Navman TRACKFISH 6600 Installation And Operation Manual page 34

Frequency and cone width
The sonar pulse
generated by
the TRACKFISH
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 8-3.
Shadows
Shadows are created around areas where the ultrasonic beam cannot 'see'. These areas include
hollows on the bottom or beside rocks and ledges, where the strong echoes returned off the rocks
obscure the weak echoes of the fi sh and may also create a double bottom trace. See following
for an example of the sonar display in such an environment. A double bottom trace is shown on
the display.
When looking for fi sh with the wide angled 50 kHz frequency, be aware of increased shadows. Use
the high frequency 200 kHz in areas that have rocks and ledges because this frequency reduces
the shadow effect considerably.
Example of shadows
TRACKFISH 6600 Installation and Operation Manual
Water
Depth
25
50
100
150
200
300
400
600
800
1000
fi sh is visible on the display
fi sh is hidden by the strong echoes off the
bottom and is not shown on the display
fi sh is visible on the display
Cone width
at 50 kHz
20
40
80
45° cone
130
170
250
330
500
660
830
Sonar display of same area
NAVMAN
Cone width
at 200 kHz
5
10
20
11°
30
cone
40
60
80
120
150
190
35