Extreme Networks Extreme Wireless Site Preparation And Installation Manual page 9

Figure 1: Fresnel Zone and Line of Sight Clearance
The radius can be calculated using the following formula:
Where
D = Distance between the antennas in kilometers
f = Frequency in GHz
60% of the Fresnel Zone has to be clear of obstructions to be line of sight. In addition to the Fresnel
Zone height requirement, earth curvature may become a factor in paths longer than 2 Km. The
additional antenna height can be calculated using the following formula:
Where
D = Distance between the antennas in kilometers
H = Height required to overcome earth curvature
and Table 5 on page 10 lists typical antenna height requirements.
Table 4: Typical Antenna Height Requirements—2.4 GHz
Distance between Tx and
Rx antennas (km)
2
5
10
15
ExtremeWireless™ External Antenna with Wave 2
Fresnel Zone radius
(meters)
7.9
12.5
17.67
21.64
Earth curvature (meters)
0.08
0.49
1.94
4.37
AP Site Preparation
Minimum antenna height
requirements (meters)
7.98
12.99
19.61
26.01
9