Operators increase Return Path bandwidth by using higher QAM64, 128, 256. Higher QAM introduces more noise sources affecting
QAM64, 128 and 256. It becomes important to verify transmission quality with Return Path QAM analysis.
For Return Path QAM analysis, the upstream signal source must be FEC encoded in order for MER, Pre-FEC, Post-FEC and
Constellation analysis. Generally, a VeEX CX series test unit with USG+FEC is required as the signal source.
To perform the Return Path QAM Analysis:
1. Press Return Path Analysis under the Advanced Tools menu on the home screen. Connect the test cable to the RF-IN test port.
2. Input test parameters: CF (Center Frequency), Symbol Rate, BW (Bandwidth), and MOD (Modulation) to match far end USG unit.
3. Press Start. Look for the QAM lock logo to transition to green and for measurements to begin.
7.8.2 Sweep Operations
Overview:
Sweep is used to identify improper balance of amplifiers, tilts, or suck outs.
Tilt and Suck Out
Starting from a drop point nearest to the signal source, for example, a Headend office, a Sweep operation measures the signal levels
across the bandwidth with predefined check points in a Sweep table. The measurement is kept as a reference. Move the test set to the
next drop point away from the first one, take the same measurement and compare with the reference measurement. Ideally, the signal of
each check point should be relatively less or more, proportionate to the reference signal.
The following Sweep Operations are available under the Sweep Operations menu:
Summary of Contents for VEPAL CX350S-D3.1
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