A method is described of combining two or more carrier signals, which may be from a space-diversity aerial system, in such a way that the output power is always the sum of the individual signal powers. This gives the optimum signal/noise ratio under the commonly assumed Rayleigh distributed fading conditions.The control signals are taken from the i.f. amplifier of the main receiver; no extra detecting facilities are therefore required. However, a standby receiver can be incorporated, and the combiner can easily be adapted to act as a change-over switch, if required.