Deviser S7200 User Manual page 53

DVB-T/H Echo Pattern
 Post-echo: In this scenario, the strongest path
(main path) leads from the nearest transmitter
tower, and the other paths are either from
transmitters located further away or from
reflections which arrive after the main path and
have lower power levels. (Below, only one echo
is shown.)
 Pre-echo: Pre-echoes often occur when there
are repeaters nearby. In this scenario, the main
path is re-transmitted from the repeater and
doesn't arrive first. The LOS (line of sight) path
arrives first but has a lower power level.
 Pre-echoes and post-echoes: This scenario
occurs when both a pre- and post-echo exist
in the transmission channel. The main path is
re-transmitted from the repeater. The LOS
signal arrives first but it has a lower power
level and the paths that arrive later may be
from reflections.
 Impulse response: Here, the main path signal is at the center of the pattern (below). On the left
side of the main path is pre-echo, on the right is post-echo. The non-shaded area shows the
guard interval. Different guard interval settings produce different shaded areas in the echo
pattern. In the echo list, tap an echo entry to move the marker there. You can also view the
distance and delay time from the echo transmitter to the main transmitter.
Part II: Settings and Measurements
53