I don’t really understand what it means when radios “tap into” certain frequencies and how they are transmitted.
In: Physics
Radio waves are, well, waves. An alternating thing going one way then the other. This thing is is an electric field – it creates a force on electrons in the antenna and the result is an electrical signal.
Now, this wave and the signal it creates (which is more or less a copy of the original wave, so the electric signal is also a wave) has a certain frequency. This frequency is the number of times the wave goes back in forth in one second.
Even if multiple frequencies are picked up at the same time, you can use a simple device to ignore all but the one you want, like your ears picking out a specific sound in a song. This device, this filter, allows many radios to transmit in the same place but not get mixed up. By adjusting the filter you can choose which frequency to allow through so you aren’t hearing all of them.
If you’ve ever tuned guitar strings to one another, you’ve seen that when the tuning is perfect, playing a note on one string will make the other string tuned to the same note vibrate as well. Tuning a radio does the same thing, only with electricity vibrating inside a circuit. Even if there’s a cacophony of radio waves coming in, the “string” will only respond to a single tone in all that noise.
Radio waves are electromagnetic waves carried by photons, exactly like heat or visible light, but at a much longer wavelength / lower frequency. When those photons move past an antenna, they induce a tiny voltage through it, very loosely similar to how moving a magnet through a coil of wire will generate a voltage.
The problem is, your antenna is equally sensitive to a pretty wide range of frequencies (maybe everything from 88-108 MHz for radio), but the user doesn’t want to listen to 50 radio stations all at once. You need some tool to focus on a specific frequency and ignore all the others. This is called a “bandpass filter,” because a narrow band of frequencies “passes through,” and all other frequencies get thrown away. Tuning your radio means telling that bandpass filter which frequencies it should be paying attention to.
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