This section contains 455 words (approx. 2 pages at 300 words per page) |
The invention of frequency modulation (FM) was a great improvement over amplitude modulation (AM) radio. Reginald Aubrey Fessenden made the world's first AM radio broadcast in 1906. With amplitude modulation, the amplitude (the distance between the "peak" and " trough") of the radio wave "carrier" is modulated to match the frequency of an audio signal. AM radio made the transmission of voice and music possible, but it was prone to interference by lightning storms and the earth's ionosphere. In 1924 Edwin Howard Armstrong invented the way to modulate the frequency of the wavelengths, rather than the amplitude. The actual frequency of the oscillations of the carrier wave is modulated to match the frequency of the audio signal; the amplitude of the radio wave stays the same, but the frequency changes. An early way of doing this was by using a vacuum tube. The capacitance between the anode and cathode...
This section contains 455 words (approx. 2 pages at 300 words per page) |