Fresnel Zone Calculator

What Is a Fresnel Zone?

Fresnel zones are ellipsoidal regions along a radio link between a transmitter and receiver. The first Fresnel zone must stay mostly clear of obstacles to avoid excessive diffraction loss on line-of-sight paths.

Fresnel Zone Radius Formula

$$ r_n = \sqrt{\frac{n \lambda d_1 d_2}{d_1 + d_2}} \qquad \lambda = \frac{c}{f} $$

$r_n$ is the radius of the $n$th zone at the point where distances to the endpoints are $d_1$ and $d_2$. $\lambda$ is wavelength from frequency $f$ and speed of light $c$. Engineers usually ensure at least 60% of the first zone ($n=1$) is unobstructed.

How to Use This Calculator

Enter zone number, carrier frequency, and the two path segment lengths from the obstacle to each endpoint. The tool computes wavelength and Fresnel radius in your chosen units.

Related tools: Wavelength Calculator and Dipole Calculator.

Frequently Asked Questions

Why is the first Fresnel zone most important?

Obstructions in the first zone cause the largest signal degradation. Keeping it clear preserves line-of-sight link budget.

What are d1 and d2?

They are distances from the clearance point along the path to the transmitter and receiver respectively. Their sum is the total link length.

How is wavelength calculated?

Wavelength equals c divided by frequency. This calculator uses c equals 299792458 m/s.

Do I need full clearance of the zone?

Full clearance is ideal. Many links plan for at least 60% first-zone clearance to limit diffraction loss.

Does this apply to microwave and Wi-Fi links?

Yes. Any point-to-point RF link where Fresnel clearance matters, including cellular backhaul and wireless ISP paths.

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Fresnel Zone Calculator

What Is a Fresnel Zone?

Fresnel Zone Radius Formula

How to Use This Calculator

Frequently Asked Questions

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