How did Hertz manage to obtain electromagnetic waves with the help of a vibrator and a resonator?

Due to the fact that changes in the magnetic field occur when the current strength in the conductor changes, i.e. when the charges move with acceleration, then electromagnetic waves should arise with the accelerated movement of electric charges.In Hertz’s experiments, the accelerated movement of charges was excited in two metal wires (rods ) with balls at the ends. Metal rods with balls at the ends and an air gap between them represented a radiating oscillatory circuit — a vibrator. If both parts of the wire were charged with opposite charges, then at a certain voltage a spark would jump between its ends. At the same time, the electric circuit was closed, and oscillations of electric charges appeared in the open oscillatory circuit, which rapidly moved along the conductor. This led to a change in the electric field around them and the appearance of an alternating magnetic field. To detect the electromagnetic volts emitted by the vibrator, a resonator was used, which was designed in the same way as the vibrator. In Hertz’s experiments, it was a wire bent in the form of a rectangle or a ring (a coil of wire), in which there was also a spark gap. Hertz discovered that under the action of the electric field of an electromagnetic wave, forced electromagnetic oscillations arose in the resonator. When resonance is reached, their amplitude reaches a value at which a spark may appear in the spark gap of the resonator.