Where is HF communication typically used instead of VHF?

HF communication is typically used over the Atlantic due to the limitations of VHF communication at long distances. VHF radio operates effectively for line-of-sight communication, which works well at lower altitudes and shorter distances, particularly over land where radio signals can be reflected and refracted by terrain. However, over oceans like the Atlantic, the vast distances involved mean that VHF may not provide reliable coverage as aircraft fly further away from shores.

HF, or High Frequency communication, is ideal for these long-range communications. It can reflect off the ionosphere, allowing signals to travel over hundreds or even thousands of miles, making it the preferred choice for aircraft flying over oceans where they are far from ground-based VHF stations. This capability is vital for maintaining communication over such extensive and remote areas, ensuring that air traffic control can monitor and guide aircraft effectively.

In contrast, areas like vast deserts or mountainous regions might require different considerations for communication based on local terrain and the operating environment. Urban airspace typically relies on VHF systems due to the dense network of ground stations providing coverage and the proximity of aircraft. Consequently, the Atlantic is the appropriate context in which HF communication becomes crucial due to the distance and operational requirements of oceanic flights.