AI-7
OPTIMUM WORKING FREQUENCY—The most practical operating frequency that can be used with
the least amount of problems; roughly 85 percent of the maximum usable frequency.
ORIGIN—The point on a graph where the vertical and horizontal axes cross each other.
OUTPUT END—The end of a transmission line that is opposite the source.
OUTPUT IMPEDANCE—The impedance presented to the load by the transmission line and its source.
PARALLEL RESONANT CIRCUIT—A circuit that acts as a high impedance at resonance.
PARALLEL-WIRE—A type of transmission line consisting of two parallel wires.
PARASITIC ARRAY—An array that has one or more parasitic elements.
PARASITIC ELEMENT—The passive element of an antenna array that is connected to neither the
transmission line nor the driven element.
PERIOD—The amount of time required for completion of one full cycle.
PITCH—A term used to describe the frequency of a sound heard by the human ear.
PLANE OF POLARIZATION—The plane (vertical or horizontal) with respect to the earth in which the
E field propagates.
POINT OF ZERO DISPLACEMENT—See REFERENCE LINE.
POLAR-COORDINATE GRAPH—A graph whose axes consist of a series of circles with a common
center and a rotating radius extending from the center of the concentric circles.
POSITIVE ALTERNATION—The portion of a sine wave above the reference line.
POWER LOSS—The heat loss in a conductor as current flows through it.
POWER STANDING-WAVE RATIO (PSWR)—The ratio of the square of the maximum and
minimum voltages of a transmission line.
PRIMARY COLORS (OF LIGHT)—The three primary colors of light (red, green, and blue), from
which all other colors may be derived.
PRISM—A triangular-shaped glass that refracts and disperses light waves into component wavelengths.
PROPAGATION—Waves traveling through a medium.
QUALITY (OF SOUND)—The factor that distinguishes tones of pitch and loudness.
QUARTER-WAVE ANTENNA—Same as the Marconi antenna.
RADIATION FIELD—The electromagnetic field that detaches itself from an antenna and travels
through space.
RADIATION LOSSES—The losses that occur when magnetic lines of force about a conductor are
projected into space as radiation and are not returned to the conductor as the cycle alternates.
RADIATION PATTERN—A plot of the radiated energy from an antenna.
