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Fresnel Zone Clearance

Determine Fresnel zone clearance for microwave and fixed wireless links: first-zone radius at an obstacle (or mid-path), the common 60% Fresnel rule for unobstructed paths, and earth bulge at the midpoint. Ideal for pages targeting line of sight, tower height, and point-to-point wireless.

Fresnel Zones Wireless Calculator — How much more than LOS or how high should my antenna be?

This calculator defines how much clearance you need (you will require more than simple Line-of-Sight) and for longer links > 3 Km (2 miles) whether you may have a ground clearance problem.

Enter the Total link distance (in Miles or Kilometers), if you do not enter an Obstacle distance (in Miles or Kilometers) the calculator will use the mid-point for all calculations (Note: assumes antennas at same height). Finally enter the system Frequency in MHz and then click the 'Calculate' button. 1 GHz = 1000 MHz e.g. 2400 = 2.4 GHz.

The calculator will generate the radius of the 1st Fresnel zone only (at the obstacle point or the mid-point), the 60% (no obstacle) radius and the height of the effective earth curvature at the mid-point of the Total link distance using the effective earth radius.

See the calculations and equations used for this wireless calculator.

Total Link Obstacle Distance 1st Fresnel Zone Radius
m at — km: —
ft at — miles: —
Frequency
60% No Obstacle Radius m: —  |  ft: —
Earth Height (mid-point) m: —  |  ft: —

Fresnel Zone Calculations

  1. Calculator normalises all distances to kilometers and meters
  2. Miles to Kilometers = 1.609
  3. Kilometers to miles = 0.621
  4. feet to meters = .3048
  5. meters to feet = 3.28
  6. 1st Fresnel Zone radius (Km) = 17.3 x Sqr root ((Obstacle Distance x (Total Link - Obstacle Distance)) / (Frequency in GHz x Total Link))
  7. 1st Fresnel Zone radius (miles) = 72.6 x Sqr root ((Obstacle Distance x (Total Link - Obstacle Distance)) / (Frequency in GHz x Total Link))
  8. Obstacle free radius = 0.6 x 1st Fresnel Zone radius
  9. Radius of nth Fresnel zone (meter) = sqr root ( (n x wave length x Obstacle distance x (Total Link - Obstacle Distance)) / Total Link )
  10. wave length (meters) = speed of light (299,792,458 m/s) / frequency in Hz
  11. Earth curvature calculation = (Total Link)2 / (8 × effective earth radius)
  12. effective earth radius = 4/3 * Earth radius
  13. Earth radius = 3963 miles, 6378 Km
Disclaimer: Due to the nature of radio frequency propagation and the numerous factors that can affect operating range we do not guarantee that you will achieve any specific range for your application. These wireless calculators are for estimation purposes only. L-com does not guarantee their accuracy or applicability. L-com cannot be held liable for wireless installations based on these tools. Customers should use these tools at their own risk. After you are finished on this page, please visit our line-up of wireless antennas.

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