In order to make it possible to direct sufficient microwave energy at a target with an electronic device which is to be interfered with or to be destroyed, the beams (7) from at least two antenna arrays (10) are focused on an effective area (8) in the vicinity of that target, preferably from a vehicle (3) which is equipped with these arrays (10). For effective super-imposition of the emitted microwave energy (7) in the emission direction of in each case one of the arrays (10), the use of an arc for discharging the capacitance (43) of the resonator via its spark gap (13) is observed, and is recorded quasi-continuously optoelectronically. The electrode separation of the spark gap (13) or the fluid pressure of the dielectric in the vicinity of the spark gap (13) is then varied by control elements such that all of the spark gaps (13) in an array (10) ignite virtually at the same time, so that their discharge current pulses which lead to the emission of the microwave energy (7) start virtually in phase.