In the field of High Frequency Surface Wave Radar (HFSWR), this paper deals with a study which determines the electric permittivity and conductivity values that a medium must hold to propagate a sole surface wave at its interface with air. Firstly, we demonstrate clearly the reason why the Zenneck Wave cannot be excited on sea surface. Kistovich decomposition is used for this purpose. Secondly, the reasoning is extended to identify electric permittivity and conductivity values that permit to excite a surface wave on an homogeneous medium. Finally, numerical validation is obtained by comparison with the analytic formulation of the field radiated by a vertical Hertzian dipole as it has been established by Norton.