Continuing my foray in to the world of Meshtastic: I’ve noticed something pretty frustrating with the nodes in my area. There seems to be a 50/50 split between those with callsigns and encryption disabled (i.e. Nodes operating under “licensed mode”) and those without. And - by design - these two groups of nodes cannot communicate with eachother.

Meshtastic has taken a rather strict view of the licensing conditions that most amateur radio licence holders are expected to abide by, specifically the prohibition on encrypted radio transmissions. To quote the UK regulator (Ofcom) and their licence conditions document (OFW611, Licence Condition 6 (19)):

Unless the Radio Equipment is being used for the purposes of clause 5, the Licensee must ensure that:

a) Transmissions are only addressed to one or more amateur radio station(s);

b) Transmissions between amateur stations are not encrypted for the purpose of obscuring their meaning, except for control signals exchanged between earth command stations and space stations in the amateur-satellite service.

As a result of this clause, and similar ones stipulated by corresponding regulatory agencies in other regions (i.e. FCC Part 97 §97.113(a)(4) in the US), Meshtastic essentially isolates nodes which are associated with a licensed amateur radio operator and restricts them from communicating with unlicensed nodes. This decision is documented in the Meshtastic FAQ.

Once the operator has configured their device to operate as a “licensed node”, then:

1. decryption will no longer be used (breaking interoperability);
2. the device will drop any messages that are encrypted - preventing re-broadcasts and ultimately degrading the Mesh Algorithm;
3. the device will publicly transmit the associated callsign every 10 minutes.

Whilst it seems like an understandable precaution, albeit one that is overly-cautious and damaging to the health of the network, it does present one big question…

Do Licence Conditions apply when an operator is conducting an activity which does not require a licence?

Meshtastic is excellent because - in itself - it requires no licence: devices operate within the ISM band (i.e. 433MHz or 868MHz in the EU/UK) and tend to have low output power.

With this in mind, if using these devices - within the relevant power limits - is not an activity that requires an operator to act under the privilege of their licence, then does it require adherence to the conditions of their licence? Surely the licence conditions are only a consideration when one is performing an activity that requires the licence?

To pose a similar situation, I could buy a TP-Link Archer AXE75, a COTS¹ WiFi router complete with a 6-antenna array, capable of outputting 200 mW (apparently going as high as 1000 mW)… entirely encrypted. Whilst a Heltec V3 acting as a Meshtastic node will likely be transmitting with a power no greater than 22 dBm (or ~150mW).

Neither device requires any form of licence to operate, so where is the implication that using one is subject to additional conditions?²

Rather than trust my own questionable interpretation of the rules though, I’ve decided to simply ask Ofcom. Here’s the email³:

I was wondering if you could provide some clarification regarding the permissibility of encrypted transmissions. My specific query pertains to the open-source project “Meshtastic”. Meshtastic currently has a thriving community of enthusiasts, and has the following characteristics:

1. It does not require a licence owing due to it’s operating frequency of 868Mhz and low power output.
2. Devices (or “nodes”) are configured to retransmit encountered messages, enhancing the range at which a transmission may occur.
3. Messages sent across nodes may utilise optional encryption, by default these messages are encrypted using a pre-defined key.
4. Licensed radio amateurs may provide their callsign as an identifier, in which case both (a) encryption, and (b) the retransmission of encrypted messages, are disabled.

There seems to be some confusion as to whether (4) above is strictly necessary in accordance with Licence Condition 5 (“Radio Equipment Use”), specifically clause 19(b)? Whilst the operator holds a amateur licence, are they bound to those conditions of the licence even when they’re not performing an activity that requires their licence - i.e. operating a lower power device on 868Mhz?

Let’s see what the official stance is.

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