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REDUCING OR ELIMINATING INTERFERENCE
Uasically
tht?re
ait
Ihiee
types
uf
interference
wtlicfi
may
nlnder
radar
reception:
sea
dutter,
due
to
echoes
off
waves
(mentioned
earlier);
precipitation dutter and interference from other shipborne radars operating
nearhy
and
nn
the
same
freqnenoy
band.
This
radar
oan
eliminate
or
reduce these types of inlerference.
Precipitation Interference
The
vcrtical beamwidth
of the scanner is designed
to see surface
targets
oven when
the
ship is rolling.
Hovvever, this
design alao
has
its disadvan
tages: rain storms, snow, or hail are detected in the same manner as normal
targets.
Precipitation
dutter
is
easily
recognizable
by
its
wool-like
appearance on~screen (see Fig.29).
When this type of interference obscures
a
large area of the screen,
you may
use the
touchpad to eliminate or
reduce the interference.
The FTC (Fast Time Cunstaiit)
Circuit
worKs by splitting up these unwanted
echoes into a speckled pattern,
making recognition of solid targets easier.
Because its efl'ect upon the piclure is to weaken it, but because it breaks
up solid echoes. it also makes for betler definition.
For this reason, it
may
be switched
on
to clarify
the picture when navigating in confined waters.
However,
with
the Circuit activated
the receiver is less
sensitive,
weaker
echoes
may
be
missed.
The^fore,
deactivate
the
Circuit
when
no
interference exists.
Press the
[^] touchpad and you will see the indicator
"FTC" appears
at the upper-riglTt hånd
side of the display
screen.
The
Circuit is switched off by pressing the touchpad again.
(A) rain squall,
FTC "OFF"
(B) FTC Circuit "ON"
interference reduced
Fig.29
Precipitation Interference
Kadar Interference
Kadar interference
may
occur
when
in
the
vicinity
of another
shipborne
radar operating
in
the
same
frequency
band.
It usually
is
seen
on the
display screen as a large number of bright dots either scattered at random
or in the form of dotted lines extending from the center (or the edge) to
the
edge
(or
the
center)
of
the
display
screen.
Fig.30
illustrates
int(?rferf?neG in
the
form
nf niirved
qpokes.
[nterference effeots are
easily
distinguished
from normal echoes because thcy
do not appear in the same
place on successive rotations of the scanner.
33
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