Waves of Change: From Sparks to Stereo – The Evolution of Radio

-Karthik Gurumurthy

Radio is this amazing technology that lets us hear someone’s voice from thousands of miles away. It works by sending electromagnetic waves through the air – these waves are much longer than light waves, ranging from tiny fractions of an inch to several miles long!

The whole concept started with Scottish physicist James Clerk Maxwell, who mathematically described electromagnetism in 1865 and theorized that radio waves existed. Then in 1890, Elihu Thomson generated radio waves using electrical current through a spark induction coil. Around the same time, German physicist Heinrich Hertz built a simple receiver using two metal balls with a wire loop – when exposed to radio waves, sparks would jump between the balls.

Croatia born American Nikola Tesla made a huge leap in 1893 with what he called a “wireless telegraph,” sending radio signals over 25 miles and even controlling a model ship remotely – pretty impressive for the 1890s!

But the real superstar was Guglielmo Marconi, who’s considered the father of modern radio. He combined different instruments to increase transmission distance, and on December 11, 1901, he shocked the world by sending a radio signal across the Atlantic Ocean between England and Newfoundland – over 2,000 miles! Scientists were baffled about how the signal could bend around Earth’s curvature until Edward Appleton discovered the ionosphere in 1924, which reflects radio waves back to Earth.

The first voice broadcast happened on December 24, 1906, when Reginald Fessenden transmitted his voice and music along the U.S. Atlantic coast. He invented a high-frequency alternator that produced continuous radio waves and developed amplitude modulation (AM) – where sound signals are carried by varying the strength of radio waves.

Radio took another big leap when John Ambrose Fleming invented the vacuum tube, which made more powerful transmitters and sensitive receivers possible. Then in 1912, Edwin Howard Armstrong created a receiver that amplified signals enough to use loudspeakers – before this, you could only listen through headphones!

Between 1925 and 1933, Armstrong developed frequency modulation (FM) radio, where the sound signal is carried by varying the frequency rather than amplitude. This was a game-changer because FM produced much clearer sound with less static and distortion.

The first radio set with transistors instead of vacuum tubes – the Regency – hit the market in 1954, and by 1957, Sony was making pocket-sized transistor radios. This was revolutionary because early radio receivers used to be as big as furniture due to the vacuum tubes!

There’s some debate about which was the first broadcasting station, but KDKA in Pittsburgh is widely considered the pioneer. On November 2, 1920, they broadcast election returns from the presidential race between Warren G. Harding, James M. Cox, and Eugene V. Debs. By September 1921, station WBZ in Springfield, Massachusetts got the first regular broadcasting license, and within a year, over 500 stations were licensed.

The science behind radio is fascinating. AM and FM waves work differently – AM varies the strength (amplitude) of the carrier wave while FM varies the frequency itself. AM can travel much farther because the waves reflect off the ionosphere and Earth’s surface, allowing them to curve around the planet. This is especially true at night when the ionosphere sinks lower. That’s why a small portable radio in Detroit can pick up stations from New York or St. Louis after dark!

FM, on the other hand, uses higher frequencies (88-108 MHz compared to AM’s 550-1600 kHz) and the waves pass straight through the ionosphere into space. This limits FM to line-of-sight transmission of about 50-100 miles. But FM has better sound quality, which makes it ideal for music and stereo broadcasting.

Radio waves travel at the speed of light (186,282 miles per second), which is why broadcasts can cross oceans in the blink of an eye. When you tune in, your receiver antenna picks up the waves, separates the sound information from the carrier wave, and converts it back to sound through your speakers.

It’s pretty incredible how radio has evolved from Marconi’s early sparks to the digital broadcasts we have today!