Balun
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A balun is a device designed to convert between balanced and unbalanced electrical signals, such as between coaxial cable and twin-lead (pronounced lēd like reed, not lĕd like red).
This is almost always done through the use of a small isolation transformer, with the earth ground or chassis ground left floating or unconnected on the balanced side. This transformer can then also perform impedance matching at the same time. A balun generally has no other functional purpose except for compatibility between systems.
The most common uses of baluns are:
- In television, amateur radio, and other antenna installations and connections, to convert between ribbon cable (balanced) and coaxial cable (unbalanced) or to directly feed a balanced antenna with (unbalanced) coax.
- In audio applications, to convert between high impedance unbalanced and low impedance balanced lines.
- In power line communications, baluns are used in coupling signals onto a power line.
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Tvbalun.jpg
Tvbalun.jpg
A 300-to-75-ohm balun
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Audiobaluns.jpg
Audiobaluns.jpg
Audio transformers
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Balun.jpg
Balun.jpg
Simple homemade balun
Simple homemade 1:1 balun using a toroidal core and coaxial cable.
References
- Building and Using Baluns and Ununs: Practical Designs for the Experimenter, Jerry Sevick, 1996.
- Balun design for radio-communications and scientific purposes (http://www.radiondistics.com)de:Balun