How to Choose a Personal Locator Beacon or Satellite Messenger

The Explorer+ has a large display with a menu that is easy to navigate.
Article By:
Chris McNamara and Jediah Porter

Last Updated:
May 27, 2018

Communication is key. This is a fundamental, human truth. For wilderness adventuring, beyond the reach of modern cell signal, connection is trickier. Many of us go to the wild to escape the tether of modern communications, but we also seek to mitigate the consequences of ill fortune. Some, of course, need more routine contact with the outside world, for one reason or another. Enter, the array of satellite messengers, personal locator beacons, and other backcountry communication technologies. We are here, now, to guide you through your choices and demystify the options. We will walk you through a step-by-step process of choosing a device suited to your needs and wishes.

The inReach app lets you access backcountry satellite communication with front country convenience.
The inReach app lets you access backcountry satellite communication with front country convenience.

Types of Wilderness Communication

First, the confines of our discussion — we limit our discussion to those products and services that provide contact, without cell signal, in the wild. We further limit our discussion to those devices and systems that provide digital, text-based communication. Voice transmission (as provided by satellite phones and two-way radios) is, paradoxically, less clear and more complicated to execute. Sometimes, of course, it is the best choice. We are, here, discussing text-based communication.

Emergency Messaging

The simplest, and arguably most important, type of communication is the SOS message. Sending a message that contains your location, as deduced by GPS triangulation, and alerts a dispatcher to your need for help is the most common, and least expensive, sort of backcountry communications. An SOS message like this, regardless of which system it employs, conveys nothing more than your location and that you need help. This is, therefore, suitable only for "life or limb" emergencies. Transmitting more nuanced information about the nature of your emergency is impossible. Some devices, predominantly those using the COSPAS-SARSAT network, only perform SOS messaging.

In our review, the ACR ResQLink+ and OceanSignal rescueME PLB1 use the COSPAS-SARSAT satellite system and offer little more than SOS functionality.

These devices offer comparable access to the COSPAS-SARSAT network  the Ocean Signal is just half the size of the ACR ResQLink.
These devices offer comparable access to the COSPAS-SARSAT network, the Ocean Signal is just half the size of the ACR ResQLink.

Non-Emergency Messaging

What, if you just want your loved ones to know that you are ok? The lack of an SOS message should be reassuring to your emergency contacts in civilization ("no news is good news"), but it isn't authoritative. If something really, really bad happens, you may be unable to activate the SOS mode on your device. If this uncertainty is overly stressful to your loved ones, having the option to send an "I'm OK" message is of value — even better if that "I'm OK" message contains information about your location. Because the COSPAS-SARSAT network is for emergency use only, equipment leveraging that technology is not suited to sending "OK" messages. Any device that sends an "OK message" must use a different, civilian, network.

SPOT inc, with their flagship device, pioneered the widespread adoption of "OK" messaging in 2007. The SPOT device, now in its third generation, is a sort of industry standard and can be purchased, registered, and used to send both SOS messages and a couple different types of "OK" messages. The Garmin InReach explorer+ can also be configured to send a few different kinds of "OK" messages. Different types of "OK" messages include customizable text (usually pre-programmed at home) and automated location transmission on some pre-set interval (usually referred to as "tracking", this is often sold as an additional, significant feature. Really, "tracking" is just sending a series of "OK" messages, automatically and on a regular interval).

Two-Way Messaging

What if, then, you want to send more nuanced information from the wild? "Body and minds are all well, but this flooding creek will delay our exit a day. Don't worry about us in the meantime". This sort of targeted information is impossible with the preprogrammed "OK" message devices and systems. A device that can send a message like this, with no more advanced functionality is currently theoretical. (There was once a SPOT device that could send customized messages from the field, but it isn't on the market any longer.) If you want to communicate in this manner, you need to look for two-way communication options.

In many cases, two-way communications would be very nice. Being able to request certain types of field weather and conditions information, for instance, is of great value. For maintenance of all sorts of relationships, regular, casual communication is very nice. Two-way texting from wild spaces currently requires an InReach device or a well-built GoTenna Mesh network.

Example of the InReach messaging when paired with a smart phone.
Example of the InReach messaging when paired with a smart phone.


Really, there are two major questions you must be asking. We just discussed the main one. What sort of communications do you want and require? After that, the remaining, albeit small, consideration, is coverage.

Communication Networks

There are a few different communication networks you must understand for non-emergency messaging. All of them can also send SOS messaging.

Public — COSPAS-SARSAT is the moniker for a global network of satellites configured specifically for Search and Rescue communication and positioning. Devices made to access the COSPAS-SARSAT network do three things with the push of one button. Generally, these devices have just this one button to push, and just this one purpose to execute. Activating the SOS button of a COSPAS-SARSAT system PLB (Personal Locator Beacon is a phrase usually used to identify COSPAS-SARSAT devices):
  • First ascertains location with regular GPS triangulation.
  • Then sends that location, as well as identifying information programmed into the device, to the COSPAS-SARSAT satellite network.
  • Finally, the device transmits a distress signal on a different frequency that can be received and position-located by aircraft.

Depending on your location and the country you registered of your COSPAS-SARSAT PLB with, the emergency satellite message and associated location and identification information is transmitted through one of a few national Search and Rescue (SAR) dispatch organizations. That SAR dispatch organization (in the United States it is a subdivision of NOAA) then works to secure the most local and most effective SAR resources. The required PLB registration, emergency dispatch protocol, and resource-acquisition that accompanies a COSPAS-SARSAT activation is a tax-payer-supported "free" service.

In an emergency  find the clearest view of the sky you can  deploy the PLB1's antenna  and push SOS.
In an emergency, find the clearest view of the sky you can, deploy the PLB1's antenna, and push SOS.

Private — The next type of emergency messaging is found in the private sector. Subscription-based devices and services employ one of a few commercial satellite communication networks to simulate the COSPAS-SARSAT response. With these devices, properly configured and subscribed, the user pushes an SOS button and the device ascertains location with GPS signal and sends the info to a satellite and on to the ground. To this point, functionality is the same as on the COSPAS-SARSAT system. Devices using private sector satellite networks do not transmit the secondary, aeronautical distress signal. The emergency message, with location and identity information embedded therein, is transmitted through a corporate dispatch office and on to local SAR resources. Examples include SPOT's Globalstar and Garmin's Iridium.

Inreach explorer
Inreach explorer

Network — Finally, local, ground-based communication networks that cover wilderness and overlap with friendly users within cell signal can be used to summon help for those in an emergency situation in the backcountry. This system relies on somewhat fickle local reception as well as the manual relay of information to the appropriate "front-country" dispatch resources.

In other parts of the world and in other sectors there are even more communication networks and protocols. These are just the main players.

Because of the currently limited selection, communication type and signal coverage are tied together. However, there are exceptions. Essentially, you have the choice of global satellite coverage, regional satellite coverage, or a locally "built" terrestrial network. For truly worldwide coverage, COSPAS-SARSAT and the Iridium network are the only viable options. Globalstar, employed by SPOT devices, is one we would consider being "regional". It is entirely possible that the Globalstar network will cover everywhere you might travel. Finally, the GoTenna Mesh "network" is very much localized to where you and your friends are recreating.

We sent texts 3.2 miles outside of cell phone range in flat terrain with the GoTenna.
We sent texts 3.2 miles outside of cell phone range in flat terrain with the GoTenna.


In your shopping, you will discover that devices sometimes come with more features than mentioned above. Notably, since SOS response requires GPS data, the devices include GPS antennae. With the hardware already there, manufacturers have taken steps to add navigational features to some products. With battery power precious, smartphone navigation being super accurate, and simplicity paramount in emergency situations, we encourage you to think very critically before you rely a great deal on the navigational features of your communication device. At OutdoorGearLab we value multi-functionality. However, communication devices are somewhere we might draw the line. Keep it simple, is our advice.

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