On the Attenuation of Wireless Signals in Short Distance Overland Transmission

It is pointed out that the signal strength of a wireless wave at a distant point depends on: (a) the electrical constants of the ground, (b) the curvature of the earth, (c) the existence of an “atmospheric” ray coming downwards from the Heaviside layer. 2. We can eliminate the effect of (b) and (c), and so obtain direct evidence about the electrical constants of the ground, by making measurements near the transmitter. 3. Measurements on wave lengths of 300 m. and upwards give information about the resistivity of the ground, and on shorter wave lengths (15 m.) give the dielectric constant of the ground. 4. Attenuation measurements have been made over short distances for wave lengths of 1600 m. and 360 m. 5. The results are compared with those calculated from Sommerfeld's theory and show close correlation for distances beyond 10 wave lengths, but show deviations from the theory for shorter distances. They give as values for the resistivity of the ground p = 1·8 × 1013 E.M.U. for the Daventry signals, and p = 0·6 × 1013 E.M.U. for the London signals.