A personal locator beacon (PLB) is a vital, last-resort SOS emergency rescue device. PLBs are smaller land-based cousins of Emergency Position Indicating Radio Beacons (EPIRBs) used by boaters.
PLBs use a 406 Mhz radio wave frequency distress signal to pinpoint your location and identification data to several satellites.
This information is forwarded to local search and rescue coordinators, making the chance of finding an adventurer vastly greater.
When a PLB has been activated, help or assistance can come from rescue authorities, colleagues, friends, or nearby monitoring assets, depending on the type of PLB and the receiving equipment used.
📡 How PLBs Work
PLBs were explicitly designed by search and rescue operators to locate you in an emergency, much like how an EPIRB works.
This sets them apart from other equipment like antenna satellite phones, VHF radios, and cellular phones.
Modern PLBs have 5 major components to achieve their goal.
The first is a powerful, 5-watt radio transmitter that transmits information at 406 MHz through the atmosphere.
The second component is the identification data stored on the PLB. This data is a 15-character unique serial number.
When you register your PLB, that serial number is linked to your personal details. This allows rescue services to know whom they are looking for and be able to contact your next of kin for more info on your trip.
The third component is a flashing light beacon, which increases your chances of being spotted during a night search.
The fourth component is the battery which must be able to keep transmitting for at least 24 hours after activating the PLB.
The final major component is a GPS receiver. Although not all PLBs have a GPS receiver, most modern ones have opted to include one due to its incredible improvements.
The GPS received will relay your GPS position to the 406 MHz transmitter. So, your location data will also be sent to rescue coordination centers.
The Cospas-Sarsat Satellite System
How PLBs communicate with satellites to find and share your location is fascinating. But, to understand this, you need to first understand a little about the Cospas-Sarsat satellite system.
This satellite system is a joint international system that was designed for search and rescue. The system is broken into three orbit radiuses.
The far outer orbit is the geostationary satellites. This orbit the earth at the same speed as the earth turns, meaning they “stand still” relative to its surface.
This allows these satellites to have a constant view of the Earth, meaning they will instantly pick up a distress alert.
The closest orbit is the low earth orbit satellites, which are more limited in the area they can cover, and they take about 24 hours for an entire pass.
But, because they are moving close to the surface of the earth, they can plot your position to an accuracy of a mile during a distress call.
But this requires at least three satellites to pass over you to get a good position fix.
Unfortunately, this can take a long time when calling for help. The system has included many medium-earth orbit global satellites to help with this time delay.
These have a wider field of view than low earth but are also in motion, so they can calculate your Doppler position.
What Happens When You Activate Your PLB?
All right, now you know which satellites are working for life-saving. But how does all that work when you activate your PLB?
The first thing that happens is that your PLB immediately starts transmitting your unique serial number.
At the same time, your GPS receiver starts trying to get a GPS fix. The geostationary satellite will see transmission almost immediately.
Then the low-earth and medium-earth satellites will coordinate your position as they pass over.
In the meantime, the geostationary satellite begins transmitting the signal to a local user terminal (LUT). The LUT is a ground station for the system.
If your PLB has a GPS receiver, getting a proper fix shouldn’t take too long. This data is then also transmitted via the geostationary satellite to the LUT.
Once the other satellites get a reliable Doppler fix, they send this data will as well.
The LUT will immediately decode all this raw data and pass that on to a Mission Control Center.
This center will then contact the rescue authorities in the country closest to your location. Finally, that coordinator will start the rescuer process.
All of this should occur within a few minutes from the time when you activate your PLB.
How Does This Help Your Chances Of Being Rescued?
Once that complete data package reaches the rescue personnel, they know where you are based on your Doppler location and GPS fix.
They also know who you are, thanks to the serial number.
This allows them to contact your next of kin to inform them and get vital information from them.
The adventurer’s family can then give them critical details about your voyage.
This includes the time of departure, heading, vessel type, and time of last contact.
These details are vital and significantly improve the odds of getting home.
🔄 What’s The Difference Between PLBs And EPIRBs?
Another crucial emergency component is the Emergency Position Indication Radio Beacon, or “EPIRB.” If you have read up on EPIRBs, you may have noticed their function is the same as PLBs.
EPIRBs also send a vertical signal at 406Mhz to the Cospas-Sarsat system. That signal also contains your identification number and position data.
So, why are they two different devices?
The significant differences between them come from their different intended uses. As the name suggests, a personal locating beacon is designed to locate a person.
And that person could be anywhere in the world, at sea, or in the wilderness.
EPIRBs are designed for use at sea, and their purpose is more orientated to locate the vessel or life raft to which they are attached.
That’s not to say that they can’t be used as a PLB emergency response, but there are some restraints.
Unlike PLBs, EPIRBs are built to have a battery life of at least 48 hours of transmission.
They are also built like tanks to withstand serious damage in case of a capsize and being tossed about at sea where things can bash into them.
In other words, they are much bigger and heavier than PLBs.
They are also considerably more expensive. EPIRBs are also designed to float upright, so the transmission is always vertical.
In fact, some versions of EPIRBs will automatically activate if they become submerged in water.
⛵ Should You Get A PLB Or EPIRB For Sailing?
The difference between the devices begs the question of which you should get for sailing.
In countries like Australia, EPIRBs are mandatory for recreational use if you go more than 2 miles offshore.
Yet, even though it may not be mandatory for you to carry an EPIRB, it doesn’t mean that you shouldn’t.
The sea is a torturously dangerous environment that can change unexpectedly and violently.
And while you may feel that your cellular phone and VHF radio are enough to keep you from imminent danger, that isn’t always the case.
So, to answer the question of which is best, if you can afford to, you should get both a PLB and an EPIRB, not just for mere redundancy.
For a more detailed comparison, you can check out our article on EPIRB vs PLB.
Consider the scenarios of a capsize or the need to abandon the ship. In both scenarios, the EPIRB should activate if it is automatic.
If it isn’t, you will need to activate it yourself, but what if you can’t get to it because the boat is sinking too quickly or on fire?
Or, what if the EPIRB activates as it should, and you become separated from your vessel and the EPIRB by a current?
For this reason, it is best to have a PLB attached to your person when you go out to sea as a last resort, along with other essential ditch bag items.
🌍 The Limitations Of PLBs In Remote Locations
Unfortunately, like all great devices, PLBs have some limitations, especially in remote areas. The satellites are part of the various types of marine emergency beacons used in maritime safety.
The problem is some areas aren’t covered by the Cospas-Sarsat low-earth and medium-earth orbit satellites. These areas are mostly close to the poles.
In practice, this means that if your PLB is activated, the signal may still be detected by geostationary satellites’ vision. But there won’t be any location data attached.
In other words, the satellite will only see an emergency signal but won’t know where it is coming from.
Even if your PLB is equipped with a GPS receiver, the coverage of GPS isn’t global, so there still won’t be any location data available.
Sure, it does help if just your identification number is transmitted. This could begin a process of trying to emergency contact you or your relatives for more information, which could start a search.
But, with no location data available, the search may take too long to save you.
🚫 The Limitation Of PLBs Without GPS Receivers
While now rarer than a few years ago, there are still PLBs around that don’t have GPS receivers, and these have a crucial time limitation.
GPS position acquisition only takes a few minutes to acquire enough search and rescue satellites and becomes more accurate as time goes on.
But Doppler positioning can take much longer., meaning that if your PLB doesn’t have a GPS receiver, there may be a delay.
Responders will be trying to figure out where to go before launching their vessels to save you. And when you’re at sea, time is crucial.
So, it is well worth spending a little bit more money to make sure that your PLB is also equipped with a GPS receiver.
🔋 PLB Battery Life And Battery Replacement
As I mentioned earlier, PLBs need to have a battery capacity big enough to send a signal for at least 24 hours.
But just because you may never need to activate it, it doesn’t mean that the battery will last forever.
Most PLBs have a battery life of around 5–10 years, depending on the model. Fortunately, your specific model will specify exactly how long the battery is expected to last.
But it is a good idea to replace the battery a little earlier than the maximum time limit. You don’t want to end up on a fouled adventure with a flat PLB.
When the battery expires, you don’t need to throw your expensive PLB in the bin. Instead, you can have the battery replaced and the PLB services by an authorized agent.
This is always a better idea than trying to DIY a piece of vital equipment that your life may depend on.
🔧 PLB Maintenance, Testing, And Storage
Like all your marine equipment, your PLB should be stored in a clean, dry environment.
Although you should have it attached to your person when at sea, you need to keep it clean.
Otherwise, salt and corrosion can build up, which could prevent it from being activated or hinder transmission.
Your PLB may come with a service interval, including the battery replacement mentioned above.
You must stick to this schedule and have the manufacturers review your PLB and replace any faulty bits.
Finally, your PLB should also be tested regularly. To do this, you will need to check the user manual of your specific model first.
Don’t assume you know how because you may accidentally switch it on and start transmitting an emergency beacon.
Typically, there is a test button on the device to test if everything is working as it should. If it doesn’t, you must have it serviced by the manufacturer or agent.
⚖️ PLB Regulation And Certification
PLBs are certified through the Federal Communications Commission. This is because it is a radio communications device, so the FCC must approve all PLBs before being sold.
However, unlike other maritime radio equipment, you don’t need a license to operate a PLB, nor is there a restriction on age.
However, it should go without saying that you should train your children how to use the device and not allow them to play with it.
PLB registration is handled by the National Oceanic and Atmospheric Administration (NOAA). And you are legally required to register your PLB with them.
This registration is the process of linking the PLBs identifier to your personal details. So, it would be exceptionally silly to buy a PLB and not register it.
🔑 Key Takeaways
1️⃣ PLBs work by transmitting a signal to satellites, which then relay the information to local search and rescue services.
2️⃣ While both PLBs and EPIRBs serve similar functions, EPIRBs are typically registered to a specific vessel, while PLBs are personal devices.
3️⃣ It’s recommended to have both a PLB and an EPIRB when sailing, as they serve as vital tools in emergency situations.
4️⃣ PLBs have limitations in remote locations where coverage by Cospas-Sarsat low-earth and medium-earth orbit satellites may be sparse.