DATELINE: 2nd April 2001

PLB LOCATION
Divers who wear emergency personal locator beacons (PLBs) are more likely than ever to be locatable not only by lifeboat or rescue helicopter but by the charter boats from which they are diving.
So says Mike Snelling, Chairman of the National Federation of Charter Skippers.
"Up to now, skippers have only had the option of a British-made homing device that costs about £2000," he says. "But now we've sourced an American-made homer which will cost us about £400, including shipping. As a result I see a lot more charter boat skippers planning to fit them."
PLBs work on the 121.5 MHz frequency and can be picked up by satellites, although signal transfer to a receiving land station can take several hours. They are designed for close-to location by helicopters, lifeboats and any other vessels equipped with a homer, providing a relatively local working range - 5-10 miles for helicopter location, less for boats.
Manufacturer Sea Marshall makes the waterproof PLB8 with flashing light for divers. It quotes a 0.75 nautical mile detection range for a diver wearing a unit around the neck; but in recent trials of the US-made homer, Mike Snelling located a PLB8 at 2.5 miles when its aerial was mounted on a stick, one metre above the sea.
"The PLB is excellent for locating a diver who is nearby but invisible either at night or in fog," says Snelling. "Fog is often associated with calm conditions, in which a PLB will work at its best. In such an emergency, a homer fitted to the diving charter boat will be invaluable."
To further aid location in fog, Snelling advises divers to carry an inflatable radar reflector and a good whistle.
By contrast to PLBs, EPIRBs (Emergency Position Indicating Radio Beacons) work on 406 MHz and are picked up by satellites only. Their signals reach land stations in about 20 minutes. EPIRBS are often carried aboard vessels but, according to Sea Marshall, are not yet available as waterproof units suitable for wear by divers.

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