We present an experimental procedure for dielectric characterization of liquid crystals in the frequency range 10(3)-10(10) Hz. This procedure is based an open-end strip line measuring cell and a 2D S.D.A. electromagnetic simulation software. Effective permittivities and tensor permittivity elements are determined for a commercial nematic liquid crystal. An application to an electrically tunable microwave phase-shifter is also presented. Transmission coefficient phase variations of about 0.5 degrees /cm length are obtained per GHz showing the liquid crystals potentialities for such applications.