Disclosed is a multiband jamming antenna for use with RF jamming systems. An exemplary embodiment of the antenna comprises high-band, medium-band and low-band radiating structures arranged in a collinear manner. The three radiating structures are operable in three respective overlapping frequency bands. In the exemplary embodiment, the high-band radiating structure comprises a hybrid biconical/dipole antenna disposed at an upper end of the antenna. The medium-band radiating structure is collinearly coupled to the high-band radiating structure and comprises upper and lower dipole elements that are tuned using a dual section coaxial transformer. The low-band radiating structure is collinearly coupled to the medium-band radiating structure. The low-band radiating structure comprises a coaxial Ruthroff UNUN transformer that is coupled to the low-band radiating structure, and a feeder cable that connected to the coaxial Ruthroff UNUN transformer, and the high-band, medium-band, and low-band radiating structures.