B Build a Dipole Antenna with LED: Charge Imbalance Explained

[greypilgrim]

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?

 

[Baluncore]

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.

 

[willem2]

This is not a LED.

 

[greypilgrim]

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.

 

[davenn]

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

cheers
Dave