Very early reflex klystron designed by Robert Sutton of the Signal School group at Bristol University. The klystron was intended as local oscillator in the receivers of the planned 10-cm microwave radars.
Sutton oscillators are characterized by the deep drawn copper discs connected to the external resonating cavity and terminating in the horn-shaped interaction gap. The reflector is cup-shaped, likely to keep the electron beam focused.
According to Callick, an oscillator complete with external cavity first operated in September 1940. The development was completed with suitable external cavities by December 1940, Sutton oscillators operated at about 1750 V resonator voltage, giving about 10 mW in output. Two frequency variants were originated and manufactured through 1941, both commonly referred to as 'Sutton tube' or 'Sutton oscillator'. The NR89, later titled as CV10, was tunable around the frequency range of the NT98 magnetron. The Air Ministry 10E/501, later titled as CV11, was tunable around the range of the CV38 magnetron.
Sutton tube also originated the Canadian REL Type 8, with a simplified factory pre-tuned resonating cavity. Despite their unstable and critical tuning and the need for quite high resonator voltage, Sutton tube and its derivatives were the only reflex klystrons available as local oscillator in 10-cm radar receivers until the late 1941.
To an article on the development of early reflex klystron to be used as local oscillator in microwave radar sets.
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