Orban OPTIMOD-FM 8700, Operating Manual

Page: 297 / 390

OPTIMOD-FM DIGITAL TROUBLESHOOTING
5-7
Do not match levels by adjusting the output level of the output driving the HD ex-
citer. Only use this control to match the peak levels of the Optimod output to the
exciter . In other words, if the exciter is set to clip when it receives at –3 dBFS, adjust
the Optimod output level to –3 dBFS. This uses all of the headroom available in the
transmission channel, minimizing the amount of look-ahead limiting that the Opti-
mod needs to do.
If you have accidentally turned on the BS.1770 Safety Limiter, this will cause the
loudness to be lower than expected in HD Radio applications. Turn it off. See step 10
on page 2-32.
Digital Radio Loudness Cannot be Set Using the Digital Output 100% Peak Level Con-
trol
When the BS.1770 Safety Limiter is
ON
, adjusting the HD-assigned
100% P
EAK
L
EVEL
C
ONTROL
sets only the output headroom, not loudness. See step 10 on page 2-32.
Loudness Drops Momentarily During HD Radio Analog/Digital Crossfades
The analog and digital channels in your transmission path have reversed polarity
with respect to each other and a phase cancellation is occurring in the radio during
crossfades. You can correct this with the
HD P
OLARITY
or FM P
OLARITY
controls. See
page 3-79.
HD Frequency Response is Limited to 15 kHz
The
HD B
ANDWIDTH
control might be set to 15 kHz. See page 3-78.
Even if the
HD B
ANDWIDTH
control is set to 20 kHz, bandwidth will be limited to 15
kHz if the HD output’s sample rate is set to 32 kHz and/or if the sample rate of the
audio applied to the 8700i’s digital input is 32 kHz. 20 kHz response requires sample
rates to be set to 44.1 kHz or higher.
Loudness is unexpectedly low from the analog FM processing chain
The MPX Power Controller and/or analog FM processing chain BS.1770 Safety Limiter
may have been turned on accidentally. See step 12 on page 2-24 and step 13 on
page 2-25 .
Digitized SCA inputs do not appear at the analog composite outputs and vice-versa
(MPX hardware only)
This is normal: Non-digitized SCA inputs are summed into the analog composite
outputs in the analog domain after D/A conversion and digitized SCA inputs are only
summed into the digital composite outputs. If you need to use both the digital and
analog composite outputs, you must split the outputs of your SCA generators with Y
cables so that each generator output drives one digitized SCA input and one non-
digitized SCA input.
General Dissatisfaction with Subjective Sound Quality
The 8700i is a complex processor that can be adjusted for many different tastes. For
most users, the factory presets, as augmented by the gamut offered by the
L
ESS
-
M
ORE
control for each preset, are sufficient to find a satisfactory “sound.” However,
some users will not be satisfied until they have accessed other Modify Processing
controls and have adjusted the subjective setup controls in detail to their satisfac-