AI-9
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.
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
which encircles other electrons and retards the movement of the encircled electrons.
SELF-LUMINOUS BODIES—Objects that produce their own light.
SENDING END—See INPUT END.
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.
SINK—See OUTPUT END.
SKIN EFFECT—The flow of ac current near the surface of a conductor at rf frequencies.
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.
SONIC—Pertaining to sounds capable of being heard by the human ear.
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. (3) ELECTROMAGNETIC. The entire
range of electromagnetic waves arranged in order of their frequencies.
SPORADIC E LAYER—Irregular cloud-like patches of unusually high ionization. Often forms at
heights near the normal E layer.
SPREADER—Insulator used with transmission lines and antennas to keep the parallel wires separated.
