page_title: Adcock antenna
section_title: Radio direction finding
hierarchical_section_title: Adcock antenna / Radio direction finding
caption_attribution_description: English: Diagram showing typical Adcock antenna array GB&#160;patent&#160;130490, Frank Adcock, "Improvements in Means for Determining the Direction of a Distant Source of Electro-magnetic Radiation", granted 1919-08-07 &#160;
context_page_description: The Adcock antenna is an antenna array consisting of four equidistant vertical elements which can be used to transmit or receive directional radio waves.
  The Adcock array was invented and patented by British engineer Frank Adcock in 1919 as British Patent No. 130,490, and has been used for a variety of applications, both civilian and military, ever since. Although originally conceived for receiving low frequency waves, it has also been used for transmitting, and has since been adapted for use at much higher frequencies, up to ultra high frequency.
  In the early 1930s, the Adcock antenna became a key feature of the newly created radio navigation system for aviation. The low frequency radio range network, which consisted of hundreds of Adcock antenna arrays, defined the airways used by aircraft for instrument flying. The LFR remained as the main aerial navigation technology until it was replaced by the VOR system in the 1950s and 1960s.
  The Adcock antenna array has been widely used commercially, and implemented in vertical antenna heights ranging from over 130 feet in the LFR network, to as small as 5 inches in tactical direction finding applications.
context_section_description: Frank Adcock originally used the antenna as a receiving antenna, to find the azimuthal direction a radio signal was coming from in order to find the location of the radio transmitter; a process called radio direction finding.
  Prior to Adcock's invention, engineers had been using loop antennas to achieve directional sensitivity. They discovered that due to atmospheric disturbances and reflections, the detected signals included significant components of electromagnetic interference and distortions: horizontally polarized radiation contaminating the signal of interest and reducing the accuracy of the measurement.
  Adcock—who was serving as an Army officer in the British Expeditionary Force in wartime France at the time he filed his invention—solved this problem by replacing the loop antennas with symmetrically inter-connected pairs of vertical monopole or dipole antennas of equal length. This created the equivalent of square loops, but without their horizontal members, thus eliminating sensitivity to much of the horizontally polarized distortion. The same principles remain valid today, and the Adcock antenna array and its variants are still used for radio direction finding.
caption: Diagram from Adcock's 1919 patent, depicting a four-element monopole antenna array; active antenna segments are marked in red.[1]
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