Operation Manual

D16 3 8 -5
1
2
2
3
4
5
6
6
ItemDescription
1Mainlobe
2
Sidelobes
3Antenna
4Arc
5
Trueecho
6
Sideechoes
IndirectEchoes
Thereareseveraltypesofindirectechoesorghostimages.These
sometimeshavetheappearanceoftrueechoes,butingeneralthey
areintermittentandpoorlydened.
D16 4 1 -5
1
3
2
4
5
6
ItemDescription
1Falseecho
2Trueecho
3Passingship
4
Mastorfunnel
5
Trueecho
6Falseecho
MultipleEchoes
Multipleechoesarenotverycommonbutcanoccurifthereisalarge
targetwithawideverticalsurfaceatacomparativelyshortrange.
Thetransmittedsignalwillbereectedbackandforthbetweenthe
targetandyourownship,resultinginmultipleechoes,displayed
beyondtherangeofthetruetargetecho,butonthesamebearing.
D16 4 2 -4
1
2
ItemDescription
1Trueecho
2Multipleechoes
RainorSnowClutter
Theradarcanseeechoesfromrainorsnow.Returnsfromstorm
areasandrainsquallsconsistofcountlesssmallechoesthat
continuouslychangesize,intensityandposition.Thesereturns
sometimesappearaslargehazyareas,dependingontheintensity
oftherainfallorsnowinthestormcell.Theimagesinthetable
belowshowhowtheRaincontrolcanclearupthisclutter:
Rain
clutter
off
Rain
clutter
on
BlindSectors
Obstructionssuchasfunnelsandmastsneartheradarantenna
mayobstructtheradarbeamandcauseradarshadowsor‘blind
sectors’.Iftheobstructionisrelativelynarrow,therewillbea
reductionofthebeamintensity,thoughnotnecessarilyacomplete
cut-off.However,forwiderobstructionstheremaybeatotallossof
signalintheshadowarea.Theremayalsobemultipleechoeswhich
extendbehindtheobstruction.Blindsectoreffectscannormallybe
minimizedbycarefulselectionofthescannersitepriortoinstallation.
SeaClutter
Radarreturnsfromwavesaroundthevesselcanclutterthecentre
oftheradarpicture,makingitdifculttodetectrealtargets.Such
‘seaclutter’usuallyappearsasmultipleechoesonthedisplayat
shortrangescales,andtheechoesarenotrepetitiveorconsistent
inposition.Withhighwindsandextremeconditions,echoesfrom
seacluttermaycausedensebackgroundclutterintheshapeof
analmostsoliddisc.
D3968-5
Interference
Whentwoormoreradar-equippedvesselsareoperatingwithin
rangeofeachothermutualradarinterferencecanoccur.This
usuallyappearsasaspiralofsmalldotsfromthedisplaycentreThis
typeofinterferenceismostnoticeableatlongranges.
Usingradar
129