Q-Lite Satellite Modem Installation and Operating Handbook
6-95
Figure 6-48 Rx Constellation Monitor
The Rx Constellation Monitor can be used to check for correct modem operation including
checking for signal distortion and phase noise. The persistence mode is useful for
showing any long-term effects due to phase noise and interference. Excessive phase
noise can cause cycle skips, seen as unwanted rotations within the constellation.
Note that MER and EVM figures are available on the panel on the right hand side. These
concepts are explained in the following information panel.
Modulation Error Ratio (MER) and Error Vector Magnitude (EVM)
MER and EVM (as displayed on the Rx Constellation Monitor)
measure how imperfect the received signal is in relation to an
ideal signal as in the following example.