Meshtastic: Is Licensed Mode really necessary?

Continuing my foray into the world of Meshtastic: I’ve been getting to grips with my local mesh network, and I’ve hit something a bit frustrating. There’s roughly a 50/50 split between nodes with callsigns and encryption disabled (i.e. nodes running in “licensed mode”) and those without. And - by design - these two groups can’t talk to each other.

Which feels like a bit of a problem for a protocol built around… well, meshing.

What’s Going On?

Meshtastic has taken a pretty strict view of the licensing conditions that amateur radio operators are expected to follow - specifically the prohibition on encrypted transmissions. To quote Ofcom’s licence conditions (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.

Similar clauses exist elsewhere - FCC Part 97 §97.113(a)(4) in the US, for example. So Meshtastic’s response has been to isolate nodes belonging to licensed operators, preventing them from talking to unlicensed nodes entirely. Their reasoning is documented in the FAQ.

Once you flip your device into “Licensed Node” mode:

1. decryption gets disabled (breaking interoperability);
2. the device drops any encrypted messages it encounters - no re-broadcasts, which degrades the mesh algorithm;
3. your callsign gets transmitted every 10 minutes.

Now, this is opt-in behaviour. Out of the box, Meshtastic devices ship with encryption on and no callsign. The unlicensed use case is the default - Licensed Node mode is something you actively choose.

Which got me thinking…

Do Licence Conditions Even Apply Here?

Here’s the thing: Meshtastic doesn’t need a licence. Devices run on the ISM band (433MHz or 868MHz in the EU/UK) at low power. No licence required.

So if I’m using one of these devices - within the power limits, on an unlicensed band - I’m not doing anything that requires my amateur licence. Why would the conditions of that licence apply?

Think about it this way: I could go and buy a TP-Link Archer AXE75 - a chunky WiFi router with a 6-antenna array, pushing 200mW (maybe even up to 1000mW)… completely encrypted. Meanwhile my Heltec V3 running Meshtastic is transmitting at maybe 22dBm (~150mW).

Neither needs a licence. So why would one be subject to extra conditions just because I happen to hold an amateur licence for other activities?

The obvious counterargument is propagation. Fair enough - my encrypted 868MHz signal could travel kilometres, while my neighbour’s 5GHz WiFi isn’t making it past their hedge. But that’s a difference of degree, not kind. Both are unlicensed transmissions within their regulatory limits. If propagation alone determined whether licence conditions kicked in, we’d need a much more nuanced framework than “you’ve got a licence, so these rules follow you everywhere.”

Time to Ask the Experts

Rather than trust my own dodgy interpretation, I’ve lobbed an email at Ofcom¹:

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 its 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 an 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?

I’ll update this when I hear back.

• ← Previous Post
• Next Post →