Abstract :
The salient results are brought together of a number of experiments on the propagation of radiation of a wavelength of 9.2 cm, carried out during 1943¿44. All the measurements described were made over land, some over open country and some over transmission paths which were obstructed by various obstacles. The obstacles included trees, both leafless and in full leaf, brick walls, windows, and other parts of buildings. Many of the obstacles caused such large attenuations that they should generally be regarded as opaque objects round which diffraction takes place. Stone buildings, groups of trees so dense that the sky cannot be seen through them, and the trunks of trees come into this category. Semi-transparent obstacles (causing a loss of signal of 10 db or less), include windows, tile or slate roofs, the sides of a light wooden hut, and thin screens of trees when the transmission path lies through the branches.
