ABSTRACT
Radiation patterns for frequency modulated antenna systems can be considered in two distinct categories. Antenna systems, which will be categorized as a non-directional antenna (NDA) or a directional antenna, and in all cases the term "omnidirectional" refers to the azimuthal response of an NDA, whether it is horizontally or vertically polarized. Antenna performance testing is a complex and fairly lengthy process that begins with an assessment of the radiation patterns achievable with a given physical configuration of panels or elements. Compared to the measurements of Voltage standing wave ratios conducted at the factory, site measurements differ because they generally include tens to hundreds of feet of coaxial line—assuming measurements are being made in the transmitter building and not at the antenna. The elevation plane response, or Vertical Radiation Patterns for a pure omnidirectional antenna, determines the effective gain of the antenna system and is directly proportional to the size, or aperture, of the antenna.
