Simrad GB40, Manual

Page: 94 / 156

Echo strength variability
The colors on the Echosounder pane indicate differences in the
strength of the echoes. However, when you're trying to interpret
the strength of an echo, remember that it can be affected by many
factors such as:
•
the size of the object (bigger objects return more echoes).
•
the depth of the object and the sonar frequency you've
selected.
•
the location of the object relative to the position of your vessel.
The area of water covered by the sonar pulse is roughly cone-
shaped and spreads out and down from your vessel so echoes
are returned most strongly from the central area under the
transducer.
•
the clarity of the water. Particles or air bubbles in the water
can reduce the strength of echoes. Planing hulls moving at
speed can produce air bubbles and turbulent water that may
create transducer interference. Using the 200 kHz frequency
can reduce the amount of noise.
•
the composition and density of the object, such as a bed of
seaweed or a rocky bottom.
7.4 Echosounder: Operating modes
¾
To change the operating mode:
•
Display the Echosounder pane and the main menu. If you can't
see the
Auto Mode
button, select
Return
.
•
The
Auto Mode
button shows the current setting. Select it to
change the setting. There are 3 operating modes:
◦ Fishing
- the range and gain settings are automatically
adjusted to suit fishing conditions.
◦ Cruising
- the range and gain settings are automatically
adjusted to suit cruising conditions.
◦ Manual
- you can change the range and gain settings
yourself. The Echosounder will store your most recent
settings and use them until you change them again.
Note: If you operate the Echosounder manually, you can
change the range and gain to suit your own preferences. The
best results are often returned in manual mode but the
optimum settings for different conditions are usually found
only with practice and experience.
Note: If you're using Fishing or Cruising mode and adjust the
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