Inventor: Edwin Howard Armstrong

• Invented in 1933
• Alternate form of signal modulation from amplitude modulation used in today's radio system

Before FM (frequency modulation), AM (amplitude modulation) was used. AM modulation had a radio signal that was proportional to the audio signal being transferred. Unfortunately, many natural signals were modulated in that way, and resulted in a lot of interference. FM modulation is changing the frequency of the main signal instead of the amplitude, resulting in less interference, as fewer signals are varied in that way. Despite the benefits of FM, it had many problems and never reached its full potential. RCA did not license FM when Armstrong first presented it to the company, so Armstrong went to smaller companies and designed transmitters, receivers, and antennas to test in New York and New England. The music was much higher quality than anything else in the day- better than phonographs, and became very popular. RCA launched attacks on FM radio through the FCC, causing its frequency to be moved and making all infrastructures obsolete. This crippled FM broadcasting, allowing AM to be around to this day, despite becoming obsolete over 60 years ago.

Picture from Encarta Encyclopedia.

Bellis, Mary. "The History of the Microscope." About.com. Available 10 April 2004. <http://inventors.about.com/library/
inventors/blmicroscope.htm#Germans>

• This site had a biography of Armstrong, and had a lot of detail about the conflicts with RCA over FM.