FM and AM meaning

FM and AM meaning

FM and AM meaning; AM stands for amplitude modulation while FM stands for frequency modulation.  Frequency modulation and amplitude modulation are the only two ways that radio signals are transmitted.

How radio works

Before discussing FM and AM meaning, we will described some terms.  We will discuss what is radio and how the engineers coined the world along the years.

What is radio

Today, when we talk about radio, we refer to the FM/AM devices that we use to listen to news, programs and we also use it to listen to music and other audio files. However, radio also refers to the type of wave through which the information is transmitted through.  You might be surprised to realize that these waves are used in more than  FM/AM radios. For starters, it is the same waves that are used to transmit voices for wireless television waves, phone calls, and messages among others. FM and AM meaning

Transmitters and receivers

The device you would use to transmit this type of wave is called a transmitter.  The radio waves are transmitted through the air from one location to another. Now, you need a receiver to convert the waves into sound waves. Antennae also called aerial is needed to receive the radio waves.

FM and AM meaning

An AM/FM receiver

You might be wondering how you get to listen to a specific station after you tune to that frequency. Well, your radio has a variable capacitor that allows your aerial to receive specific frequencies at any given moment when you tune.

Electromagnetic waves

Radio waves are electromagnetic waves and they have speed, frequency, and wavelength. The speed simply means how fast waves travel from one location to another. The wavelength, on the other hand, is the distance between two successive crest or troughs. What are crest and troughs you ask? You see electromagnetic waves resemble a sine curve and so the topmost part of the sine wave is called crest while the bottom-most part is called the trough. The frequency of a wave refers to the number of complete cycles per second. It is measure in Hertz. If you have 40 cycles per second, it is said to be 40 Hertz.

The wavelength of radio waves is several hundred meters and are several hundreds of thousands Hertz.  This is why you get to listen to radios and watch tv live events in real-time. FM and AM meaning

Evolution of the term radio

The term radio came to be a few years after it was invented. It will interest you to find out that people used to refer to radio waves using other terms such as the Hertzian wave, ether waves, and electric waves. The Nikolas tesla when he files his patent, he named it the wireless telegraphy. A French inventor is credited for using the term radio for the first time when he invented a cohere detector and named it radio conductor.

Development of radio waves

The first device to detect radio waves was developed in 1983 by a man named Edouard Branly. Like all other inventors of his time, he named his invention a radio conductor. In your research, you might find other people referring to it as coherer.

The first idea of wireless communication was under development as early as 1830. This was when Maxwell clerk James  demonstrated that it is possible to propagate electromagnetic waves through the air.

History of radio

You may not know this but the first radio message was sent in the year 1894 by Sir Oliver Lodge. The problem of radio interference was solved in the year 1903. It is an accomplishment accredited to  an American physicist called John stone. It was only until 1906 that voices were transmitted via radio waves. A Canadian named Reginald Fessenden made this discovery. The message was sent 11 miles into the Atlantic Ocean.  The same year, the triode valve was engineered by Lee De Forest. The radio became smaller and very practical.

And the televisions you ask? In the 1920s, the technology of radio waves evolved into television. Transistors were later invented in 1947. Transistors made the radio circuitry became more compact.  The discovery was made in the Bell labs.  Commercial radios based on transistors were sold in the year 1954 for the first time.

A telephone-based on radio waves was developed in 1973.  Later the wi-fi was developed as a way of connecting computers wireless via radio waves. Bluetooth came into the market only in the year 1998.  It’s a short-range communication protocol.

Nikola Tesla is the man credited with the development of the original radio. However, in the year 1909, Guglielmo Marconi wrongfully received a noble peace prize in physics for inventing the radio. It is only after his death that the real inventor received the credit. While Guglielmo Marconi thought he invented the radio, Tesla had filed a patent on radio technology like three years earlier. He had named it world telegraphy.

Analog radio

You remember we said that electromagnetic waves travel like sine curves. The voice, images, or information signal is added to the radio wave. The radio wave is referred to as a carrier signal. This is a process that is called modulation. Now, when your radio receives the signal, it cancels out the carrier signal and it remains with the signal that was added to the carrier signal.

There are two ways you can perform signal modulation, frequency modulation, and amplitude modulation.  When you perform modulation by causing fluctuation on the carrier frequency, the process is called frequency modulation. This is how FM radio stations operate If the modulation process causes the amplitude of the wave to change, this type of modulation is referred to as amplitude modulation.  This is how AM radios station operate.

How analog radio works

Difference between AM and FM


How radio waves are turned into sound waves

When your radio receives either the FM or the AM signals, it uses the circuitry inside to change the signal into copies of the original sound. The circuitries are called detector circuits while the process of changing the signal into coherent sound waves is called the demodulation process.

How Digital radio works

Digital radio is also called digital audio broadcasting. Like the AM and FM radios, digital radios also use radio waves to transmit signals. However, digital uses a method that compresses the information sent by use of MPEG. The information is broken down into ones and zeros and then it is transmitted. This is done using the COFDM ns multiplexing technology to ensure the information is transmitted reliably and received robustly. The signals are not prone to interference.  Digital radios are a more efficient method to broadcast over the airwaves.

How  Online radio works

This works in the simplest way possible. You do not need any other equipment other than the microphone, a laptop, and a mixer. Then, you will need a cloud service provider such as the who will handle the rest of the things. This is the easiest and fastest way to get on the air in just minutes.

In most countries, there is little to no regulation when it comes to online radios. You should check before you start your broadcasting. But before you play any music that is not yours, please look for licensing. More people are willing to listen to online radios than you might think.

Other applications of radio waves.

Radio broadcasting

Radio broadcasting means transmitting audio signals to the public audience who have radio receivers. AM broadcasting was done in 1920 but the FM broadcasting was started in the 1930s. most of the radio receiver devices you have had can receive both AM and FM signals. AM broadcasting transmit using frequencies as low as 148 kHz to as high as 1.71MHz. Amplitude modulation waves have low fidelity but can travel beyond the horizon.  Shortwaves broadcasting is a version of AM broadcasting that allows waves to travel beyond the continent because the waves can be reflected by the ionosphere.

Frequency modulation is better than AM broadcasting.  The waves have a frequency that varies between 65 MHz to 108 MHz. however, FM waves can only be transmitted between 48-64  km. it is possible to block FM waves using buildings, hills among other big objects.

Satellite radio is a form of radio broadcasting that has high-quality audio transmitted to receivers on earth using microwave downlink signals. The signal is transmitted directly from a satellite that is located 22000 miles above the earth.

Digital Radio Mondiale (DRM)  is another form of digital broadcasting. It was developed to replace the legacy AM and FM broadcasting. It is a recent discovery since it was developed in the year 2001. Digital Radio mondiale  is now available in more than 20 countries.  The two modes used for this transmission are DRM30 mode and DRM+. The former uses AM broadcast bands that are below 30 MHz while the latter uses VHF frequencies.

Television broadcasting

In my previous article on how how modern LCD display tv works, we saw how the device produces the image that you see. However, here we are going to look into how the video signals are broadcasted from the station. Television broadcasting uses radio waves to transmit video and sound signals to television sets. TV signals occupy a wider bandwidth. The analog signals require frequencies as low as 6 MHz. however, since the last decade, you now be using the digital format referred to as high definition television (HDTV). The images are transmitted at 30 fps and in 1080 p resolution. The digital television transmission system uses digital modulations such as 8VSB and OFDM.  The transmission system also uses image compression besides the  8VSB and OFDM.

There are two types of television, satellite television, and terrestrial television.  The former uses signals that are broadcast direct from a satellite while the terrestrial television has land-based tv stations that transmit signals. Terrestrial televisions use frequency bands between 41 MHz and 88MHz. frequency boundaries vary from one country to another.


This is the application of radio waves for navigation or to locate objects. This is the technology that is used by smartphones, car trackers, and sometimes your pc. GPS is maintained by the US military and makes use of more than 30 satellites that orbit the earth. The satellites are located in the low earth orbit.  Using GPS, it is possible to calculate the longitude and latitude of an object at any given moment.

FM and AM meaning
Radio triangulation use for radiolocation

Other than GPS, there are radio beacons that are located in fixed places on the earth’s surface and transmit signals continuously. This is used by ships and aircraft for navigation. There is one beacon that is known as a very high frequency omnidirectional range (VOR) which is a worldwide radio navigation for the aircraft.  The beacons are located on the ground and transmit on frequencies between 108 MHz and 117.95 MHz. The VOR transmits two signals at the same time. The difference between the two signals gives the bearing from the transmitting station. It is also possible to calculate the distance from them because. FM and AM meaning

Radio jamming

Before we finish on FM and AM meaning, there is one last thing, radio jamming. It is possible to suppress signals or what you know as radio jamming.  You can  achieve this by broadcasting radio signals that interfere with the reception of other signals.  It is applied in the military. Some countries use this technique to prevent their citizens from receiving any broadcast from neighboring countries.  If you want to jam a signal,  you would need a very strong transmitter that would emit signals at the same frequency as the transmitter you are targeting.  However, you would transmit noise instead of sound, video, or anything sensible. FM and AM meaning