That long barreled goose gun ought to shut that thing the hell up. If you have the book on turning your microwave into a maser weapon you can just aim a bank of those at incoming drones at low altitude, like the ones organically fielded by the local po-po and shut those the hell up as well. A .50BMG rifle would work as well.

We'll run into trouble with the Predator and Reaper class drones. Those will require much more expenditure in air defense.