What are the common very high frequency/ultra-high frequency (VHF/UHF) [30 MHz to 300 MHz, and 300 MHz to 1000 MHz] antenna types?

VHF/UHF stands for very high frequency and ultra-high frequency, respectively. These frequency designations are in both the ITU and IEEE radar bands, but in this case we are discussing IEEE radar bands VHF and UHF, 30 MHz to 300 MHz and 300 MHz to 1000 MHz in the US. This is an important note, as the ITU UHF band extends to 3000 MHz. The VHF/UHF bands are commonly used for land mobile radio (LMR), public safety, military communications, trunking, AM/FM radio, GPR/WPR, TV broadcast, aviation, LMR/PMR, and amateur radio applications. Given the requirements of many of the applications in these frequency bands, VHF/UHF antennas are often designed to be extremely environmentally rugged, serve flexible deployments, and to handle relatively high power levels.

The most common VHF/UHF antenna types are dipole arrays, exposed dipoles, collinear, and Yagi antennas. The following is a brief description of the common VHF/UHF antenna types.

Dipole Array Antenna

A dipole array antenna consists of two or more dipole antennas positioned on the antenna structure in such a way to achieve a desired radiation pattern. Properly designed, a dipole array antenna can be more directional and exhibit more desirable gain characteristics over a given frequency bandwidth than a standard dipole.

Exposed Dipole Antenna

An exposed dipole is simply a type of dipole antenna with the electrical structure “exposed” instead of concealed beyond or within additional radome or protective housing. Like a typical dipole, an exposed dipole is omnidirectional and operates over a distinct bandwidth that is a direct result of the dimensions of the dipole antenna.

Collinear Antennas

Collinear antennas, or collinear antenna arrays, are array antennas where the antenna elements are precisely spaced to be both parallel and collinear. In this way collinear antenna elements are all positioned along a single axis. For VHF/UHF applications, collinear antennas are typical dipoles stacked along the vertical axis. This is done as a dipole radiates equally out in all azimuthal directions perpendicular to the antenna and only marginally at the top and bottom of the antenna axis. By “stacking” dipole antennas, the relative signal strength of the radiation pattern can be increased, as there is a practical limit to the size of a dipole antenna for a given bandwidth.

Yagi Antennas

A Yagi antenna, or Yagi-Uda antenna, is a series of parallel resonant antennas constructed in an end-fire array. Usually, Yagi antennas are constructed using half-wave dipoles. The benefit of a Yagi antenna is that it is a highly directional antenna with moderate to high gain.