FM broadcasting

FM broadcasting is a method of radio broadcasting using frequency modulation. Invented by Edwin Howard Armstrong in 1933, it provides high-fidelity sound over VHF radio waves, significantly reducing static and interference compared to AM broadcasting. The technology was adopted for commercial use in the United States following approval by the Federal Communications Commission and became the dominant medium for music radio.

History

The development of this technology was pioneered by Edwin Howard Armstrong, who conducted his first major demonstration for the RCA at the Alpine, New Jersey station in 1935. Despite initial resistance from established AM networks and David Sarnoff of NBC, Armstrong persisted, building his own station, W2XMN in Alpine, New Jersey. The Federal Communications Commission began authorizing commercial stations in 1941, with the first being W47NV in Nashville, Tennessee. Post-World War II, the band expanded, and the rollout was accelerated by the Zenith Radio Corporation's victory in a key regulatory case. The format's superior sound quality fueled the rise of Top 40 and album-oriented rock formats on stations like WABC and WMMR.

Technical characteristics

This system operates within the VHF band, specifically between 87.5 and 108.0 MHz in most of the world, as defined by the International Telecommunication Union. The process involves varying the frequency of the carrier wave in proportion to the audio signal. Key technical features include a wider bandwidth than AM broadcasting, typically 200 kHz, which allows for high-fidelity audio and the potential for stereophonic sound. The capture effect helps the receiver lock onto the strongest signal, minimizing co-channel interference. Transmission relies on complex transmitter and antenna systems, often located on structures like the Empire State Building or Sutro Tower.

FM broadcasting around the world

Adoption and band plans vary globally under the oversight of the International Telecommunication Union. In the Americas and most of Asia, the 87.5–108.0 MHz band is standard, as used by major broadcasters like the BBC in the United Kingdom and NHK in Japan. Some nations, like those in Eastern Europe, historically used the OIRT band of 65.8–74.0 MHz. In Brazil, stations like Rádio Globo dominate, while in Germany, public broadcasters like ARD share the band with private networks. The rollout in India was accelerated by initiatives like Radio City.

Advantages and disadvantages

Primary advantages include high-fidelity, static-free audio quality, which is ideal for music radio, and resistance to signal-to-noise ratio degradation. The technology also supports additional subcarrier services without affecting the main audio. Disadvantages consist of a limited broadcast range, typically under 100 kilometers, due to VHF propagation characteristics, making it less suitable for wide-area coverage than AM broadcasting. Signals are also more susceptible to blockage by terrain and large structures like the Rocky Mountains, and require more complex and expensive receivers.

Subcarrier services

The bandwidth allows for the transmission of additional signals on subcarriers outside the audible range. These services include RDS, which provides station identification, traffic announcements, and alternate frequencies, widely used in Europe. SCA channels in the United States have been used for Muzak, reading services for the visually impaired, and utility telemetry. Digital subcarriers can also transmit data for paging systems or stock tickers from services like Bloomberg L.P..

Future and digital transition

The future is shaped by the transition to digital radio standards. In the United States and several other countries, HD Radio allows digital and analog signals to be broadcast simultaneously. In much of Europe, Asia, and Australia, the DAB+ standard is being adopted, with countries like Norway and the United Kingdom having begun sunsets for analog transmissions. Hybrid systems and the growth of internet radio and streaming media from platforms like Spotify present both competition and complementary distribution paths for traditional broadcasters.

Category:Radio communications Category:Broadcasting