Reflex klystron

The reflex klystron is a type of vacuum tube used to generate microwaves. It is a low-power device used mainly to provide a tuneable low-power frequency source for the local oscillators in the receiver circuits of radar sets, and with minor modifications as a switch that could turn another microwave source on and off, a use known as the soft Sutton tube or rhumbatron switch. The first reflex klystron, called the Sutton tube, was developed in 1940 by Robert W. Sutton of the Signal School group at Bristol University, who was asked to make a tuneable version of the klystron designs developed in the United States in the late 1930s. By placing a reflector at the far end of the tube to turn the electrons back toward the gun, a single resonator could do the work of two cavities, and the frequency could be tuned by changing the reflector voltage. Sutton tubes were widely used in microwave radar during World War II and through the 1960s, until solid state devices such as the Gunn diode took over their role.