Whip Antenna Design Calculator
A whip antenna also known as a monopole antenna looks capacitive if it is shorter than a quarter wavelength, and are tuned to resonance with a series inductor. PCB antennas are often shorter than a quarter wavelength due to board size restrictions and often fit into this category.
The capacitance is related by a formula and is a function of the percentage of wavelength. The matching inductor is chosen such that the antenna resonates at the desired frequency.When the antenna is perfectly tuned then it looks like a pure resistance tied to ground. This resistance is known as the radiation resistance.