[Blackadam] The J/APG-1 is an active phased array radar developed to equip the Japanese Air Self-Defense Force (JASDF) F-2 fighter aircraft. The J/APG-1 radar only has a detection range of 40 kilometers due to problems caused by the interferences coming from the interaction of the body and the radar’s antenna. This radar system entered service with the F-2 jet in 2002.

That was what performance was rumoured to be when it was first put into service in 2000, without being fully developed. 2002 may have been when the glitches had been ironed out. AFAIK the Japanese haven’t published range figures.