This calculator estimates the radius of the first Fresnel zone, essential for analyzing the propagation of radio waves between two antennas. It allows you to assess whether obstacles are interfering with the signal and optimize the alignment for a lossless link.
Useful for telecom engineers, wireless network installers and radio propagation students seeking to guarantee optimal direct visibility between two points.
Formulas
Radius (m) = 17.31 × √( D km / (4 × f GHz ) )
Radius (ft) = 72.05 × √( D miles / (4 × f GHz ) )
Explanation of formulas
- D represents the distance between the antennas (in kilometers or miles).
- f is the frequency of the signal (in GHz).
- The square root of the D/f ratio determines the size of the Fresnel zone, larger at low frequency and long distance.
- Sufficient clearance of this area guarantees optimal transmission of the radio signal.
Calculation of the Fresnel zone for a 10 km link at 5 GHz
Input : D = 10 km, f = 5 GHz
Output : Radius ≈ 12.26 meters
Benefits and uses
- Evaluates losses due to obstacles in radio links.
- Helps position antennas for clear visibility.
- Essential in planning long-range microwave and Wi-Fi links.
- Practical tool for engineers and field technicians.