For the past few months, I’ve been listening to local repeater conversations during morning commutes — and one topic keeps coming up: APRS.
Frames, messages, digipeaters, position reports… it’s clearly a big part of the ham radio world.
So, I decided to build a small APRS station of my own — partly to learn how it all works, and partly because I don’t (yet) own a transceiver with built-in APRS support.
The idea
I had a Raspberry Pi Zero W sitting in a drawer, waiting for a new project.
After browsing through the excellent FM Poland documentation on building a homebrew APRS hotspot, I realized it was a perfect starting point.
The goal was to create a simple KISS TNC setup using the Pi, and then connect it to a basic handheld radio — no special APRS hardware required.
Hardware setup
Here’s the final hardware stack:
- Raspberry Pi Zero W
- Waveshare Ethernet + USB expansion board (adds 3× USB ports and wired network, which made setup much easier)
- Modified CM108 USB sound card (wired for PTT and audio in/out following the FM POLAND guide)
- Baofeng UV-82 handheld radio as the transceiver
It’s a very modest build, but it works surprisingly well.
The CM108 handles the analog-digital conversion for audio and PTT control, while the Pi runs the digital side.
Software
I installed Raspberry Pi OS Bookworm (Lite) — small, fast, and perfect for headless operation.
Then came the main part of the setup: Direwolf, running in KISS TNC server mode.
Direwolf is an incredibly capable software TNC and digipeater for packet radio.
With a little configuration tweaking, it happily communicates over the sound card interface and lets any connected application handle APRS data frames.
Once the PTT wiring was confirmed and the audio levels tuned, packets started appearing — always a satisfying moment.
On-air testing
For initial tests, I used my Baofeng UV-82, tuned to the local APRS frequency.
It’s not the ideal radio for packet work — the audio response isn’t exactly linear, and it lacks filtering — but it’s good enough to get on the air and verify that everything works.
I was able to receive and decode APRS packets locally, and even send a few test beacons through nearby digipeaters.
Next steps
Now that the basic setup works, I’m planning to:
- Add RF filters to the Baofeng to clean up the transmitted signal
- Possibly replace the radio with something more suitable
This project turned out to be a great way to learn the nuts and bolts of packet radio — and it’s incredibly satisfying to see your own APRS packets appear on the map.
Images
References
73 SP3LSN