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Fresnel Zone Calculator

Enter frequency and path length to get the radius of the first Fresnel zone and the 60% clearance you need at any point along the link.

How to use the result

The first Fresnel zone radius at a point is the square root of λ × d1 × d2 / D. Keep at least 60% of it free from obstacles: with that clearance the loss is close to free space. A ridge touching the line of sight costs about 6 dB, and more if it goes into the path. Check the real terrain between your sites on the coverage map, where the profile with the Fresnel zone is drawn for you. Background: line of sight versus diffraction.

Explore more

ToolsRadio horizon, free-space path loss and Fresnel zone calculators. Radio Horizon CalculatorLine-of-sight range from antenna heights. Free-Space Path Loss CalculatorPath loss in dB and received power for any link. How it worksThe model behind the map: ionosphere, terrain, diffraction and noise.

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Coverage values are estimates computed by MFH and are indicative only. Elevation data: SRTM, NASA/USGS (public domain). Methodology · About and limits · Live HF propagation data

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