Raymarine c97 - Page 163

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2
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ItemDescription
1Mainlobe
2
Sidelobes
3Antenna
4Arc
5
Trueecho
6
Sideechoes
IndirectEchoes
Thereareseveraltypesofindirectechoesorghostimages.
Thesesometimeshavetheappearanceoftrueechoes,butin
generaltheyareintermittentandpoorlydened.
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ItemDescription
1Falseecho
2Trueecho
3Passingship
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Mastorfunnel
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Trueecho
6Falseecho
MultipleEchoes
Multipleechoesarenotverycommonbutcanoccurifthereis
alargetargetwithawideverticalsurfaceatacomparatively
shortrange.Thetransmittedsignalwillbereectedbackand
forthbetweenthetargetandyourownship,resultinginmultiple
echoes,displayedbeyondtherangeofthetruetargetecho,
butonthesamebearing.
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ItemDescription
1Trueecho
2Multipleechoes
BlindSectors
Obstructionssuchasfunnelsandmastsneartheradarantenna
mayobstructtheradarbeamandcauseradarshadowsor
‘blindsectors’.Iftheobstructionisrelativelynarrow,therewill
beareductionofthebeamintensity,thoughnotnecessarilya
completecut-off.However,forwiderobstructionstheremay
beatotallossofsignalintheshadowarea.Theremayalso
bemultipleechoeswhichextendbehindtheobstruction.Blind
sectoreffectscannormallybeminimizedbycarefulselectionof
thescannersitepriortoinstallation.
RainorSnowClutter
Theradarcanseeechoesfromrainorsnow.Returnsfrom
stormareasandrainsquallsconsistofcountlesssmallechoes
thatcontinuouslychangesize,intensityandposition.These
returnssometimesappearaslargehazyareas,dependingon
theintensityoftherainfallorsnowinthestormcell.Theimages
inthetablebelowshowhowtheRaincontrolcanclearupthis
clutter:
Rain
clutteroff
Rain
clutteron
SeaClutter
Radarreturnsfromwavesaroundthevesselcanclutterthe
centreoftheradarpicture,makingitdifculttodetectreal
targets.Such‘seaclutter’usuallyappearsasmultipleechoes
onthedisplayatshortrangescales,andtheechoesare
notrepetitiveorconsistentinposition.Withhighwindsand
extremeconditions,echoesfromseacluttermaycausedense
backgroundclutterintheshapeofanalmostsoliddisc.Sea
cluttercanbesuppressedusingtheseacluttersettings.The
imagesinthetablebelowshowhowtheseacluttersettingscan
clearupsomeofthisclutter:
Radarapplication
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