Radio frequency (RF) sources are devices that generate electromagnetic waves within the radio frequency spectrum, typically ranging from 3 kHz to 300 GHz. These sources can include radio transmitters, cellular base stations, and microwave ovens, which all produce RF signals for various applications, such as communication and heating. RF sources are essential in modern technology, enabling wireless communication systems like Wi-Fi, Bluetooth, and television broadcasting. They work by converting electrical energy into radio waves, which can then travel through the air and be received by antennas, allowing for the transmission of information over long distances.