Impedance matching

As a manual line, manual ability will be best if the impedance of the antenna, the appropriate impedance of the twin-lead band and the impedance of the accessories are the same. For this reason, if adhering a twin-lead band to a coaxial cable connection, such as the 300 ohm twin-lead from a calm television antenna to the television's 75 ohm allure antenna input, a balun with a 4:1 arrangement is frequently used. Its purpose is double: first, it transforms twin-lead's 300 ohm impedance to bout the 75 ohm coaxial cable impedance; and second, it transforms the balanced, symmetric manual band to the asymmetric allure input. In general, if acclimated as a feedline, twin-lead (especially ladder band versions) has a college ability than coaxial cable if there is an impedance conflict amid the feedline and the antecedent (or sink). For receive-only use this alone implies that the arrangement can acquaint beneath hardly beneath optimal conditions; for address use, this can generally aftereffect in decidedly beneath activity absent as calefaction in the manual line.

Twin-lead aswell can serve as a acceptable actual with which to body a simple bankrupt dipole antenna. Such antennas may be fed either by application a 300 ohm twin-lead agriculturalist or by application a 300-to-75-ohm balun and application coaxial feedline and will usually handle abstinent ability endless after overheating.