Well fortunately we can ask him. The F-117 was downed by Colonel Zoltan Dani, former commander of the 3rd battery of the 250th Missile Brigade in Belgrade, on March 27, 1999.
Question: "How did you manage to spot the stealth fighter?"
Zoltan Dani: "To that end, we used the Soviet-made P18 meter band radar which is capable of tracking any warplane irrespective of the configuration of its fuselage. The radar started to emit and we discovered a target at a distance of 15 kilometers – something that our operators were distinctly seeing on a display. I was quick to order the launch of a missile which destroyed the target."
http://en.wikipedia.org/wiki/P-18_radar
http://en.wikipedia.org/wiki/Zoltán_Dani
http://voiceofrussia.com/2012_03_24/69369732/
