I couldn't answer you exactly here, because I'm now behind the time. I'm now some years out of military and I never worked with digital PESA or AESA radar, only with analogue mechanical one generation from eighties. But I think some things are the same.
You have to know, that radar signal, which go from emitter become weaker, before it reach target and than signal, which go back from target to receiver again become weaker. Ergo, if RWR detector is the same sensitive as is radar receiver, than could detect radar emissions in twice of radar range. It only depend in which frequencies it listen. The jammer is most effective, when its emitting in the same frequency is stronger, than signal, which radar send and come back from target. As I hear in past it was a big problem with OSA (SAM-8 ), that it was actually unjammable, because it have so high power radar, that jammers on planes could not overcome with noise the power of returning signal. But it need very skilled operators, who know to look in crude radar picture.
AESA and PESA radars have lower power signals, so old RWR detectors could not register them and ignore hem as noise. But newer RWR detectors sensitivities could be suited for those radars. Jammers could easily overcome with power of noise the power of returning signal, but AESA and PESA radars could easier change frequencies with frequency hoping, so the jamming noise is not in the proper frequency as returning signal and radar then easily ignore jamming noise in wrong frequency and see target. But in peace time all radars work only in peace time frequency without hoping. But I think modern radars with modern digital computers could quite effectively do with jamming in constant frequency with coding signals.