Alcad 918 Serie Manuel D'utilisation page 183

Relative amplitude in dB and delay in μs (distance in km) from the main signal (0 pulse) can be measured.
The yellow line represents the end of the guard interval.
Echoes and pre-echoes (pulses) above the yellow line disturb the signal and must be reduced as much as
possible.
The echoes (pulses) beyond this line disturb the reception and must be as weak as possible.
Attention: a high amplitude echo pulse within the guard interval will also disturb the signal
quality.
74