Furuno CH-37BB, Руководство оператора

Страница: 21 / 71

2. SONAR MODE
2-5
Point to consider
• Normally, a vertically distributed schools of fish are better sonar target than the bot-
tom, because it reflect the transmitted pulse back toward the transducer.
• In case of 3, both schools of fish (a) and (b) are presented. However midwater
schools of fish tend to be larger than bottom schools of fish and they are often dis-
played near the bottom on the display.
• It is difficult to detect bottom fish when they are not distributed vertically.
2.5.3 Suitable tilt angle
The figure below illustrates the relationship among tilt angle, depth and detection
range. Refer to it to find out the suitable tilt angle for a given depth/detection range.
Case 1 2 3
Tilt angle 30° to 40° 10° to 20° 0° to 5°
Screen
Discrimi-
nation
fish
echoes School of fish is ob-
scured by the bottom School of fish is located
above the bottom (mid-
water) School of fish is located
close to the bottom
Bottom B tt
School of fish School of fish School of fish a
School of fish School of fish School of fish a
Bottom
Bottom
School of fish School of fish a
B tt
l School of fish a
School of
fish
School of
fish
School of
fish
b
100 200 300
Depth (m)
(200) (400) (600)
(800)
20(40)
40(80)
60(120)
80(160)
100(200)
200(400)
Range (m)
400
Tilt angle and beam coverage (frequency: 113 kHz, vertical beamwidth: 11°
0°
5°
10°
15°
100m
200m
300m
17m 17m 17m 35m 35m 35m 52m 52m 52m 11° 11° 11°
Vertical width of sonar beam