Northstar 491 Echo Sounder Operations Manual This manual is for using the 491 sounder with the Northstar 957, 958, 961 and 962 navigators. For the Northstar 6000i, information in Section 6 of its manual can be used instead. Revision A Part Number GM494 Northstar a unit of Brunswick New Technologies Marine Electronics 30 Sudbury Road Acton, Massachusetts 01720 www.NorthstarNav.
Contents 1 Welcome . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Welcome to the Northstar 491 Using this manual . . . . . . . . . . Technical support . . . . . . . . . . How echo sounding works . . . Powering the 491 on and off . Setting up the 491 . . . . . . . . . 2 ............ ............ ............ ............ ............ ............ Quick Start: Using the Echo Sounder . . . . . . . . . 11 Displaying the echo sounder’s picture . Using demo mode . . . . . . . . . . .
Introducing snapshots . . . . . . . . . . . . . . . . . 46 Setting up the video image overlay . . . . . . . 49 6 Reviewing past echoes using SoundTrac . . . . . 51 Viewing past echoes using SoundTrac . . . . . 52 Marking fish as waypoints . . . . . . . . . . . . . . 53 Navigating to a past echo position . . . . . . . . 53 7 Setting the Alarms . . . . . . . . . . . . . . . . . . . . . . . . . 55 Understanding the alarms . . . Setting the fish alarm . . . . . . . Setting the bottom alarm . . . .
1 Welcome Welcome to the Northstar 491 . . . . . . . . . . . . . 1-2 Using this manual . . . . . . . . . . . . . . . . . . . . . . . . . 1-2 Technical support . . . . . . . . . . . . . . . . . . . . . . . . . 1-4 How echo sounding works . . . . . . . . . . . . . . . . . 1-5 Powering the 491 on and off . . . . . . . . . . . . . . 1-7 Setting up the 491 . . . . . . . . . . . . . . . . . . . . . . . . .
Welcome to the Northstar 491 Congratulations on your purchase of the Northstar 491 Echo Sounder. The 491 connects with a Northstar navigator and a third-party transducer to add echo sounding capability to the Northstar 957, 958, 961, and 962 navigators. See the Northstar 491 Installation Manual (part number GM495) for recommended transducers. You may be adding the 491 to your existing Northstar navigator for echo sounding, or you may have purchased your navigator complete with echo sounding.
Chapter 4 describes how to adjust the depth settings to choose what portion of the water under the vessel you’ll display. Chapter 5 explains other functions—the A-Scope, etc. Chapter 6 describes Northstar’s exclusive SoundTrac™ feature, for accessing past echoes and navigating back to their locations. Chapter 7 tells how to use the echo sounder’s alarms: the fish alarm, bottom alarm, and temperature alarm. At the back of the manual are a glossary and an appendix outlining the 491’s specifications.
Technical support After you follow the instructions in this manual, if you need technical support or if you have any other questions, you can contact Northstar by email, fax, phone, or U.S. mail as follows: Table 1: Contacting Northstar Email: Service: service@northstarnav.com Sales: sales@northstarnav.com Fax: Service: 978/897-1595 Sales: 978/897-7241 Telephone: 978/897-6600 or 800/628-4487 U.S. mail: 30 Sudbury Road Acton, MA 01720 Web site: www.northstarnav.
To prevent delays, it is critical that you first obtain a Return Materials Authorization (RMA) number before returning your unit to the factory. If you purchased your 491 through a dealer, to get an RMA number, call the dealer with the serial number. The 491’s serial number is located at the top of the unit. The 491 should be shipped in a properly designed carton with packing material. Please reference the RMA number on the outside of the carton.
GPS antenna 33-foot cable (part of transducer) 491 module 957/958/6000i Navigator 10-foot cable (Northstar-supplied) Ship's Power Transducer 10-foot cable (Northstar-supplied) Figure 1: 957/958 echo sounder system components GPS antenna Control Head 33-foot cable (part of transducer) 491 module 961/962 Processor 10-foot cable (Northstar-supplied) Ship's Power Transducer 10-foot cable (Northstar-supplied) Figure 2: 961/962 echo sounder system components Page 6 491 Echo Sounder Operations Manual
Powering the 491 on and off As part of its power-up sequence, the navigator automatically activates the 491. The 491 is automatically shut off by the navigator when you press and hold PWR until the screen goes dark. Setting up the 491 Your 491 should be installed by a qualified marine technician. Your satisfaction with the system’s performance will be greatly influenced by the practical knowledge and experience of the installer.
4. Check that the FORMAT option is set to “490.” If not, set it now. Using the 491 with the 957/958 Before starting, you should double-check that the navigator’s AUX port is set to the Sounder option: 1. Press STAR until you reach the OPTIONS/SERVICE INFO screen. 2. Press the PORT SETUP OPTIONS key. 3. Check that the AUX PORT option is set to “Sounder.” If not, set it now.
Figure 3: STAR key ECHO SCREEN Auto Picture Frequency Zoom Depth More Depth settings More settings Alarms Advance Speed Snapshot A-Scope Data Return Data on-screen Bottom box Temp box Temp graph Speed Return Shift Range Bottom box Return Snapshot Display Rename Archive Erase Return Picture settings Gain Clutter Noise Limiter Hue Signal level Return Alarm settings Fish alarm Bottom alarm Temp alarm Return Figure 4: 961/962 echo sounder menu structure 491 Echo Sounder Operations Manual Page
STAR key ECHO SCREEN Auto Picture Frequency Zoom Depth More Depth settings More settings Alarms Advance Speed Video A-Scope Data Return Shift Range Bottom box Return Data on-screen Temp box Temp graph Bottom box Speed Video setup Video on Return Return Picture settings Gain Clutter Noise Limiter Hue Signal level Return Alarm settings Fish alarm Bottom alarm Temp alarm Return Figure 5: 957/958 echo sounder menu structure Page 10 491 Echo Sounder Operations Manual
2 Quick Start: Using the Echo Sounder Displaying the echo sounder’s picture . . . . 2-12 Using demo mode . . . . . . . . . . . . . . . . . . . . . . . . 2-14 Introducing the displayed information . . . . 2-15 Using automatic mode . . . . . . . . . . . . . . . . . . . . 2-16 Changing the frequency of echoes . . . . . . . . 2-17 Zooming in and out . . . . . . . . . . . . . . . . . . . . . . . 2-19 Setup functions . . . . . . . . . . . . . . . . . . . . . . . . . . .
Displaying the echo sounder’s picture Once the navigator has been configured to operate with the 491, you’re ready to start viewing echo sounding data. To see the echo sounding screen at any time, press STAR from any screen. You’ll see live echoes moving across the screen.
real-time echoes. For details, see “Reviewing past echoes using SoundTrac” starting on page 51. Depth marker and indicator Depth Scale Echo data Water temperature box Color bar Position marker and indicator Water temperature scale Depth box Lat/lon of position marker Dist/brg to position marker Steering indicator Speed, course, and speed through the water Figure 7: Illustrated SOUNDTRAC screen NOTES: All of the alarm messages always appear on all of the echo sounder’s screens.
Using demo mode The echo sounder can be operated in “demo mode” for training and familiarization. Simulated echo data generated by the 491 will be displayed. To enter demo mode: 1. Press STAR several times to display the ECHO SOUNDER SETUP screen. 2. Press the CURSOR PAD down to select demo mode, then press EDIT. 3. Press the CURSOR PAD left or right to highlight “ON,” then press ACCEPT. While in demo mode, the word “Demo” appears in the upper right corner of the ECHO screen.
Introducing the displayed information The following information can be displayed on the ECHO screen.
Using automatic mode To operate the echo sounder automatically, just press AUTO. All of the 491’s adjustments will be set to produce a useful picture under most conditions. When you’re too busy to optimize the settings manually, the echo sounder can automatically set the optimal gain, clutter, and range settings, to show an excellent picture, from the surface to the bottom. When you select auto, the range setting may change from time to time to keep the seabed in view as the water depth changes.
Manually overriding automatic mode You can always manually change any of the echo sounder’s settings: the gain, clutter, noise limiter, shift, and range. Changing the appearance of the picture (colors, gain, clutter, and the noise limiter) is described in Chapter 3. Setting the range and shift is described in Chapter 6. Changing the frequency of echoes The 491 uses two transducer frequencies: 50 kHz and 200 kHz. The advantages and disadvantages of each frequency are shown below. Table 2: 50 kHz vs.
• 50 kHz echoes when adjusting the picture, you can see the effect of changes on the right side 200 kHz echoes Adjusts the frequency of the data displayed (currently showing dual frequency on a split screen, with 50 kHz to the left and 200 kHz to the right) Figure 8: ECHO screen with both frequencies displayed To change the display frequency: 1. On the ECHO screen, press FREQUENCY until you display the desired frequency or frequencies.
When using the zoom feature (which also splits the screen into halves), both sides of the screen always display the same frequency. Zooming in and out On the ECHO screen, the echo sounder’s zoom feature expands a portion of the echoes. You can examine closely any part of the water column, to determine the composition of the bottom or look at the echoes of fish, rocks, or wrecks. When fishing, the zoom function is useful for showing a detailed view of any echoes below the vessel.
• marker zoom The original unzoomed echoes are on the right side, and the magnified area is shown on the left side of the screen. A tab below the ZOOM key shows which zoom mode is in use. Using bottom zoom When you select bottom zoom, the contour of the bottom is magnified, clearly displaying canyon edges and echoes near the seabed. The 491 automatically locates the seabed and displays it on the lower left side of the screen (normal echoes are displayed on the right side).
Using bottom lock/ center zoom Using marker zoom When you select bottom lock/center zoom, the sea bottom is flattened out and displayed in the center of the screen. You can see any fish near the bottom, as with the bottom lock zoom, and also examine the seabed’s composition. When you select marker zoom, you can choose the part of the water column to magnify. The top edge of the magnified area is determined by the location of the depth marker.
the magnified area up or down, press the CURSOR PAD to move the depth marker. Leaving zoom mode You can return to the normal unzoomed display just by pressing and holding ZOOM for more than one second, or by pressing ZOOM repeatedly until you have cycled through all the zoom modes. Setup functions Several setup functions are available to configure the echo sounder to your preferences.
961/962 echo sounder setup screen 957/958 echo sounder setup screen Entering numerical values When changing the numerical value of the echo sounder’s settings, you can either press the CURSOR PAD to increase or decrease the value, or use the KEYPAD to manually type in the desired value.
Transducer depth Changing the depth units This option specifies how far below the surface of the water the transducer is mounted. The number is added to all depths measured by the 491 so they will refer to depth from the surface, not from the transducer. This value should have been set correctly during installation and should not be changed. You can change the depth units to feet, meters, or fathoms: 1. Press the CURSOR PAD up or down to highlight the DEPTH UNITS option. 2. Press EDIT. 3.
sequence number restarts at 00, and the oldest waypoints with this same name will be overwritten (unless they have been renamed). To turn this feature on or off, or to change the maximum number of each of these waypoints: 1. Press the CURSOR PAD up or down to highlight the waypoint type you want to change: The line “*Fish##*:” controls fish waypoints The line “*Therm##*:” controls temperature waypoints The line “Mark Wpts:” controls waypoints marked by the user 2. Press EDIT. 3.
957958/ sensor setup screen To simplify operation, the “sensor installed” options can be set to “No” to remove all references to temperature and speed from all the screens. Highlight the appropriate line and press EDIT to change an option. Speed calibration is entered as a percentage from –99% to +99% to make the speed read lower or higher than the uncalibrated value.
3 Adjusting the Echo Sounder Picture The picture menu . . . . . . . . . . . . . . . . . . . . . . . . 3-28 Adjusting the gain (strong echoes) . . . . . . . . 3-28 Adjusting the clutter (weak echoes) . . . . . . . 3-29 Adjusting the signal level (weak echoes) . .
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.
3. At the GAIN window, press the CURSOR PAD left or right to adjust the gain, or use the KEYPAD to manually enter the desired gain value. The available settings range from zero (minimum) to 75 (maximum). Gain window The window shows the effect of adjusting the gain. The fish symbols near the bottom of the window represent various echo strengths, and the expanding and contracting color bar above shows the colors that will be used to display these echoes.
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.
desired signal range, Signal Level completely removes the weaker colors and their echoes. To adjust the signal level: 1. On the ECHO screen, press PICTURE. 2. On the PICTURE screen, press SIGNAL LEVEL. 3. At the SIGNAL LEVEL window, press the CURSOR PAD up or down to remove the weaker color levels from the picture, or use the KEYPAD to manually enter the desired signal level. The available settings range from 1 (minimum) to 5 (maximum).
Selecting the color bar (hue) and white level Understanding the color bar The color bar displayed at the extreme left of the ECHO screen shows the range of colors used to display different echo strengths. Weaker echoes are displayed with colors near the bottom of the scale, and stronger echoes are displayed with colors near the top. You can choose any one of nine palettes of colors to represent the echo strengths from weakest to strongest.
Hue and white level window 4. Press RETURN to go back to the ECHO screen. Setting the white level You can replace any single color in the color bar with white. On the HUE AND WHITE LEVEL window, press the CURSOR PAD up or down to select that color. To remove the white level and return to using all the colors on the color bar, press the CURSOR PAD down until the white level moves off the color bar.
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4 Understanding Depth Settings Viewing the seabed depth . . . . . . . . . . . . . . . . 4-36 Viewing the depth marker . . . . . . . . . . . . . . . . 4-36 Changing the depth settings . . . . . . . . . . . . . . 4-36 Setting the picture’s shift (starting depth) . . 4-37 Setting the picture’s range . . . . . . . . . . . . . . . . 4-38 T his chapter explains how to override the system’s automatic depth settings and manually control the depth range shown on the screen, and how to use the depth marker.
Viewing the seabed depth The seabed depth (the “bottom”) is displayed in a black box at the left edge of the ECHO screen. You can change the size and location of the depth box on the ECHO screen. Its size on the SOUNDTRAC screen is always small. There are four available sizes: • small • medium • large • huge To resize the depth box or move it up or down: 1. At the ECHO screen, press DEPTH. 2. To cycle through the size choices, repeatedly press BOTTOM BOX.
you can manually override these auto values for your specific needs at any time. There are two depth settings: • shift (how far below the surface the echo sounder picture starts) • range (the depth covered by the echo sounder picture from the top of the screen to the bottom of the screen) Setting the picture’s shift (starting depth) The shift setting adjusts the depth of the top edge of echoes pictured on the ECHO screen.
In the large rectangle on the right, the blue area at the top (with waves) represents the surface of the water, and the brown area below represents the seabed. The number at the bottom is the depth of the picture, and the seabed depth is also labelled. The smaller rectangle inside the larger one represents the echo sounder’s picture. As you move the shift (and range) settings, this rectangle adjusts to show what you will see on the echo screen.
Range window The vertical black arrow in the SET RANGE window indcates the values that this window adjusts: the range of the echo sounder picture, relative to the depth of the water. The white number in the black box indicates the current range setting. 3. Press the CURSOR PAD up or down to adjust the range, or use the KEYPAD to manually enter the desired depth. 4. Press RETURN to go back to the ECHO screen.
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5 Other Functions: Using the MORE key Using the MORE key . . . . . . . . . . . . . . . . . . . . . . 5-42 Changing the advance speed . . . . . . . . . . . . . 5-42 Displaying the A-scope . . . . . . . . . . . . . . . . . . . 5-43 Setting the ECHO screen data . . . . . . . . . . . . . 5-44 Introducing snapshots . . . . . . . . . . . . . . . . . . . . 5-46 Setting up the video image overlay . . . . . . .
Using the MORE key Pressing the MORE key accesses the following functions: • alarms (described in Chapter 7) • advance speed • A-scope • data (numeric and graphic information on the ECHO screen) • snapshots (961/962 only) • video overlay setup (957/958 only) When the menu function is in use in the 961/962, the ECHO screen moves every half second, giving the picture a less than smooth appearance. Press RETURN to go back to the main screen for a normal smooth appearance.
The A-Scope shows every ping received, even when the advance speed setting causes pings to be averaged before display Displaying the A-scope The echo sounder’s A-scope lets you look closely at present or past echoes by horizontally magnifying the echo from each ping. To display the A-scope: 1. Press MORE. 2. Press A-SCOPE to turn the A-Scope on or off.
Using the A-scope with dual frequencies If you’re displaying both 50 and 200 kHz echoes, the A-scope magnifies echoes from the frequency shown on the right side of the screen. A-scope on dual-frequency echo screen Using the A-scope with zoom mode If you’re in zoom mode, the A-scope magnifies the unzoomed echoes on the right side of the screen.
Echo screen data selections Bottom depth box Press BOTTOM BOX to set the size and location of the box displaying the bottom depth (white numbers on a black background). Press this key again to cycle through the available sizes: small, medium, large, and huge. Press the CURSOR PAD up and down to set the position of the box at the left edge of the screen. Temperature box This key won’t appear unless a temperature sensor is installed and configured.
Temperature graph This key won’t appear unless a temperature sensor is installed and configured. Speed through the water Press TEMP GRAPH to turn the temperature graph on or off. The temperature graph displays an orange temperature scale at the left of the screen, and an orange line tracing out the varying water temperature measurements, superimposed on the echoes. Press SPEED to turn the Speed Through the Water display on or off. STW is displayed on the bottom right corner of the screen.
Snapshot screen (961/962 only) To rename a stored snapshot, from the SNAPSHOT screen, press the CURSOR PAD to highlight the desired slot, and press RENAME. Use the KEYPAD to enter a new name and press ACCEPT. To display a stored snapshot, from the SNAPSHOT screen, press the CURSOR PAD to highlight the desired slot, and press DISPLAY. When finished, press RETURN. To erase a snapshot from a slot, from the SNAPSHOT screen, press the CURSOR PAD to highlight the desired slot, and press ERASE.
Archiving and restoring snapshots with a Zip disk If your 961/962 has a zip drive installed, you can save up to 10 snapshots on each disk. To save a stored snapshot onto a zip disk, from the SNAPSHOT screen, press the CURSOR PAD to highlight the desired slot, and press ARCHIVE. A new screen appears displaying the 10 slots available on the zip disk. Archiving snapshots screen (961/962 only) Press the CURSOR PAD to select an empty slot on the disk, and press OK.
Setting up the video image overlay If you’ve connected the 957/958 to an NTSC-compatible device, you can display the image on the echo sounder screen. To display the video image on the ECHO SOUNDER screen, first press MORE, then press VIDEO. To change the transparency of the image while you’re displaying the ECHO SOUNDER screen, go to a different screen, press the navigator’s IN or OUT keys, then return to the ECHO SOUNDER screen.
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6 Reviewing past echoes using SoundTrac Viewing past echoes using SoundTrac . . . . 6-52 Marking fish as waypoints . . . . . . . . . . . . . . . . 6-53 Navigating to a past echo position . . . . . . . . 6-53 T his chapter describes how to use SoundTrac to view past echoes, and how to navigate to any past echo positions.
Viewing past echoes using SoundTrac On the SOUNDTRAC screen, you can use Northstar’s exclusive SoundTrac feature to look back and examine past echo data. To enable SoundTrac, at the ECHO screen, press the CURSOR PAD to the left. A dashed vertical line—called the position marker—is now displayed. Echoes from at least the past three minutes are available, depending on the depth of the water and the advance speed you’ve set.
Echoes from the last 3000 pings are stored. The number of minutes of past echo data available depends on two factors: • the depth of the water • the advance speed In deeper water, the 491 pings at a slower rate, so the echo sounder saves data over a longer period of time. A slower advance speed will have the same effect. Marking fish as waypoints The 961/962’s fish marking function lets you use SoundTrac to mark fish, wrecks, or any other objects that you see at any past echo displayed on the screen.
• to add a past echo position to the end of an already displayed route Going to a past echo position is described below. The other options are described in the Operator’s manuals for your Northstar navigator. Going directly to a past echo position To go directly to a past echo position (as long as the GPS is providing position data): 1. On the SOUNDTRAC screen, press the CURSOR PAD left or right to move the position marker to the desired position, then press GO TO.
7 Setting the Alarms Understanding the alarms . . . . . . . . . . . . . . . . 7-56 Setting the fish alarm . . . . . . . . . . . . . . . . . . . . . 7-56 Setting the bottom alarm . . . . . . . . . . . . . . . . . 7-58 Setting the temperature alarm . . . . . . . . . . . . 7-60 T his chapter describes the echo sounder’s three alarm functions (for fish, bottom, and temperature conditions): the settings for each alarm, and how to turn them on and off.
Understanding the alarms The echo sounder’s alarms work just like the other alarms. Their status is updated every second, and their messages are displayed in the following ways: • at the bottom of the ECHO screen, and also on various windows that may be overlaid onto these screens • on the ALARMS screen On this screen, you can manually “clear,” or stop, new alarms, although some are auto-clearing, and you can view old alarms, which are alarms that already have cleared.
4. Follow the instructions below for each of these five settings. Fish alarm window Setting the alarm’s echo strength level To set the fish alarm’s minimum echo-strength level: 1. At the FISH ALARM window, press SET ALARM LEVEL. 2. Press the CURSOR PAD up and down to set the echo strength level from 1 to 15, as represented on the vertical color bar. Echoes received that are strong enough to be within the crosshatched area on the vertical bar will cause an alarm (weaker echoes will be ignored).
2. Press the CURSOR PAD up or down to set the depth, or use the KEYPAD to manually enter the desired depth. The depth is displayed in the tab below the SET UPPER MKR key. To set the depth of the lower marker: 1. At the FISH ALARM window, press SET LOWER MKR. The lower marker window is highlighted in black. 2. Press the CURSOR PAD up or down to set the depth, or use the KEYPAD to manually enter the desired depth. The depth is displayed in the tab below the SET LOWER MKR key.
To set the bottom alarm: 1. At the ECHO screen, press MORE. 2. Press ALARM. 3. At the ALARM screen, press BOTTOM ALARM. The options on the BOTTOM ALARM window are on/off and the depth setting. Bottom alarm window Setting the bottom level You can set the depth level for the seabed, so that as soon as the bottom is shallower than this depth, the bottom alarm will sound.
Turning the bottom alarm on and off To turn the alarm on, at the BOTTOM ALARM window, press TURN ALARM ON. To turn the alarm off, press TURN ALARM OFF. The alarm When the bottom is detected, the alert tone sounds and the message “Bottom Collision!” is displayed. This message clears automatically after 20 seconds, and the alarm is reset. Setting the temperature alarm This alarm isn’t present unless a temperature sensor is installed and configured.
Setting the upper and lower temperature limits You can set the upper and lower temperature limits. When the water temperature is either inside or outside these limits, the temperature alarm will sound. To set the upper temperature limit: 1. At the TEMPERATURE ALARM window, press SET UPPER LIMIT. The upper limit window is highlighted in black. 2. Press the CURSOR PAD up or down to set the temperature, or use the KEYPAD to manually enter the desired temperature.
The alarm Page 62 When the temperature alarm sounds, an alert message is displayed. This message clears automatically after 20 seconds and the alarm is reset.
8 Troubleshooting 491 Operations Troubleshooting the echo sounder . . . . . . . 8-64 Checking the transducer . . . . . . . . . . . . . . . . . . 8-65 T his chapter explains how to troubleshoot the echo sounder system before returning the equipment for factory service.
Troubleshooting the echo sounder No echoes displayed when STAR key is pressed. Is the Advance Speed set to zero? YES Change the Advance Speed setting. NO Contact Northstar Service to upgrade to the latest version of 961/962 software. NO Is the 961/962 software Version 3.0 or greater? YES Configure NMEA Port 3 for the 491. See Section 1 of this manual for instructions. NO Has NMEA Port 3 been configured for the 491? YES 491 is communicating with the navigator 1.
No echoes displayed on sounder screen. Is the Advance Speed set to zero? YES Change the Advance Speed setting. NO Configure the navigatorʼs Aux Port for the 491. See Section 1 of this manual for instructions. NO Has the navigatorʼs Aux Port been configured for the 491? YES 491 is communicating with the navigator. 1. Check fuses and circuit breakers. 2. Check power to 491 with a voltmeter. 3. Verify that the data cable between the navigator and the 491 is properly wired and connected.
transducer. The models below can be purchased from Northstar. Table 3: Northstar-recommended transducers Manufacturer Model Power Northstar P/N Airmar B260 1 kW TD1004 Airmar B744V (w/3-wire speed) 600 W TD1005 Airmar P66 600 W TD1006 Airmar Technology Corporation may be reached at 35 Meadowbrook Drive, Milford, New Hampshire 03055-4613; phone 603/673-9570; fax 603/673-4624. NOTE: Detailed information on maintaining and troubleshooting a transducer is outside the scope of this manual.
A 491 Features and Specifications Table 4: 491 echo sounder features Performance characteristics Output Single/Dual Channel, 50/200kHz, 600W Alarms Fish, seabed, temperature Update rate 10 Hz maximum (depends on water depth) Auto modes Fishing and cruising Zoom modes Marker, bottom, bottom lock, bottom lock/center Features Mark present or past echo as waypoint (961/962) Go directly to any past echo A-scope analyzes present or past echoes Navigation data shown at bottom of screen Demo mode for t
Table 4: 491 echo sounder features (Continued) Screen notations Echo data Seabed depth (various size digits) Frequency of each window Speed through water (if connected) Water temperature (if connected) Depth scale for each window Depth of depth marker Latitude/longitude of position marker and vessel Alarm status and auto/manual status Zoom mode Name of waypoint, and distance and bearing to waypoint Steering indicator Interfacing Connects Northstar 961/962 GPS Chart Navigator Northstar 957/958/6000i GPS Ch
Table 4: 491 echo sounder features (Continued) Manual controls Gain 0 to 75 db Clutter 0 to 9 Signal level 0 to 5 Noise limiter ON/OFF White level Any single color Other Screen color palette Depth marker Position marker Zoom in/out Shift Ranges 15, 30, 60, 120, 200, 400, 800, 1000, 2400 feet 5, 10, 20, 40, 80, 150, 300, 500, 800 meters Advance speed 1/8 to 2/1 Depth units Feet, meters, fathoms Installation calibrations Include speed, temperature, gain, and transducer type 491 Echo Sounde
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G Glossary A-scope COG clutter A horizontally magnified view of each echo, where the strength is shown by the width as well as the color of the line. Course-Over-Ground. The actual path of your vessel relative to the surface of the earth. Distracting echoes caused by turbulence, plankton, etc. Can be reduced by the clutter control. current The horizontal movement of water caused by tidal or other forces.
longitude Imaginary lines on the Earth's surface running North/South and expressed in degrees (0-180) east or west of the Prime Meridian (a line running from the North to South Pole, passing through Greenwich, England). meter A unit of measurement (length) equal to 39.37 inches, slightly more than a standard yard. nautical mile (nm) An international unit equal to 6,076.115 feet (1,852 meters) used officially in the U.S. since 1959. A nautical mile is about 800 feet more than a statute mile.
