Furuno CH-500, Руководство оператора

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1. OPERATIONAL OVERVIEW
1-9
1.8 Noise and Interference
Ultrasonic noise and interference can make it difficult to see the echoes you want to
see on the screen. Depending on the cause, your sonar can “adjust” the picture, either
by suppressing noise and interference, or by changing the transmission rate.
The following sections cover the more common causes of noise and interference.
1.8.1 Sea Surface Reflections (Horizontal Mode)
When a tilt is set at a low angle, sea surface reflections cover a large area of the dis-
play, making it difficult to read.
To reduce sea surface reflections, set the tilt angle to 5° or higher so that the upper
edge of the sonar beam does not hit the surface, or adjust the TVG.
1.8.2 Wake Noise (Horizontal Mode)
The wake from own ship or other ships can cause “noise” which is shown as a dark
reflection on-screen, when the tilt is at a low angle. The wake appears as a thick, con-
tinuous line and is easily distinguished from a fish school. However, because the air
bubbles in the wake attenuate the sound beam, it is often difficult to “see” beyond the
wake.
To avoid wake noise, wait until the wake has settled before checking the screen.
Tilt angle 0°
Tilt angle 5° to 7°
Other ship
Own ship
Own ship
Tilt: 0° to 5°
Own ship's
screw noise
Wake produced by
other ship
Own ship's wake
Own and other ship
'
s screw noise Own ship
'
s screw noise