An RF apparatus may include: an RF resonance device having an electrically conductive outer wall, the outer wall comprising a gap extending over its circumference, and an input coupling device having an RF generator, arranged on the outer side of the outer wall of the RF resonance device in the region of the gap, for coupling RF radiation of a particular frequency through the gap into the interior of the RF resonance device, and shielding which externally shields the generator and electrically bridges the gap on the outer side of the outer wall, wherein the shielding is formed as a resonator having a high impedance at the generator frequency.