Safety Information
2.3 Safety distance to transmitter antenna
SIMATIC RF600
System Manual, 06/2019, J31069-D0171-U001-A22-7618
21
2.3.2
Minimum distance to antenna in accordance with ETSI
At a transmission frequency of 900 MHz, the wavelength of the electromagnetic wave
λ
is
approximately 0.34 m. For distances less than 1
λ
in the near field, the electrical field
strength (1/r) diminishes exponentially to the power three over distance, and for distances
greater than 1
λ
, it diminishes exponentially to the power two over distance.
The horizontal line at 41.25 V/m marks the "safety limit value".
For the maximum permitted transmit power (1/r
2
) in accordance with ETSI (2 W ERP), the
"safety distance" is d = 0.24 m. This means that personnel should not remain closer than 24
cm to the transmitter antenna for extended periods (for several hours without interruption).
Remaining within the vicinity of the antenna for a brief period, even for repeated periods (at a
distance < 0.24 m), is harmless according to current knowledge.
Distance to transmitter antenna [m]
Feld strength [V/m]
% of limit value
1
10
24
5
2
5
If the transmitter power is set lower than the highest permissible value (2 watts ERP), the
"safety distance" reduces correspondingly.
The values for this are as follows:
Radiated power ERP [W]
Safety distance to transmitter antenna [m]
2.0
0.24
1.0
0.17
0.5
0.12
