Microwave Power Modules (MPMs) consisting of, at least, a travelling-wave ‘vacuum electronic device’, a ‘Monolithic Microwave Integrated Circuit’ (‘MMIC’) and an integrated electronic power conditioner and having all of the following: (a) A ‘turn-on time’ from off to fully operational in less than 10 seconds; (b) A volume less than the maximum rated power in watts multiplied by 10 cm 3 /W; and (c) An ‘instantaneous bandwidth’ of greater than 1 octave (f max > 2f min ) and having any of the following: 1. For frequencies equal to or less than 18 GHz, an RF output power greater than 100 W; or 2. A frequency greater than 18 GHz; Technical notes: 1. To calculate the volume in item b. above, the following example is provided: for a maximum rated power of 20 W, the volume would be: 20 W × 10 cm 3 /W = 200 cm 3 . 2. The ‘turn-on time’ in item a. above refers to the time from fully off to fully operational, i.e., it includes the warm-up time of the MPM.