Communications System How does NASA communicate with spacecraft?

How is data put on radio waves?

There are two common ways to put information in a radio wave, and you've likely run into them yourself. They are called A.M. and F.M. just like the two choices you've always known are on a radio. To understand these two ways of sending information it is important to know that radio waves, by themselves, have very regular patterns. Generally they keep the same amplitude or frequency all the time. (Amplitude is the "height" of the radio wave, frequency is how close the waves are to each other.)

A.M. stands for amplitude modulation. In this method, the information is put into a radio wave by varying the amplitude. For example, if all we wanted to do was send 1's and 0's, we could have just two different levels of amplitude that correspond to these numbers--1 being high, 0 being low.

F.M. stands for frequency modulation. This time the amplitude is kept constant, it is the frequency that is varied..