June 1 marked the golden anniversary of FM stereo broadcasting in the United States.
It was on that date in 1961 that three stations in Schenectady, Chicago and Los Angeles lit up 38 kHz subcarriers at midnight (ending May 31) in their respective time zones, and rolled out the stereo broadcasting with equipment that had been given FCC type approval only hours before.
The three stations — GE’s WGFM in Schenectady; Zenith Radio’s WEFM in Chicago, and Los Angles’ KMLA — became the first implementers of the backwards-compatible multiplex system for transmitting stereo signals, which was based on Zenith and General Electric inventions.
The transmission methodology — in which left and right signals are summed together and sent along the main FM channel, and a left/right difference signal created and carried by a multiplexed subcarrier — had been winnowed down from more than a dozen systems vying for FCC approval.
The early-morning June 1, 1961 FM stereo broadcasts lasted for only a few hours, but paved the way for a stereo transmission system that eventually gained global acceptance and even after 50 years shows no signs of fading away.
— James E. O’Neal