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Chameleon Knowledge Base · The Complete Online HF Antenna Handbook

What Is an Unun?

Learn what an unun is, how it works, and where it is used in amateur radio antenna systems.

Feed Lines & RF Components Matching & Isolation Devices Reviewed 2026-07-14
Short Answer: Learn what an unun is, how it works, and where it is used in amateur radio antenna systems.

Explanation

Overview An unun (short for unbalanced-to-unbalanced transformer ) is a matching device used to connect two unbalanced systems while transforming impedance as required. Unlike a balun, an unun does not convert between balanced and unbalanced circuits. Primary Functions Impedance transformation. Efficient power transfer. Matching unbalanced antennas. Supporting broadband antenna operation. Common Ratios 1:1 4:1 9:1 49:1 64:1 Typical Applications End-fed antennas. Random-wire antennas. Long-wire antennas. Broadband matching networks. Important Note An unun provides impedance transformation but does not necessarily suppress common-mode current. Depending on the antenna system, an additional common-mode choke may still be recommended. Applied to Chameleon Products Many Chameleon broadband and end-fed antenna systems use carefully engineered ununs to provide wide frequency coverage while maintaining efficient impedance transformation across multiple amateur bands. Related Articles What Is a Balun? What Is Common-Mode Current? What Is Feed-Line Radiation? What Is Characteristic Impedance? Related Products CHA EMCOMM III CHA LEFS Series CHA OCF40

The exact result depends on the complete station: frequency, geometry, feed line, matching network, return-current path, environment, operating power, and the reference plane of any measurement. A low SWR establishes an impedance relationship at that point; it does not by itself prove efficiency, radiation pattern, compatibility, or safety.

What to Verify

  • Use the newest official product guide or primary service documentation.
  • Confirm the exact model, revision, components, configuration, and operating conditions.
  • Begin tests at low power and change one variable at a time.
  • Do not infer compatibility from connector or thread fit.

Learn Next

  • Antenna Selection: A Mission-First Decision Guide
  • Engineering Design Tradeoffs in Portable HF Antennas
  • Antenna Measurement Reference Planes
  • Understanding Common-Mode Current

Source note: Independently synthesized with reference to The ARRL Handbook for Radio Communications, 99th edition (2022), and The ARRL Antenna Book for Radio Communications, 24th edition (2019). Verify changing regulations, services, software, specifications, availability, and safety requirements against current primary sources.