Orban OPTIMOD-FM 8600S, Operating Manual

Page: 88 / 354

2-32
INSTALLATION ORBAN MODEL
C) You can use either program material or tone to set your output level (and
thus, your on-air modulation). If you want to use tone, turn on the 100 Hz cal-
ibration tone and set it to 91%.
The tone is calibrated with reference to the composite output and as-
sumes 9% pilot injection: 91% + 9% = 100%. The peak level at the ana-
log output is now the same as the maximum peak level under program
conditions when the
AO P
RE
-
E
control is set to
P
RE
-
E
.
This peak level should agree with the setting of the
AO 100%
control.
AO
100%
is equal to the RMS value of a sinewave whose peak value is equal
to the maximum peak output of the analog output under program con-
ditions if the
AO P
RE
-
E control is set to
P
RE
-
E
.
For example, when
AO P
RE
-
E
= +10.0 dBu, the peak output is 5.77 volts, which corresponds to a sin-
ewave whose RMS values is 4.08 volts. Program material peaks of fre-
quent recurrence will not exceed 5.77 volts peak.
See step (9.H) on page 2-30 for instructions on how to turn on the cali-
bration tone and set its frequency and level.
D) Using the
AO 100%
button, set the desired analog output level corresponding
to 100% modulation, using units of dBu (0 dBu = 0.775 Vrms).
The most accurate way to set this control is by observing a modulation
analyzer connected to your transmitter.
If you have (inappropriately) set
AO S
OURCE
: M
ONITOR
in step (B) above,
the peak level will not be well controlled because no peak limiting has
been applied to this signal. This will also be true if you have defeated the
final clipper (step 6 on page 2-29).
If you are using program material, make sure that the program material
is loud enough to produce peaks of frequent recurrence that hit the
8600S’s peak limiting system, thereby defining the maximum peak level
that the 8600S will produce. In the U.S., we recommend using 900

s peak
weighting on the peak modulation indicator, as permitted by F.C.C. rules.
This will cause the monitor to ignore very low energy overshoots and will
result in the highest peak modulation permitted by law.
In other countries, use a peak-indicating instrument as specified by the
regulatory authority in your country.
If you are required to implement the average modulation limits specified
by ITU-R 412-9, you may seldom see peaks hitting

75 kHz deviation. In
this case, we advise you to set the output level by using the 8600S’s ref-
erence 100Hz tone.
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 totals 20%, you can set the total modulation to 110% (

82.5
kHz deviation). This implies that you must set the 8600S’s composite out-
put level for the equivalent of 90% modulation, not counting the subcar-
riers. (90% + 20% = 110%.) The pilot injection will thus be about 8%
modulation instead of the desired 9%. Adjust the
Setup > S
TEREO
E
NCODER
> Next > P
ILOT
L
VL
control as necessary to produce 9% modu-
lation (

6.75 kHz deviation). This will ordinarily require you to set the
P
ILOT
L
VL parameter to “10%.”