Delay Difference Between Digital-Channel And Fm Outputs; Hd I/O Setup Controls; Hd Audio Controls - Orban Optimod-FM 8300 Operating Manual

3-56
OPERATION

Delay Difference between Digital-Channel and FM Outputs

HD I/O Setup Controls

HD Audio Controls

To make the receiver analog/digital crossfade free from comb filtering, the time de-
lays in the HD Radio's analog and digital channels must have a fixed and predictable
offset, correctly implementing the HD Radio receiver's "time diversity" processing.
The 8300's HD output has a constant time offset with respect to the FM output, re-
gardless of the FM output's latency (which can vary depending on processing set-
tings). This fixed time offset is approximately 3 ms. Therefore, the HD Radio exciter
should be preset to compensate for this 3 ms offset between the FM output and HD
output. You must then fine-tune the exciter's delay by ear to minimize comb filter-
ing during analog/digital crossfades. Once you have done this, the time diversity de-
lay will always be correct even if you choose a different 8300 preset.
The ultra-low-latency structure does not support this feature and will
have a different delay offset from the optimum 5-band and 2-band struc-
tures.

Multiplex Power / HD Gain Reduction meter is switchable via the M
control in S
F
UNCTION
the ITU412 Multiplex Power controller. It shows how much the MPX Power Con-
troller has reduced the clipper drive, thereby reducing the average power in the
processed audio. It will show no gain reduction unless the MPX Power Controller
is turned on. In HD GR mode, the meter indicates the larger of the gain reduc-
tions in the left and right channel look-ahead limiters for the HD Radio / digital
radio / netcast processing chain
The PC Remote application shows all meters simultaneously and shows the left
and right HD gain reduction meters separately.
The HD look-ahead limiter is not stereo-coupled. This prevents limiting
on one channel from causing audible modulation effects on the other
channel.

Digital Output: You must use the AES digital output to drive the digital trans-
mitter. All of its associated setup controls (output level, sample rate, format,
word length, and dither) work the same as they do when this output is emitting
the FM-processed signal.
Included with each preset in Full Control on the 8300 unit and also in the "HD Proc-
Function
HF Shelving Filter
Look-Ahead Limiter
. In M
P
ETUP ULTIPLEX OWER
.
Control Name
HD EQ Gain
HD EQ Freq
HD Limiter Drive
Table 3-10: HD Audio Controls
ORBAN MODEL 8300
mode, it indicates the action of
Values
0...–6 dB; 0.5 dB steps
2...– 20 kHz; 1 / 6-octave steps
0...+12 dB; 1.0 dB steps
ETER