The SPOT Messenger and Personal Locator Beacons

Until recently I had never heard of the SPOT. I was familiar with the Personal Locator Beacon, or PLB, but  I had never considered using one.  As we sat around the campfire during a recent North Wash canyoneering trip, people talked of their experience with SPOT- how well it messaged, how they used it for pickup at the end of their treks, how it kept their families happy knowing they were safe, and how it creates an online GPS coordinate database of the ground they cover.

The SPOT sounded interesting, but I have always been one to leave technology behind when going into the wilderness. I have never carried a cell phone, any type of two-way radio, or even a GPS in the bush. For more on my thoughts on the GPS, see my recent blog post . But after listening to peoples’ experiences with SPOT, after doing research for a blog post on rattlesnakes, and after reading recent news articles regarding the use (and misuse) of SPOT and PLB’s  (see Ramkitten’s collection of articles) I have been thinking more about how I could use the device.

The safety of my five year old has also prompted me to take a closer look at the SPOT and PLB’s. In recent years my son and I have been spending more time together in the Utah desert. Rattlesnakes have always been my greatest concern in the bush, and I seem to meet up with them frequently enough. Now that my son is along with me, that concern has become heightened. If keeping him safe means merely carrying another 6 or 8 ounces in my pack, then that is easily done. There is no question that these devices save lives, and are worth their weight and cost during emergency situations.

SPOT,PLB’s, and Avalanche Beacons


The SPOT Satellite GPS Messenger (SPOT 2)- 5.2 ounces without batteries (about 6 ounces with lithium batteries), cost- $149.95 at REI for the device and $100.00 per yer activation fee for basic features.

Being relatively unfamiliar with both SPOT and PLB’s, I began by seeing what REI had to offer.  REI carries a number of PLB’s and both versions of SPOT including the new, SPOT Satellite GPS Messenger,  the ACR SARLink 406 PLB, and the McMurdo Fastfind 210 PLB. Both ACR and McMurdo have a complete line of PLB’s and related survival equipment for all types of outdoor activities.  Do not confuse these devices with avalanche beacons, or transceivers, which are a separate device altogether.  Avalanche beacons transmit a homing signal locally, so that others with a transceiver are able to pinpoint a person’s exact location under the snow.

Common Features

In my research I focused my attention on devices for “land-based” activities- hiking, backpacking, floating rivers, and biking for example- where you might find yourself far from help. The information I provide comes from the spec sheets for the respective devices and phone calls to customer service for each.  Speaking of customer service- I spoke to representatives at SPOT and  ACR  immediately after placing my calls.


The ACR SARLink PLB- 8.9 ounces with battery, cost- $399.95 at REI (no yearly activation fee).

For purposes of presenting SPOT and a PLB, I chose to focus on the ACR SARLink and the SPOT Satellite GPS Messenger.  Should you use either one to call for help, both devices use GPS satellites to find your location and then transmit those coordinates and a distress call to other satellites, which in turn transmit them to a call center. A distress call using the ACR SARLink goes through the government’s SARSAT system, ultimately ending at their control center in Maryland. When you register your ACR SARLink you are given a unique identification code which allows rescue personnel to know exactly who you are so they can seek additional information about your situation. The ACR SARLink transmits a local 121.5 mhz homing signal (line of site), much like avalanche beacons, to search and rescue personnel in your vicinity. The SARLink also has a built in LED strobe.

Unique SPOT Functions

Activating the SPOT S.O.S. function will send your GPS coordinates and distress call through a commercial satellite to the GEOS Alliance, a private company in Texas. In Tracking Mode the SPOT will retrieve your coordinates every 10 minutes and store them on your SPOT personal web page for 30 days. This page can be shared with friends and family. The coordinates can be exported and saved in Excel or Google Earth formats. The Track function continues for 24 hours after the Track button is depressed. You must reactivate the Track function every 24 hours.

Using the Check-in function you can send your present coordinates and a custom message to up to 10 email addresses or phone numbers as a text message. Using the Custom Message function you can create a different message to be sent to the same or other email addresses or phone numbers.  Finally, you can create a custom “Help” message for up to 10 contacts- this can be used to notify contacts that you are at a resupply or pickup location, for example.

Cost and Activation Fees

There is a difference in the initial cost between the two devices. PLB’s are more expensive across the board than SPOT.  But it is important to look beyond the initial cost of the device.  You will spend 400 dollars on the ACR SARLink. You will spend 150 dollars for the SPOT Satellite GPS Messenger.

To keep your SPOT active and to use the basic functions- S.O.S., Help, Check-in, and Custom  Message- costs another 100 dollars per year. Additionally you can choose to pay $7.95 for yourself and each family member, per year, which covers up to $100,000 for each individual in search and rescue costs (see the GEOS Alliance website for full details). The Track function costs $49.99 per year, Road Assist can be added for $30.00 per year, and replacement insurance for the unit can be added for $17.95 per year.

There is a one-time activation for the SARLink, and that is included in the initial cost of the device.

Batteries and Battery Life

The ACR SARLink uses a proprietary lithium battery that is costly. A replacement battery for the SARLink will cost around 160 dollars, not including shipping. The battery only needs to be changed every 5-6 years, or after emergency use of the device. The battery change should be done by an authorised service center where they will also verify the seal on the unit, reset the battery use indicator, and perform a number of tests on the unit to insure that it is ready for use. Battery life in emergency mode is rated at about 35 hours.

The SPOT uses 3- AAA lithium batteries, available at your local grocery store for about 7 dollars (the first generation of the device uses 3-AA batteries). The use life of the batteries in the SPOT depends on the operation of the device. In tracking mode you will get about 14 days of use on one set of batteries. If you use the message functions- the Help, Check-in, or Custom Message function, you can send up to 1900 messages on a set of batteries.  So if you use the Tracking function and send a message or two a day, you can probably expect to change the batteries every 10 or 12 days.  The SPOT will send a  message every 5 minutes for 7 days in the S.O.S. function.  All of these time estimates are assuming new batteries.

Waterproofing and GPS Accuracy

Both devices are rated waterproof to 5 meters in depth for 1 hour. You could safely swim with either for extended periods, for example making your way out of rapids or swimming across a river.

There is a difference in GPS accuracy in the devices. The SPOT is accurate to about 6 and 1/2 meters.  The SARLink is accurate to within 100 meters.  The homing feature on the SARLink more than makes up for its being less accurate than the SPOT.


According to the SARSAT/NOAA website, there were 282 rescues in the United States in 2008 initiated through SARSAT. Of these, 68 people were rescued in 35 incidents using the PLB to call for help. No further details were given about the rescues. You can read a few ACR PLB rescue stories at the ACR website.  According to the GEOS Alliance website, 400 people were rescued using the SPOT to call for help in 2008. No details were given regarding the number of incidents involved. You can read about some of the SPOT rescues at the SPOT website.

After researching the SPOT and the ACR SARLink, I cannot say that one is a better choice than the other. If you are looking for peace of mind in the form of 6 or 8 ounces, you have found it in either device.  If your goal is to carry a device to call for help in the event that rescue is needed, the PLB will suit your needs.  If you are interested in communicating your location daily, and tracking your progress in the wilderness, then the SPOT is for you.

Ultimately one of these devices may save your life, but they are not a license to act without caution.  A PLB or SPOT is not a substitute for knowledge, preparedness, or common sense.  Recent unnecessary SPOT distress calls may signal the need for a closer look at who pays for search and rescue costs. Proper use of these devices by everyone will keep us all safe at a reasonable price.

10 Responses to The SPOT Messenger and Personal Locator Beacons

  1. Ramkitten says:

    This is a great comparison. Thank you for all of the information.

    I’ve still not used the SPOT, but our SAR team practices on the rescue end with PLB’s, which we’ve had some trouble pinpointing in the past during trainings. We haven’t had to actually locate one in the field during a real mission, though, at least in the past two years or so since I’ve been on the team. We have gotten a SPOT-relate call, though, which came about because the user didn’t check in. Really, though, it ended up being a miscommunication b/w the hiker and his mom, with the hiker not thinking he had to check in with his coordinates and his mom thinking he was supposed to do so at a certain time. After an all-night search for the young man during a severe thunderstorm, he was found to be just fine and oblivious to the fact anyone was looking for him. Oh well, at least it ended well. Still, prior communication b/w the SPOT user and the ones back home they’d be sending the check-in coordinates to is pretty important.

  2. Max says:

    There are a few more critical emergency signaling differences between the SPOT and ACR SARLink:

    Power and Frequency Differences:
    Power and Frequency are two key areas to consider when researching a life saving device. Satellites are thousands of miles away from earth, so your beacon’s signal needs to have enough power to travel that far and be able to go through anything between you and the satellite (trees, weather, out of slot canyons, etc.).

    POWER: SPOT is powered by 400 milliWatts while ACR 406 MHz PLBs and EPIRBs use 5 Watts. You would need 12.5 SPOT units to equal the POWER of one ACR PLB or EPIRB! When your signal has to travel 22,000 miles to reach a satellite, you want to make sure you have more than enough power to get it there!

    FREQUENCY: The basic principles of frequency are that the lower the frequency, the easier it can penetrate buildings, trees and meteorological activity that appear between the transmitting device (PLB, EPIRB or SPOT) and the receiving device (the satellites). FM radios and TV channels work on a lower frequency which is why they can penetrate buildings and the environment pretty easily. Now think about radar which uses a really high frequency. Radar works by hitting an object and bouncing off, that’s how radar knows where to place an airplane on the radar screen. So the higher the frequency, the less likely it can penetrate things in between, the lower the frequency, the easier it can penetrate. 406 MHz PLBs and EPIRBs use a dedicated frequency set up by the search and rescue community that is in the same range as UHF TV stations. SPOT uses the 1.6GHz frequency which is four times higher in the frequency spectrum. This means SPOT’s frequency is four times less likely to go through an object or weather than the lower 406 MHz frequency.

    Considering power, combined with frequency, ACR’s 406 MHz beacon stands head and shoulders above satellite messenger systems like SPOT. ACR has 12.5 times more power and is four times more likely to penetrate objects in between the beacon and the satellite than SPOT.

    Redundancies: PLBs and EPIRBs have multiple ways to contact SAR in order to get you rescued. SPOT has one single transmission method. PLBs and EPIRBs can contact SAR via 406 MHz, which locates your beacon using Doppler Shift, it can contact SAR using GPS data and it also has a 121.5 MHz homing frequency so when SAR forces get a few miles away from you, they can home in directly on your beacon and find you faster. SPOT uses GPS only to send its location. If you cannot download GPS, SAR will have no idea where you are!

    Coverage: EPIRBs and PLBs use the Cospas-Sarsat satellite system which contains 2 different satellite systems (LEOSAR – Low earth orbiting and GEOSAR – Geostationary). These two systems cover every inch of the planet. SPOT tracker is part of Globalstar and uses the Globalstar (Nasdaq: GSAT) satellite system which only covers a certain percentage of the earth, but has quite a few locations that are undetectable.

    The SPOT is an excellent tool for personal tracking and checking in with friends and family to say “I’m OK”. In fact, I own a SPOT myself and carried one on a remote 6 week kayaking expedition in the Pacific North West last summer – I was able to check in every few days and send my friends GPS coordinates so they can track the progress of the expedition. However, the SPOT was brought purely for those tasks, not for emergency use – for emergency use I wanted to ensure that I had a device that was certified to the highest standards, was fast, and provided more than just GPS signaling – for these reasons I carried an ACR SARLink GPS equipped PLB.

    • Thanks Max! You have provided some of the critical information that I searched for, and it sounds like you are quite knowledgeable in the field of satellites. I called both companies and asked them to explain the differences to me between the two devices, and to explain to me why I should buy theirs and not the other. I specifically asked about how each used satellites. I knew about the gaps in coverage for SPOT in certain parts of the world, but not much more than that. It was obvious that they operate differently. But multiple calls did not get those differences explained. I felt from the very beginning that it was like comparing apples and oranges as they say, but none of the reps that I talked to told me that nor, in the case of the SARLink, could they explain the differences and the apparent superiority of the SARLink satellite communication system (using two satellite systems instead of one).
      Thanks for finally giving me those answers. I will be sure to Tweet this info so that all of those who read my post can see the more technical side of the comparison.
      One question about the battery use though- the specs of the SARLink state that it transmits 35 hours in emergency mode, the SPOT for 7 days. I understand that the signal itself, based on the frequency of the SPOT for example, may or may penetrate obstacles as well as the SARLink signal. I just wonder how the extra 5 1/2 days of possible transmission time might factor into the equation? Granted this battery life is best case scenario- there are many variables I have left out.
      I did get your point about the SPOT needing to get GPS data before it can even transmit your distress call. And the fact that the SARLink doesn’t even need it and can still transmit.
      The battery life issue was just an observation.
      Any more comments you would like to make would be greatly appreciated. By the way, I still have not purchased either device, but plan to very soon for the coming season in the bush. I was leaning towards the SPOT for the reasons you point out- being able to check in daily for example. But the recent recall due to power issues makes me wonder.
      Thanks again,

      • Max says:

        Hey Gerald

        I’m glad you found my reply useful. A few clarifications:
        – The SPOT unit will still send out a distress message even if it doesn’t have any GPS data. However this distress transmission will be a simple “help me” without any geo-location, hence not very useful for SAR. In comparison, a 406MHz PLB distress signal (also without any GPS data) still identifies your location to within 5km using Doppler triangulation (LUTs detecting the non-geostationary satellites of the Cospas-Sarsat system interpret the Doppler frequency shift heard by LEOSAR and MEOSAR satellites as they pass over a beacon transmitting at a fixed frequency. The interpretation determines both bearing and range). Of course if the PLB is able to get a GPS-lock then your location is even more accurate. The reason I feel this distinction is important is because the GPS-lock is the least reliable part of the distress system – the upper limit of a GPS cold-lock is around 20min (regardless of whether you’re using a SPOT or a PLB, they both rely on the same GPS satellite network). Furthermore, a GPS-lock under canopy or in a slot canyon is very unreliable, because the GPS unit requires a minimum of four visible satellites). SPOT relies entirely on this GPS system to acquire coordinates. With PLBs, as soon as you press the distress button, you will be able to immediately send out your location to within 5km using a powerful 5 Watt blast of the 406MHz signal, then if a GPS lock is possible the following transmissions (every 50 seconds) will include the GPS coordinates.

        – As I mentioned previously, the SPOT unit uses the Globalstar communications satellite network, which is not designed for SAR and does not have dedicated channels listening for SAR distress signals. This means that your SPOT, similar to a Sat Phone, needs to first listen in order to find a free slot before it can transmit your distress signal to a Globalstar satellite (acquisition time). This introduces extra delay into the system. Comparatively, the PLBs Cospas-Sarsat system is dedicated to 406MHz distress signals, so a PLB can begin transmitting distress signals immediately, and they will be picked up by the satellites immediately as well. In short what I’m trying to convey is that the Cospas-Sarsat system has been designed for the ground up specifically for just SAR distress signaling. The SPOT unit uses a commercial communications satellite network which is not dedicated for SAR nor specifically optimized to handle SAR distress calls.

        On the subject of battery life, the much shorter (35hr) transmission time of the ACR PLB is because the ACR unit transmits at a much much higher power (minimum 5 watts, typically 6.3 watts), hence drains its batteries quicker compared to the weaker 400 milliWatts SPOT signal. PLB’s transmit every 50 seconds during that 35hr period, while the SPOT unit does not guarantee any transmission rate (only that most likely something will be sent within 20 minutes). The 35hr time window is definitely more than enough to relay the message to the satellite. Plus, I’d much rather have a shorter transmission time of a powerful signal rather than a longer transmission time of a weak signal that has a lower chance of actually reaching the satellites.

        Another thing to consider when comparing battery life is to look at the different testing and certification requirements between the two units: Personal Locator Beacons, like EPIRBs, must be submitted to an independent test lab that verifies the frequency, operating life, testing in extreme temperatures, environmental testing, etc. From there, the product must go to Cospas-Sarsat, USCG and finally the FCC (or other comparable agencies in each country) for approval to certify that the EPIRB/PLB meets the standards for Radio Technical Commission for Maritime Services (RTCM) and that it exceeds required operating and mechanical conditions that will appear in the marine environment. PLBs and EPIRBs are rigorously tested by governing agencies to confirm they will work properly in the environment. This is a big difference from SPOT which only has to self-test and self certify that it meets Part 15 FCC. So the “up to 7 days” that SPOT reports in its spec sheet might not be a very well grounded statistic…

        One note on the GPS coordinates for the SPOT and GPS equipped PLBs such as the ACR SARLink: I’m not sure about the exact GPS chipset used in either of the units, but on average autonomous civilian GPS horizontal position fixes are typically accurate to about 15 meters (45ft). From my experience the SPOT unit is consistent with these figure. HOWEVER, any PLB or EPIRB is only accurate to 100m – a much bigger error range! The reason is actually not the inferiority of the unit’s GPS chipset itself but because the space in the hex message protocol (set by Cospas-Sarsat) for position information is limited, so transmitted accuracy is approximately +/- 125 meters. In my opinion 100m range accuracy is plenty enough for SAR purposes, however might not be accurate enough if you wish to use the device for non-emergency use (to plot trail heads, etc). The SPOT is by design a great GPS tracker, accurate to 15m on average, however I still feel that for emergency signaling use PLBs are far superior by design.

  3. Thanks again for the great comments. On thinking more about it, I can plainly see why you carried both on the trip you mentioned. They are two very different devices. Would you mind if I posted your comments on my web page where I have re-posted this blog? Your comments are so informative I feel they need to be promoted. Do you have a blog or web page that you would like me to link to? I’d be happy to do that.

  4. Max says:

    Hi Gerald

    You’re more than welcome to re-post my comments. I’m glad you found them informative.

    At present I don’t really have much of a ‘web presence’ so nothing to link to, but thanks for the offer! 🙂

  5. One other interesting piece to add is that the SARLink PLB now can send “I’m Ok” messages and also include your GPS position. ACR just launched which is an optional subscription service. Its not a SPOT like tracking service, but its a peace of mind messaging services. Only $39 per year for the basic plan, and its completely optional.

    • This is a great feature of the SPOT, one that has nearly sold me on it. I am glad to hear that it will be available with SARLink as well. I will follow the link and take a look at the particulars. My one concern would be battery life- considering the cost of replacing the battery, I wonder just how many “okay” messages I would want to transmit.
      Thanks for the heads up on the new option.

  6. […] the SPOT Versus PLB Question In the last week I have had a few comments on my blog post about the SPOT GPS Messenger and Personal Locator Beacons. The comments and the information sent to me is just too important not to post, especially for […]

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