Which frequency band is primarily used for long-range two-way voice or data link transmission?

The frequency band primarily used for long-range two-way voice or data link transmission is HF, or High Frequency. This band operates in the range of 3 to 30 MHz and is well-known for its ability to support communications over considerable distances, primarily due to its capability to reflect off the ionosphere. This characteristic makes HF suitable for global communications, especially in situations where other bands may be limited, such as beyond the line of sight or when operating over oceanic regions.

HF radios can be used for various forms of communication, including voice transmissions and digital data links, making them versatile for aircrew operations over long distances. In contrast, the other frequency bands either have shorter range capabilities or are better suited for specific applications. For instance, VHF (Very High Frequency) is typically used for line-of-sight communications and operates best within a limited range, while UHF (Ultra High Frequency) also functions well for shorter distances and is mainly used for ground communications. SATCOM (Satellite Communication), while being excellent for long-distance communication as well, operates via satellite, requiring specific equipment and infrastructure that might not always be available in every operation.