A VLF transmitter (Very Low Frequency transmitter) is a device that emits radio waves at frequencies between 3 kHz and 30 kHz. These low frequencies allow the signals to travel long distances, making them useful for communication with submarines and other remote locations. VLF transmitters are often used for navigation and time signals, as they can penetrate water and earth better than higher frequency signals. The technology behind VLF transmitters involves large antennas and powerful transmitters to generate the low-frequency waves. Due to their long wavelengths, VLF signals can reflect off the ionosphere, enabling them to cover vast areas. This makes them essential for military and maritime operations, as well as for scientific research in atmospheric studies.