This invention relates to an output arrangement for electron beam tubes. The invention provides an electron beam tube, of the type for amplification of RF signals, comprising an electron gun (14), an interaction region (18) within a vacuum, an RF input (7) and an RF output arrangement. The RF output arrangement comprises an output coaxial line (38) and a coaxial divider (32), the coaxial divider being arranged to divide a signal on the coaxial line into a plurality of signals. The vacuum within the interaction region extends into the coaxial divider, allowing both the size and mass of the divider to be greatly reduced.