The AN/APG-66 can detect a phantom sized target at 40 nm...
translate that to figure we can use... roughly 74 km for a target with an RCS >6m2.
Given that^ the KLJ-7 is superior to the AN/APG-66, and superior to the improved AN/APG-66(v)2 with 25% greater detection range.
The AN/APG-68(v)5/7/9 have greater detection ranges then the KLJ-7.
The APG-68(v)5 has a detection range of 130km for a target with an RCS of 5m2.
I will clarify a bit on how to interpret these claims.
A radar cross section (RCS) is a 'fictitious' value, meaning it can and does change. Currently, the official unofficial standard for any credible targeting purpose is 1 m/sq at about 100-150 km distance out. That is derived from a clean F-16. An RCS value is calculated from many factors but the main ones are illustrated below...
When we get into other radar transmission characteristics such as 'continuous wave' or methods of exploitation such as 'bi-static' then the issue of RCS gets much murkier, but for now, we can stay with the above popular method of pulsed characteristic and mono-static method. It is about 80% of the world's radar systems, from civilian to military use.
Can a B-52 have an RCS of 1 m/sq? Yes, but at several hundreds km distance out. So at the expected 100-150 km, the B-52 would produce dozens of m/sq from the frontal aspect alone. For a clean F-16 at that distance, the radar would experience periods of ambiguity due to background clutter processing and could (but not always) miss the F-16 from one moment to the next. That is why even when fully loaded 'for bear' the F-16 always proved to be problematic for opposition aircrafts in the radar front.
So when we talk about differences in radar systems, it is always good to have a fixed distance for
ALL aircrafts, such as 100 km or 300 km, with the guesstimated different RCS values for each aircraft. Or to set a fixed RCS value for
ALL aircrafts, such as 1 m/sq or 10 m/sq, with the guesstimated different distances for each aircraft.
Remember this truth:
EVERY body under radar bombardment will produce different RCS values at different distances.
Can an F-22 produce a 100 m/sq RCS value? Yes, but pretty much right 'in your face' distance and with pretty much every fighter-class radar systems out there.