how are we able to put information on radio waves? I know how radio waves travel, but how do we get info on them like music or news?


how are we able to put information on radio waves? I know how radio waves travel, but how do we get info on them like music or news?

In: Technology

For FM the signal deviates from the carrier frequency with the encoding. So the signal will appear to dance or pulsate.

AM is similar but the signal will vary with amplitude

There are two* ways to get information onto light (which is what radio waves are): change the brightness (amplitude modulation or AM) or change the color/frequency (frequency modulation or FM).

You can’t extract information from the raw carrier wave, but, if you track how the wave changes from baseline, you can extract a signal.

For the simplest of analogue AM radios, you can adjust the intensity of the carrier wave in time with the sound wave. Your radio will move its speaker cone a distance proportional to the strength of the signal; if the signal gets stronger, the cone moves forwards, and if the signal gets weaker, the cone moves backwards. Since the signal strength is moving in time with the sound waves, the speaker cone will move in time with the sound – *producing sound* in the process.

FM radio does the same, but equates the frequency/color of the signal to motion of the cone.

Digital works the same as both, but instead of adjusting the signal based on an analog audio signal, it adjusts it to simulate the bits of data in a computer, which a more advanced radio antenna can decode and feed into a computer on the receiving end.

Imagine the speech from two people talking as information carried by sound waves. If they talked in front of you, you can hear them but the sound can only project so far, so fast.

Now, pit those two people talking on an airplane flying at high speed. This is the radio carrier wave that helps carry information quickly and to far distances. The plane is moving too quickly for you to even comprehend what is said if you are stationary. However, if you manage to synchronize the movement of say a spy drone at exactly the same air speed as the plane, you would be able to follow and hear the conversation.

Tuning your radio frequency is effectively controlling the speed of your spy drone to match the information carried by fast moving radio waves. Using set speeds of aircraft that don’t overlap, you can have multiple conversations (radio stations) all on the air.

Imagine two kids sending each other messages using flashlights to spell out Morse code. By turning the lights on and off, “dot dash dot dash”, they’re sending messages, or “information”.

Radio waves are also light, but they’re not part of what’s called the “visible spectrum”. Imagine the rainbow, and now imagine it keeps going in colors your eyes and brain aren’t set up to see.

In the same way, these radio “lights” blink. An antenna picks up that signal, and translates it into audio — similar to how the bumps and grooves on an old record can “record” sound.

To get a little more advanced, radio and light are both “radiation”. Light is the common name for the radiation “frequency” we can see with our eyes. Radiation can be thought of as a wave. The faster that wave crests and falls, the higher the frequency. Really high frequency radiation, like xrays, can be dangerous. Low frequency radiation, like light and radio, are generally not dangerous.

In the simplest terms, you can “add” waves together. This is what AM does. The music is added to the carrier wave and broadcast over the air. The receiver then subtracts the carrier wave and is left with just the waveform for the music.

[Here’s an illustration]( Consider the top wave the carrier wave, the second wave the music and the third wave the sum of the two. The station broadcasts the third wave. You would then tune your radio to 100Hz and your radio would subtract the 100Hz from the signal it receives.