dBm vs dBmV vs dBuV: Understanding the Differences

This page compares dBm, dBmV, and dBuV, highlighting the differences between them. Input signal levels are often expressed in mV, µV, or nV. However, these units can be quite large, so the more concise dBm, dBmV, and dBuV are commonly used to represent the same signal levels.

There are two fundamental types of voltages: source voltage and potential difference (voltage difference). Let’s break down each unit:

dBm

dBm represents power in decibels relative to 1 milliWatt (mW) and is typically dissipated in a 50 Ohm resistance. The formula to calculate power in dBm is:

Power in dBm = 10 * Log (P watts / 0.001)

Essentially, it’s a logarithmic way to express power compared to a 1 mW reference.

dBmV

dBmV is frequently used in TV receiver contexts where a 75 Ohm impedance is standard, as opposed to the 50 Ohm impedance more common in RF circuits.

dBmV refers to the signal voltage in decibels with respect to a signal level of 1 milliVolt (mV) across a 75 Ohm resistance.

dBuV

dBuV represents the signal voltage measured in decibels relative to 1 microVolt (µV) across a 50 Ohm resistance.

Conversion

You can approximate the dBm value from dBmV by subtracting 113 from the dBmV value.

Example:

100 dBmV ≈ -13 dBm