GAIN - (1) The ratio between the amount of energy propagated from an
antenna that is directional compared to the energy from the same antenna that would be
propagated if the antenna were not directional . (2) Any increase in the strength of a
signal .
GAIN-BANDWIDTH PRODUCT - The number that results when the gain of a
circuit is multiplied by the bandwidth of that circuit. For an operational amplifier, the
gain-bandwidth product for one configuration will always equal the gain-bandwidth product
for any other configuration of the same amplifier .
GALENA - A crystalline form of lead sulfide used in early radio receivers
.
GALVANOMETER - A meter used to measure small values of current by
electromagnetic or electrodynamic means .
GAMMA (g) - The emitter-to-base current ratio in a common-collector
configuration .
GAMMA-FERRIC OXIDE - The common magnetic constituent of magnetic tapes in
a dispersion of fine, needle-like particles within the coating.
GANGED TUNING - The process used to tune two or more circuits with a
single control .
GAP EROSION - (1) The read or write gap increased in length and retreated
below the head surface. (2) Usually due to deterioration of core material at the edges of
the gap.
GAP LOSS - (1) The loss in output due to the finite gap length of the
reproduce head. (2) The loss increases as the wavelength decreases.
GAP WIDTH - The dimension of the gap of a magnetic head measured in the
direction perpendicular to the direction of the tape path.
GAS - One of the three states of matter; it has no fixed form or volume .
GATE - As applied to logic circuitry, one of several different types of
electronic devices that will provide a particular output when specified input conditions
are satisfied. Also, a circuit in which a signal switches another signal on or off .
GATED AGC - Circuit that permits automatic gain control to function only
during short time intervals .
GATED-BEAM DETECTOR - An fm demodulator that uses a special gated-beam
tube to limit, detect, and amplify the received fm signal. Also known as a quadrature
detector .
GATING - The process of selecting those portions of a wave that exist
during one or more selected time intervals or that have magnitudes between selected
limits. Also, the application of a specific waveform to perform electronic switching .
GAUSS - The metric unit of the magnetic flux density equal to 1 Mx/CM2.
GENERAL-PURPOSE COMPUTER - A computer designed to operate on a program of
instructions for the purpose of solving many different types of processing problems.
GENERAL PURPOSE ELECTRONIC TEST EQUIPMENT (GPETE) - Test equipment that
has the capability, without modification, to generate, modify, or measure a range of
electronic functions required to test several equipments or systems of basically different
designs .
GENERATIONS OF COMPUTERS - Historically, the distinctive types of
computers from the 1940s to the present; the first generation was based on vacuum tubes,
the second on transistors, the third and current features integrated circuits. Recent
developments involve the use of VLSI (very large scale integration) and semiconductor
memories.
GENERATOR - A machine that converts mechanical energy to electrical energy
by applying the principle of magnetic induction. A machine that produces ac or dc voltage,
depending on the original design .
GENERATOR END - See INPUT END .
GERMANIUM - A grayish-white metal having semiconductor properties .
GETTER - An alkali metal introduced into a vacuum tube during manufacture.
It is fired after the tube has been evacuated to react chemically with (and eliminate) any
remaining gases .
GIMBAL - A mechanical frame, with two perpendicular intersecting axes of
rotation, used to support and furnish a gyro wheel with the necessary freedom to tilt in
any direction .
GLOW DISCHARGE - Discharge of electricity through a gas in an electron
tube .
GRAMME-RING ARMATURE - An inefficient type of armature winding in which
many of the turns are shielded from the field by its own iron ring .
GRAPH - A pictorial presentation of the relation between two or more
variable quantities, such as between an applied voltage and the current it produces in a
circuit .
GRAPHICS - The use of pictorial means to present data in the form of
plotted curves, graphs (bar, pie, line, and so on), or diagrams. These may be displayed on
a crt or printed.
GRID BIAS - A constant fixed potential applied between the grid and the
cathode of a vacuum tube to establish an operating point .
GRID CURRENT - The current that flows in the grid-to-cathode circuit of a
vacuum tube .
GRID-GAP TUNING - A method of changing the center frequency of a resonant
cavity by physically changing the distance between the cavity grids .
GRID-LEAK BIAS - A self-bias provided by a high resistance connected
across the grid capacitor or between the grid and cathode .
GROUND - (1) The point in a circuit used as a common reference point for
measuring purposes. (2) To connect some point of an electrical circuit or some item of
electrical equipment to earth or to the conducting medium used in lieu thereof .
GROUND CLUTTER - Unwanted echoes, from surrounding land masses, that
appear on a radar indicator .
GROUND-CONTROLLED APPROACH - A radar system used to guide aircraft to safe
landings in poor visibility conditions .
GROUND PLANE - The portion of a ground-plane 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 PLANES - Copper planes used to minimize interference between
circuits and from external sources .
GROUND POTENTIAL - Zero potential with respect to the ground or earth .
GROUND RANGE - The distance on the surface of the earth between a radar
and its target. Equal to slant range only if both radar and target are at the same
altitude .
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 which travel near the surface of the earth .
GROUP - A collection of units, assemblies, subassemblies, and parts. It is
a subdivision of a set or system but is not capable of performing a complete operational
function .
GROUP VELOCITY - The forward progress velocity of a wave front in a
waveguide .
GROWN JUNCTION - A method of mixing P-type and N-type impurities into a
single crystal while the crystal is being grown .
GUIDANCE RADAR - A system which provides information that is used to guide
a missile to a target .
GYRO - Abbreviation for gyroscope .
GYROSCOPE - A mechanical device containing a spinning mass mounted so that
it can assume any position in space .
