RANGE-HEIGHT INDICATORA radar display on which slant range is shown along the X axis and
height along the Y axis .
RANGE MARKERA movable vertical pulse on an A-scope or a ring on a PPI scope used to measure the
range of an echo or to calibrate the range scale .
RANGE RESOLUTIONAbility of a radar to distinguish between targets that are close together .
RANGESThe several upper limits a meter will measure as selectable by a switch or by jacks; for
example, a voltmeter may have ranges of 1 volt, 2.5 volts, 10 volts, 25 volts, and 100 volts .
RANGE STEPOn an A-scope sweep, a vertical displacement used to measure the range of an echo .
RAREFIED WAVEA longitudinal wave that has been expanded or rarefied (made less dense) as it
moves away from the source .
RATE GYROA gyro used to detect and measure angular rates of change .
RATIOThe value obtained when one number is divided by another. This value indicates the relative
proportions of the two numbers .
RATIO DETECTORA detector that uses a double-tuned transformer to convert the instantaneous
frequency variations of the FM input signal to instantaneous amplitude variations .
RATIO OF TRANSMITTED POWERSThe power ratio (FSK versus AM) that expresses the overall
improvement of FSK transmission when compared to AM under rapid-fading and high-noise conditions
RC CONSTANTTime constant of a resistor-capacitor circuit; equal in seconds to the resistance value in
ohms multiplied by the capacitance value in farads  .
RC DIFFERENTIATORAn RC circuit in which the output is taken from the resistor .
RC FILTERA filter used in applications where load current is low and constant, and voltage regulation is
not necessary .
RC INTEGRATORAn RC circuit in which the output is taken from the capacitor .
RC NETWORKA circuit containing resistance and capacitance arranged in a particular manner to
perform a specific function .
RC OSCILLATORAn oscillator in which the frequency is determined by resistive and capacitive
REACTANCEThe opposition offered to the flow of an alternating current by the inductance,
capacitance, or both, in any circuit .
REACTANCE AMPLIFIERA low-noise amplifier that uses a nonlinear variable reactance as the active
element instead of a variable resistance. Also called a parametric amplifier .
REACTANCE TUBEA tube connected in parallel with the tank circuit of an oscillator. Provides a signal
that will either lag or lead the signal produced by the tank .
REACTANCE-TUBE MODULATORAn FM modulator that uses a reactance tube in parallel with the
oscillator tank circuit .