Which frequencies are normally only useful for distances within the line of sight?

The correct answer relates to VHF, or Very High Frequency, which typically operates in the frequency range of 30 MHz to 300 MHz. VHF is well known for its line-of-sight propagation characteristics, meaning it is most effective for communication over relatively short distances, typically up to about 100 miles, depending on the environment and equipment used.

VHF signals can be blocked or degraded by physical obstacles like buildings and hills, which further emphasizes their reliance on line-of-sight conditions for effective transmission. They are commonly used in services such as FM radio broadcasting, television broadcasts, and two-way radio communications, all of which are generally designed for local coverage.

In contrast, UHF (Ultra High Frequency), HF (High Frequency), and SHF (Super High Frequency) can have different propagation characteristics in various situations. UHF can also provide line-of-sight communication but is often used for longer distances in some applications due to its ability to penetrate buildings better than VHF. HF signals can bounce off the ionosphere and are capable of covering much greater distances, making them less dependent on line of sight. SHF frequencies are generally used for satellite communications and radar, which again do not predominantly rely on line-of-sight principles in the