AI-6
LOWEST USABLE FREQUENCY—The minimum operating frequency that can be used for
communications between two points.
LUMPED CONSTANTS—The properties of inductance, capacitance, and resistance in a transmission
line.
LUMPED-IMPEDANCE TUNING—The insertion of an inductor or capacitor in series with an antenna
to lengthen or shorten the antenna electrically.
MAGNETIC (H) FIELD—The field produced when current flows through a conductor or antenna.
MAJOR LOBE—The lobe in which the greatest amount of radiation occurs.
MARCONI ANTENNA—A quarter-wave antenna oriented perpendicular to the earth and operated with
one end grounded.
MAXIMUM USABLE FREQUENCY— Maximum frequency that can be used for communications
between two locations for a given time of day and a given angle of incidence.
MEDIUM—The substance through which a wave travels from one point to the next. Air, water, wood,
etc., are examples of a medium.
MINOR LOBE—The lobe in which the radiation intensity is less than a major lobe.
MULTIELEMENT ARRAY—An array consisting of one or more arrays and classified as to directivity.
MULTIELEMENT PARASITIC ARRAY— An array that contains two or more parasitic elements and
a driven element.
MULTIPATH—The multiple paths a radio wave may follow between transmitter and receiver.
NATURAL HORIZON—The line-of-sight horizon.
NEGATIVE ALTERNATION—The portion of a sine wave below the reference line.
NODE—The fixed minimum points of voltage or current on a standing wave or antenna.
NOISE (OF SOUND)—An unwanted disturbance caused by spurious waves that originate from man-
made or natural sources.
NONDIRECTIONAL—See OMNIDIRECTIONAL.
NONLUMINOUS BODIES—Objects that either reflect or diffuse light that falls upon them.
NONRESONANT LINE—A transmission line that has no standing waves of current or voltage.
NORMAL—The imaginary line perpendicular to the point at which the incident wave strikes the
reflecting surface. Also called the perpendicular.
NULL—On a polar-coordinate graph, the area that represents minimum or 0 radiation.
OMNIDIRECTIONAL—Transmitting in all directions.
OPAQUE—A type of substance that does not transmit any light rays.
OPEN-ENDED LINE—A transmission line that has an infinitely large terminating impedance.
