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Chameleon Knowledge Base · The Complete Online HF Antenna Handbook

What Is LMR-400 Coax?

Learn about LMR-400 coaxial cable, its advantages, and why it is one of the best choices for low-loss amateur radio feed lines.

Getting Started HF Fundamentals Reviewed 2026-07-14
Short Answer: Learn about LMR-400 coaxial cable, its advantages, and why it is one of the best choices for low-loss amateur radio feed lines.

Explanation

Overview LMR-400 is a premium low-loss 50-ohm coaxial cable widely used in amateur radio, commercial communications, military systems, and professional RF installations. Its combination of low attenuation, high power handling, and excellent shielding makes it one of the preferred choices for permanent antenna installations. Advantages Very low attenuation. High power capability. Excellent shielding effectiveness. Outstanding long-distance feed-line performance. Limitations Larger outside diameter. Heavier than portable coaxial cables. Less flexible in cold weather. Typical Applications Permanent HF stations. VHF/UHF base stations. Long feed-line runs. Remote antenna installations. Selection Considerations When feed-line length is significant, the lower attenuation of LMR-400 can substantially improve transmitted and received signal performance compared with smaller coaxial cables. Applied to Chameleon Products LMR-400 is an excellent choice for permanent Chameleon antenna installations and is also used as the radiating element in selected Chameleon magnetic loop products, where its electrical and mechanical characteristics contribute to efficient loop performance. Related Articles

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.