How your TV signal reveals movement in the next room

A technical demonstration shows how ordinary digital TV signals can be used to detect movement through walls. By analyzing interference patterns (selective fading) in an ATSC broadcast signal captured with a software-defined radio, the experimenter detected when someone stood up from a chair and walked in a neighboring room. The disturbance creates visible 'stripes' in a signal spectrogram.

This reveals that common wideband radio signals—like TV, WiFi, and cellular—are all vulnerable to passive motion sensing by anyone with a cheap receiver. It's a stark reminder of how the radio waves constantly flooding our homes can be repurposed for surveillance, turning everyday devices into unintentional motion detectors. The post ends with a wry 'Happy paranoia!' highlighting the privacy implications.