Ham Radio General Class Practice Test

Which frequency is more likely to support long-distance communications via the ionosphere?

1. HF band

2. VHF band

3. UHF band

4. SHF band

The correct answer is: HF band

The HF band, or High Frequency band, is particularly effective for long-distance communication due to its ability to reflect off the ionosphere, a layer of the Earth's atmosphere that can support radio wave propagation. When radio waves in the HF range are transmitted, they can bounce off the ionosphere and return to the Earth at various distances, allowing signals to travel beyond the line of sight, making communication possible over vast distances. This phenomenon is primarily due to the way the ionosphere interacts with radio waves. HF frequencies typically range from 3 MHz to 30 MHz, which are well-suited for ionospheric reflection, especially during times of high solar activity when the ionosphere is more ionized and can reflect signals effectively. In contrast, the VHF (Very High Frequency), UHF (Ultra High Frequency), and SHF (Super High Frequency) bands are generally not as effective for long-distance communication via the ionosphere. These bands, which operate at higher frequencies, typically have shorter wavelengths that tend to penetrate the ionosphere instead of reflecting off it. Therefore, their propagation characteristics are more suitable for line-of-sight communication and are limited to much shorter distances compared to HF. In summary, the HF band stands out as the optimal choice