An inexpensive Raspberry Pi Pico is giving a classic piece of packet-radio equipment a second life.
A new project called Pocket Pico recreates the Heathkit HK-21 Pocket Packet TNC—but there's an interesting twist. Instead of simply copying what the old TNC did, the Pico emulates the original Z80 processor and runs the old HK-21 firmware.
That makes this more than another modern APRS gadget.
Classic Packet Radio on Modern Hardware
The original Heathkit Pocket Packet was a small terminal node controller, or TNC. It allowed a computer and radio to communicate using packet radio.
Pocket Pico moves that job onto the inexpensive Raspberry Pi Pico.
The Pico also handles 1200-baud Bell 202 modulation and demodulation, eliminating the need for the original modem hardware.
According to Hackaday, the project supports:
AX.25 packet
APRS
A personal packet BBS
Older packet-radio software
That's an interesting combination of old and new.
Why This Project Is Interesting
Modern APRS applications can hide much of what's happening between the computer and radio. That's convenient, but it doesn't necessarily teach you much about packet radio.
Pocket Pico takes a different approach.
You get an opportunity to experiment with the technology behind traditional packet while using hardware that is inexpensive and readily available.
There's also something pretty neat about a tiny modern microcontroller pretending to be a Z80 processor so it can run amateur-radio software designed decades ago.
Old Ham Radio Technology Doesn't Have to Stay Old
Projects like Pocket Pico demonstrate one of the things I enjoy about amateur radio. Older technology doesn't necessarily become useless when the original hardware disappears.
Sometimes it just needs a new platform.
A Raspberry Pi Pico recreating a Heathkit packet TNC is a great example—and perhaps an inexpensive way for another generation of hams to discover packet radio.
Read more about the Pocket Pico project:
https://hackaday.com/2026/09/25/pi-pico-recreates-the-heathkit-pocket-packet/
More amateur radio, QRP and practical operating information:
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