| It's probably not something many people are interested | | | | The in-phase component is the radiation field of the |
| in unless they're some kind of an electrical engineer or | | | | antenna and the out of phase component is the |
| just bored, but understanding how an antenna works | | | | induction field. At the antenna, both fields are parallel to |
| can be useful when the one on your TV or radio goes | | | | the metal surface. |
| south on you and the reason is beyond your | | | | What happens is that the coulomb field and the |
| comprehension. | | | | induction field fall off much more quickly than the |
| Trying to explain how an antenna works in simple | | | | radiation field as the distance increases from the |
| English is not an easy task as there are a lot of | | | | antenna. When you reach distances greater than a |
| technical specifications that need to be explained. But a | | | | few wavelengths from the antenna, you have what is |
| general understanding is possible without getting into | | | | called the antenna's far field. This field is pure radiation. |
| tech speak that would make Einstein cringe. | | | | As you get closer to the antenna you have what is |
| In order for an antenna to work it has to radiate. Your | | | | called the antenna's near field. This field is a mixture of |
| antenna, whether TV or radio has what is called free | | | | radiation, coulomb, and induction fields. Still with us? |
| electrons running through it. It is these free electrons | | | | Great, we're getting to the good part. |
| that vibrate. The question becomes, how do these | | | | What ultimately happens with all these fields that |
| free electrons vibrate and what causes them to | | | | makes it so that your TV or radio picks up signals |
| vibrate? | | | | through your antenna is this. The free electrons moving |
| Well, in real life it takes an electric field to move an | | | | through your antenna are moving at their maximum |
| electron. If you take an isolated straight dipole, the | | | | speed. The right hand half of your antenna |
| power comes from the combined fields of all the | | | | accumulates electrons. The left hand half of your |
| charged particles, both positive and negative, in the | | | | antenna is where the electrons depart and leave an |
| antenna. We'll call this field the antenna's coulomb field. | | | | excess of charged ions. The coulomb field produces |
| In addition to this field, the antenna exhibits a magnetic | | | | an imbalance and opposes the electrons' rightward |
| field that is the sum of the magnetic fields of all the | | | | motion. The electrons then stop, coast for a bit and |
| free moving electrons. The antenna also has a | | | | then head back towards the left. After they reach |
| dynamic electric field that is the vector sum of the | | | | maximum speed they then stop and process is |
| dynamic electric fields of all the free electrons. What | | | | repeated, now heading back to the right. The result is a |
| we can do is separate the electric field of the antenna | | | | vibration of free electrons that heats the metal and in |
| at any point in space into two components. One of the | | | | turn generates electromagnetic waves. |
| components will be in phase with the total magnetic | | | | And that, in as simple English as possible, is how your |
| field and the other will be 90 degrees out of phase. | | | | antenna works. |