Orban OPTIMOD-AM 9300, Руководство по эксплуатации

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2-26
INSTALLATION ORBAN MODEL 9300
10. Set output and configuration level.
This is a preliminary level adjustment. Later in this installation procedure, you
will set 9300 for the highest modulation level that your facility can produce. If
your transmission facility proves to have overshoot, tilt, or ringing when you test
it in step 11 on page 2-27, you will have to go through the Transmitter Equalizer
adjustment procedure, which starts with step 12 on page 2-27.
A) Make sure that the transmitter is turned off.
B) Turn on the 400Hz calibration tone. To do this:
a)
Navigate to
S
ETUP
> T
EST
.
b) Set the
M
ODE to
S
INE .
c) Press the
N
EXT key twice.
d) Set
S
INE
/T
RNGL
M
OD
to 50%.
e) Press
N
EXT
.
f) Set
S
INE
/T
RNGL
F
REQ to
400 H
Z .
C) Set modulation.
If you plan to modulate asymmetrically, you must leave headroom for the
positive peaks. For example, you must set the
DO 100%
control lower
than –2.0 dBFS to support 125% modulation.
a) Set to its minimum level the
AO
X
100%
or
DO 100%
control associated with
the output you are using to drive the transmitter under adjustment.
b) Turn the transmitter on.
c) Set the control you adjusted in step (a) to produce 40% modulation.
This leaves 2 dB of headroom to accommodate overshoot in the transmis-
sion plant. This should suffice for most facilities.
The most accurate way to set this control is by observing a modulation
analyzer or oscilloscope connected to your transmitter.
D) In
S
ETUP
> T
EST , set the
M
ODE to
O
PERATE .
E) Drive the 9300 with program material and observe the negative modulation
level. Trim the
AO
X
100%
or
DO 100%
control associated with the output you
are using to drive the transmitter under adjustment so that you observe 99%
modulation on negative peaks.
Spend time observing the modulation with different program material. If
you see the peak modulation level vary significantly depending on pro-
gram material, the 9300’s transmitter equalizer can often improve this
situation.
Note that if you set the processing up for asymmetrical modulation
(which is done by editing the active System Preset) and you observe neg-
ative peaks that are higher than positive peaks, you can correct this by
changing the setting of the
P
OLARITY control, located next to the
AO
X
100%
or
DO 100%
control in the active System Preset.