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Chameleon Knowledge Base · The Complete Online HF Antenna Handbook

What Is a 4:1 Balun?

A 4:1 balun nominally transforms impedance by four while interfacing balanced and unbalanced circuits, such as about 200 ohms to 50 ohms under its design conditions.

Feed Lines & RF Components Matching & Isolation Devices Reviewed 2026-07-14
Start with the function: A 4:1 balun nominally transforms impedance by four while interfacing balanced and unbalanced circuits, such as about 200 ohms to 50 ohms under its design conditions.

What the label leaves out

Real antenna impedance is complex and frequency-dependent, so a four-to-one ratio does not guarantee a low SWR. Current and voltage implementations also control common mode differently.

The mistake to avoid

Using a 4:1 balun because a folded dipole is “300 ohms” ignores installation height, feed-point impedance, line transformation, and the balun’s real load range.

A sound installation approach

Measure or model the actual load, decide whether balance and common-mode control are required, select the correct topology and rating, then verify loss, heat, SWR, and line current.

System boundary

Use current manufacturer documentation, measured RF behavior, the building grounding system, and applicable electrical and lightning requirements. A ratio, DC continuity check, or inline protective device does not establish complete-system safety or efficiency.

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