Which factor primarily affects the range of VHF radio transmission?

The factor that primarily affects the range of VHF radio transmission is antenna height and local terrain. VHF radio waves travel primarily by line of sight, which means that the height of the antenna can significantly extend the range of transmission. A higher antenna allows the radio waves to propagate further, especially over the horizon, because it minimizes obstructions like buildings, trees, and other geographical features. Additionally, local terrain plays an important role; areas with hills, mountains, or other obstacles can hinder the effective range due to blocking or reflecting the signal.

While weather conditions can influence radio communications to some extent, including phenomena like temperature inversions or precipitation that may affect signal propagation, the primary determinant remains the physical landscape and the effective elevation of the transmitting and receiving antennas. The other options, such as the color of the vessel or the type of fuel used, do not have any significant impact on the VHF radio range. The VHF signal operates on electromagnetic principles that are not influenced by these characteristics. Therefore, understanding the relationship between antenna height, local terrain, and radio wave propagation is key in optimizing VHF communication range.