Testing Magnets Installed on EPIRB Brackets. Prepared by Robert G. Garrott CGD Five CFVS Coordinator July 3, 2007. Background Information 1.
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Prepared by Robert G. Garrott
CGD Five CFVS Coordinator
July 3, 2007
In 2006, CGD Seven CFVS Coordinator Larry Yarborough and SEC Charleston Lead Examiner Greg Johnson lead a detailed analysis of EPIRB false alerts. They found air and surface sorties triggered by false alerts cost the Coast Guard millions in fuel, personnel and maintenance expenses each year, and that there were two main causes for these false alerts.
Modern 406 MHz EPIRBs are designed to automatically activate if removed from their mounting bracket and in contact with water. To reduce false alerts, a magnet mounted in the bracket opens a magnetic reed switch in the EPIRB circuitry. The two most common problems causing false alerts are mounting the EPIRB in the bracket incorrectly, and for the magnet to be missing or out of position.
Because they can be placed in the bracket backwards (with the line spool facing out), ACR Satellite EPIRBs are more susceptible to incorrect mounting than other EPIRBs.
Careful attention to Owner’s Manuals and mounting diagrams can prevent false alerts due to incorrect mounting in the bracket.
It takes just a few seconds to verify the magnet is properly installed in the bracket. The test device – an inexpensive magnetic compass. The bracket magnet will cause the compass needle to swing and point at the bracket instead of pointing at the magnetic north pole. The following slides show this occurring for several of the most frequently encountered marine EPIRBs.
Note: The magnet is positioned under the EPIRB and is not visible until the EPIRB is removed.