Sine and Cosine Graphs Compared to Sounds Waves

Sound Waves

Cosine Graph

Sine Graph

 Sound waves are a type of sine and/or cosine graphs that overlap and create sound using various amplitudes and frequencies.

How Radios Work

  Radios take electromagnetic waves and turn them into sound. They travel through the air like light. They broadcast using modulation and amplification. Modulation allows the manipulation of waves so that people hear different frequencies in succession which registers and different sounds to your ear. The amplification allows a broader range of sound that can be transmitted. Radios change waves into sound through the reciever and antenna. The antenna recieves the signal and sends it to the receiver which conducts it through a series of circuits and vacuum tubes. The circuits and tubes work like sophisticated  and powerful coherers (signal detectors) to convert the electromagnetic waves back into sound waves using the amplitude modulation. That's how radios work.

 

AM vs. FM

AM vs. FM Modulation

There are two types of radio broadcasting: AM and FM. The difference between them isn't how the radio works. That is the exact same in both FM and AM radios. (See How Radios Work) The difference is how the carrier wave is altered. AM radios use the amplitude or strength of the waves are varied to carry the sound information. With the FM radios, the frequency, the number of times that the current changes direction each second, of the carrier wave is altered. Most people use FM stations because both AM and FM are susceptible to slight changes in amplitude. When this happens in an AM radio, the listener hears static. With an FM signal, the changes don't alter the sound because the amplitude does not effect the frequency. The receiver of the FM waves just look over the changes in amplitude, so this results in no static at all. 

History of the Radio

1888: Heinrich Hertz made the first electromagnetic radio wave.
1894: Sir Oliver Lodge sent the first message using radio waves in Oxford, England. 
1899: Guglielmo Marconi sent radio waves across the English Channel.
1901: Marconi sent waves across the Atlantic from Cornwall, England to Newfoundland 
1906: Reginald Fessenden became the first person to transmit a human voice using radio waves. He sent a message from Brandt Rock, Massachusetts to ships eleven miles off the coast. 
1906: Lee De Forest invented a triode or audion. This is an electrical component that made radios smaller and more compact. This earned him the nickname "father of the radio."
1910: The first public radio broadcast was made from the Metropolitan Opera, New York City.
1920s: During the 1920s, the radio began to evolve into the television. 
1947: The first transistor was created by John Bardeen, Walter Brattain, and William Shockley. They worked for Bell Lades. The transitor made it possible to amplufy radio signals with more compact circuits. 
1954: The world's first commercially produced transistor radios were launched. In the first year, 1500 were sold. By the end of 1955, over 100,000 were sold. This radio was called the Regency TR-1.