An antenna loading coil is an inductor placed in series with an antenna element in order to lower the antenna’s resonant frequency. A standard dipole antenna is resonant if constructed with a length of one-half wavelength. A vertical antenna (effectively half ... Read More
It could also be an impedance match that connects one part of the antenna, that might be of a 3/4 wavelenght, to a 1/4 wave part. It could also be a phase shift coil to make different antenna parts work together in phase and add gain.