Furuno CH-300 Operator's Manual page 53

Sea surface reflections
To reduce sea surface reflections, set the tilt angle to 5° or higher, 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.
10
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
distinguishes from a fish school. A wake contains many air bubbles which attenuate
ultrasonic energy, making it difficult to sound beyond the wake.
Other
ship
Own
ship
Sea surface
°
10
Sea surface
°
Sea surface reflections
Own ship's
screw noise
Wake produced
by other ship
Own ship's
screw noise
Wake
2. HORIZONTAL MODE
Tilt angle
indication
Sea surface
reflections
Own ship's wake
(produced when
own ship turned)
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