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Radio signals come to antennas from certain directions. How does the antenna process of receiving the signal in the air work? How does a certain antenna receive this electromagnetic field as the radio signal travels through the air? Why does that antenna receive it and not another conductor? Also, doesn't an electromagnetic signal get lost when it is received by other antennas before it reaches the target antenna?

Specifically, I ask the following. How is the signal from an antenna directed towards the target? How is the signal coming to the target antenna pulled towards itself by the antenna?

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    $\begingroup$ This question is similar to: How can current flow through an open wire (like a dipole antenna)?. If you believe it’s different, please edit the question, make it clear how it’s different and/or how the answers on that question are not helpful for your problem. $\endgroup$
    – Farcher
    Commented Nov 16 at 23:19
  • $\begingroup$ Possibly relevant: physics.stackexchange.com/q/35412/4993 $\endgroup$
    – WillO
    Commented Nov 17 at 13:31
  • $\begingroup$ This could be helpful in aiding your understanding, although not directly related: youtu.be/GVYEVhZ-BaE $\endgroup$
    – Tachyon
    Commented Nov 17 at 14:02
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    – uhoh
    Commented Nov 17 at 14:11
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    $\begingroup$ I think this question shouldn't have been closed. Some of the answers here are even better than the other question, and contain more information! $\endgroup$
    – Mike Waters
    Commented Nov 17 at 18:23

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How do antennas catch the correct radio signal in the air?

They don't. They catch all the signals that are within their operating band (which is generally much wider than a single broadcasting channel).

Then the receiver electronics that they are connected to selects an individual channel to receive, amplify, and demodulate or decode.

How does a certain antenna receive this electromagnetic field as the radio signal travels through the air?

It depends on the geometry of the antenna. An antenna made up of a long straight wire works by the electric field component of the EM wave driving conductors in the antenna back and forth. An antenna made up of a loop of wire works by the magnetic field component of the EM wave inducing an emf around the loop. Other shapes are more complicated but typically work by reflecting the EM field from a large area onto a smaller antenna that works like one of the above.

Why does that antenna receive it and not another conductor?

Other conductors can. That's why electrical engineers spend a lot of time worrying about electromagnetic compatibility and electromagnetic compliance.

Also, doesn't an electromagnetic signal get lost when it is received by other antennas before it reaches the target antenna?

Typically antennas aren't that efficient at extracting power from the EM wave. Also, even if they did completely absorb the power that reached them, the wave would refract around them after a few wavelengths and be available for a second antenna to receive.

How is the signal from an antenna directed towards the target?

This is a very complicated question, but it basically involves designing the transmitting antenna so that radiation from it interferes constructively in the direction you want to send a signal and destructively in the directions you don't want to send the signal.

How is the signal coming to the target antenna pulled towards itself by the antenna?

It isn't. The receiving antenna just receives the (usually tiny) portion of the transmitted signal that happens to reach its actual surface.

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  • $\begingroup$ What drives a radio signal to reach the surface? Why does it reach the surface specifically where the target is? $\endgroup$
    – Ahmet
    Commented Nov 16 at 17:58
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    $\begingroup$ The signal doesn't go specifically to where the receiver is. The broadcast signal goes to a wide area, and if people want to receive it they can put their receiver antennas anywhere that the signal is going. $\endgroup$
    – The Photon
    Commented Nov 16 at 18:03
  • $\begingroup$ But signal is transmitted through the air How can it be received by an antenna on the ground? How exactly does the process of receiving this signal through the air work? @The Photon $\endgroup$
    – Ahmet
    Commented Nov 16 at 18:07
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    $\begingroup$ @Ahmet, typically you extend your antenna above the ground into the air. Burying it in the ground is usually ineffective. (but also google the image effect which allows the ground to be used as a reflector that doubles the effective length of an antenna) $\endgroup$
    – The Photon
    Commented Nov 16 at 18:12
  • $\begingroup$ @Ahmet I suggest reading an amateur radio handbook for some practical information on antenna design and operation. You may be able to find an older edition (even one from the 1960's would help you) online for free, or if you're in the US find one at your local public library. $\endgroup$
    – The Photon
    Commented Nov 16 at 18:15
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The broadcast signal is not directed in most cases. It goes in all directions. That is why millions of people can listen to the same radio station.

Broadcasts are made on narrow frequency bands, and it is the job of the receiver to be tuned to a certain frequency and filter the desired signal from the general cacophony of radio signals that exists in the ambient environment.

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  • $\begingroup$ Although this is technically correct, most of the broadcast patterns you cited do transmit in all directions – but some more strongly than others. My main goal was to correct the OP's mistaken idea of a point to point transmission. And I can adjust the wording to cover the intent which was the entire receiving apparatus $\endgroup$
    – RC_23
    Commented Nov 16 at 21:18
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To add to The Photon's answer:

A clever antenna design can actually behave significantly "larger" than its physical cross-section for signal capture, as follows. We can place a "dummy antenna" that is not connected to anything a short distance in front of the actual antenna. The incoming radio wave strikes the dummy element first and wastes some time interacting with it. That portion of the plane wave front is now slightly phase-delayed relative to the rest of the wave and the wave then refracts (bends in) slightly around the dummy element- so more of the plane wave strikes the "active" antenna behind it.

We can add more dummy elements like this in front of the active element to diffract more and more of the incoming plane wave into the active element, yielding an antenna that now consists of a long horizontal beam (bristling with little antenna elements sticking out from its sides) that you point at the broadcasting antenna. This is the principle behind old-school rooftop TV antennas from the pre-cable era and is called the Yagi-Uda design after its Japanese inventors.

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