The Importance of SART on Ships: A Guide to Search and Rescue Transponders

SART on ship: Search and Rescue Transponder, is a crucial piece of equipment on a ship since it serves as a signalman.

It’s an essential device in times of distress since it helps determine the location of the ship if it veers off course.

Because SARTs are constructed of waterproof materials, water cannot harm them.

SARTs can function for extended periods because they are primarily battery-operated.

Ships, lifeboats, and liferafts all use SARTs. They are the most helpful devices in an unforeseen disaster and are built to float on the water for an extended period if the vessel is submerged.

SARTs can send and receive radio signals thanks to their transmitter and receiver combo, which also allows for fast detection thanks to their brilliant color.

By responding to the search signal generated by an X-band radar, which normally operates at 9 GHz, SART equipment have played a crucial role in the rescue of multiple ships and boats. We refer to these signals as homing signals.

The response helps rescuers reach the vessels in time and is typically shown on radar screens as a series of dots on an X-band radar.

The Goal And Process Of A SART’s Operation

A SART broadcasts a sequence of response (homing) signals in response to a signal from a ship or aircraft radar. It functions in the 9 GHz (3 cm, or “X-band”) radar frequency band. The SART can be set to answer when questioned either manually or automatically (in certain situations). Instructions for using and activating SARTs are marked on the sides of each SART; however, the process differs depending on the type available.

These response signals, which are around 8 n miles out from the position of the SART along its line of bearing, will appear as a line of 12 dots (0.64 n miles apart) on the radar screen of the ship or aircraft. The survival boat can be located by the aircraft or rescue vessel thanks to this distinct radar signal that is simple to identify. Twelve more dots, spaced 0.64 n miles apart, are generated as the SART approaches (see Section 11.1.4).

Radar operating at 3 GHz, often known as 10 cm or “S-band,” will not trigger a SART.

The Operation and Interrogation Indication

The SART will indicate whether it is operating correctly visually and/or audibly upon activation. Additionally, it will let you know when radar signals from an aircraft or ship conducting a search are questioning it.

Distances between locations

Distances between locations
(Credit: MarineGyan)

When questioned within 8 n miles by a shipborne X-band radar with a 15 m scanner height, a SART should react. When a compatible X-band radar installed aboard an aircraft operating at a height of 3,000 feet and at a minimum distance of 30 n miles queries a SART, it should also react.

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Because height affects how far a SART will react to a radar signal, survivors should try to mount the SART as high as they can in a lifeboat or life raft by attaching it to an oar, for example. For this reason, mounting poles are incorporated into certain SART versions. The device’s features and the antenna’s vertical polar diagram will allow the SART to react to radars in situations with significant swell. In the horizontal plane, SART transmission is almost omnidirectional.

Location Inaccuracies

While a search radar is questioning it, the SART’s receiver is continuously scanning the radar band for radar signals. When an X-band radar within range interrogates (or triggers) the sweep, it alternates between being sluggish and quick. There can be a slight lag in the SART response when the SART receiver locks onto the searching radar signal since not all maritime radars in the 9 GHz radar band operate at the same frequency. There is a pause as the SART receiver moves from receive to broadcast mode and keeps sweeping once it has locked onto the seeking radar.

The initial dot of the SART answer displayed will be no more than 150 meters away from the actual location of the SART as the range closes to reveal the fast sweeps responses.

The first dot of the SART response displayed can be up to 0.64 n miles away from the true position of the SART when the range is such that only the slow sweep responses are visible (range roughly larger than 1 n mile).

 SART on ship: Overview of features, location, and operation

SART Overview of features, location, and operation

  • Because SART is composed of fiber-reinforced plastic, it is resistant to both extreme weather and prolonged exposure to sunlight.
  • It can float apart from the survival craft.
  • SART is installed on a mounting bracket on the bridge of a ship that is fastened to a bulkhead.
  • It creates a sequence of clips on the 3 cm/X Band radar that it is questioned by, and it operates in the 9GHz frequency range (9.2 to 9.5 GHz).
  • They might be permanently affixed to the survival craft or they can be moveable.
  • Since the SART is manually enabled, it only reacts when questioned.
  • The SART responds to radar interrogation when it is triggered in a distress situation by sending out a signal that causes 12 blips on the radar and, when the range between the two decreases, changes into concentric circles.
  • The PPI indicates that there will be 0.6 miles separating each blip.
  • Compared to a signal echo from, say, a radar reflector, this signal is much easier to detect.
  • Additionally, the SART alerts survivors when the radar is questioning them and gives an audible or visual signal that it is working properly.
  • When no radars are visible, an audible beep is heard every 12 seconds; when a radar is questioned, it sounds every 2 seconds.

Carriage Requirement

  • Passenger ship- at least 02
  • Cargo ship 500 GT and above- at least 02
  • Cargo ship 300 GT and above- at least 01
  • 1 on each survival craft

Battery Requirement

  • In standby condition, operational for 96 hours
  • In working condition, operational for 08 hours
  • Battery should be replaced every 2 to 5 years
  • Operable in temperature between -20 deg to 55 deg

SART Test Procedure

Self Test (General)

  • Switch SART to test mode
  • Hold SART given the radar antenna
  • Check that the visual indicator light operates
  • Check that the audible beeper operates
  • Observe the radar display and see if there are concentric circles on the PPI
  • Check the battery expiry date

Self Test (Typical)

  • Remove SART from the bracket
  • Insert the probe into the SART at 2-second intervals; the lamp flashes and the beeper sounds
  • Observe concentric circles on the X band radar

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In the event of a false activation, turn off the SART right away. Send out a DSC safety notice on channel 70 on the VHF. Send out a safety broadcast via RT on VHF Channel 16 to all stations, stating your ID, whereabouts, and your want to revoke the erroneous warning that was mistakenly sent out.


Using a typical Automatic Identification System class-A position report, the AIS-SART is a self-contained radio device that transmits updated location data to help find a survival craft or troubled vessel.

A built-in GNSS receiver (such as GPS) provides the AIS-SART with its position and time synchronization. A search and rescue locating device is included in one or more installations of the Global Maritime Distress Safety System (GMDSS). An AIS-SART (AIS Search and Rescue Transmitter) or a radar-SART (Search and Rescue Transponder) could be one of these devices.

SARTs are helpful in air and sea rescue operations when it comes to planes or ships that have become stuck. To cover a wide range, they are made to withstand the most extreme circumstances and remain mobile at high places, such as atop a pole.

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