Sidelobe Echo/False Echo (Horizontal Mode); False Echo (Vertical Mode) - Furuno CH-500 Operator's Manual

1. OPERATIONAL OVERVIEW
1.8.3

Sidelobe Echo/False Echo (Horizontal Mode)

While the ultrasonic wave is emitted only in the direction set by the TILT control, some
emissions are directed outside the main beam. These are called sidelobes. The ener-
gy of the sidelobe is weak in comparison to the main beam, but when the water is rel-
atively shallow and the seabed is hard, strong echoes are detected by the sidelobes.
These "false" echoes appear on the display in a manner similar to that shown in the
figure below.
Sidelobe
1.8.4

False Echo (Vertical Mode)

In shallow water (less than 100 m), unwanted echoes may appear. This phenomenon
is caused by false echoes from the previous transmission.
Reducing [TX Rate] on the [COM1] menu may lessen this effect.
1-10
Mainlobe
False echo
Fish
Bottom
school
Mainlobe echo
Sidelobe echo Sidelobe echo Sidelobe echo
Range Range Range