2-32
INSTALLATION ORBAN MODEL 8685
C) Make sure that your transmitter is configured to apply preemphasis to the
audio it receives from the 8685.
D) L
OCATE to INPUT/OUTPUT > 2.0 OUT > 2.0 OUTPUT LEVEL (100%) and set the 2.0
OUTPUT LEVEL (100%) control to 0.0 dBfs.
E) Set your transmitter’s modulation with tone.
a) L
OCATE to SYSTEM SETUP > TEST MODES.
b) Choose T
ONE. Set FREQUENCY to 100 HZ and LEVEL to 100%.
c) Click the T
ONE button.
d) L
OCATE to the MAPPING page (to the right of the TEST MODES page) and set
the L
2.0 TONE PROC X AND R 2.0 TONE PROC X fields to TONE, where “x” is a
number from 1 to 4 that identifies which of the four available 2.0
processors you are using to drive the transmitter.
e) If you are driving your transmitter with the 8685’s analog outputs: L
OCATE
to I
NPUT/OUTPUT > UTILITIES and adjust the ANALOG OUTPUT LEVEL control to
produce 100% modulation of your transmitter as measured by the peak
modulation instrument specified by your country’s regulatory authority.
This assumes you have routed the 2.0 processing’s left and right outputs
to the analog outputs. The routing matrix is located in the O
UTPUT
ROUTING tab in I/O SETUP.
f) If you are driving your transmitter with an 8685 digital output: Use a gain
control following the 8685 output (typically, your analog transmitter’s
sensitvity control) to produce 100% modulation of your transmitter.
Achieving correct on-air loudness and proper operation of the 8685’s
loudness meter requires you to align the transmission system following
the 8685 so that 0.0 dBfs at the 8685’s output corresponds to 100% peak
modulation of the transmitter. Using the 8685’s 2.0
OUTPUT LEVEL control
to set the gain between the 8685 and the transmitter will not produce
correct loudness meter calibration and on-air loudness because this con-
trol only sets the maximum peak level while attempting to maintain the
average modulation constant when adjusted. It does this by driving the
look-ahead limiter 1 dB harder for every 1 dB that the 2.0
OUTPUT LEVEL is
turned down.
F) Test modulation with program material to determine the overshoot in your
transmission system.
a) L
OCATE to SYSTEM SETUP > TEST MODES and choose OPERATE.
b) Recall the TVA
5B GEN PURPOSE preset.
c) Apply typical program material to the 8685’s input. Verify that the 2.0
LIMITER GR meters are indicating gain reduction on peaks, which ensures
that the 8685 is producing 100% peak modulation on program material.
d) Measure your transmitter’s peak modulation. If this exceeds 100%, turn
down the 8685’s 2.0
OUTPUT LEVEL control until the modulation of peaks of
frequent recurrence is constrained to 100% deviation.
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