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Peak power density in the far field of a radio frequency point source is calculated as follows:
P
.
G
Where
=
S
π
2
4
d
Rearranging terms to solve for distance yields:
2.1.1.1
Calculated Distances and Power Compliance Margins
Table 3 shows calculated minimum separation distances d, recommended distances and
resulting power compliance margins for each frequency band and antenna combination.
Band
Antenna
Max
Average
Transmit
Power in
Burst
(Watt)
0.005
Integrated
(7dBm)
5.4
GHz
0.00035
External
4ft Dish
(-4.6dBm)
0.020
EU
Integrated
(13dBm)
5.8
0.0014
External
GHz
4ft Dish
(-1.4dBm)
0.32
Integrated
(25dBm)
FCC
External
2ft Flat
0.32
5.8
Plate
(25dBm)
GHz
External
0.32
6ft Dish
(25dBm)
Notes:
•
The regulations require that the power used for the calculations is the maximum power in
the transmit burst subject to allowance for source-based time-averaging.
S =
power density in W/m
P=
Maximum Average transmit power capability of the radio, in W
G=
total Tx gain as a factor, converted from dB
d =
distance from point source, in m
P
.
=
d
π
4
Variable
P
G
(Watt)
200
0.00250
(23dBi)
2884
0.00017
(34.6dBi)
200
0.01
(23dBi)
2884
0.0007
(34.6dBi)
200
0.16
(23dBi)
631
0.16
(28dBi)
6310
0.16
(38dbi)
Table 3 - Power Compliance Margins
23
2 Avoiding Hazards
2
G
.
S
d
Recom-
(m)
mended
S
2
(W/m
)
Distance
(m)
10
0.06
1
10
0.06
10
0.13
1
10
0.13
1
10
0.5
2
10
0.9
4
10
2.83
10
Power
Compliance
Margin
15.9
7.6
7.6
4.0
4.5
3.5
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