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AIDS TO NAVIGATION
V'arious aids have been
deveioped
to oid
tlie
navigstor in jdontifyinc
radar
targets.
RADAR 13EACONS
Radar
beacons
are
transmitters
operating
in
the
marine
frequency
band
which
produce distinctive indications on the radar displays of ships within
range
of
these
bRaeons-
There
are
two
classea
of
beacons:
racan
and
ramark.
Racon
A
racon
is
an
omnidirectional
transmitter which
emits
a
distinctive
signal
when triggered by
ihe pulse from a ship's radar.
Both range and bearing
to
the
target can be extracted from
the
signal.
Because
the
beacon
'
S
Signal
travels at the same time as the echo arriving the ship's range to the target
can be determined.
Since the signal will be received only when the scanner
is
pointing directly at
the beacon,
bearing is
shown as well as the range
and the vessel s position is thus determined.
The range and bearing of the
racon signal is measured in exactly the same manner as a normal target pip-
The racon signal appears on the .display as either a radial line originating at
a point juGt beyond
the
radar
beacon
or
as
a Morse code Signal dispJayed
radially from just beyond the beacon.
See Fig.49.
Note that with the FT C
or IR Circuit switched on, the racon marker line may partially disappear.
(A) Coded Racon Signal
(B) Racon Signal
Fig.49 Racon Signal Appearance
Ramark
A similar type of
beacon is known as a ramark.
It tranemits continuously on
a
frequency
constantly varying
so as
to sweep
through
the
en Ure
radar
band.
The
ramark
signal appears as a radial line from
the
center of the
CRT.
Tha radial line
may
be a eontinuous narrow line, a series of dashes
a
sei'ica
of
Uots,
or
a
series
of
dots and
dashes.
Fig.50
illustrates the
appearance
of
a
ramark
signal,
as
a
dotted
line,
and
as
a dashed
line.
Although
the
ramark
flash
shows
only
the
bearing
to
the beacon,
if
the
ramark is mounted on the ooast and this can be also seen on the screen, a
fix can be obtained from the ramark.
(A) as a dotted line
(13) as a dashed line
Fig.50 Ramark Signal Appearance
48
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