Definition
Packet radio is a mode of sending digital data over amateur (ham) radio frequencies, packaging information into discrete frames that are transmitted, acknowledged, and reassembled at the far end. Built primarily on the AX.25 link-layer protocol, 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, and no commercial infrastructure — exactly the kind of resilient, grid-optional channel a sovereign operator wants as a fallback.
How it works
Data is broken into packets, each carrying source and destination callsigns, a sequence number, and an error-checking frame-check sequence. Receiving stations verify the checksum and acknowledge good frames, so corrupted packets are retransmitted rather than silently lost. Because AX.25 supports digipeating (digital repeating), a packet can hop across intermediate stations to reach a distant node, and bulletin-board systems (BBS) let messages be held and forwarded when the recipient is offline. This store-and-forward behavior makes packet radio naturally delay-tolerant.
Where it fits today
Packet radio is the ancestor of modern ham data modes and underpins systems like APRS (position and short-message reporting) and Winlink (radio email). It typically runs narrowband on VHF/UHF or HF, trading raw speed for range and resilience. As with all amateur-band operation, message content may not be encrypted, so packet radio is about resilient reach — keeping data moving when normal networks are down — rather than privacy.
For higher-throughput mesh data over WiFi hardware see AREDN, and for a cryptography-first transport that can ride the same radios see Reticulum.
In Simple Terms
Packet radio is a mode of sending digital data over amateur (ham) radio frequencies, packaging information into discrete frames that are transmitted, acknowledged, and reassembled…