Low Frequency Antennas

Updated on 2017/06/20 03:27

Syllabus

Structural details, dimensions, radiation pattern, specifications, features and applications of following Antennas: 

  • Hertz & Marconi antennas

Hertz Antenna

  • Hertz Antenna is λ/2 antenna & Marconi antenna is λ/4 antenna.
  • Nearly all antennas have been developed from two basic types- the Hertz and the Marconi.
  • The basic Hertz antenna is λ/2 long at the operating frequency and is insulated from ground. It is often called a DIPOLE or a DOUBLET.

hertz-antenna.png

Marconi Antenna

marconni antenna.png

  • The basic Marconi antenna is 1/4 wavelength long and is either grounded at one end or connected to a network of wires called a COUNTERPOISE.
  • The ground or counterpoise provides the equivalent of an additional 1/4 wavelength, which is required for the antenna to resonate.
  • The term "Marconi antenna" usually refers to a two part antenna consisting of a vertical portion and a "reflective" or "ground" portion.
  • When constructed properly, it is very similar to a vertically oriented dipole, in that one element is "up" and the other is "down".
  • Any antenna complete in itself and capable of self oscillation, such as half or full wavelength is known as Hertz antenna.
  • When antenna utilizes ground (earth) as a part of its resonant circuit, it is a Marconi antenna.
  • A quarter wavelength antenna is an example of Marconi antenna where the ground operates as the missing quarter wavelength.
  • Most of the low and medium freq antennas are of Marconi types.

References

  • Notes by Dr. S. K. Jagtap, SKNCOE, Pune
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Created by Vishal E on 2017/05/05 18:39