Tektronix MTM400 - Manual (Page 164)

Interface Configuration and Interpretation
3-120 MTM400 MPEG Transport Stream Monitor User Manual
Input Card Screen - QAM Annex B II
Figure 3-43: Input card screen - QAM Annex B II (example)
Two LED indicators are available on the Readings section of the screen:
FEC Lock Forward Error Correction Lock, which displays the status of the
deinterleaver and Reed Solomon decoder.
RF Lock If full lock is acquired onto the channel and it is receiving the
signal correctly, the RF Lock indicator will light up green. When
a signal is present but no lock is achieved, the indicator is red.
When no signal is found, the indicator is gray.
The following graphs, which can be selected from the Graph drop-down list, are
available when the QAM (Annex B) interface card is installed:
RF Constellation I and Q data are collected from the QAM front end and
displayed as a conventional constellation of 256 points by 256
points. 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.