Which frequency range corresponds to High Frequency (HF) used in aviation?

Which frequency range corresponds to High Frequency (HF) used in aviation?

• A. 3-30 MHz
• B. 30-300 MHz
• C. 0.3-3 MHz
• D. 300-3000 MHz

Answer: (A)

High Frequency aviation communications use the 3 to 30 MHz range. This band is ideal for long-distance, over-the-horizon transmission because signals can reflect off the ionosphere and be received far beyond the aircraft’s line of sight. That ionospheric propagation is what makes HF essential for oceanic and remote-area flights where VHF signals wouldn’t reach. In contrast, the 30-300 MHz range is VHF and is used for short-range, line-of-sight air-ground communications, which is why it doesn’t serve long-distance needs. The 0.3-3 MHz (MF/LF) and 300-3000 MHz (UHF) ranges have other typical uses and propagation characteristics that don’t provide the same horizon-spanning reliability as HF for aviation.

High Frequency aviation communications use the 3 to 30 MHz range. This band is ideal for long-distance, over-the-horizon transmission because signals can reflect off the ionosphere and be received far beyond the aircraft’s line of sight. That ionospheric propagation is what makes HF essential for oceanic and remote-area flights where VHF signals wouldn’t reach.

In contrast, the 30-300 MHz range is VHF and is used for short-range, line-of-sight air-ground communications, which is why it doesn’t serve long-distance needs. The 0.3-3 MHz (MF/LF) and 300-3000 MHz (UHF) ranges have other typical uses and propagation characteristics that don’t provide the same horizon-spanning reliability as HF for aviation.