Basic Radar Theory - Icom MR-1220 Series Instruction Manual

2
BASIC OPERATION

Basic radar theory

Radar finds targets by receiving electromagnetic radiation reflected from large vessels, bridges, or other nearby
metal objects. Receiving unwanted reflections from some objects may cause false echoes on screens where the
target does not exist.
By understanding these phenomena logically and adjusting the radar function appropriately, some of these false
echoes can be reduced.
D Multiple echoes
Multiple echoes may be displayed when a short-range
and strong echo is received from a vessel, a bridge, or
a breakwater.
Multiple echoes will be displayed beyond the target's
true echo point on the same bearing of a large target.
You can reduce them by properly adjusting
control.
See page 8 for more information on
control.
Your vessel A target
D Sidelobe echoes
Radiation escapes on both sides of the beam in the
sidelobe. If a target reflects this radiation, it will be
displayed on the screen as an echo.
Sidelobe echoes usually occur as a result of large
(strongly reflecting) targets at a short distance. You
can reduce them by properly adjusting
control.
See page 8 for more information on
control.
Sidelobes Main
beam
15
D Indirect echoes
Indirect echoes may be returned from a passing
vessel or from a reflective surface such as the mast of
your vessel.
/
SEA
/
SEA
Scanner
Multiple
echoes
True
echo
Indirect echoes from the reflective surface appear in
different orientations than direct (true) echoes, but the
distance is approximately the same for both.
/
SEA
/
SEA
True echo
Sidelobe
echoes
A target
Mast or similar
obstruction
A target
Your
vessel
Indirect
reflection
Bridge
Mirrored image
of the target
True
echo
False
echo
True echo
Indirect echo