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Chapter 6: Using the Radar 121
Side lobes
Side lobe patterns are produced by small amounts of energy from the transmitted
pulses that are radiated outside the narrow main beam.
The effects of side lobes are most noticeable with targets at short ranges (normally
below 3 nm), and in particular with larger objects. Side lobe echoes form either arcs on
the radar screen similar to range rings, or a series of echoes forming a broken arc.
Indirect echoes
There are several types of indirect echoes or ghost images. These sometimes have the
appearance of true echoes, but in general they are intermittent and poorly defined.
True echo Side echoes
Main lobe
Antenna
Arc
Side
lobe
Side
lobe
D1638-4
False echo
Passing
ship
True echo
D1641-4
True echo
False echo
Mast
or funnel
81221_4.book Page 121 Tuesday, February 28, 2006 5:24 PM