Interface Configuration and Interpretation

The following graphs are available when the COFDM interface card is installed:

RF constellation (all data carriers)

When the receiver is in RF lock, the constellation points are displayed. Note that according to ETR290, only the data pilots are used for MER and EVM calculation. The samples collected are not real time, so there is some dwell (delay) before a complete constellation is displayed. The persistence of the display can be varied using the Persist slider control at the bottom of the graph.

MER and EVM calculations are performed on the constellation data according to the formulae given in ETR290-101. Note that this calculation specifically excludes the TPS carriers.

Overall SNR (all continuous pilots)

Atime-line graph of measured Signal-to-Noise Ratio is displayed, over a period of the preceding 255 seconds.

Overall MER (all data carriers)

A time-line graph of measured Modulation Error Ratio is displayed, over the preceding 255 seconds.

Linear Amplitude response (selected carriers)

A linear amplitude response is shown for the carriers selected using the carrier START and STOP controls. Allows you to view and zoom in on frequency-dependent amplitude distortions.

Impulse response

Achannel response graph is shown, allowing time-related distortions, particularly echoes, to be displayed relative to the main signal. Echoes occurring before and after the main signal are displayed. It is derived form the linear amplitude response, transformed into the time domain.

MTM400 MPEG Transport Stream Monitor User Manual

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