A radio-frequency telephone set including (a) a powered antenna element having a power supply portion, and (b) a substrate having a dielectric layer, a first conductive layer formed on one of opposite surfaces of the dielectric layer, and a second conductive layer formed on the other of said opposite surfaces, wherein the first conductive layer includes a conductive pattern having opposite end portions one of which is electrically connected to the power supply portion, and further having a land electrode electrically connected to the other end portion, and the second conductive layer includes a ground electrode and a conductor-free portion defined by said ground electrode, the land electrode and the conductor-free portion at least partially overlapping each other as viewed in a direction perpendicular to the plane of the dielectric layer.