How FM Radio Changed the Way We Listen

Radio could deliver music to a living room, but in the 1930s, that music often came accompanied by crackly static. Thunderstorms and electrical equipment interfered with both sound and speech. Edwin Howard Armstrong realized that listeners did not have to endure this interference.

On November 5, 1935, Armstrong invited a group of engineers in New York to hear his new FM radio for themselves. For the first time, they experienced music and voices coming through the air without all the usual static. Today, almost a century later, we still celebrate the moment Armstrong helped make radio sound clear and true.

Armstrong and Radio Interference

Armstrong had been engaged in radio research for many years prior to studying interference. Armstrong had attended Columbia University to study electrical engineering and had also become a member of the faculty there.

Back then, most people listened to the radio using AM stations. These stations sent music and voices by changing the strength of their signals. But whenever there was a thunderstorm or other electrical noise, those signals would get scrambled, filling living rooms with crackles and pops.

FM is short for frequency modulation. FM transmits sound by varying the frequency of a radio signal rather than the amplitude. A well-designed FM receiver can reject much of the interference in amplitude while still receiving the transmitted signal.

Armstrong’s system used a technique called wideband FM. This system utilized a wider frequency range. Armstrong found that wideband FM could dramatically reduce interference. This discovery was significant because it disproved some of the beliefs that had caused earlier FM research to falter.

A Demonstration That Was Heard

For his 1935 demonstration, Armstrong had his friend transmit a signal from his home in Yonkers, New York. Armstrong clearly transmitted the sounds of paper being torn and water being poured, as well as music, to his audience.

This allowed concrete sounds to serve as a basis for the audience. A good transmission would allow speech to be clearly heard and small details to be preserved. This demonstration also showed the value of small details, free from the interference that often plagued radio at the time.

Armstrong also published a technical report in May 1936 describing his system. The report detailed transmitting and receiving equipment used in his system, explained how interference was reduced, and included results from experimental transmissions.

Beyond the Lab

Back then, families listened to music and news on their trusty AM radios, and stations were set up for the old technology. When FM came along, it wasn’t easy for everyone to make the switch. People needed to buy new radios and figure out how to use them. The change took time, and both broadcasters and listeners had to get comfortable with something unfamiliar.

Armstrong continued to work on FM. In 1939, Armstrong set up an experimental FM station in Alpine, New Jersey.

Armstrong’s research also helped lay the groundwork for high-fidelity FM transmission. Armstrong’s 1935 demonstration made the possibility of high-fidelity FM transmission audible. Engineers could also hear the value of research conducted over the years.