I Mapped an Entire Building’s RF Footprint Without Walking Inside. Here’s How.

A 200$ drone, a 25$ SDR dongle, and an afternoon. That’s all it took. It started with a bet. A friend — let’s call him Marcus — works in physical security. He runs RF site surveys for corporate clients. The kind of work where you walk into a building with a spectrum analyzer, a directional antenna, and a laptop, and you spend two days mapping every wireless signal in the place. He charges $8K per survey. I told him I could do the same thing from the parking lot. He laughed. I didn’t. Three weeks later, I had a complete RF heatmap of a 40,000 sq ft office building — every Wi-Fi AP, every Bluetooth beacon, every rogue device, every cellular signal — all captured from a drone flying 200 feet above the roof. No badge. No lobby. No security guard blinking at me weird. Marcus stopped laughing. Here’s exactly how I did it. The Setup (Under $250 Total) Let’s get the hardware out of the way first because it’s almost embarrassingly cheap.