HUMANIKRONOne cheap RTL-SDR dongle + a Raspberry Pi — and you get a pocket radio centre that you control from your phone through a browser. I called it ARGUS.
What it can do
- FM radio with demodulation and gain control.
- Aviation — ADS-B. I decode aircraft positions (altitude, speed, tail number) via pyModeS and show them in a list.
- Spectrum scanner. rtl_power builds a waterfall across a band — you can see where the "live" signals are.
- Decoders. rtl_433 (sensors, weather stations), multimon-ng (pagers/tones), a band plan with presets.
The main challenge — a single dongle
All of these modes want the same receiver at the same time. So the heart of the system is an arbiter: a small Python service that hands the dongle to modes in turn, kills the previous process and stops them from locking each other out. Without it, two requests kill the radio.
Architecture
FastAPI serves JSON and the dashboard itself (a single HTML), the rtl_* processes start on demand, and the result streams to the browser. Access is only inside a private tailnet, so you can "listen" from anywhere, but nothing is exposed to the outside.
Conclusion
SDR is not "hacker magic" but ordinary engineering: processes, queues, parsing. With $30 of hardware and a Raspberry Pi you get a tool that used to cost as much as a car.