and consists of two horizontal half-wave antennas
mounted at right angles to each other in the same
horizontal plane.
TWISTED PAIR—A line consisting of two insulated
wires twisted together to form a flexible line
without the use of spacers.
TWO-WIRE OPEN LINE—A parallel line consisting
of two wires that are generally spaced from 2
to 6 inches apart by insulating spacers.
TWO-WIRE RIBBON (TWIN LEAD)—A parallel
line similar to a two-wire open line except that
uniform spacing is assured by embedding the two
wires in a low-loss dielectric.
UNIDIRECTIONAL ARRAY—An array that radiates
in only one general direction.
UNTUNED LINE—Another name for the flat or
nonresonant line.
V ANTENNA—A bidirectional antenna, shaped like
a V, which is widely used for communications.
VELOCITY—The rate at which a disturbance travels
through a medium.
VERTICAL AXIS—On a graph, the straight line axis
oriented from bottom to top.
VERTICAL PATTERN—The part of a radiation
pattern that is radiated in the vertical plane.
VERTICAL PLANE—An imaginary plane that is
perpendicular to the horizontal plane.
VERTICALLY POLARIZED—Waves radiated with
the E-field component perpendicular to the earth’s
surface.
VOLTAGE-FEED METHOD—See END-FEED
METHOD.
V O L T A G E S T A N D I N G - W A V E R A T I O
(VSWR)—The ratio of maximum to minimum
voltage of a transmission line.
WAVE ANTENNA—See BEVERAGE ANTENNA.
WAVE MOTION—A recurring disturbance advanc-
ing through space with or without the use of a
physical medium.
WAVE TRAIN—A continuous series of waves with
the same amplitude and wavelength.
WAVEFRONT—A small section of an expanding
sphere of electromagnetic radiation, perpendicular
to the direction of travel of the energy.
WAVEGUIDE—A rectangular, circular, or elliptical
metal pipe designed to transport electro-magnetic
waves through its interior.
W A V E G U I D E M O D E O F O P E R A T I O N —
Particular field configuration in a waveguide that
satisfies the boundary conditions. Usually divided
into two broad types: the transverse electric (TE)
and the transverse magnetic (TM).
WAVEGUIDE POSTS—A rod of conductive material
used as impedance-changing devices in
waveguides.
WAVEGUIDE SCREW—A screw that projects into
a waveguide for the purpose of changing the
impedance.
WAVELENGTH—(1) The distance in space occupied
by 1 cycle of a radio wave at any given instant;
(2) The distance a disturbance travels during one
period of vibration.
WINDOW—See Slot.
YAGI ANTENNA—A multielement parasitic array.
Elements lie in the same plane as those of the
end-fire array.
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