Orban OPTIMOD-FM 8700, Operating Manual

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4-12
MAINTENANCE ORBAN MODEL 8700i
NOTE: The recommended Belar monitor is the only instrument we have
encountered that can accurately measure the performance of the 8700i’s
stereo encoder. With most older-technology monitors, you will be meas-
uring the performance of the monitor, not the 8700i’s encoder. Of
course, we have not evaluated every monitor on the market.
B) Navigate to the 8700i’s S
YSTEM
S
ETUP
and choose T
EST
M
ODES
.
C) Choose
T
ONE
. Set the test tone parameters as follows:
Frequency 400 Hz
Mod Level 91%
Mod Type L+R
Test: Pilot On
D) Navigate to
I
NPUT
/
OUTPUT
and then to screen
I
NPUT
/O
UTPUT
> C
OMPOSITE
. Set
the
O
UTPUT
1 L
EVEL
to make the stereo monitor read
100%
total modulation.
E) Navigate to the 8700i’s S
YSTEM
S
ETUP
and choose T
EST
M
ODES
.
F) Measure the L–R level on the stereo monitor at several frequencies, in units of
dB below 100% modulation. This is the main channel to subchannel crosstalk.
It should not exceed –70 dB, 50-15,000 Hz.
G) Set the M
OD
. T
YPE
to L
–R
. Measure the L+R level on the stereo monitor at sev-
eral frequencies, in units of dB below 100% modulation. This is the subchan-
nel to main channel crosstalk. It should not exceed –70 dB, 50-15,000 Hz.
H) Set the M
OD
. T
YPE
to LEFT . Measure the Right level on the stereo monitor at
several frequencies, in units of dB below 100% modulation. This is left into
right stereo separation. It should not exceed –55 dB, 50-15,000 Hz and will
typically be –60 dB or better.
I) Set the
M
OD
. T
YPE
to
RIGHT
. Measure the Left level on the stereo monitor at
several frequencies, in units of dB below 100% modulation. It should not ex-
ceed –55 dB, 50-15,000 Hz and will typically be –60 dB or better.
J) Set the
M
OD
. T
YPE
to
L
–R
and the
F
REQUENCY
to
5000.0 H
Z
. Measure the 38
kHz subcarrier suppression on the stereo monitor. It should not exceed –65 dB.
K) Measure the Pilot Modulation on the stereo monitor. It should read 0%.
L) Set the M
OD
. L
EVEL
to 0.0%. Measure the de-emphasized noise at the left and
right outputs of the stereo monitor. It should not exceed –80 dB below 100%
modulation.
M) Repeat steps (C) through (L) for the 8700i’s
COMPOSITE OUTPUT 2.
N) Measure pilot tone injection: Using the stereo monitor, verify that pilot tone
injection is between 8% and 10% modulation. If it is outside these parame-
ters, it can be adjusted by navigating to
I
NPUT
/
OUTPUT
and then to screen
I
NPUT
/O
UTPUT
> C
OMPOSITE
. Adjust
P
ILOT
L
EVEL
as necessary.
O) If the measured pilot level varies by more than a few tenths of percent from
the pilot level indicated, this indicates there may be a problem elsewhere—
either in your measuring setup, or with the 8700i.