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The experimental results of a program of study on low-noise traveling-wave tubes for 9,000 mc are described. Tests of tubes utilizing velocity jumps for noise reduction show that a single, gradual jump upward in voltage results in the best noise reduction. The design of a tube having 11.3 db noise figure and 18 db gain at 9,000 mc is given. Curves for the variation of noise figure with magnetic field, operating voltages, and cathode temperature are presented. The experimental results obtained from measuring the noise figure of some of the tubes at different frequencies suggest an empirical modification of the simple theory.