--------------- Funny how they're ALWAYS "in development" and have BEEN so for more than 30 YEARS! Sort of like other Tesla-fanatic inventions. The simple fact is that you can focus a shitload of RF at something with a dish, but it falls off faster than 1/r^2 because it's subject to HUGE f-stop aperture considerations unless the dish is enormous, requires a LOT MORE energy than merely blowing the hell out of it with a shell or missile, or even a huge blast-in-range, and can be deflected with 30 cents worth of Aluminum foil or Aluminum paint inside cheap plastic.
Otherwise you're talking solely about ranges of a few feet because you want specifically to target electronics, instead than merely blowing out the tires.
Even a maser is subject to reflection, and really BIG EMP weapons are merely explosives which are better used ballistically.
-Steve