If you use APRS, Winlink, or AREDN, you’re already relying on packet radio, whether you realize it or not. It’s one of the oldest digital modes in the hobby, and it’s also one of the most quietly influential, since so much of what came after it borrowed from the protocol it introduced.
AX.25, the protocol underneath everything
Packet radio uses AX.25, an amateur adaptation of the X.25 networking protocol, first standardized for ham use in the early 1980s. AX.25 breaks data into addressed packets with error checking built in, the same basic concept every modern network protocol uses, just adapted for the limitations of an HF or VHF radio link instead of a wire. That packet-based structure is exactly what let amateur radio start behaving like a real data network instead of just a voice or CW medium.
The BBS era
Through the 1980s and into the 1990s, packet radio ran an entire ecosystem of amateur bulletin board systems, message forwarding networks, and even early forms of amateur email, years before most hams had internet access at home. Packet BBSs let operators leave messages for each other and relay traffic across whole regions using nothing but VHF radios and terminal node controllers (TNCs) to handle the AX.25 framing.
Where packet’s DNA lives on today
Classic packet BBS activity has mostly faded, but the protocol didn’t die, it just got absorbed into newer systems. APRS still uses AX.25 framing for its position and messaging packets. Winlink’s packet-mode gateways use it too, alongside the newer VARA and ARDOP options. Even AREDN, while built on standard WiFi hardware and IP networking rather than AX.25 directly, inherits the same packet-switched philosophy that made 1980s ham packet radio possible in the first place. Understanding packet radio isn’t really about reviving an old mode, it’s about understanding the foundation several modes you probably already use are quietly built on.
Related reading: What Is RTTY? · What Is APRS? · What Is VARA?