Search and Rescue Radar Transponder (SART)
Search and Rescue Radar Transponder known as the SART are portable devices capable of transmitting locating signals which indicate the location of mobile unit in distress on the ships Radar screen. The SART signal is picked up by the rescue units X-Band, 9 Ghz (3cm) Navigational RADAR.
The SART signal appears on the RADAR display of a series of equally spaced dots outward on a line of bearing. There are about 12 NM of blips. These turn into arcs as the ship nears the signal on their x-band radar (The reason it is call X-Band is from WW2 when it was very secret) (or the 3 cm/9 Ghz). Generally, Search and rescue radar transponders are a means of providing locating signals in the GMDSS.
The activation of SART is simple. The SART are typically carried into survival craft and activated manually. SART are required to manually activated and deactivated.
When the SART is activated from a ship in distress or survival craft, SART provides both a audible and visual indication to alert survivors that a RADAR has triggered the SART. I guess this would give the survivors some hope that a rescue is at hand. This might be the time for survivors to attract the attention of rescue units via alerting devices.
IMO has given us some specifications for the Batteries used to power the SARTs. The SART will have sufficient battery capacity to last for 96 hours in the standby mode followed by 8 hours in transponder mode. A SART antenna is typically horizontally polarized and omni directional. This is because the 3 cm radar has an antenna that is horizontally polarized, and by the way radars, and SARTS, are the only antennas that are horizontally polarized.
The Communications Range of the SART relies on direct wave propagation, their communications range is determined primarily by transmitter power output, receiver sensitivity and antenna height above ground. It seems that the SART operators have little control over the first two but can optimize its effective range by maintaining the SART as high as possible. There is an extension mast attached to some SARTS to increase the height, providing a little more range. The height of the SART should be at least 1 meter above sea level to be effective.
The Performance Standards are set by IMO for SARTs call for a range of at least 5 miles when a SART is located 1 meter above sea level. This assumes the search vessel has a radar antenna 15 meters high. When the radar is aboard an aircraft, such as a US Coast Guard Aircraft flying a search patter at an altitude of 3000 feet should be able to detect SART at ranges up to 30 miles.
Most SART currently on market are not designed to float free or be place in the water. However, SARTs are required to sustain a drop from 20 meters into water with out damage. And have a Water tight integrity to a depth of 10 meters for 5 minutes.
On the ship the operation of the Marine X-Band Radar used to Detect the SART at its maximum range will be enhanced if the controls of the radar are properly set.
When looking for a SART the 6 or 12 N Mile range should be used. the bandwidth of the radar should be less than 5 MHz so a medium bandwidth should be selected. Check your Radar operating manual for proper radar parameters and bandwidth selection. Medium and wide bandwidths are normally with long pulse radar transmission.
In increasing the visibility of the SART in clutter condition, the radar should be de-tuned to reduce the clutter. Some radars with AFC (automatic frequency control) may not permit any manual de-tuning of the equipment. The normal gain setting for long range detection should be used, with some light background noise visible. The Anti-Sea Clutter control should be set to minimum and the Anti-Rain Clutter should be set to be used normally as to break up areas of the rain. The SART response, being a series of dots, will not be affected by the action of the anti-clutter rain circuitry.
