Radio Frequencies Explained: AM, FM, DAB, and Internet

April 5, 2026

Radio technology has evolved dramatically since the first wireless transmissions over a century ago. Today, listeners can access radio through AM, FM, DAB+, satellite, and internet streaming, each with its own strengths and limitations. Understanding how these different technologies work helps you appreciate why your favorite station sounds the way it does and why certain technologies are better suited to specific listening situations.

AM Radio (Amplitude Modulation)

AM radio is the oldest commercial broadcasting technology, dating back to the early 1920s. AM works by varying the amplitude (strength) of a carrier wave to encode audio information. The carrier frequencies used for AM broadcasting range from 530 kHz to 1700 kHz in most countries.

Advantages of AM

AM signals can travel long distances, especially at night when the ionosphere reflects medium-wave signals back to earth. A powerful AM station can be heard hundreds or even thousands of miles away after sunset. This long-range capability made AM the foundation of national and international broadcasting for decades. AM receivers are also simple and inexpensive to manufacture.

Limitations of AM

AM audio quality is relatively poor by modern standards. The narrow bandwidth of AM channels limits the frequency range of audio, producing a thinner, less detailed sound than FM. AM is also susceptible to electrical interference from motors, lighting, electronics, and atmospheric conditions like lightning, which produce the crackling and buzzing familiar to AM listeners.

AM Today

Despite its limitations, AM radio remains important for talk programming and news, where audio fidelity is less critical than reach. AM sports broadcasting, particularly baseball in the United States, has a devoted following. Some countries are considering phasing out AM broadcasting, while others are investing in HD Radio or DRM (Digital Radio Mondiale) to modernize the AM band with digital audio quality.

FM Radio (Frequency Modulation)

FM radio, developed in the 1930s and widely adopted in the 1960s and 1970s, represents a major improvement over AM in audio quality. FM works by varying the frequency of a carrier wave rather than its amplitude. FM broadcasting operates in the 87.5 MHz to 108 MHz band in most countries.

Advantages of FM

FM delivers much higher audio quality than AM, with a wider frequency range that captures the full spectrum of music. Stereo broadcasting, standard on FM since the 1960s, creates a spatial listening experience that AM cannot match. FM is also more resistant to electrical interference than AM, producing a cleaner, more consistent signal.

Limitations of FM

FM signals travel in straight lines and are limited by the horizon, typically providing coverage of 30 to 60 miles from the transmitter depending on terrain and power. Mountains, tall buildings, and other obstacles can block FM signals, creating dead spots. This line-of-sight limitation means FM is inherently a local medium, which is why each city has its own FM stations rather than hearing national broadcasts.

FM Today

FM remains the dominant radio platform worldwide. The vast majority of radio listening in most countries occurs on FM, and the technology's combination of decent audio quality, reliable coverage, and simple receiver requirements ensures its continued relevance. Some countries are transitioning to DAB+ while others are investing in FM infrastructure for years to come.

DAB and DAB+ (Digital Audio Broadcasting)

DAB is a digital radio technology that transmits audio as digital data rather than analog signals. DAB+ is the improved version using more efficient audio compression, delivering better sound quality in less bandwidth. DAB+ is used in Europe, Australia, and parts of Asia.

Advantages of DAB+

DAB+ offers several benefits over FM. It can carry more stations in the same bandwidth, giving listeners more choice. It provides consistent audio quality without the fading and interference that affect FM. DAB+ receivers display text information including station name, track title, and artist. And the digital signal either works clearly or not at all, eliminating the gradual degradation that FM experiences at the edge of coverage.

Limitations of DAB+

DAB+ requires new receivers, which can be an adoption barrier. Coverage can be less robust than FM in some areas, particularly indoors and in hilly terrain. The "digital cliff" effect means that when signal strength drops below a threshold, the audio cuts out completely rather than gradually fading as FM does. And while more stations can fit in the bandwidth, the audio quality of each station depends on the bit rate allocated to it, and some broadcasters have used low bit rates that actually sound worse than FM.

DAB+ Adoption

Norway became the first country to switch off national FM broadcasting in favor of DAB+ in 2017. The UK, Germany, Netherlands, and Australia have significant DAB+ adoption. However, many countries, including the United States, have not adopted DAB+ and have no plans to do so. The future of radio may involve DAB+ in some markets while others maintain FM or transition directly to internet-based delivery.

Satellite Radio

Satellite radio uses communications satellites to deliver radio signals covering entire continents. SiriusXM in North America is the primary commercial satellite radio service, offering hundreds of channels across music, talk, sports, and entertainment. Satellite radio requires a subscription and specialized receiver but provides nationwide coverage with consistent quality, making it popular for road trips across large countries.

Internet Radio (Streaming)

Internet radio delivers audio content over the internet, either as live streams of traditional radio stations or as internet-only stations. This technology has transformed radio from a local medium into a global one.

Advantages of Internet Radio

Internet radio offers effectively unlimited choice. With RadioGlob, you can listen to stations from any country in the world. Audio quality can be excellent, with many stations streaming at high bit rates that match or exceed FM quality. There is no geographic limitation; a station in Tokyo sounds exactly the same whether you listen from Tokyo or Toronto. And internet radio stations can provide additional content including song information, album art, links, and on-demand listening.

Limitations of Internet Radio

Internet radio requires an internet connection, which means it depends on infrastructure that may not be available during emergencies or in remote areas. Streaming uses data, which can be costly on metered mobile connections. There is a slight delay (latency) compared to live broadcast radio. And the reliance on internet infrastructure introduces privacy considerations, as online listening can be tracked in ways that traditional radio listening cannot.

HD Radio

HD Radio is a digital technology used primarily in the United States that broadcasts digital audio alongside traditional AM and FM signals on the same frequencies. It offers improved audio quality and allows stations to broadcast additional subchannels. HD Radio requires compatible receivers but is free to listen to, like traditional broadcast radio.

Choosing Your Listening Method

Each radio technology serves different needs. FM remains the most practical for local listening and in-car reception. AM offers long-distance reception and talk programming. DAB+ provides digital quality and more stations in supported markets. Satellite radio covers vast geographic areas. And internet radio offers global access to any station worldwide. For the widest selection and easiest exploration of global radio, internet streaming through RadioGlob is the ideal starting point. For more on the technology behind international broadcasting, see our shortwave radio guide.