A control apparatus for controlling RF power supplied to first and second loads is provided. The control apparatus includes a first symmetric hybrid junction (36) having a first port (34) for receiving input RF power, a second port (42) coupled to a first load (14) and a third port (38) coupled to a dummy load (40). The control apparatus further includes a second symmetric hybrid junction (52) having a first port (50) coupled to a fourth port (44) of the first symmetric hybrid junction (36) and a third port (54) coupled to the second load (16). First and second variable short circuits (58, 62) are respectively coupled to second and fourth ports (56, 60) of the second symmetric hybrid junction (52). RF power reflected by the first and second variable short circuits (58, 62) is controllably directed through the second symmetric hybrid junction (52) to the second load (16). The amplitude and phase of the RF power supplied to the second load (16) can be controlled independently. In a preferred embodiment, the first and second loads (14, 16) are first and second accelerator guide sections (1, 2) of a linear accelerator (10), and the control apparatus (66) is used to control the output beam energy (20) of the linear accelerator (10).