And presumably you have all the classified data on the T-50 radar operation. If it can sniff it out maybe it can track it to. If you don't know where to point them, how can you sweep any specific area with sharper sensors, unless the L Band provides this information somehow?
I don't know either because of the lack of data but it's a lot of effort to go to just to tell you that something is somewhere. Half decent intuition would tell you as much when in combat.