Orban 8300J, Operating Manual

Page: 71 / 280

OPTIMOD-FM DIGITAL INSTALLATION
2-23
and observe the peak deviation produced by the program material. The
overshoot is the amount (in dB) by which the deviation with program
material exceeds

75 kHz deviation.
See the notes on the M
PX
P
OWER
O
FFSET
control on page 3-35.
21. Set up modulation reduction to compensate for subcarriers, if needed.
In the United States, F.C.C. Rules permit you to add 0.5% modulation for every
1% increase in subcarrier injection. For example,
if your subcarrier injection to-
tals 20%, you can set the total modulation to 110% (

82.5 kHz deviation). The
8300 has the ability to reduce audio modulation to compensate for subcarriers.
The advantage of using the modulation reduction function is that the pilot injec-
tion stays constant when the audio modulation is reduced. However, using the
modulation reduction function is slightly inconvenient because it requires pro-
gramming and activating at least one 8300 GPI input.
If you have the same sub-
carrier injection at all times , a more convenient alternative is to set the desired
modulation level by using the
C
OMPOSITE
L
EVEL
control(s). Then turn up the pilot
injection control until the injection equals 9% modulation.
If you wish to use the modulation reduction function anyway:
A) Navigate to
S
ETUP
/ N
EXT
/ M
ODULATION
R
EDUCTION
.
B) Hold down the appropriate M
ODULATION
R
EDUCTION
button and turn the knob
to set the amount of modulation reduction produced by the M
ODULATION
R
EDUCTION
1
and
M
ODULATION
R
EDUCTION
2
functions.
You can program these to be activated via any rear-panel GPI input, or by
the 8300’s clock-based automation.
When both modulation reduction functions are active, the modulation
reduction is the sum of their settings.
To comply with FCC Rules, set the modulation reduction to one-half the
injection of the associated subcarrier. For example, if your subcarrier in-
jection totals 20% from two 10% subcarriers, set
M
ODULATION
R
EDUCTION
1
TO
“5%” and
M
ODULATION
R
EDUCTION
2
to 5%. This will reduce your audio
modulation to 90% (100% – 5% – 5%). When you add back the 20%
modulation due to the subcarriers, you get the required 110% total
modulation.
The Modulation Reduction function is active as long as signal is applied
to its associated GPI input.
C) Program the GPI input(s).
a) Navigate to S
ETUP
/ N
EXT
/ N
ETWORK
&R
EMOTE
/ R
EMOTE
I
NTERFACE
.
b) Using the N
EXT
button, scroll the screen until you see the button
corresponding to the GPI terminal you wish to program.
c) Hold down this button and turn the knob until you see
M
OD
. R
EDUCTION
1
or
M
OD
. R
EDUCTION
2
as desired.