PULSE-REPETITION FREQUENCY (PRF)The rate, in pulses per second, at which the pulses occur
  .
PULSE-REPETITION RATE (PRR)Same as PULSE-REPETITION FREQUENCY (PRF)  
PULSE-REPETITION TIME (PRT)Interval between the start of one pulse and the start of the next
pulse; reciprocal of pulse-repetition frequency .
PULSE-TIME MODULATION (PTM)Pulse modulation that varies one of the time characteristics of a
pulse train (pwm, pdm, ppm, or pfm) .
PULSE WIDTHDuration of time between the leading and trailing edges of a pulse  .
PULSE-WIDTH MODULATION (PWM)Pulse modulation in which the duration of the pulses is
varied by the modulating voltage .
PULSINGAllowing oscillations to occur for a specific period of time only during selected intervals .
PUMPElectrical source of the energy required to vary the capacitance of a parametric amplifier .
PUSH-PULL AMPLIFIERAn amplifier that uses two transistors (or electron tubes) whose output
signals are in phase opposition .
Q(1) Figure of merit of efficiency of a circuit or coil. (2) Ratio of inductive reactance to resistance in
servos. (3) Relationship between stored energy (capacitance) and rate of dissipation in certain types of
electric elements, structures, or materials  .
QUALITY (OF SOUND)The factor that distinguishes tones of pitch and loudness .
QUANTIZED WAVEA wave created by the arbitrary division of the entire range of amplitude (or
frequency, or phase) values of an analog wave into a series of standard values. Each sample takes the
standard value nearest its actual value when modulated .
QUANTIZING NOISEA distortion introduced by quantizing the signal .
QUANTUM-MECHANICAL TUNNELINGThe action of an electron crossing a PN junction because
of tunnel effect .
QUARTER-WAVE ANTENNASame as the MARCONI ANTENNA .
QUIESCENCE(1) The state of an amplifier with no signal applied. (2) The operating conditions that
exist in a circuit when no input signal is applied to the circuit  [71 .
QUIESCENT STATEThe period during which a transistor, tube, or other circuit element is not
performing an active function in the circuit  .
RADARAn acronym for RAdio Detecting And Ranging .
RADAR ALTIMETERAirborne radar that measures the distance of the aircraft above the ground .
RADAR BEAMThe space in front of a radar antenna where a target can be effectively detected or
tracked. Defined by areas that contain half or more of the maximum power transmitted .