DIFFUSIONThe scattering of reflected light waves (beams) from an object, such as white paper.
DIPOLEA common type of half-wave antenna made from a straight piece of wire cut in half. Each
half operates at a quarter wavelength of the output.
DIRECTIONALRadiation that varies with direction.
DIRECTORThe parasitic element of an array that reinforces energy coming from the driver toward
DIRECTIVITYThe property of an array that causes more radiation to take place in certain directions
than in others.
DISPERSIONThe refraction of light waves that causes the different frequencies to bend at slightly
DISTRIBUTED CONSTANTSThe constants of inductance, capacitance, and resistance in a
transmission line. The constants are spread along the entire length of the line and cannot be
DOPPLER EFFECTThe apparent change in frequency or pitch when a sound source moves either
toward or away from a listener.
DOUBLETAnother name for the dipole antenna.
DRIVEN ARRAYAn array in which all of the elements are driven.
DRIVEN ELEMENTAn element of an antenna (transmitting or receiving) that is connected directly
to the transmission line.
ECHOThe reflection of the original sound wave as it bounces off a distant surface.
ELASTICITYThe ability of a substance to return to its original state.
ELECTROMAGNETIC FIELDThe combination of an electric (E) field and a magnetic (H) field.
ELECTROMAGNETIC INTERFERENCEMan-made or natural interference that degrades the
quality of reception of radio waves.
ELECTROMAGNETIC RADIATIONThe radiation of radio waves into space.
ELECTRIC (E) FIELDThe field produced as a result of a voltage charge on a conductor or antenna.
ELEMENTA part of an antenna that can be either an active radiator or a parasitic radiator.
END-FEED METHODConnecting one end of an antenna through a capacitor to the final output stage
of a transmitter.
END-FIRE ARRAYAn array in which the direction of radiation is parallel to the axis of the array.
FADINGVariations in signal strength by atmospheric conditions.
FEEDERA transmission line that carries energy to the antenna.