AI-7
PARABOLIC REFLECTOR—An antenna reflector in the shape of a parabola. It converts spherical
wavefronts from the radiating element into plane wavefronts.
PARALLEL-CONNECTED DUPLEXER—Configuration in which the tr spark gap is connected
across the two legs of the transmission line one-quarter wavelength from the Tjunction.
PARASITIC ARRAY—An antenna array containing one or more elements not connected to the
transmission line.
PEAK POWER—Maximum power of the rf pulse from a radar transmitter.
PERSISTANCE—The length of time a phosphor dot glows on a crt before disappearing.
PHANTASTRON—A variable-length sawtooth generator used to produce a sweep on an A-scope.
PIP (BLIP)—On a crt display, a spot of light or a base-line irregularity representing the radar echo.
PLANE WAVEFRONTS—Waves of energy that are flat, parallel planes and perpendicular to the
direction of propagation.
PLANNED-POSITION INDICATOR—A radar display in which range is indicated by the distance of a
bright spot or pip from the center of the screen and the bearing is indicated by the radial angle of the
spot.
POWER GAIN—In an antenna, the ratio of its radiated power to that of a reference.
POWER-AMPLIFIER (CHAIN) TRANSMITTER—Transmitter that uses a series of power amplifiers
to create a high level of power.
PREAMPLIFIER (PREAMP)—An amplifier that raises the output of a low-level source for further
processing without appreciable degradation of the signal-to-noise ratio.
PRIMARY LOOP—In a cooling system, the primary source of cooling for the distilled water.
PROBE COUPLER—A resonant conductor placed in a waveguide or cavity to insert or extract energy.
PULSE WIDTH—Duration of time between the leading and trailing edges of a pulse.
PULSE-FORMING NETWORK (PFN)—An LC network that alternately stores and releases energy in
an approximately rectangular wave.
PULSE-REPETITION RATE (PRR)—Average number of pulses per unit of time; pulse rate.
PULSE-REPETITION FREQUENCY (PRF)—The rate at which pulses are transmitted, given in hertz
or pulses per second; reciprocal of pulse-repetition time.
PULSE-REPETITION TIME (PRT)—Interval between the start of one pulse and the start of the next
pulse; reciprocal of pulse-repetition frequency.
RADAR—An acronym for RAdio Detecting And Ranging.
RADAR ALTIMETER—Airborne radar that measures the distance of the aircraft above the ground.
RADAR BEAM—The space in front of a radar antenna where a target can be effectively detected or
tracked.
