Onwa Marine Electronics KR-12X8 - Manual (Page 44)

4. FALSE ECHOES
Occasionally false echoes appear on the screen at positions where there is no
target. In some cases the effects can be reduced or eliminated. The operator
should familiarize himself or herself with the appearance and effects of these
false echoes, so as not to confuse them with echoes from legitimate contacts.
4.1 Multiple Echoes
Multiple echoes occur when a short range, strong echo is received from a ship,
bridge, or breakwater. A second, a third or more echoes may be observed on the
display at double, triple or other multiples of the actual range of the target as
shown in Figure 4-1. Multiple reflection echoes can be reduced and often removed
by decreasing the sensitivity or properly adjusting the A/C SEA.
4.2 Side-lobe Echoes
Every time the antenna rotates, some radiation escapes on each side of the
"side-lobes." If a target exists where it can be detected by the
side-lobes as well as the main-lobe, the side-lobe echoes may be represented on
both sides of the true echo at the same range, as shown in Figure 4-2. Side-lobes
show usually only at short ranges and from strong targets. They can be reduced
through careful reduction of the sensitivity or proper adjustment of the A/C SEA.
beam called
Figure 4-1 Multiple echoes
Own ship
Multiple
echo
True
Echo
37