Furuno NAVNET 1823C - Manual (Page 68)

2. RADAR OPERATION
2-32
2.24 Suppressing Second-trace Echoes
In certain situations, echoes from very distance targets may appear as false
echoes (second-trace echoes) on the screen. This occurs when the return echo
is received one transmission cycle later, or after a next radar pulse has been
transmitted.
Second-trace
echo
Tx repetition
Actual range
False echo
range
Second-trace echoes
To activate or deactivate the second-trace echo rejector do the following:
1. Press the [MENU] key.
2. Press the RADAR DISPLAY SETUP soft key.
3. Use the trackball to select 2ND ECHO REJECTION, then press the EDIT soft
key.
4. Choose ON or OFF as appropriate, then press the ENTER soft key.
5. Press the [MENU] key to close the menu.