Radio waves transmit music, conversations, pictures, and data invisibly through the air, often over millions of miles — it happens every day in thousands of different ways! Even though radio waves are invisible and completely undetectable to humans, they have totally changed society. Whether we are talking about a cell phone, a baby monitor, or any one of the thousands of other wireless technologies, all of them use radio waves to communicate. In this activity, you will learn more about radio transmissions.

How does NASA communicate with spacecraft? Messages travel through space as radio waves, just like the radio waves that you receive with a car radio. Each spacecraft has a transmitter and a receiver for radio waves as well as a way of interpreting the information received and acting on it. Radio waves from a spacecraft need to be received on Earth and are often quite weak when they get here. NASA has huge radio receivers to gather information from space missions. These must be precisely aimed so they can get the waves. Likewise, NASA must precisely aim transmissions to spacecraft so that these ships can hear the messages.

Radio waves were first transmitted in the 1800s and were thought to be an amazing discovery as people could communicate with each other from far distances. However, as time went on, people started to take radio waves for granted, and now, hardly anyone realizes how much we actually use radio waves as part of our everyday lives. The biggest use for radio waves is communication, such as cell phones, emails, and texting. However, surprisingly, there are many other uses for radio wave transmissions that we use every day, such as:

• television
• wireless networks
• mobile phones
• GPS systems
• garage door openers
• wireless clocks
• police radios
• radio controlled toys

Satellites and Radio Waves

Satellites orbiting the Earth communicate with stations on the ground using radio waves. The only difference between the radio waves picked up by the satellite radio on your office desk and those used for traditional FM and AM broadcasts is the wavelength and frequency. The government allocates specific frequencies for commercial, scientific, and military satellites so they don't interfere with your television and other kinds of radio communications.

The Need For Satellites

Most commercial radio signals do not travel more than a few hundred miles at most, and the curvature of the Earth limits high-frequency radio to about 60 miles. Radio signals follow a straight line from the transmission antenna, called the line of sight; any position that cannot see the antenna tower cannot receive the signal. Some radio signals bounce off the upper layers of the atmosphere back to Earth, but these happen unpredictably; most of the waves go straight into space. Satellites allow radio communications to travel reliably around the Earth.