Orban OPTIMOD-FM 5700i, Operating Manual

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OPTIMOD-FM DIGITAL INTRODUCTION
1-23
Line-Up Facilities
Metering of Levels and Subjective Loudness
The meters on the 5700i show left/right input levels and composite modulation. Left
and right input level is shown on a VU-type scale
(
0 to –27 dB), while the metering
indicates absolute instantaneous peak (much faster than a standard PPM or VU me-
ter). The input meter is scaled so that 0 dB corresponds to the absolute maximum
peak level that the 5700i can accept (+27 dBu). If you are using the AES3 digital in-
put, the maximum digital word at the input corresponds to the 0 dB point on the
5700i’s input meter.
If you have an 5700iHD, you can switch the front-panel metering to indicate level
and gain reduction parameters relevant to the digital radio processing chain or to
the analog FM processing chain. Simultaneous metering of analog and digital radio
processing chains is available on 5700i PC Remote Software.
Composite Output Level
The 5700i controls instantaneous, absolute peak levels to a tolerance of approxi-
mately
±
0.1 dB. Composite modulation is indicated in percentage modulation, abso-
lute 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
or when the final clipper is defeated in Setup). 100% ordinarily
corresponds to
±
75 kHz-carrier deviation.
Note that when the 5700i’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 it is metered. Therefore, you
must mentally add the subcarriers to the meter indication, or refer to an external,
calibrated modulation monitor.
BS.1770-3 Loudness Level
The subjective loudness meter, labeled L
OUDNESS
L
EVEL
in the 5700i’s GUI, displays
the loudness at the output of the digital radio processing chain, measured by the
ITU-R BS.1770-3
5 algorithm.
The loudness meter indicates both BS.1770 Short-Term and Integrated Loudness on
the same scale. The solid bar indicates the Integrated Loudness, while the floating
bar segment indicates the Short-Term Loudness. Per the BS.1770-3 specification, the
5
Recommendation ITU-R BS.1770-3 (03/2013): “Algorithms to measure audio pro-
gramme loudness and true-peak audio level.” 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.