Raymarine e7 - Page 138

Thetablebelowshowstypicalmaximumradarrangesforvarious
radarantennaheightsandtargetheights.Rememberthatalthough
theradarhorizonisgreaterthantheopticalhorizon,theradar
canonlydetecttargetsifalargeenoughtargetisabovetheradar
horizon.
Antennaheight
(meters)
Targetheight
(meters)
Maximumrange
(Nauticalmiles)
33
7.7
31010.9
5
38.8
5
1012
Radarimagequality
Anumberoffactorscanaffectthequalityofaradarimage,including
echoes,seaclutter,andotherinterference.
Notallradarechoesareproducedbyvalidtargets.Spuriousor
missingechoesmaybecausedby:
•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.
D16 38 -5
1
2
2
3
4
5
6
6
ItemDescription
1Mainlobe
2
Sidelobes
3Antenna
4Arc
5
Trueecho
6
Sideechoes
138e7/e7D—Userreference