All modern (1980s and later) RWRs can determine the bearing of emissions. Heck, even the RWR in the Mig-21 (1950s plane) could determine bearing. With bearings

All modern (1980s and later) RWRs can determine the bearing of emissions. Heck, even the RWR in the Mig-21 (1950s plane) could determine bearing. With bearings known, all you need is two planes to determine location by taking the intersection of the two bearings. Most RWRs can also identify the type of radar, as well as whether it is searching or locked into a target. Planes can also equip targeting pods that have even more advanced passive sensors: https://en.m.wikipedia.org/wiki/AN/ASQ-213 https://en.m.wikipedia.org/wiki/AN/ASQ-213 Passive sensors have advanced significantly.