Off-Grid Messaging with MeshCore

Ahoy!

Ahoy there makers!

This week I’ve been down a rabbit hole of LoRa mesh networking. It started innocently enough — I was looking at what projects the XIAO is great for, and Meshtastic popped up. One thing led to another, and I ended up standing on the moors above Belmont holding a phone with no SIM card in it, watching the delivery tick appear next to a message it had no right to be able to send.

No wifi. No signal bars. No SIM. So where did the message go?

The answer was sitting in my loft, and it cost about the same as a takeaway. This is the full write-up of that build — and if you want to go deeper, I’ve turned the whole thing into two free courses:

• Off-Grid Messaging with MeshCore — the complete beginner course: two Heltec V3 boards, one repeater, one client, no internet required
• MeshCore Room Servers and Sensors — part two: message stores and sensor nodes that report telemetry across kilometres

What LoRa Trades Away

The boards I used are Heltec WiFi LoRa 32 V3s — LoRa radios. LoRa stands for Long Range, and the way it gets that range is by giving up almost everything else.

Think of it like this: your phone is having a fast conversation in a quiet room. LoRa is shouting one word at a time, very slowly, across a valley. You can’t say much — it’s text only, no pictures, no browsing — but you can be heard a very long way off.

That trade-off is the whole point. A tiny, low-power radio that can push a text message over hills and through weather, using no infrastructure at all.

Why MeshCore?

Most people who’ve heard of this space have heard of Meshtastic. It’s a bigger project, it’s been around a lot longer, and it’s properly good. I went with MeshCore instead, and the reason is how it finds you.

The first message you send goes looking for you — it floods out across the whole network. But the moment it arrives, the reply traces the route back, and the network remembers the way. Everything after that takes the direct road instead of shouting at everyone. It’s a lovely bit of design, and it makes busy networks a lot less noisy.

Two Boards, Two Jobs

Here’s the bit that catches people out: the two boards are identical off the shelf — same board, same price, same everything — but they end up with completely different jobs.

• Companion — this is the one that pairs to your phone over Bluetooth. It’s the node you actually type on.
• Repeater — this one will never send a message of its own again. It just forwards what it hears. That’s not a limitation, that’s the job.

If you flash both boards as repeaters, you’ve built a network with nobody on it. Ask me how I know to warn you about that.

There’s a third role too — a Room Server, which is like a bulletin board that holds messages until you check in. And a fourth — a Sensor node — that reports temperature, battery voltage and even tank levels over the mesh. Those two are exactly what the second course covers.

Flashing the Boards

Flashing takes minutes, not hours. Head to the MeshCore web flasher, plug in a board, pick your hardware, pick the role — Companion on one, Repeater on the other — and pick your region preset.

I’d strongly recommend using the preset rather than hand-typing frequencies and spreading factors from a forum post. Depending which source you trust, they don’t all agree with each other — the EU/UK preset in the flasher handles the detail correctly.

Staying Legal (UK)

Two settings genuinely matter before you go any further:

1. Set the duty cycle to 10%. MeshCore will happily let you run at 100%, and in the UK that’s not legal.
2. The power limit counts your antenna, not just the board. With the stock antenna you’re fine. Stick a big high-gain antenna on it and you can be over the legal limit without touching a single other setting.

And before anyone asks — no, a ham licence doesn’t help you here. This isn’t amateur spectrum. It’s the same ISM band as your doorbell.

The Gotcha That Looks Like a Broken Board

This one had me genuinely puzzled. Two radios, same settings, sitting thirty centimetres apart on the bench — and they would not talk to each other.

Nothing was broken. They just hadn’t introduced themselves yet. MeshCore won’t let you message someone whose encryption key it’s never seen, so one of the nodes has to shout its name first. That’s what the Advert button does.

If your two nodes won’t talk and everything else looks right, that’s almost certainly what’s missing. Send an advert, give it a second, and try again. Mine went from stubbornly refusing to an instant delivery tick.

Into the Loft

Belmont sits high, and my roof is very nearly the highest point in it — on paper, the best thing I own for radio. But there was one thing that could have killed the whole plan: foil-backed roofing membrane. If that’s what’s under your tiles, you’re not putting a radio in a loft, you’re putting it in a very well-made metal box.

I got lucky — mine is a breathable membrane, not a foil-backed one, so the signal has a way out through the tiles. It’s worth checking yours with a torch before you plan a loft install.

Two hard-won tips for the install itself:

• Mount the antenna as high and as clear of the roof timbers as you can.
• Set the admin password and turn on remote admin while the node is still on the bench. You do not want to be climbing back up there with a laptop. Ask me how I know.

How Far Does It Actually Reach?

I’ve read people getting tens of miles out of these things. I’ve also read someone who couldn’t get five streets. Both of those are true, and the difference isn’t the money you spend — it’s whether the radio can see where it’s going.

So I drove out across the West Pennine Moors and tested it properly: close in (direct hop, easy), further out (watching the loft repeater appear in the hop count — that message went through my roof), then further still until the hills finally won. Watch the video above to see where the line actually fell.

The one thing I learned, putting all of this together: range isn’t something you buy — it’s something you climb. The cheapest node in the world with a clear view of the horizon will beat the most expensive one sat in a cupboard, every single time.

What This Is (and Isn’t)

Quick gut-check: this is not free phone service. It’s text only, it’s slow, it’s not private on the public channel, and that 10% duty cycle means it’s not somewhere you sit and chat all day.

But it works when your phone doesn’t — and that’s a different thing. That’s the useful thing:

• Walking the moors, where mobile coverage genuinely drops out for miles at a time
• Festivals, when ten thousand people are hammering the same cell site and nobody’s phone can get a word in
• Storms and power cuts — last winter a storm took out the power, the landlines and the mobile masts at the same time, which is exactly the moment you don’t want to rely on the one network that just went down with everything else

It doesn’t replace anything. It’s the thing that still works when the other thing doesn’t. That’s all it ever needed to be.

Join the Map

Have a look at the MeshCore map. London’s covered. Bristol’s covered. And around here? Almost nothing — until now.

If you’re anywhere near Bolton — or anywhere near an empty bit of the map — put a node up and let’s see how far this network can stretch. Tell me in the comments roughly where you are, and I’ll come back in a few months and show you what the map looks like then.

One thing worth thinking about first: putting a repeater on that map means putting roughly where you live on the map too. That’s your call to make — just make it a decision, rather than a default you never actually chose.

Learn MeshCore Properly

If this has got you tempted, I’ve written two full free courses that go much deeper than the video:

Off-Grid Messaging with MeshCore

Learn

Build your own off-grid LoRa mesh network with MeshCore and two cheap Heltec V3 boards - one as a repeater, one as a client. No internet, no phone signal, no subscription.

 1h 17m

MeshCore Room Servers and Sensors

Learn

Part 2 of the MeshCore series. Build the other two node types - a room server that stores messages for people who were out of range, and a sensor node that reports temperature, battery and tank levels across kilometres.

 1h 37m

Off-Grid Messaging with MeshCore

Everything in this post, step by step: how LoRa works, the hardware, antennas and the law, flashing, radio settings, repeater setup and placement, client setup, channels, paths and routing, remote admin, and troubleshooting. Two Heltec V3 boards and an afternoon — about £30 of hardware.

MeshCore Room Servers and Sensors

Part two covers the other two node types: a room server that stores messages for people who were out of range, and a sensor node that reports temperature, humidity, battery and tank levels across kilometres — all over the mesh, no internet involved.

Happy meshing — and if you put a node up, let me know how far you get!