Meshtastic and MeshCore on EU 868 MHz: The Amateur-Radio Trap

LoRa mesh projects invite good amateur instincts: improve the antenna, choose a high site, add a relay and use all the power the hardware can deliver. On European licence-exempt spectrum, those same instincts can quietly move a node outside the conditions that made it licence-exempt.

The Trap in One Sentence

Meshtastic and MeshCore are software projects, not radio services. A node can be lawful as short-range equipment, or it can be operated under an amateur authorisation on an amateur allocation, but the operator cannot combine the convenient parts of both frameworks.

Putting a callsign in a node name does not change the allocation. Selecting a “licensed” or unrestricted firmware setting does not create authority. Conversely, a licence-exempt SRD node does not gain amateur privileges merely because its owner is a licensed ham.

Four Gates Must Pass at the Same Time

“EU 868” Is a Software Label, Not One Legal Limit

The harmonised European SRD framework contains several entries across 863–870 MHz. They do not all use the same power, duty cycle, bandwidth or access conditions. A statement such as “868 MHz permits 500 mW” is incomplete until it names the exact frequency range and device category.

The Meshtastic EU_868 profile and the commonly used MeshCore frequency sit in the 869.4–869.65 MHz non-specific SRD entry. The current EU harmonised table permits up to 500 mW e.r.p. there, subject to qualifying spectrum-access and interference-mitigation techniques or, alternatively, a duty cycle not exceeding 10%.

This wording matters. Ten percent is not the only conceivable route in the harmonised entry, but it is the simple route implemented by many nodes. If a product relies on the access-technique route instead, that technique and its conformity assessment need evidence. A setting called listen-before-talk is not, by itself, that evidence.

What 10% Duty Cycle Actually Means

Duty cycle is transmitted on-air time divided by the relevant observation period. As a useful one-hour intuition, 10% corresponds to 360 seconds of transmission. The precise assessment method comes from the applicable regulatory and standards framework, not from this arithmetic shortcut.

Count every emission from the transmitter:

• user messages and acknowledgements;
• position, telemetry and neighbour information;
• advertisements, discovery traffic and keep-alives;
• forwarded mesh packets;
• retries after collisions or missing acknowledgements; and
• administrative and remote-control traffic.

The limit applies to the transmitter, not to the network as a single shared account. Ten nodes can each satisfy a device-level limit and still create a badly congested channel. Legal maximum airtime is therefore a poor normal operating target.

Meshtastic’s Current EU_868 Guardrails

Current official Meshtastic documentation and firmware source define the EU_868 region as 869.40–869.65 MHz, up to +27 dBm e.r.p., with a 10% duty-cycle limit. The standard LongFast channel is centred at 869.525 MHz.

That is a sensible attempt to fit the duty-cycle alternative of the 500 mW e.r.p. entry. It is still only part of the compliance case. The software does not measure the installed antenna gain, verify the finished board’s emissions, inspect the Declaration of Conformity or know whether an external amplifier was added.

Meshtastic also documents settings intended for licensed amateur operation that can lift regional power restrictions. That capability is useful only inside an authorised amateur framework. Enabling it while remaining on the EU 869.525 MHz SRD channel removes a software guardrail; it does not create legal permission.

MeshCore’s Current Default Needs Deliberate Attention

Current official MeshCore CLI documentation lists 869.525 MHz, 250 kHz bandwidth, spreading factor 11 and coding rate 4/5 as the default radio settings. It also documents a duty-cycle control from 1% to 100%, with 50% as the default and 100% meaning no software limit.

A 50% setting does not satisfy the 10% duty-cycle alternative at 869.4–869.65 MHz. Selecting 10% is the obvious configuration when that is the compliance route. A higher value could only be justified by a different applicable route that the actual equipment implements and its conformity evidence supports.

MeshCore’s documentation also notes that the configured transmit-power value controls the LoRa device and that an external PA may increase total output. The number in the settings screen is therefore not necessarily the conducted power at the antenna connector.

ERP, EIRP and the High-Gain-Antenna Surprise

The European entry is expressed in e.r.p., referenced to a half-wave dipole. Antenna catalogues often use dBi, referenced to an isotropic radiator. Mixing them creates a 2.15 dB error.

Therefore 27 dBm e.r.p. is approximately 29.15 dBm e.i.r.p., or about 823 mW e.i.r.p. The reference must always be named.

A hypothetical 33 dBm transmitter

Assume a measured +33 dBm at the transmitter output, 1 dB of cable and connector loss, and an antenna with 6 dBi peak realised gain in the relevant direction and polarisation:

That is about 7.7 times the 500 mW e.r.p. limit. The example is deliberately generic: a product name, front-panel setting or module data-sheet maximum is not a calibrated measurement of the finished node.

A high-gain antenna is not unlawful by definition. It means conducted power must be reduced enough that the complete installed system remains within the applicable radiated-power limit, with measurement uncertainty and manufacturing variation allowed for.

The RED/CE Gate Does Not Disappear

For normal SRD operation in the EU, spectrum conditions and Radio Equipment Directive conformity are separate requirements. Check the exact finished product, not merely the radio chip:

• product identity, manufacturer and responsible economic operator;
• CE marking and the EU Declaration of Conformity;
• declared frequency range, power and supported antennas;
• firmware and region configuration covered by the evidence;
• occupied bandwidth, receiver behaviour and unwanted emissions; and
• installation instructions and environmental limits.

An external PA, altered filter, unsupported antenna, changed power supply or unrestricted firmware may move the finished configuration outside the evidence used for conformity. A callsign does not waive RED obligations for ordinary SRD equipment.

Amateur-built equipment has specific treatment under the RED, but that is not a blanket exemption for a commercially supplied module or finished product with a user-added amplifier. The precise builder, supply and use circumstances matter.

Why High Sites and Routers Need More Engineering

A fixed router, repeater or high-site node is not automatically unlawful. It does, however, hear and forward more traffic, cover more territory and make poor filtering or excess radiated power affect more users.

A permanent node should have:

• a recorded firmware version and exported configuration;
• measured conducted power and unwanted emissions for the actual board;
• a cable-loss and antenna-gain budget that closes at the required e.r.p.;
• airtime logs covering busy periods, relaying and retries;
• a conservative capacity budget rather than operation at the legal ceiling;
• remote monitoring and a reliable stop-transmitting function;
• operator contact details; and
• weather, electrical, RF-exposure and lightning provisions appropriate to the site.

Good mesh coverage is compatible with responsible operation. The engineering goal is predictable capacity and a documented legal configuration, not maximum range at every cost.

Can 70 cm Amateur Radio Solve the Problem?

Sometimes it can provide a more suitable framework for experimentation, but it is a different project—not an escape switch.

Belgium includes amateur allocations within 430–440 MHz, with class, sub-band and power conditions that must be checked in the current BIPT tables. The band is shared and structured: repeaters, satellites, weak-signal work, digital activity and coordinated services all need consideration. An amateur allocation is not one empty 10 MHz channel.

Meshtastic normally uses AES-encrypted channels. Amateur rules in many countries restrict messages that obscure their meaning and impose identification, content, unattended-station and remote-control conditions. Do not copy an encrypted SRD configuration onto 70 cm and assume the callsign makes it valid.

The UK and United States Are Separate Cases

The UK publishes its own licence-exempt interface requirements through Ofcom. Do not treat an EU table as the final UK authority after Brexit; check the current IR 2030 entry and applicable equipment rules.

In the United States, 902–928 MHz can involve Part 15 licence-exempt operation as well as a secondary amateur allocation under Part 97. Those are separate legal routes with different equipment, identification, content and interference obligations. Geographic frequency overlap does not let an operator mix their privileges.

A Defensible Pre-Transmit Workflow

1. Name the legal route. SRD, amateur or another authorisation—not merely “LoRa.”
2. Record the exact entry. Frequency, device category, radiated power, bandwidth and access or duty-cycle condition.
3. Identify the hardware. Board revision, RF front end, PA path, filter and band variant.
4. Preserve conformity evidence. Declaration, instructions, intended antennas and supported firmware configuration.
5. Measure conducted RF. Power, occupied bandwidth and unwanted emissions need suitable calibrated equipment and attenuation.
6. Close the radiated-power budget. Include real cable loss, connector loss, installed antenna gain and uncertainty using the correct dBi or dBd reference.
7. Configure airtime. Count messages, beacons, telemetry, relaying, acknowledgements and retries.
8. Test worst-case traffic. A quiet bench node does not represent a busy high-site router.
9. Lock and monitor the configuration. Record firmware updates and repeat the review after material changes.
10. Provide a shutdown path. Every unattended node should be attributable and controllable.

The Practical Verdict

Meshtastic’s current EU_868 profile provides useful guardrails for one 869.4–869.65 MHz SRD route. MeshCore’s current 50% duty-cycle default requires deliberate correction when relying on the 10% alternative. Neither firmware can certify arbitrary boards, amplifiers, antennas or installations.

The ham-radio trap is believing that technical competence or a callsign supplies missing permission. It does not. The more durable amateur habit is measurement: verify the rule, firmware, airtime, output, antenna system and unwanted emissions as one complete station.

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