Spectrum Analyzer Procedure⎯Setting The Modulator Output Signal Level In Operate Mode - Motorola OM 1000 Installation And Operation Manual

Spectrum Analyzer Procedure⎯Setting the Modulator Output Signal Level in Operate Mode
When combining the RF modulator output signal with other headend signals that use analog
carriers, you must set the modulator output signal level to approximately 15 dBmV below the
level of the analog carriers.
Set the RF-modulator output-signal level by incrementing or decrementing the signal-level
parameter from 0 through 40. This range corresponds to an actual output level ranging from
+30 through +50 dBmV. The default level setting is 35, approximately 45 dBmV.
To set the RF-modulator output-signal level with the modulator in OPERATE mode:
1
Measure and record the signal level of the analog carriers by observing the level of the
carriers during sync tip. During sync tip, the full power of the signal is concentrated in the
carrier.
2
Connect the
RF OUT
Configuration
Resolution bandwidth
Video averaging
3
Measure the power of the modulator-output signal.
of the OM 1000 to a spectrum analyzer configured as follows:
Setting Comments
300 kHz The bandwidth of the RF-modulator output signal is about
1.5 MHz, which is wider than the maximum resolution
bandwidth of most spectrum analyzers. For spectrum
analyzers that do support a higher-resolution bandwidth,
adjacent channel signals can interfere with measurement of a
1.5 MHz bandwidth signal.
A 300 kHz resolution bandwidth measures a portion of the
output signal total bandwidth.
ON Because the modulator-output signal is QPSK modulated, the
signal level changes constantly over time, resulting in a
noise-like signal. Video averaging smoothes out the variations
in the signal to provide an average signal level.
Alternatively, you can observe the signal-power average by
reading the level that corresponds to the center or average of
the noise line rather than its peak.
Setup and Operation
OM 1000 Installation and Operation Manual
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