The difference in wavelength sizes between television frequencies result in varying broadcast performance. There are two major over-the-air television frequencies in the United States: UHF and VHF. Ultra High Frequency, or UHF, broadcasts have a shorter wavelength, which makes them easier for antennas to receive. In addition, these broadcasts can pass through smaller-sized openings compared to VHF signals.
Due to the difference in wavelength for UHF and VHF signals, VHF broadcasts need a larger antenna for smooth reception. However, VHF signals are easier to receive through obstacles such as trees or large poles. VHF diffracts around these obstacles and comes in at 40 percent signal, while UHF can only manage 10 percent signal in the same conditions.
Most digital television stations in the United States now use UHF, but there are still a number of VHF channels. Since digital TV produces a picture that is either perfect or blank, it is important to buy the right antenna to receive all available channels.
Channel two in North America has a wavelength of around 5.5 meters, while the lowest UHF channel has a 64-centimeter wavelength. Powerful VHF antennas are often as long as 3 meters, while a comparable UHF antenna is 1 meter. Modern roof antennas have a smaller Yagi placed in front of a larger log-periodic, providing both UHF and VHF-high signals.