The measurement of the lateral deviation of radio waves by means of a spaced-loop direction-finder

The paper gives an account of some systematic measurements of the lateral deviations of wireless waves received at Slough from various short-wave transmitters over a period of several months. The measurements were made by means of a spaced-aerial direction-finder of the four fixed-loop type, and the first part of the paper is devoted to a description of the apparatus, together with an account of its performance in respect of instrumental accuracy, pick-up factor, and other characteristics. The second part of the paper describes the measurements themselves, which were made photographically from a cathoderay oscillographic goniometer. Some of the observations were made on pulse transmissions from Nauen (¿ = 30 m.) and Dorchester (¿ = 37.3 m.), and the remainder on continuouswave transmissions from Zeesen (¿ = 31.4m.), Prague (¿ = 44.6 m.), and various American stations. The results obtained show that the variations in bearings which arise from instrumental causes do not exceed about 2°, and are usually of the order of 1°. The records demonstrate that lateral deviation occurs for the above cases to an extent which depends on the range and type of the reflected waves observed. Deviations of 10° to 20° were recorded from the more distant stations, while in the case of Dorchester, distant 160 kilometres, the deviations were as much as 50° on occasions. From a study of these observations it is concluded that the effective points of reflection at the ionosphere may be as much as 50¿100 km out of the great-circle path.