Abstract: The invention relates to ultra-high frequency filters with variable capacitance tuning devices tunable in a wide frequency range.Each tuning device comprises two coaxial fingers, namely a fixed finger and a finger movable in the filter body. One of these fingers is hollow and the other has a tuning plunger, whose end is cylindrical and which is displaceable, e.g. by screwing in the body of the finger. The minimum capacitance obtained with a minimum penetration of the plunger, its end being level in the vicinity of the end of the corresponding finger, is adjustable by displacing the movable finger relative to the fixed finger. The supplementary variable capacitance is obtained by plunging the tuning plunger into the hollow finger.

Abstract: The tuning device comprises a hollow cylindrical part and a moving rod which penetrates a cavity by passing from one side to the other of the hollow cylindrical member. This cylindrical member is fixed and integral with the cavity. It has an end located within the cavity, the end being longitudinally cut to form n slots (n being an integer greater than 1) for forming n elastic members, which are covered with an electrolytic silver deposit. Joined silver contacts are welded to the end of the elastic members to provide the contact with the moving rod and prevent poor conduction of surface currents due to wear to the electrolytic deposit at the contacts.