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EPIRBs & SARTS
Nowadays, an EPIRB is one of the easiest way to get help virtually anywhere in the world's oceans.
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There are various different types of EPIRB. Firstly there are two different frequencies, 121.5Mhz and 406Mhz.
121.5 Mhz
This frequency is used by the more basic EPIRBs and as a secondary frequency for more complex models. It is only really useful near land or
within range of other shipping, as it is not generally detectable globally by satellites. It is ideal for use in personal locator EPIRBs but for Blue Water situations it is useful when
used with direction finding equipment. Personal beacons are now even available in multi function watches.
406 Mhz
This is the principle EPIRB frequency, detectable globally by satellite. They are available in manual or automatic formats and with either
standard or GPS location. Each is programmed with a unique code which is centrally registered to the vessel. It is therefore not possible to move an EPIRB from one vessel to another
without first notifying the authorities. It is not advisable to purchase second hand EPIRBS for this and various other reasons.
Manual EPIRBS (Cat 2) are normally positioned close at hand and rely on someone manually
activating them. They are less prone to accidental activation, but are of less use on a single handed vessel. It is just one more thing to do in an emergency situation.
Automatic EPIRBS (Cat 1) are usually equipped with some kind of hydrostatic release.
Once this device is under a certain level of water pressure, ie the vessel is sinking, it releases the EPIRB to float free. The EPIRB then has a water sensor to activate the internal
transmitter. It is vital that the EPIRB is fitted in a position where it is least likely to be fouled by rigging and other equipment. It is usually also possible to activate an
automatic EPIRB manually. This might be necessary in a man overboard situation.
The standard location process of and EPIRB can take several hours. It involves satellites and associated centralised equipment slowly
building up a location profile for the EPIRB until finally the approximate location is determined. 121.5 Mhz can then be used by search vessels/aircraft to pinpoint the EPIRB’s exact
position.
GPS is now commonly used to speed up the location process. This can take two formats. An internal GPS
that allows the EPIRB to constantly transmit its exact position. This obviously has its advantages, but the cost and the fact that there will be an acquisition delay might be a
consideration. With modern GPS engines, this is not normally a problem.
A cheaper alternative is to use the ships GPS to update the EPIRB’s position memory until the time of deployment. When it is deployed the
EPIRB will transmit the time and position of the vessel at the time of activation. There are obvious drawbacks to this system but it is important to remember that the standard location
system will continue to give a reasonably accurate position update as long as the EPIRB remains operational. It also is important to make sure that the connection between GPS and EPRIB
remains permanently in place and operational.
To See our range of EPIRBS, visit our
electronics pages
- particularly McMurdo,
GME, and
Jotron.
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