A PLB (Personal Locator Beacon) is a personal emergency beacon that transmits a 406 MHz distress signal to the COSPAS-SARSAT satellite system. Unlike an EPIRB — which identifies the vessel — a PLB identifies an individual. It is small, light and is worn or kept in a lifejacket pocket.

How does a PLB differ from an EPIRB?

An EPIRB is the vessel's device: it activates if the boat sinks and alerts rescuers to the shipwreck. A PLB is personal: each crew member carries their own. If someone falls overboard and drifts away from the boat, the vessel's EPIRB cannot locate that individual — only their PLB can. They are complementary, not interchangeable.

Does a PLB activate automatically in water?

Most marine PLBs require manual activation: you deploy the antenna and press the activation button. Some models have automatic water-activation, but the majority are manual. This means the crew member must be conscious to activate it. For high-risk areas like Patagonia, some sailors integrate the PLB directly into their harness or lifejacket.

How long does a PLB battery last?

A PLB battery must guarantee at least 24 hours of continuous transmission and has a standby life of 5 years. Like an EPIRB, the battery must be replaced even if the device has never been used. The expiry date is printed on the unit.

Is a PLB required in Chile?

A PLB is not universally mandatory by regulation, but many nautical insurance companies require one for navigation in remote areas. For the southern channels and Patagonia, I strongly recommend that every crew member carries one. It is the cheapest life insurance a sailor can have.

PLB Personal Locator Beacon: Sailor's Guide

In most maritime emergencies, the boat and the crew stay together. But there's one critical exception: man overboard. If someone falls over the side at night, in rough seas, or in the southern channels where visibility is limited, the chances of recovering them without a personal locator device are slim. The PLB exists for exactly that scenario.

What a PLB is and how it works

PLB stands for Personal Locator Beacon. It's an emergency device that transmits a distress signal on 406 MHz to the COSPAS-SARSAT satellite system — the same system used by an EPIRB. The key difference is size and purpose: a PLB is personal, portable, and worn on the body.

Once activated, it transmits a signal with a unique identification code registered to the wearer. If the unit has built-in GPS — as all modern models do — it also transmits an exact position. Satellites detect the signal and relay it to ground stations, which alert the relevant rescue centre with the position and identity of the person in the water.

Response time: With the COSPAS-SARSAT system's low-orbit (LEO) satellites, detection takes minutes. With the geostationary (GEO) satellites covering Chile, detection is near-instant if the PLB has GPS. Without GPS, the system calculates position via the Doppler effect, which can take longer and is less precise.

PLB vs EPIRB: the difference that saves lives

This is the point that causes the most confusion. Many sailors assume that if they have an EPIRB on board, they're covered. They are — but only for the scenario of the vessel itself being lost. If someone falls overboard and separates from the boat, the EPIRB does not transmit that person's position — it transmits the vessel's position, which may be miles away by the time help arrives.

In the southern channels of Chile, where water temperature is 6-10°C and survival time without an immersion suit is 30 to 90 minutes, recovering someone in the water without an exact location is extraordinarily difficult. A PLB solves that problem directly.

"I recommend one PLB per crew member on any voyage outside the bay. It's the cheapest life insurance a sailor can buy."

How to activate a PLB

Activation varies by model, but the general procedure is: deploy the antenna (usually by twisting and extending it) and hold the activation button until the unit starts flashing. A PLB makes no audible sound while transmitting, but the flashing light confirms it's working.

Important: Most PLBs are manually activated. If the person is unconscious when they fall in the water, the PLB will not activate on its own unless it's a model with automatic immersion activation (these cost more but exist). For crews with mixed experience levels, automatic-activation models are worth the extra investment.

Marine PLB vs aviation and hiking PLBs

PLBs exist for different environments: marine, aviation and land. Marine PLBs are built to work submerged to 10 metres (IPX8 rated), have positive buoyancy, and can be activated with gloves on or wet hands. Aviation and hiking models lack these features and should not be used in a marine environment.

Always look for a PLB with ITU certification for maritime use, and confirm it operates on 406 MHz (some older models use frequencies the COSPAS-SARSAT system no longer actively monitors).

Registering and maintaining your PLB in Chile

Like an EPIRB, a PLB must be registered with the Maritime Authority so the rescue system can identify the wearer when it activates. In Chile, registration is done through the Armada de Chile at your nearest Harbour Master's office, or online through the Directemar system. You'll need the unit's 15-digit HEX code and your personal details.

Register the PLB under your name with up-to-date contact details
Replace the battery every 5 years even if it's never been used
Check the status indicator periodically
Update the registration if you regularly change vessels
Carry the PLB on your lifejacket or somewhere easily accessible — not in a drawer

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Rodrigo Troncoso Peirano

Merchant Marine Captain with 30 years of experience in industrial fishing, offshore operations, and the fjords of Patagonia.

PLB: Personal Locator Beacon — What It Is and When to Use It