Orban OPTIMOD-FM 8600Si, Operating Manual

Page: 168 / 356

3-2
OPERATION ORBAN MODEL 8600Si
•
Input meters show the peak input level applied to the 8600Si’s analog or digital
inputs with reference to 0 = digital full-scale. If the input meter’s red segment
lights up, you are overdriving the 8600Si’s analog to digital converter, which is a
very common cause of audible distortion.
•
Gate LED indicates gate activity, lighting when the input audio falls below the
threshold set by the AGC gate threshold control (via the Full Modify screen’s
AGC G
ATE
control). When this happens, the AGC’s recovery time is slowed to
prevent noise rush-up during low-level passages.
There is also an independent gate for the multiband compressor (3-band
and 5-band). You can only see its action from the Optimod PC Remote
software.
•
Gain Reduction meters normally show the gain reduction in the multi-band
compressor. Full-scale is 25 dB gain reduction.
When the Five-Band structure is operating, all the meters indicate gain reduc-
tion.
When the Two-Band structure is operating, the Band 1 and 2 meters indicate
gain reduction in the Master and Bass bands, the Band 3 meter indicates the lar-
ger of the actions of the left and right HF enhancers, and the Band 4 and 5 me-
ters indicate left and right HF Limiter gain reductions.
•
Composite meter shows the output level of the stereo encoder before
the composite output attenuators. The meter’s reading is calibrated in
percent modulation.
•
Multiplex Power Gain Reduction meter indicates the action of the ITU412
Multiplex Power controller. It shows how much the MPX Power Controller has
reduced the clipper drive, thereby reducing the average power in the processed
audio. It will show no gain reduction unless the MPX Power Controller is turned
on.
In PC remote, this meter uses a two-color display to indicate the action of the
ITU Multiplex Power controller and the BS.1770 safety limiter in the analog radio
processing chain. It shows how much the Multiplex Power Controller and
BS.1770 Safety Limiter have reduced the clipper drive, reducing the average
power in the processed audio. The BS.1770 gain reduction is shown in cyan and
the multiplex power gain reduction is shown in dark blue.
•
Multiplex Power Level meter indicates multiplex power according to the ITU-R
BS.412 standard. Its calibration will be correct if the Optimod’s output level con-
trol was adjusted using the tone method (see step 11.D) and subsequent steps
starting on page 2-19) and the transmission path following the Optimod has no
overshoot. See
ITU-R Multiplex Power Controller starting on page 3-80 for a full
discussion of the Multiplex Power Gain Reduction and Level meters.