Quick answer: a personal locator beacon (PLB) is a one-way emergency device that sends a distress signal on 406 MHz to the international Cospas-Sarsat satellite system; in the United States the alert goes through NOAA to rescue coordinators. PLBs need no subscription but must be registered with NOAA. A satellite messenger uses a commercial satellite network to send an SOS to a private response center and, on most models, lets you text and share your location, but it requires a paid plan. Some newer phones can also text emergency services by satellite. Choose a PLB for a simple, long-lasting emergency-only device; choose a messenger if you want two-way communication and trip check-ins.
Cell coverage ends quickly in national forests, canyons and backcountry areas, often well before the trailhead. When something goes wrong out there, a dead-zone phone cannot call for help. Satellite devices close that gap. They have become smaller and cheaper, and many campers now carry one on solo trips, remote drives and backpacking routes.
The choices can be confusing, though. Personal locator beacons, satellite messengers and phone-based satellite features all promise “SOS,” but they work differently, cost different amounts and suit different trips. This guide explains the differences. It is part of our camping safety guide, which covers emergencies, weather and wildlife.
Sources: NOAA Search and Rescue Satellite Aided Tracking (SARSAT) program, beacon registration and false-alert guidance; International Cospas-Sarsat Programme; Federal Communications Commission (FCC) rules for 406 MHz beacons (47 CFR Part 95); U.S. Air Force Rescue Coordination Center information via NOAA SARSAT; device makers’ published specifications for satellite networks (Iridium, Globalstar); Apple, Google and T-Mobile published information on phone satellite features; New Hampshire Fish and Game Department, Hike Safe Card program. Checked October 2026.
The Three Types of Satellite Emergency Devices
| Feature | Personal locator beacon (PLB) | Satellite messenger | Phone satellite SOS/texting |
|---|---|---|---|
| Network | Government Cospas-Sarsat system (406 MHz) | Commercial satellites, such as Iridium or Globalstar | Commercial satellites linked to certain phones and carriers |
| Who receives the SOS | Government rescue coordination (NOAA in the U.S.) | A private emergency response center that contacts local rescuers | Emergency relay centers or services, depending on the phone and carrier |
| Two-way messaging | No (one-way alert) | Yes on most models | Yes, limited, varies by phone and plan |
| Subscription | None | Required | Varies; some features free for a period or included in plans |
| Battery | Long-life battery, not rechargeable on most models | Rechargeable | Phone battery |
| Location sharing and check-ins | No | Yes | Limited, varies |
| Registration | Required with NOAA in the U.S. | Account setup with provider | Phone setup |
How a Personal Locator Beacon Works
A PLB is a small, rugged transmitter designed for one job: telling rescuers that a life is in danger and where. When you activate it, it sends a digital distress signal on 406 MHz to satellites in the Cospas-Sarsat system, an international search-and-rescue program founded by Canada, France, the United States and the former Soviet Union. Satellites relay the alert to ground stations and mission control centers.
In the United States, NOAA operates the SARSAT program and the U.S. Mission Control Center. NOAA passes inland alerts to the Air Force Rescue Coordination Center, which works with local search-and-rescue teams, sheriffs’ offices and other agencies. Most PLBs also include a GPS receiver, so the alert carries your coordinates, and a 121.5 MHz homing signal that helps rescuers close in on your location.
PLB strengths
- No subscription. You buy the device and register it for free.
- Government system. Alerts go directly into the official search-and-rescue system.
- Reliable, purpose-built design. PLBs are built to strict standards and are designed to transmit for at least 24 hours once activated.
- Long battery life. Batteries typically last several years on the shelf; the manufacturer specifies a replacement date.
- Simple to use. Extend the antenna, give it a clear view of the sky and press the button.
PLB limitations
- One-way only. You cannot describe the emergency, ask for advice or tell rescuers you are fine.
- No routine messages. You cannot send “running late” or “made it to camp.”
- Battery replacement is usually done by the manufacturer or an authorized service center.
- Emergency use only. A PLB is meant for grave and imminent danger.
Registration with NOAA
In the United States, FCC rules require 406 MHz beacons to be registered with NOAA. Registration is free and is done online through NOAA’s beacon registration database. You list the beacon’s unique identification number, your contact information, emergency contacts and the kinds of trips you take. NOAA requires registrations to be renewed every two years, and you should update them when your contact details change.
Registration matters. When an alert arrives, rescuers use your registration to call your emergency contacts, confirm the alert and learn what you might be doing. An unregistered beacon can slow the response.
How a Satellite Messenger Works
A satellite messenger is a handheld device that connects to a commercial satellite network. Devices that use the Iridium network, for example, have global coverage, while devices on the Globalstar network cover large parts of the world but not every region. Most current models offer:
- An SOS button that sends an alert, with your location, to a private emergency response coordination center staffed around the clock. That center contacts the appropriate local rescue agency and relays information.
- Two-way text messaging with friends, family and the response center, often through a paired phone app.
- Location tracking, so people at home can follow your progress on a map.
- Preset check-in messages, such as “All OK, camping here tonight.”
- Weather forecasts on some models.
Messenger strengths
- Two-way communication. In an emergency you can say what happened, how many people are hurt and what you need. Rescuers can tell you what to expect.
- Non-emergency messages. You can tell someone you are delayed, which can prevent an unnecessary search.
- Rechargeable. Most charge by USB.
Messenger limitations
- Subscription plans. You pay monthly or annually, and plans vary in how many messages and tracking points they include.
- Battery management. A rechargeable device can die if tracking runs constantly or you forget to charge it. Our guide to portable power for camping covers battery banks.
- A private relay. The SOS goes to a commercial response center first, which then contacts official rescuers. That works well in practice, but it is one more step than a PLB.
Phones With Satellite Features
Recent smartphones can connect to satellites in some situations. Apple introduced Emergency SOS via satellite with the iPhone 14 in late 2022, using the Globalstar network. Google added Satellite SOS to some Pixel phones in 2024. T-Mobile launched satellite texting with Starlink in 2025 for compatible phones. These features have expanded quickly, and availability depends on the phone model, operating system, carrier, plan and country.
Phone satellite features are a real step forward, and they may save lives. Keep their limits in mind:
- You need a clear view of the sky, and connecting can take time, especially under trees or in narrow canyons.
- Coverage areas and supported countries vary.
- Your phone’s battery powers everything: navigation, photos, light and messaging.
- Phones are fragile compared with a rugged beacon, and many are not waterproof enough for a river crossing or downpour.
For many car campers on established routes, a satellite-capable phone may be enough. For remote, solo or long trips, a dedicated device is a stronger backup.
Which Should You Carry?
| If you… | Consider |
|---|---|
| Want a simple emergency device with no monthly fees | A PLB |
| Want to text family, share your location and send check-ins | A satellite messenger |
| Mostly car camp near roads and own a satellite-capable phone | Your phone’s satellite feature, plus a charged power bank |
| Camp or hike solo in remote areas | A PLB or a messenger, ideally with a phone as a backup |
| Lead a group or family trip into the backcountry | A messenger for communication, with a PLB as a backup on longer trips |
| Paddle, hunt or travel in very remote country | A PLB clipped to your body, plus a messenger if communication matters |
Our guide to solo camping safety has more on planning trips alone.
How to Use a Satellite Device Well
Before the trip
- Register or activate the device. Register PLBs with NOAA; set up messenger subscriptions and contacts.
- Charge and test. Most PLBs have a self-test function; follow the manufacturer’s limits on how often to use it, since tests draw on the battery. Messengers can send a test message.
- Learn the menus at home, especially how to start and cancel an SOS.
- Leave a trip plan with someone, including your device type and what messages to expect.
- Update emergency contacts so they know they may be called.
On the trail
- Carry the device on your body, such as on a shoulder strap or belt, not deep in a pack that could be lost in a fall or river.
- Keep the antenna area unobstructed and the device charged.
- Send regular check-ins if your device allows, especially when plans change.
In an emergency
- Decide whether the situation is life-threatening or at risk of becoming so. That is what SOS is for.
- Move to open sky if you safely can.
- Activate the SOS according to the device instructions and leave it on.
- Stay with the device and stay put unless staying is unsafe. Our guide on what to do if you get lost while camping explains how to wait for rescuers.
- With a messenger, share details: injuries, number of people, supplies and conditions.
Accidental activations
False alerts happen. NOAA asks beacon owners who accidentally activate a PLB to turn it off and contact the rescue coordination center or NOAA as soon as possible, so a search is not launched. Messenger users can usually cancel an SOS through the device and should confirm the cancellation with the response center.
Does Rescue Cost Money?
In much of the United States, search-and-rescue is provided by public agencies and volunteer teams without billing the person rescued. That is not universal. Some states allow agencies to seek reimbursement in certain circumstances. New Hampshire, for example, can bill people whose negligence led to a rescue, and its Fish and Game Department sells a voluntary Hike Safe Card that generally exempts holders from that liability except in cases of recklessness. Helicopter or ambulance transport after a rescue can also be billed by the provider. Some messenger plans and memberships offer search-and-rescue cost coverage; read the terms carefully.
Fear of cost should never stop you from calling for help in a real emergency.
Common Mistakes
- Buying a device and never registering or testing it.
- Keeping a PLB in the car during hikes.
- Letting a messenger battery run down with constant tracking.
- Using SOS for non-emergencies, such as a dead car battery when you are safe and can walk out.
- Assuming a phone feature works everywhere, without checking coverage, compatibility and plan details.
- Not telling contacts what to expect, which can cause panic when a check-in is missed.
Frequently Asked Questions
What is the difference between a PLB and a satellite messenger?
A PLB sends a one-way distress signal through the government Cospas-Sarsat system and needs no subscription. A satellite messenger uses a commercial network, offers two-way texting and tracking and requires a paid plan.
Do I have to register a personal locator beacon?
Yes. In the United States, FCC rules require 406 MHz beacons to be registered with NOAA. Registration is free and must be renewed every two years.
Can my phone call for help by satellite?
Some newer phones can send emergency messages by satellite, depending on the model, carrier and location. You need a clear view of the sky, and features vary, so check your phone’s settings before the trip.
Does a PLB need a subscription?
No. PLBs have no monthly fees. You pay for the device and eventual battery replacement.
How long does a PLB transmit?
PLBs are designed to transmit for at least 24 hours after activation, and many last longer. Check your model’s specifications.
What happens after I press SOS?
A PLB alert goes through the satellite system to NOAA and on to rescue coordinators, who contact local responders. A messenger SOS goes to a private response center, which contacts rescuers and can message you back.
