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.

Written by Joeri Van Dooren, ON6URE – RF, electronics and software engineer, complex platform and antenna designer. Founder of RF.Guru. An expert in active and passive antennas, high-power RF transformers, and custom RF solutions, he has also engineered telecom and broadcast hardware, including set-top boxes, transcoders, and E1/T1 switchboards. His expertise spans high-power RF, embedded systems, digital signal processing, and complex software platforms, driving innovation in both amateur and professional communications industries.