Abstract :
Types of crystal valves which were designed during the war are discussed and criticized, with a view to their use in the frequency bands from 20 000 to 60 000 Mc/s. A new design of a waveguide plug-in crystal valve, evolved as a result of these considerations, is then described. Crystal valves to this design were made initially by the author using silicon taken from 1.25-cm rectifiers. Later the design was developed by two manufacturers working on Admiralty contracts, and a summary is given of the experimental data obtained on these crystals. A fairly large number of crystal valves have now been made, and the data confirm the advantages of this design. The factors involved in the choice and treatment of the semiconductor are not discussed, since the first essential was to produce an efficient millimetre-wave component.
