Signal Attenuation
Signal attenuation or signal loss occurs even as the signal passes through air. The loss of signal strength is more pronounced as the signal passes through different objects. A transmit power of
20 mW is equivalent to 13 dBm. Therefore, if the transmitted power at the entry point of a plasterboard wall is at 13 dBm, the signal strength is reduced to 10 dBm when exiting that wall.
This table shows the likely loss in signal strength caused by various types of objects.
Signal Attenuation Caused By Various Types of Objects

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