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Resumen del manual
Not all radar echoes are produced by valid targets. Spurious echoes may be caused by: • Side lobes. • Indirect echoes. • Multiple echoes. • Blind sectors. • Sea, rain, or snow clutter. • Interference. Through observation, practice, and experience, you can generally detect these conditions very quickly and use the radar controls to minimize them. Side Lobes Side lobe patterns are produced by small amounts of energy from the transmitted pulses that are radiated outside the narrow main beam. The effects of side lobes are most noticeable with targets at short ranges (normally below 3 nm), and in particular with larger objects. Side lobe echoes form either arcs on the radar screen similar to range rings, or a series of echoes forming a broken arc. True echoSide echoesMain lobeAntennaArcSidelobeSidelobeD1638-4 Indirect Echoes There are several types of indirect echoes or ghost images. These sometimes have the appearance of true echoes, but in general they are intermittent and poorly defined. False echo PassingshipTrue echo D1641-4True echo False echo Mastor funnel C-Series Widescreen user reference Multiple Echoes Multipleechoesarenotverycommonbutcanoccurifthereisalarge target with a wide vertical surface at a comparatively short range. The transmitted signal will be reflected back and forth between the target and your own ship, resulting in multiple echoes, displayed beyond the range of the true target echo, but on the same bearing. D1642-3True echoMultiple echoes Blind Sectors Obstructions such as funnels and masts near the radar antenna may obstruct the radar beam and cause radar shadows or ‘blind sectors’. If the obstruction is relatively narrow, there will be a reduction of the beam intensity, though not necessarily a complete cut-off. However, for wider obstructions there may be a total loss of signalin the shadow area. There may alsobe multiple echoes which extend behind the obstruction. Blind sector effects can normally be minimizedbycarefulselectionofthescannersitepriortoinstallation. Sea Clutter Radar returns from waves around the vessel can clutter the centre of the radar picture, making it difficult to detect real targets. Such ‘sea clutter’ usually appears as multiple echoes on the display at short range scales, and the echoes are not repetitive or consistent in position. With high winds and extreme conditions, echoes from sea clutter may cause dense background clutter in the shape of an almost solid disc. D3968-4 Rain or Snow Clutter The radar can see echoes from rain or snow. Returns from storm areas and rain squalls consist of countless small echoes that continuously change size, intensity and position. These returns sometimes appear as large hazy areas, depending on the intensity of the rainfall or snow in the storm cell. D3967-4 Using radar 103 Interference 9.4 Radar display overview When two or more radar-equipped vessels are operating within With your radar scanner connected and the radar in transmit mode, range of each other mutual radar interference can occur. This the radar picture provides a map-like representation of the area usually appears as a spiral of small dots from the display centre This in which the radar is operating. type of interference is most noticeable at long ranges. D6601-2 3nmHead-UpRelative MotionRings .nmVRM/EBL...GAIN...PRESENTATION...TARGETTRACKING... ENHANCEECHOES...D6803-3OrientationData barSurfacevesselWaypointShip'sheadingmarkerRadarstatusiconRangeringLand- massBoat'spositionRangeMotion modeRange ring spacing Typically, your boat’s position is at the centre of the display, and its dead ahead bearing is indicated by a vertical heading line, known as the Ship’s Heading Marker (SHM). On-screen targets may be large, small, bright or faint, dependent on the size of the object, its orientation and surface. If using an analog radar scanner, strongest target returns are displayed in yellow with weaker returns in two shades of blue. If using a digital radar scanner, stronger target returns show as different colors from a range of 256 colors, providing better clarity. Be aware that the size of a target on screen is dependent on many factors and may not necessarily be proportional to its physical size. Nearby objects may appear to be the same size as a distant larger objects. C-Series Widescreen user reference With experience, the approximate size of different objects can be determined by the relative size and brightness of the echoes. You should bear in mind that the size of each on-screen target is affected by: • The physical size of the reflecting object. • The material from which the object is made. Metallic surfaces reflect signals better than non-metallic. • Vertical objects such as cliffs reflect signals better than sloping objects such as sandbanks. • Highcoastlinesandmountainouscoastalregionscanbeobserved at longer radar ranges. Therefore, the first sight of land may be a mountain several miles inland from the coastline. Although the coastline may be much nearer, i...
Otros modelos de este manual:Sounders - C140w (3.17 mb)