Raymarine RL80C Plus Spécifications Page 73

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Chapter 3: Standard Radar Operations 3-5
Identifying False Echo
Returns
Identifying False Echo Returns
Notallechoesaredirectreturnsto the radarantenna. Occasionally signals
appearat positionswherethere is no actualtarget.Theseare calledfalse
echoes,and may be caused by side lobes,ghost images, indirectechoes or
multipleechoes.
Thissectionbrieflydescribesthe echopatternsthatcan be producedbyfalse
echoesandthelikelycause.Itshouldbenotedthattheradaroperator,through
observation, practice,and experience,cangenerally detecttheseconditions
veryquickly.Theseeffectscanusuallybe minimizedusing theradar controls.
Side Lobes
Asmall part of theRF energy fromeach transmittedpulseis radiatedoutside
thesinglenarrowbeam.Thisproducessidelobepatterns, shownin
Figure 3-3.
Sidelobes havenoeffect on distant or smallsurfaceobjects.However, the
echofroma largeobjectatshortrangemayproduceanarcon theradarscreen
similartoarangeringor a seriesof echoesformingabrokenarc.Side-lobe
echoesnormallyoccur at rangesbelow3nm, and can be reducedby adjusting
the SEA control.
Figure 3-3: Side Lobes
True echo Side echoes
Main lobe
Antenna
Arc
Side lobe Side lobe
D1638-2
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