Orban OPTIMOD-FM 8500S, Operating Manual

Page: 87 / 335

OPTIMOD-FM DIGITAL INSTALLATION
2-31
Monitor: If you do not need the 8500S’s analog output to drive a trans-
mitter, you may configure it to receive the output of the multiband com-
pressor before peak limiting. This signal is suited for driving headphones.
The input/output delay is approximately 3-8 milliseconds (depending on
the setting of
AGC C
ROSSOVER
T
YPE
)
. Even though normal 8500S presets
have a delay of about 15 ms, which most DJs, announcers, and presenters
can learn to use without discomfort (although they may need some time
to become accustomed to it), the low-delay output will cause less bone-
conduction comb filtering. However, in most cases, the low-delay output
will not be necessary to ensure adequate talent comfort.
The normal delay is 15 ms except for “UL” (ultra-low latency) presets,
which have approximately 5 ms delay.
If have set the source to Monitor, be sure to set analog pre-emphasis to
Flat. See step (A).
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
calibration 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
sinewave 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 2-29 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 2-28).
If you are using program material, make sure that the program material
is loud enough to produce peaks of frequent recurrence that hit the
8500S’s peak limiting system, thereby defining the maximum peak level
that the 8500S will produce. In the U.S., we recommend using 900
μ
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.