Radio and Wireless Signals

When electric current wiggles back and forth very quickly in a wire called an antenna, it sends out radio waves: a kind of electromagnetic wave, the same family as light, but with waves far longer than our eyes can see. Another antenna, even far away, picks up a tiny copy of that wiggle.

Each station sends at its own frequency: how many times per second the wave wiggles, measured in hertz (Hz). FM radio stations in Canada are between 88 and 108 megahertz (millions of wiggles per second). Wi-Fi uses about 2.4 or 5 gigahertz (billions).

Radio is everywhere: phones, Wi-Fi, Bluetooth, GPS, garage door openers, and the wireless sensors on many home weather stations that send readings to the indoor console.

A plain, steady wave (the carrier) carries no information. To send sound or data, the transmitter changes the wave, which is called modulation:

• AM (amplitude modulation) changes the wave’s strength to follow the sound. Canadian AM stations are between about 530 and 1,700 kHz.
• FM (frequency modulation) shifts the frequency slightly up and down instead. FM is much less affected by electrical noise, like lightning crackle.
• Digital signals switch between patterns that stand for 0s and 1s (Lesson 19), which is how Wi-Fi, Bluetooth and phones work.

A receiver uses a tuned circuit of a coil and a capacitor that responds strongly to just one frequency, much like a swing that goes highest when it’s pushed at just the right rhythm. Turning the tuning knob changes the coil or capacitor, choosing a different station. Then a detector recovers the sound from the wave. In the simplest AM radios, the detector is a diode (Lesson 9).

The radio spectrum is shared by everyone, so it’s managed by law. In Canada, Innovation, Science and Economic Development Canada (ISED) decides which services use which frequencies and licenses transmitters, so broadcasters, aircraft, emergency services and others don’t interfere with each other.

Anyone can listen to broadcast radio, but most transmitting needs permission. Wi-Fi, Bluetooth and FRS walkie-talkies don’t need a licence, but they must be certified by ISED. Amateur (ham) radio is the exception made for learning: after passing ISED’s Basic Qualification exam, people in Canada can operate their own stations on bands set aside for amateurs and assemble commercial transmitter kits; the Advanced Qualification lets them design and build their own transmitters. There’s no minimum age, and some ham operators earn their certificate while still in school.

Weather and radio have a long history together in Canada. Environment and Climate Change Canada’s Weatheradio service broadcast forecasts on VHF frequencies near 162 MHz for decades, until it closed in March 2026; Environment and Climate Change Canada now points people to its WeatherCAN app and website, and the most urgent warnings, such as tornado warnings, reach phones, TV and radio through the national Alert Ready system.

About 3 m (300 ÷ 100).

Changing a carrier wave so it carries sound or data, for example by changing its strength (AM) or frequency (FM).

The tuned circuit: a coil and capacitor that respond strongly to one frequency.