Gira 5110 00 Product Documentation page 44

Software "Media coupler / repeater"
Parameters
source are at the receiver with a differing phase location. In many cases, the reflected radio
power is too small to influence the direct path of the radio wave in any significant way. A
receiver can then receive the signal of the transmitter without any interference (Figure 15).
Figure 15: Interference has no effect on the receiver
However, in the worst case, the waves received directly and via reflection are superimposed
unfavourably at the target location, creating a signal which receivers can no longer evaluate
reliably (Figure 16). Positive and negative superposition of radio waves pointing the same way
is also termed interference.
Figure 16: Interference at the receiver prevents reception
Effects from reflections can also be used positively in a building. If possible, RF devices, or their
transmission and reception antennas, can be installed horizontally or vertically in the same
alignment, as the radio wave also swings in the appropriate direction (polarisation). If antennas
are aligned in different ways, then the signal available at the receiver is weakened and thus the
maximum radio range is reduced. The weakening of the signal can be of such magnitude that a
receiver can no longer receive any output radiated directly from the transmitter. However, in
practical terms, reflections may cause a rotation of the polarisation direction, meaning that the
reflected signal reaches the receiver in a weakened form and can also be understood there
(Figure 17).
Figure 17: Reflection allows reception through a change of polarisation
In practice, reflection and interference effects can frequently be changed or used beneficially
through a slight change in the installation location or the installation environment.
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