Furuno 1830 - By Two Bearings

factors such as dislortion from beamwidth and pulselength malte idenlification
of specific features difficult. However, the following may serve as an aid to
Identification.
1) High, steep, rocky and barren landroasses provide good reflecting
surfaces.
2) Low, vegetation covered lands laake poor radar targets.
3) Submerged objects do not produce echoes.
4) Mud flåts, marshes, sandspits, and smooth, clear beaches make poor
targets because they have almost no area that can reflect energy back to the
radar.
5) Smooth water surfaces such as lagoons and inland lakes appear as blank
areas on the displaysmooth water surfaces return no energy.
6) Although you might expect an object as large as a lighthouse to be a
good radar target, in actuality the return echo is weak since the conical
snape diffuses most of the radiated energy.
SHIP TARGETS
A bright, steady, dearly defined image appearing on the display is in all
likelihood the target pip of a Steel ship. There are several dues which can
aid you in Identification of a ship. Check your navigational position to
overrule the possibility of land. Land and precipitation echoes are much
more massive in appearance, whereas the target pips of ships are relatively
small. The rate of movement can eliminate the possibility that the pip is an
airoraft.
A target pip may brighten and become dim due to changes in aspect, etc.
In most cases however a pip will fade from the display only when the range
becomes too great.
ECHO SIZE
As the radar beam rotates. the painting of the pip on the display begins as
soon as the leading edge of the radar beam strikes the target, and continues
until the trailing edge of the beam is rotated bevond the target. Thus, a
target cannot appear less wide than the beamwidth. As the beam widens
with distance from the scanner, so ailso will the widths of targets vary on
the display. Fig.39 illustrates the relationship between beamwidth and the
appearance of a target pip«
Short Range
Fig.39 Beamwidth vs. Target Appearance
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