What is a common use for HF frequencies?

HF frequencies, typically ranging from 3 MHz to 30 MHz, are especially well-suited for long-distance communications due to their ability to reflect off the ionosphere under certain conditions. This characteristic allows HF radio signals to travel beyond the horizon, making them ideal for connecting with stations thousands of miles away.

In contrast, local emergency communications often utilize VHF or UHF frequencies, which are more suitable for shorter-range transmissions. Marine communications generally rely on VHF frequencies for line-of-sight operations, while aviation communications predominantly occur on VHF as well, especially for air traffic control and communication between aircraft and ground stations.

Thus, it is the unique propagation characteristics of HF frequencies that establish them as a reliable choice for long-distance communication.