Gira 5110 00 Product Documentation page 40

Figure 10: Frequency key shifting as a modulation method (FSK = Frequency Shift Keying)
Radiation and attenuation of radio signals in buildings
Radio waves with a frequency used for KNX RF can penetrate ceilings or walls in a building.
Depending on the mass (thickness) and conductivity (metallic component, humidity), this is
connected with a greater or lesser energy loss. This loss of transmission energy is also called
attenuation (ratio of transmitted and received radio radiation power).
Radio signals are attenuated by various influences on their journey between the transmitter and
receiver. The precondition for comprehension between the transmitter and receiver is, of
course, that the radio signals of the transmitter still have sufficient energy on reaching the
receiver for the receiver to be able to evaluate the signals.
Almost ideal radiation conditions for electromagnetic radio signals exist in the free-field. The
term "Free-field" refers to a free area, in which radio waves can radiate out more or less
unhindered and interference effects from structures or obstacles have no influence.
If walls and ceilings must be penetrated on the transmission path, then the attenuation - and
thus the radio range - is primarily dependent upon the number, type and consistency of the
construction materials to be penetrated and on the effective wall and ceiling thicknesses. Part of
the incidental radio radiation is reflected on the limit areas and a further part is absorbed. Moist
materials, as is found in new buildings or recently renovated rooms (newly-papered or
plastered) attenuate electromagnetic radio waves to a greater extent.
Material (dry)
Wood, plaster, plasterboard *, glass **
Brick, chipboard plates
Reinforced concrete
Metal grid
Metal, aluminium cladding
*: no metallic stand
**: without metallisation or wire inlay, no leaded glass
Take the attenuation factors of a building into account when selecting the mounting locations of
KNX RF devices (hand-held transmitters, push-button sensors, media couplers). Take into
account too that each KNX RF device is both a transmitter and a receiver on account of the
bidirectionality (e.g. hand-held transmitters with or without LED status display and media
couplers are transmitters and receivers in the same way).
Order No. 5110 00
Software "Media coupler / repeater"
Material thickness
< 30 cm
< 30 cm
< 30 cm
< 1 mm
< 1 mm
Parameters
Transmission
90...100 %
65...95 %
10...70 %
0...10 %
0 %
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