AI-4
FAST-TIME-CONSTANT CIRCUIT—Differentiator circuit in the first video amplifier that allows
only the leading edges of target returns, no matter how small or large, to be used.
FEEDBACK—The return of a portion of the output of a circuit to its input.
FEEDHORN—A horn radiator used to feed a reflector.
FIRST DETECTOR—See Mixer.
FREQUENCY COMPENSATION NETWORK—Circuit modification used to improve or broaden the
linearity of its frequency response.
FREQUENCY SCANNING—Varying the output frequency to achieve electronic scanning.
FREQUENCY SPECTRUM—In a radar, the entire range of frequencies contained in an rf pulse or
signal.
FREQUENCY SYNTHESIZER—A bank of oscillators in which the outputs can be mixed in various
combinations to produce a wide range of frequencies.
GAIN—Any increase in the strength of a signal.
GATED AGC—Circuit that permits automatic gain control to function only during short time intervals.
GLOW DISCHARGE—Discharge of electricity through a gas in an electron tube.
GROUND CLUTTER—Unwanted echoes from surrounding land masses that appear on a radar
indicator.
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-CONTROLLED APPROACH—Radar system used to guide aircraft to safe landings in
poor visibility conditions.
GUIDANCE RADAR—System which provides information that is used to guide a missile to a target.
HALF-POWER POINT—A point on a waveform or radar beam that corresponds to half the power of
the maximum power point.
HARD-TUBE MODULATOR—A high-vacuum electron tube modulator that uses a driver for pulse
forming.
HEIGHT-FINDING RADAR—Radar that provides target altitude, range, and bearing data.
HITS PER SCAN—The number of times an rf beam strikes a target per antenna revolution.
HORIZONTAL PLANE—Imaginary plane that is tangent (or parallel) to the earth's surface at a given
location.
HORN ANTENNA—See Horn Radiator.
HORN RADIATOR—A tubular or rectangular microwave antenna that is tapered and is widest at the
open end.
