Furuno FR-8251, FR-8111 manual Locating a Ship or Survival Craft in Distress by Sart

2.6Locating 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 Screen B: When SART is close

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

Position of

SART

9500 MHz

9200 MHz

Radar antenna beamwidt h

SART mark length

Sweep time

7.5 µs

100 µs

Radar receiver bandwidth

1Radar 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.

2SART range errors

There are inherent delays in the SART responses as the SART has a trigger delay and may also

Figure 2-8 Appearance of

SART marks on the radar display

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.

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