Some Results of a Study of Ultra-Short-Wave Transmission Phenomena

The results of a series of transmission experiments made in the range 3.7 to 4.7 meters and over distances up to 125 miles are reported. These observations were chiefly confined to the region reached by the directly transmitted radiation and are found in good agreement with the assumption that such transmission consists mainly of a directly transmitted radiation plus the reflection components which would be expected from the earth's contour. The residual field not thus explained consists of a more or less pronounced diffraction pattern due to the irregularities of the earth's surface. A hill-to-hill transmission has three demonstrable reflection surfaces. Quantitative checks on hill-to-hill transmission have been obtained and it has been found that a field intensity of 40 microvolts per meter gives very good transmission. Static is ordinarily entirely absent and no Heaviside layer reflections have been observed. The almost universal standing wave diffraction patterns have been studied and sample records are given. The methods of measuring field intensity which we have used are described in an appendix. No long range transmissions, such as harmonics of distant (greater than 500 miles) short-wave stations would yield, have been observed.