Admittance of infinite and finite cylindrical metallic antenna

A monopole antenna excited by a coaxial line is studied in detail. The mathematical model of the excitation is a magnetic ring current the radius of which may be larger than the radius of the cylinder. First a study is made of the waves guided by and radiated from an infinite cylinder. Numerical results for the current and the conductance are given. The conductance decreases when the gap width increases. The standing-wave antenna is treated with an assumed effective gap at the antenna ends. A solution of the antenna problem is found by superimposing the multiply reflected waves. In the solution, the effect of the gap and the antenna end separates. Accurate values for the gap admittance and the end admittance are derived from experimental values obtained by Hartig.