September 1970 | NTIA Technical Memo ERL TM ITS 250
Further HF tests on the Wyoming buried dipole
D. C. Crombie
Abstract: Tests of the radiation efficiency of a dipole antenna 100 ft. long and buried in Sherman granite are described. The measurements were taken under winter conditions as a comparison with earlier measurements made in summertime; this determines whether any appreciable alterations occur due to climactic conditions. The results of a measurement of the sky wave-to-ground wave ratio at 3375 kHz over an 18 km path are also given. The efficiencies measured at 2.0 and 7.975 MHz are comparable. For reasons that are not understood, the winter efficiency at 3.375 MHz is about 11 times greater than the summer efficiency. The distance at which the ground wave and sky wave signals are nearly equal, resulting in severe multiplicative noise or selective fading, occurs in the range of 10 to 30 km at 3375 kHz.
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