Explanation: At 15 kHz, the wavelength is exceptionally long (20 kilometers). Practical transmitting antennas are electrically very short compared to this wavelength, resulting in extremely low radiation efficiency. A significant portion of the generated power is lost as heat in the antenna system and ground, rather than being radiated as an electromagnetic wave. Additionally, Very Low Frequencies (VLF) are susceptible to high levels of atmospheric noise (sferics from lightning). To overcome these factors—extremely poor antenna efficiency and high ambient noise—and ensure a reliable signal over long ground wave paths, stations operating at 15 kHz must generate exceptionally high power outputs.