Orban OPTIMOD-FM 8600S, Operating Manual

Page: 92 / 354

2-36
INSTALLATION ORBAN MODEL
country does not require this, leave the BS.1770 Safety Limiter off. It must be OFF
if you are transmitting HD Radio.
A) To use the BS.1770 Safety Limiter, assign the output source of one of the Digi-
tal Outputs to HD. See step (11.I) on page 2-34. We suggest using Digital Out-
put 1 to drive the digital radio transmitter.
To facilitate error-free loudness calibration through your transmission
system, activating the BS.1770 Safety Limiter changes the behavior of the
Digital Output 100%
P
EAK
L
EVEL
control. Normally, changing the setting
of this control changes both the loudness and peak level of the signal
appearing at the Digital Output driving your digital radio transmitter.
However, when the BS.1770 Safety Limiter is turned
ON
, the Digital Out-
put becomes the "Loudness Reference Output" and the Digital Output
100% P
EAK
L
EVEL control sets only the peak level, not the loudness . In this
case, the output loudness is always calibrated correctly with respect to
0 dBFS.
( Note: If both Digital Output 1 and Digital Output 2 are sourced from
“HD,” then Digital Output 2 becomes the “Loudness Reference Output”
instead of Digital Output 1.)
For example, setting the Digital Output 1 100% PEAK LEVEL control to
–3 dBFS always constrains the maximum peak level appearing at Digital
Output 1 to –3 dBFS, but changing the setting of the Digital Output 1
100% P
EAK
L
EVEL
control does not change loudness. This is because when
the BS.1770 Safety Limiter is turned ON, a second “hidden” gain control
is inserted before the input of the peak limiter. The gain set by the “hid-
den” control complements the setting of the Digital Output 1
100% P
EAK
L
EVEL
control. For example, when the Digital Output 1
100% P
EAK
L
EVEL
control is set to –3 dBFS, the “hidden” control adds 3 dB of gain before
the peak limiters to compensate for the 3 dB of loss that the
100% P
EAK
L
EVEL
control introduces after the peak limiters. Unless the peak limiters
produce gain reduction, this arrangement keeps the overall gain con-
stant from the input of the peak limiter to the Digital Output.
If the peak limiters produce enough gain reduction to reduce loudness
audibly, this gain reduction will cause the output loudness to be lower
than the setting of the
BS.1770 L
OUDNESS
C
ONTROL
T
HRESHOLD . This will
never occur with BS.1770 reference levels normally used in digital radio
(–18 LUFS) and digital television (–23 LUFS or –24 LUFS) because with
these reference levels, any peak limiting that occurs will be too brief to
audibly affect loudness.
Unless the
100% P
EAK
L
EVEL
control is set to 0 dBFS, this arrangement
causes the output loudness to change when you toggle the
BS.1770
S
AFETY
L
IMITER
control ON and OFF. In our example, the loudness will de-
crease by 3 dB when you set the
BS.1770 S
AFETY
L
IMITER
to OFF.
B) Navigate to the
Setup
>
I/O C
ALIB
> HD C
ALIB screen.
C) Set the
1770 L
IM control to
O
N
.
D) Set the
L
OUD
T
HR control to be equal to the target integrated loudness of your
broadcast as specified by the regulatory authority in your country.
E) After you have chosen a Processing Preset and adjusted it to your taste (step
13 on page 2-22, you must set the preset’s
HD L
IMITER
D
RIVE
to create the ap-
propriate amount of gain reduction in the BS.1770 Safety Limiter. Then save