User's Manual

27
Peak power density in the far field of a radio frequency point source is calculated as follows:
Rearranging terms to solve for distance yields
S
GP
d
.4
.
π
=
2.1.1.1 Calculated Distances and Power Compliance Margins
959HTable 3 shows calculated minimum separation distances d, recommended distances and
resulting power compliance margins for each frequency band and antenna combination.
Variable Band Antenna Max
Average
Transmit
Power in
Burst
(Watt)
P (Watt) G S
(W/m
2
)
D
1
(m) Recom-
mended
Distance
(m)
Power
Compliance
Margin
2.5 GHz Integrated 0.25 0.125
63
(18dBi) 10 0.25 2 8
5.4 GHz Integrated
0.005
(7dBm) 0.0025
200
(23dBi) 10 006 1 16
Integrated
0.32
(25dBm)
0.16
200
(23dBi)
10 0.5 2 4
External
2ft Flat
Plate
0.32
(25dBm)
0.16
631
(28dBi)
10 0.9 4 4.5
5.8 GHz
External
6ft Dish
0.32
(25dBm)
0.16
6310
(38dbi)
10 2.83 10 3.5
1. Calculated
Table 3 - Power Compliance Margins
Notes:
1. 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.
2. At 5.4GHz the product is generally to a fixed EIRP which can be achieved with the
Integrated Antenna. If there are no EIRP limits, use the distance calculations for 5.8GHz.
3. At 5.8GHz, for antennas between 2ft and 6ft, alter the distance proportionally to the
antenna gain.
4. At 2.5GHz, with a 4/12ft dish, the safe distance is increased to 08/2.4m.
Where S = power density in W/m
2
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
2
4
.
d
GP
S
π
=