Planning
Transmission field
4
45 | 82
Building Technologies
009865_m_en_--
Fire Safety
2015-11-06
4.3 Transmission field
In the open, the field strength falls with a factor of 1/r², i.e. a doubling of distance in
the open equates to a 6 dB increase in damping. In buildings, the factor in a first
approximation is 1/r
5
, i.e. a doubling of distance means that damping increases by
around 6 to 17 dB.
The table below illustrates the relationship between distance and damping for the
line of sight in the building:
Distance [m]
40
30
25
20
15
10
5
Damping [dB]
90
83
79
74
67
57
40
Maximum values: Distance 40 m / damping 90 dB
Table for converting to linear values
Damping factor
1
4
10
50
100
1000
Damping [dB]
0
6
10
17
20
30
The transmission field in the building is affected by walls and obstacles. These
constructions (walls, ceilings etc.) must be analyzed in detail to obtain a
statement on damping.
Radio damping when passing through obstacles
The approximate values listed in the table should be added together for
constructions encountered along the radio link in order to determine the actual
damping at the receiver location.
Construction
Additional damping
Room divider
<1 dB
Dry bricks
around 6 dB
Dry concrete
around 6 dB
Lime sand brick
around 8 dB
Planar lime sand brick elements
around 8 dB
Timber frame wall
around 8 dB
Timber panel wall
around 8 dB
