Abstract: A strip transmission line for guiding a wave therein, including a strip-shaped inner conductor; an outer conductor surrounding the inner conductor with a clearance; a ferrite coating carried on at least one of the conductors; and at least one throughgoing slot provided in the inner and outer conductors for dividing the inner and outer conductors into at least two inner conductor sections and at least two outer conductor sections. The slots extend in a direction of wave propagation, whereby a variable current applied to the inner and outer conductors flows in one direction in one of the inner and outer conductor sections and returns in an opposite direction in another of the inner and outer conductor sections for generating a variable premagnetizing field within the strip transmission line between the inner and outer conductors to vary an electric length of the strip transmission line.