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Radar uses a form of electromagnetic radiation, which like light, can be reflected. Because of this property, some
objects may cause false echoes on the screen where in fact no targets actually exist.
These echoes may appear if a large vessel, bridge, or tank is in proximity. Operators should be familiar with the ef-
fects of these phenomena. In some cases, echoes can be reduced.
I Side-lobe echoes
Radiation can escape on each side of the beam inside
the lobes. If a target reflects this radiation, it will be dis-
played on the screen as an echo.
Main beam
Side lobes
I Indirect echoes
Indirect echoes may be returned from either a passing
ship, or returned from a reflecting surface, such as a
mast on your own ship.
Scanner
Mast or
similar obstruction
Target
Own ship
Bridge
An echo is reflected at this point.
BASIC RADAR THEORY
Side-lobe echoes usually occur at short ranges and as
a result of large (strongly reflective) targets. They can
be
[SEA]/[
See p. 10 for the [SEA]/[
An indirect echo from a reflecting surface will appear
on a different bearing from the direct (true) echo, but
the distance will be approximately the same for both.
Target
Indirect echo
reduced
with
proper
] control.
False
echoes
True echo
8
adjustment
of
the
] control.
True
echo
True echo
False echo
21
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