What does the term 'free-space loss' refer to?

The term 'free-space loss' specifically refers to the reduction in signal strength as it propagates through free space, which is an unobstructed environment. This phenomenon occurs as the signal travels over distance, where factors such as the distance between the transmitter and receiver and the frequency of the signal come into play. In free-space conditions, the signal spreads out uniformly over an area that increases with distance, leading to a decrease in power density and therefore the strength of the received signal.

While physical barriers can contribute to signal loss, this is more accurately described in terms of obstruction loss rather than free-space loss. Atmospheric absorption affects signals in specific frequency ranges, generally at higher frequencies, but does not define the concept of free-space loss either. Interference from other signals refers to additional signal degradation not associated with the intrinsic properties of signal propagation in free space. Thus, the correct understanding is that free-space loss is a fundamental concept related to signal propagation in an ideal and unobstructed environment.