Ok, so I have two questions, but I think the answer for them might be the same.

First, how does a radio station (say FM) transmit data to my car antenna? If the radio station broadcasts at 90.1 MHz, but the sound I want to hear is in the Hz or KHz range, how does this work? It seems like there would have to be two frequencies going on at the same time. Would the data be like a small signal on the larger signal that is the carrier signal?

Similarly (I think), in a song, if a bass drum is hit while a singer is singing, how can both of these frequencies be carried on the same line at the same time? In other words, how can one signal come through an antenna, and result in a subwoofer and tweeter each vibrating at different frequencies, but at the same time.

I am currently studying electrical engineering in school, so I do have some idea of how various types of passive and active circuit components work and behave at different frequencies. All this to say, hopefully there's no need to break answers down to a grade school level.

what you are asking is not normally called data transmission but rather signal processing
but that aside, you find the answer in http://en.wikipedia.org/wiki/Frequency_modulation

Oh wow, that actually explained it well. Also watched this Youtube video: http://www.youtube.com/watch?v=SmW4z76KgNQ

Edit: From what I understand, the signal that a radio station broadcasts isn't fixed at 90.1 MHz, it actually varies between 90.1 MHz +/- 75 KHz. I thought it was fixed, so that was my misunderstanding.

Any clue about the second question? It seems to me like frequency modulation works if one of the frequencies is already known (in this case the 90.1 MHz is known), but if two sounds are being played at the same time (bass drum + singer's voice), both frequencies are unknown. How can they be transmitted at the same time?

This post was edited by SexualNinja on May 21 2014 08:12am

Super high level version, lol

you still aren't grasping the fact that its not direct sound wave transmission.

radio waves=/=sound waves.

data is encoded onto the radio wave and decoded by the receiver which then uses the code to produce the sound waves.

"but if two sounds are being played at the same time (bass drum + singer's voice), both frequencies are unknown"

why would they be unknown?

Not sure what I ever said that made you think I don't understand that. As I said, I thought the wave that reached your car's antenna was fixed at a MHz value. I thought that if it was fixed at this value, there was no data and there should only be silence coming from your speakers. Turns out that the frequency isn't fixed, it's a MHz value +/- 75 KHz. And that part now completely makes sense to me. So "carrier frequency" + "baseband signal" = "transmitted signal". Here's my next question.

The carrier frequency is fixed at 90.1 MHz. Also, at any one time, the baseband signal is at a single instantaneous frequency. If the baseband signal is at one frequency at any instant, how can it contain the data required to produce two different sounds, or make two speakers vibrate at two different frequencies?

This post was edited by SexualNinja on May 21 2014 08:54am

Just a guess, but does a Fourier transform have anything to do with it?

frequency modulation.

That's the answer to the first question from the OP. Still looking for the second.

This post was edited by SexualNinja on May 21 2014 10:38am

fm modulation is the coding process so once you understand the coding process then you will understand how the data is implemented.

you will also need to learn about demodulation once you learn about modulation in order to get a picture of the entire process.

This post was edited by Subwoofer on May 21 2014 11:20am