Wi-Fi Range Calculating Utility at 11Mbps 802.11b 2.4GHz
- EIRP in RED indicates that the power is above the legal limit in Europe (excluding France where the limit is 7bBm.
- The range quoted is the theoretical range and does not take into account loss due to obscured fresnel zones or diffraction loss.
- The range quoted is with a 10db headroom to allow for signal fade.
Range Calculating Utility at Variable Rate 802.11a 5.8GHz
At the moment it is difficult to get the information required from the manufacturers of equipment to produce meaningful results for 802.11a as there is little equipment currently available that has external connectors. These figures are therefore based on one vendor's equipment only.
Note how the range drops considerably when the transmission speed is increased. It should be noted that 802.11a at 6mbps is roughly similar in real performance terms to 802.11b at 11Mbs.
- EIRP in RED indicates that the power is above the legal limit in the United Kingdom. 802.11a is not yet legal in all European Union countries
- The range quoted is the theoretical range and does not take into account loss due to obscured Fresnel zones or diffraction loss.
- The range quoted is with a 10db headroom to allow for signal fade.
mW to dBm Conversion
Fresnel Zone Size at Given Distance 802.11a/b/g 2.4GHz/5.4GHz
The Fresnel zone is the radius around the center of the line of site beam that must be clear from obstruction to prevent signal loss. If 50% of the Fresnel zone is obstructed, there will be a corresponding 6db drop in signal strength.
The Fresnel zone appears as an ellipse between the two end points of the link and is widest in the middle of the path.
The height of the aerials off the ground required for a point to point link over flat terrain is the fresnel distance+ the earth's curvature over that distance.
