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PHOENIX CONTACT
105542_en_05
General formula:
free space attenuation [dB] = 32.4 + 20 x log(f) + 20 x log(d)
Formula for 2.4 GHz:
free space attenuation [dB] = 100 + 20 x log(d)
Formula for 868 MHz:
free space attenuation [dB] = 91.17 + 20 x log(d)
f = transmission frequency in MHz
d = distance between the antennas in km
The free space attenuation is later included in the system calculation (see Section “Equiva-
lent isotropically radiated power (EIRP)” on page 147).
9000 m
-
-110.3 dB
10 km
-
-111.2 dB
11 km
-
-112 dB
12 km
-
-112.8 dB
13 km
-
-113.4 dB
14 km
-
-114.1 dB
15 km
-
-114.7 dB
16 km
-
-115.3 dB
17 km
-
-115.8 dB
18 km
-
-116.3 dB
19 km
-
-116.7 dB
20 km
-
-117.2 dB
21 km
-
-117.6 dB
22 km
-
-118.1 dB
23 km
-
-118.5 dB
24 km
-
-118.8 dB
25 km
-
-119.2 dB
Table 8-6
Free space attenuation
Distance [...]
Attenuation at 2.4 GHz [...]
Attenuation at 868 MHz [...]