What is difference between HF and VHF?

But the real advantage of HF is skywave propagation, where a single link can span distances as great as 3,000 km (a little less than 1,900 miles) . Skywave propagation occurs when the radio wave is refracted (bent) in the uppermost layer of the atmosphere, called the ionosphere.

This works particularly well over water, and HF Surface Wave can be used to communicate between ships hundreds of miles apart. HF Surface Wave provides a more robust service than Skywave and is particularly suitable for higher speed operation . This can make it an excellent choice for Naval Task Group communication.

VHF operates at a higher frequency range than HF , usually between 30-300 MHz. These transmissions, due to their higher frequency, penetrate through the Ionosphere, with little or no refraction. VHF propagation is ‘line of sight’ in nature and so is restricted to shorter-range communications.

The advantage of the HF band is that radio waves of these frequencies are refracted (bent) by the ionosphere so that the waves return to the Earth’s surface at long distances beyond the horizon ,…

The HF system on an aircraft provides two-way voice communication with or digitally coded signals for ground stations or other aircraft . The HF radio control panel is located where it is easily accessible to the pilot or copilot.

HF- Communication. High frequency (HF) is the ITU-designated range of radio frequency electromagnetic waves (radio waves) between 3 and 30 MHz . It is also known as the decameter band or decameter wave as the wavelengths range from one to ten decameters (ten to one hundred metres).