Antenna terms, and definitions

Impedance: The total opposition offered by a circuit or component to the flow of alternating current.

Impedance match: The condition where the load impedance equals the characteristic impedance of a transmission line.

Inductance: The natural property of an electrical circuit which opposes the rate of change or current, i.e., electrical intertia.

In phase: Two or more signals of the same frequency passing through their maximum and minimum values of like polarity at the same instant.

Insulator: A device or material that has a high electrical resistance; a nonconductor of electricity.

Interference: A degradation of a received signal caused by another transmitter, a noise source, or the desired signal propagation over two or more different routes.

Inverted L antenna: A half-wave dipole fed by a one-quarter wavelength long vertical section.

Inverted vee antenna: A half-wave dipole erected in the form of an upside-down vee, with the feed point at the apex. It is essentially omnidirectional, and is sometimes called a dropping doublet.

Ionization: The process where radiation and particles from the Sun make some of the Earths atmosphere partially conductive.

Ionosphere: A partially conducting region of the Earths atmosphere between 50 kms and 400 kms high.

Lambda: Greek lower case letter. Used to represent a wavelength with reference to electrical dimensions in antenna work. linearly polarized antennas, Antennas that produce only one polarization.

Line of sight: [LOS]. The transmission path of a wave that travels directly from the transmitting antenna to the receiving antenna.

Load: A device that consumes electrical power.

Loading: Providing or connecting an electrical device capable of accepting power to match the impedance of an antenna to a transmitter so that maximum power is radiated from a generating device, such as a transmitter.

Lobe: A bulge on an antenna radiation pattern which indicates the direction in which radiated power is concentrated.

Log-Periodic (LP) Antenna: A broadband, multielement, unidirectional, narrow-beam antenna that has impedance and radiation characteristics that are regularly repetitive as a logarithmic function of the excitation frequency.

Long-wire antenna: An antenna that is a wavelength or more long at its operating frequency. An end fed single wire antenna usually one wavelength or longer. An area of a radiation pattern plotted on a polar-coordinate graph that represents maximum radiation.

Lowest usable frequency: [LUF]. The lowest frequency that will not be absorbed by the ionosphere or smothered by atmospheric noise.

Antenna "M" Terms and definitions