Abstract: Apparatus for an adjustable low-loss capacitor, which can withstand the application of high shock forces without a corresponding change in a preselected value of capacitance, is described. This capacitor has two sets of hollow cylindrical electrodes which are coaxially interleaved, with, more particularly, one set attached to a rotor unit and the other to a stator unit, all contained within a housing. The capacitance is varied by longitudinal, i.e., axial, movement of the rotor unit with respect to the stator unit. The rotor unit is threadedly inserted into a bushing. In addition, the rotor unit includes a frictional locking mechanism which comprises a threaded member which is inserted into a hole cut into the rotor unit and oriented substantially parallel to the center axis of the rotor. As this threaded member is turned, one portion of the rotor unit moves, with respect to another portion, in a longitudinal direction substantially parallel to a center axis of the rotor unit.