Elint page in Kneeboard
Information recorded from the RWR is used as well, so you don't need to carry the U22/A. The jammer are otoh able to detect more types of emitters (like CW-radars). The U22/A only detects in the front.
The more emissions that are recorded, the better the accuracy will be, as long as you change your own position. Best is to circle the area, and (if possible) to get close to the emitter to yield the most accurate position-estimation.