NorthStar Navigation EXPLORER 657 Sonar A-Scope display, Setting gain and threshold, Bottom type

Page 43

9-5 Sonar A-Scope display

A

BE

D

The display shows the sonar history on the left and the A-Scope display on the right. The A-Scope shows:

A, B, C The strengths of echoes being received now from different depths - the longer the horizontal line the stronger the signal:

AUnwanted noise echoes.

BEchoes from fish and the bottom

CThe strongest echo, usually from the bottom

D A vertical line showing the threshold, the

weakest echo to display on the sonar history

B

A

C

EA vertical line showing the gain setting; echoes above this strength will display as the maximum signal strength

Use the A-Scope while adjusting the gain and threshold settings manually (see section 8-6).

Setting gain and threshold

It is convenient to use the A-scope display when adjusting gain and threshold manually. Follow this procedure to adjust gain and threshold for normal circumstances:

1Switch to a sonar display (see section 9). If

necessary, press or to adjust range so that the bottom is displayed.

2If necessary, select the sonar frequency to

adjust the settings for. Press , select

Frequency and select 200 kHz or 50 kHz.

3Press , select Sonar splits then select Split A-scope.

4Press to display the Gain window. To

adjust gain or threshold for a frequency, press or to select the setting to adjust, then press or to change the setting.

5Set threshold to zero.

6Adjust Gain so the peak of the strong signal from the bottom just touches the gain line.

7Adjust threshold so that it is just to the right of the noise.

8Press to close the gain window.

9If required, repeat these steps to adjust gain and threshold for the other frequency.

Note: Setting the gain higher will display more detail from weak echoes, like fish, but will loose detail from the strong echo from the bottom.

Fish recognition

The echo strengths shown on the A-scope can be useful in recognising the type of fish. Different species of fish have different sizes and shapes of swim bladders. The air in the swim bladder reflects the ultrasonic pulse, so the strength of the echo varies between fish species according to the size and shape of the swim bladder.

When catching fish from a school, note the species and the strength of the echo that it returns on the A-scope. Then, when that particular echo is seen again, it is likely to be the same fish species.

Bottom type

The shape of the echo strengths in the A-Scope can help you to recognise the type of bottom.

Northstar Explorer 657 Installation and Operation Manual

43

Image 43
Contents Explorer Damage Possible injury or deathCould result in death or serious injury Could result in minor or moderate injuryPage Contents Tides window User card window 15 AIS Installation Other Nmea instruments Installation Northstar petrol/gasoline sensorsIntroduction 657 can use two kinds of plug-in card Cleaning and maintenanceOverview Plug-in cardsReplacing the display unit Changing the plug-in cardRemoving the display unit Turn the display unit off see -2 and put the dust cover onOverview of the keys Using the keysUsing the menus Basic OperationTurning off manually Turning on and off / auto power Turning on manuallyMan overboard MOB Backlight and night modeNight mode To cancel MOB or set another MOBSimulate mode Alarms657 has user settable alarms see section Main windows Page Multi window displays Deleting a favorite display from the list Favorite displaysSelecting a favorite display Adding a favorite display to the listDisplays can show data at the top, called the data header Setting the data header for a displayData header CompassNavigating to a point Navigation ChartGoing to a waypoint or to a point on the chart Introduction to navigatingStarting a route from the routes window Starting a route from the chart windowCancelling a route PreparingLand Sea Cursor see section Typical waypoint see section Chart windowTo go to the Chart window, press then select Chart Typical chart window showsLatitude and longitude Chart modesChart scale Chart symbols and informationProjected course Finding a chart symbolPerspective view Distance and bearing calculatorInterval Track Track 2, 3, 4 or Navigation Highway windowTracks and tracking Time intervals Interval Track Track 2, 3, 4 orWaypoints window Navigation WaypointsMoving a waypoint Displaying a waypoint on the chartManaging waypoints Creating a new waypointSort Waypoints Navigation RoutesDeleting all waypoints Changing a waypoint’s dataCreating a new route Creating a new route from the chart windowRoutes window Managing routesCreating a new route from the routes window Displaying a route on the chartEditing a route from the chart Editing a routeSatellites Satellite window shows UsingSonar fishfinding Introduction Satellite windowStrength of echoes Interpreting the displayDepth Bottom typesFrequency and cone width WaterExample of shadows When to use 50 kHzWhen to use 200 kHz ShadowsWhen to use 50/200 kHz When to use MixedMinute ago Seconds ago Now KHz display 200/50 Khz display Mixed displayFish symbols Fish detection and display Where to find fishFish arches Zoom range and offset Range657 has two range modes AutoThis display is called the gain window Changing modeGain and threshold Gain windowSonar history display no split Sonar fishfinding DisplaysHistory position bar Extended history modeSonar Zoom and Full Screen Zoom displays Screen. Press to return to the most recent echoSonar 50/200 display Sonar Bottom displayBottom type Setting gain and thresholdSonar A-Scope display Fish recognitionChanging a gauge layout Gauges windowData window Selecting a Gauges layoutFuel window shows Fuel functions and displayWhat the fuel computer does Fuel windowWhen you add or remove fuel When you remove fuel Low fuel alarmBoat speed sensors Speed Log Economy Range Water speed and ground speedSpeed Log Economy Press twice, then select Fuel Fuel consumption curvesMaking a curve Start running the boat in a straight lineSelecting a curve Using a curveRenaming a curve Deleting a curveCalibration Setup enginesTo the reading of the fuel dispenser’s gauge Then press Tides window Choosing the date of the tide chartTides window shows data for the chosen date User card window has User card windowSaving data to the user card Rereading the file information 15 AISDeleting a file from the user card Sorting the file namesViewing AIS Vessels Displaying Full AIS Details Safety msgs rxAIS Windows VesselsDisplays Distress Poll 16 DSC/Buddy track windowsDeleting a boat Using the displays Displaying a boat on the chartBoat positions Creating a waypointSetting up SmartCraft Setup option menusTime see Favorites see 17-14 Simulate see Language Setup SystemAuto power off Factory resetPalette Setup ChartSetting map datum RotationMap shift Nmea datum offsetMap shift Applying a map shiftLat/lon grid Digit size Setup SonarPulse power FrequencyDgps Source Setup GPSSetup Fuel GPS SourceNum engines Setup enginesSetup tanks SourceRecord Setup TrackDistance TimeReset engine hours Setup AIS Show Dangerous OnlySetup Logs Reset total distAlarm sounds when it is on Setup AlarmsSymbol Alarm Arrival radius Anchor alarmFuel Setup UnitsTemperature Setup CommsSpeed filter Setup CalibrateTemperature filter SpeedSpeed range Setup TimeSetup Favorites Keel OffsetMode InstallationSetup Simulate SimulateGPS or Dgps antenna For GPS navigation see section Installation What comes withInstallation Options and Accessories Optional sensors and instrumentsDisplay unit 18-3 Black Yellow Blue Power/data cablePin Wire Function ConnectionsThere are two mounting arrangements Installation The display unitFlush Mounting Bracket MountingAuto power Installation Power/data cableBasic power Black Power/data cable Red Yellow Fuse 2AInstalling an antenna Installation GPS antenna Selecting an antennaDgps Source Installation Northstar petrol/gasoline sensors Installation Sonar transducerBlue Sonar cable Either Installation Other NavBus instruments Installation SmartCraftNavBus Installation Other Nmea instruments Installation Northstar VHF radioTilt and rotation for best viewing and hand Installation Setup and testEnter setup data to set up the 657 to your If the display unit is bracket mounted, adjustAppendix a Specifications Adindan Afgooye List of datumsSouth American General problems Appendix B TroubleshootingFuel consumption problems GPS navigation problemsThere is no reading for fuel economy Sonar fishfinding problemsTwin engine installation shows only one flow rate Erratic Fuel Flow readingsBottom is displayed too far up the screen Bottom is not displayedThere is a double bottom trace displayed Glossary Appendix C Glossary and navigation dataNavigation data TBMFT!COUNBSJOFDPN