Orban OPTIMOD-FM 5500 Operation Manual page 71

OPTIMOD-FM DIGITAL
2. Turn the 5500's ITU-412 MPX power controller off.
When on, it causes gain reduction that makes it impossible to set the AI
and DI reference level controls correctly with test tones. See step 20 on
page 2-21.
3. Recall the ST ENC NO LIM preset.
A) Press the Recall button on the 5500's front panel.
B) Turn the knob until S
C) Press the Recall Next button.
The 5500 is now in stand-alone stereo encoder mode. The L/R protection
limiting and composite limiter are inactive. This makes it easier to adjust
modulation using a test tone.
4. Adjust the input to accept a flat or preemphasized signal.
Note for users of J.17 preemphasis: If you are using the digital input and
set it to D
J.17 deemphasis to the digital input signal. It will then leave it un-
changed or preemphasize it at 50 or 75 µs, following the setting of the
I P
NPUT
The J.17 option is rarely used; it applies mainly to NICAM links. You can
set most Optimod-FMs to emit a J.17-preemphasized signal with or with-
out additional 50 or 75 µs preemphasis. For example, see step (12.B) on
page 2-18.
A) Press the Modify button.
B) If you do not see the A
appears.
C) While holding down the A
the 5500 to the input signal's preemphasis.
All FM audio processing chains must include a preemphasis limiter to
prevent high frequency overmodulation. Therefore, regardless of
whether you choose Y
nal driving the 5500 stereo encoder has already received 50 µs or 75 µs
preemphasis limiting. (Any Optimod-FM will perform preemphasis limit-
ing.) You must set the 50 or 75 µs preemphasis in the audio processor
driving the 5500 to be the same as the 5500's preemphasis setting.
If the signal driving the 5500 has not already received preemphasis limit-
ing, you must run the 5500 in its audio processing mode (not its stand-
alone stereo encoder mode) so that the 5500 can perform the preempha-
sis limiting.
 Choose Y
Y causes the 5500 to apply 50 or 75 µs preemphasis to the input signal,
ES
following the preemphasis setting you specified in step 5.F) in Quick
Setup (page 2-16).
 Choose N
E N L
T NC O IMIT
+J17 in step (8.B) on page 2-16, the 5500 will first apply
IGITAL
, as adjusted in the steps immediately below.
-E
RE MPH CONTROL
E
PPLY MPH
E
PPLY
or N
ES O
if the input signal has no 50 or 75 µs preemphasis.
ES
if the input signal has already been pre-emphasized.
O
is visible in the lower line of the display.
soft button, press the Next button until it
soft button, rotate the knob to match
MPH
in this step, you must ensure that the sig-
2-23
INSTALLATION