2-way satcomm vs. PLB?

I am planning to upgrade my GPS from a wrist-based Garmin Foretrex 401 to a handheld (either the 66st or 66i). I’m also planning to add some type of personal locator capability, e.g., the ACR RescueME PLB1.

The vast majority of my activations are solo, and I’m frequently in remote areas without cell service. Would I be better served with a separate PLB device or am I overlooking the value in also having 2 way comm?

My spouse doesn’t need real-time breadcrumbs to track my progress, but might be freaked out if he doesn’t hear from me for more than a day. A month ago I broke my ankle en route to an activation. Fortunately I remained ambulatory (actually thought it was just a bad sprain, and kept activating all week ;-)) so not an ER, but maybe a situation where non-ER messages would be helpful.

The 66i rolls nav, satcomm and SOS messaging into one unit (subscription required to use comm and SOS). The 66st is just nav, and the PLB1 only sends a one way ER message with GPS info (no subscription required).

Thanks for any guidance you can provide.

73 Paula k9ir


You can send SOTA spots with any Garmin InReach device.

Hello Paula,
As you’ve recognized, sometimes things fail or get broken at the worst possible time. (like your commo widget is between you and the rock that you fall on)
The old military saw for rescue stuff is: "two is one; one is none"
For that reason, Kay and I carry an ACR beacon AND a Garmin In-Reach. (not to mention the HF rig)
All Best, Ken

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My wife and I each carry the ACR ResQlink. No subscription fee, and more reliable (transmits on different freq than Garmin and at higher watts). Talking with local rescue crew, the commercial satellite communications like the /GarminSpot or other two way devices frequently don’t work in the deep valleys of the Olympics, or at are spotty, or they batteries die when the are really needed. I am a flight nurse, and even in the air our Spot and our other $30,000 Sat phone are too often unreliable.I can usually get out with APRS (from summits) if my cell doesn’t work, and I also have my MTR3B. If I needed to have frequent 2 way comms and APRS didn’t work, I might get a Garmin, but would still carry the PLB too. I am also setting up my parents with a $50 HF QXC transceiver. They have tech licenses, but don’t know Morse code, so I am hoping the decoder and preprogrammed message function will allow them to have 40 and 80 m NVIS comms with me if I am camped in a deep valley

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Also, keep in mind that anything touch screen (LCD, liquid crystal display ) is likely to freeze and not work in the cold. I carry a non touch screen GPS as a backup to my cell phone when ski mountaineering.

If the device is for safety of life then you need a stand alone PLB where the batteries are not compromised by any other activities that may occur on a combined device.
Last week end I was on a NSW Police led SAREX. They were able to confirm that the Garmin InReach device’s worked but had latenceis that comprimised their usability for the use they were wanting them for.


Tnx to all for the great info. Sounds like a PLB is advisable because of its reliability in all situations.

A GPS/nav device that includes 2 way comm would be a nice backup to ER comm with the understanding that the LEO sats the Iridium system uses, while worldwide, may not be accessible for messaging in certain environments. I would use the 66i or 66st primarily for navigation, but like that the 66i allows for non-ER comm.

FYI all of the 66 series of GPS from Garmin do not have touch screens; agreed that would be a deal breaker, but Garmin wisely stayed with buttons.

It’s difficult to find info on device transmit power. I found this reference, which contains an interesting discussion of TX power vs. type of sats used: https://www.reddit.com/r/Ultralight/comments/a3ix2d/submission_power_of_inreach_and_mini/

73 Paula k9ir

This, this a million times.

I have standard Iridium short message device I use for spotting when out of cell coverage. Same frequencies and operation modes as an inReach device and almost as expensive to use! Typically I see a round trip latency of around 25seconds from sending a spot at the device to my own servers processing the received message for posting on SOTAwatch. It’s gone from my remote device to a satellite, around the satellite network, to an earth station in the US Midwest, to Portsmouth UK, to my server in Iceland. Then I post it on SOTAwatch.

It’s 1.6GHz and uses a small patch antenna. It doesn’t work through foliage, in fact low density overhead branches and trees will kill its performance dead. It will hear the satellite network but they wont hear you.

Doesn’t matter. The Iridium uplink signal is very, very bursty and only sent when invited by the satellite network. My modem is powered from a 5V 95mA max supply. It can send 1 maximum length message (300bytes + header/framing) every 30 seconds. I’ll will flatten my bank account with the cost before Iit will flatten the small battery that powers it.

To recap:
Life depends on device: buy a PLB / EPIRB and register it.
Want to send messages and/or spot for SOTA when portable with no cell coverage, no APRS and no CW skimmers: use an Iridium device.


I am persuaded ;-). A RescueME PLB1 it will be.

The new GPS would be primarily for nav. The comm field performance of Garmin devices using Iridium doesn’t seem to be as great as I’d read elsewhere. Ability to self-spot when all other options are unavailable doesn’t occur often enough for me to justify a more expensive device plus subscription (especially if it takes so little to kill performance). So the 66st may make more sense (IOW - back to the original plan!).

Thanks again for the comments and info from real-life field experience.

73 Paula k9ir

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I would defer to all things SAR to Compton, as he has said when life is as stake is PLB all the way.

For VK ops most of your national parks type offices will rent for a small fee, if not lend you for free ( with deposit). in VK1 Namadgi Visitor’s Centre rents for about 5 bucks.

Having nerded out one night and actually read the MOU between inreach etc and the Australian Maritime Safety Authority ( the VK authority for commencing most SARs) there is a lot of person to person contacts " in reach calls AMSA" etc PLB all the way.

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