Characteristics of Electromagnetic Radiation from Aircraft in Flight

This paper reports the results of an investigation of the effects of altitude, frequency and distance upon the strength of a received radio signal as transmitted from an airplane in flight and received at a point on the earth's surface. Frequencies between 475 kc. and 5,500 kc. are reported on for altitudes up to 6,000 feet and distances up to 60 miles. Representative curves, plotted between the above mentioned variables, are included and the difference in results obtained during daylight and darkness are shown. In general, the data show that, within the limits of this investigation, the higher the frequency the shorter the reliable communication range becomes. An appendix is included in which is shown how the data for a given altitude, distance and frequency may be used to calculate the theoretical field strength for the given frequency when the transmitter (or airplane) is at a different distance and/or altitude.