VHF
Initialism of very high frequency.
VHF: radio waves between 30 and 300 megahertz
VHF occupies the radio spectrum from 30 to 300 MHz, a range that sits between HF (high frequency) and UHF (ultra high frequency). In industrial and commercial use, VHF bands carry FM radio broadcasts, television signals, aircraft communications, marine radio, and two-way business radio. The wavelength at VHF is roughly 1 to 10 meters, short enough that directional antennas become practical, yet long enough to propagate beyond the line-of-sight with reasonable reliability through atmospheric layers and obstacles.
Within VHF, the band is subdivided by regulatory bodies. The FM broadcast band occupies 88 to 108 MHz. Aviation uses 118 to 137 MHz for air-to-ground voice. Marine VHF spans 156 to 162 MHz and is mandatory on commercial and many recreational vessels. Land mobile radio, including taxi dispatch and industrial two-way systems, operates in several sub-bands between 30 and 50 MHz and between 136 and 174 MHz. Each allocation protects specific uses and prevents interference.
Propagation and practical performance
VHF signals propagate primarily by direct wave and ground wave over distances of 30 to 100 kilometers depending on transmitter power, antenna height, and terrain. Unlike HF, VHF does not reliably bounce off the ionosphere, so it cannot reach around the curvature of the earth. This makes VHF suitable for regional point-to-point links and mobile networks where repeated base stations or relay sites can fill coverage gaps. Rain, fog, and snow cause some attenuation but less than at higher frequencies.
VHF equipment operates with channel widths typically 12.5 kHz or 25 kHz for narrowband applications, allowing more channels in the same spectrum. Modulation is usually FM (frequency modulation) rather than AM because FM offers better noise rejection and more efficient use of the band. Portable and mobile radios for VHF are compact and practical; antennas are short whips or external rods of 30 to 100 centimeters.
The term "very high frequency" is relative; it dates from mid-twentieth-century radio classification when frequencies above 30 MHz were indeed considered very high. Today, VHF remains the workhorse band for reliable short-range industrial, public safety, and commercial communications where simplicity and proven performance outweigh the appeal of newer digital systems.