Shows the possibility of generating magneto-active plasmas in a waveguide by the use of electromagnetic waves launched transversely to the static magnetic field for ordinary and extraordinary polarisation. With extraordinary polarisation, plasmas of densities of about 1017 m-3 can be obtained at low power levels. The working gas was argon and the static magnetic field about 0.09 T. Plasma density is limited by the frequency of the incident waves (2.45 GHz in the authors' case) and not by the mechanism of wave transformation.