Table of Contents
Advertisement
The broadcasting norms DVB-T and DVB-T2 define a modulation parameter called "guard interval" where
echoes won't disturb the reception.
The transmission of digital data (Symbol) is interrupted during the guard interval.
A delayed (or advanced) symbol of any shorter duration than the guard interval will not disturb the reception.
A delayed (or advanced) symbol of any longer duration than the guard interval will disturb the reception.
You have to reduce the level of reception of the echoes by orienting the antenna or by selecting a more di-
rective antenna.
The Echo function of the appliance enables you to display possible echoes that disturb the received signal.
Main signal
Pre-echo
Measurements
form arrow position
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.
7849B – 7859B – 7817B
p.
75
Yellow line,
Guard interval
limit
Echos out of interval
Advertisement
Table of Contents
