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balun(bal -ŭn) See feeder.
a device in the antenna-feeder line of a radio transmitter or receiver that matches an unbalanced feeder with a balanced feeder or antenna, or a balanced feeder with an unbalanced antenna. Baluns are principally used at meter and decameter wavelengths.
At decamenter wavelengths baluns are most often composed of elements that have lumped parameters, such as capacitors, inductance coils, and transformers, and form, for example, single- and multiple-section electric filters (Figure 1,a; see page 26). At meter wavelengths baluns are composed of elements having distributed parameters forming, for example, a quarter-wave sleeve (Figure 1,b), a U-bend (Figure 1,c), or a coaxial-slot coupling (Figure l,d). All such baluns operate in a narrow frequency band; in order to widen the frequency band, various devices, consisting of short-circuited and open-ended stubs, are used to compensate for the mismatch (Figure l,e). Transformer baluns with ferrite cores are often used in feeder lines that carry moderate power (up to 10 kilowatts).
REFERENCESAizenberg, G. Z. Antenny ul’trakorotkikh voln [part 1]. Moscow, 1957.
Lavrov, G. A., and A. S. Kniazev. Prizemnye i podzemnye antenny. Moscow, 1965.
Drabkin, A. L., V. L. Zuzenko, and A. G. Kislov. Antenno-fidernye ustroistva, 2nd ed. Moscow, 1974.
G. A. KLIGER and V. I. KOMISSAROV
balun(BALanced UNbalanced) A device that connects a balanced line to an unbalanced line; for example, a twisted pair to a coaxial cable. A balanced line is one in which both wires are electrically equal. In an unbalanced line, such as a coax, one line has different properties than the other.
|The BNC connector on the left connects to coaxial cable. The screw connectors on the right connect to telephone style twisted wire pairs. (Image courtesy of Black Box Corporation.)|