What do negative dB values mean?


Negative dB Readings: In the context of signal testing and measurement, dB readings can indeed be negative. This typically indicates that the signal strength is less than a predefined reference level. Negative dB readings are not uncommon, especially when dealing with signal losses or attenuation in cable testing. For example, when testing return loss your reading is always negative. The formula for return loss is 10log(Pr/Pi). With Pr being reflected power and Pi being the Incident power (power measurement before losses). The reflected power cannot be larger than the incident power so the radio will always be between 0 and 1, giving a negative dB value. 

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