Orban OPTIMOD-FM 5500 Operation Manual page 72

2-24
INSTALLATION
In step 6 in Quick Setup (page 2-16), make sure that you have set the
5500's preemphasis to match the preemphasis of the input signal. Even
though the 5500 is not applying preemphasis, its L/R overshoot limiter
needs to be aware of the input signal's preemphasis because the over-
shoot limiter uses different algorithms for 50 and 75 µs. This minimizes
audible limited-induced artifacts.
Usually, the STL adds less peak overshoot to its input signal if its input
and output signals are preemphasized. Doing this eliminates several
stages of deemphasis and preemphasis. However, if the STL uses lossy
digital compression (like MP2), you must apply a flat signal to the STL
and restore preemphasis in the 5500. Studio-Transmitter Link (starting on
page 1-15) has a thorough discussion of these issues.
5. Adjust the input lowpass filter.
A) If you do not see the I
pears.
B) While holding down the I
cutoff frequency of the phase-linear lowpass filter at the 5500's input.
It is usually unnecessary to use this filter; you may set it O
need to remove out of band noise from a noisy STL.
To minimize filter-induced overshoot, set the cutoff frequency as high as
possible. While this filter introduces no phase distortion, it will add over-
shoot if it removes a significant amount of the high frequency energy
that was present at the output of the audio processing driving the 5500.
If you are using an Optimod-FM 8000, 8100, 8500, or 8600 audio proces-
sor to drive the STL, set the 5500's L
are using any other Optimod-FM, set the filter to O
6. Set the analog input reference level.
[Skip this step if you will not be using the analog input.]
A) Navigate to Setup > I/O C
B) Set the I to Analog.
NPUT
The 5500 will automatically switch to analog input if signal lock is un-
available at the AES3 input.
C) Apply a 50 Hz sine wave the 5500's analog input (usually through an STL) and
set the peak level of the tone to equal the maximum peak output level pro-
duced by the FM audio processor driving the 5500.
All digital Optimod-FM processors have a built-in tone oscillator that can
generate this tone. Set the modulation in the Optimod's tone generator
to 100%.
Tone alignment does not account for any overshoots that the STL might
generate with program material. Normally, you will use the 5500's
left/right overshoot limiter and/or composite limiter to eliminate such
overshoots. Do not substitute these limiters for the peak limiters in the
audio processor driving the STL. The 5500's overshoot limiters should only
be used to eliminate 3 dB or less STL-induced overshoot.
LPF soft button, press the Next button until it ap-
NPUT
LPF soft button, rotate the knob to set the
NPUT
OWPASS
> A I C > I
ALIB NLG N ALIB
ORBAN MODEL 5500
unless you
UT
F to O or 17 . If you
ILTER UT KHZ
, 16 or 17
UT KHZ KHZ
.
NPUT
.