What is permitted, what is not — and why your digital voice radio is legal.
Every digital voice operator eventually asks the same question: if my DMR or P25 radio turns my voice into an unintelligible digital stream, isn't that encryption — and isn't encryption banned on the ham bands? The short answer is no, and the reason is a single distinction the FCC rules turn on: the difference between encoding a message and encrypting it. This page lays out what the rule actually says, what it permits, what it forbids, and where the genuine gray areas are.
The governing text is in 47 CFR §97.113(a)(4). Among the things it prohibits are "messages encoded for the purpose of obscuring their meaning." That single clause is the whole encryption rule. Notice what it hinges on: not whether a transmission is hard to decode, not whether it's digital, but whether the purpose is to obscure the meaning from other listeners.
That framing is deliberate. The amateur service is built on the premise that anyone may listen — there is no expectation of privacy on the ham bands, and the prohibition itself traces back to international treaty obligations, since amateur signals routinely cross borders. The rule exists to keep the bands open and self-policing, where any licensed operator can monitor and verify what's being sent.
Both encoding and encryption turn your voice or data into something that isn't plain language. The difference is whether the method to get it back is public.
Your DMR, P25, NXDN, D-STAR, Fusion, and M17 radios all encode. The vocoders that compress your voice (AMBE, AMBE+2, IMBE, Codec 2) and the protocols that carry it are publicly documented; anyone can buy or build a decoder. The digital stream sounds like noise to an FM receiver, but it isn't secret — and "sounds like gibberish to the wrong receiver" is not the test. The test is purpose and recoverability.
All the common amateur digital voice modes are legal because their codecs and protocols are public. A receiver that can't decode them is missing the documented method, not being locked out by a secret key. Run DMR, P25, NXDN, D-STAR, Fusion, or M17 freely.
For data and RTTY, §97.309 allows the specified codes (Baudot, AMTOR, ASCII) and any other digital code whose technique has been publicly documented. The principle was settled decades ago when the FCC approved modes like PACTOR, G-TOR, and CLOVER specifically because they were openly documented and commercially available — using them doesn't obscure meaning, it just formats it efficiently.
Squeezing data to make it smaller is not encryption. As long as the compression method is standard and recoverable, the meaning is intact — it's just packaged tightly.
Codes used to control a station rather than to hide a message are allowed. The rules explicitly contemplate special codes for the telecommand of model craft (§97.215) and for space-station telecommand (§97.211). A control sequence isn't a "message" being obscured; it's an instruction to equipment.
Any scheme whose point is to keep other amateurs from understanding your traffic is prohibited — full stop. A secret key, a private cipher, a scrambler: if the goal is that only your intended party can read it, it's out.
This is the practical trap for digital-voice operators. Surplus commercial and public-safety radios ship with real encryption (DES, AES) built in for their business and agency customers. Those features are illegal to use on the amateur bands and must be left switched off. The radio is fine; the encryption setting is not. (This is why public-safety P25 and NXDN traffic can be scrambled, but amateur P25 and NXDN always run "in the clear.")
This comes up constantly, so it's worth being clear: petitions to carve out an exception allowing encryption during emergency operations or training — to protect things like medical (HIPAA) data — have been brought to the FCC and dismissed. The Commission concluded the change would undermine the open, monitorable character of the service and wasn't shown to be necessary. As the rules stand, EmComm traffic must be sent in the clear like everything else.
A few cases sit closer to the line and are worth understanding rather than guessing about:
While we're in §97.113, the same section bars several other things often confused with the encryption question: music on phone (with narrow exceptions), communications to facilitate a criminal act, obscene or indecent language, false or deceptive signals or identification, broadcasting to the general public, and messages sent for pecuniary (business) interest. None of these are about encryption, but they're the neighbors of the rule and round out "what you can't send."
Part 97 doesn't ban digital, complexity, or anything that merely sounds like noise. It bans one specific thing: encoding a message to obscure its meaning from other amateurs. Your digital voice radios are legal because their methods are public and anyone can decode them. The only encryption you're likely to encounter — the DES/AES options inside surplus commercial radios — is exactly the thing you must keep turned off. Encode all you like; just don't keep secrets.