Build a Dipole Antenna with LED: Charge Imbalance Explained

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Discussion Overview

The discussion revolves around the construction and operation of a dipole antenna that incorporates an LED and a capacitor, as demonstrated in a video. Participants explore the implications of using an LED in this setup, particularly regarding charge imbalance and the behavior of the LED in response to alternating current from a cellphone transmitter.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions whether the LED's unidirectional current flow would lead to a charge imbalance in the antenna, potentially causing it to stop functioning after a while.
  • Another participant notes that current can flow in the reverse direction once the reverse breakdown voltage is reached, which could damage the LED if excessive current flows.
  • A participant challenges the identification of the component in the video, asserting that it is not an LED.
  • Another participant confirms the use of an LED in the video, referencing a specific timestamp for clarity.
  • Concerns are raised about the labeling of components, with a participant suggesting that the setup described may not logically include a capacitor in parallel with the LED, proposing an alternative configuration where a diode conducts during the other half of the cycle to prevent charge buildup.
  • A participant shares personal experience using a similar setup as an RF detector, indicating it works effectively.

Areas of Agreement / Disagreement

Participants express differing views on the components used in the antenna setup and their implications for charge behavior. There is no consensus on whether the LED will function as expected or if the proposed configurations are valid.

Contextual Notes

Some participants express uncertainty regarding the identification of components and their roles in the circuit, highlighting potential misunderstandings due to language barriers in the video.

Who May Find This Useful

Individuals interested in antenna design, RF detection, and the behavior of electronic components in alternating current applications may find this discussion relevant.

greypilgrim
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Hi.

In this video around 6:45, this guy builds a simple dipole antenna with an LED and capacitor in parallel in the center. The LED flickers when close to a transmitting cellphone.

Since the LED only let's current pass in one direction, shouldn't this quickly lead to a charge imbalance between the parts of the antenna and thus create an opposing field so the LED should stop working after a while?
 
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greypilgrim said:
Since the LED only let's current pass in one direction, shouldn't this quickly lead to a charge imbalance between the parts of the antenna and thus create an opposing field so the LED should stop working after a while?
Current will also flow in the reverse direction once the reverse breakdown voltage is reached. Usually about 6V. The LED will be destroyed by reverse current if too much current flows.
 
This is not a LED.

upload_2017-3-17_7-5-20.png
 
Yes, but he only uses this lamp in the first experiment. In the second part of the video he clearly uses an LED. The label can be seen at 7:08.
 
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greypilgrim said:
Yes, but he only uses this lamp in the first experiment. In the second part of the video he clearly uses an LED. The label can be seen at 7:08.

yes agreed
I have issues with that it is supposed to be a capacitor in parallel with the LED, ceramic Capacitors DONT have black band on one end of them
BUT there are plenty of diodes that are blue bodied and have black bands on one end ... a capacitor in there just doesn't make sense

it's a pity that the video isn't in English so that the narration could be understood !

This would be a more logical setup
the LED conducts 1/2 the cycle, the diode conducts the other 1/2 cycle so there is no build-up of charge at one end

and that situation I have often used as a RF detector ... works very well

upload_2017-3-18_11-3-18.png


cheers
Dave
 
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