SatComm with SPOT-X and or Garmin inReach

[axlesandantennas]

Hey all.

I'm a SPOT-X user and am very happy with the system as a whole. But I do have a question about SPOT vs inReach: Do any of you have actual experience using both? As happy as I am with the SPOT-X, I am a long LONG time Garmin user and am looking to switch. I personally do not venture out of the US anymore, so world wide coverage is not something that I need.

I understand the SPOT / Globalstar system versus the Iridum that inReach uses and the fact that Iridum runs at least twice as many satallites as Globastar. I've been in some fairly deep valleys and never had a message not go though.

Anyway, what are your thoughts?

 

[DaveInDenver]

Don't read too much into the difference of the 66 satellite constellation of Iridium verses 48 of Globalstar. By deciding not to cover beyond 70° (e.g. the Earth's poles) Globalstar doesn't need as many satellites.

The architecture is different. Iridium's satellites are interconnected and communicate with each other while Globalstar's only see the ground stations. Globalstar's design is simpler but limits operation to within satellite sight of their land-based stations. Iridium's constellation is more complex but it's necessary to achieve uninterrupted coverage of the Earth.

Satellites for both pass in and out of view all the time and at any instant you can potentially see multiple satellites depending on your view of the sky. View of the sky is the important part. Being in a deep canyon with a few degrees of sky is going to limit you regardless of system. The actual transit overhead of a particular satellite is going to be a few to maybe ten or so minutes, which is the full 180 degrees horizon to horizon.

So if you put yourself at the bottom of a hole you limit yourself. Imagine looking at aircraft flying over with you looking through a tube. The data bursts are short so standard messages like position or SMS work or not given the window you give yourself. With voice having view of more than one satellite and how hand-offs work is more critical.

Also when you say just U.S. do you mean Lower 48 or all 50? Since Globalstar is just a bent pipe it needs a ground station within the bent pipe's view and they don't have one on Hawaii, so Globalstar doesn't cover Hawaii nor do they AFAIK claim to. They say they cover Alaska but whether it does reliably all over is of some debate.

If SPOT-X is working for you now so will Iridium-based options. The real difference is going to be the user terminal, e.g. your SPOT or InReach device itself. The SPOT-X is probably the worst option since it's lower power and has a less directional antenna. InReach devices have about 3 times the power (1.5 watts vs about 600mW for Globalstar radios).

Then the Tracker uses a patch antenna with gain while SPOT-X (and InReach) use low gain (maybe unity, not sure) helical antennas stubs out of the top that are not nearly sensitive to orientation. You're a ham, you understand that pointing the flat face of a patch at the sky works much better than off its edges and a helix that's omnidirectional requires more power to achieve a similar signal strength. Trackers and InReach should perform about the same, the patch antenna compensating for the lower power.

When you figure the orbits for these satellites is 1,400 km, around 875 miles, that they work at all is danged amazing. I say that as a ham and EE knowing the improbability and SNR involved for a satellite to hear your device at all. I use a SPOT Gen 3 Tracker and like you I've never had it not do what I expected it to do. But I also know a bit more than most users so I have a harness that positions it horizontal as much as possible on my backpack strap and when I do a message it's sitting flat on the ground.

 

[axlesandantennas]

Excellent information DaveInDenver!

US for me = lower 48. Sometime in the future, I would like to add Alaska to that travel map, but it's still a few years off.

Good to go on looking though a tube. This is something I have to explain to my friends all the time when it comes to any kind of satellite system such as Spot, iridium, or just standard GPS. They need to have a clear sky view more than anything else. Typically, when I send a message via SPOT, I will hit send and then sit it, antenna pointing up, on my roof rack for the best sky observation. It does work in the Jeep, but I like the little extra "umph". Additionally, I actually use an external GPS antenna for my Garmin 78. I get wayyyy better reception that way since I like to map out routes and trails for my map products.

That's interesting about the x-mit power of each unit. I had calculated the SPOT at just under 1 watt but at the frequency used, it's all LOS anyway, so power is not quite as important. Knowing that the Garmin has that much more does however make it a little more appealing since that 'should' help when under thicker leaf canopy. Going back to the antenna part though, the Garmin Montana 700i series has a external antenna for iridium that is hitting my "external antenna lust" so it's a big driver for me at this point.

I have until May to make my decision as that is when my subscription is up with SPOT. I will say that I do like the SPOT x with the attached keyboard. It's a little hard to use, but I also don't have to use an iphone to type complex messages.

Decisions decisions!

 

[Rando]

Dave pretty much covered what you need to know - if you are staying in the continental US and only want to send SMS (aka SBD) messages the constellations are fairly equivalent.

I use both professionally - SPOT as an asset tracker and Iridium for data transmission. Personally/recreationally I use an inReach. For your use it would really come down to which handset you prefer. I personally think the Garmin/InReach hardware is much nicer than the SPOT hardware and that doesn't even take into account he newer Garmin devices like the Montana.

A couple of other notes, you really don't need an external antenna with either. My older inReach will track and send tracking points just fine while sitting in a backpack in the back seat of the truck, under the cabover overhang of our Four Wheel Camper. The SPOT Trace can send a track point from inside a building. Sitting in a mount on the dashboard you will be more than OK.

Now totally speculating here - but if you plan on keeping this for a long time, I think Iridium has a much better chance of keeping their constellation alive. With networks like StarLink coming on line, there will be a definite squeeze in the satellite market so it would not surprise me if globalstar didn't make it as it has far less functionality than Iridium.

 

[DaveInDenver]

Globalstar and even Iridium to some extent do seem to face a dilemma with the possibility of ubiquitous Internet such as Starlink. Iridium signed a pretty huge contract to provide service to the government so they're sitting good financially and about a year ago hit a major constellation upgrade milestone. Globalstar for their part solved their constellation issues a few years ago and are in good shape technically. My SPOT renewal is up in a couple of weeks. I'll probably renew for 2021 but I kind of doubt I'd upgrade devices with them. I like the idea of the SPOT-X (or for that matter InReach) but don't want to change out my bike- and backpacking kits to accommodate USB charging. I prefer the AAA battery route personally. So if I was to do anything it would be to go back to a plain PLB for SOS since I use a plain old eTrex GPS receiver for navigation anyway.

 

[Rando]

There is still a niche for Iridium even with Starlink which is handheld and machine-to-machine communications. As of now anyway, Starlink requires a phased array antenna to steer the beam to a satellite, which makes it impractical for handheld devices (phones, inReach, hotspots) and embedded M2M devices that don't need high data rates (think ACARS with MH370). I am just not sure there will space in that niche for 2 or more providers.

 

[DaveInDenver]

The antenna for Starlink makes the assumptive need for high bandwidth, low latency and continuous service as a replacement for terrestrial Internet. The intended markets are different for Iridium and Globalstar.

It's relatively easier to throttle down a big pipe than to scale up a fundamentally limited service that doesn't have the bandwidth to offer. Have to assume that Starlink's plan must anticipate mobile and portable devices and if you don't need gigabit speed for VoIP or IoT so the big steerable pizza boxes might not always be required.

Although there's the problem of putting a higher power 24 GHz transmitter against your head. It's already probably not wise to do with 5G phones that only work at single digit kilometer distances, despite what the FCC says. So handheld Starlink phones are not something likely to exist nor hopefully be adopted from a health standpoint.