False Echoes - Raytheon Pathfinder 1200 Instruction Manual

2.5
FALSE ECHOES
Occasionally, signals appear on the screen at positions where there is no target. They
are false echoes.
The following are known as most common false echoes.
2.5.1 Side Echoes
Some radiation escapes on each side of the main beam in side lobes. If they are re-
flected by a target, they will be displayed on the screen as an echo. (See Figure 2-6)
These echoes appear as arcs form echoes at each side of the true echo. Sometimes joined
together if the side echoes are strong.
SIDE ECHOES
TRUE ECHO
FIG. 2-6 SIDE ECHOES
2.5.2 Indirect Echoes
As shown in Figure 2-7, indirect echoes may appear if there is a large target, such as
a passing ship, at a short range or a reflecting surface, such as a funnel, on your own ship.
The signal, on first striking the smooth side of the large target, will be deflected. Then
it encounters a second target, the echo will return along the same paths to the scanner.
Thus, the echo from the second target will appear beyond that of the large target but on
the same bearing. The indirect echoes will also appear when the signal will be deflected
by the reflecting surface.
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