HF radar and communication systems take advantage of surface wave propagation at the interface of the sea to overcome the radioelectric horizon limitation. The paper reviews electromagnetic fields excited by a vertical electric dipole over both a flat and a spherical Earth in order to focus on the surface wave. In a first time, classical Norton and Zenneck results are discussed and compared with a modal decomposition technique for a plane interface. Secondly, the field on a spherical Earth is considered. Fock formulation is applied in the last part of this communication. Even if the expressions of these fields are not similar, the results are in good agreement. This make the way for analytic isolation of surface wave contribution whatever the antenna design.