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LANCOM Reference Manual LCOS 3.50 ̈ Chapter 11: Wireless LAN – WLAN
258
Wireless LAN – WLAN
To ensure that the Fresnel zone 1 remains unobstructed, the height of the
antennae must exceed that of the highest obstruction by this radius. The full
height of the antenna mast (M) should be as depicted:
M = R + 1m + H + E (Earth's curvature)
The height of the Earth's curvature is calculated from E = d² * 0,0147 – even
at a distance of 8 km that results in almost 1m!
Example: With a distance of 8 km between the antennae, the result in the
2.4-GHz band is a mast height above the level of the highest obstruction of
approx. 13 m, in the 5-GHz band 9 m.
11.5.2 Antenna power
The power of the antenna must be high enough to ensure acceptable data
transfer rates. On the other hand, the country's legal limitations on
transmission power should not be exceeded.
The calculation of effective power considers everything from the radio module
in the transmitting access point to the radio module in the receiving access
point. In between there are attenuating elements such as the cable, plug
Fresnel zone 1
Radius R
Safety margin:
Obstruction height H
Earth's curvature E