RADIATION RESISTANCEThe resistance, which if inserted in place of an antenna, would consume
the same amount of power as that radiated by the antenna.
RADIO FREQUENCIESElectromagnetic frequencies that fall between 3 kilohertz and 300 gigahertz
and are used for radio communications.
RADIO HORIZONThe boundary beyond the natural horizon in which radio waves cannot be
propagated over the earth's surface.
RADIO WAVE(1) A form of radiant energy that can neither be seen nor felt. (2) An electromagnetic
wave generated by a transmitter.
RAREFIED WAVEA longitudinal wave that has been expanded or rarefied (made less dense) as it
moves away from the source.
RECEIVERThe object that responds to a wave or disturbance. Same as detector.
RECEIVING ANTENNAThe device used to pick up an rf signal from space.
RECEIVING ENDSee OUTPUT END.
RECIPROCITYThe property of interchangeability of the same antenna for transmitting and receiving.
RECTANGULAR-COORDINATE GRAPHA graph in which straight-line axes (horizontal and
vertical) are perpendicular.
REFERENCE LINEThe position a particle of matter would occupy if it were not disturbed by wave
REFLECTED WAVE(1) The wave that reflects back from a medium. (2) Waves traveling from the
load back to the generator on a transmission line. (3) The wave moving back to the sending end of a
transmission line after reflection has occurred.
REFLECTION WAVESWaves that are neither transmitted nor absorbed, but are reflected from the
surface of the medium they encounter.
REFLECTORThe parasitic element of an array that causes maximum energy radiation in a direction
toward the driven element.
REFRACTIONThe changing of direction as a wave leaves one medium and enters another medium of
a different density.
RERADIATIONThe reception and retransmission of radio waves caused by turbulence in the
RESONANCEThe condition produced when the frequency of vibrations are the same as the natural
frequency (of a cavity). The vibrations reinforce each other.
RESONANT LINEA transmission line that has standing waves of current and voltage.
REST POSITIONSee REFERENCE LINE.
REVERBERATIONThe multiple reflections of sound waves.