OPTIMOD-FM DIGITAL
INSTALLATION
2-35
The Ratings Encoder Loop-through mode has a standard fallback strategy:
To prevent an audio mute, your Optimod will automatically bypass the ste-
reo encoder loop-though and will drive its stereo encoder from the output
of its FM audio processing if there is no valid AES3 signal at your Optimod’s
Sync Input. When this occurs, ratings encoding is not occurring, so warn-
ings will flash on both the Optimod’s front panel and in PC Remote (if pre-
viously connected to your Optimod). Nevertheless, we recommend moni-
toring the presence of valid ratings encoding via the monitor supplied by
the ratings provider.
L)
If you selected
FM
or
FM+D
ELAY
, 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
, 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 2-36.
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 8600S’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
Summary of Contents for OPTIMOD-FM 8600S
Page 1: ...Operating Manual OPTIMOD FM 8600S Digital Audio Processor Version 2 1 Software ...
Page 7: ...Operating Manual OPTIMOD FM 8600S Digital Audio Processor Version 2 1 Software ...
Page 56: ......
Page 166: ......
Page 254: ...3 88 OPERATION ORBAN MODEL 8600S ...
Page 326: ......
Page 328: ...6 28 TECHNICAL DATA ORBAN MODEL 8600S CONTROL BOARD PARTS LOCATOR ...
Page 352: ...6 52 TECHNICAL DATA ORBAN MODEL 8600S ...