What frequency band are you using? ISM is the only one that permits store-and-forward / automatic operation, as the gotenna people found.

You say a few miles per node - I am having trouble seeing how that's possible without elevating all the nodes

Oh yes, line of sight makes a big difference (also working as mesh helps for forwarding packets). Also we use a very high spreading factor so the bit rate becomes super low (with lots of chirps)

He's gotta be assuming the nodes have clear line of sight and fresnel zone. The maximum distance for the link budget in a perfect situation. In practice it probably cuts off at the nearest rise in the ground or depression.

But they're still cool and I still want some for non-hiking applications. With the very low power idle and low cost they could be set up with solar panels in the tops of trees or in similar high height above terrain positions.

915 MHz goes a lot farther than 2.4 GHz.

At very low bit rates you need very little SNR.

There is probably very low noise out in hiking environments.

Yes, attenuation due to terrain is going to be a killer, but my experience with non line of sight 900 MHz links blasting through trees leads me to believe it would be workable for low bit rate data between a series of hikers along the same trail.

It is sending only location and text messages so intermittent link status or re-tries due to temporarily terrain/foliage obstructions will not cause degradation in service that you would experience trying to watch netflix over this mesh.

You're wrong. It's a mistake to treat terrain and foliage as the same thing. I have extensive experience with 3 completely different, narrowband and wideband, 902-928 MHz radio data systems as well as just playing around in the range with my software defined radios (hackrf, rtlsdr, etc).

902-928 has almost no advantage over 2.4 GHz when it comes to line of sight issues with terrain. In fact, it's more problematic due to the increased size of the fresnel zone. Sure, it does better through trees but a slight rise of ground is just as much of a problem for 915 and 2400. The freq here isn't helping much. It's the chirp and LORA modulation helping the link budget. But no line of sight is no line of sight.

It sounds like you agree 900 MHz will be much better than 2.4 GHz in this non line of sight application so long as the obstructions are trees and foliage and not terrain.

I would expect to be able to send a few bytes between two stations maybe 400m apart through non-line of sight forest with 900 MHz and both stations at the same elevation. Certainly the grandparent quoting miles would be for mountain top to mountain top.

This is all assuming they use antennas that are optimized for the application. If they use a “chip” antenna, performance will suck.

the video on their web page shows an external antenna, looks like a dipole.

This stack overflow question has some nice pictures of the LoRa "chirps". They use rising/falling frequency modulation to allow operation at startlingly low signal to noise ratios.

(Also, the hardware they're using is fairly generic, and pretty much all the vendors selling them offer them in 915/920MHz and also 868MHz and 433MHz variants. I've seen claims of over 10km range with 433MHz LoRa gear without special antennas or clear line-of-sight...)

Just noticed I'd left out the link to the SO question I mentioned (and it's too long ago to let me edit that post):

https://electronics.stackexchange.com/questions/278192/under...

LoRa has very peculiar modulation scheme that in the end is not CDMA-ish spread spectrum but an interesting way how to extend straight FSK into spread spectrum modulation with respectable processing gain and interference rejection.

I recall reading that part of the design was so that not only was it good at rejecting interference, but that it also caused little interference to other users of the spectrum.

If someone else's ISM radio is using a specific frequency (perhaps with CDMA or TDMA), a "chirp" that's spears over about a hundred kHz and -20db or so down in the noise is unlikely to bother them, but is quite useable/reliable for the LORA gear to detect.

Not sure why this was downvoted, it's exactly correct.

I used to get about a mile on 900MHz Ricochet radios, one of which was sitting on a chair in the living room, the other of which was sitting on the passenger seat of my car. Around a mile, the usable data rate would fall below 4800bps, and my NMEA packets would stop going through.

I find it entirely believable that a lower data-rate modulation could get better range than that, even on less power and worse antennas.

And you can do a LOT with antennas on 900MHz.

Their site says using 915mhz, and the radios they recommend are all LoRa devices, so that's probably the best way of evaluating distance performance.

I actually fly FPV drones and it’s amazing how far I can go and what obstacles I can penetrate with my 915mhz 2W control link with very usable latency (good antennas makes a huge difference as mentioned by others). 2-5km through thick city buildings etc at times.

Can you use MURS for this? Or potentially GMRS if the operators are licensed?

Hmm... I'm pretty sure MURS allows for this type of traffic as of the last rules revision and would be ideal for this use with the higher power allowance, but MURS is a USA only thing so that kinda limits you if the goal is something that works all around the world.

OP is also talking about using off the shelf LoRa boards and their project is more about the software, so they are stuck with the bands available on the commercial LoRa transceivers those boards use.

Is there anything I, as a sysadmin-by-experience, can do to help out?

I don't have any relevant skills for radio or SDR stuff, but I'd love to mess around with it for a couple of hours a week.

I'm not involved with the project, but I think you can probably get this running. The hardware is cheap, the install instructions are pretty straightforward, and if you know which end of a USB cable is which, you'll be able to bumble through.

Keep notes as you do, and that can feed directly into improving the documentation to be more noob-friendly.

You'll find more ways to get involved from there, including just using and sharing the project with friends.

I'm adding myself to the Gitter channel and will hook up a radio to my home office Raspberry Pi. I'm excited to be a part of this! :)

Thanks for the encouragement, by the way. I really appreciate that.

yep - what myself248 said. and yes, if you have questions just ask on the gitter channel and we'll all work together to help.

I just want to say: you seem like an awesome person. Keep being awesome!

Radio amateurs might be some suitable beta testers for you. It being an open source radio system fits right into the mission and spirit of amateur radio.

However, I'll take the cynical route and say mesh radios, for the general public, are still not very popular. Gotenna and Beartooth, among others appear to be common and popular, and highly reviewed, but in my hikes and ski trips, I haven't seen or heard from a single one. I've seen FAR more basic FRS radios, and SPOT satellite messengers.

I'm one of those amateurs.

Gotenna is stupid expensive. And spot is pretty evil (or at least the instances I've encountered it).

I think what most of the public expects from a radio device is PTT audio. Which isn't going to work with these low bitrate lora devices. I think if they got conditioned to some of this form factor, it would catch on a lot better.

FRS radios and SPOT are also awesome.

The LORA stuff is pretty cool in that the radio stack (if you can call it so, it's super little code) is open source and you can get complete modules with an STM32 and the associated LoRa radio circuitry and just add power and an antenna.

This is so cool... I spent six months doing research on a routing layer for mesh Android devices (using Bluetooth and Wifi). This would probably make a lot of what I originally tried out a lot easier.

Edit: The issue was making a jump from a local cluster to another cluster far away as local messaging was easy but the further out, the harder it became to maintain connectivity since the amount of devices entering and leaving a mesh became a factor. We actually thought of using amateur radio (to basically allow you to extend the range using them for transfer)

My solution for this kind of thing is to support a router that connects to the internet. Then on the internet side run a DHT so all the internet routers/gateways can find each other. Each router would keep track of the devices they have seen recently, and publish them to a DHT. Much how running a bittorrent client for a particular torrent publishes that fact to the DHT so anyone on the planet can find peers of that torrent.

So if Bob at a ski resort in Colorado want to message someone in Germany his message would propagate around the mesh until a gateway noticed it was for a client that hasn't ever been seen by that gateway. The gateway/router would do a DHT lookup, and would find a router in Germany had seen that user recently and forward the message there. Next time that router heard (directly or indirectly) that the recipient was online it would forward it (directly or through store and forward) to the user. Sure this process might take minutes, but generally it would still be useful.

Imagine an island like Haiti or Puerto Rico is hit by a storm and only one in 5000 people has a cell signal or sat uplink. Add a mesh and just a few uplinks for the whole island and important communications could get through. Maybe even putting a sat uplink on a car that could drive around and allow messages in/out even just once a day could be quite valuable. This of course needs to be combined with store/forward messages and the other various delay tolerant network features.

Seems much more useful than using HF radios to scan the planet for open Ham <-> email gateways. I was rather amused to hear that to communicate across Puerto Rico they often ended up sending messages through an email gateway they could reach in Italy... just to get messages across the island.

The Synapse mesh radios pretty much do this, seamlessly linking RF meshes with an IP bridge.

https://developer.synapse-wireless.com/modules/index.html

One of the other things we have been doing with Serval in the Mesh Extender devices is making it possible to connect external radios, including HF radios from Codan and Barrett, for really long range inter-cluster communications.

That's awesome, this kind of thing was the first idea I had when I saw the LoRa radios, but was far too lazy to start doing :p still have the hardware at home; ill see if I can install it later.

awesome! we'd love to have you join us ;-)

Yeah I'm interested. I've been building something like this solo, but don't have the skill set to write a mobile app to go with it. I've got the spare parts to make a dozen widgets with a comparable feature set, but family life is keeping me from doing much of it. I know a guy in disaster response who would love to get his hands on a working prototype set to geek out over.

Looks awesome! Downloading the app, going to try it out on my T-BEAM that's been sitting dusty, and will definitely have an opportunity to test it soon.