What is a PLB or Personal Locator Beacon?

Personal Locator Beacons which are usually just referred to as PLBs are a fairly new addition the safety tool box which everyone who spends time outdoors, especially those who do risky activities away from civilization, should carry.

If you end up in an emergency situation out in the wilderness a PLB in your pocket or backpack could be your only hope of rescue.

What is a PLB and how does it work?

Simply put, Personal Locator Beacons send an emergency signal through a worldwide satellite system to the appropriate Rescue Control Center (RCC). These RCCs will then dispatch Search and Rescue (SAR) Teams to assist you with your emergency situation. PLBs should only be used in an actual emergency situation as rescue workers will come looking for you when you activate your beacon.

Never turn your PLB on just to test it, this will cause an actual distress message to flow through the SAR System. There are proper procedures outlined in your beacon’s instructions which if followed properly will allow you to test the PLB without giving off a false alarm.

PLBs were once large and bulky devices, but as technology has improved manufacturers have been able to reduce the size of their products. Your average PLB is now as small as the average flip style cell phone, they will easily fit into your backpack or pants pocket.

Who should carry a Personal Locator Beacon?

Anyone who enjoys activities that are slightly dangerous or which place them well off the beaten path should definitely carry a PLB.

Here are some examples of who should carry a Personal Locator Beacon:

  • Hikers
  • Campers
  • Hunters
  • Horse Riders
  •  ATV Riders
  • Snow Machine Riders
  • Skiers and Snowboarders
  • Climbers
  • Kayakers
  • Jet Ski Riders
  • Boaters
  • Fishermen
  • Ice Fishers
  • Those who often travel in areas without cell coverage

As you can see from the list, anyone who is out by themselves or with a small group away from other people should carry one, especially if they know cell coverage is spotty or unavailable where they are going.

How much is your life worth?

Over the last few years PBLs have not only become smaller, but they’ve become cheaper and filled with more bells and whistles.

You can get reliable PLB from online stores like Amazon.com for as little as $275. A small price to pay to know that rescue forces will be headed you way if you need them.

How will they find you?

OK, so you’ve fallen and you can’t get up, to use the line from the TV commercial, you’ve had an accident out in the wilderness, here is how a PLB can help you.

Perhaps you were hiking in the Colorado wilderness by yourself, far from any other person, when you slipped and fell. Your leg got caught, twisted, and broken severely under a rock. You are miles from anyone else, you are stuck and there is no way you can get yourself out and no one will be passing by to find you.

In an older time you’d be out of luck, you’d die right there where you lay. But you have a technological marvel packed away in your backpack, your PLB. You pull it out, open it up, and turn it on. Within seconds the Search and Rescue Satellite system will pick up the Personal Locator Beacon’s signal and alert the authorities that someone needs help.

Depending on the type of PLB you’ve purchased, either the PLB will send your GPS location to the system, or the satellite system will determine your location on its own.

In either case after you bought it you should have registered your Personal Locator Beacon, in the United States this registration data will be transmitted along with the PLB activation information to the U. S. Air Force Rescue Coordination Center (AFRCC).

Rescue is on the way

The AFRCC will attempt to immediately contact you or those you’ve listed as contacts on your PLB Registration via phone to determine if you are actually in a distress situation. They make these calls because most beacon activations are false alarms and they need to determine if your emergency signal requires that someone respond. If they find out that you are or could be in an emergency situation or they can’t contact anyone they will get SAR forces headed to the location of your Personal Locator Beacon’s signal as fast as possible.

Be Prepared

Scenarios just like this one play out all the time, so make sure ahead of time that if you were to find yourself in a bad situation that you would have the right tools in order to bring about a good ending.

Buy yourself a PLB!


More Information

In other areas of this site you find much more information on how PLBs work, how the Search and Rescue Satellite System works, How to properly operate your Personal Locator Beacon, How to test your PLB, What is the best type of PLB to buy and most importantly our Personal Locator Beacon Review area, where you’ll be able to get our honest opinion of the various PLBs available on the market and where you can get them at a reasonable price.

Our goal is to be your best resource for information on Personal Locator Beacons! Writers for this site have worked in the United States Search and Rescue community for many years and have extensive knowledge of how the COSPAS-SARSAT system and America’s SAR System works. Rest assured we won’t steer you wrong. We fell that a PLB should be carried by everyone who engages in risky pastimes and those who spend time well away from others in areas of limited cell coverage.

This site is also committed to reducing the very large amount of false activations which take up a huge amount of our nation’s Search and Rescue professional’s time. PLBs are not toys and should be used and tested properly. It is every owners responsibility to learn about their beacon so as to prevent themselves from setting off a false SARSAT alarm.


This site recommends that you buy a PLB with GPS capability!

The COSPAS-SARSAT Satellite System

This page started out real dry and technical, but I’ve totally reworked it to make it more assessable and easier to read. This section will give you the background necessary to understand the recommendations which come later in the e-book on how to increase your odds of being saved from a distress situation.

The greatest aid to both searchers and those needing to be rescued is the Cospas-Sarsat system. This is a system of satellites orbiting the Earth combined with ground stations which are designed to provide distress alerting and location data to assist search and rescue (SAR) operations. This is accomplished by receivers on the satellites which detect and locate the signals of distress beacons operating on a frequency of 406 Megahertz (MHz). The position of the distress and other related information is forwarded to the appropriate Rescue Coordination Centers (RCCs) through the Cospas-Sarsat Mission Control Center (MCC) network.

The basic Cospas-Sarsat concept is illustrated in this figure. The System is composed of:


1. Distress radio beacons (ELTs for aviation use, EPIRBs for maritime use, and PLBs for personal use) which transmit signals during distress situations.
2. Instruments on board satellites in geostationary and low earth orbits which detect the signals transmitted by distress radio beacons.
3. Ground receiving stations, referred to as Local Users Terminals (LUTs), which receive and process the satellite downlink signal to generate distress alerts.
4. Mission Control Centers (MCCs), which receive alerts, produced by LUTs and forward them to Rescue Coordination Centers (RCCs), Search and Rescue Points Of Contacts (SPOCs) or other MCCs.

The Cospas-Sarsat system is currently comprised of two types of satellites, Low Earth Orbit (LEOSAR) and High Earth Orbit (GEOSAR). Low Earth Orbit satellites are placed close to the Earth, this coupled with the speed they need to circle the earth in order to stay at a constant altitude, causes them to rapidly fly over the terrain below. High Earth Orbit satellites because they are so much higher in altitude move at a speed in relation to the ground below which causes them to remain stationary over one spot on the Earth.

LEOSAR and GEOSAR Satellites

Low Earth Orbit Satellites orbit the Earth in near-polar orbits. They provide complete, yet non-continuous coverage of the Earth. The non-continuous aspect of the coverage occurs because the polar orbiting satellites can only view a portion of the earth at any given time.  Consequently the System cannot produce distress alerts until the satellite is in a position where it can “see” the distress beacon.  However, the satellite’s onboard 406 MHz processor includes a memory module, the satellite is able to store distress beacon information and rebroadcast it when the satellite comes within view of a ground station, thereby providing global coverage. A single satellite, circling the earth around the poles, eventually views the entire surface of the Earth.

Low Earth Orbit Satellites calculate the location of distress beacons using Doppler processing techniques.  Doppler processing is based upon the principle that the frequency of the distress beacon, as “heard” by the satellite instrument, is affected by the relative velocity of the satellite with respect to the beacon.  By monitoring the change of the beacon frequency of the received beacon signal and knowing the exact position of the satellite enables the calculation of the beacon location.

Each satellite makes a complete orbit of the earth around the poles in about 100 minutes, traveling at a velocity of 7 km per second. The satellite views a “swath” of the earth of approximately 6000 km wide as it circles the globe, giving an instantaneous “field of view” about the size of a continent. When viewed from the earth, the satellite crosses the sky in about 15 minutes, depending on the maximum elevation angle of the particular pass.

A LEOSAR Satellite Over-Europe

A Low Earth Orbit Satellite passing over Europe

High Earth Orbit Satellites carried on board various geostationary satellites. Because a high earth orbit satellite remains stationary relative to the Earth it has a continuous view of the terrain below enabling immediate alerts upon distress beacon activation. Unfortunately because the satellite does not move in relation to the terrain below there is no Doppler effect on the received frequency, and Doppler radiolocation positioning techniques cannot be used to locate distress beacons. Position information must either be acquired from the beacon though an internal or an external navigation receiver (GPS) and encoded in the message sent by the beacon, or derived, with possible delays, from the low Earth orbit satellite system.

There is one significant advantage of buying a beacon with a GPS receiver.  These emergency beacons determine their location using a GPS receiver that is either integrated into the beacon (called a location protocol beacon) or fed by an external GPS receiver. This accurate location information (generally around a football field in size for positional accuracy) is then encoded into the 406 MHz signal that is transmitted by the beacon.  The satellite then receives that signal with the location and forwards the location.  This information can often be derived in a matter of minutes!  Since every second counts in reaching the scene of a distress this means that there is an increased chance of survival.

GEOSAR Satellite Coverage (Footprint)

High Earth Orbit Satellites are “parked” over the indicated positions and have a continuous view of their respective color coded line of sight areas.

The important points to take away from this are:

Low Earth Orbiting Satellites can provide position calculation on distress beacons which do not provide their GPS location, but a satellite has to pass over to hear the beacon. Remember Low Earth Orbit Satellite coverage is not continuous so delays in picking up a beacon are possible and it could take several satellites passing over before a accurate position is determined.

High Earth Orbit Satellites provide instantaneous detection of distress beacons in their field of view but cannot determine location on its own. The distress beacon must send an encoded GPS location to be forwarded to rescuers.

The LEOSAR and GEOSAR satellites are complimentary systems. Each type of satellite is able to help fill the others blind spots. While low Earth orbit satellites pass over areas every hour and a half or so the high Earth orbits are always watching. When distress beacons like PLBs are in an area where a satellite in high Earth orbit can’t see due to the angle or obstructions a low orbit one will pass over in time.


This site recommends that you buy a PLB with GPS capability!