FOUR-ELEMENT ARRAYAn array with three
parasitic elements and one driven element.
FREE-SPACE LOSSThe loss of energy of a radio
wave because of the spreading of the wavefront
as it travels from the transmitter.
FREQUENCYThe number of cycles that occur in
one second. Usually expressed in Hertz.
FREQUENCY DIVERSITYTransmitting (and
receiving) of radio waves on two different
FRONT-TO-BACK RATIOThe ratio of the energy
radiated in the principal direction to the energy
radiated in the opposite direction.
FUNDAMENTAL FREQUENCYThe basic
frequency or first harmonic frequency.
GAINThe 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 ENDSee INPUT END
GROUND PLANEThe portion of a groundplane
antenna that acts as ground.
GROUND-PLANE ANTENNAA type of antenna
that uses a ground plane as a simulated ground
to produce low-angle radiation.
GROUND REFLECTION LOSSThe loss of rf
energy each time a radio wave is reflected from
the earths surface.
GROUND SCREENA series of conductors buried
below the surface of the earth and arranged in
a radial pattern.
Used to reduce losses in the
GROUND WAVESRadio waves that travel near the
surface of the earth.
GROUP VELOCITYThe forward progress velocity
of a wave front in a waveguide.
H-FIELDAny 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-JUNCTIONA waveguide junction in
which the junction arm is parallel to the magnetic
lines of force in the main waveguide.
HALF-WAVE DIPOLE ANTENNAAn antenna
consisting of two rods (¼ wavelength h) in a
straight line, that radiates electromagnetic energy.
HARMONICA frequency that is a whole number
multiple of a smaller base frquency.
HERTZ ANTENNAA half-wave antenna installed
some distance above ground and positioned either
vertically or horizontally.
HORNA funnel-shaped section of waveguide used
as a termination device and as a radiating antenna.
HORIZONTAL AXISOn a graph, the straight line
axis plotted from left to right.
HORIZONTAL PATTERNThe part of a radiation
pattern that is radiated in all directions along the
HORIZONTALLY POLARIZEDWaves that are
radiated with their E-field component parallel
to the earths surface.
HYBRID JUNCTIONA waveguide junction that
combines two or more basic T-junctions.
HYBRID RINGA hybrid-waveguide junction that
combines a series of E-type T-junctions in a ring
I2R LOSSSee COPPER LOSS.