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
current flows through it.
a conductor as
POWER RATIO—See POWER GAIN.
P O W E R S T A N D I N G — W A V E R A T I O
(PSWR)—The ratio of the square of the maxi-
mum 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 frequen-
cies 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 electromag-
netic 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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