18WuD2x

groundtrack • G-string antenna 323
changes position on the surface. For satellites in
equatorial orbits, the track follows the equator.
ground wave In wireless communications and
broadcasting, an electromagnetic (EM) wave that
consists of three distinct components: the direct
wave (also called the line-of-sight wave), the reflected
wave, and the surface wave. The direct
wave is significant only when the transmitting and
receiving antennas are connected by a line through
free space without obstructions. The reflected
wave, after returning from the earth’s surface or a
human made structure, combines with the direct
wave (if any) at the receiving antenna. The surface
wave travels in electrical contact with the earth.
This occurs only with vertically polarized EM fields
at frequencies below about 15 MHz. Below about
300 kHz, the surface wave propagates for hundreds
or even thousands of miles. Sometimes the
surface wave is called the ground wave.
ground wire A conductor between an equipment
and a ground connection, either for circuit completion
or for safety.
group 1. A series of computer storage locations
containing a specific record or records. 2. The
data in these locations. 3. A record set having a
common key value in a sorted file.
group busy In a telephone system, an audio signal
indicating that all of the lines in a group are in
use.
group code In digital communications, an errordetecting
code used to verify a character group
transferred between terminals.
group delay In a modulated signal, a delay in the
transmission of data.
grouped-frequency operation In a two-wire communications
system, the grouping of directional
signals into certain frequency bands.
grouped records A set of data records in which the
key of one record identifies the entire set.
grouping 1. The arrangement of data into blocks
or sets. 2. On a phonograph disc, the insertion of
gaps in the arrangement of grooves. 3. Any periodic
irregularity in the spacing of a data transmission.
4. The bunching of grooves on a disc
recording. 5. In a facsimile system, occasional
spacing errors between recorded lines. 6. A mass
of data arranged into groups, according to common
characteristics.
group mark 1. In telegraphy, an indicator that signals
the end of a data unit. 2. A character indicating
the end of a character group; usually, it is
a logical record that is addressed and processed
as a unit.
group velocity The velocity at which a group of
waves or a pulse is propagated.
Grove cell A closed-circuit primary cell in which
the positive electrode, platinum, is immersed in
nitric acid; the negative electrode, zinc, is immersed
in sulfuric acid. The nitric acid is held in
a porous cup, surrounded by a larger jar of sulfuric
acid.
growler 1. An electromechanical troubleshooting
device that indicates the location of short circuits
and grounds (especially in electric motors) by
emitting a growling or rumbling sound. 2. Any
tester that provides an audible signal, which indicates
electrical continuity.
grown-diffused transistor A transistor that is
made by first growing the emitter and collector
regions as a crystal, into which the base region is
later diffused while the crystal is being pulled.
grown diode A semiconductor diode created by
growing a layer of p-type material into n-type material
(or vice versa) as the single-crystal material
is being pulled from the melt.
grown junction A pn junction produced by adding
impurities in various amounts to a crystal while it
is being pulled from molten semiconductor material.
grown-junction diode See GROWN DIODE.
grown-junction photocell A grown-junction diode
used as a photoconductive cell.
grown-junction transistor A transistor made by
adding n-type and p-type impurities successively
to a crystal in its molten state, then slicing
the resulting npn formations from the finished
crystal.
G-scan
A rectangular radar display consisting of a
laterally centered blip that “grows wings” as a target
approaches. Horizontal and vertical displacement
of the blip indicate horizontal and vertical
aiming errors.
Transmitting
horn
Coaxial
cable
Zinc
(−)
Platinum
(+)
Nitric
acid
Sulfuric
acid
Grove cell
G scope See G SCAN.
GSR Abbreviation of GALVANIC SKIN RESPONSE.
G-string antenna In microwave operations, a communications
path provided by a dielectric-coated
wire that behaves like an extremely low-loss
coaxial line with its outer conductor removed to
infinity. A horn at each end matches the line to
the transmitter and receiver. The term comes
Wire
G-string antenna
Porous cup
Solid
container
Receiving
horn
Coaxial
cable