The insulated monopole: Admittance and junction effects

Recent theoretical and experimental studies of the insulated linear antenna in a relatively dense ambient medium are reviewed briefly. Attention is then directed to a description of the admittance and impedance of air-insulated monopoles as determined by theory and by measurements when two quite different junctions between the antenna and the feeding coaxial line are used. Graphs of the admittances of antennas with three different thicknesses of the insulation and lengths up to a wavelength are shown. No theory of the junction effects or simple corrective network is provided, but it is shown that with proper design of the junction region, the uncorrected (ideal) theoretical admittances are satisfactory approximations of measured values.