ARRL Technician Practice Exam

Why are direct UHF signals rarely heard from stations outside your local coverage area?

1. UHF signals are too weak to transmit that far

2. UHF signals are usually blocked by buildings

3. UHF signals are usually not reflected by the ionosphere

4. UHF signals are absorbed by the atmosphere

The correct answer is: UHF signals are usually not reflected by the ionosphere

Direct UHF signals are rarely heard from stations outside your local coverage area primarily because UHF signals are usually not reflected by the ionosphere. The ionosphere is a layer of the Earth's atmosphere that can reflect certain frequencies of radio waves, allowing them to travel over long distances. However, UHF frequencies, which typically range from 300 MHz to 3 GHz, predominantly pass through the ionosphere rather than being reflected. This characteristic makes UHF signals more suitable for line-of-sight communication, as they tend to follow the curvature of the Earth only over relatively short distances. Therefore, any UHF communication typically remains within the local coverage area unless other propagation methods are utilized, such as repeaters or satellite communication. In contrast, other factors, while they can affect UHF signals, do not primarily account for the reduced range in this context. For example, while UHF signals can be influenced by buildings and atmospheric conditions, these factors are generally secondary compared to the fundamental behavior of UHF signals concerning the ionosphere.