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Sidelobe echoes
Every time the radar pulse is transmitted, some
radiation escapes on each side of the beam,
called sidelobes. 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. Sidelobes show usually only on
short ranges and from strong targets. They can
be reduced through careful reduction of the gain
or proper adjustment of the [STC] key.
Target B
(True)
Target B
(Spurious)
Target A
Figure 3-4 Sidelobe echoes
Virtual image
A relatively large target close to your ship may
be represented at two positions on the screen.
One of them is the true echo directly reflected
by the target and the other is a false echo which
is caused by the mirror effect of a large object
on or close to your ship as shown in the figure
below. If your ship comes close to a large metal
bridge, for example, such a false echo may
temporarily be seen on the screen.
Tr ue
echo
False
echo
Own
ship
Target ship
Mirror image
of target ship
Figure 3-5 Virtual image