18WuD2x

ground connection • ground-mounted vertical antenna 321
ground connection 1. A low-resistance connection
to the earth. 2. The common point, such as a
chassis, to which zero-potential terminals of circuit
components are connected.
ground constants The conductivity and dielectric
constant of the earth for a particular kind of terrain
and soil at a given location. Affects the behavior
of radio antenna systems and electrical
utility systems. Usually, high conductivity (low
resistance) and low dielectric constant are desirable
characteristics.
ground-controlled approach Abbreviation, GCA.
In air navigation, a ground radar system that provides
information for radio-directed aircraft approaches.
ground-controlled interception Abbreviation,
GCI. A ground radar system by which an aircraft
can be directed to intercept enemy aircraft.
ground current 1. A direct electric current flowing
into the earth from an electrical or electronic device,
or into a device from the earth. 2. An alternating
current flowing between the earth and a
device. 3. An electric current flowing through the
earth between two points. 4. A current flowing in
the normal ground (low-potential) line of a circuit.
ground detector A device that indicates whether
or not a given circuit point is at direct-current
ground.
grounded antenna See MARCONI ANTENNA.
grounded-base circuit See COMMON-BASE CIR-
CUIT.
grounded-cathode circuit See COMMON-
CATHODE CIRCUIT.
grounded-collector circuit See COMMON-
COLLECTOR CIRCUIT.
grounded-drain circuit See COMMON-DRAIN
CIRCUIT.
grounded-emitter circuit See COMMON-
EMITTER CIRCUIT.
grounded-gate circuit See COMMON-GATE CIR-
CUIT.
grounded-grid circuit See COMMON-GRID CIR-
CUIT.
grounded outlet An outlet with a receptacle having
a ground contact that can be connected to
equipment-grounding conductors.
grounded-source circuit See COMMON-SOURCE
CIRCUIT.
grounded system A set of electrical conductors or
a transmission line in which one conductor is deliberately
grounded.
ground effect 1. Modification or distortion of the
ideal free-space directivity pattern of an antenna
by reflections from, and absorption by, the earth.
2. Effects of the earth on radio-wave propagation
(e.g., the production of a reflected wave and a surface
wave, neither of which can exist if the earth
is not part of the signal path). 3. Effects on antenna
behavior, such as modification of the
impedance and resonant frequency, caused by
the proximity of the earth.
ground efficiency In an antenna system, the quality
of the ground circuit. For some antenna systems,
such as a balanced dipole at great height,
this is not a consideration. Ideal ground efficiency
(100%) results in zero ground loss.
ground environment 1. See GROUND CON-
STANTS. 2. The ground characteristics in the
vicinity of an unbalanced antenna working
against ground. 3. In aviation, the set of groundbased
installations.
ground fault 1. Loss of a ground connection. 2. A
short-circuit to ground.
ground-fault interrupter Abbreviation, GFI. A
fast-acting electronic circuit breaker that opens
the power-line circuit breaker to prevent electric
shock or equipment damage when the path of
current flow is through the earth.
grounding electrode A device, such as a ground
plate or ground rod, that facilitates lowresistance
connections to the earth.
grounding plate A metal plate connected to the
earth, on which a person stands to discharge
static electricity from the body.
grounding rod See GROUND ROD.
ground insulation Electrical insulation used between
adjacent energized and grounded parts,
such as transformer windings and metal cores.
ground level See GROUND STATE.
ground loop A closed current path resulting from
improper grounding of the components in a system.
A loop is formed when two devices are connected
to each other, and also to separate earth
grounds or to a single earth ground via conductors
of appreciable length. The loops can act as antennas,
increasing the likelihood of ELECTROMAG-
NETIC INTERFERENCE to or from the system. The
use of a single GROUND BUS is preferred.
A B C
Loop
ground loop
Loop
ground mat A grid or network of conductors, connected
to earth ground, for the purpose of improving
the earth conductivity.
ground-mounted vertical antenna A vertical radiator
mounted at the earth’s surface or at the surface
of a body of water, and fed with coaxial cable.
The radiator can be any physical length, but it is
tuned to resonance at the operating frequency.