What is the function of a loading coil in an electrically short antenna?

An electrically short antenna (one that is physically shorter than its natural resonant length, such as a short whip used for HF mobile) exhibits a high amount of capacitive reactance and a very low radiation resistance. To make the antenna system resonant and capable of accepting power from the transmitter at the desired operating frequency, a loading coil is added. The loading coil is an inductor, and its inductive reactance cancels out the antenna's inherent capacitive reactance, bringing the system to resonance. While the coil is necessary to achieve resonance and efficiently transfer power, it does not lower losses or lower the Q. In reality, loading coils typically introduce inherent resistive losses and raise the Q of the antenna system, which unfortunately narrows the SWR bandwidth.