Contents
1 Welcome
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Welcome to the Northstar 491
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Using this manual
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Technical support
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How echo sounding works
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Powering the 491 on and off
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Setting up the 491
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2 Quick Start: Using the Echo Sounder
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Displaying the echo sounder’s picture
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Using demo mode
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Introducing the displayed information
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Using automatic mode
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Changing the frequency of echoes
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Zooming in and out
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Setup functions
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3 Adjusting the Echo Sounder Picture
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The picture menu
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Adjusting the gain (strong echoes)
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Adjusting the clutter (weak echoes)
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Adjusting the signal level (weak echoes)
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Suppressing interference (the noise limiter)
. 31
Selecting the color bar (hue) and white level
32
4 Understanding Depth Settings
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Viewing the seabed depth
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Viewing the depth marker
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Changing the depth settings
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Setting the picture’s shift (starting depth)
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Setting the picture’s range
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5 Other Functions: Using the MORE key
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Using the MORE key
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Changing the advance speed
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Displaying the A-scope
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Setting the ECHO screen data
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