Cylindrical variable delay line - is formed by windings on cylindrical mandrel with longitudinal inlaid electrode

摘要

A variable delay line comprises a mandrel of insulating material (12) having a longitudinal electrode (14) inlaid along one generatrix. A coil (11) is wound around the mandrel between a pair of conaxial terminals (18) set in the extremities thereof. The coil is wound in alternating shapes of at least three turns (20, 21), which define a succession of zones so that a slider can select the delay from a stepped ramp type characteristic curve. A tupical design uses a mandrel of polycarbonate reinforced by a 20% content of glass fibre, the mandrel having an overall dia. of 6. 3 mm and a length of 68 mm and carrying a total of 764 coils of 0.06 mm dia. enamel wire. Such a coil has a delay of 330 ns. and an impedance of 100 ohms.