Orban OPTIMOD-FM 8600, Operating Manual

Page: 255 / 397

OPTIMOD-FM DIGITAL OPERATION
3-75
54), automation (page 2-42), and GPI remote interface (page 2-60).
Out Source allows you to determine if a given output (analog left/right, AES3 #1,
AES3 #2) emits the FM-processed signal (
FM
), the FM-processed signal with diversity
delay (
FM+D
ELAY
), the low-delay monitor signal (
M
ONITOR
;
for driving talent head-
phones) or the HD-processed signal (
HD
). This versatile control allows you to selec-
tively apply diversity delay to each output as desired.
Diversity Delay Trim allows you to trim the analog FM delay in intervals of one
sample of 64 kHz (15.6 µs) so that the delays of the analog-FM and digital radio
channels are matched at the receiver’s crossfade point. This prevents audible comb
filtering during crossfades. The setting of this control is critical to get best results
and you should adjust it to one-sample accuracy.
When this field is highlighted, press the
E
NTER
button to toggle between coarse and
fine adjustment. In PC Remote, drag the slider of the control with the mouse to set
the delay coarsely, use the Page Up and Page Down keys for intermediate incre-
ments, and use the mouse wheel to fine-tune the delay in one-sample adjustment
increments.
Maximum available delay is approximately 16 seconds.
See the documentation provided with your HD Radio exciter for more in-
formation on setting the delay correctly.
You can adjust the diversity delay time via the 8600’s API. See page 2-54.
St. / Mono (“HD Output Stereo / Mono Mode”) determines if the digital-channel
output will be fed by the normal stereo output of the HD processing chain or by a
mono feed from the HD processing chain’s left channel, right channel, or sum of left
and right channels. In all cases, the signal appears on both the left and right chan-
nels of the analog and digital outputs.
The 8600 does not set the AES3 stereo / mono status bits to reflect the
setting of this control. The AES3 status bits appearing at the HD output
are always set “stereo” even when the two audio channels carry identical
mono signals.
HD Bandwidth sets the audio bandwidth of the HD output from 15 to 20 kHz in
1 kHz steps.
The user should carefully test the codec in use to ascertain if lowering the
bandwidth to 15 kHz improves subjective quality. This can occur because
the codec then uses all of its bits to encode information in the most sub-
jectively important part of the ear’s bandwidth. If the codec employs
Spectral Band Replication® technology (as does the iBiquity HD Codec),
then you can set the bandwidth at 20 kHz without quality penalty, alt-
hough the difference between 15 and 20 kHz is unlikely to be audible
following the encode / decode cycle.
HD Polarity sets the polarity of the output of the HD processing to
P
OSITIVE
or
N
EGATIVE
. The switch allows you to match the polarity (sometimes informally called
“phase”) of the audio through the analog FM and HD transmission channels, regard-