Table of Contents
Advertisement
APPLICATION
As
an
airi
to
navigation,
radar
can
ba
a very
vaJuablo
tool-
No other
navigation aid can give you the ability to spot vessels coming at you in ttie
fog,
or tell you the location of the inlet to the harbor in the pitch black of
night.
To help you understand better what your radar can and cannot do
tor
you
this
section
covers
the
characteristics
and
limitations
of
radar,
picture interpretation, position fixing with radar and aids to navigation.
FACTORS AFFECTING MINIMUM RANGE
Targets
disappearing
from
the
screen
when
at
close
ranges
can
be
dangerous.
For this
reason,
detection of targets at short ranges is very
important.
Minimum
range
is
determined
primartly
by
transmitter
pulselength.
The • shorter
the
transmission
time,
the
sooner
the
return
echoes
can
bc
rcccived
and
their
distance
measured.
This
radar
automatically determines the pulselength for both short and long ranges,
for
optimal detection of targets at short as well as long range-
Sea Return
Sea
dutter
echoes
received
from
waves
may
hamper
detection of
targets
beyond the minimum range set by the pulselength and recovery time.
CKe-
covery
time
is
the
time
required
for
the
receiver
to
recover
to
half
sensitivity after the end of a transmitted pulse,
so it can receive a return
eehQ.)
Proper
adjnatment of the A/C SKA
oontrol
iray alleviate some
of the
problem.
Ver tical Beamwjdth
The ability to see targets very close to the boat is decreased if the antenna
is mounted too high off the water,
since the bottom of the vertical beam of
the
scanner cuts
off nearby
targets,
Fjg.37 illustratcs
the
cffectc
of
a
scanner mounted too high off the water.
Fig.37 Effeets of a Scanner Mounted too High off the V/ater
FACTORS AFFECTING MAXIMUM RANGE
It is nearly impossible to State that a radar has a maximum range. The max-
imum
range a radar will "see" is dependent on many factors,
not just the
39
Advertisement
Table of Contents
