Hmm, not your typical RADAR. This is basically using the RF emissions of the plane, and their detection at multiple RF detection stations with synchronized clocks, to determine the difference in arrival time. The radio emissions all travel at the same speed through the air, the difference in arrival time can be used with some simple trig to figure out where the RF emitter is. There are a number of Time Difference of Arrival or TDOA systems out there. It is why I expect aircraft stop using their radios when they are about to engage their targets.
That said, they are "easy" to jam in the sense that when you have two radio signals on the same frequency, they will interfere with direction finding. And there is a lot of noise in the RF spectrum out there, especially during thunderstorms.
That said, they are "easy" to jam in the sense that when you have two radio signals on the same frequency, they will interfere with direction finding. And there is a lot of noise in the RF spectrum out there, especially during thunderstorms.