How Does An EPIRB Work


It’s a nightmare, you’re in the middle of the ocean, your ship sinks so fast you can’t even send distress,

MV Derbyshire is a bulk carrier that sank in 1980. She was almost 300 meters long. It’s believed she sank within seconds rather than minutes.

Consider another scenario, you’ve more time, but you can’t send distress you give your last known position, but that was taken six minutes ago, in that time your ship could have travelled a couple of miles, in both scenarios, one piece of equipment could give rescuers vital information it’s the EPIRB.

An EPIRB is an Emergency Position Indicating Radio Beacon,

it became standard equipment on vessels nowadays.

We’ll take a look at standard maritime EPIRB that would be carried on a ship.

Activating and How to Use EPIRB :

The main body of the EPIRB is waterproof and enables it to float, comprises a switch for manual activation, and sensors on the bottom for automatic activation, they also got an antenna that needs a clear view of the sky. 

EPIRBs should be mounted in float-free containers and surrounded by protective housings with a hydrostatic release that will cut the EPIRB free when submerged.

In theory, the EPIRB will float to the surface and activate, in case of the ship sank, that’s why those two sensors kick in, all they do is detect a conductive medium like seawater, and a small amount of current passes between the contacts tells the EPIRB has been submerged and needs to activate.

if you have time to carry the unit and take it into your survival boat then you can activate it manually using the switch, either way, you now have an EPIRB trying to tell the outside world that help is needed. 

To do that it needs a clear view of the sky it needs to get a direct line of contact with any of the satellites in the cosmos, these are a network of satellites orbiting the earth designed to pick up these distress signals. 

Every EPIRB will transmit its own identity to the satellite system, besides that modern ones also transmit their GPS location so they can be found easily. Of course, even if you have an older model that is not GPS enabled the satellite can still find you.

What it does is measure the Doppler shift in the transmission’s frequency to work out your position, the frequency shift is enough to give a location 

If the signal has a higher frequency than expected the satellite is moving towards the transmitter and if it has a lower frequency the satellite is moving away.

In the case of GPS enabled, beacons bypass all of that and just tell the satellite where they are, so now a satellite knows the identity and position of a distress beacon that’s been activated and it’s enough to get help mobilized.

After Signal Transmitted:

Satellites send the distress down to monitoring stations, and it is then passed on to regional control centres these centers have access to a database of all EPIRBs that are registered, this gives them information about the vessel that the EPIRBs registered, so they can plan the rescue appropriately.

For example, if the centre detects activation of an EPIRB from a yacht they will know the color of the hull, the size of the yacht, and all vital information when an aircraft is sent to search.

Likewise, if the centre detects activation of an EPIRB from a commercial vessel, they’ll attempt contact using radio or satellite communications, they may then contact the vessels owners who can provide passenger and crew or details of the cargo that’s carried, again all vital information when planning a rescue. 

The Rescue Coordination Center can then commit a search, be a passing ships or aircraft or dedicated search and rescue services, they will have an accurate position and details of who needs rescuing, all of which increase the chances of a successful rescue.

Points to Remember:

EPIRB needs to be mounted in a clear space so that it can float free, if you take it into a lifeboat make sure you activate it manually and follow the instructions on the unit itself, then leave the device floating in the sea either way make sure it has a clear line of sight to the sky, you don’t want anything to cross the path of the signal from the unit to the satellite, and finally make sure it’s registered giving rescue authorities the details of your vessel.

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