Flying a quadrotor near an actual airport is a dumb idea to begin with, but it hasn’t stopped some people. So, the FAA is testing technology that would track down drones—or any other R/C aircraft—that are getting a little too close for comfort.
Rather than tracking the drones themselves, which would require all sorts of expensive physics-defying radar, the FAA’s system would detect the radio signals being used to control them. The technology is being developed by CACI International, and sounds like fairly straightforward radio-location tech: it would be able to detect radio signals in the (fairly predictable) range used for controlling R/C aircraft, and then locate the remote control being used.
The FAA hasn’t said exactly where the systems would be deployed; given the cost, it’s unlikely it would be every tiny airstrip in the States. But it does seem to be a problem: according to the FAA, it gets around 100 reports a month of drones being operated close to aircraft or airports.