What is one disadvantage of microwave systems in telecommunications?

Microwave systems are commonly used in telecommunications due to their ability to transmit data over long distances without the need for physical cables. However, one notable disadvantage of these systems is their vulnerability to environmental conditions, such as fog. When microwave signals travel through the atmosphere, they can encounter obstacles, and fog can scatter these radiated beams. This scattering can lead to signal degradation or loss of clarity, which may negatively impact communication quality.

In this context, while other options highlight certain strengths or features of microwave systems, they do not identify a disadvantage. The reliability and stable frequencies associated with microwave systems contribute positively to their performance, and the mention of underground cables is irrelevant since microwave transmission itself is not dependent on such infrastructures. The scattering effect from fog distinctly impacts the effectiveness of microwave systems, making it a crucial consideration in their deployment and operation in various environments.