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47
BASIC RADAR THEORY
■ Indirect echoes
Indirect echoes may be returned from either a
passing vessel, or returned from a reecting surface,
such as a mast on your own vessel.
Target
Scanner
Mast or
similar obstruction
An echo is reflected at this point.
Your ship
Target
Bridge
An indirect echo from a reective surface will appear
on a different bearing from the direct (true) echo, but
the distance will be approximately the same for both.
■ Sidelobe echoes
Radiation can escape on each side of the beam
inside the sidelobes. If a target reects this radiation,
it will be displayed on the screen as an echo.
Sidelobe echoes usually occur at short ranges and as
a result of large (strongly reective) targets. They can
be reduced with proper adjustment of the
/
control.
See page 9 for details of the
/
control.
Radar uses a form of electromagnetic radiation that can be reected off a large vessel, bridge, or other metal
objects that are in proximity. Because of this property, unwanted reections off some objects may cause false
echoes to appear on the screen where in fact no actual targets exist. Operators should be familiar with the effect
of this phenomena. In some cases, echoes can be reduced.
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