The following measurement information is provided for digital signals over two screens. Under the SLM tab, the following
measurements can be seen:
QAM Power Level (graphic bar and numeric in dBmV)
MER (numeric in dB)
Pre BER & Pre Error Seconds (numeric)
Post BER & Post Error Seconds (numeric)
Severely Error Seconds (numeric)
Max Adjacent Channel Delta (numeric in dB)
Note:
Modulation Error Ratio (MER)
in digital systems is very similar to Carrier to Noise (C/N) in analog
systems. It is a measure of how tightly symbols are recorded with respect to their optimum location based on
the Error Vector Magnitude or EVM.
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 you should have 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, CSO, CTB and Ingress.
CX100/110/120/150/180 series e-Manual D07-00-002 Rev B01
Page 14 of 39
