Measured admittances of electrically thick monopoles

Extensive measurements of admittances are reported for electrically thick cylindrical monopoles driven from coaxial lines over a large ground plane. The monopoles have circular cross sections with radii in the range froma/lambda = 0.039to 0.140 or circumferences from approximately0.25lambdato0.88lambdawherelambdais the wavelength. Results are given for tubes with open ends, flat metal ends, and ends with hemispherical caps. Graphical representations of the measured values are given over a range of lengths of the monopoles extending fromh/lambda = 0.05toh/lambda = 1.0. The ratios of the radii of the outer to the inner conductor of the coaxial lines used are near 1.2. Comparisons with available theory are considered briefly together with the related problem of end correction for the coaxial line.