18WuD2x

horizon • horizontal flowcharting 343
location, where the sky and the earth appear to
meet (i.e., the last visible part of the earth’s surface
from a given observation point). 3. Also
called radio horizon. The set of points, from a particular
location at a given radio frequency, representing
the maximum communications range via
the ground wave under normal conditions. Also
see ARTIFICIAL HORIZON.
horizontal 1. Pertaining to objects or effects in a
plane perpendicular to a line connecting the
zenith (the point directly overhead) and the nadir
(the point directly underfoot). 2. Pertaining to
that which is parallel to an assumed flat surface.
3. Pertaining to width deflection on a cathode-ray
tube.
horizontal AFC In a television receiver circuit, automatic
frequency control (AFC) of the horizontal
sweep. It keeps the receiver’s horizontal scanning
in step with that of the camera at the transmitting
station.
horizontal amplification Gain provided by the
horizontal channel of a device, such as an oscilloscope,
cathode-ray electrocardiograph, or
television receiver. Compare VERTICAL
AMPLIFICATION.
horizontal amplifier A circuit or device that provides
HORIZONTAL AMPLIFICATION. Compare
VERTICAL AMPLIFIER.
horizontal angle of radiation For an antenna, the
direction of maximum radiation in the horizontal
plane (see HORIZONTAL, 1), provided as an azimuth
angle measured clockwise from geographic
north.
horizontal angle of deviation In a communications
circuit, the angular difference, in degrees,
between the compass direction from which a received
signal arrives, and the great-circle path
connecting the receiving station with the transmitting
station.
horizontal axis The axis that is parallel to an assumed
horizontal surface (of the earth, for example)
or the one so represented in a diagram. Also
see X-AXIS.
horizontal beamwidth In a directional antenna
system, the angle, measured in the horizontal
plane, between the half-power points in the major
lobe.
horizontal blanking See HORIZONTAL RETRACE
BLANKING.
horizontal-blanking pulse In a television signal,
the rectangular pedestal-shaped pulse that occurs
between the active horizontal lines to
achieve horizontal retrace blanking. Compare
VERTICAL-BLANKING PULSE.
horizontal centering control See CENTERING
CONTROL.
horizontal channel The system of amplifiers, controls,
and terminations that constitute the path of
the horizontal signal in an equipment, such as an
oscilloscope or graphic recorder. Compare VER-
TICAL CHANNEL.
270°
Beamwidth
0°
180°
horizontal beamwidth
90°
horizontal-convergence control In a color television
receiver, the variable component for adjusting
the horizontal dynamic convergence voltage.
horizontal coordinates See CARTESIAN COORDI-
NATES.
horizontal deflection In a cathode-ray tube, the
lateral movement of the electron beam on the
screen. Compare VERTICAL DEFLECTION.
horizontal deflection coils The pair of coils that
produces the magnetic field to horizontally deflect
the electron beam in an electromagnetic cathoderay
tube. Also see DEFLECTION COIL.
horizontal-deflection electrodes See HORIZON-
TAL DEFLECTION COILS and HORIZONTAL DE-
FLECTION PLATES.
horizontal deflection plates In an electrostatic
cathode-ray tube (typical of laboratory oscilloscopes
and some early television picture tubes), a
pair of plates that produces an electric field to
horizontally deflect the electron beam. Compare
VERTICAL DEFLECTION PLATES.
horizontal directivity The radiation or reception
pattern of a directional antenna in the horizontal
plane.
horizontal-drive control See DRIVE CONTROL.
horizontal dynamic convergence During the
scanning of a horizontal line in a color picture
tube, convergence of the electron beams at the
aperture mask. Compare VERTICAL DYNAMIC
CONVERGENCE.
horizontal field strength The field strength of signals
passing through an antenna in a horizontal
plane. Compare VERTICAL FIELD STRENGTH.
horizontal-field-strength diagram A plot of horizontal
field strength, usually in polar form. Compare
VERTICAL-FIELD-STRENGTH DIAGRAM.
horizontal flowcharting Flowcharting the movement
of documents or files, rather than the data
bits themselves, through a digital system.