Furuno CH-270 - Manual (Page 48)

2. HORIZONTAL MODE
2-28
Sea surface reflections
To reduce sea surface reflections, set the tilt angle to 5 ° or lower, so the upper edge of the
sonar beam does not hit the sea surface, or adjust TVG. When a decreased tilt angle is
used, sea surface reflections cover a large area as illustrated below.
Sea surface
Sea surface
8 °
Tilt angle
indication
Sea surface
reflections
8 °
Sea surface reflections
Wake
A wake produced by own ship or another ship can be a strong reflecting object when a
decreased tilt angle is used. As the wake appears as a thick continuous line, it can be
easily distinguished from a fish school. A wake contains many air bubbles which attenuate
ultrasonic energy, making it difficult to sound beyond the wake.
Own
ship
Other
ship
Wake produced
by other ship
Own ship's
screw noise
Own ship's
screw noise
Own ship's wake
(produced when
own ship turned)
Wake