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Attenuation

refers to any reduction in the strength of a signal (loss). It is usually measured in decibels (dB) which is a logarithmic term that ratios the output voltage or power as a function of input voltage or power. As an example, 3dB loss is equivalent to 30% loss of voltage and 6dB loss is equivalent to 50% loss of voltage. In the case of power, 1.5dB loss is equivalent to 30% loss of power and 3dB loss is equivalent to 50% loss of power. Typically, cables are rated in dB loss per 100 feet.
 

AP = 10log (POUT /PIN ), where AP = power attenuation
AV = 20log (VOUT /VIN ), where AV = voltage attenuation