FOUR-ELEMENT ARRAY—An array with three parasitic elements and one driven element.
FREE-SPACE LOSS—The loss of energy of a radio wave because of the spreading of the wavefront as it travels from the transmitter.
FREQUENCY—The number of cycles that occur in one second. Usually expressed in Hertz.
FREQUENCY DIVERSITY—Transmitting (and receiving) of radio waves on two different frequencies simultaneously.
FRONT-TO-BACK RATIO—The ratio of the energy radiated in the principal direction to the energy radiated in the opposite direction.
FUNDAMENTAL FREQUENCY—The basic frequency or first harmonic frequency.
GAIN—The ratio between the amount of energy propagated from an antenna that is directional to the energy from the same antenna that would be propagated if the antenna were not directional.
GENERATOR END—See INPUT END
GROUND PLANE—The portion of a groundplane antenna that acts as ground.
GROUND-PLANE ANTENNA—A type of antenna that uses a ground plane as a simulated ground to produce low-angle radiation.
GROUND REFLECTION LOSS—The loss of rf energy each time a radio wave is reflected from the earth's surface.
GROUND SCREEN—A series of conductors buried below the surface of the earth and arranged in a radial pattern. Used to reduce losses in the ground.
GROUND WAVES—Radio waves that travel near the surface of the earth.
GROUP VELOCITY—The forward progress velocity of a wave front in a waveguide.
H-FIELD—Any space or region in which a magnetic force is exerted. The magnetic field may be produced by a current-carrying coil or conductor, by a permanent magnet, or by the earth itself. Also known as MAGNETIC FIELD.
H-TYPE T-JUNCTION—A waveguide junction in which the junction arm is parallel to the magnetic lines of force in the main waveguide.
HALF-WAVE DIPOLE ANTENNA—An antenna consisting of two rods (¼ wavelength h) in a straight line, that radiates electromagnetic energy.
HARMONIC—A frequency that is a whole number multiple of a smaller base frquency.
HERTZ ANTENNA—A half-wave antenna installed some distance above ground and positioned either vertically or horizontally.
HORN—A funnel-shaped section of waveguide used as a termination device and as a radiating antenna.
HORIZONTAL AXIS—On a graph, the straight line axis plotted from left to right.
HORIZONTAL PATTERN—The part of a radiation pattern that is radiated in all directions along the horizontal plane.
HORIZONTALLY POLARIZED—Waves that are radiated with their E-field component parallel to the earth's surface.
HYBRID JUNCTION—A waveguide junction that combines two or more basic T-junctions.
HYBRID RING—A hybrid-waveguide junction that combines a series of E-type T-junctions in a ring configuration.
I2R LOSS—See COPPER LOSS.
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