Orban 5750 Technical Manual Operation 3-39
16, 20, 25, 31.5, 40, 50,
63, 80, 100, 125, 160,
200, 250, 315, 400, 500,
630, 800, 1000, 1250, 1600, 2000,
2500, 3150, 4000, 5000,
6300, 8000, 9500, 10000, 12500,
13586.76, 15000
Table 3-7: Digital MPX
Facilities are self-explanatory, except for the following:
The TONE LVL control is calibrated under the assumption that the stereo pilot tone contributes 9% to the total
modulation. Hence, a TONE LVL setting of 91% produces 100% modulation (91% + 9%).
Note that when the OPTIMOD is in TONE mode and its analog or digital L/R outputs are set to FLAT (instead of PRE-
EMPH), these outputs apply 50μs or 75μs deemphasis to the output of the tone oscillator. Applying deemphasis this
way is only correct if equipment downstream from the OPTIMOD, like a transmitter’s stereo encoder, applies
preemphasis before final transmission.
In BYPASS mode, preemphasis is still applied to the signal path. The BYPASS GAIN control calibration allows enough
internal headroom to make swept frequency response measurements without internal clipping. When the BYPASS
GAIN control is set to 0.0 dB and the AI REF VU control is set to 0.0 dBu, you will observe a gain of approximately –17
dB from the analog input to the analog output at 100 Hz. If the AO PRE-E control is set to PRE-E and the 5750 is
configured for 75µs preemphasis, the gain from analog input to analog output will be approximately 0 dB at 15 kHz.
While this calibration may seem unintuitive, experience has shown that it greatly reduces calls to Orban customer
service complaining that the frequency response of the transmission path is not flat when in fact the measurement
in question was causing undetected clipping at high frequencies due to preemphasis.
To Next Page
Loading...
Need help?
General
