Locating A Ship Or Survival Craft In Distress By Sart - Furuno FR-8051 Operator's Manual

2.6 Locating a Ship or Survival
Craft in Distress by SART
SART background
The SART is required on vessels of 300 GT and
above by the 1974 SOLAS Convention as
amended in 1988 (GMDSS). Performance stan-
dard is specified in IMO Resolution A.697 (17).
SART activating conditions
The SART should operate correctly when inter-
rogated at a distance of up to at least five miles
by a navigational radar complying with resolu-
tions A.477(XII) and A.422(VII) and IEC 936,
with an antenna height of 15 meters. (It should
also operate correctly when interrogated at a dis-
tance of up to 30 miles by an airborne radar with
at least 10 kW peak output power at a height of
3,000 feet.)
How SART works
Upon receiving a radar signal from a rescue party,
the SART automatically transmits a series of
twelve frequency sweeps at a frequency between
9200 (+0/-60 MHz) and 9500 MHz (-0/+60
MHz). The radar will represent twelve SART
marks during one sweep cycle on the screen. See
the Figure 2-8.
Screen A: When SART is distant
Radar antenna
beamwidt h
Position of
SART
SART mark length
9500 MHz
9200 MHz
Sweep time
7.5 µs
Figure 2-8 Appearance of
SART marks on the radar display
2 – 4
Screen B: When SART is close
Radar receiver
bandwidth
100 µs
The length of a SART mark depends on the
radar's receiver bandwidth and sensitivity. For the
bandwidth of 12 MHz, the length is 45 meters
approximately and for the bandwidth of 3 MHz
(usually on the 6 mile range or larger), 12 meters
approximately.
How to show SART marks on the
display
Detune the radar receiver manually by turning
the TUNE control out of best tuning condition.
This erases or weakens all normal radar echoes;
but, the SART marks are not erased because the
SART response signal scans over all frequencies
in the 9 GHz band. When the radar approaches
the SART in operation, the SART marks will en-
large to large arcs, blurring a large part of the
screen. Reduce the sensitivity and adjust the sea
clutter control of the radar.
Summary to detect SART responses
1) Use range scale of 6 or 12 nm as the spacing
between the SART responses is about 0.6 nm
(1125 m) to distinguish the SART
2) Turn off the automatic clutter suppression.
3) Turn off the Interference Rejector.
4) Turn off the Echo Average.
General remarks On receiving SART
1 1 1 1 1 Radar range scale
When looking for a SART, it is preferable to use
a range scale between 6 and 12 nautical miles.
This is because the spacing between the SART
responses is about 0.6 nautical miles (1125 m)
and it is necessary to see a number of responses
to distinguish the SART from other responses.
2 2 2 2 2 SART range errors
There are inherent delays in the SART responses
as the SART has a trigger delay and may also
have to sweep through the whole radar band be-
fore reaching the frequency of the search radar.
At medium ranges of about 6 nautical miles the
range delay may be between about 150 meters
and 0.6 nautical mile beyond the SART position.