What Is the Fresnel Zone Radius & Line-of-Sight Clearance Calculator?
A Fresnel zone is an elliptical volume of space surrounding the line of sight between two antennas.
How Does the Fresnel Zone Radius & Line-of-Sight Clearance Calculator Work?
Calculates the boundary where reflected radio waves travel an extra half-wavelength (lambda/2), producing phase cancellation.
Fresnel Zone Radius & Line-of-Sight Clearance Calculator Formula & Variables
The core mathematical equation utilized by this calculator is expressed as:
r_1 = sqrt{ rac{lambda d_1 d_2}{d_1 + d_2}}, quad ext{Clearance}_{60%} = 0.60 cdot r_1
First Fresnel zone radius where phase difference is less than half a wavelength (180 deg).
How to Use the Fresnel Zone Radius & Line-of-Sight Clearance Calculator
- Input link frequency in GHz, distance from TX to obstacle, and distance from obstacle to RX.
Step-by-Step Example Calculation
10 km Wireless Backhaul (5.8 GHz)
Input Values:
frequencyGhz:5.8
distanceToObstacleKm:4
distanceFromObstacleToRxKm:6
Worked Steps: First Fresnel radius r₁ = 11.15 m; minimum 60% clearance required is 6.69 m above tree canopy/ridge.
Understanding Your Result
At least 60% of the first Fresnel radius must remain completely unobstructed to avoid diffraction loss.
Factors That Affect the Result
- Earth curvature and atmospheric refraction (effective Earth radius k-factor) bend the ray path over long distances.
When Should You Use This Calculator?
- Tower height planning for cellular backhaul, fixed wireless internet (WISP), and microwave relay paths.
Assumptions & Limitations
- Applies to 1st Fresnel zone; assumes homogeneous atmosphere.
Frequently Asked Questions
Calculation Accuracy & Reference Note
Standard telecommunications microwave path engineering model.