Orban Optimod-FM 8300 Operating Manual page 71

OPTIMOD-FM DIGITAL
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
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
injection control until the injection equals 9% modulation.
If you wish to use the modulation reduction function anyway:
A) Navigate to S
B) Hold down the appropriate M
to set the amount of modulation reduction produced by the M
1 and M
R
EDUCTION
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
TO "5%" and
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
b) Using the N
corresponding to the GPI terminal you wish to program.
c) Hold down this button and turn the knob until you see
M . R
OD EDUCTION
P O
PX OWER
C
OMPOSITE
/ N / M
ETUP EXT ODULATION
ODULATION
R
ODULATION EDUCTION
M R
ODULATION EDUCTION
/ N / N
ETUP EXT ETWORK
button, scroll the screen until you see the button
EXT
as desired.
2
control on page 3-35.
FFSET
control(s). Then turn up the pilot
L
EVEL
R .
EDUCTION
R button and turn the knob
EDUCTION
2 functions.
M
ODULATION
to 5%. This will reduce your audio
2
&R / R
EMOTE EMOTE
INSTALLATION
ODULATION
R 1
EDUCTION
.
I
NTERFACE
or
M . R 1
OD EDUCTION
2-23