Antenna Werks - Coils Are Inductors
Here is a brief discription on how the coils shown here, perform as part of an mobile antenna system.
The coil or inductor as part of the HF antenna, resists changes in the electric current passing through it. When current flows through it, energy is stored temporarily in a magnetic field in the coil. When the current flowing through an inductor changes, the time-varying magnetic field induces a voltage in the wire.
Wire will generate a magnetic field when current flows through it, so every wire has some inductance. The inductance of the circuit depends on the geometry of the current path as well as the magnetic permeability of nearby materials, such the mounting hardware at the top and bottom of the coil.
In inductors and in this case the antenna coil, utilizing wire of a larger gauge will increase the magnetic field. Winding the wire into a coil increases the number of times the magnetic flux lines link the circuit, increasing the field and thus the inductance. The more turns, the higher the inductance. The amount of inductance also depends on the shape of the coil, as well as the separation of the wire turns on the coilform.
The coils in this photo, one shown complete and the other incomplete, were built for the 17 meter band, and they have an inductance of 4 uH as required for my latest antenna design, and proofed with my antenna analyzer.