Raymarine C Series - Manual (Page 145)

Chapter 6: Using the Radar 131
Sea
Radar echoes from waves around your boat can clutter the centre of the radar picture,
making it difficult to detect real targets (see
page 122 ).
Adjusting the sea mode will reduce this clutter for up to 5 nautical miles (depending on
wave and sea conditions) from your boat. This has the effect of reducing the sea echoes
to intermittent small dots whilst small targets remain visible and persistent. Gain
levels further from your boat remain unchanged. There are three sea gain modes:
• HBR (Automatic Harbor mode) - this takes account of the effects of land clutter so
that small target are not lost. It should be used when you are in harbor or in close
proximity to land.
• OSH (Automatic Offshore mode) - the system continually calculates the required
level of sea clutter control.
• MAN (Manual mode) - this enables you to select the sea clutter level and then
adjust the settings to ensure that all close small targets are visible. On short range
scales, do not set the SEA control so high that all clutter is removed, since this could
stop you seeing echoes from close targets. The acuteness of the sea clutter curve is
set up in the Radar Setup menu (see
page 149 ). Manual sea clutter mode should be
used in conjunction with the GAIN function (described below).
Gain
The gain function makes the radar picture clearer by changing the sensitivity of radar
reception.
• For long ranges - select a sensitivity level that gives a slight speckle in the back-
ground. Be careful not to set the gain too low, or you may miss weak or small tar-
gets.
• For shorter ranges - reduce the gain slightly to reduce the speckle and therefore
improve target definition.
Note: If you set the GAIN to MAN (manual), you should check it every time you change
the range scale.
Tune
The tune function is used to fine tune the receiver in the scanner for maximum target
returns on the display.
Auto mode
In AUTO mode, the radar tunes itself automatically on all range scales. This is the
default and it is recommended that you leave the TUNE function in
AUTO mode, to ensure that the radar receiver is always tuned to
receive the maximum signal.
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