telecommunications Telecommunication, often used in its plural form or abbreviated as telecom, is the transmission of information over a distance using electronic means, typically through cables, radio waves, or other communication technologies. These means of ...

, antenna blind cone (sometimes called a cone of silence or antenna blind spot) is the volume of space, usually approximately conical with its vertex at the antenna, that cannot be scanned by an antenna because of limitations of the antenna

radiation pattern In the field of antenna design the term radiation pattern (or antenna pattern or far-field pattern) refers to the ''directional'' (angular) dependence of the strength of the radio waves from the antenna or other source.Constantine A. Balanis: " ...

and mount. The concept was encountered as early as the 1950s in low-frequency radio ranges, when it was used to determine when an aircraft was directly over a station. As the signal may not completely fade away, the aircraft's position could be confirmed by listening for a station location, or "Z", marker. An

Air Route Surveillance Radar The Air Route Surveillance Radar is a long-range radar system. It is used by the United States Air Force and the Federal Aviation Administration to control airspace within and around the borders of the United States. The ARSR-4 is the FAA's mos ...

(ARSR) is an example of an antenna blind cone. The horizontal radiation pattern of an ARSR antenna is very narrow, and the vertical radiation pattern is fan-shaped, reaching approximately 70° of elevation above the horizontal plane. As the fan antenna is rotated about a vertical axis, it can illuminate targets only if they are 70° or less from the horizontal plane. Above that elevation, they are in the antenna blind cone. The antenna blind cone is also referred to as the "cone of silence", especially in America. This term is also used for

weather radar A weather radar, also called weather surveillance radar (WSR) and Doppler weather radar, is a type of radar used to locate precipitation (meteorology), precipitation, calculate its motion, and estimate its type (rain, snow, hail etc.). Modern w ...

NEXRAD NEXRAD or Nexrad (Next-Generation Radar) is a network of 159 high-resolution S-band pulse-Doppler radar, Doppler weather radars operated by the National Weather Service (NWS), an agency of the National Oceanic and Atmospheric Administration (NOAA) ...

radars make two-dimensional scans at varying angles ranging from 0.5° above level to 19.5° above level (during a significant weather event). These levels become much closer to the ground, and closer to each other, as they get closer to the radar site, rendering them of little use for the three-dimensional profiling such multi-level scanning is meant to provide. Thus, a weather event located very close to and/or directly overhead of the radar site will be mostly situated in the "cone of silence." This is part of the reason why most U.S. weather radars partially overlap each other's territories.

References

Blind cone Blind often refers to: * The state of blindness, being unable to see * A window blind, a covering for a window Blind may also refer to: Arts, entertainment, and media Films * ''Blind'' (1987 film), a documentary by Frederick Wiseman about the ...

Radar {{electronics-stub