Simrad RA771UA, Инструкция по эксплуатации

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3 . 4 False Echoes
Echoes from targets which do not actually exist in
that direction may appear on the
CRT.
to as "false"
or
"indirect" echoes. The causes and
phenomena
of
such false echoes are listed below.
Virtual
or
Ghost Echoes
on the screen as two echoes in two separate
directions. One is a real echo and the other is a
virtual, or ghost, echo caused by secondary reflection of
emitted pulses by funnels, masts, etc. The former
appears at the correct range and bearing, while the ghost
appears at a range the funnel or the
mast (Fig. 3 - 4 ) .
They are referred
A
large target at close range may, at times, appear
Direct Reflection P a t h
Reflection
i
Direction
of
Ghost
Echo
Heading Marker
screen
Fig. 3 - 4 Virtual or Ghost Echoes
When a target is on the funnel or
mast
side, a
series of ghost echoes may appear in the vicinity of a
real echo.
as mentioned previously. When the intensities of
reflected waves change,
a
number of ghosts can be
detected (Fig.
3-5).
But, they are arranged
with respect to a real echo and vanish
when the ship's heading changes.
The principle of this phenomenon is the same
3 - 4