The electric and magnetic fields of a linear radiator carrying a progressive wave

Abstract

The vector- and scalar-potential method of calculating electric and magnetic fields is applied to a straight conductor carrying a progressive wave of current. It is shown that unless the conductor is assumed to be terminated by charges which satisfy the condition of electrical continuity at the ends, the calculated field has an anomalous and impossible character. Such charges need not be included in the case of closed circuits of conductors carrying progressive waves. The mutual cancellation in such cases of the anomalous features associated with each linear element is confirmed by analysis of a particular case. It is pointed out that a linear progressive wave radiator has only one axis of symmetry, i.e. the radiator itself, differing in this respect from a standingwave radiator, which is symmetrical about the equatorial plane. The consequent asymmetry of the field from a progressive wave radiator is confirmed by analysis.The field system associated with a progressive wave of current is regarded as a more fundamental conception than that due to a standing wave, since any standing-wave system of currents is resolvable into positive and negative travelling waves. This feature is illustrated by the synthesis of the travelling wave fields into the known form for a dipole standing-wave radiator.The radiation resistance of a progressive-wave radiator is calculated by Pistolkors's method, and is shown to be equal to that for a standing-wave radiator when the length of radiator is an integral number of half wavelengths.