Research carried out by air traffic control provider Nats, Thales UK and the R&D lab Roke Manor confirmed that a TV signal-based system can track aircraft flying up to 10,000ft.
By Lobodrl (Own work) [CC BY-SA 3.0], via Wikimedia Commons
In the experiment, a signal transmitted from at Crystal Palace in London was collected by three special receivers that measured the delayed waveforms to derive the location of the aircraft. Up to 30 aircraft can be tracked by this method.