This paper deals with an investigation into some theoretical and practical aspects of the partial suppression of one or both sidebands of a modulated carrier wave. The work is primarily of interest in connection with asymmetric-sideband television broadcasting channels.The envelope distortion and carrier phase modulation produced by a channel of asymmetric characteristics are derived, and experiments are described which demonstrate some of the effects in such channels. A method is described of obtaining the “equivalent modulation characteristics” of an asymmetric-sideband channel, which is exact for all types of modulation envelope at any modulation depths. In the analysis quite general channel characteristics are assumed, and not “idealized” forms.