Which type of device uses radio waves to connect over a networked area through a base station at a fixed location?

The correct choice is a cell phone. This device operates using radio waves to communicate wirelessly with a base station, which connects to a larger network, such as those used in cellular communication. When a cell phone is in use, it sends and receives signals through nearby cell towers, allowing for voice calls, text messaging, and internet connectivity over a broad area.

In contrast, radar and sonar are technologies that serve different purposes; radar is primarily used to detect objects and determine their distance using radio waves, while sonar does the same using sound waves, often in underwater applications. An electronic warfare device typically refers to systems designed to disrupt or degrade enemy use of the electromagnetic spectrum, rather than facilitating standard communication over networked areas like a cell phone does.