REFLECTOR—The parasitic element of an array that causes maximum energy radiation in a direction toward the driven element.
REFRACTION—The changing of direction as a wave leaves one medium and enters another medium of a different density.
REFRACTIVE INDEX—The ratio of the phase velocity of a wave in free space to the phase velocity of the wave in a given substance (dielectric).
RERADIATION—The reception and retransmission of radio waves caused by turbulence in the troposphere.
RESONANCE—The condition produced when the frequency of vibrations are the same as the natural frequency (of a cavity), The vibrations reinforce each other.
RESONANT LINE—A transmission line that has standing waves of current and voltage.
RHOMBIC ANTENNA—A diamond-shaped antenna used widely for long-distance, high-frequency transmission and reception.
RIGID COAXIAL LINE—A coxial line consisting of a central, insulated wire (inner conductor) mounted inside a tubular outer conductor.
ROTATING JOINT—A joint that permits one section of a transmission line or waveguide to rotate continuously with respect to another while passing energy through the joint. Also called a rotary coupler.
SCATTER ANGLE—The angle at which the receiving antenna must be aimed to capture the scattered energy of tropospheric scatter.
SELF-INDUCTION—The phenomenon caused by the expanding and collapsing fields of an electron that encircles other electrons and retards the movement of the encircled electrons.
SERIES RESONANT CIRCUIT—A circuit that acts as a low impedance at resonance.
SHIELDED PAIR—A line consisting of parallel conductors separated from each other and surrounded by a solid dielectric.
SHORT-CIRCUITED LINE—A transmission line that has a terminating impedance equal to 0.
SKIN EFFECT—The tendency for alternating current to concentrate in the surface layer of a conductor. The effect increases with frequency and serves to increase the effective resistance of the conductor.
SKIP DISTANCE—The distance from a transmitter to the point where the sky wave is first returned to earth.
SKIP ZONE—A zone of silence between the point where the ground wave becomes too weak for reception and the point where the sky wave is first returned to earth.
SKY WAVES—Radio waves reflected back to earth from the ionosphere.
SLOT—Narrow opening in a waveguide wall used to couple energy in or out of the waveguide. Also called an APERTURE or a WINDOW.
SOURCE—(1) The object that produces waves or disturbance; (2) The name given to the end of a two-wire transmission line that is connected to a source.
SPACE DIVERSITY—Reception of radio waves by two or more antennas spaced some distance apart.
SPACE WAVE—A radio wave that travels directly from the transmitter to the receiver and remains in the troposphere.
SPECTRUM—(1) The entire range of electromagnetic waves; (2) VISIBLE. The range of electromagnetic waves that stimulate the sense of sight;
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