Raymarine C140w - Page 102

Antennaheight
(meters)
Targetheight
(meters)
Maximumrange
(Nauticalmiles)
5
1012
Radarimagequality
Anumberoffactorscanaffectthequalityofaradarimage,including
echoes,seaclutter,andotherinterference.
Notallradarechoesareproducedbyvalidtargets.Spuriousechoes
maybecausedby:
•Sidelobes.
•Indirectechoes.
•Multipleechoes.
•Blindsectors.
•Sea,rain,orsnowclutter.
•Interference.
Throughobservation,practice,andexperience,youcangenerally
detecttheseconditionsveryquicklyandusetheradarcontrolsto
minimizethem.
SideLobes
Sidelobepatternsareproducedbysmallamountsofenergyfrom
thetransmittedpulsesthatareradiatedoutsidethenarrowmain
beam.Theeffectsofsidelobesaremostnoticeablewithtargetsat
shortranges(normallybelow3nm),andinparticularwithlarger
objects.Sidelobeechoesformeitherarcsontheradarscreen
similartorangerings,oraseriesofechoesformingabrokenarc.
True echo Side echoes
Main lobe
Antenna
Arc
Side
lobe
Side
lobe
D1638-4
IndirectEchoes
Thereareseveraltypesofindirectechoesorghostimages.These
sometimeshavetheappearanceoftrueechoes,butingeneralthey
areintermittentandpoorlydened.
False echo
Passing
ship
True echo
D1641-4
True echo
False echo
Mast
or funnel
102C-SeriesWidescreenuserreference