Directional transmission of electromagnetic waves for navigational purposes

The paper criticizes the differences between directional transmission and reception as used in navigation and describes in particular a number of directional transmission methods which have been developed by the Royal Air Force. These methods include several in which the determination of a bearing depends on the timing of the moment of equality of signals as heard in the receiver, and also include a new class of directional transmitters in which a characteristic of the radiation, such as a particular wave-length, is alloted to each direction in azimuth.