Calculating Power (dBm and mW) from Peak-to-Peak Voltage

"To calculate the power from peak-peak voltage, the load impedance (Z) must be known. In RF design, the standardized impedance value is 50 ohms, For CATV and video, 75 ohms is common and in audio and telecommunication design, a 600 ohms impedance is often used. Although technically any Z can be used, we will conform to the 50 ohms RF impedance standard on this web page.

The SI unit of power is the watt. In radio, we might see the term dB used. However, dB is a decibel comparison between 2 signals and not an absolute value like the watt. A common and very useful term is dBm. dBm is the measured power ratio in decibels referenced to 1 milliwatt. dBm measures are an absolute power and very useful because both large and small signals are quantified with 1 number. Here are some bullets to contemplate:"


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