Learn

about radio

These modules will lead educators through key concepts in the science, engineering and social impacts of radio frequency technologies.

It explores the pervasiveness of radio and its role in modern communication, highlighting how engineers use electromagnetic waves to transmit information and the challenges of a limited radio spectrum. It also examines the societal impact and future potential of radio, emphasizing the need for equitable technology development through collaborative efforts.

What is radio?
Radio is everywhere. It is invisible energy carrying data between cell phones and information from Earth to orbiting satellites. Radio waves are also emitted by our planet, objects in outer space, and events like starting a car or turning on a light.

Radio is a field of scientific and technological research making significant changes in how we communicate, work and live. Wireless connectivity plays a starring role in history and our future, encompassing everyday communication, healthcare and remote monitoring systems.

When the first radio communication was used to send a message across great distances using wireless telegraphy in 1895, the airspace was changed forever. Today, radio waves are used by wireless laptops, remote-control car locks, AirPods and Internet-of-Things devices. Radio is employed for air traffic control, spacecraft communications and astronomical research.

Radio frequency technologies continue to be developed through innovations in science and engineering. Equally important for society are the policies governing radio usage by everyone.

Like many innovative technologies on the horizon, it is vital that everyone is informed about radio and has a voice in how it shapes our future. We each have a role to play. Our decisions about how to use and share the radio spectrum shape our individual lives, society and the world.
Every electrical device, including the wires and appliances in your home, generates an electromagnetic field.
Our eyes can perceive visible light, a type of electromagnetic (EM) radiation, but they are incapable of detecting other forms of the EM spectrum, including radio waves.
AM/FM Radios are designed to receive specific frequencies of EM radiation and convert this energy into sound.
Microwave ovens use EM radiation to transfer energy directly to water molecules, thereby heating up food.
Sunglasses and sunscreen block or filter specific kinds of EM radiation, like ultraviolet (UV) light.
Computers and cell phones transmit and receive information using technologies that function within the radio frequency spectrum.
X Ray machines use high-energy "ionizing" EM radiation, which is different from the low-energy "non-ionizing" radiation found in radio waves and light.
Astronomical telescopes capture EM radiation emitted by interstellar objects, such as quasars and nebulas. Almost all astronomical events generate radio waves.
Electromagnetic radiation is around us at all times
Radio is a form of electromagnetic (EM) radiation. Light and energy from the sun are also EM radiation, as are infrared light and microwaves.
Electromagnetic radiation in everyday life
Every electrical device,
including the wires and appliances in your home, generates an electromagnetic field.
Our eyes
can perceive visible light, a type of electromagnetic (EM) radiation, but they are incapable of detecting other forms of the EM spectrum, including radio waves.
AM/FM Radios
are designed to receive specific frequencies of EM radiation and convert this energy into sound.
Microwave Ovens
use EM radiation to transfer energy directly to water molecules, thereby heating up food.
Sunglasses & Sunscreen
block or filter specific kinds of EM radiation, like ultraviolet (UV) light.
Computers and Cell Phones
transmit and receive information using technologies that function within the radio frequency spectrum.
X-Ray Machines
use high-energy "ionizing" EM radiation, which is different from the low-energy "non-ionizing" radiation found in radio waves and light.
Astronomical Telescopes
capture EM radiation emitted by interstellar objects, such as quasars and nebulas. Almost all astronomical events generate radio waves.
Radio waves are different lengths
Waves carry other waves
Radio communication relies on systems made up of many technologies
Each band of the radio spectrum has advantages and limitations
Buildings, weather and natural landscapes can interfere with EM communication
Radio waves are different lengths
Electromagnetic (EM) radiation travels in the form of a wave, classified by each wave's length – or wavelength. Radio waves vary in wavelength, ranging from as small as a millimeter to as long as a hundred kilometers – about 62 miles! These varying wavelengths make up the "radio spectrum," which is a segment of the broader EM radiation range characterized by the longest wavelengths.
Sections, or "bands," of the spectrum are defined by their range of wavelengths. Another common method to describe radio wave lengths is through their frequency—the number of waves that form in one second. Frequency can be measured in hertz (Hz), megahertz (MHz) and gigahertz (GHz). One Hz equals one cycle per second, while one GHz equals one billion cycles per second.
The radio band, characterized by its long wavelengths, is highlighted within the full EM spectrum. The portion depicted as a rainbow represents the band of visible light that is detectable by our eyes."
AM Radio
The EM wave transmitted by AM Radio stations can be as long as a city block (580 ft to 1,820 ft).
Wi-Fi
A 5GHz WiFi router transmits EM waves about as long as the bee hummingbird, the world's smallest bird (6cm).
5G
Millimeter waves, found within the bands used for 5G communications, can have wavelengths about as long as a grain of rice, roughly 7.7mm.
Waves carry other waves
We send information or data by altering a "carrier wave"—a wave with a specific known frequency. When you tune into 102.7 FM in your car, the carrier wave for that radio station is 102.7 MHz. Carrier waves alone don't carry information; thus, a transmitter modifies the electrical output in an antenna, changing the wave to encode information onto it. A receiver tuned to the carrier frequency can detect these modifications and decode them back into the transmitted information.
Today, most radio communications transmit digital information. This digital data consists of a series of bits (top row). Through a special circuit with an antenna, these data bits are encoded onto a radio wave using a technique called modulation. The carrier wave (middle row) has a known frequency. To convey data, either the frequency (or wavelength) or amplitude (height) of these waves is altered, allowing a receiving device to interpret the data based on these changes in the carrier waves (bottom row). Here, periods of high and low amplitude represent binary digits (1s or 0s), each being a "bit." In some applications, such as Bluetooth, the phase, or timing, of the waves is also adjusted to encode information.
Digital Modulation
Analog data doesn't resemble a sequence of 1s and 0s but instead exhibits a pattern that varies constantly along a continuum. Similar to digital data transmission, analog data is sent by modifying the frequency, amplitude or phase of a carrier wave. In the case of old television signals, the amplitude, frequency and phase of radio waves were manipulated to control the brightness, sound and color of the display.

Processes of encryption are often used to make sure that information can travel securely from place to place. Signals are mixed up or “shredded” so that only a device with the matching key can interpret them correctly.
Radio communication relies on systems made up of many technologies
How did the data center find James?
Our cell phones continuously send brief messages to nearby towers, and one antenna in your phone is dedicated solely to this task. Both your phone and SIM card have unique identification numbers, as does each tower. When a tower picks up a location signal—a "ping"—from your phone, it relays a message to the data center. Consequently, the data center is always aware of the last tower that received a signal from your phone.

As soon as a tower receives information that a message is incoming for your phone, it coordinates with your device to select a specific frequency for use—like a dedicated radio or television channel. Additionally, a specific time slot is reserved for this communication. During this allocated time, no other phone connected to the tower will use that same frequency, ensuring a clear and uninterrupted connection for your message.
The path differs for each kind of device
The communication pathway varies depending on the type of device. Radio signals are just one of the numerous links in the communication chain. For instance, when using Wi-Fi, radio waves transport information to a router in your house, and from there, the data travels through copper or fiber optic cables. In contrast, some devices, like walkie-talkies and certain Internet-of-Things (IoT) devices, may communicate directly with each other via radio. Additionally, satellites are increasingly becoming an integral part of this communication chain.
Each band of the radio spectrum has advantages and limitations
Each band of the radio spectrum has distinct characteristics, such as the amount of energy needed to use them, the distance they can carry information and their interaction with molecules in air, water and various materials. These unique features of each radio spectrum band make them useful for different purposes. Generally, longer radio waves travel farther.
Today, most radio communications transmit digital information. This digital data consists of a series of bits (top row). Through a special circuit with an antenna, these data bits are encoded onto a radio wave using a technique called modulation. The carrier wave (middle row) has a known frequency. To convey data, either the frequency (or wavelength) or amplitude (height) of these waves is altered, allowing a receiving device to interpret the data based on these changes in the carrier waves (bottom row). Here, periods of high and low amplitude represent binary digits (1s or 0s), each being a "bit." In some applications, such as Bluetooth, the phase, or timing, of the waves is also adjusted to encode information.
Did you know?

Antennas are carefully matched to the length of the waves they send or receive. To capture as much of the wave's energy as possible, most types of antennas need to be 1/4 or 1/2 the length of the wavelength. Antennas use unique shapes and techniques to fit in a compact space.
Option 3
mmWave
New 5th generation systems can use very short waves, 24-40 GHz. Your signal would only travel ¼ mile–2 miles and could be blocked by almost anything in the way, but your antenna could be smaller than a penny! With these systems, data are passed from tower to tower until a hub connects to fiber optic cable.
Option 2
X band
The Mars rover communicates directly with Earth over the X band, from 7-8 GHz. If your friend is 140 million mile away, you’ll use NASA’s Deep Space Network antenna, 112 feet wide, to send Elmo their way. Your friend can receive the signal using an antenna only 1 foot wide (and shaped like a hexagon).
Option 1
Very low frequency radio
The band from 3-30 kHz is used for navigation and communicating with submarines. Signals can follow the curve of the Earth and travel around obstacles. They can reach your friend up to 1,000 miles away or even 120 feet under the sea. You will need an array of antennas, each almost 1,000 feet tall.
Challenge

Let’s say you have your own transmitter and want to send all 49 years of Sesame Street episodes to a friend. (That’s 1,346 hours and growing!) What band should we use?
Wider is faster
In advertisements, we often hear about new technologies with higher speed data transmission, or “throughput.” Many of these, like 5G systems, utilize higher frequency (shorter wavelength) radio waves.

However, what is most critical is the amount of the radio spectrum these technologies use – the "bandwidth" they require to send and receive data. Bandwidth can be compared to the width road, and data is similar to cars trying to pass through. Just like traveling home in the middle of the day is far easier than making the same journey during rush hour – a narrow bandwidth can become a bottleneck during high data traffic periods.
The capabilities of communications systems are changing as protocols, algorithms and hardware advance. New technologies not only use existing bandwidth more efficiently but also access greater bandwidth for data transmission by operating at higher frequencies, which typically face fewer usage conflicts. Though a technology may be able to operate across a wide range of frequencies, the bandwidth a device uses at any given moment is much narrower. For example, 2.4 GHz Wi-Fi operates within a frequency range of 2.4-2.5 GHz (a 100 MHz band), but each individual Wi-Fi channel only use 10-20 MHz of that bandwidth at a time.
Buildings, weather and natural landscapes can interfere with EM communication
Waves in different bands of the EM spectrum interact with materials differently. For example, visible light can pass through your sunglasses, yet many lenses are capable of blocking 100% of ultraviolet light, protecting your eyes from damage while allowing you to see. Similarly, radio waves can easily pass through air, glass, and wood, but they are absorbed by water and reflected by metals.
What is happening when waves are blocked or weakened?
Radio waves can be absorbed, reflected, or scattered by objects. When a device receives only part of a radio signal, its response depends on various factors. In some devices, a weak signal may lead to lower volume or "static" – a type of chaotic noise. For others, if the signal is weak or interrupted, the information being transmitted may need to be resent, making the connection feel slower. Many digital devices require a complete "packet" of information to function correctly.
Humans can also block and redirect EM
Human bodies absorb EM radiation and can even act as antennas. Communication devices typically use "non-ionizing" wavelengths, meaning they don't damage cell structures or DNA. However, EM radiation from phones and other devices can sometimes cause localized warming of body tissues – similar to how microwave ovens work. Scientists continue to research the potential effects of various types and amounts of EM radiation on humans.

MAKING WAVES

with radio

Learn

about radio

What is radio?

Electromagnetic radiation is around us at all times

Electromagnetic radiation in everyday life

Radio waves are different lengths

Waves carry other waves

Digital Modulation

Radio communication relies on systems made up of many technologies

How did the data center find James?

The path differs for each kind of device

Each band of the radio spectrum has advantages and limitations

Wider is faster

Buildings, weather and natural landscapes can interfere with EM communication

What is happening when waves are blocked or weakened?

Humans can also block and redirect EM