Question about Electromagnetic Wave Induction into Receiving Antennas

[thentangler]

Hey there everybody.

I have a question which till date no professor has been able to answer. At least as far as I know.
Its a basic antenna question.

We all know that any moving charged particle generates EM waves. That is how an antenna works, when the electrons on the antenna are excited at a particular freq, they generate EM waves of that freq. That travels to a receiving antenna and induces oscillations of the electrons in THAT antenna at the same freq. My question is:
How does the receiving antenna convert the oscillations of the electrons to current? There is no transfer of electrons from the transmitting antenna to the receiving one, only EM radiation. And the electrons from the antenna are not fed into the circuits which drive a radio or LEDs which light up when EM waves strike it, like the stickers you stick on your cell phones, and which light up when ever you make or receive a call.

This site might make it clear if I've confused you
http://www.dxzone.com/cgi-bin/dir/jump2.cgi?ID=7566

But it talks only about the transmitting side. My question is on the receiving side.
I really appreciate it if anyone could hlpe me out.
Thanks a lot.

 

[vanesch]

My question is:
How does the receiving antenna convert the oscillations of the electrons to current?

What do you think a current is ?

 

[madmike159]

Antenna gives off radio waves. Radio waves = EM wave = Photon = Energy (E = hf). The energy from the photon is given to a electron in the other antenna creating current.

 

[Meir Achuz]

In a conducting rod antenna, the E field of the EM wave creates an AC EMF in the rod.
In a loop antenna, the B field of the EM wave creates a changing flux through the loop,
giving an EMF by Faraday's law.

 

[thentangler]

Thanks for the replies guys.
@ Clem,
How is the AC EMF fed to the circuitry of the reciever once it passes thru the antenna stage?
Is there a terminal EMF or something which is created at the feedline of the antenna? After that how does it get into the circuit?
I know very well that the current (i.e movement of electrons) which flows into the amplifier modules of your standard radio, does NOT come from the receiving antenna.

Thanks

 

[Meir Achuz]

The antenna just acts like an AC generator in the circuit.

 

[berkeman]

I know very well that the current (i.e movement of electrons) which flows into the amplifier modules of your standard radio, does NOT come from the receiving antenna.

Of course it does. This is an AC current at the RF carrier wave frequency, so the electrons in the antenna and coax cable and input to the receiver amp are all oscillating at the RF carrier wave frequency. The electrons in the metal antenna are experiencing the periodic force from the EM wave going by, and that force is what causes the motion of those electrons, which causes the propagation of the wave (AC motion of the electrons) in the coax cable connected between the antenna and the receive amp input.

 

[thentangler]

Then how is the circuit completed?
Cos the circuit is grounded. And I am pretty much sure there is no depletion of electrons.
the electrons can't be replenished from the air, cos antenna works in space also!

 

[russ_watters]

Then how is the circuit completed?
Cos the circuit is grounded. And I am pretty much sure there is no depletion of electrons.
the electrons can't be replenished from the air, cos antenna works in space also!

It's AC! There is no "depletion of electrons".

 

[thentangler]

I know I am asking a really dumb question. But can you please explain how electrons move in an Alternating Current through a circuit?

 

[russ_watters]

They literally just move back and forth in the wire.