RF amplification system includes a power cavity and a coupling loop operably positioned within the power cavity between an inner conductor and an outer conductor. The coupling loop includes a secured segment that is coupled to the grounding deck and a movable segment that is coupled to the secured segment. The secured segment extends between the grounding deck and the movable segment. The coupling loop defines a loop region that correlates to an amount of inductive coupling between the coupling loop and magnetic field within the power cavity. The movable segment is movable relative to the secured segment while the secured segment is stationary to change a size of the loop region and thereby change the amount of inductive coupling.