Sound through the air
Radio was the first technology to send voices and music through the air, without wires, to anyone with a receiver. It brought news, sports, music and stories into homes across the world. Today, the same technology carries cell phone calls, Wi-Fi, GPS and much more.
The science behind radio
In the 1860s, Scottish physicist James Clerk Maxwell predicted invisible electromagnetic waves that travel at the speed of light. In 1887, German physicist Heinrich Hertz proved they existed by sending sparks across his lab. These are radio waves.
Radio waves are part of the electromagnetic spectrum, like light, but with much longer wavelengths: from about a metre to many kilometres.
Inventing radio
| Year | Inventor | Achievement |
|---|---|---|
| 1887 | Heinrich Hertz (Germany) | Produced and detected radio waves |
| 1890s | Jagadish Chandra Bose (India), Nikola Tesla, others | Experiments with wireless signals |
| 1895 | Guglielmo Marconi (Italy) | Sent wireless telegraph signals over 2 km |
| 1901 | Marconi | Received the first transatlantic wireless signal, the letter "S" in Morse code, at Signal Hill, St. John’s, Newfoundland |
| 1906 | Reginald Fessenden (born in Quebec) | First radio broadcast of voice and music, on Christmas Eve |
| 1920 | XWA (later CFCF), Montreal | One of the world’s first scheduled radio broadcasting stations |
| 1920 | KDKA, Pittsburgh | Broadcast U.S. presidential election results |
Marconi built wireless stations at Glace Bay, Nova Scotia, which began regular transatlantic message service in 1907. Fessenden, sometimes called the "father of radio broadcasting," was the first to transmit the human voice by radio.
How radio works
At the station
- A microphone turns sound into an electrical signal.
- A transmitter combines that signal with a steady carrier wave at the station’s frequency. This is called modulation.
- The signal is sent to an antenna, which radiates radio waves in all directions.
At home
- The receiver’s antenna picks up radio waves from many stations.
- A tuner selects one frequency.
- The receiver separates the sound signal from the carrier wave.
- An amplifier strengthens it, and a speaker turns it back into sound.
AM and FM
| AM (amplitude modulation) | FM (frequency modulation) | |
|---|---|---|
| How sound is carried | Changes the height (amplitude) of the wave | Changes the spacing (frequency) of the waves |
| Frequency range | 530–1700 kHz | 88–108 MHz |
| Range | Long; signals can travel hundreds of km, especially at night | Shorter, about 50–100 km |
| Sound quality | More static | Clearer; better for music |
| Common uses | Talk radio, news, sports | Music |
AM signals travel farther at night because they bounce off a layer of the upper atmosphere called the ionosphere.
The golden age of radio
From the 1920s to the 1950s, radio was the centre of family entertainment, with music, comedy, drama, sports and news.
- Hockey Night in Canada started on radio in the 1930s, with Foster Hewitt’s famous call, "He shoots, he scores!"
- The Canadian Radio Broadcasting Commission was created in 1932, becoming the CBC in 1936.
- During World War II, radio brought news from the front to families at home.
- CBC radio reached remote and northern communities, connecting a huge country.
Radio in emergencies
Radio is still vital during emergencies, because battery-powered or crank radios work even when the power and internet are out. Canada’s Alert Ready system broadcasts emergency alerts on radio, TV and cell phones.
Radio technology today
Radio waves now carry far more than broadcasts:
| Use | Example |
|---|---|
| Mobile phones | Calls and data |
| Wi-Fi and Bluetooth | Wireless internet and devices |
| GPS | Satellite navigation signals |
| Satellite radio and digital radio | Clearer sound, more channels |
| Aviation and marine radio | Communication with pilots and ships |
| Radar | Detecting aircraft and weather |
| Radio astronomy | Studying distant galaxies |
| Amateur ("ham") radio | Hobbyists communicate worldwide |
Internet radio and podcasts have also changed how people listen.
Common mistakes
- Thinking radio waves are sound waves. They’re electromagnetic waves that carry a sound signal.
- Thinking only one person invented radio. Many scientists contributed.
- Thinking radio is outdated. Radio waves power much of modern communication.
Try it yourself
- Tune an AM radio at night and try to pick up distant stations. Note the cities you hear.
- Make a list of every device in your home that uses radio waves.
- Research the first radio station in your province.
Quick recap
- Radio uses electromagnetic waves to send sound without wires.
- Hertz proved radio waves exist; Marconi sent signals across the Atlantic to Newfoundland in 1901.
- Fessenden made the first voice and music broadcast in 1906.
- AM changes wave height; FM changes wave spacing.
- Radio waves now carry phone, Wi-Fi, GPS and emergency alerts.