Appendix I Glossary

COAXIAL LINE—A type of transmission line that contains two concentric conductors. COLLINEAR ARRAY—An array with all the elements in a straight line. Maximum radiation is perpendicular to the axis of the elements. COMBINATION ARRAY—An array system that uses the characteristics of more than one array. Also known as ARRAY OF ARRAYS. COMPLEX WAAE—A wave produced by combining two or more pure tones at the same time. CONDUCTANCE—The opposite of resistance in transmission lines. The minute amount of resistance that is present in the insulator of a transmission line. CONNECTED ARRAY—see DRIVEN ARRAY COPPER LOSS—Power loss in copper conductors caused by the internal resistance of the conductors to current flow. Also know as 1²R LOSS. CORNER-REFLECTOR ANTENNA—A half-wave antenna with a reflector consisting of two flat metal surfaces meeting at an angle behind the radiator. COUNTERPOISE—A network of wire that is connected to a quarter-wave antenna at one end and provides the equivalent of an additional ¼ wavelength. COUPLING DEVICE—A coupling coil that con- nects the transmitter to the feeder. CREST (TOP)—The peak of the positive alternation (maximum value above the line) of a wave. CRITICAL ANGLE—The maximum angle at which radio waves can be transmitted and still be refracted back to earth. CRITICAL FREQUENCY—The maximum fre- quency at which a radio wave can be transmitted vertically and still be refracted back to earth. CURRENT-FEED METHOD—See CENTER-FEED METHOD. C U R R E N T S T A N D I N G - W A V E R A T I O (ISWR)—The ratio of maximum to minimum current along a transmission line. CUTOFF FREQUENCY—The frequency at which the attenuation of a waveguide increases sharply and below which a traveling wave in a given mode cannot be maintained. A frequency with a half wavelength that is greater than the wide dimension of a waveguide. CYCLE—One complete alternation of a sine wave that has a maximum value above and a maximum value below the reference line. DAMPING—Reduction of energy by absorption. DENSITY—(1) The compactness of a substance; (2) Mass per unit volume. DETECTOR—The device that responds to a wave or disturbance. DIELECTRIC HEATING—The heating of an insulating material by placing it in a high frequency electric field. DIELECTRIC LOSSES—The losses resulting from the heating effect on the dielectric material between conductors. DIELECTRIC CONSTANT—The ratio of a given dielectric to the dielectric value of a vacuum. DIFFRACTION—The bending of the paths of waves when the waves meet some form of obstruction. DIPOLE—A 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. AI-2