File:Log-periodic monopole antenna.png
Summary
A wire <a href="https://en.wikipedia.org/wiki/log-periodic_antenna" class="extiw" title="w:log-periodic antenna">log-periodic monopole antenna</a> for military communication, from a US Navy training manual. It consists of many vertical wire monopole <a href="https://en.wikipedia.org/wiki/driven_element" class="extiw" title="w:driven element">driven elements</a> of gradually decreasing length suspended through insulators from a support line between two masts, attached in parallel to a feedline at the bottom. The log-periodic antenna, invented by Dwight E. Isbell and Raymond DuHamel in 1958, is a broadband high-gain antenna. Log-periodic dipole antennas (LPDAs) are widely used as rooftop <a href="https://en.wikipedia.org/wiki/television_antenna" class="extiw" title="w:television antenna">television antennas</a>, but vertical monopole versions like this can also be used in the MF and HF band. Each vertical element serves as a quarter-wave <a href="https://en.wikipedia.org/wiki/monopole_antenna" class="extiw" title="w:monopole antenna">monopole</a> radiator, one half of a <a href="https://en.wikipedia.org/wiki/dipole_antenna" class="extiw" title="w:dipole antenna">dipole antenna</a>. The other side of the feedline to the transmitter or receiver is attached to a buried ground system under the antenna, and the reflection of the element in the ground plane provides the other half of the dipole. The antenna radiates <a href="https://en.wikipedia.org/wiki/vertical_polarization" class="extiw" title="w:vertical polarization">vertically polarized</a> radio waves in a beam off the narrow end of the antenna. The antenna has a fairly constant gain between the wavelengths equal to 4 times the longest element and 4 times the shortest element. A typical version designed to cover a frequency range of 2-30 MHz requires a 140 ft tower and the antenna is 500 ft long. The US Navy AS-2224/FRC is a typical portable version.
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File history
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| Date/Time | Thumbnail | Dimensions | User | Comment | |
|---|---|---|---|---|---|
| current | 23:15, 7 January 2017 | | 302 × 224 (5 KB) | 127.0.0.1 (talk) | A wire <a href="https://en.wikipedia.org/wiki/log-periodic_antenna" class="extiw" title="w:log-periodic antenna">log-periodic monopole antenna</a> for military communication, from a US Navy training manual. It consists of many vertical wire monopole <a href="https://en.wikipedia.org/wiki/driven_element" class="extiw" title="w:driven element">driven elements</a> of gradually decreasing length suspended through insulators from a support line between two masts, attached in parallel to a feedline at the bottom. The log-periodic antenna, invented by Dwight E. Isbell and Raymond DuHamel in 1958, is a broadband high-gain antenna. Log-periodic dipole antennas (LPDAs) are widely used as rooftop <a href="https://en.wikipedia.org/wiki/television_antenna" class="extiw" title="w:television antenna">television antennas</a>, but vertical monopole versions like this can also be used in the MF and HF band. Each vertical element serves as a quarter-wave <a href="https://en.wikipedia.org/wiki/monopole_antenna" class="extiw" title="w:monopole antenna">monopole</a> radiator, one half of a <a href="https://en.wikipedia.org/wiki/dipole_antenna" class="extiw" title="w:dipole antenna">dipole antenna</a>. The other side of the feedline to the transmitter or receiver is attached to a buried ground system under the antenna, and the reflection of the element in the ground plane provides the other half of the dipole. The antenna radiates <a href="https://en.wikipedia.org/wiki/vertical_polarization" class="extiw" title="w:vertical polarization">vertically polarized</a> radio waves in a beam off the narrow end of the antenna. The antenna has a fairly constant gain between the wavelengths equal to 4 times the longest element and 4 times the shortest element. A typical version designed to cover a frequency range of 2-30 MHz requires a 140 ft tower and the antenna is 500 ft long. The US Navy AS-2224/FRC is a typical portable version. |
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