"Live testing" is discouraged: https://www.sarsat.noaa.gov/emergency_beacon-testing/

I dont own this but it is pretty much the standard: https://www.acrartex.com/products/resqlink-400/

These devices require a new battery every few years and that service includes a test done by the manufacturer. There is also a self test button on the device which does not send a message to the satellites.

If you really feel the need to send test messages into space, they do support that but then you need a subscription (https://www.acrartex.com/406link/). At that point you may as well buy a different device which has 2 way messaging included in the subscription. PLB users generally do trust that their devices work the first time they're used for real, and this trust is backed up by a lot of real world use.

>PLB users generally do trust that their devices work the first time they're used for real, and this trust is backed up by a lot of real world use.

Although they are not foolproof. See for example the story of Kate Matrosova. [1] Basically, mountain shadows made the location readings erratic which, in combination with extremely bad weather, meant rescuers couldn't find her.

[1] https://www3.bostonglobe.com/metro/2015/02/21/the-young-woma...

Note that http://www.catskillmountaineer.com/reviews-winterhikingKM.ht... for example says Kate did not have a PLB, but only a SPOT (one of the many commercial products in this space)

PLBs are tested down to -40° so it might have stayed working for longer as the weather got worse. It is of course impossible to say if Kate might have survived under other circumstances except that (not very interestingly) if she's decided the weather was too awful and aborted she'd almost certainly live.

It's been a while since I read the book on this. I'm not sure if it got into the exact equipment or not. Certainly if SAR had an accurate fix from the beginning there would have been at least some hope for a rescue.

The book was interesting mostly for all the SAR detail. The accident, sadly, was mostly in the category of--however fit and well-equipped you are--don't try to beat a very bad incoming storm on an exposed ridge line in the middle of winter. If she had turned around at Madison Hut or wherever she'd have been fine.

I only meant that the devices, if properly maintained, can be trusted to do their job as best they can and not say "PC LOAD LETTER" and expect you to troubleshoot it. A successful rescue is never guaranteed.

Those of us who are programmers usually default to "If it's not tested end to end, it won't work," and that is the sentiment I was responding to.

Kate Matrosova was using SPOT, not a PLB.

Actual PLBs (not SPOT) have a backup strategy in the event the GPS signal is obscured by mountains.

If the device can't get a reliable GPS fix, the satellites will resort to measuring doppler shift as they pass overhead to locate the transmitter. It's slower (takes several passes of the satellite, so we're talking hours) and less accurate, but it will get rescuers to the general direction.

From there, PLB devices also transmit a low-power homing signal on 121.5 MHz (the aviation distress frequency) that SAR teams can locate using radio direction-finding equipment.

Thanks for the info. Although, in general, I assume a device that allows you to have two-way communications with SAR is preferable even if a PLB might have been better in this ultimately fatal situation.

Yes, two-way communication is a huge benefit since you can explain the problem and the responders can give advice in addition to ETAs.

However, a device like the Garmin inReach requires an active subscription for the SOS to work. If there's a glitch with your credit card and the service becomes inactive while you're on travels, it might not work.

Another difference is that an inReach SOS message goes to the Garmin-run https://www.iercc.com/en-US/about/ rescue coordination center who will the relay to rescue services.

Whereas a PLB or EPIRB communicate with the Cospas-Sarsat system and is handled directly by government rescue agencies (https://www.sarsat.noaa.gov/mission-control-center). While the Garmin service works great, I have more trust in the USMCC being always responsive than any private company.

So the best advise is to have both. I have an EPIRB (for boating) and a couple PLBs in addition the the Garmin inReach. I use the inReach for casual messaging but if I ever have a real emergency I'll activate the PLB and EPIRB first and only afterwards start trying to message via the Garmin.

My understanding is that SARSAT is the only option that has satellites in orbits above LEO, and thus generally better coverage. So if it's down to one thing only, I'd pick the PLB just on the basis that, in a serious emergency, it's more important for help to come at all.

For PLB I am pretty sure it's universal. For messengers (like the inreach), find out what people in your geo use between iridium or SPOT because satellite coverage can vary. For example, I have heard that in alaska SPOT's only geostationary sat is really low on the southern horizon and anything that breaks LOS will interfere with the device.

For PLB specifically you cannot test them. Once you activate them, they continually broadcast and cannot be canceled except by destroying the device. For messengers, they hook up to a web service and you can send messages to personal email or SMS via the sat network as your test.

> I have heard that in alaska SPOT's only geostationary sat is really low on the southern horizon and anything that breaks LOS will interfere with the device.

Any geostationary sat would be low on the southern horizon in Alaska. That's just how geostationary orbits work, they are over the equator. Though pretty high above (35.000km/22.000mi). So it's still visible there but yeah you need a clear view of the southern horizon.

But Globalstar which runs the service for SPOT only has low earth orbit sats which are definitely not geostationary. They're only at a few hundred kilometers.

However it could very well be that their orbits are aligned so that they are always pretty low to the south from Alaska, yes.

This is a quite good writeup with some recommendations: https://www.greenbelly.co/pages/best-personal-locator-beacon...

And answers your question: "Each device has a test mode that will communicate with the SARSAT satellite network without sending an alert."

> Each device has a test mode that will communicate with the SARSAT satellite network without sending an alert.

That explanation is factually incorrect, then. There currently is no "test" flag, nor is there the required infrastructure to check if your test alert went through:

https://www.sarsat.noaa.gov/emergency_beacon-testing/

So this "self-test" feature can't be communicating with actual satellites. No idea what it actually does, but it's definitely not an end-to-end test.

Perhaps the emergency communication with satellites is a handshake, and the "test" mode for the beacons simply doesn't complete the handshake?

Possibly (the page I linked even mentions a "test" type of signal), but given that there is no return link for most PLBs and no "list of recent successfully received test transmissions" online, I don't understand how one would actually verify success.

This policy document mentions that the "self-test" feature actually does not communicate with satellites at all, and also mentions a "test frame" that is discarded by satellites, as well as a "test protocol" that is forwarded by satellites, but discarded by the ground segment: https://www.sarsat.noaa.gov/wp-content/uploads/POL-MCC-051-v...

So it seems like both the "self-test" and the "test frame" don't tell you a lot about how well your beacon would work in case of an actual emergency (unless you have equipment that can receive and interpret that signal), and live testing involves a lot of paperwork.