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The rubber ducky antenna (or rubber duck aerial) is an electrically short monopole antenna, invented by Richard B. Johnson, that functions somewhat like a base-loaded whip antenna. It consists of a springy wire in the shape of a narrow helix , sealed in a rubber or plastic jacket to protect the antenna. [ 1 ]
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A reconfigurable antenna is an antenna capable of modifying its frequency and radiation properties dynamically, in a controlled and reversible manner. [2] In order to provide a dynamic response, reconfigurable antennas integrate an inner mechanism (such as RF switches, varactors, mechanical actuators or tunable materials) that enable the intentional redistribution of the RF currents over the ...
Paradoxically, every antenna of any type, shorter than ~ 1 / 10 wave in its longest dimension is approximately isotropic, but no real antenna can ever be exactly isotropic. An antenna that is exactly isotropic is only a mathematical model , used as the base of comparison to calculate either the directivity or gain of real antennas.
The most commonly used shortwave antennas for international broadcasting are the HRS antenna (curtain array), which cover a 2 to 1 frequency range and the log-periodic antenna which cover up to 8 to 1 frequency range. Within that range, the SWR will vary, but is usually kept below 1.7 to 1 – within the range of SWR that can be tuned by ...
The Glasgow Academy: 73.6 66.2 9 Stewart's Melville College: 73.3 68.9 10 The Mary Erskine School: 73.1 75.2 11 High School of Dundee: 72.6 73.3 12 St Margaret's School for Girls, Aberdeen 71.7 62.8 13 St. Aloysius' College: 71.2 65.5 14 George Watson's College: 70.9 68.1 15 Morrison's Academy: 68.6 66.5 16 Wellington School: 68.6 61.1 17 ...
For instance, if a radio wave passing a given location has a flux of 1 pW / m 2 (10 −12 Watts per square meter) and an antenna has an effective area of 12 m 2, then the antenna would deliver 12 pW of RF power to the receiver (30 microvolts RMS at 75 ohms). Since the receiving antenna is not equally sensitive to signals received from all ...
The length of a whip antenna is determined by the wavelength of the radio waves it is used with. Their length varies from compact electrically short antennas 1 / 10 wavelength long, up to 5 / 8 wavelength to improve directivity. The most common type is the quarter-wave whip, which is approximately 1 / 4 wavelength long.