SLM Measurement (Digital Carrier)
Modulation Error Ratio (MER)
In digital systems, MER is very similar to Carrier to Noise (C/N) in analog systems. MER measures how tightly symbols are
recorded with respect to an optimum location based on the Error Vector Magnitude (EVM).
Modulation Error Ratio (MER) and Error Vector Magnitude (EVM) Relationship
MER determines how much margin the system has available before a failure can be expected. A poor MER is not noticeable on the
picture up until the point of system failure - this is often referred to as the "Cliff Effect". Ideally, there should be at least 4 to 5dB of
margin from the MER where significant errors occur to allow for system degradation. MER measurements are useful for early
detection of non-transient (noise) impairments, such as system noise Ingress.
CX380C User Manual RevA00
Page 25 of 105
