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Chameleon Knowledge Base · The Complete Online HF Antenna Handbook

What Is Line-of-Sight (LOS) Propagation?

Learn what line-of-sight propagation is and why antenna height is critical for VHF and UHF communications.

Getting Started HF Fundamentals Reviewed 2026-07-14
Short Answer: Learn what line-of-sight propagation is and why antenna height is critical for VHF and UHF communications.

Explanation

Overview Line-of-Sight (LOS) propagation occurs when radio waves travel directly between two antennas without significant obstruction. LOS communication is the primary propagation mode for most VHF, UHF, and microwave systems. Factors Affecting LOS Antenna height. Terrain. Buildings. Trees. Earth curvature. Radio Horizon The radio horizon generally extends beyond the visible horizon because radio waves experience slight atmospheric refraction. Improving LOS Coverage Increase antenna height. Reduce obstructions. Maintain Fresnel Zone clearance. Applied to Chameleon Products Portable support systems such as the CHA PORTA-MAST can significantly improve line-of-sight coverage by elevating antennas above nearby obstructions. Related Articles What Is Space Wave Propagation? What Are Fresnel Zones? How Does Antenna Height Affect Performance? Related Products CHA PORTA-MAST CHA URT1 MB

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.