GB627340A - Improvements in or relating to tunable electric resonators - Google Patents

Abstract

627,340. Variable condensers. PHILIPS LAMPS, Ltd. March 13, 1947, No. 7051. Convention date, June 2, 1944. [Class 37] [Also in Group XL (b)] A variable condenser for tuning a cavity between an inner conductor 1 and an outer conductor 2 includes an electrode 6 having a plurality of rings of different heights surrounding one another, the height of the rings increasing with the radius of curvature. The rings which may either take the form of a series of coaxial cylinders or of a continuous spiral are arranged to move into corresponding spaces between rings 4 of uniform height which form the second electrode, the degree of penetration being controlled by a porcelain rod 9 acting on the base-plate 12. With such a construction when the condenser is set to have a small capacity, the charging current in flowing radially inwards passes a minimum number of junction seams 13 between the base-plate and the electrode rings, thereby minimizing the ohmic loss. The rings may be fixed on the base-plates 5, 12 by soldering or welding. Alternatively, the electrode may comprise a number of cylinders threaded at one end and screwed together to form a coaxial assembly. A spiral type of electrode may also be made by coiling a profiled metal strip having a narrower strip overlaid along one edge, the thickness of the latter determining the spacing of the successive turns of the spiral.