Application of Frequencies above 30,000 Kilocycles to Communication Problems

The authors briefly describe the results of a number of experiments with frequencies above 30,000 kc covering a period of several years. Since the major interest of radio communication companies has been in long-distance communications, this paper includes some qualitative data covering propagation beyond the optical, or direct vision, range. The authors have found that the altitude of the terminal equipment location has a marked effect on the signal intensity, even beyond the optical range. Frequencies. below about 43,000 kc appear to be reflected back to earth at relatively great distances in the daytime in north-south directions, but east-west transmission over long distances is extremely erratic. Frequencies above about 43,000 kc do not appear to return to earth beyond the ground wave range, except at rare intervals, and then for only a few seconds or a few minutes. These frequencies, which do not return to earth, also appear to be free of echoes and multiple path transmission effects. Therefore, they are free from distortion due to selective fading and echoes. The range is also limited to the ground wave range, so these frequencies may be duplicated at many points without interference. As the frequency is raised, the range tends to approach the optical distance as a limit. Experiments with frequencies above 300,000 kc have, so far, indicated that the maximum range is limited to the optical distance. A number of possible applications are suggested, based on the unique properties of these frequencies.