UnbalunÜbertrager

UnbalunÜbertrager, in English commonly called an unbalun, is a device that converts signals between unbalanced and balanced form. It is used to connect unbalanced transmission lines, such as coaxial cables, to balanced loads like dipole antennas, or to transform impedance while maintaining proper balance. The goal is to minimize undesired current on the shield and to improve common‑mode rejection, which reduces radiated interference and distortions.

Two broad classes are typically used. Transformer-based baluns provide both balance and impedance transformation and come in several winding ratios, such as 1:1, 4:1 and 9:1. A 1:1 balun (often implemented as a choke) suppresses common‑mode currents without changing the matched impedance. A 4:1 or 9:1 balun transforms impedance to match a balanced antenna to a 50-ohm unbalanced feed, enabling efficient power transfer across a useful bandwidth. Ruthroff and Guanella designs describe common winding configurations to achieve wideband performance.

Construction methods vary. Common approaches use ferrite cores with bifilar or coaxial windings to realize the desired ratio, or non‑transformer chokes that block common‑mode currents on the feedline. The choice of core material, winding technique, and enclosure affects bandwidth, power handling, and robustness.

Applications are most prominent in radio communication and antenna systems, where unbalunÜbertrager enable feeding dipoles, verticals, or multi‑element antennas from coaxial cables. They are also used in audio and measurement setups to preserve signal integrity by maintaining balance. Practical design considerations include frequency range, voltage and power ratings, and the need to minimize losses and reflections across the operating band.