragraph 6.c of Appendix E
for further information.)
5)
Distortion:
The
deemphasized
THD
should
now
be
measured
at
100%
modulation ( corresponding to
3.3V rms at
the TEST JACK).
The level
is
most
conveniently set
for each frequency to be
measured by adjusting the oscillator
OUTPUT ATTEN to produce a reading of "+ 3VU" on the OPTIMOD-TV VU meter
in
its L ( or
R) FILTER
OUT
switch
position.
Alternately,
you
can
adjust
the
oscillator at each frequency to produce the level at the MAIN OUTPUT tabulated
in TABLE D-1 below.
TABLE D-1
50Hz
3.30V
100Hz
3.30V
400Hz
3.24V
lkHz
2.99V
5kHz
1.29V
10kHz
0.685V
15kHz
0.462V
D-2
Advertisement
