Survival Craft Radio Equipment

So, you have abandoned your sinking GMDSS vessel, and you find yourself in a lifeboat or liferaft.

What now ?

Well the GMDSS doesn't stop yet - there are specific GMDSS radio systems developed for operation from survival craft.

These systems are designed to alert rescuers to your plight and guide them to your location.

Search And Rescue (Radar) Transponders (SARTs)

SART is a self contained, portable and buoyant Radar Transponder (receiver and transmitter).

SARTs operate in the 9 GHz marine radar band, and when interrogated by a searching ship's radar, respond with a signal which is displayed as a series of dots on a radar screen.

SART

Although SARTs are primarily designed to be used in lifeboats or liferafts, they can be deployed on board a ship, or even in the water.

SARTs are powered by integral batteries which are designed to provide up to 96 hours of operation.

Operation

When activated, a SART responds to a searching radar interrogation by generating a swept frequency signal which is displayed on a radar screen as a line of 12 dots extending outward from the SARTs position along its line of bearing.

The spacing between each dot is 0.6 nautical miles.

As the searching vessel approaches the SART, the radar display will change to wide arcs. These may eventually change to complete circles as the SART becomes continually triggered by the searching ship's radar.

Although not an actual SART response, this radar picture gives an impression of how a SART signal would be displayed

Some slight position error will also be caused by the SART switching from receive to transmit mode.

SARTs will also provide a visual and audible indication to users when interrogated by a searching radar.

Range

The range achievable from a SART is directly proportional to its height above the water.

A SART mounted at 1m (ie: in a liferaft) should be able to be detected at 5 nautical miles by a ship's radar mounted at 15m.

The same SART should be able to be detected at 30 nautical miles by an aircraft flying at 8000 feet.

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GMDSS carriage requirements

GMDSS vessels from 300 to 500 GRT are required to carry 1 SART, and vessels over 500 GRT are required to carry 2.

Portable VHF transceivers

These units are designed to allow communications between searching vessels and survivors in liferafts. They operate on the VHF marine band in voice mode. DSC capability is not fitted.

Performance standards

The IMO performance standard requires that the equipment:

• provide operation on VHF channel 16 (the radiotelephone distress and calling channel) and one other channel

• be capable of operation by unskilled personnel

• be capable of operation by personnel wearing gloves

• be capable of single handed operation, except for channel changing

• withstand drops on to a hard surface from a height of 1 metre

• be watertight to a depth of 1 metre for at least 5 minutes, and maintain watertightness when subjected to a thermal shock of 45 degrees Celsius.

• not be unduly effected by seawater or oil

• have no sharp projections which could damage survival craft

• be of small size and weight

• be capable of operating in the ambient noise level likely to be encountered on board survival craft

• have provisions for attachment to the clothing of the user

• be either a highly visible yellow/orange colour or marked with a surrounding yellow/orange marking strip

• be resistant to deterioration by prolonged exposure to sunlight

Typical GMDSS VHF portable transceivers

GMDSS carriage requirements

GMDSS vessels from 300 to 500 GRT are required to carry 2 VHF portables, and vessels over 500 GRT are required to carry 3.

Let's take good look at DSC - what it is - and how it works...