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The Difference RADAR SART and AIS SART

As an important part of GMDSS, Search and Rescue Radar Transponder (SART) will be on standby when the ship is in distress, after being manually turned on, but it will not transmit distress signal at this time, when there is a search and rescue ship or aircraft passing within 5n mile, the 9GHz navigation radar inside my body will trigger me. When there is a search and rescue ship or airplane passing within 5n miles, the pulse signal from my 9GHz navigation radar will trigger me. My “power” (display) will be different depending on the distance.


The SART sweep generator sends out 12 equally spaced sawtooth signals, which are sensed by the navigation radar and shown on the display as 12 equally spaced dots radiating outward from the center. The first dot represents the distance between the SART and the SAR vessel, and the angle between the bow line and the line of the 12 dots is shown on the display as the bearing. When the target distance approaches within 1n mile, the bright spots gradually become concentric circles. The dots and concentric circles are internationally recognized SAR signals.


To display only SART signals on the radar screen, “radar receiver detuning” can be used to eliminate the common radar image generated by the same-frequency echo signals.SART signals cannot be eliminated because the SART response signal scans all frequencies in the 9 GHz band.

Comparison between RADAR-SART and AIS-SART

Ⅰ Different System Composition

AIS-SART and AIS equipment together to form a homing system, the working channel is AIS I and AIS 2, its working frequency is 161.975MHz and 162.025MHz, while RADAR-SART and 9GHz search and rescue radar together to form a homing system, the working frequency is 9200MHz-9500MHz, unless the search and rescue radar and AIS equipment are connected, otherwise, in the search and rescue radar, the SART response signal scans all the frequencies in the 9GHz band. Unless SAR radar and AIS equipment are connected, AIS-SART signal cannot be displayed on SAR radar; similarly, RADAR-SART signal cannot be displayed on AIS equipment.

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Ⅱ Different activation methods

After AIS-SART is activated, it directly enters into the activation state and transmits message 1 and message 14; after RADAR-SART is activated, it is only in the preparatory state, only the receiver is working, the transmitter is not working, and it is only activated and transmits the corresponding response signal after receiving the 9GHz radar pulse signal, which can effectively prolong the battery life.

This effectively extends the battery life.


Ⅲ Differences in the range of action

The antennas of AIS-SART and RADAR-SART are at the same height above the sea level, and the transmitter power is about 1 W. The farthest distance that can be searched is shown in the table below. It can be seen that AIS-SART can be searched farther than RADAR-SART.

Convention Requirements

Part 1

Requirements of Inspection Rules

A1 sea area: 1 for both passenger and cargo ships.

A1+A2 sea area or A1+A2+A3 sea area: passenger ships and cargo ships of 500 gross tons and above are equipped with 2 units, and cargo ships of less than 500 gross tons are equipped with 1 unit.

For manned non-motorized vessels equipped with life rafts, they should also be equipped with search-and-rescue positioning devices for life rafts in accordance with the sea area in which they are sailing.

Ships equipped with two search and rescue positioning devices should be equipped with one per side. The search and rescue locator device should be stored in a place where it can be quickly put into the life raft.

Part 2

SOLAS requirements

Every passenger ship and all cargo ships of 500 gross tons and above shall be equipped with at least one SAR locator transponder per side.

All cargo ships of 300 GT and above but less than 500 GT shall be equipped with at least one SAR locator transponder.

The SAR locator transponder shall comply with the applicable performance standards, which are not less stringent than those adopted by the Organization.

The search and rescue locator transponder shall be stowed in such a position that it can be quickly placed on all life rafts other than the life rafts required by regulation 31.1.4. One search and rescue locator transponder may also be placed on each life raft (other than a life raft required by clause 31.1.4).

At least two search and rescue locator transponders shall be provided, and a ship with a self-landing lifeboat shall place one search and rescue locator transponder in the self-landing lifeboat and another search and rescue locator device closest to the bridge to facilitate its use on board and transfer to another lifeboat.


SART is an important communication equipment for ships in distress. After the modification of the performance standard, AIS-SART is more conducive to the rapid and accurate localization of boats (rafts) in distress under adverse conditions at sea, which greatly shortens the time for rescue at sea and improves the chances of survival of people in distress.

Although many ships still use the traditional RADAR-SART system in ship search and rescue response, with the gradual increase and improvement of AIS signal base station, the superiority of AIS-SART system will be highlighted. It is believed that AIS-SART system will eventually replace RADRA-SRAT system and become the protagonist of ship search and rescue response.






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