Manufacture of quartz crystal filters

Quartz crystal filters used in modern carrier systems present new problems in manufacturing technique. In the assembly and testing of the filters and in the production of component crystals, coils and condensers, special factory facilities are required for accurate measurement of frequency and control of atmospheric conditions. The manufacture of quartz crystal plates in particular combines several fields of applied science, including crystallography, precision grinding, vacuum technique and high frequency electrical measurement. Inductance coils and fixed and variable condensers for use in crystal filters must consistently meet advanced requirements, especially in regard to stability. The assembly of these components into filters resembles the manufacture of radio receivers, differing mainly because of smaller quantity requirements. Testing equipment must permit rapid shop adjustment and test of the completed filters with laboratory precision.