Packet Radio

Packet radio is a mode of sending digital data over amateur (ham) radio frequencies, packaging information into discrete frames that are transmitted, error-checked, acknowledged, and reassembled at the far end. Built primarily on the AX.25 link-layer protocol — an amateur adaptation of the X.25 standard using callsigns as addresses — it turns a radio and a small modem (a TNC, or terminal node controller) into a store-and-forward data link that works with no internet, no cellular network, and no commercial infrastructure of any kind. For a sovereign operator, it is the proven, decades-old answer to the question "how does data move when everything else is down?"

How it works

Data is broken into packets, each carrying source and destination callsigns, control and sequencing information, and a frame-check sequence for error detection. Receiving stations verify the checksum and acknowledge good frames, so corrupted packets are retransmitted rather than silently lost — a genuinely reliable link over an unreliable medium. Because AX.25 supports digipeating (digital repeating), a packet can hop through intermediate stations to reach a node beyond direct radio range, and bulletin-board systems (BBS) hold and forward messages for stations that are off the air. Classic deployments run at 1200 baud AFSK on VHF/UHF — slow by any modern standard, but astonishingly robust — with 9600-baud FSK links and slower HF operation extending the trade-space between speed, range, and reliability. The TNC's job has increasingly moved into software: a sound-card interface and a modem program on any computer, including a Raspberry-Pi-class board running beside a node, do what dedicated hardware once did.

Where it fits today

Packet radio is the ancestor of most modern ham data modes and still underpins two workhorses: APRS, the position-and-telemetry reporting network that runs largely over 1200-baud AX.25, and Winlink, the radio email system whose VHF/UHF sessions commonly ride packet links. Its store-and-forward nature makes it naturally delay-tolerant: messages move when propagation and station availability allow, which is exactly the right model for emergency traffic and off-grid coordination. In the modern sovereignty stack it sits alongside newer kin — LoRa-based Meshtastic meshes for license-free short messaging, and Reticulum, a cryptography-first network stack that can run over packet-radio hardware itself.

The rules of the band

Beyond simple digipeating, the packet era built real network infrastructure: NET/ROM and similar node firmware turned stations into automatic relays that discovered each other and routed traffic across multi-hop paths, and regional BBS networks forwarded messages continent-to-continent over HF gateways — a volunteer store-and-forward internet before the internet was public. Getting started today is deliberately anticlimactic: a VHF handheld, a USB sound-card interface, free modem software, and a local APRS frequency will have you passing packets within an evening, and the same station doubles as an emergency-traffic asset the day the region's infrastructure has a very bad week.

Two constraints follow from operating under an amateur license. You need the license — obtainable nearly everywhere, and the exam is not difficult — and message content may not be encrypted on amateur frequencies, nor may traffic be commercial. That means packet radio offers resilient reach, not privacy: treat everything sent as public. Authentication without content encryption (signing a message so recipients know it is genuinely yours) is the community's accepted pattern for trustworthy traffic. Understood on those terms, packet radio remains one of the cheapest, most battle-tested fallback channels a self-reliant operator can field: a handheld radio, a sound-card interface, and software are enough to move real data across a region with zero dependence on anyone's infrastructure. For higher-throughput mesh networking over WiFi hardware under the same amateur rules, see AREDN.