FM broadcasting

FM radio sends music to you through the air.

An engineer named Edwin Armstrong made a special kind of FM. It helps music sound very clear. This type of radio has less popping sounds.

It does not have much static noise. Most music uses this way to play. However, the sound does not travel as far.

It is a great way to listen to songs!

FM radio is a way to send sound through the air.

It uses a method called frequency modulation. This is also known as FM. In FM, the radio signal changes its frequency to carry sound. This is different from AM radio. AM radio changes the strength of the signal instead.

An engineer named Edwin Armstrong invented wide-band FM.

This invention helps music sound very clear. It has high fidelity. This means the sound is a very accurate copy of the original. FM is also good at fighting static. Static is the popping or hissing noise you might hear.

One test showed that FM stayed clear even with a huge spark nearby.

FM stations use very high frequencies. Most of the world uses the band from 87.0 to 108.0 MHz. This is part of the VHF range.

Because FM uses more space in the air, it cannot travel as far as AM. However, it is the best way to listen to music.

FM broadcasting is a special way to send sound through the air.

It uses a method called frequency modulation, or FM for short. This method changes the frequency of a carrier wave to carry information. This is different from AM radio, which changes the signal's strength instead. FM is great for music because it offers high fidelity. High fidelity means the sound is a very accurate copy of the original program.

Because it is so clear, it is used for most music and audio broadcasts.

How does FM work so well? In FM, the frequency of the wave changes based on the sound input.

This makes the signal very good at fighting off noise. Most interference shows up as changes in signal strength, which is called amplitude noise. Because FM does not rely on strength to carry sound, it can ignore much of this static.

Engineers even use a trick called pre-emphasis to help. They boost high sounds before sending them. Then, the radio receiver uses de-emphasis to lower them back down. This helps keep the high sounds clear and free from popping noises.

People have been working on this for a long time. In November 1919, Hans Idzerda began broadcasts in the Netherlands. He used a type of narrow-band FM at station PCGG. Later, an American engineer named Edwin Armstrong changed everything. In 1933, he invented wide-band FM, which is what we use today.

He even did secret tests from the Empire State Building in New York City. His station was called W2XDG and used a power of 2 kW. These early steps helped make modern radio possible.

FM stations use specific parts of the radio spectrum. Most of the world uses the band from 87.0 to 108.0 MHz. This is part of the VHF range.

Different places use different rules for their frequencies. In Japan, the band is 76 to 95 MHz. In the former Soviet republics, an older band from 65.8 to 74 MHz is used. In Brazil, stations used the 88 to 108 MHz band until the late 2010s. Many countries also use specific multiples of 100 kHz to set their stations. This helps keep the signals from bumping into each other.

You might also enjoy listening to music in stereo.

Stereo means you hear different sounds in the left and right speakers. Edwin Armstrong was the first to experiment with sending many signals at once. In the late 1950s, many groups tried to find the best way to do stereo. These groups included names like Zenith and General Electric. In April 1961, the FCC approved the GE and Zenith systems. These became the standard for stereo FM in the United States. This system was designed so that even old mono radios could still hear the music.

FM broadcasting is a sophisticated method used to transmit audio signals via radio waves. It utilizes a process called frequency modulation, or FM, to encode information. In this system, the frequency of a carrier wave is varied to represent the input sound. This differs from Amplitude Modulation, or AM, which changes the signal's strength instead.

Because of this method, FM provides higher fidelity than AM. High fidelity means the sound is an extremely accurate reproduction of the original program. Consequently, FM is the preferred choice for broadcasting music and general audio.

The mechanism of FM relies on how the carrier wave responds to audio input. The frequency deviation of the carrier is directly proportional to the amplitude of the audio signal. This means as the sound gets louder, the frequency shifts more significantly.

This approach makes FM much more resistant to amplitude noise. Most interference, such as static, affects the signal's strength rather than its frequency. Because the information is carried in the frequency, the receiver can ignore these strength changes. In wideband FM, devices called limiters help restore a constant signal envelope. This process effectively rejects most amplitude variations caused by interference.

To combat specific types of noise, engineers use a technique called pre-emphasis and de-emphasis. In FM systems, random noise tends to be stronger at higher audio frequencies. To fix this, the transmitter uses pre-emphasis to boost high frequencies before they are sent.

When the signal reaches the receiver, a process called de-emphasis reduces those high frequencies back to their original levels. This reduces the level of high-frequency noise relative to the recovered signal. This method was originally described by Edwin Armstrong to improve the signal-to-noise ratio. However, modern music with much more high-frequency energy can sometimes make this process difficult. To prevent excessive frequency deviation, modern systems use modulation control devices.

FM broadcasting occupies the Very High Frequency (VHF) portion of the radio spectrum. Most of the world uses a broadcast band between 87.0 and 108.0 MHz. This is often called the CCIR band.

Different regions follow different rules for their frequency allocations. In Japan, the band is 76 to 95 MHz. Some former Soviet republics still use the older OIRT band from 65.8 to 74 MHz. Brazil recently expanded its band to include 76 to 88 MHz following the phase-out of analog television. Stations are assigned frequencies at specific intervals, usually 30 kHz apart. To prevent inter-channel interference, stations near each other often maintain a 500 kHz separation.

The history of FM is marked by several key scientific milestones. Hans Idzerda began early broadcasts in the Netherlands in November 1919 using narrow-band FM. However, the modern era of FM was shaped by American engineer Edwin Armstrong. In 1933, Armstrong invented wide-band FM, which allowed for much higher sound quality.

Between 1934 and 1935, he conducted secret tests using an experimental station called W2XDG. This station was located in the Empire State Building in New York City. It transmitted at 41 MHz with a power of 2 kW. Armstrong's work proved that wide-band FM could provide much greater immunity to noise than AM.

Stereo FM was a major advancement that allowed for two-channel audio. Armstrong was a pioneer in this field, experimenting with multiplexing as early as 1934. He used subcarriers to send different types of information alongside a main program.

In the late 1950s, the FCC evaluated many different systems to standardize stereo. These tests took place in Uniontown, Pennsylvania, using the KDKA-FM station. Several companies, including Zenith and General Electric, proposed different methods. In April 1961, the FCC officially approved the GE and Zenith systems. These systems were chosen because they were compatible with existing mono receivers. This ensures that a person with an old mono radio can still listen to a stereo broadcast.

FM broadcasting remains a vital part of global communication systems. It requires more bandwidth than AM, which is why it uses higher-frequency bands. The maximum frequency deviation for a stereo broadcast is typically ±75 kHz. In some monophonic broadcasts, this value might be lower, such as ±50 kHz. Because FM provides such high-quality sound, it connects listeners to a wide range of musical and spoken content. The science of frequency modulation continues to be a foundation for how we experience audio through the airwaves.