Origin of Non-reciprocity on High-frequency Ionospheric Paths

Abstract

THE reciprocity theorem¹ is not generally true for electrical systems which include an ionospheric radiation link. This has been demonstrated on many occasions, particularly by recent investigators^2,3 who have observed periods of uncorrelated two-way fading of high-frequency pulse transmissions over ionospheric paths. However, in spite of the long-standing interest in the question of the applicability of the reciprocity theorem to ionospheric paths⁴, the origin and magnitude of non-reciprocity observed in high-frequency tests have not been accounted for. We have completed preliminary investigations which provide direct evidence that the polarization of antennæ and limiting wave polarizations are important factors in determining whether or not a high-frequency ionospheric path is reciprocal.