— 40 —
FRONT-PANEL HEADPHONE JACK
The headphone jack on the front panel monitors the broad-
band-limited output of the peak limiter. This is a ‘flat’ monitor
point that does
not
reflect action of the 15kHz low-pass filter
and adaptive pre-emphasis for FM transmission, nor the effects
of composite clipping. The volume control next to the jack ad-
justs only the headphone volume.
COMPOSITE MULTIPLEX OUTPUT
The DAVID IV has two independent outputs for the compo-
site/MPX (multiplex) signal. These outputs include the S (L+R),
S’ (L–R), 19kHz Stereo Pilot and optional RDS subcarrier com-
ponents that comprise the FM baseband signal.
Navigate to:
Setup / Stereo Generator
:
Confirming
Pre-Emphasis
FM broadcasting imparts high-frequency pre-emphasis to the
program audio signal in transmission, and the FM receiver pro-
vides the complementary de-emphasis. The time constant of
the pre- and de-emphasis networks is determined by geograph-
ic location. The Americas (Western Hemisphere) have standard-
ized on a 75-microsecond curve, and Europe has chosen 50-
microseconds. Other parts of the world have opted for one or
the other of these, so make sure you know what setting is the
proper one for you location before proceeding.
From the previous menu select:
Pre-Emphasis
to bring up the se-
lection screen shown here:
Turn
the jog wheel to position the brackets around the desired
characteristic:
50us
or
75us
, and then
push
the knob to
set it and fix this selection in the DAVID IV non-volatile
memory. The
None
option is included for test purposes only.
Mono Mode and
Pilot Injection
Press the
Back
button to return to the
Stereo Generator
menu.
Turn
the jog wheel to select
Pilot
and
push
the knob to bring up
the
Pilot
menu, shown at the top of the next page.
Summary of Contents for 719
Page 1: ...DAVID IV FM Audio Broadcast Processor Installation User Guide www inovonicsbroadcast com ...
Page 2: ......
Page 4: ......
Page 70: ... 66 NOTES AND DOODLES ...