Generating a WiFi Radio Heatmap with a Helical Antenna, Antenna Rotator and a HackRF
Over on YouTube The Thought Emporium channel has been working on creating a "WiFi Camera" over the past few weeks. The idea is to essentially create a small radio telescope that can "see" WiFi signals, by generating a heatmap of WiFi signal strength. This is done with a directional helical 2.4 GHz antenna and motorized rotator that incrementally steps the antenna through various angles. After each movement step a HackRF and Python script is used to measure WiFi signal strength for a brief moment, and then the rotator moves onto the next angle. The helical antenna and rotator that they created are made out of PVC pipe plastic and wood, and are designed to be built by anyone with basic workshop tools like a bandsaw.
The final results show that they've been able to successfully generate heatmaps that can be overlaid on top of a photo. The areas that show higher signal strength correlate with areas on the photo where WiFi routers are placed, so the results appear to be accurate. In the future they hope to expand this idea and create a skyward pointing radio telescope for generating images of the galactic hydrogen line, and of satellites.
The videos are split into three parts. The first two videos show the build process of the antennas and rotator, whilst the third video shows the final results.