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Here the DAVID IV can be placed in the
Mono
(monaural
transmission) mode for testing or for special circumstances,
though
Stereo
will be the usual choice for normal operation.
Selecting
Mono
removes both the 19kHz stereo pilot tone and
the S’ (L–R ‘stereo difference’) subcarrier.
The 19kHz RDS sync output remains active, however, assuring
that RDS messaging remains an available option in mono.
The factory-default setting of 9.0% stereo pilot injection is
normal for FM transmissions worldwide, although the value
may be set anywhere between 6% and 12%. To reset the level to
a nonstandard figure,
turn
the jog wheel to place the brackets
around the
Pilot Level
slider,
push
the knob, and then
turn
it to
adjust the injection level.
Adjusting
the Multiplex
Outputs
Press the
Back
button to return to the
Stereo Generator
menu.
Turn
the jog wheel to select
Multiplex Out
and
push
the knob to
bring up the
Multiplex Output
menu:
The levels of the two independent composite/MPX outputs are
individually adjustable. The open-circuit peak-to-peak voltage
at the rear-panel BNC connectors is displayed below the slider
window. This voltage level, which represents 100% program-
peak carrier modulation, is adjustable between 0.8V p-p and 9V
p-p (+12dBu.)
Turn
the jog wheel to bracket the appropriate
slider (
MPX Level 1
or
MPX Level 2
),
push
the knob to select it, and
then
turn
the knob to dial-in the desired output level.
The exact setting of this control will depend on the input sensi-
tivity of your FM exciter or STL (microwave link) transmitter
and the desired peak carrier modulation you wish to achieve.
Use your mod-monitor to check the off-air signal when making
this adjustment, and be sure that audio processing setup has
been completed to your satisfaction before fine-tuning the out-
put level.
Multiplex
Output
Servo
The DAVID IV employs an open-loop servo system to maintain
the multiplex output at the precise level set by the user. As ei-
ther the 19kHz stereo pilot level or the RDS injection level is
adjusted (or even turned off), the composite/MPX output re-
mains constant so that no back-and-forth tweaking is required.
Summary of Contents for 719
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