Orban OPTIMOD 5750 Operating Manual page 122

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Orban 5750 Technical Manual Technical Data
Meter uses silence gating and its integration time is 10 seconds. Because the meter is always monitoring program
material, it integrates the previous 10 seconds of program material and weights all program material equally within
the specified time window.
For example, material occurring 3 seconds in the past and 8 seconds in the past both contribute equally to the
meter's current indication; newer program material in the specified time window is not favored over older program
material.
Because loudness perception combines the contributions of all acoustic sources, there is only one Loudness Level
meter indication for both stereo channels.
The unit of measure in the BS.1770 meter is LKFS or LUFS, which are the same, differing only in nomenclature. A
change of 1 LUFS is the same as a change of 1 dB.
In the digital radio chain, "LKFS" and "LUFS" are absolute loudness measurements with respect to digital full scale.
"LK" and "LU" (without the "FS") are relative loudness measurements, where "0" on the meter corresponds to a
user-preset "BS.1770 Reference Level," which you set via your OPTIMOD's BS.1770 LOUDNESS CONTROL
THRESHOLD control. The BS.1770 meter on your OPTIMOD indicates "LK" or "LU"; you can choose which label to use
via a control available on the HD DIGITAL RADIO tab in I/O SETUP. The other BS.1770-associated controls for digital
radio are also there.
The meter is scaled so that the loudness level at the consumer's receiver is correct when the 5750's digital radio
processing chain is adjusted to make the dominant program material indicate "0 dB" on the 5750's Loudness Level
meter and the BS.1770 REFERENCE LEVEL (which you must enter manually) in I/O SETUP > HD RADIO is equal to that
specified by the regulatory authority in your country.
In the analog radio processing chain, the BS.1770 meter and Safety Limiter are calibrated per EBU Tech 33444,
Section 5.9 titled "Practical guidelines for distribution systems in accordance with EBU R 128; Supplementary
information for EBU R 128," which is available for free download. Use a search engine to find the latest version. This
calls for a 1 kHz sinewave at –23 LUFS to produce an FM carrier deviation of ±14 kHz without pilot tone. This
corresponds to 18.67% modulation without pilot tone. This calibration includes 50µs transmission pre-emphasis.
The loudness meter is calibrated so that "0" corresponds to the setting of the BS.1770 LOUDNESS CONTROL
THRESHOLD control in INPUT/OUTPUT > UTILITY.
Built-in Calibrated Line-up Tones
To facilitate matching the output level of the 5750 to the transmission system that it is driving, the 5750 contains an
adjustable test tone oscillator that produces sine waves at 5750's (analog or digital) left, right, and composite
outputs. The frequency and modulation level of the line-up tones can be adjusted from the front panel.
The stereo encoder is calibrated so that 100% left or right modulation will provide 100% modulation of the stereo
composite signal, including pilot tone, but excluding any SCA subcarriers. The pilot tone stereo system has an
interleaving property, which means that the stereo composite modulation is approximately equal to the higher of
the left or right channels.
Because the pilot tone is phase-synchronous with the stereo subcarrier, the composite modulation will actually
increase about 2.7% when the modulation is changed from pure single-channel to L+R modulation while the peak
audio level is held constant.