Radar-SART (9 GHz)
A 9 GHz radar-SART does not transmit a message; it produces a distinctive line of response dots on any nearby X-band radar screen once triggered, guiding a rescuer visually toward survivors, which is a different mechanism entirely from an AIS-SART's plotted position on an electronic chart.
Read more — Radar-SART (9 GHz) explained ▾
What sets a 9 GHz radar-SART apart
A search and rescue transponder in this category works by responding to X-band (9 GHz) radar pulses, not by transmitting its own independent signal like an AIS-SART or an EPIRB. When it detects an incoming radar pulse from a searching ship or aircraft, it replies with a swept response that appears on the searcher's radar screen as a line of about twelve dots stretching outward from the SART's position, growing shorter as the range closes. This gives a visual, radar-based homing aid with no need for the SART to know its own position, unlike an AIS-SART which broadcasts GPS coordinates directly.
Main components
Transponder unit
A compact, buoyant, watertight unit combining the X-band receiver and transmitter, designed to float upright when deployed and mounted on a telescopic pole to maximise its effective range.
Battery
A dedicated primary battery, separate from any radio or EPIRB battery, rated to power the unit continuously for a minimum stand-by and active operating period set by the equipment standard.
Activation switch and indicator
A manual switch, with a test/standby/active status indicator, usually including an audible or visual signal confirming it is transmitting once activated.
Mounting bracket
A bracket in the survival craft or on deck that allows quick removal, since the SART's effectiveness depends heavily on being raised well clear of the water and wave clutter.
Selection and sizing
| Parameter | Relevance |
|---|---|
| Battery endurance | Standard requires a set standby period plus continuous active transmission, typically 96 hours standby and 8 hours active |
| Mounting height achievable | Detection range depends heavily on how far above sea level the SART can be raised |
| Buoyancy and float orientation | Must self-right if it ends up in the water rather than in a survival craft |
| Quantity carried | Set by SOLAS carriage requirements per survival craft arrangement, not a single ship-wide figure |
Regulations and class
SOLAS Chapter III sets the carriage requirement for radar-SART or AIS-SART units according to ship type and survival craft arrangement, with cargo ships typically required to carry at least one and passenger ships more, distributed so that units are available regardless of which side is used to abandon ship. The performance standard requires detection by a 9 GHz radar out to a stated minimum range under standard test conditions, and the unit must survive drop testing consistent with survival craft stowage. Class and flag state surveys check battery expiry dates and that the annual servicing required by the manufacturer's approval has been carried out, since a SART with an expired battery gives no warning that it will fail when needed.
Typical faults
- Expired battery - the most common finding at survey; a SART past its battery expiry date may still power on briefly during a self-test but fail to sustain a rescue-length transmission.
- Bracket corrosion - a seized quick-release bracket delays getting the SART clear of the survival craft in an actual emergency.
- Water ingress through a damaged seal - a cracked case or worn gasket, often from rough handling during drills, lets water reach the electronics.
- Confusion with AIS-SART carriage credit - crews sometimes assume one type substitutes freely for the other in the carriage requirement, when the two work by different mechanisms and the required mix is set by the flag state.
What to look for in a supplier
- Current type approval matching the 9 GHz radar-SART performance standard, distinct from AIS-SART approval
- Battery and hydrostatic/mechanical service intervals clearly stated, with service available in the ship's trading area
- Bracket and pole design proven for the specific survival craft or deck stowage arrangement fitted
- Drop and immersion test certification appropriate to the stowage location
Check the battery expiry date at every lifeboat and liferaft inspection, not just at the annual survey - it is the single most common reason a SART is later found to be unserviceable, and it is caught immediately by a five-second look at the label.