Transmission Field - Siemens FDCW221 Technical Manual

6.2

Transmission field

Building Technologies
Fire Safety & Security Systems
In free environmental conditions, the field strenght decreases by 1/r²; i.e. with
double distance the attenuation increases by 6 dB. In buildings this factor is, as a
5
first approximation, 1/r
approx. 16 to 17 dB.
The following table shows the correlation between the distance and attenuation in
case of intervisibility in the building.
Distance [m] 40
Attenuation [dB] 90
Maximum values: Distance 40 m / Attenuation 90 dB
Table for the conversion to linear values
Attenuation factor 1
Attenuation [dB] 0
The transmission field in the building is influenced by walls or obstacles. To be able to make a
statement on the attenuation, construction elements such as walls, ceilings, etc. must be exactly
analysed.
Fig. 8 Radio attenuation when penetrating obstacles
, i.e. with double distance the attenuation increases by
30 25 20 15
83 79 74 67
4 10 50 100
6 10 17 20
Project engineering
10 5
57 40
1000
30
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11.2007