Week #12
A wave is a disturbance that transfers energy from one point to another without the movement of matter between said points. Think of a wave in the ocean: while the wave travels, the water itself doesn’t move across the ocean but rather it rises and falls as the wave passes through it. Waves have specific properties:
Wavelength: The distance between two consecutive peaks in the wave.
Frequency: How many wave cycles pass a point in one second, measured in Hertz (Hz). As the wavelength increases, the frequency decreases, and vice versa.
Amplitude: The height of the wave, which indicates its energy level.
Speed: How fast the wave travels, determined by its medium and type.
Electromagnetic waves are a type of wave that doesn’t need a medium (like air or water) to travel—they can move through the vacuum of space. These waves are produced when electric and magnetic fields oscillate together at right angles to each other in the direction of wave travel. This interaction between an electric wave and a magnetic wave is why they’re called electromagnetic waves. They differ from sound waves or ocean waves because they consist of energy, not a physical substance. While sound waves must have a medium to travel through (such as air or water — sound is vibrations in matter), EM waves are able to travel through the atmosphere, as well as over long distances, which makes them ideal for communication and broadcasting.
Electromagnetic waves occur naturally (lightning, stars, and the sun) or can be created artificially (transmitters, antennas, and electronic devices). Depending on their wavelength and frequency, they can serve vastly different purposes, from cooking food in a microwave to enabling wireless communication. The energy of a radio wave decreases as the wavelength increases, which is why they are non-ionizing and generally safe for humans — they lack the energy required to remove tightly bound electrons so they can’t damage our cells by breaking their chemical bond (unlike X-rays or gamma rays, which are ionizing and can cause harm).
The electromagnetic spectrum represents the full range of all electromagnetic wave frequencies, from very low-energy waves with long wavelengths to extremely high-energy waves with short wavelengths.
It includes:
Radio waves, being on the low-energy end of the spectrum, have the longest wavelengths, and the lowest frequencies, ranging from about 1 millimeter to 100 kilometers, and below 300 GHz. This allows them to travel vast distances and to successfully penetrate obstacles like walls and infrastructure.
Beyond the tiny band of visible light, humans can’t directly sense any electromagnetic waves, even though we are constantly surrounded by them. This includes everything from the heat we feel from the sun’s infrared rays to the radio waves that our beloved mobile phones use for communication. Understanding the invisible world of electromagnetic radiation was one of the most significant achievements in science, laying the foundation for a lot of modern technology.
The theory of electromagnetic waves was first proposed by Scottish physicist James Clerk Maxwell in 1864. Maxwell's equations mathematically described the interplay between electric and magnetic fields and predicted that disturbances in these fields could travel through space as waves. This meant that light, heat, and radio waves were all manifestations of the same fundamental phenomenon—electromagnetic radiation. Maxwell’s work unified the fields of electricity, magnetism, and optics into a single framework, showing that electromagnetic waves could exist at any frequency, not just those visible to humans.
It wasn’t until over two decades later, in 1887, that Heinrich Hertz provided experimental proof of Maxwell’s predictions. Hertz constructed an apparatus that could generate and detect electromagnetic waves, confirming their existence. His experiments demonstrated that these waves behaved as predicted—they could reflect, refract, and interfere, much like visible light. Hertz's discovery was groundbreaking because it transformed Maxwell’s abstract theory into observable reality. However, Hertz himself referred to the practical applications of his work as “of no use,” unaware that it would become the backbone of modern communication systems.
The discovery of radio waves and their practical use began with these foundational breakthroughs. Building on Hertz’s experiments, inventors like Nikola Tesla and Guglielmo Marconi explored how electromagnetic waves could transmit information across distances. In 1895, Marconi successfully transmitted wireless signals over a mile, marking the birth of modern wireless communication. In 1901, Marconi successfully received the first transatlantic radio signal. This took place on December 12 at Signal Hill in Newfoundland, Canada. Using a kite to lift a wire antenna and a telephone receiver as part of his apparatus, Marconi detected Morse code for the letter "S," sent from Poldhu in Cornwall, England. This accomplishment demonstrated that radio waves could travel beyond the Earth's horizon, opening the door to global wireless communication.
Marconi's work at the time faced numerous challenges. Strong winds repeatedly broke his kites, and earlier, storms had destroyed the large antennas at the transmission and reception stations. Nevertheless, his success marked a pivotal moment in science and technology. Marconi’s experiments started a rapid technological revolution, where engineers were working on better antenna design, which enhanced transmission and reception of radio signals; researchers explored different frequencies and discovered which were useful for different purposes such as navigation, military communication, and later, broadcasting; and the ionosphere was discovered, and later played a central role in enabling long-distance communication.
By the early 20th century, Marconi’s technology was being implemented on ships, revolutionizing maritime safety protocols. This proved crucial during the Titanic disaster in 1912, where wireless distress signals enabled rescue operations, saving many people’s lives. By World War I, radio communication was being rapidly adopted, and mostly used for coordinating troop movement and intelligence operations. By the 1920’s the radio in its familiar device form became a household fixture, revolutionizing how people consumed news, music, and entertainment.
The ability to send wireless signals across vast distances laid the groundwork for commercial radio networks, eventually leading to the rise of telecommunications giants. And so once radio technology became widely used, it became clear that without regulation, the radio spectrum—a finite resource—could be essentially over-flooded and rendered useless. The electromagnetic spectrum's radio frequencies, like lanes on a highway through which traffic goes, needed oversight (like traffic lights) to prevent interference between competing signals and ensure efficient use.
In the U.S., regulation began with the Radio Act of 1912, spurred by the Titanic disaster. The act mandated that all radio operators be licensed and that certain frequencies be reserved for specific uses, such as distress signals. This marked the first step in formalizing spectrum management.
As radio grew in popularity for broadcasting and commercial purposes, the Radio Act of 1927 established the Federal Radio Commission (FRC). The FRC allocated specific frequency bands to different users, such as broadcasters, government services, and maritime communications. The guiding principle was that the airwaves are a public resource and should serve the “public interest, convenience, and necessity.”
In 1934, the Communications Act replaced the FRC with the Federal Communications Commission (FCC), giving the FCC authority over all wireless and wired communications. The FCC remains responsible for spectrum allocation in the U.S. today. The National Telecommunications and Information Administration (NTIA) oversees spectrum usage by federal government agencies, including the military, weather services, and NASA.
The electromagnetic spectrum is divided into bands, each with a specific frequency range and designated purpose. These bands are classified by their frequency range (measured in Hertz, Hz) and are typically identified by their corresponding wavelength. Following are a few examples of major radio bands, along with their applications:
Primarily used for long-distance communication, especially maritime and aviation communication. In the past, LF was used for AM radio broadcasting, though this is now largely replaced by higher frequencies.
Used for AM Radio Broadcasting (530 kHz to 1700 kHz). This band is the one most people are familiar with when they tune into AM radio stations.
Long-range communication, including international broadcasting and military communication. Used for shortwave radio, where signals can bounce off the ionosphere, allowing communication over long distances (e.g., between continents).
Used for FM Radio Broadcasting (88 MHz to 108 MHz), which is the most common band for commercial radio stations; Television broadcast signals (channels 2-13 in the U.S.); Two-way radio communications for aviation, maritime, and public safety organizations.
Used for television broadcasting (channels 14-69 in the U.S., now being repurposed for mobile broadband and other technologies); Mobile Phones (e.g., 3G, 4G networks); Wi-Fi and Bluetooth operate in parts of the UHF band, particularly between 2.4 GHz and 5 GHz.
Used for satellite Communication (often using the 12 GHz to 18 GHz range); Radar systems and point-to-point communication; Some high-speed wireless communications like Wi-Fi (specifically, the 5 GHz band).
High-bandwidth, high-speed communication systems, including emerging 5G technologies. Also used in radio astronomy and experimental scientific applications.
Each of these bands is allocated and regulated to prevent interference. The FCC in the U.S., along with the NTIA, plays a critical role in ensuring that the spectrum is divided up in a way that maximizes its utility while minimizing conflicts between different services. For instance, radio broadcasters are assigned specific frequencies to ensure they do not overlap, and mobile operators are given access to portions of the spectrum to support cellular networks.
In addition to these allocated frequencies, there are also unlicensed bands (such as the ISM bands for Wi-Fi and Bluetooth), where devices can operate without specific licenses, as long as they comply with power limits and other restrictions to avoid interference with licensed services.
While the regulatory framework has evolved significantly since its inception, several challenges persist in modern spectrum management:
Spectrum Scarcity and Inefficient Use: Despite technological advances, certain portions of the spectrum remain underutilized while others are congested. A 2012 President's Council of Advisors on Science and Technology (PCAST) report found that in many frequency bands, actual use of allocated spectrum was only 20% or less. This inefficiency stems partly from traditional "command-and-control" licensing approaches that can be inflexible in responding to changing needs and technologies.
Licensing Process and Costs: Obtaining spectrum licenses can be complex and expensive. The FCC primarily uses spectrum auctions for commercial allocations, which can result in billions of dollars in bids. For example, the C-band spectrum auction in 2021 generated over $81 billion in bids. While this system ensures market-based allocation, it can create barriers for smaller companies and innovators.
International Coordination: Spectrum management requires significant international cooperation, as radio waves don't respect national boundaries… The International Telecommunication Union (ITU) coordinates global spectrum use, but conflicts still arise. For instance, there are ongoing debates about spectrum allocation for 5G networks, with different countries adopting varying approaches to frequency allocation.
To me, the story of radio waves represents one of humanity's most transformative discoveries. From Maxwell's theoretical work to Hertz's experiments, and from Marconi's first transatlantic signal to today's complex web of wireless communications, our understanding and use of radio waves has revolutionized how we live, work, and connect. As we push into new frontiers with technologies like IoT devices, 5G, quantum communication, and beyond — the management and allocation of the radio spectrum becomes increasingly critical. The finite nature of this resource requires innovative solutions, from dynamic spectrum access to artificial intelligence-driven allocation systems. Yet despite these challenges, radio waves remain at the heart of our connected world, enabling everything from space exploration to the simple act of checking the time on our phones. As we look to the future, our relationship with radio waves will continue to evolve, driving new technological breakthroughs and reshaping our understanding of what's possible, and what’s out there, all around us.
Radio wave | Encyclopedia Britannica
The electromagnetic spectrum | Encyclopedia Britannica
How Heinrich Hertz Discovered Radio Waves | Famous Scientists
The history of radio technology | ThoughtCo
Milestones:Reception of Transatlantic Radio Signals, 1901 | ETHW
Radio Spectrum Allocation | Federal Communications Commission
FCC online table of frequency allocation
Who regulates the spectrum | National Telecommunications and Information Administration
The National Telecommunications and Information Administration (NTIA): Current Roles and Programs
Radio regulations | the International Telecommunication Union
This is well beyond the scope of this explainer, but to anyone who's interested — there's a lot of really interesting readings about radio as art. These are just some I had on hand:
Radical Radio by R. Murray Schafer
Take it to the air: Radio as public art by Sarah Kanouse
Transmission Arts: The Air That Surrounds Us by Galen Joseph-Hunter
