Why is the use of dBmV acceptable for expressing power per Hz across channel bandwidth?

The use of dBmV for expressing power per Hz across channel bandwidth is primarily acceptable because a constant 75-ohm impedance is utilized in many communication systems, particularly in cable television and broadband data applications. When power levels are measured in dBmV, which represents decibels relative to one millivolt, it provides a clear and effective way to quantify signal levels in a system that has a specific impedance.

This relationship to a fixed impedance ensures that the power measurements are consistent and can be directly related to the voltage levels at the input of receivers, such as TVs and modems, which are typically designed to operate within that 75-ohm environment. Using dBmV allows for easy interoperability among different devices and systems, as they can all reference the same standard measurement, facilitating communication and signal processing tasks.

The other options do not encapsulate the primary reasoning for using dBmV in this context. While simplifying calculations, standardization, and a relationship to optical power are important in different contexts, they do not specifically focus on the critical aspect of impedance that underpins the practical use of dBmV in telecommunications.