Who led the FM radio revolution in the 1920s and 1930s?

• A. Guglielmo Marconi
• B. Nikola Tesla
• C. Edwin Howard Armstrong
• D. Lee de Forest

Answer: (C)

The main idea tested here is identifying who drove the shift to frequency modulation, which made radio sound much clearer. Frequency modulation encodes the audio information in changes to the carrier frequency rather than its height, so it’s far less affected by static and noise from electrical interference or weather. Edwin Howard Armstrong was the key figure who developed and championed this approach in the 1920s and 1930s, securing patents, conducting pivotal experiments, and pushing for its practical use in broadcasting. His work demonstrated that FM could deliver high-fidelity sound, especially for music, and laid the groundwork for modern FM radio.

Other pioneers did important things in the broader history of radio. Guglielmo Marconi helped establish wireless communication, but not the FM technique. Nikola Tesla contributed fundamental ideas about electricity and radio concepts, and Lee de Forest invented the Audion amplifier that boosted early radio signals; however, they did not lead the FM revolution Armstrong did.