MeshCore UK: settings, the rules and getting on air

UK settings at a glance

All four radio settings have to match, or your radio won't decode anyone. The older EU/UK Long Range preset (869.525 MHz, 250 kHz, SF11, CR5) isn't compatible, and German users have reported some radios dropping back to it after a reboot, so look at the settings again after any restart or update. Local groups such as MeshCore Yorkshire and ScotMesh publish the settings they use, and both match the table.

Is MeshCore legal in the UK?

Yes, without a licence. 869.618 MHz falls in 869.40 to 869.65 MHz, which Ofcom's IR 2030 (entry IR2030/1/19) opens to any short-range device that keeps to two conditions:

• No more than 500 mW ERP. That's the power leaving the antenna, compared with a dipole, so the antenna and cable count as well as the radio's setting.
• No more than 10% of the time transmitting, unless the device uses listen-before-talk and similar techniques to the standard set in EN 300 220. In practice, plan on 10%.

The firmware won't keep you to 10% unless you set it. MeshCore's firmware has an airtime budget per rolling hour, and its default is 50%. A handheld companion sending your own messages won't get close to 10%. A busy repeater can, because everything it forwards counts. On a repeater, the command set dutycycle 10 sets it to 10%. It was added in firmware 1.15; on older firmware, use set af 9, which does the same.

Working out your ERP

Take the radio's output in dBm, subtract the cable and connector loss, and add the antenna gain in dBd. Antenna gain is usually quoted in dBi, so subtract 2.15 to get dBd. Most LoRa radios go up to 22 dBm, which is legal into a small whip but over the limit into a high-gain collinear: 22 dBm into a 9 dBi antenna with 1 dB of loss is about 610 mW ERP. The checker at the top of the page does the sum and tells you the highest setting your antenna allows.

At 62.5 kHz wide, the signal runs from 869.587 to 869.649 MHz, right at the top edge of the band, so the radio's own emissions need to meet the standard too. Buy radios sold for the UK or EU 868 MHz band.

What you need

• A MeshCore-supported LoRa radio for 868 MHz. Look up your board, including its version number, in the MeshCore web flasher. 433 MHz and 915 MHz versions of the same board won't work here.
• An antenna made for 868 MHz, with the right connector. Never power a radio up without its antenna.
• A phone with the MeshCore app by Liam Cottle (links on meshcore.io), or a browser for the web app.
• A USB data cable and a computer with Chrome or Edge, if you need to flash the firmware yourself.

Before you buy, look at the MeshCore map and your nearest local group to see whether there are repeaters near you. Two radios always work between themselves, so buying a pair is a good way to start if your area is quiet.

Getting on air

1. Flash the companion firmware. In the flasher, pick your exact board, a stable release and the Companion Radio (BLE) firmware for use with a phone. Use a data cable, not a charge-only one. Some boards need a button held while plugging in to start the bootloader.
2. Pair the app. Turn on Bluetooth, allow the app's nearby-device permission, and pick your radio from the list. Radios with a screen show a PIN; screenless ones use 123456 by default.
3. Choose the preset. In the radio settings, select EU/UK (Narrow), then check the four values in the table above have stuck.
4. Name your node. Use something short that people will recognise, but not your address. Decide whether to include your position in adverts: you can leave it off, or set a rough location.
5. Set your local scope and path hash size. Ask your local group. Many UK repeaters drop messages with no scope (see below).
6. Send an advert, then a short message on the Public channel or your local channel, and wait for a reply. Try outside or by a window first.

How messages get through

Your phone only talks to your own radio, over Bluetooth. Your radio does the long-distance part on 869.618 MHz, and repeaters pass messages on. Your own radio, called a companion, never repeats anyone else's traffic.

The first message to someone floods: every repeater that hears it sends it on once, so it spreads in all directions until it reaches them or runs out of repeaters. Their radio sends the route back with its acknowledgement, and later direct messages travel only along that path. If a repeater on the route goes off air or someone moves, the stored path stops working; resetting the path in the app makes the next message flood again.

• Heard repeats on a channel message counts the repeaters your radio heard passing it on. It shows the message left your area, not that anyone read it.
• Delivered on a direct message means the other radio sent back an acknowledgement. No acknowledgement doesn't always mean it failed: the reply may be the part that got lost.
• Each repeater adds its path hash (1, 2 or 3 bytes) to the packet. 1 byte is the firmware default. Larger hashes stop two repeaters sharing an ID on big meshes and need firmware 1.14 or later; ScotMesh, for example, uses 3 bytes.

Channels, direct messages and rooms

All of them share the one radio channel, so adding chat channels doesn't add capacity. Messages are encrypted, but your node name, any position you advertise, and when you transmit are visible to anyone listening. Channel messages hold up to 160 bytes, including your name. Messages aren't stored for people who are offline unless you use a room server.

To send direct messages, both radios need each other as a contact. You'll see other nodes' adverts under Discover Contacts, and you can also swap contacts by QR code or public key. Keep your private key, and any backup file that contains it, to yourself.

Scopes in the UK

A scope is a region name added to flood messages, so repeaters know how far to carry them. It doesn't change the frequency or make anything private. Since firmware 1.15 you can set a default scope for your companion, which in the app is under Experimental settings (app 1.43 or later). Some current examples:

Other areas may use different names or none. Your local group will know, and the app's Discover Regions tool lists the scopes reported by repeaters in direct range.

Antennas, height and range

Height and a clear view make more difference than anything else. A radio in a pocket indoors might reach a few hundred metres; the same radio at an upstairs window, or a repeater on a hill, can reach many kilometres. Hold or mount the antenna vertically, clear of your body and any metal. At 869 MHz, thin coax loses a lot: 5 m of RG58 loses around 2.5 dB, nearly half your power, so keep cable short or use low-loss coax. If you change the antenna, run the checker again, because more gain means more ERP.

Putting up a repeater

• Talk to your local group first. A repeater in the wrong place adds traffic and collisions without adding coverage.
• Flash the Repeater firmware for your board, set the UK preset, and change the admin password before it goes up.
• Set the airtime budget to 10% with set dutycycle 10 (set af 9 on firmware older than 1.15), check its ERP, and set the scopes and path hash size the local network uses.
• For solar, size the panel and battery for December, not June, and keep the enclosure out of direct sun.

When it doesn't work

MeshCore isn't an emergency service and nobody is guaranteed to be listening. In an emergency, call 999 or 112.

Sources

• Ofcom, IR 2030, 23 October 2026 edition, entry IR2030/1/19.
• MeshCore official site, FAQ, default scope notes and firmware source.
• MeshCore Yorkshire, ScotMesh and HanseMesh settings pages.

Checked November 2026. MeshCore changes quickly, so check with your local group too. For the US, see the MeshCore USA guide.

Questions