taog wrote:don't you surprise that APG-81's amount elements ?
it look the before "+" mean ~400 units (1200+)
Not really as the technology level would also affect the element count (besides antenna area). Mid-late 1990's it was possible to put about high-power 2500 X-band T/R modules to a square meter. Currently it's possible to squeeze about 4000 high-power modules to a square meter, especially GaN modules. In the future the amount of modules is likely to increase as the T/R module size is decreasing with the use of GaN and better design and production methods (of both modules and overall antenna).
I think the pictures and the module count might well be accurate. APG-81 module count would be consistent with the approximate size of the antenna and current generation high-end T/R modules available. APG-77 module count would be consistent with it's antenna size and previous generation T/R modules. With current generation T/R modules it should be able to squeeze about 2500 modules to it.
I think APG-81 is way more capable radar than most people realize. Given the amount of modules, it could easily have way higher max output power than even the vaunted Irbis-E as that would require using only 12W T/R modules, which would be far from state-of-the-art. Currently there are up to 20W modules available in GaAs and GaN modules can have way more power than that (over 50W in X-band). It would not be impossible to have something like 40 kW of max output power. On the other hand the high number of T/R modules would make the radar very flexible and be capable of large number of simultaneous beams.