On the face of it, a simple AM/FM radio is easy enough to use. You power it through an electric plug or batteries, and you turn it on. You then pick AM stations if you want news or talk radio, or go with the FM band for music after raising the FM antenna. You turn the tuner dial to pick the specific station you want, adjust the volume, sit back, and relax.
But how, exactly, does this thing work. How does the music travel from the radio station to your radio? On a similar note, how do people talk through 2-way radio without wires?
From a medieval person’s point of view, it works like magic. But then again, “any sufficiently advanced technology is indistinguishable from magic,” as legendary sci-fi author Arthur C. Clarke famously put it.
But it’s not magic, though it may seem that way for some of us.
A more complete explanation may require an entire book, but here’s the gist of the process. A little more than a hundred years ago, geniuses figured out how to use electric currents to generate radio waves, and that it’s actually possible to use these waves for wireless communication.
For this type of communication, the 2 basic components are the transmitters and the receivers.
How Radio Transmitters Work
The transmitter may be used by your favorite radio station, but you also have one in your 2-way radio.
- A radio transmitter has an oscillator that generates a carrier wave at a particular frequency.
- Then there’s the modulator, and its job is to add the useful info to that carrier wave. This can be the music or the news, for example.
- The modulator can slightly increase or decrease the carrier wave intensity. This is amplitude modulation, which you find in AM radio broadcasts.
- Or, the modulator can slightly increase or decrease the carrier wave frequency. This is frequency modulation, which you find with FM radio.
- There’s an amplifier that then increases the power of the modulated carrier wave. This is crucial so that you can send out a powerful broadcast that can reach for many miles around.
- Finally, there’s the antenna. This converts the amplified signal to the radio waves sent out to your AM/FM radio, and to the other radios in the area.
How Your Radio Receiver Works
The job of your AM/FM radio is to receive the information sent out by these stations through radio waves. That way, you’re able to enjoy your punk music, hourly news, baseball game broadcasts, and storm warnings.
So how does this radio really work? It’s like with the radio transmitters, but with everything in reverse to obtain the useful information.
- Receiving the info starts with your antenna. For AM radio, there’s usually a small, hidden antenna inside the radio. For FM radio, you often have to extend the FM antenna. You may even have to fiddle with it and point it the right way to get the best radio reception without too much static.
With the antenna exposed to the radio waves in the air, these radio waves induce a tiny alternating current in the antenna.
- The receiver has an RF amplifier, which boosts (amplifies) the extremely weak radio frequency signal from the antenna. This readies the signal for processing by the tuner.
- The antenna may just be a piece of wire, though for most metals it’s an elongating metal tube. Yet it receives the radio waves of all the frequencies, and then the RF amplifier amplifies all these signals. That means you can, theoretically, listen to all the radio stations at the same time. Obviously, that’s not practical.
That’s where the tuner comes in. The tuner extracts the signals from a specific frequency from all these frequencies your antenna receives.
The tuner is a circuit that uses and inductor and a capacitor so that the circuit resonates at a specific frequency. Depending on the values you choose for the coil and capacitor, you’ll have your resonant frequency. This circuit blocks out all the other alternating current signals that aren’t the same as the resonant frequency.
So, your tuner is not just a simple dial to select the radio station you want. It’s actually a lot more sophisticated than just a “simple dial”.
- Now that you have received the radio wave, how do you obtain the useful info inside it? For that, you have the detector. This detector then separates the audio information, so the music or the news is now distinct from the carrier wave.
- In its raw form, the signal you get from the detector is actually very weak. To hear the info, you have an audio amplifier. This boosts the weak signal significantly, often just by using a very basic transistor amplifier circuit. This is also why this type of radio is sometimes called the transistor radio.
- The detector then sends out the audio through the speakers, and you’re good to go. Obviously, you can bypass the speaker and just listen to earphones or headphones.
We’ve just described the basic radio receiver setup. Most radios offer more sophisticated features, with extra filtering and tuning circuits for better performance. These circuits may enable the radio to lock on much better to the frequency of your favorite radio station while excluding other signals for better reception. Or perhaps it’s designed to produce superior audio output, so that you hear crystal-clear music you can really enjoy.
Keep in mind that with 2-way radios, you have simple transmitter and receiver capabilities. The 2-way radio acts like a broadcast station, and another person receives your signal through your chosen frequency. Then they can respond, and you can hear what they have to say through your own radio.
As you can see, it’s not really magic. But then in some ways, it’s still magic despite the seeming simplicity of the designs. You can hear music broadcast from many miles away—regardless of how you explain this, it’ll always be great!