Instruction Manual

47
BASIC RADAR THEORY
■ Indirect echoes
Indirect echoes may be returned from either a
passing vessel, or returned from a reecting 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 reective surface will appear
on a different bearing from the direct (true) echo, but
the distance will be approximately the same for both.
Tr ue echo
False echo
Indirect echo
Tr ue echo
■ Sidelobe echoes
Radiation can escape on each side of the beam
inside the sidelobes. If a target reects this radiation,
it will be displayed on the screen as an echo.
Main beam
Sidelobes
Sidelobe echoes usually occur at short ranges and as
a result of large (strongly reective) targets. They can
be reduced with proper adjustment of the
SEA
/
control.
See page 9 for details of the
SEA
/ control.
False
echoes
Tr ue
echo
Radar uses a form of electromagnetic radiation that can be reected off a large vessel, bridge, or other metal
objects that are in proximity. Because of this property, unwanted reections 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.
9
MR-1010RII / Page 13-52