In VHF communication, what term is used for the primary method of wave propagation?

In VHF communication, the primary method of wave propagation is line-of-sight propagation. This term refers to the transmission of radio waves between two points that are in direct visual contact with each other, without any significant obstructions. VHF waves typically operate in the frequency range of 30 MHz to 300 MHz, where the curvature of the Earth plays a significant role in limiting connectivity. For effective communication, both the transmitting and receiving antennas need to be at a height sufficient to avoid any barriers.

Line-of-sight propagation is most effective in situations where there are no obstacles like hills, buildings, or heavy foliage that might deflect or absorb the radio waves. This method is particularly important for marine communications, where many vessels rely on VHF radios to maintain contact with each other and with shore stations.

While other propagation methods, such as tropospheric scattering and surface wave propagation, are used in different contexts or circumstances, they are not the primary means of propagation for VHF communications compared to line-of-sight. Skywave propagation is also not applicable in the VHF range, as it primarily pertains to higher frequency communications where the ionosphere reflects radio waves back to Earth.