how radio waves are broadcast out of an antenna.
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Any alternating electric field travelling in any metal generates an electromagnetic field around it. This alternative field propagates as a “wave” at the speed of light.
A single straight piece of wire with a changing current flowing through it works as an antenna, coupling the line to the EM field.
We can even pick up the “hum” of the 60hz power lines in your house with unprotected sensitive devices.
Antenna design is all about efficiently transfering as much power to or from the em field and the transducer a.k.a. antenna, including limiting directionality.
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