Which frequency characteristic tends to require more tower sites for coverage?

Higher frequency signals tend to require more tower sites for effective coverage primarily due to their propagation characteristics. As frequency increases, the wavelength decreases, which results in reduced ability to penetrate obstacles such as buildings, trees, and varied terrain.

Higher frequency signals are more directional and experience greater attenuation when traveling through or around physical barriers, meaning they can't travel as far as lower frequency signals without losing significant strength. Consequently, to maintain consistent coverage in a given area, more transmitters or tower sites are necessary to compensate for the limited range of these higher frequency waves.

In contrast, lower frequency signals, with their longer wavelengths, can propagate over longer distances and can diffract around obstacles more effectively, making them suitable for broader coverage with fewer tower installations. Mid-range and ultra-high frequencies also share similar characteristics, but the specific context highlights that it is the higher frequencies that lead to the need for a denser arrangement of towers.