ACR PLB vs InReach

[BPLwiia]

I’ve been doing some reading and trying to understand transmission capability and reliability of COSPAS-SARSAT vs. private GEOS/Iridium/Globalstar.  I’m not interested in discussing other capabilities, such as messaging.

COSPAS-SARSAT has a 406 MHz and has 121.5 MHz homing capability.  How does this compare to the private satellite systems? Is one able to transmit better under the canopy of trees or in foul weather conditions? Is there any difference in either performance or reliability between them?

 

 

 

[Jenny A]

It might boil down to who you mistrust the least:  big government or large for-profit corporations?  That is a simplistic answer, but that’s how I view the choice.

[Rex Sanders]

Iridium transmit and receive: 1616-1626.5 MHz
Globalstar transmit: 1610.73-1620.57 MHz
Globalstar receive: 2484.39-2499.15 MHz

Those are a lot higher than the 406 MHz signal PLBs send to COSPAS-SARSAT satellites. In general, lower frequencies require longer antennas but penetrate tree canopies, heavy rain, and snow better. But there are a lot of other variables involved.

The COSPAS-SARSAT 121.5 MHz homing frequency is good for a few miles; it’s typically used during aircraft searches when a GPS position isn’t available or flaky.

In theory, due to the frequencies used, and multiple redundant design features, PLBs using COSPAS-SARSAT should be much more reliable than SPOT or inReach for SOS messages.

There are many, many other differences between COSPAS-SARSAT and private systems; the devices supported on those systems; and the back-end infrastructure. It all needs to work seamlessly when you need help.

In the real world, taking everything into account, I’d rank COSPAS-SARSAT as #1 in SOS reliability; Iridium as a close #2; and Globalstar as a distant #3.

But statements like that can start flame wars on BPL.

Lots of background on satellite systems:
https://backpackinglight.com/satellite_communications_sotmr_part1/

NOAA’s SARSAT web site is pretty good at explaining COSPAS-SARSAT:
http://www.sarsat.noaa.gov

Note: PLB “I’m OK” messages are actually single-transmission test messages with a lower probability of getting through. I wouldn’t depend on them to keep people at home happy, and each PLB will transmit a relatively small number of those messages before you need to replace the expensive battery or entire unit.

Hope this helps.

— Rex

[BPLwiia]

Great resources Rex, thanks. As I read through them it would appear that the COSPAS-SARSAT uses three satellite groups – low earth (LEOSAR), geostationary (GEOSAR) and are now using the next generation of satellites the medium altitude (MEOSAR) which near instantaneous location.

http://www.sarsat.noaa.gov/satellites1.html

InReach uses the Iridium satellite system. Does it have access to the new GEOSTAR satellites?

 

[Brad Rogers]

I would think that the PLB would be the most reliable, but as you know there are advantages to being able to communicate with rescuers.

I have been a part of a couple of airlifts, ran across another, and have been in a couple of other instances where communication deemed quite useful.

The fist instance was where we ran across another hiker and his wife who was having heart arrhythmia. I didn’t have a communication device but the guy I was hiking with had a SPOT (I think it was a first generation – which was probably all that was out then). He was reluctant to use the SOS as it would alert his family that there was an emergency and they would think the worst for him (it would have been helpful to have 2-way communication). He also had a cell phone but no signal – however I was able to take his cell phone and hike to the top of the highest nearby mountain and got signal and they airlifted him out.

The second time I was with a hiker who twisted his knee in talus and had an inreach and a satellite phone and we were able to get him airlifted out. We ended up using the Sat phone but could have used the SOS on the inreach. We did use the inreach to communicate with the NPS and help coordinate his rescue.

In Alaska last year, my Dad was hiking with me and hurt his leg and we were able to communicate with the bush pilot to come pick him up at the midway point (which we knew was a potential bail out point) while I finished the trip. This wasn’t a rescue, and we didn’t use SOS, but if we had a PLB or Spot we would have been forced to either push the SOS or do nothing at all.

When I was in WRR in 2016 they were airlifting out a rock climber that had fallen off Pangora(sp). I don’t know all the details, but when I talked to a member of his climbing party, they said they coordinated the rescue with an inreach.

In Alaska in 2015 we were able to communicate with the bush pilot where he needed to change our pickup time up considerably. If we hadn’t been able to communicate with him we might not have had everything ready for pickup.

The Inreach vitual keyboard is slow and tedious (many times I don’t carry a phone though I have often entertained the idea of taking my phone instead of my camera), but it works in a pinch. I always set up the pre-programed messages prior to a big trip and use them to “check in” every day or two and only use the keyboard if there is a emergency or major deviation to the plan, which isn’t often. Carrying the inreach makes my wife and my parents feel better about me on trips and I figure with me being a husband and father that taking something is the responsible thing for me to do.

[BPLwiia]

There’s no question there are tangential issues related to choosing a device. Right now, I’m trying to ferret out just the transmission aspect of having such a device. I don’t want to clutter the discussion on other issues which can be addressed in another thread.

I think most people assume that all devices (PLB, InReach, SPOT, etc) send a signal and there’s no difference between them. I’m trying to understand if a PBL, using the COSPAS-SARSAT system, has any technical advantage to it either in speed or reliability of transmission.

[BlackHatGuy]

You might find this useful/interesting. From the site: Iridium® handheld device users will benefit from an even more powerful and reliable enhanced personal communications network.

[John S.]

I believe the PLB does have technical advantages in reliability.

1. Power of signal transmission- most PLB’s seem to transmit at 5 watts. Garmin won’t tell you what their transmission strength is…it won’t be 5 watts I bet.
2. Battery readiness- Garmins may not have as much battery power if you are using it for other stuff- debatable
3. Satellite system
4. Signal receiving authority

[BlackHatGuy]

Transmission of the Delorme inReach products was 1.6 watts. No idea if Garmin upped that, but doubtful they did.

[BPLwiia]

“You might find this useful/interesting. From the site: Iridium® handheld device users will benefit from an even more powerful and reliable enhanced personal communications network”

I saw that and Iridium talks only about changes to the low-orbit satellites. No mention at all about having or using medium-altitude satellites so I would assume they will not be using those. When you read the NOAA Search and Rescue Satellite Aided Tracking, it sounds to me they are promoting the medium altitude satellites as the  wave of the future with instantaneous location.

http://www.sarsat.noaa.gov/satellites1.html

[BlackHatGuy]

Some folks believe that the Garmin devices are using the Iridium 9603 chip, if so, here’s info on that.

[Rex Sanders]

Watts of transmission power is … sort of important, but it depends on so many other things, like distance to satellites, antenna design on the device and the satellites, and more. See “Factors affecting signal strength” in https://backpackinglight.com/satellite_communications_sotmr_part1/ for an incomplete list.

COSPAS-SARSAT satellites fly at a mixture of elevations, including geostationary orbits roughly 50 times higher than low-earth birds, so in some ways PLBs need the extra power.

COSPAS-SARSAT Medium Earth Orbit (MEO) satellites have certain advantages over the LEO and GEO satellites they currently use, including near-instant locations by Doppler location processing – the old system depended on irregular LEO satellite passes for that. But if your PLB has a good GPS fix and can see a GEO satellite, Doppler location processing isn’t really necessary, so maybe MEOSAR is not quite as revolutionary as NOAA would have you believe.

Iridium and Globalstar don’t plan to use MEO or GEO satellites – but they don’t need to. Iridium in particular has good global coverage with LEO satellites.

We won’t know the impact of Iridium NEXT satellites on existing devices like the inReach until they activate that network. And taking full advantage of NEXT might require new devices.

The inReach SE repeatedly warns when the battery starts getting too low to ensure SOS functions. Don’t know about other devices.

It’s not clear that different Iridium modems / chip sets have much impact on reliability – each generation mostly shrinks the size.

In my mind, the big advantage for PLB reliability is redundancy: several independent satellite systems in different orbits, fixing your rough position using Doppler location processing, sending a more precise GPS position when available, plus a local homing signal. Secondary advantages include lower frequencies and higher transmission power.

In my experience, the inReach SE gets routine messages out under very challenging settings – e.g. deep canyons with continuous redwood forests.

If you want the absolute most reliable way to send an SOS – carry a PLB. But for many people, there are other considerations.

And always leave a written (as in paper) trip itinerary with a reliable contact, including instructions on when to call search and rescue. All electronic devices can fail.

— Rex

[BlackHatGuy]

Thanks Rex, lots of great info from you in this thread.

[Rex Sanders]

One more reliability advantage for PLBs: Buy it, register it, throw it in your pack, and forget about it for 7-10 years.

No need to worry about battery charging, subscriptions, expired passwords or credit cards, Bluetooth pairing, and on and on with more complex devices.

Not related to signal reliability, but still important.

— Rex

[BPLwiia]

What I really like about this thread is the discussion regarding transmission issues. All too often, the discussion centers around features of the various devices which, at least to me, is secondary to the principal purpose which is to transmit and do so quickly, accurately, and reliably.

[Seth R]

I think it really depends on where you hike. I trust both devices to function as advertised.

I live in the east and almost always have the ability to squeeze out a text no matter where I am in New England, even the middle of nowhere Maine. PLB is my choice here. Shortly I am heading to Wyoming for a week of solo backpacking. InReach SE will be my device. I would rather just pay up front for a device than have to be in a subscription plan.

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