It was proposed [1] that an unsymmetrical surface wave propagating radially over a flat surface and having an azimuthal dependence of the form Sin

is a valid solution of Maxwell\´s equation and the value of the reactance required for the support of the wave is independent of the order of the mode. In this communication the radiation properties of a new type of surface wave horn antenna using unsymmetrical radial surface wave, by coating a thin layer of dielectric, such as Teflon, over a conductive layer of the H-plane sectoral horn has been described. The structure considered here is shown in fig.(1). The reactive surface of surface reactance, say

is confined between two vertical conducting planes at an angle of

with each other. The vertical plates has been truncated at a suitable height where the field concentration is almost negligible. The structure considered, may be noted, has no cover at the top, being a surface wave structure.