PHASE SHIFTER—A device used to change the phase relationship between two ac signals.
PLANE OF POLARIZATION—The plane (vertical or horizontal) with respect to the earth in which the E-field propagates.
POSITIVE ALTERNATION—The portion of a sine wave above the reference line.
POWER GAIN—The ratio of the radiated power of an antenna compared to the output power of a standard antenna. A measure of antenna efficiency usually expressed in decibels. Also referred to as POWER RATIO.
POWER LOSS—The heat loss in a conductor as current flows through it.
POWER RATIO—See POWER GAIN.
POWER STANDING—WAVE RATIO (PSWR)—The ratio of the square of the maximum and minimum voltages of a transmission line.
PROPAGATION—Waves traveling through a medium.
PROBE—A metal rod that projects into, but is insulated from, a waveguide or resonant cavity and used to inject or extract energy.
QUARTER-WAVE ANTENNA—See MARCONI ANTENNA.
RADIATION FIELD—The electromagnetic field that detaches itself from an antenna and travels through space.
RADIATION LOSSES—The losses that occur when magnetic lines of force about a conductor are projected into space as radiation and are not returned to the conductor as the cycle alternates.
RADIATION PATTERN—A plot of the radiated energy from an antenna.
RADIATION RESISTANCE—The resistance, which if inserted in place of an antenna, would consume the same amount of power as that radiated by the antenna.
RADIO FREQUENCIES—Electromagnetic frequencies that fall between 3 kilohertz and 300 gigahertz and are used for radio communications.
RADIO HORIZON—The 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 WAVE—A longitudinal wave that has been expanded or rarefied (made less dense) as it moves away from the source.
RECEIVER—The object that responds to a wave or disturbance. Same as detector.
RECEIVING ANTENNA—The device used to pick up an rf signal from space.
RECEIVING END—See OUTPUT END.
RECIPROCITY—The ability of an antenna to both transmit and receive electromagnetic energy with equal efficiency.
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 WAVES—Waves that are neither transmitted nor absorbed, but are reflected from the surface of the medium they encounter.
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