The external radiation conductance

of narrow half-wave axial and transverse slots on a circular cylinder, a ribbon, a knife edge, and a right-angle wedge are computed. The method is based on finding the total power radiated assuming a sinusoidal variation of voltage along the slot. The theoretical values of

for the ribbon of width

are applied to the case of a half-wave slot cut in the narrow face of a rectangular waveguide which has a flush mounted plate or flange of width

.