ARRL Technician Practice Exam

Why are UHF signals generally more effective inside buildings than VHF signals?

1. They travel longer distances

2. They have a shorter wavelength

3. They skip off surfaces better

4. They operate at higher power

The correct answer is: They have a shorter wavelength

UHF signals are generally more effective inside buildings than VHF signals primarily due to their shorter wavelength. The shorter wavelength of UHF signals allows them to better penetrate through building materials such as walls, windows, and roofs. This increased ability to pass through obstacles results in a stronger and clearer signal within the confines of buildings, where physical barriers can attenuate radio waves. In contrast, VHF signals have longer wavelengths, which may have increased difficulty traveling through these same materials. VHF signals tend to reflect off surfaces rather than pass through them, leading to weaker reception inside structures. This makes UHF a more favorable choice for indoor communications, such as in urban settings or within complexes, where considerable obstructions can impede signal strength. Understanding this characteristic of signal propagation highlights the practical reasons why UHF frequencies are often chosen for various communication systems that operate in environments with numerous physical barriers.