ANTENNA A device used to radiate or receive radio
ANTENNA COUPLER A device used for impedance
matching (tuning) between an antenna and a transmitter
ANTENNA RECIPROCITY The ability of an antenna
to both transmit and receive electromagnetic energy.
ANTENNA TUNING The process where an antenna is
electrically matched to the output frequency and
impedance of the transmitter.
ATTENUATION A deliberate reduction or an
unintended loss in RF signal strength.
BANDWIDTH Any section of the frequency spectrum
occupied by specific signals.
BIDIRECTIONAL ANTENNA An antenna that
radiates in or receives most of its energy from only two
BLACK Cipher text or encrypted text or information
CARRIER The unmodulated signal originally produced
in the oscillator section of a transmitter.
CARRIER FREQUENCY The final RF output without
modulation. The assigned transmitter frequency.
CHANNEL A carrier frequency assignment, usually with
a fixed bandwidth.
COMPLEX WAVE A transmitted radio signal
composed of different frequencies.
COUNTERPOISE The ground plane, or reflective
surface, comprising an antennas reflected image at a
CRITICAL FREQUENCY The highest transmitted
frequency that can be propagated directly upward and
still be bent, or refracted, back to Earth.
CYCLE Two complete alternations of alternating current,
or one complete revolution in any period of time, equal
DAMA (DEMAND ASSIGNED MULTIPLE ACCESS
SUBSYSTEM) Subsystem that multiplexes several
subsystems on one satellite channel.
DIFFRACTION The bending of radio waves around the
edges of a solid objector dense mass.
DIRECTIONAL ANTENNA An antenna that radiates
or receives radio waves more effectively in some
directions than in others.
DIRECTIVITY The sharpness or narrowness of an
antennas radiation pattern in a given plan.
DIRECT WAVE A radio signal that travels in a direct
line-of-sight path from the transmitting antenna to the
DUMMY LOAD A nonradiating device used at the end
of a transmission line in place of an antenna for tuning a
transmitter, The dummy load converts transmitted
energy into heat so that no energy is radiated outward or
EHF (EXTREMELY HIGH FREQUENCY) The band
of frequencies from 30 GHz to 300 GHz.
ELECTRIC FIELD A field produced as a result of a
voltage charge on an antenna.
ELECTROMAGNETIC ENERGY An RF source
composed of both an electric and a magnetic field.
ELECTROMAGNETIC WAVES Energy produced at
the output of a transmitter; also called radio waves.
FADING Variation, usually gradual, in the field strength
of a radio signal that is caused by changes in the
transmission path or medium.