NorthStar Navigation NorthStar 491 manual Picture menu, Adjusting the gain strong echoes

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The picture menu

You can adjust the appearance of echoes in five different ways:

•gain (for high intensity echoes)

•clutter (for low intensity echoes)

•noise limiter (for interference)

•hue (to choose colors and white level)

•signal level (to remove weak echoes)

Gain and clutter changes are applied only to new echoes as they appear on the right side of the screen—earlier echoes are not affected.

NOTE:

When you override the gain’s automatic settings, the tabs on the PICTURE key and AUTO key change from green to yellow, indi- cating the system is no longer in automatic mode. When you turn the noise limiter on, only the PICTURE key tab changes from green to yellow. Changing the hue or adjusting the signal level has no effect on the operating mode (the tabs stay green).

Adjusting the gain (strong echoes)

The gain setting selects the echo strengths that will be displayed using the top color in the color bar (the strongest echoes). Any echoes stronger than this selection will use the same color and no detail can be distinguished. The gain is usually set so that seabed echoes are displayed in brown, the strongest level.

The gain can be also be set automatically by pressing the AUTO key. This will provide an excellent picture under most conditions, and will allow the 491 to reliably detect the seabed depth.

Gain is normally adjusted in conjunction with clutter, as described on the next page, to maximize its effectiveness.

To adjust the gain:

1.On the ECHO screen, press PICTURE.

2.On the PICTURE screen, press GAIN.

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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 Organization Using this manualWelcome to the Northstar Conventions Hearing from you Service and repairTechnical support How echo sounding works 961/962 echo sounder system components Using 491 with the 961/962 Powering the 491 on and offSetting up 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 Chart Overlay screen Using demo modeAt the Chart Overlay Selection window, press Depth and temperature Introducing the displayed informationEcho sounding Navigation Status tabsUsing automatic mode Cruising or ﬁshing50 kHz 200 kHz Manually overriding automatic modeChanging the frequency of echoes Echo screen with both frequencies displayed Choosing the zoom scale Choosing a zoom modeZooming in and out Using bottom zoom Using bottom lock zoomUsing bottom lock/ center zoom Setup functions Accessing the setup screenEntering numerical values Changing the temperature graph’s units and scale Transducer depthChanging the depth units 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 depth marker Changing the depth settingsViewing the seabed depth 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 screenScope on dual-frequency echo screen Setting the Echo screen dataUsing the A-scope with dual frequencies Bottom depth box Temperature box Echo screen data selectionsTemperature graph Introducing snapshotsSpeed through the water 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 windowSetting the bottom alarm Setting inside or outside ﬁsh markersAlarm Turning the ﬁsh alarm on and offSetting the bottom level Bottom alarm windowTemperature alarm window Setting the temperature alarmTurning the bottom alarm on and off 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 characteristicsPhysical characteristics Environmental characteristicsScreen notations InterfacingManual controls ON/OFFEcho Sounder Operations Manual Glossary Echo Sounder Operations Manual