Modulation frequencies we know as radio or FM radio patented December 26, 1933 in America by Edwin Howard Armstrong. Through the regulation of the Federal Communications Commission (FCC) W1XOJ station broadcasts its broadcast for the first time on January 5, 1937 which demonstrated directly by Armstrong in the 42-49MHz frequency spectrum and the frequency of the FCC gave permission for commercial use, which then formed the Yankee Network for broadcasting device sales FM radio (until the year 1945 to 55 FM radio stations), with propaganda FM quality is much better (and get stereo) rather than AM radio (Amplitudio Modulation), which had already been used.
In 1945 Radio Corporation of America (RCA) urged the FCC to move the FM frequency to a higher (88-108MHz) due to interference with television signals and to widen the use of television frequencies by shifting the frequency of 40MHz FM. Armstrong has failed to shift the FM patents to higher frequencies. RCA then Armstrong took over patent that makes crushed Yankee Network, until Armstrong's suicide jump from his apartment, tragic! Then his ex-wife with the widow Armstrong filed a patent trial to be restored in 1967.
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