Furuno 1942, 1932, 1832 What is Radar?, How Radar Determines Range, How Radar Determines Bearing

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1. PRINCIPLE OF OPERATION

1.1 What is Radar?

The term “RADAR” is an acronym meaning RAdio Detection And Ranging. Although the basic principles of radar were developed dur- ing World War II, echoes as an aid to naviga- tion is not a new development.

1.2How Ships Determined Position Before Radar

Before the invention of radar, when running in fog near a rugged shoreline, ships would sound a short blast on their whistles, fire a shot, or strike a bell. The time between the origination of the sound and the returning of the echo indi- cated how far the ship was from the cliffs or the shore. The direction from which the echo was heard indicated the relative bearing of the shore.

1.3How Radar Determines Range

Radar determines the distance to the target by calculating the time difference between the transmission of a radar signal and the reception of the reflected echo. It is a known fact that ra- dar waves travel at a nearly constant speed of 162,000 nautical miles per second. Therefore the time required for a transmitted signal to travel to the target and return as an echo to the source is a measure of the distance to the tar- get. Note that the echo makes a complete round trip, but only half the time of travel is needed to determine the one-way distance to the target. This radar automatically takes this into account in making the range calculation.

1.4How Radar Determines Bearing

The bearing to a target found by the radar is determined by the direction in which the radar scanner antenna is pointing when it emits an electronic pulse and then receives a returning echo. Each time the scanner rotates pulses are transmitted in the full 360 degree circle, each pulse at a slightly different bearing from the previous one. Therefore, if one knows the di- rection in which the signal is sent out, one knows the direction from which the echo must return.

1.5Radar Wave Speed and Antenna Rotation Speed

Note that the speed of the radar waves out to the target and back again as echoes is extremely fast compared to the speed of rotation of the antenna. By the time radar echoes have returned to the scanner, the amount of scanner rotation after initial transmission of the radar pulse is extremely small.

1.6 The Radar Display

The range and bearing of a target is displayed on what is called a Plan Position Indicator (PPI). This display is essentially a polar diagram, with the transmitting ship’s position at the center. Images of target echoes are received and dis- played at their relative bearings, and at their distance from the PPI center.

With a continuous display of the images of tar- gets, the motion of the transmitting ship is also displayed.

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Contents Page 00080788713 Important Notices Radio Frequency Radiation Hazard Compliance with R&TTE Directive 1999/5/EC Foreword Table of Contents Model 1832 Specifications Vii SpecificationsViii OptionEquipment List Installation Materials Configuration of Model 1832/1932/1942 Xii Radar Display What is Radar?How Radar Determines Range How Radar Determines BearingHow radar works Control Description Basic Operation125 NM Display Indication and MarkersStand-by Economy modeTurning the Radar On/Off TransmittingSelecting the Range Adjusting Picture BrillianceAdjusting Receiver Sensitivity Adjusting the A/C SEA Control reducing sea clutterAdjusting A/C Rain Adjusting the A/C Rain Control reducing rain clutterAdjusting the A/C SEA control Tip for adjusting the A/C SEABy cursor Erasing the Heading Line, North MarkMeasuring the Range By range ringPredicting collision course Using the Offset EBLMeasuring the Bearing By EBLCancelling shifted picture Shifting off centering the PictureMeasuring range and bearing between two targets Zoom Cancelling zoomSelecting the Presentation Mode Basic Menu OperationPress the Menu key to close the menu Magnifying Long Range Echoes echo stretch Echo TrailSelect OFF deactivate at Echo Trail on the menu Suppressing Radar InterferenceGuard Alarm Selecting PulsewidthMentally create the guard zone you want to set Guard WatchmanGo into the Others menu, and set 15. Watchman for off Displaying Navigation DataFollowing summarizes the Other Menu Other Menu DescriptionOutputting Target Position Adjusting Brilliance of MarkersFunction Keys Suppressing NoiseMultiple Echoes Side-lobe EchoesIndirect Echoes Indirect echoes Blind and Shadow SectorsMaintenance & Troubleshooting Troubleshooting Self Test Mounting Model Where the temperature is more than 70 CUnpacking the antenna unit Siting, handling considerationsMounting platform Wiring and final preparationMounting Model 1932 Connections Fasten the cable gland assemblyWaveguide Groove Final preparationMounting Navigation aid, video sounder con- nectionYou will need an Nmea cable Mounting considerationsHeading signal can be connected to the HDG connector Heading Sensor ConnectionInput/Output Data List Preparation Tick boxAdjusting tune/video When adjustment is completed, the mes- sages disappearsEntering antenna height Adjusting sweep timing Adjustment range0.000~3.239nm Adjusting MBS Adjustment 0.00~0.25Magnetron heater voltage Setting a blanking areaThis page is intentionally left blank Menu Tree ARP-10 Option Limits, Visual alarm against lost Targets violating CPA/TCPATargets AP-4 Auto acquisition area is predefined between One minute after acquisition Vector still un- reliableAP-6 AP-7 ARP-10 Not usedMake sure the follows on Self Test menu Page Hatai Page Marine Radar Marine Radar