Filter
Top Products
2. HORIZONTAL MODE
2-28
Sidelobe echo (false echo)
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 display
as a false echo as shown below.
Mainlobe
Sidelobe
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.
Sidelobe echoes
Noise
When the fishing ground is crowded with many fishing boats, the sonar is subject to
interference from ultrasonic equipment (echo sounder or sonar) on other boats as well as
those on own ship.
For instance, interference from the sonar operated on other boats will show itself on the
display as in the figure below. This interference can be suppressed by changing the Tx rate
on the COM1 menu.
Interference from sonars