Difference between revisions of "Antennas"

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== What is an antenna? ==
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Related wiki page: [[Feedlines]]
  
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Antennas are electrical circuits designed to facilitate the transmission and/or reception of electromagnetic radiation.
  
Related wiki page: [[Feedlines]]
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Antennas are specifically designed to transmit/receive as much electromagnetic radiation as possible, whereas most circuits are designed to emit/detect as little as possible.  However, even a [[dummy load]] will emit a small amount of electromagnetic energy when radio-frequency oscillations are applied to it.
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== Antenna Size ==
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Optimized antennas will have dimensions of the same order as the wavelength of operation.  A [[balanced antenna]] will typically be about a half-wavelength long, and an [[unbalanced antenna]] such as a [[vertical antenna|vertical]] will typically be about a quarter-wavelength long.  It is possible to shorten antennas drastically at the cost of efficiency.  See [[antenna loading]] for more discussion.
  
Antennas are electrical circuits. What makes them different from most circuits is that they are designed to facilitate the release of electromagnetic radiation. This occurs because the dimensions of the antenna are significant compared to the wavelength of operation, whereas in a conventional circuit, the dimensions of the components are very small compared to the wavelength of operation. So, antennas are specifically designed to release as much electromagnetic radiation as possible, whereas most circuits are designed to emit as little as possible
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== Theory of Antennas ==
  
In terms of their construction, antennas are LCR circuits in which the Resistance, Inductance and Capacitance are distributed along a conductor, rather than being concentrated in a particular component such as an inductance in an inductor.
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In terms of their construction, antennas are RLC circuits in which [[resistance]], [[inductance]] and [[capacitance]] are distributed along a conductor, rather than being concentrated in a particular component such as an inductance in an inductor.
  
 
== Antenna Types ==
 
== Antenna Types ==

Revision as of 18:07, 20 May 2008

Related wiki page: Feedlines

Antennas are electrical circuits designed to facilitate the transmission and/or reception of electromagnetic radiation.

Antennas are specifically designed to transmit/receive as much electromagnetic radiation as possible, whereas most circuits are designed to emit/detect as little as possible. However, even a dummy load will emit a small amount of electromagnetic energy when radio-frequency oscillations are applied to it.

Antenna Size

Optimized antennas will have dimensions of the same order as the wavelength of operation. A balanced antenna will typically be about a half-wavelength long, and an unbalanced antenna such as a vertical will typically be about a quarter-wavelength long. It is possible to shorten antennas drastically at the cost of efficiency. See antenna loading for more discussion.

Theory of Antennas

In terms of their construction, antennas are RLC circuits in which resistance, inductance and capacitance are distributed along a conductor, rather than being concentrated in a particular component such as an inductance in an inductor.

Antenna Types

Simple Antennas:

Dipole

Loop

Omnidirectional

Random Wire

Vertical

Wire

Complex Antennas:

Beam

DDRR

Dish or Parabola

Log Periodic (LPDA) [1]

Quad

Yagi [2]

Specialized Antennas:

DF - Direction Finding

Mobile

Panel

Portable

Baluns

Understanding Antennas

UNDERSTANDING ANTENNAS FOR THE NON-TECHNICAL HAM