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16
1. To the left channel
only,
apply a 500Hz test tone from the console
at a level 2.5dB above normal reference level. This is simply a
console VU meter indication of +2.5VU.
2. Adjust the left channel (
L
)
INPUT GAIN
control so that
both
the
0dB
and
the
–5dB
AGC GAIN
indicators light to
equal brilliance.
Remember that the AGC circuit responds slowly to level changes, so
have patience in performing this step of the procedure.
3. Turn off the +2.5VU test signal to the left channel and apply
+2.5VU to the right channel
only.
4. Adjust the right channel (
R
)
INPUT GAIN
control so that
both
the
0dB
and
the
–5dB AGC GAIN
indicators light to
equal brightness.
This completes
INPUT GAIN
adjustment. The
DAVID-II
may now be
fed normal stereo program material from the console. If this
procedure has been performed properly, and the operator pays
reasonable attention to console metering, the
AGC GAIN
indicators will
always remain the green-LED “safe operating” zone between
–5dB
and
+5dB
.
Output Level
Adjustment
Perform this part of the procedure “on-air” under normal operating
conditions, and using typical program material. You also must have
access to the station’s Modulation Monitor. An RDS or SCA subcarrier
should
not be connected
until Step #6. Be sure that the
COMPOSITE
PROCESSING
control is
OUT
; that is, fully counterclockwise.
PLEASE
be certain that you understand operation of the Mod-
Monitor, and that it is properly calibrated and connected to the correct
transmitter/exciter RF sample point.
1. Put the Mod-Monitor in its “Total Peak Modulation” measurement
mode with peak flasher(s) set to 100%.
2. Turn the
AVERAGE COMPRESSION
control fully clockwise (
10dB).
With normal program fed to the
DAVID-II
(at the level which
maintains
AGC GAIN
in the center of its range), adjust the
OUTPUT
LEVEL
control for a Mod-Monitor indication of
frequent
100%-
modulation peaks.
3. Back-down the
OUTPUT LEVEL
control slightly, so that the 100%
peak flasher(s) light only occasionally.
4. Switch the Modulation Monitor to display the injection level of the
19kHz stereo pilot.
5.
Adjust the
PILOT INJ.
control for a 9% Mod-Monitor reading of pilot
injection.
6.
(OPTIONAL)
If an RDS or an SCA subcarrier is to be broadcast,
connect it to the
DAVID-II
(or other combining point) at this time.
Using the Mod-Monitor, or other means of reading the auxiliary
subcarrier injection level, adjust the
SUB INJ.
level control (or other
subcarrier level control) for the proper injection. This is normally
