Input Admittance of Infinitely Long Dipole Antennas Driven from Coaxial Lines

For an infinitely long dipole antenna driven from a coaxial line, the reflection coefficient and hence the apparent terminal admittance are determined approximately when the radii of the coaxial line are small compared with the wavelength. This result is useful because the differences of admittances for antennas with identical geometries near the driving point are less sensitive to the driving condition and hence can be found approximately by many existing theories.