Nicole Marie Stedman, age 16, of Marion, Ohio, for her question:
HOW ARE RADIO PROGRAMS TRANSMITTED?
Three steps are involved in transmitting a radio program. First of all, you have to create the communication signals and change them into radio waves. Second, you must transmit or send the radio waves. And finally, you must receive the radio waves and change them to a form that can be understood.
To understand radio broadcasting, you must first understand what sound is. All sounds consist of vibrations. Sound travels through the air in the form of waves called sound waves.
During a radio broadcast, a microphone picks up speech and other sounds that make up the program. An electric current runs through the microphone. When the sound waves enter the microphone, they disturb the current in the microphone, creating vibrations in it that match the sound waves.
The electric waves that represent the sounds of the program travel over wires to a control board. The control board has many switches and dials. A technician controls the sounds and varies the volume or loudness of each sound. From the control board, the waves go to the transmitter.
The transmitter strengthens the incoming electric waves representing the broadcast. The transmitter also produces another kind of electric waves called carrier waves. It combines the carrier waves with the electric waves from the radio station. This combination becomes the radio signal that brings the program to radios.
The transmitter sends the radio signals to an antenna. The antenna, in turn sends the signal out into the air as radio waves.
There are two ways that the radio program can be transmitted: AM and FM. The factor that influences the distance a program can be broadcast is the power of the transmitter. The strongest AM stations have a power of 50,000 watts. Some FM stations have 100,000 watts.
Each station transmits on a different channel or assigned frequency.
A program carried by radio waves travels at the speed of light. This speed is 186,282 miles per second. By contrast, sound waves themselves move through the air at a speed of only about one fifth of a mile per second.
As a result of this difference in speed, a surprising effect occurs. Let us say that a live radio broadcast of a concert in Los Angeles is going to listeners in New York City. The music would reach the radio listeners in New York a fraction of a second before it reaches the audience in the back of the concert hall in California.
Radio waves cannot be seen, heard or felt in any way. But radio receivers pick them up and turn them into sound waves that make up radio programs.
The main parts of an electrically powered radio include: the antenna, the tuner, amplifiers and the speaker.
The antenna receives radio waves from many stations. The tuner of a radio makes it sensitive to particular frequencies. A dial attached to the tuner shows the frequencies, or channels, of the stations that may be tuned in.
Amplifiers strengthen the program signal selected by the tuner.
The speaker is the final link between the broadcasting studio and the listener. It changes the electric signals back into the original program sounds.