How are radio stations able to turn digital music into radio waves?


How are radio stations able to turn digital music into radio waves?

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It all depends on what you mean by ‘digital’ music and what type of radio wave.

If you’re referring specifically to FM radio in the FM broadcast frequency bands for consumer or commercial radio stations.

Different parts of the world use different frequency band licensed slot assignments. Where I’m from this generally uses a frequency between 88Mhz-109Mhz for broadcast.

The source (music/audio) can be split into various sub segments and either used in an analogue or digital amplifier. The only real difference between the two is analogue and digital use different modulation techniques.

FM being (Frequency Modulation) will maintain a constant frequency (carrier signal) and the audio is added or subtracted to the carrier frequency.
This is called the modulation technique.

There are many forms of modulation techniques dependent upon the source, the receivers, distance e.g AM, FM, PCM, TDM, 2-4-8-16 QAM.

Ultimately the selected frequency band of operation, RF power requirements, type of audio or data to be transmitted will determine the most suitable modulation technique to employ for any given use requirement.

When you talk Wi-Fi, Microwave, Satellite communications they all follow the same base principles just the operating band and modulation scheme change to suit the particular environment.

Input Source>Modulation Indexing>Power Amplifier>Transmission Line/Antenna.
At other end is your Receiver which de-modulates the source/signal via the same modulation scheme and I.F mixing to feed the subsequent demodulated signal to an audio amplifier and ultimately a speaker which is just converting an electrical signal back into a mechanical signal> speaker coil moves and the resultant cone sound back in our hearing range 0.3kHz ~ 20kHz.

It’s not just RF energy, things like fibre optic use various wavelengths of light to perform the modulation and demodulation.

There are literally hundreds types transmission lines, modulation techniques, splitters, amplifiers that work from DC>Light and everything in-between.

The use case scenario ultimately determines the frequency band, modulation technique to be used for that particular use case.

The radio waves stations send have two parts: the sound waves, which are self explanatory, and the carrier wave, which is like an identifer for each station. In fact, these carrier waves are where station numbers come from (like 1080 or 100.5).

The station will broadcast signals that combine the sound and carrier waves together. When you tune your radio, you’re asking it to look for a signal with a specific carrier wave. As the radio picks up those signals, it removes the carrier wave and keeps the sound waves, which it then plays as music.

Digital music is basically a long list of air pressures. Quite literally when it comes to CDs, and an mp3 is a list of instructions to calculate the air pressures. There are 40.000 measurements a second to be exact. Each radio station has an assigned frequency. When the air pressure is high it sends a slightly higher frequency, when it is low it is a slightly lower frequency. Messing with the frequency is called modulation. A normal radio wave has about a hundred million positive peaks per second. Your radio can just count the number of peaks in a 40.000th of a second. It knows that on average the speaker should be in a neutral position. If it counts a few more it pushes the speaker outwards, a few less and it pushes the speaker inwards.

Counting isn’t quite how the radios work but it’s a good enough analogy.

All sound is analog.

While reproductions of particular sounds may be recorded and stored in digital mediums, when these are played back, the result is *analog* electrical signals which drive the speakers. Even when a speaker is fed directly with digital pulses, the resultant sound is an analog signal.

FM radio stations merely replace speakers with an FM radio transmitter.

Radio transmission is fascinating!

>FM radio was invented by Edwin Armstrong in order to make high-fidelity (and static-free) music broadcasting possible. He built the first station in 1939, but FM did not become really popular until the 1960s. Hence the higher frequencies for FM radio.