381295/B
39
As the distance from the bottom to the fish increases, the fish echoes become clearer.
However, this assumes that the fish echoes are considerably stronger than the bottom
echoes.
• If you use a very small tilt (C) you are not bothered by bottom echoes. However, if the
sea surface is gusty you will see echoes from the waves. These echoes are normally
rather weak, and they hardly move in relation to your vessel.
• By means of a medium tilt angle (B) you are able to pick up scattered fish or schools
if these are located at some distance above the bottom. The upper school in the
illustration appears on the sonar picture before the bottom echo, while the lower
school will easily be disguised by the bottom echoes. Once again you can activate the
RCG function to improve the reading.
Tip
With the various beams provided by the SN90, it may be difficult to understand
the concept. How do these beams "behave" in the water? By means of a graphic
presentation, the
Beam Visualization
dialog box attempts to give you a better
understanding of how the acoustic beams are transmitted into the water. Open the
Beam
Visualization
dialog box from the
Setup
menu.
Procedure
1
In a
Vertical
view, click on the tilt line, keep the mouse button depressed, and drag
the line up or down.
Optionally:
2
Click in any view to make it active.
The active view is identified with a thicker border. Unless you use the
Apply to all
function, all changes you make will only be applied to this view.
3
Observe the
Main
menu.
Its default location is on the right side of the SN90 presentation.
4
Select
Tilt
.
5
Make the necessary adjustment.
The following methods can be used to adjust this setting:
a
Select [
+
] or [
-
] to choose the requested setting.
b
Place the cursor on the button. Press and hold the left mouse button. Move the
cursor horizontally over the button. Release the mouse button when requested
value is shown.
c
Select the middle of the button to open it. If you have a keyboard connected to
the SN90, type the requested value.
Summary of Contents for SN90
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