EPIRB (406 MHz emergency beacon)

Safety beacons

An EPIRB is your boat's satellite distress beacon. Once switched on, it sends a coded 406 MHz alert through the international Cospas-Sarsat satellites to rescue authorities, giving the beacon's ID and, on GPS models, your position. It keeps transmitting for at least 48 hours.

How it works

Each 406 MHz beacon carries a unique 15-character hex ID. Satellites relay its alert to the US Mission Control Center, which matches the ID with NOAA's registration database and passes your details to the Coast Guard. A weak 121.5 MHz signal lets rescuers home in once close. Category I EPIRBs sit in a float-free bracket with a hydrostatic release that frees them if the boat sinks; Category II are released by hand. Satellites stopped processing old 121.5/243 MHz beacons in February 2009.

Using it

• Mount a Category I EPIRB outside the cabin, where it can float free if the boat sinks and nothing blocks it. Keep a Category II where anyone aboard can grab it fast.
• Switch it on only in grave and imminent danger, when you have no other way to get help. Once on, leave it on until rescued.
• If you abandon ship, take the EPIRB, tie its lanyard to the life raft (never to the boat or bracket) and let it float upright with a clear view of the sky, not inside the raft's canopy.
• Some newer beacons have a Return Link light that confirms the alert reached the system; these have been legal in the US since June 1, 2022. It doesn't mean a rescue has been launched.
• Give your emergency contacts your plans. When an alert comes in, the Coast Guard phones the numbers in your registration first to check whether you're really out.
• If it goes off by accident, switch it off as the manual says and call the Coast Guard at 1-855-406-8724 with the hex ID so they can stand down. NAVCEN says the Coast Guard doesn't refer accidental alerts from properly registered beacons to the FCC unless there was a hoax or gross negligence.

Looking after it

• Run the self-test as the maker directs; one maker says monthly. Self-tests, and especially GPS self-tests, use battery life, so stay within the number the manual allows.
• Replace the battery by the date on the label, with the maker's specified battery, normally through an approved service centre. An accidental activation also means a new battery.
• The hydrostatic release unit has its own expiry date, usually two years from installation (check the label), and is simply replaced when due. Don't paint it or power-wash it; replace it if it's dropped.
• Check the bracket holds the beacon securely. Beacons knocked out of their brackets are a common cause of false alerts.
• Clean the beacon only with a damp cloth (one maker also allows rubbing alcohol), and don't carry it by the antenna.
• Re-register every two years, and whenever your phone, address, emergency contacts or boat change.
• When a beacon is retired, remove and recycle the battery and tell NOAA; a beacon thrown in the trash can go off and trigger a search.

Troubleshooting

Buying a boat that has one

• Make sure it's a 406 MHz beacon. A 121.5 MHz-only EPIRB is illegal to use in the US and no satellite hears it.
• Read the battery and hydrostatic-release expiry dates, and budget for service if either is near or past.
• Get the seller to mark it sold with NOAA, then register it in your name before you go out.
• Check the hex ID on the beacon matches the paperwork and that it's coded for the US.
• New sales of EPIRB models that don't meet the current RTCM 11000 standard ended in January 2020 (47 CFR 80.1061). Older ones may still be used as certified, but ask the maker whether batteries and service are still available.

General guidance for recreational boaters, researched from the sources listed and written in our own words. Your equipment manuals, local knowledge, the Navigation Rules and a qualified instructor come first.