What Causes Antennas to Radiate?

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Discussion Overview

The discussion centers on the mechanisms that cause antennas to radiate electromagnetic fields, exploring the principles of electromagnetic theory and the behavior of electrons within antennas. Participants examine the relationship between alternating currents, electron movement, and the generation of radio waves, touching on concepts from Maxwell's equations and induction principles.

Discussion Character

  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • Some participants propose that passing radio-frequency alternating currents through an antenna causes electrons to jostle, which in turn creates electromagnetic fields that manifest as radio waves.
  • Others argue that currents induced in the antenna produce an electromagnetic field, referencing Maxwell's equations as foundational to this understanding.
  • A participant questions the role of induction principles, suggesting that electric fields typically produce only magnetic fields without generating radio waves.
  • In response, some participants clarify that changing electric fields create magnetic fields and vice versa, implying that electron motion inherently produces radiation.
  • One participant elaborates that electron motion against fixed ions in the conductor's lattice causes vibrations that produce electric fields, while another asserts that electron motion alone is sufficient for radiation, dismissing the necessity of ionic motion.

Areas of Agreement / Disagreement

Participants express differing views on the conditions under which antennas radiate fields, with no consensus reached on the necessity of ionic motion or the specific mechanisms involved in radiation generation.

Contextual Notes

Some statements rely on assumptions about electromagnetic theory and the behavior of materials, which may not be universally agreed upon. The discussion also reflects varying interpretations of induction principles and their implications for radiation.

shankar
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what makes antenna to radiate,the basic principle...

:smile:
 
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You pass radio-frequency alternating currents through the antenna. The electrons in the antenna get jostled back and forth. Jostling electrons create jostling electromagnetic fields. Jostling electromagnetic fields are what we call "radio waves."

- Warren
 
Currents induced in the antenna by the transimtter, produce a Electro magnetic field. This is all coverd by Maxwells equations. Due a web search on that key word for more information.
 
the alternating current produce fiels...then what about the induction principle...where electric field produce only magnetic field no radio waves?
[?]
 
Originally posted by shankar
the alternating current produce fiels...then what about the induction principle...where electric field produce only magnetic field no radio waves?
[?]
Changing electric fields create magnetic fields. Changing magnetic fields create electric fields. You cannot jostle an electron around without producing SOME radiation.

- Warren
 
Originally posted by chroot
You pass radio-frequency alternating currents through the antenna. The electrons in the antenna get jostled back and forth. Jostling electrons create jostling electromagnetic fields. Jostling electromagnetic fields are what we call "radio waves."

- Warren
To elaborate , electrons jostle against ions which are held in a fixed position in the crystal lattice of the conductor , causing the ions to vibrate and produce electric fields.
 
ya its true E&M are there but at what condition they the element radiates field?
 
Originally posted by shankar
ya its true E&M are there but at what condition they the element radiates field?
What?

- Warren
 
Originally posted by McQueen
To elaborate , electrons jostle against ions which are held in a fixed position in the crystal lattice of the conductor , causing the ions to vibrate and produce electric fields.

Ionic motion is not needed, electron motion alone will do the trick. In fact any ion vibration will probably be in the infra red energy region.
 

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