Which type of propagation is primarily used for VHF and UHF bands?

The primary type of propagation used for VHF and UHF bands is line-of-sight propagation. This type of propagation occurs when radio waves travel directly from the transmitting antenna to the receiving antenna without significant reflection or refraction. At VHF (30 MHz to 300 MHz) and UHF (300 MHz to 3 GHz) frequencies, the radio waves tend to follow a straight path, which means that the distance over which reliable communication can occur is primarily limited by the curvature of the Earth and any obstructions like buildings or hills.

As frequency increases, the ability of the waves to diffract around obstacles diminishes, making line-of-sight essential for effective communication in these bands. This is why antennas for VHF and UHF communications are often placed at elevated heights to maximize line-of-sight distances.

In contrast, other propagation modes are less effective at these frequencies. For example, skywave propagation involves the reflection of radio waves off the ionosphere, which is more commonly utilized at HF (High Frequency) bands. Ground wave propagation is more effective at lower frequencies, allowing signals to travel along the surface of the Earth, and is typically more relevant for AM broadcasting. Satellite propagation, while relevant, specifically involves signals traveling to and from satellites