Furuno CH-37 Operator's Manual page 38

Furuno color sector scanning sonar operator's manual model ch-37

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Sidelobe

2-22

False echo by sidelobe

An ultrasonic wave is emitted only in the direction set by the

TILT control, however there are some emissions outside the

main beam. These are called sidelobes. The energy of the

sidelobe is fairly weak but when the water is comparatively

shallow and the bottom is rocky and hard, strong signals are

detected by the sidelobe. These are represented on the dis-

play as a false echo as shown below.

Mainlobe

Figure 2-21 Sidelobe echoes

Mainlobe echo

Sidelobe echo

The bottom echo

detected by sidelobe

appears at a certain

tilt angle when the

sidelobe points ver-

tically. Also, poor

soundome projection

may result in a similar

false echo.

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Troubleshooting