A number of countries have installed HF Over The Horizon Radar (OTHR), the French system is called Nostradamus and operates from 6-30 MHz.
The Nostradamus radar system is a set of 288 bi-cone antenna elements distributed over the arms of a three-branch star, with a buried infrastructure to shelter the transmission and reception electronics.
It is claimed to detect any aircraft flying 700 to 2000 kilometers away.
Watch Nostradamus, the French skywave over the horizon radar
