Simrad SN90, Operator'S Manual

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381295/B
At 0° tilt the sonar beam is transmitted parallel with the sea surface, while 80° tilt will
direct it towards the bottom.
The challenge is to find a tilt that prevents the fish echoes to be "buried" in reverberation
and bottom echoes.
• If you use a high tilt value (A) the fish are easily disguised by bottom echoes. A
strong RCG (Reverberation Controlled Gain) setting will remove the bottom echoes.
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 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.
2 In a Vertical view, click on the tilt line, keep the mouse button depressed, and drag
the line up or down.
Optionally:
Simrad SN90 Operator Manual