Open-Source QuadRF Sees WiFi Through Walls, Tracks Drones
QuadRF, an open-source phased-array radio built on Raspberry Pi 5 and FPGA, can see WiFi traffic through walls and detect drones in flight.
QuadRF is a handheld phased-array radio built around a Raspberry Pi 5 and an FPGA board with picosecond-level timing precision. It was developed by Martin McCormick, a former SpaceX engineer who worked on the original Starlink Dishy terminal, as a scaled-down version of a much larger project aiming for Earth-Moon-Earth (EME) radio experiments.
Operating in the 4.9-6 GHz range, QuadRF runs a browser-based VNC interface offering GNU Radio, SDR tools, and a custom augmented-reality RF visualizer. In hands-on testing, the author was able to visually distinguish WiFi networks as colored 'blobs' and successfully tracked a flying DJI drone, despite the UI still feeling rough around the edges.
A standout engineering detail is how I/Q data is streamed at over 5 Gbps with low latency through the Raspberry Pi's camera/display MIPI lanes instead of USB — achieved by reverse-engineering the MIPI protocol on the Pi 5's RP1 chip. This design also allows multiple QuadRF units to be daisy-chained, each calculating its own phase shift, while leaving the PCIe port free for storage or networking.
The Crowd Supply campaign has already exceeded expectations, with a basic kit priced at $499 and the enclosure moving from 3D-printed to injection-molded. As pre-production hardware, results should be taken with some caution, but the project highlights how far open-source RF engineering has come.