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-3.4-
3.3 SART (Search and Rescue Transponder)
A Search and Rescue Transponder (SART) is generally carried on the SOLAS Convention ships
under the GMDSS scheme. It serves as a homing device for the rescue party to reach the survival
craft in distress. It is triggered by any X-Band (3 cm) radar within a range of approximately 5 nm
(IMO Resolution A.802 (19)). Each radar pulse received causes it to transmit a response which is
swept repetitively across the complete radar frequency band. When interrogated, it first sweeps
rapidly (0.4 µs) through the band before beginning a relatively slow sweep (7.5 µs) through the
band back to the starting frequency. This process is repeated for a total of twelve complete cycles.
At some point in each sweep, the SART frequency will match that of the interrogating radar and be
within the pass band of the radar receiver. When the SART is within about 1 nm, the radar display
may show 12 responses equally spaced by 0.64 nautical miles.
9500 MHz
9200 MHz
Radar antenna
beamwidth
Screen A: When SART
is distant
Screen B: When SART
is close
Lines of 12 dots
are displayed in
concentric arcs.
Echo of SART
Position of
SART
Own ship's
position
Own ship's
position
SART mark
length
Radar receiver
bandwidth
Sweep time
7.5 µs
95 µs
Sweep start
High speed sweep signal
Low speed sweep signal
24 NM
1.5 NM
Position of
SART
Echo of
SART
Summary to detect SART response
No particular facilities are required to detect the SART responses; however, the following
precautions are necessary.
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. To avoid a chance of regarding SART signals as noise, do the following:
- Turn off the automatic clutter suppression.
- Turn off the Interference Rejector.
- Turn off the signal processor such as Echo Average.
The FR-1500 Mark-3 series radars have a macro feature for easy detection of SART.
Press [F1], 0], [ENTER/SELECT]. The following setting is factory provided.
IR (Interference Rejector): OFF ECHO AVG: OFF
A/C AUTO: OFF N REJ: OFF
Signal processor: OFF ES: OFF
Range: 12 nm