The Determination of the Direction of Arrival of Short Radio Waves

In this paper are described methods and technique of measuring the direction with which short waves arrive at a receiving site. Data on transatlantic stations are presented to illustrate the use of the methods. The methods described include those in which the phase difference between two points constitutes the criterion of direction, and those in which the difference in output of two antennas having contrasting directional patterns determines the direction. The methods are discussed first as applied to the measurement of a single plane wave. Application to the general case in which several fading waves of different directions occur then follows and the difficulties attending this case are discussed. Measurements made with equipment responsive to either the horizontal or the vertical component of electric field are found to agree. The transmission of short pulses instead of a steady carrier wave is discussed as a means of resolving the composite wave into components separated in time. More detailed and significant information can be obtained by this resolving method. The use of pulses indicates that (1) the direction of arrival of the components does not change rapidly, and (2) the components of greater delay arrive at the higher angle above the horizontal. The components are confined mainly to the plane of the great circle path containing the transmitting and receiving stations. A method is described in which the angular spread occupied by the several component waves may be measured without the use of pulses.