VHF/UHF Propagation

 

VHF (Very High Frequency) and UHF (Ultra High Frequency) radio waves are typically used for communication over shorter distances than HF (High Frequency) radio waves. VHF and UHF radio waves have longer wavelengths than HF radio waves, and they are less affected by the ionosphere. Instead, they are more affected by the terrain and the atmosphere.

Propagation of VHF and UHF radio waves can occur in several ways:

1. Line-of-Sight Propagation: VHF and UHF radio waves travel in straight lines, and they are only able to travel as far as the horizon, or the point where the Earth's surface blocks their path. This is known as line-of-sight propagation, and it is the most common way that VHF and UHF radio waves propagate.

2. Tropospheric Scattering: VHF and UHF radio waves can also be scattered by the atmosphere, allowing them to travel over the horizon. This is known as tropospheric scattering, and it can be caused by temperature inversions, atmospheric turbulence, and other meteorological conditions.

3. Ground-wave Propagation: VHF and UHF radio waves can also propagate along the surface of the Earth, known as ground-wave propagation. This type of propagation is affected by the electrical conductivity of the ground, and it is typically only effective over short distances.

4. Tropospheric Ducting: VHF and UHF radio waves can travel along a layer of air with a relatively constant temperature and humidity, called a duct. This is known as tropospheric ducting, and it can allow VHF and UHF radio waves to travel long distances.

In general, VHF and UHF radio waves are less affected by solar activity than HF radio waves, but they are more affected by the weather and the terrain. When planning communications on the VHF and UHF bands, it is important to take these factors into consideration and to use the appropriate antenna and power to maximize the propagation of the signal.