Why does the Navy primarily use the upper and lower ends of the mf band?

The primary reason the Navy uses the upper and lower ends of the medium frequency (MF) band is due to their suitability for long-distance communication, which is typically associated with maritime operations. While the commercial broadcast band does extend from 535 to 1,605 kHz, this range is heavily utilized for commercial broadcasting and is crowded with various radio station signals.

Operating at the upper and lower ends of the MF band allows the Navy to utilize frequency ranges that can effectively support long-distance communications, particularly in maritime environments where conditions can promote signal propagation. Frequencies lower in the band can be reflected by the ionosphere at night, allowing for extended range, while higher frequencies may be more suitable during the daytime. Therefore, focusing on these ends of the MF band thus enables the Navy to achieve reliable communication over vast distances, which is crucial for operational effectiveness.