Electromagnetic signals questions

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Discussion Overview

The discussion centers on the characteristics of electromagnetic signals, specifically the relationship between the electric and magnetic components, and the functionality of receivers in detecting these signals. Participants explore theoretical aspects, practical applications, and the efficiency of different types of antennas.

Discussion Character

  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions how much larger the electric component of an electromagnetic signal is compared to the magnetic component, suggesting that receivers primarily focus on the electric signal.
  • Another participant argues that receivers do not selectively look for one part of the signal, stating that both electric and magnetic components are essential for the antenna to function.
  • A participant references their book, which claims that the electric component is significantly larger than the magnetic component, using the relationship E=c*B to support this view.
  • Further, a participant expresses concern about the efficiency of loop antennas compared to dipole antennas, questioning the practicality of their AM broadcast radio receiver if the electric component is indeed much larger.
  • Another participant clarifies that antennas couple to electromagnetic waves where both fields are present, and distinguishes between antenna operation based on electromagnetic waves and near-field coupling methods.

Areas of Agreement / Disagreement

Participants express differing views on the significance of the electric versus magnetic components in electromagnetic signals and their implications for receiver design. The discussion remains unresolved with multiple competing perspectives on the topic.

Contextual Notes

Participants reference specific relationships and equations, such as E=c*B, but do not fully resolve the implications of these relationships on antenna efficiency or receiver functionality. There is also a distinction made between near-field and far-field interactions that is not fully explored.

dervast
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Hi i am wondering in an electromagnetic signal how times bigger the electonic signal is bigger from the magnetic one... I have also read that because the electric signal is bigger the most reveivers ignores the magnetic field and only searchs for the electric signal...


Do u know any receiver that uses the magnetic component of an electromagnetic signal?
Really how can we denote an electromagnetic signal?
 
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You aren't even close. The receiver doesn't 'look' for a certain part of the signal as you imply. The antenna creates an electric current which is the same as any other electric current. Of course the signal strength is very low. The receivers job is to filter out the frequency wanted and amplify it and convert it to audio which we can hear. The antenna will not work if either part of the electromagnetic signal is missing. In fact, you can't really have one without the other.
 
Thx a lot but my book mentions that receivers use the electri part of the signal and not the magnetic one because the electric one is c times bigger E=c*B
 
dervast said:
Thx a lot but my book mentions that receivers use the electri part of the signal and not the magnetic one because the electric one is c times bigger E=c*B
But then a loop antenna would be 3*10^8 times less efficient than a dipole, and my simple AM broadcast radio receiver wouldn't work very well...

As supernova says, antennas couple to EM waves, where both the electric and magnetic fields are present in a traveling or stationary electromagnetic wave. If you want to talk about near-field capacitive or inductive pickups, then yes, you don't need an EM wave. But antenna equations are based on Maxwell's equations for electromagnetic waves, not for near-field coupling of one or the other field.
 

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