Chapter 7: Using the Radar 153SeaRadar echoes from waves around your boat can clutter the centre of the radar picture,making it difficult to detect real targets (seepage 144).Adjusting the sea mode will reduce this clutter for up to 5 nautical miles (depending onwave and sea conditions) from your boat. This has the effect of reducing the sea echoesto intermittent small dots whilst small targets remain visible and persistent. Gainlevels 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 sothat small target are not lost. It should be used when you are in harbor or in closeproximity to land.• OSH (Automatic Offshore mode) - the system continually calculates the requiredlevel of sea clutter control.• MAN (Manual mode) - this enables you to select the sea clutter level and thenadjust the settings to ensure that all close small targets are visible. On short rangescales, do not set the SEA control so high that all clutter is removed, since this couldstop you seeing echoes from close targets. The acuteness of the sea clutter curve isset up in the Radar Setup menu (seepage 171). Manual sea clutter mode should beused in conjunction with the GAIN function (described below).GainThe gain function makes the radar picture clearer by changing the sensitivity of radarreception.• 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 thereforeimprove target definition.Note:If you set the GAIN to MAN (manual), you should check it every time you changethe range scale.TuneThe tune function is used to fine tune the receiver in the scanner for maximum targetreturns on the display.Auto modeIn AUTO mode, the radar tunes itself automatically on all range scales. This is thedefault and it is recommended that you leave the TUNE function inAUTO mode, to ensure that the radar receiver is always tuned toreceive the maximum signal.
