The attenuation of wireless waves over towns

This paper is supplementary to the paper on ¿The Attenuation of Wireless Waves over Land¿ which was read a year ago before the Wireless Section. It describes an experimental and theoretical investigation of the absorption of wireless waves produced by their passage over a town. In the course of the work the polar curve of signal intensity of 2LO was obtained and this curve was utilized to provide a revised signal-strength contour map of 2LO. Important differences between town attenuation and country attenuation are disclosed by the experiments. In particular, the absorption over the dense part of the town is found to increase extremely rapidly with the frequency of the waves. Aerials tuned for the reception of broadcasting in suburban districts are found to produce a critical effect on the attenuation in the neighbourhood of the common wave-length to which they are all tuned. Confirmatory experiments on short waves are described in an appendix, which also emphasizes the difficulty of calculating the resultant field strength in a region influenced by re-radiation from one or more receiving aerials.