CSO/CTB
The CX380C measures the CSO/CTB by taking the measurement at the programmed frequency offsets of an analog channel’s
video carrier. The frequency offsets can be programmed in
Setup Main Menu
.
The default values are:
CSO-1 offset: 1.25MHz
CSO-2 offset: 0.75MHz
CTB offset : 0 MHz
CSO-3 offset: -0.75MHz
CSO-4 offset: -1.25MHz
The CX380C first measures the signal levels at those frequency offsets of a live carrier then prompts to either use a channel blocker
or remove the carrier. The same frequency offsets will be measured after the carrier is removed or blocked and they are used to
compare with the previously measured results with a live carrier to determine the final CSO/CTB values.
Alternatively, the CX380C can measure the CSOs of a live carrier without using a channel blocker or removal of the carrier by
selecting the GATED CSO mode. In this mode, the CX380C measures the noise level at the frequency offsets during the sync pulse
period where the carrier signal is quiet then compare with the measured levels during the non sync pulse period.
7.1.2 Digital Channel Measurements
When testing a digital channel, the unit first tries to lock onto the QAM signal. Once the QAM signal is locked, the unit starts
displaying the digital measurement results as well as the constellation diagram.
QAM unlock
If the unit is unable to lock onto the digital channel, the following icon is displayed.
Always ensure QAM lock is achieved prior to making Constellation and related digital measurements.
SLM button:
The following measurement information is provided for digital signals:
Channel number (defined in the channel table)
Channel frequency (defined in the channel table)
Channel or program name
Modulation type measured
QAM Power Level in dBmV/dBuV including graphic bar indication
Modulation Error Ratio (MER) in dB
Pre BER & Pre Error Second ratio
Post BER & Post Error Second ratio
Severely Error Second count
Max Adjacent Channel Delta in dB
Graphic limit indicators are provided for all graphically displayed signal levels. Numeric data that is outside of limits are displayed in
red.
CX380C User Manual RevA00
Page 24 of 105
