OPTIMOD-AM DIGITAL
INSTALLATION
2-37
K)
Interactively tweak these controls to maximize separation (by minimizing the
maximum amount of crosstalk into the undriven channel). It may turn out
that no improvement is possible.
L)
Navigate to
S
ETUP
>
T
EST
.
M)
Set the
M
ODE
to
O
PERATE
.
15.
Test the polarity and LF transmitter equalization settings under pro-
gram conditions.
A)
Apply program material to OPTIMOD-AM's input at normal operating levels.
B)
Recall the
GEN
MED
preset:
a)
Press the Recall button.
b)
Turn the control knob until you see next:
GEN
MED
.
c)
Press the RECALL NEXT soft key button to select the
GEN
MED
preset.
C)
Turn on the carrier.
D)
Navigate to
S
ETUP
>
M
ODIFY
S
YS
P
ST
>
TX1/D
AY
.
E)
Set the
P
OS
P
EAK
control to 125%:
F)
Check modulation asymmetry with the oscilloscope or with your modulation
monitor.
If negative peaks are modulating higher than positive peaks:
a)
Navigate to
S
ETUP
>
I/O
C
ALIB
.
b)
Press the button corresponding to the active output
c)
Change the setting of the
P
OLARITY
control.
d)
Navigate to
S
ETUP
>
M
ODIFY
TX
P
RESET
>
TX1/D
AY
.
G)
Set the
POS
PEAK
control to 100%.
The 100% setting yields the cleanest sound. (See page 1-16 for an expla-
nation.)
However, if absolute maximum loudness is desired at the expense of
cleanest possible sound, the
POS
PEAK
control may be set as high as
your government regulations and transmitter performance will allow. In
the U.S., FCC Rules limit this to 125%.
Note too that the distortion of older transmitters and most receivers
tends to increase radically when negative modulation of more than 85%
is attempted. In the case of receivers, the major cause of this distortion is
cheaply designed envelope detectors with incorrectly biased diodes. Con-
sider reducing clipping in the processing so that the last 15% or so of
modulation consists of low duty-cycle spikes that can be soft-clipped by
the receiver’s detector. This trades off about 1.5dB loudness loss for sub-
stantially cleaner sound.
If you choose to modulate asymmetrically with a transmitter that com-
presses peaks in the positive direction,
do not
attempt to modulate be-
Summary of Contents for Optimod-AM 9400
Page 1: ...Operating Manual OPTIMOD AM 9400 Digital Audio Processor Version 1 2 Software...
Page 7: ...Operating Manual OPTIMOD AM 9400 Digital Audio Processor Version 1 2 Software...
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Page 261: ...OPTIMOD AM DIGITAL TECHNICAL DATA 6 29...
Page 267: ...OPTIMOD AM DIGITAL TECHNICAL DATA 6 35 CPU Module...
Page 273: ...OPTIMOD AM DIGITAL TECHNICAL DATA 6 41 RS232 BOARD PARTS LOCATOR...
Page 275: ...OPTIMOD AM DIGITAL TECHNICAL DATA 6 43 8300 POWER SUPPLY PARTS LOCATOR...
Page 284: ...6 52 TECHNICAL DATA ORBAN MODEL 9400 DSP BOARD PARTS LOCATOR DRAWING 32170 000 14...
Page 292: ...6 60 TECHNICAL DATA ORBAN MODEL 9400 DISPLAY BOARD PARTS LOCATOR...
Page 293: ...OPTIMOD AM DIGITAL TECHNICAL DATA 6 61 DISPLAY BOARD...