Noise figure calculation and measurement for low-power crossed-field amplifiers

Some measurements that have been made in our laboratory indicate that it is possible to make crossed-field amplifiers with moderately low noise figures without any special noise-reduction transducers [1]. This can be compared with the situation in an O-type tube where again no effort has been made to make an especially low-noise tube. In both cases the noise figures which would be obtained are of the order of 25 dB. The measurements we have made lead us to believe that the crossed-field amplifier is not necessarily noisy and also have led us into considering possibilities of making ultra-low-noise amplifiers. This paper contains more of our measurements and also some theoretical work in which we have investigated the effect of changing the drift space between the gun and the interaction region.