SATEL-EASy+
User guide
Version 1.33
84
17.2 Radio field strength
Radio signal strength must be good enough for successful data transfer. Where field strength is
above a certain level, the operational results are very good. Below this level, a few dB marginal
areas occur in which errors begin to be generated by noise and interference that will eventually
lead to loss of connection.
The field strength is at its optimum level in open space, although increasing distance will still
reduce it. It must also be remembered that one open space has different environmental and
external factors to another, and that the effects on transmission quality must be taken into
account when planning the system.
Ground, ground contours and buildings cause attenuation (loss of energy through absorption)
and reflection of radio waves. Buildings reflect radio waves and therefore the effects of
attenuation are not as acute when transmission is over a short distance.
However, the reflected waves will often be a bit delayed, and when they combine with the direct
radio waves they interact in either a weakening or a strengthening way. This causes the fading
effect in mobile systems. In reality very sharp signal drops spaced about 35 cm apart may occur.
The attenuation may even reach 40 dB, normally less.
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