What does balun mean?
A balun is a specialized component used in radio-frequency engineering to connect a balanced system to an unbalanced one — hence the name, a contraction of 'balanced-to-unbalanced.' In practice, this usually means joining a symmetric antenna, such as a dipole fed at its centre, to asymmetric coaxial cable. Beyond simple connection, a well-designed balun suppresses unwanted currents that would otherwise flow on the outside of a cable shield, which can distort an antenna's radiation pattern and introduce interference. Baluns also frequently perform impedance transformation, with common ratios including 1:1 and 4:1 depending on the application. The term belongs chiefly to the vocabulary of professional radio engineers and amateur radio operators, where choosing the right balun — whether a simple choke made from coiled coax or a purpose-built transformer — is a routine part of building and tuning antenna systems.
nounA device used to connect a balanced line or load (such as a dipole antenna) to an unbalanced line or source (such as coaxial cable), converting between the two while managing impedance and rejecting unwanted currents.
- A radio-frequency device that interfaces a balanced transmission line or antenna with an unbalanced feed line such as coaxial cable.
"The technician fitted a balun at the antenna feed point to match the coaxial cable to the balanced dipole."
"Without a balun at the feed point, the outside of the coax shield can radiate and distort the antenna's pattern."
"He wound his own choke balun by coiling several turns of the coax into a loop near the transmitter."
Regular English pluralization; standard in amateur radio and engineering writing.
"The club's spare-parts box held a drawer full of assorted baluns."
Its name is literally a mash-up: 'bal' for balanced, 'un' for unbalanced — one of the few electronic components whose name is its own job description.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of balun
The word 'balun' was coined as a portmanteau of 'balanced' and 'unbalanced', reflecting exactly what the device does. It emerged in mid-twentieth-century radio engineering literature as coaxial feed lines became widespread alongside older balanced antennas. Because it is a modern English blend rather than a borrowing, it has no true cognates in other languages, though equivalent terms exist in other languages' technical vocabularies.
How balun is actually used
A technical term used almost exclusively in radio engineering and amateur ('ham') radio contexts; plural is 'baluns'.
Easily confused with balun
A ballast regulates current in electrical circuits such as fluorescent lamps, whereas a balun specifically converts between balanced and unbalanced transmission lines in radio-frequency systems.