How far do radio waves travel?

You’ve probably experienced signal loss from an AM or FM radio station while traveling from one city to another. But do you know why this phenomenon occurs?

If you’re curious, follow our post to understand how far radio waves travel, their characteristics, limitations, and to learn some other interesting facts about the world of radio.

History of radio waves

Before we talk about the distance that radio waves can travel, it’s important to know the history of their discovery and the invention of the machines that allow humans to make use of this phenomenon. For that, let’s go back two centuries and talk about some great names in science!

James Clerk Maxwell was responsible for creating the modern theory of electromagnetism. To summarize Maxwell’s incredible work, he proved on paper, in 1865, the existence of electromagnetic waves and, consequently, radio waves.

Heinrich Hertz, using the theories created by Maxwell, demonstrated in practice that electromagnetic waves existed. In his laboratory, Hertz built a machine that generated a spark. This spark, in turn, generated an electromagnetic disturbance that propagated through the air and was captured by another part of his experiment. In short, Hertz built a transmitter and receiver of electromagnetic waves! The date? November 29, 1888.

A few years later, during the 1890s, Guglielmo Marconi invented wireless telegraphy. Building upon Hertz’s machine, Marconi managed to transmit telegraph signals through the air! First, for only 9 meters. Gradually, he improved his invention until, in 1901, he successfully transmitted a wireless telegraph signal across the Atlantic Ocean for over 3,000 kilometers.

From there, great names further developed the technology theorized by Maxwell and proven by Hertz. Guglielmo Marconi, Nikola Tesla, Thomas Edison, and the Brazilian inventor Roberto Landell de Moura were responsible for advancing Hertz’s invention and transforming the simple transmitter-receiver into a technology capable of revolutionizing the world.

The distance radio waves travel

Radio waves, as we mentioned, are vibrations in the electromagnetic spectrum. Therefore, they move at the speed of light, an incredible 300,000 kilometers per second! To understand how far radio waves can travel, we need to understand some characteristics of this phenomenon.

Characteristics of radio waves

Radio waves have characteristics that determine the transmission power, identification, position in the radio spectrum, and speed of wave movement. Here’s a brief overview of each characteristic:

Amplitude: It measures the intensity of the wave. It is the maximum distance between the crest (highest point) and the trough (lowest point) of the wave. The amplitude of a radio wave determines its transmission power, meaning the wider the wave, the farther it can be transmitted.

Wavelength: It is the distance between two consecutive crests of the wave. It can be measured in meters or other units of length. The wavelength is directly related to the frequency of the wave.

Frequency: It measures how many times the wave completes a cycle per second. It is measured in Hertz (Hz). Electromagnetic waves are categorized by their frequency. Visible light, microwaves, X-rays, and radio waves are examples of different types of electromagnetic waves.

Radio waves are characterized by having very short frequencies, much smaller than visible light. In the case of electromagnetic vibrations, the lower the frequency, the larger the size of the wave. And the larger the size of a radio wave, the farther it can travel without being affected by obstacles.

That’s why AM radio stations can travel farther away than FM radio stations! But we’ll talk more about that later on.

Limitations on the range of radio waves

In addition to characteristics such as amplitude, wavelength, and frequency, there are other factors to consider when it comes to the range of radio waves. Several factors can influence the distance that radio waves can travel. Here are some of them:

Transmitter power

The power of the transmitter is a critical factor in determining the distance that radio waves can travel. The higher the transmitter power, the farther the radio waves will travel. This is because the transmitter power determines the intensity of the radio wave. The stronger the radio wave, the farther it will travel.

However, it’s important to note that increasing the transmitter power does not automatically guarantee a longer transmission. Additionally, increasing the transmitter power can also cause issues such as interference with other radio transmissions.

Government regulations establish limits on the power of radio transmitters to ensure compatibility between various transmissions.


Interference is one of the main causes of loss of quality and distance in the propagation of radio waves. It can be caused by various factors, such as other radio transmissions, physical obstacles, electrical activity, or other types of electromagnetic pollution.

When it comes to AM and FM radios, the most common causes of interference are “pirate radios” that transmit on the same frequencies as licensed radios, thereby blocking their reception locally.

Government regulations establish standards to limit electromagnetic pollution and protect the quality of radio transmissions.

The influence of the atmosphere on the propagation of radio waves

The atmosphere has a significant influence on the range of radio waves. This is because waves travel through electromagnetic propagation, which is affected by various environmental factors such as air density, humidity, and temperature.

The atmospheric layer that has the greatest influence on the propagation of radio waves is the ionosphere. This layer is composed of ionized gases and is capable of reflecting and refracting waves at different altitudes. This ability allows radio waves to be sent over long distances. However, the ionosphere is a dynamic environment, and its properties can change depending on the time of day, season, and solar cycle. These changes can affect the range of radio waves that rely on the ionosphere for propagation.

Those who work at radio stations have encountered this phenomenon. It is common for the transmitter power of the station to be reduced at night when the ionosphere absorbs less and reflects the radio signal more.

In addition, humidity and temperature also influence the propagation of radio waves. The moisture in the air can absorb the waves, reducing their range. Temperature, on the other hand, affects the density of the air, and the lower the density, the greater the range of radio waves. Conversely, higher air density has a greater impact on radio waves. Attenuation is more pronounced at higher frequencies, which means that higher-frequency radio waves have a shorter range.

Another important factor to consider is the presence of physical obstacles such as buildings and mountains, which can block or attenuate radio waves, reducing their range. The larger the wavelength, the greater the ability to bend around obstacles and reach greater distances.

Use of radio waves

Anyone who thinks that radio waves are only used to listen to broadcast stations is mistaken. Radio waves are used for various purposes, such as military transmissions, satellite communications, amateur radio, television, among others. Here are some wave bands and their uses:

Shortwave (SW): Shortwave is used for long-distance transmissions, such as international radio, amateur radio, and military communications.

Medium wave (MW): In addition to AM radio station transmissions, medium waves are also used for maritime and aviation navigation, military communications, and car location and alarm systems.

Longwave (LW): In addition to AM radio station transmissions, long waves are also used for navigation and location systems, such as LORAN-C.

Very High Frequency (VHF): The VHF band is used for short and medium-distance communications, such as aviation radio, emergency communications, FM radio, and television.

Ultra High Frequency (UHF): The UHF band is used for short-distance communications, such as two-way radios, cell phones, digital television, and military communications.

These are just a few of the main radio wave bands, and each of them has its own characteristics and specific applications.

Differences between AM and FM transmission

When it comes to radio waves, it’s inevitable to think of AM and FM, isn’t it? Everyone has tuned their radio to an AM or FM station to listen to their favorite programming. So it’s time to learn more details about these bands.

AM radio waves (Amplitude Modulation) are characterized by the use of amplitude modulation to transmit audio signals and data through the airspace. Due to their lower frequency range, typically between 535 kHz and 1605 kHz, they are capable of propagating over long distances. Additionally, they can be received by simple and inexpensive receivers.

However, AM radio waves have some disadvantages. One of the main drawbacks is the limitation in audio quality. They are also more susceptible to electromagnetic interference and noise.

On the other hand, FM radio waves (Frequency Modulation) are characterized by the use of frequency modulation to transmit audio signals and data through the airspace.

One of the main advantages of FM radio waves is the high audio quality that can be achieved. This is because frequency modulation allows the signal amplitude to remain constant while the frequency is changed to carry the audio information. Additionally, FM has a wider bandwidth than AM, allowing it to transmit more data in a single radio wave.

However, FM radio waves also have some disadvantages. One of them is their limited propagation, as they use a higher frequency range, typically between 88 MHz and 108 MHz. This means that FM transmissions reach a smaller geographic area. Additionally, FM receivers are generally more expensive and complex.

Web radio as an alternative

With the popularization of the internet, the possibility arose to combine the broadcasting system with streaming technology to overcome the limitations of traditional communication.

Streaming technology allows audio content to be transmitted over the internet, eliminating the need for radio waves to reach the audience. It is sent through a network of servers and routers that connect users’ devices to the internet. This process is not affected by electromagnetic interference and has no geographic limitation.

By using audio compression algorithms like MP3, which can reduce the file size without significantly affecting sound quality, audio streaming is not subject to distortions, unlike analog radio broadcasts.

In addition to these benefits, it is a cost-effective and accessible technology for everyone.


Radio is a historic means of communication and holds a special place in the hearts of people all around the world. However, as we have shown here, radio waves have their limitations in terms of range, influenced by a combination of factors including frequency, transmitter power, interference from physical obstacles, and weather conditions.

Therefore, streaming technology can be an effective alternative to expand the reach of radio stations, allowing people from different parts of the world to access content instantly and without interference.

BRLOGIC is a leading provider of audio streaming services. If you want to bring your station to the internet so that more people can listen to it, visit our website and discover the advantages.

About the author

Luiz Silveira

Luiz Silveira is a specialist in digital marketing and a radio, music and technology enthusiast. With a decade of experience, he aims to help radio stations better position thenselves on the internet.

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