NorthStar EXPLORER 457 Installation And Operation Manual page 18

Bottom types
Mud, weed and sandy bottoms tend to weaken
and scatter the sonar pulse, resulting in a weak
echo. Hard, rocky or coral bottoms reflect the
pulse, resulting in a strong echo.
Frequency and cone width
The sonar pulse
generated by the 457/467
transducer travels down
through the water,
spreading outwards in
a cone shape. The cone
width is dependent
upon the frequency of
the pulse; at 50 kHz it
is approximately 45°,
and at 200 kHz it is
approximately 11°.
The differences in the
cone width affect what is
displayed. See
section 3-3.
18
Water
Depth
25
50
100
150
200
300
400
600
800
1000
Northstar FISH 457/467 Installation and Operation Manual
Cone width
at 50 kHz
20
40
80
45° cone
130
170
250
330
500
660
830
Cone width
at 200 kHz
5
10
20
11°
30
cone
40
60
80
120
150
190