AI-9
SCANNING—Systematic movement of a radar beam to cover a definite pattern or area in space.
SEA CLUTTER—Unwanted echoes from the irregular surface of the sea that appear on a radar
indicator.
SEARCH RADAR SYSTEM—Early-warning device that searches a fixed volume of space.
SECOND DETECTOR DEMODULATOR—The part of the receiver that separates the audio or video
component from the modulated intermediate frequency.
SECOND-SWEEP ECHOES—See Ambiguous Returns.
SECONDARY LOOP—In a cooling system, the loop that transfers the heat from the heat source
(electronic equipment) to the primary loop; usually distilled water.
SELF-SYNCHRONIZED RADAR—A type of radar in which the timing pulses are generated within
the transmitter.
SENSITIVITY TIME CONTROL (STC)—A circuit that varies the gain of a receiver as a function of
time.
SERIES-CONNECTED DUPLEXER—Configuration in which the tr spark gap is connected in series
in one leg of the transmission line one-half wavelength away from the T- junction.
SHADOW—A dead spot (minimum radiation) caused by the physical obstruction of transmitted waves
by a feed horn.
SINGLE-ENDED MIXER—See Unbalanced Crystal Mixer.
SINGLE, STATIONARY-LOBE SCANNING SYSTEM—Antenna (with a single, stationary beam)
that is rotated to obtain 360-degree coverage.
SLANT RANGE—See Range.
SPECTRUM ANALYZER—A test instrument that provides a visual display of the frequency
distribution of a transmitter output.
SPHERICAL WAVEFRONTS—Waves of energy that spread out in concentric circles.
STABILITY—In a magnetron, the ability to maintain normal operating characteristics.
STATUTE MILE—I5,280 ft.
STUB—A short section of transmission line connected in parallel with the main transmission line.
SCINTILLATION—Apparent change in target reflectivity. Motion of the target causes radar pulses to
bounce off different parts of the target, such as fuselage and wingtip.
SUPERHETERODYNE RECEIVER—A type of receiver that uses a mixer to convert the rf echo to an
IF signal for amplification.
SUPPORT SYSTEM—For a radar, a system that provides an auxiliary input, such as dry air, electrical
power, or liquid cooling.
SYMMETRICAL MULTIVIBRATOR—Circuit that generates square waves.
