Orban OPTIMOD-FM 8700, Operating Manual

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INTRODUCTION ORBAN MODEL 8700i
el, before de-emphasis, that the processing will produce, under any program, pro-
cessing, or setup condition (except when the processing is switched to
B
YPASS
). The
meter indication is not affected by the setting of the output level control.
Composite Output Level
The Orban 8700i Audio Processor controls instantaneous, absolute peak levels to a
tolerance of approximately

0.1 dB. Composite modulation is indicated in percent-
age modulation, absolute instantaneous peak indicating. 100% is calibrated to the
highest composite peak modulation level that the processing will produce, including
the pilot tone, under any program, processing, or setup condition (except when the
processing is switched to
B
YPASS
). 100% ordinarily corresponds to

75 kHz-carrier
deviation.
Note that if the 8700i’s subcarrier inputs are used, the meter will not indicate the
subcarriers’ effect on composite modulation because the subcarriers are mixed into
the composite signal in the analog domain, after the composite signal is metered.
Therefore, you must mentally add the subcarriers to the meter indication or refer to
an external, calibrated modulation monitor.
BS.1770 Loudness Level
BS.1770-01
Measured
loudness
x
L
K-filter
Mean square
y
L G
L
x
R
K-filter
Mean square
y
R
G
R
x
C
K-filter Mean square
y
C G
C
x
Ls
K-filter Mean square
y
Ls
G
Ls
x
Rs K-filter Mean square
y
Rs
G
Rs
z
L
z
R
z
C
z
s L
z
Rs
10 Log
10
Gate

Figure 1-4: BS.1770 Loudness Meter Block Diagram (from ITU-R document)
The subjective loudness meters, labeled L
OUDNESS
in the 8700i’s GUI, display the
loudness at the output of the digital radio processing chain and analog FM pro-
cessing chains, measured by the ITU-R BS.1770-3
3
algorithm.
3
Recommendation ITU-R BS.1770-3 (08/2012): “Algorithms to measure audio pro-
gramme loudness and true-peak audio level.” BS.1770-3 first introduced gating to
the loudness meter. For further information about the BS.1770-3 meter, please refer
to the following standards: ITU-R BS.1770, ATSC A/85 EBU R 128, EBU Tech 3341, EBU
Tech 3342, EBU Tech 3343, and EBU Tech 3344. These are free downloads that can
be found easily with a search engine.