Furuno 1942 MARK-2 manual False Echoes, Multiple Echoes, Side-lobe Echoes

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4. FALSE ECHOES

Occasionally false echoes appear on the screen at positions where there is no target. In some cases the effects can be reduced or eliminated. The operator should familiarize himself or herself with the appearance and effects of these false echoes, so as not to confuse them with echoes from legitimate contacts.

4.1 Multiple Echoes

Multiple echoes occur when a short range, strong echo is received from a ship, bridge,

4.2 Side-lobe Echoes

Every time the scanner rotates, some radia- tion escapes on each side of the beam— called “side-lobes.” If a target exists where it can be detected by the side-lobes as well as the main-lobe, the side-lobe echoes may be represented on both sides of the true echo at the same range, as shown in Figure 4-2. Side-lobes show usually only at short ranges and from strong targets. They can be reduced through careful reduction of the sensitivity or proper adjustment of the A/C SEA.

or breakwater. A second, a third or more ech- oes may be observed on the display at double, triple or other multiples of the actual range of the target as shown in Figure 4-1.

Main-lobe

True echo

Multiple reflection echoes can be reduced and often removed by decreasing the sensi- tivity or properly adjusting the A/C SEA.

True echo

Own ship Multiple

echo

Figure 4-1 Multiple echoes

Side-lobe

Sprious target

Antenna

Figure 4-2 Side-lobe echoes

4-1

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Contents Marine Radar Page Radiator Distance to Stay away from transmitting scannerWorst case 1.70 m Nil Worst case 1.20 mDo not disassemble or modify the equipment Do not open the equipmentUse the proper fuse Keep heater away from equipmentCompliance with R&TTE Directive 1999/5/EC Foreword FeaturesTable of Contents Menu KEY Menu TreeTable of Contents by INDICATION, Marker Display Unit System ConfigurationScanner Unit Principle of Operation What is Radar?How Radar Determines Range How Radar Determines BearingHow radar works Control Description Basic OperationTurning the Radar On/Off Economy modeStand-by TransmittingAdjusting Receiver Sensitivity Adjusting Picture BrillianceAdjusting the A/C SEA Control Reducing sea clutter Selecting the RangeAdjusting the A/C SEA control Adjusting the A/C Rain Control Reducing rain clutterTip for adjusting the A/C SEA Adjusting A/C RainErasing the Heading Marker, North Marker Measuring the RangeMeasuring range by range rings Measuring range by cursorMeasuring the Bearing Using the Offset EBLMeasuring range and bearing between two targets Cancelling offcentered pictureOffcentering the Picture Zoom Cancelling zoomMenu Operation Selecting the Presentation ModeBasic Menu Operation Head upMagnifying Long Range Echoes echo stretch Echo TrailSuppressing Radar Interference Cancelling echo trailFixed time trail Continuous trailSetting a guard zone Guard AlarmSelecting Pulsewidth Selection of guard zone typeCancelling the guard zone and guard alarm Silencing the audible alarmWatchman How watchman worksDisplaying Navigation Data Cancelling watchmanTurning on watchman To turn navigation data on or offOther Menu Description Other Menu DescriptionFunction Controls Adjusting Brilliance of MarkersSuppressing Noise Outputting Target PositionSide-lobe Echoes False EchoesMultiple Echoes Blind and Shadow Sectors Indirect EchoesShowing Sart marks on the radar display Sart Search and Rescue TransponderSummary to detect Sart response General remarks on receiving SartThis page is intentionally left blank Replacing the Fuse Maintenance & TroubleshootingPreventive Maintenance But Then TroubleshootingSelf Test This page is intentionally left blank Display accuracy is affected by the following Operation of ARP-10 OptionGeneral Principal specificationsARP-10 Menu Operation Keys used for auto plotterARP Menu Deactivating the auto plotterAcquiring Targets Setting auto acquisition areaManual acquisition Automatic acquisitionTerminating Tracking of Targets Displaying Target DataIndividual targets All targetsTrue or relative vector vector mode Mode and Length of VectorsCPA/TCPA alarm Past Position DisplayLost target alarm This page is intentionally left blank Specifications of Marine Radar Display Unit Dimensions and Mass IN-1 IndexPage Page Page 00080835401