NorthStar Navigation NorthStar 491 manual Adjusting the signal level weak echoes, Clutter window

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displayed. If you select 5, for example, all weak and moderate echoes will be displayed using the background color (just as if they weren’t there). You might choose this setting to eliminate high levels of background noise and echoes from turbulence or plankton. A setting of 0 allows all echoes to be displayed.

To adjust the clutter:

1.At the ECHO screen, press PICTURE.

2.At the PICTURE screen, press CLUTTER.

3.Press the CURSOR PAD left or right to adjust the clutter, or use the KEYPAD to manually enter the desired clutter value. The available settings range from zero (minimum) to nine (maximum).

Clutter window

4. Press RETURN to go back to the ECHO screen.

When you adjust the clutter, the color of the AUTO and PICTURE key tabs changes from green to yellow, since the echo sounder is no longer in fully automatic mode.

Adjusting the signal level (weak echoes)

As with the CLUTTER key, the SIGNAL LEVEL key controls the appearance of low level noise in the picture. Whereas clutter compresses or expands the available colors to fit the

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491 Echo Sounder Operations Manual

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Contents Northstar Echo Sounder Contents Reviewing past echoes using SoundTrac Troubleshooting 491 OperationsPage 1Welcome Welcome to the Northstar Using this manualOrganization Conventions Technical support Service and repairHearing from you How echo sounding works 961/962 echo sounder system components Setting up Powering the 491 on and offUsing 491 with the 961/962 Using the 491 with the 957/958 Press the Port Setup Options key961/962 echo sounder menu structure 957/958 echo sounder menu structure 2Quick Start Using the Echo Sounder Displaying the echo sounder’s picture Illustrated Echo screenIllustrated Soundtrac screen At the Chart Overlay Selection window, press Using demo modeChart Overlay screen Echo sounding Depth and temperatureIntroducing the displayed information Navigation Status tabsUsing automatic mode Cruising or ﬁshingChanging the frequency of echoes Manually overriding automatic mode50 kHz 200 kHz Echo screen with both frequencies displayed Zooming in and out Choosing a zoom modeChoosing the zoom scale Using bottom zoom Using bottom lock zoomUsing bottom lock/ center zoom Setup functions Accessing the setup screenEntering numerical values Changing the depth units Changing the temperature graph’s units and scaleTransducer depth Number of special waypointsSpeed and temperature sensor setup 961/962 sensor setup screen957958/ sensor setup screen 3Adjusting the Echo Sounder Picture Adjusting the gain strong echoes Picture menuAdjusting the clutter weak echoes Gain windowAdjusting the signal level weak echoes Clutter windowSuppressing interference the noise limiter Selecting the color bar hue and white level Understanding the color barSetting the white level Hue and white level windowEcho Sounder Operations Manual 4Understanding Depth Settings Viewing the seabed depth Changing the depth settingsViewing the depth marker Setting the picture’s shift starting depth Shift windowSetting the picture’s range Range window Echo Sounder Operations Manual 5Other Functions Using the More key Using the More key Changing the advance speedDisplaying the A-scope Scope on single-frequency echo screenUsing the A-scope with dual frequencies Setting the Echo screen dataScope on dual-frequency echo screen Bottom depth box Temperature box Echo screen data selectionsSpeed through the water Temperature graphIntroducing snapshots Taking and storing a snapshotArchiving and restoring a snapshot with a ﬂoppy disk Snapshot screen 961/962 onlyArchiving and restoring snapshots with a Zip disk Archiving snapshots screen 961/962 onlySetting up the video image overlay Echo Sounder Operations Manual 6Reviewing past echoes using SoundTrac Viewing past echoes using SoundTrac SoundTrac screenMarking ﬁsh as waypoints Navigating to a past echo positionGoing directly to a past echo position Selected Cursor Position window appears7Setting the Alarms Understanding the alarms Setting the ﬁsh alarmSetting the upper and lower marker depths Fish alarm windowAlarm Setting the bottom alarmSetting inside or outside ﬁsh markers Turning the ﬁsh alarm on and offSetting the bottom level Bottom alarm windowTurning the bottom alarm on and off Setting the temperature alarmTemperature alarm window Turning the temperature alarm on and off Upper limit window is highlighted in blackWhen the temperature alarm sounds, an alert message is 8Troubleshooting 491 Operations Troubleshooting the echo sounder Checking the transducerTroubleshooting the echo sounder No echoes displayed when Star key is pressedChecking the transducer OFFManufacturer Model Power Northstar P/N Maintaining a transducerA491 Features and Speciﬁcations Performance characteristicsScreen notations Physical characteristicsEnvironmental characteristics InterfacingManual controls ON/OFFEcho Sounder Operations Manual Glossary Echo Sounder Operations Manual