Fresnel Zone Recommendations


The Fresnel (pronounced fre∙NEL) Zone is a three-dimensional volume around the line of sight of an antenna transmission. Objects that penetrate this area can cause the received strength of the transmitted signal to fade. Out-of-phase reflections and absorption of the signal result in signal cancellation.  This article provides some high-level recommendations for installing ePMP radio links which may have objects in the Fresnel zone.


The foliage of trees and plants in the Fresnel Zone can cause signal loss. Seasonal density, moisture content of the foliage, and other factors such as wind may change the amount of loss. Plan to perform frequent and regular link tests if you must transmit through foliage.

Illustration of Fresnel Zones 1,2,3 concept

As a rule of thumb:

  • installers should ensure that at least 60% of the 1st Fresnel zone is clear of obstacles to ensure good signal reception.
  • the maximum obstruction allowable is 40%, but the recommended obstruction is 20% or less
  • signal reflections and deflections are most impactful within Zone 1, and less impactful in Zone 2,3

OFDM technology can often use multi-pathing to an advantage to overcome nLOS, especially in cases where the Fresnel zone is only partially blocked by buildings, “urban canyons”, or foliage. OFDM tends to help especially when obstacles are near the middle of the link, and less so when the obstacles are very near the ODU.

However, attenuation through walls and trees is substantial for any use of the 5.4 GHz and 5.8 GHz frequency bands. Even with OFDM, these products are not expected to penetrate walls or extensive trees and foliage.