If we look back at when radio was invented, Marconi used a "spark gap transmitter" to get his telegraph data to travel through the air. Today, spark gap transmitters are illegal, because they produce radiation across nearly the entire radio frequency...

"Frequency modulation" is a very broad term that means that you are imposing data on the signal by changing the frequency, as opposed to changing the amplitude (amplitude modulation). There are many frequency modulation techniques, but I'll talk abou...