BASIC RADAR THEORY 8
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.
■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
be reduced | with proper | adjustment of the |
[SEA]/[ | ] control. |
|
See p. 10 for the [SEA]/[ | ] control. | |
True echo
False echoes
■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.
Target
Scanner
Mast or 
similar obstruction
Target
Own ship
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.
True echo
False echo
True echo 
Bridge 
Indirect echo 
An echo is reflected at this point.
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