A brief overview of BALUN types and their applications
1. There are two main types of baluns:
-
Current baluns (Guanella) → Enforce equal currents, suppress common-mode currents.
-
Voltage baluns (Ruthroff) → Enforce equal voltages but do not suppress common-mode currents.
2. Each type has its own benefits:
- Voltage baluns effectively transform impedance but may introduce unwanted RF on the feedline, depending on the type of UNUN, ferrite core type and winding technique used.
- Current baluns improve balance and reduce feedline radiation, but may not always provide the desired impedance transformation.
3. A hybrid (combination of both) is often the best solution:
- Stacking a voltage balun (ruthroff or autotransfer) and a current balun (guanella) provides both proper impedance matching and common-mode current suppression.
-
This approach outperforms using only one type, especially in real-world antenna setups where imbalances exist.
When to Use an UNUN Instead of a BALUN
- BALUN (BALanced to UNbalanced): Used for dipoles, loops, and other balanced antennas.
- UNUN (UNbalanced to UNbalanced): Used for end-fed wires, verticals, and other unbalanced antennas.
Mini-FAQ
- Which should I choose for a dipole? — A current balun (Guanella) to enforce current balance and suppress common‑mode currents.
- When is a voltage balun useful? — When a specific turns‑ratio impedance transformation is needed; add a choke for common‑mode control.
- UNUN vs BALUN? — Use a BALUN for balanced antennas; use an UNUN for unbalanced antennas like end‑fed wires and verticals.
Interested in more technical content? Subscribe to our updates for deep-dive RF articles and lab notes.
Questions or experiences to share? Feel free to contact RF.Guru.