Skip to main content
Calcimator

Fresnel Zone Calculator

Calculate Fresnel zone clearance radius for wireless link design. Includes earth curvature bulge and minimum antenna height.

Inputs

MHz
km
%

Results

1st Fresnel Zone Radius

12.5 m

≈ 7 adult heights

60% Clearance (Min.)

7.5 m

≈ 4 adult heights

Min Clearance Height

7.87 m

≈ 5 adult heights

2nd Fresnel Zone Radius17.67 m
3rd Fresnel Zone Radius21.64 m
Max Radius (at Midpoint)12.5 m
Earth Curvature Bulge0.37 m
Wavelength0.1249 m
How to Use This Calculator
  1. Enter link frequency (MHz) and total link distance (km).
  2. Set the obstacle position along the path as a percentage of total distance (1% to 99%, with 50% as the worst-case midpoint).
  3. Review the 1st, 2nd, and 3rd Fresnel zone radii at the obstacle location.
  4. Ensure 60% of the 1st Fresnel zone is clear of obstacles for a clean line-of-sight link.
  5. Use the minimum clearance height, which adds the earth curvature bulge to the 60% clearance radius, to specify tower heights or choose alternate path routing.

How the result changes with Frequency

Frequency1st Fresnel Zone Radius60% Clearance (Min.)Min Clearance Height
10,0016.12 m3.67 m4.04 m
35,0013.27 m1.96 m2.33 m
65,0002.4 m1.44 m1.81 m
90,0002.04 m1.22 m1.59 m

What each input means

Frequency
Operating frequency of the wireless link in megahertz
Link Distance
Total distance between transmitter and receiver in kilometers
Obstacle Position Along Path
Position of obstacle as percentage of total path (50% = midpoint, worst case)

How this is calculated

Formula

r = √(n × λ × d₁ × d₂ / D)

Worked example, using the default values

  1. Identify Input Parameters
    Frequency = 2400, Link Distance = 5, Obstacle Position Along Path = 50 = 3 input(s) provided
  2. Calculate 1st Fresnel Zone Radius
    1st Fresnel Zone Radius
    12.5 = 12.5
  3. Calculate 60% Clearance
    60% Clearance = r
    7.5 = 7.5
  4. Calculate Min Clearance Height
    Min Clearance Height
    7.87 = 7.87
  5. Calculate 2nd Fresnel Zone Radius
    2nd Fresnel Zone Radius
    17.67 = 17.67
  6. Calculate 3rd Fresnel Zone Radius
    3rd Fresnel Zone Radius
    21.64 = 21.64

Engine last updated . Checked against 2 independently-derived tests — how we verify calculators.

Related Calculators

The questions that sit next to this one — chosen by subject, including calculators filed under a different category.

RF & Antenna

Antenna Height Calculator

Calculate the required tower height for line-of-sight coverage over a given distance, accounting for earth curvature and remote antenna height.

RF & Antenna

Free Space Path Loss Calculator

Calculate free space path loss (FSPL) from distance and frequency. Includes received signal power estimation.

Telecom Infrastructure

Microwave Link Calculator

Path clearance, fade margin, and availability.

RF & Antenna

Link Budget Calculator

Calculate end-to-end RF link budget from transmitter to receiver, including EIRP, path loss, and link margin.

Traffic Engineering

Sight Triangle Calculator

Calculate clear sight triangle dimensions for intersection safety based on AASHTO guidelines, design speed, and intersection control type.

More in Technology & Computing.