Orban OPTIMOD-FM 5700i, Руководство по эксплуатации

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INTRODUCTION ORBAN MODEL 5700i
integration time of the Short-Term Meter is always 3 seconds, while the Integrated
Meter uses silence gating and its integration time is user-adjustable to 10, 20, 30, or
60 seconds. Because the meter is always monitoring program material, it integrates
the previous 10, 20, 30, or 60 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 me-
ter’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, dif-
fering only in nomenclature. A change of 1 LUFS is the same as a change of 1 dB.
“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 L
OUDNESS
C
ONTROL
T
HRESHOLD
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 D
IGITAL
R
ADIO
tab in I/O
SETUP
. The other BS.1770-
associated controls are also there.
The meter is scaled so that the loudness level at the consumer’s receiver is correct
when the 5700i’s digital radio processing chain is adjusted to make the dominant
program material indicate “0 dB” on the 5700i’s Loudness Level meter and the
BS.1770 R
EFERENCE
L
EVEL
(which you must enter manually) in I/O Setup is equal to
that specified by the regulatory authority in your country.
Built-in Calibrated Line-up Tones
To facilitate matching the output level of the 5700i to the transmission system that it
is driving, the 5700i contains an adjustable test tone oscillator that produces sine
waves at 5700i’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 (as
described in
Test Modes starting on page 3-77).
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 ste-
reo 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 increase about 2.7% when the modulation is changed
from pure single-channel to L+R modulation while the peak audio level is held con-
stant.
When the 5700i’s left/right analog output is switched to F
LAT
, a de-emphasis filter is
inserted between output of the 5700i’s audio processing and its line output. Thus, as
the frequency of the Test Tone is changed, the level at the 5700i’s line output will
follow the selected de-emphasis curve. In most cases, the pre-emphasis filter in the