Orban OPTIMOD-FM 8600Si, Руководство по эксплуатации

Страница: 91 / 356

OPTIMOD-FM DIGITAL INSTALLATION
2-35
toring the presence of valid ratings encoding via the monitor supplied by
the ratings provider.
L) If you selected
FM
or
FM+D
ELAY in step (I) above , use a modulation monitor or
modulation analyzer to adjust the
DO 100%
control to make the modulation
monitor read 100% modulation (usually
±
75 kHz deviation).
See the notes in step (10.D) on page 2-32.
M) If you selected
HD
in step (I) , set the
DO 100%
control to the maximum peak
output, in units of dBFS, that the following transmission system can accom-
modate.
Once you have set the
DO 100%
control, you may use the
HD L
IM
D
R
control in
the active processing preset to set the final loudness. This is the correct meth-
od for matching the loudness of the analog and HD1 channels in HD Radio
transmission.
If the BS.1770 Safety Limiter is active, the
DO 100%
control does not affect
loudness, only peak headroom. Refer to the explanation in step (12.A) on
page 2-35.
In a transmission system using a lossy codec, it is usually wise to leave 1 to
2 dB of headroom to accommodate codec overshoots.
If the transmission system uses linear PCM, we recommend setting the
DO
100% control to –0.2 dBFS. Because the peak limiter is a “true peak” lim-
iter whose sidechain is oversampled to 256 kHz, setting the DO 100%
control to –0.2 dBFS or lower will prevent overshoots following the
transmission system’s final D/A converter if the D/A converter is phase-
linear (i.e. introduces no group delay distortion). This setting will also
prevent overshoots caused by phase-linear sample rate conversion unless
the sample rate converter removes a significant amount of spectral en-
ergy, which is typically true when the output sample rate is 32 kHz. To
prevent overshoots in 32 kHz transmission systems, set the 8600Si’s
HD
B
ANDWIDTH
control to 15 kHz.
12. Set up and activate the BS.1770 Safety Limiter in the digital radio proc-
essing chain (optional).
The adjustments in this step can only be done from PC Remote.
The BS.1770 Safety Limiter prevents the BS.1770-3 integrated loudness from ex-
ceeding a value set by the
L
OUD THR
control. If your country requires that the in-
tegrated loudness of your digital radio broadcast to be constrained according to
the BS.1770-3 loudness measurement algorithm, execute the steps below.
If your
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