What does the term 'dBm' measure?

The term 'dBm' specifically measures power levels in relation to 1 milliwatt (mW). It is expressed in decibels (dB) and provides a logarithmic scale to quantify power levels, making it easier to compare different power levels. When you see a value in dBm, it indicates how much power is present compared to a reference level of 1 milliwatt.

This measurement is particularly useful in radio communications because it allows for straightforward comparisons of how strong a signal is, regardless of the actual power that might be used in different scenarios. For instance, a device that outputs 100 mW would be measured as 20 dBm, and this allows engineers and technicians to quickly understand the relative power levels without dealing directly with the raw values in milliwatts.

While the other options touch on related concepts in radio communication systems, they do not accurately define what dBm represents. For example, measuring frequency levels relates to how often a wave oscillates, while signal strength in decibels and voltage levels focus on different attributes of signal measurements but do not specifically tie back to the established power reference of 1 milliwatt that dBm does.