Reliability of SPOT?

In another post, where I asked ops what first aid training they acquire, several respondents stressed the importance of a SPOT or other Personal Locator Beacon (PLB) in case of medical emergency. A variety of PLB’s are out there; the InReach system that Garmin offers, having purchased Delorme specifically to get the InReach technology, is another. I don’t own one yet but find myself sorely tempted.

I have not seen discussion of the accuracy of PLBs. We all seem to assume they are like GPS - push the emergency button, the system sees where you are, and help is on the way. This may not be true. This story describes a highly publicized death of a hiker on Mount Washington in New Hampshire. Other accounts are available by searching the name of the unfortunate victim. You can argue with several of the decisions the hiker made, but it seems clear that when she triggered her PLB (I believe it was a SPOT), the system sent would-be rescuers location data that was up to a mile wrong. By the time they found her she was dead.

This prompts some questions for this tech-savvy audience:

  • Is there anything PLB users can do to minimize the chance that they, too, will be mis-located when they most need to be found?

  • Are some technologies better than others? I have read that the ACR ResQLink and other PLBs designed for aviation rescue are more reliable than SPOT, InReach, and other technologies marketed to recreational users, but I’ve seen no data to support the claim.

  • What do we know about the limitations of each of the the different types of PLB technology?

Thanks and 73,

Scott, a PLB is a very different device to an InReach or SPOT.

I would trust my safety to a PLB and would NOT trust it to an InReach or SPOT device.


I have used both Spot and InReach and was disappointed in the ability of Spot to get a signal out at all. I am much happier with my Garmin InReach Explorer+ and Inreach Mini. The GPS function seems pretty accurate. I have only the Security Plan but it allows free preprogrammed text messages to one person. These Txts include the GPS location. My wife appreciates getting the updates. BTW, I am using the Mini now and will be selling the Explorer+

Dave AE9Q

So I have used the Iridium system in a Search and Rescue capacity (National Guard was deploying us with their Iridium Nano’s are not quite InReach (had spot here originally), but it is the same service provider). This is definitely not scientific nor a large enough sample to be definitive however I have seen the system fail 2 of the 3 times we deployed with them. The first incident where we had issues was literally a problem with the Iridium system. The second time WX was the factor but our packets were suffering from a 45 minute delay from the time we sent till they were received back at the command post. Fortunately I had my APRS enabled on my FT1 and I was able to communicate with the command post that way as well as they could track me. The 3rd time we deployed with the Iridium nano’s it worked great. These samples were from ~15 months time span in 2017 and 2018. In all three cases it was a local California Guard unit that was responsible for setting us up with these so at least that parameter was not a changing one. Just my experience, and I know plenty others have had great experiences, but i’m not that impressed with satellite services overall, not when most of the US has good APRS coverage.

Well Google is our friend :wink:

However in brief the various types of satellite communicators (SPOT, Garmin) are designed primarily to offer satcoms at a price geared towards the leisure user. Some of them also offer mapping (to appeal to people who want to carry just one device). They may also offer a “distress” function. The big difference between them and PLB (which is not just designed for aviation use), is in the way the distress message is handled. The communicators generally go to a commercial call centre.
PLBs’ distress signals are routed direct to a dedicated SAR coordination centre. PLBs have another advantage in that most of them also transmit a homing signal to help the SAR team locate you when they are on scene

Only you can decide which type of device suits your needs best, I’m not advocating one or t’other. Hope that helps, but the various websites will give you full details of the capabilities. I have no personal experience with the communicators mentioned, but a wee bit with PLBs

Iridium NANO uses the Iridium network of satellites whereas SPOT uses GlobalStar satellites. It depends on where you are on Earth, but for more extreme latitudes there is no SPOT coverage as their satellites are not in polar orbits. Coverage is worse once you move further beyond 54N or 54S. Iridium should give the same coverage worldwide as they have more satellites in polar orbits. That nice Mr. Musk has just launched a load of replacement satellites to extend their network and to replace older satellites nearing their end of life.

My home rolled satellite spotter use Iridium SBD messaging and normally has a 20-30sec latency on sending a spot to it appearing on SOTAwatch, It’s only failed twice. Once when tree coverage of the sky was about 45% and once when it was unable to gain sync to the network. It transmits on about 1.6GHz using a 25mm square ceramic patch antenna and the fact that 45% tree cover stops it working makes it unsuitable for any safety of life use IMHO. I could fall or break a leg when walking in a forest as much as I could when out on an open mountainside. This is the real difference of a safety PLB compared with a leisure PLB/messaging system.

A PLB will be much more reliable and is always ready for use during its lifetime. Every 5 years typically it will need servicing (i.e new battery) but it doesn’t need to be charged up before you go out and you don’t need to worry about whether your InReach or SPOT service contract is still running. You keep it with the outdoor gear ready to use.

my bad you are right its InReach that uses the Iridium infrastructure for txt/messaging

Yes InReach uses the Iridium SBD service. I’ve just looked and SPOT has new coverage maps and improved coverage so its service should be more reliable and quicker. The killer on all these devices is the cost to use them gets big quickly. Cost to buy, monthly service plans, excess message charges etc.

For me, being a technology junky, when I saw the 1st data modems for Iridum being offered I just had to have one. That’s why I have spotting concoction built from an Iridium modem and a Raspberry Pi to drive it used in conjunction with my mobile phone. If I was starting now I’d buy an InReach. You can use an InReach unit to send spots to SOTAwatch as well. It should be feasible to support SPOT-X but nobody who has one has asked me to support it.

Thanks very much to all who responded, including the prolific and always erudite MM0FMF! Some thoughts:

  • I should have been a bit more specific about the differences in the technologies, and I should not have lumped InReach and SPOT into the category of PLB. When I commented that I had not seen data on the different technologies, what I meant to say was that I had not seen numeric data regarding the reliability of InReach and Spot for distress signalling so as to compare them to true PLBs. I did not mean to impugn the reliability of true PLBs. Mea culpa and thanks to all who filled in my blanks.

  • I hoped someone could direct me to a resource I have not found online: some kind of numeric data on the experience with SPOT and InReach. Failing that, I was gratified to receive some real-world experience on the reliability of those two systems. Thanks to those who shared their experiences.

  • At present, it appears that if you want to be sure rescuers know exactly where to find you, a PLB is the device of choice. If you want to be able to text from the back country, I guess the InReach using the Iridium network is a good choice. And if you just want to leave electronic breadcrumbs on a map, SPOT will do. But SPOT or InReach will not provide the assurance of rescue location signal that a PLB will, despite what the vendors may imply.

I have seen at least one website of a backcountry hiker (not a SOTA op) who carries both a PLB and an InReach device so he has both texting and distress calling available to him. Looks like that currently remains the only way to ensure having both functions.

73, Scott

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I have used SPOT for SOTA these last two years. Just the locator beacon which sends position/time locations as I walk and I also send “all OK” messages to my wife from time to time (e.g. at the summit, when back at the car, etc). I have found two things about using it. 1) Positional accuracy is good, less than 10 meters error 2) Does not work well under forest canopy. Needs an open sky. How open is the question…it always works on mountaintops with no trees. When I send a message from a location that “looks” like it should work (say overhead clear plus or minus 30 degrees or so) not all the messages will get through This is kind of annoying so I will send messages more frequently if I guess that I need to! In case of emergency I would need an open sky and might have to crawl (if injured) somewhere to get out from under the trees. That being said I am paying $400 for 2 years service which is $17 per month which is good value to me. 73 Hal N6JZT

So, keep in mind I am approaching this response more from the perspective of a US Based, SAR ops individual, and hoping that this hits on some of your last points. Oddly I’ve been working on a blog write up on exactly this topic for the past two years. InReach vs Spot, vs HAM. As you call out though it’s hard to find data other then customer reviews and antecdotal evidence. At the end of the day I think I refer to the PLB option as a “solution to a problem that does not actually exist” especially if you are already a HAM. It is true that there are some areas “out there” that not even APRS is an option, and PLB does make sense, but I would say for the large majority of the SOTA outings we go on ham bands will have you covered. I have no clue if the results would be remotely similar on other parts of the planet, and advise you to reach out to those on the ground in those areas. I tend to stick to high traffic areas when activating internationally.

TLDR: it’s a cool tool, it can be an expensive one, it serves a purpose, but as a HAM you already have the great majority of the options a PLB offers you.

Since you called out having the option to communicate with a responding SAR team via the TXT option, you already have that as a HAM. Your HT is that method. Most SAR teams outside my local coverage area I have interacted with do actually have Ham Ops on the team, even if they are there just to provide technical support and some jurisdictions do monitor local repeaters and even citizens band (big in areas with jeep trails). From what I have seen in the W6 and W7N scene SAR teams would rather have voice comms with the subject instead of hoping the txt gets received and responded to. (which btw, if you are on a SAR team elsewhere in the US please reach out to me on DM, I do have questions for you). Looking at your activation history, I would check out GEMA or NCEM or any statewide emergency services organization website, or just reach out to the local ARES contacts as well to see what may be there.

I have heard of folks who actually include their callsign in their outbound message on their PLB which in that case, the responding teams may try and reach out to you on Simplex. If the approaching team is a hasty team they would rather have voice comms with you so they can start relaying back to command post what other assets are going to be needed to support your situation. (Much faster information flow)
National Interoperability (United States) Scanner Frequencies and Radio Frequency Reference. Is the list of national emergency use frequencies VTAC11 is used…a lot… While I do not personally endorse this, if you have a Baofeng, you already are open on those frequencies. YMMV, but they might be willing to communicate with you on that frequency. I’ve had the “and what if I come up on a subject, or I am a subject in the BC and 911 is not an option” with my SAR coordinator. The response was basically “get on local county DISPATCH, and avoid the ham bands if you can, however if you have to use the ham bands do it”.

I get the tech fun factor and PLBs are a fun new toy/tool, but that said it’s just one more tool in the tool shed. In the mentioned blog write up it literally comes down to your level of comfort (and the level of comfort of those you leave at home) and the fact that a HAM license is 15.00 for 10 years, and somewhere between 300-500 dollars for an HT that includes the features that would put you on par with a PLB (APRS). The PLB unit runs about that same amount, unless you roll your own, and then as Andy called out the cost to use over time can reach to the sky pretty quickly. So do pay attention to your plan/usage.

It does also boil down to the comfort of those you are leaving at home and one other thing to consider there is having and communicating a proper plan with them and I did teach my wife how to follow me on APRS. I always print out a smaller scale map that includes my intended route, potential timing (research the münter method if this is new to you) and other specifics like my call sign, and frequencies I will be monitoring while out there. My general rule is “I’ll be home, or will check in by such and such time, if i’ve not by bed time then start the troops”. If the home front had to call 911, they have all the information responding services needs to get to me quickly assuming I stuck to my original plan.

It’s a fun topic for sure, and everyone has their opinion, and I continue to be surprised by all the hams that resort to PLBs given that we have the tech in our hand already, beyond the “it’s cool fun tech that I want to play with from a tech nerd perspective”

My research on this topic brought me to my purchase of a “true” PLB. I have read of many stories of SPOT signals that took hours to get out or didn’t get out at all. My choice was the McMurdo Fast Find 220. It has a 6 year battery life and a price of $210. There are no monthly or yearly fees of any kind.

And I wrote a blog post on that back in 2011. People often focus on incidents that require evacuation, but there are a lot more where communication could make things safer or easier. Maybe a mild sprain and you self-evacuate to a different trailhead. Sure would be great to contact somebody and get a ride.


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" * Reporting a wildfire"
This is one where from my past where having the radio would’ve been good…I could’ve dialed around to find the fire crews in the field to hear/get the beta…is this fire close to me, do I need to deviate and self evac, or can I continue on my trek etc…
Great write up…maybe I’ll delete mine and link to yours…at a minimum I’ll just declare “yet another write up, and here is another perspecitve” etc…

Go ahead and post your own thoughts. The more the merrier. My post has about 200 views in five years, so it hasn’t exactly cornered the market.

It is time to update my post anyway. That was before I got my KX3.


I am another person who carries both an inreach and a PLB. My PLB lives in my zippered pants pocket for the duration. The Inreach is on the pack tether and there incase something happens at home and we need to be summoned out early or more likely we need to make contact saying we are late or the plans changed in the field. Plus if your really stuck for contacts getting that initial sotawatch spot out is always awesome :slight_smile:

IMO definitely room for both but if I had to choose one it would be a PLB. At the end of the day I would much rather rely on a system that is going to run redundant mechanisms for location detection rather than relying on a GNSS reading. My inreach sitting on the window sill overnight thought it covered the whole suburb!

Spot works fine for me at 57N