How does AM Radio Work?

Amplitude Modulation radios are not only a source of entertainment through various talk shows and music stations, but also serve as a two-way communication tool. It’s quite fascinating how this broadcasting service works through a process of radio wave creation and modulation. If you are wondering about how does AM radio work, you are in the right place. This article explains the details regarding the functioning of an AM radio starting from its components to the modulation process.

AM radio waves carry transmissions over the air, as part of the electromagnetic range that includes x-rays, ultraviolet rays, microwave, gamma, and several other rays. But, since the electricity in the air is basically random noise, how do the signals carry important information, such as voice or voice? That’s where the concept of modulation comes in, which is the foundation for both AM and FM transmissions.

Read on to learn about the concept of modulation and the AM radio working in more detail.

How does an AM radio work?

Amplitude Modulation is one of the simplest forms of radio broadcasting. And, as the name suggests, AM band uses the process of amplitude modulation to encode useful information on radio signals by collecting them and transforming them. Modulation simply refers to a process of change, which helps electromagnetic radiation adapt to carry important information. Without it, radio signals could not carry transmissions.

It operates in the 520-1710 kHz frequency range, and a specific frequency of this spectrum is termed as the carrier frequency. It carries the actual signal from the antenna to a receiving tuner (more on that later).

A carrier way typically oscillates at 800,000-17,000 cycles per second, which is quite fast to comprehend. Therefore, modulation is necessary. When modulation occurs, the carrier wave’s amplitude takes the shape of the radio program, in curved form. The carrier wave’s amplitude increases or decreases according to the audio of the radio program. Consider a steady radio wave, broadcasting on the AM band with an unchanged height/amplitude. This means the steady signal will not be carrying any essential information. For the steady signal to produce audio, it must first encode or modulate with information, such as voice or music. This process of modulation entails a change in the height of a wave or a signal’s amplitude strength. The change occurs in direct proportion to the input signal.

Here are the steps to how an AM radio works:

  • A radio signal is simply electronic current or electrons that are moving up and down quickly.
  • The transmitter radiates this signal outward into the field.
  • These waves travel over the air (at the speed of light).
  • The antenna picks the transmitter’s radio waves.
  • As the waves hit the receiver, the electrons inside vibrate, mimicking the original signal/sound. 
  • Next, the tuner separates one wave from the various signals the antenna receives.
  • The frequency of the signal will remain constant, but what will change is the amplitude (height) of the waves.
  • For example, you tune your radio to 550 on the AM dial. This means the wave is transmitting at 550,000 hertz. Now that you have set the tuner at 550, it will amplify this particular frequency. How?
  • It will use a demodulator to enable the current to flow in one direction, instead of flowing both ways.
  • Once the signal is modulated, you will have a varying signal, which is a copy of the original audio, going from 0 to positive.
  • The amplifier will then send this signal out as audio via the speaker or headphone. 

How does an AM antenna work?

Every radio that you see requires an antenna. These come in all shapes and sizes, depending on the frequency you’re trying to receive. When it comes to the AM band, you need a highly powerful antenna.

The interesting bit is that the AM antennas work differently from the FM antenna. While the FM antenna picks the radio’s wave electric part, the AM radio binds with the magnetic part. It’s made with a fine wire, which is looped around a ferrite core. As it concentrates on the radio’s magnetic part, it generates a bigger current in the loop. That means, even though the antenna appears to be quite tiny, it still packs plenty of power. You could have a longer antenna to receive better, but since radio waves and AM stations are pretty strong in urban locations, a longer length wouldn’t make much of a difference.

Radio tuner working

A radio tuner comprises a coil and wiper, which works to take up the energy that a radio antenna typically gathers. The antenna receives countless waves at a time and the tuner works to separate and pick one wave from the several thousand incoming radio signals. So, the job of a radio tuner is to resonate at and amplify a specific frequency, while ignoring the others. The amplifier then strengthens the signal, passes it through the demodulator, and last, outputting it through the speaker as the audio you hear.

Which type of signal is used by AM radio?

You may wonder, when there are several thousand waves passing in the air, how does a radio differentiate whether they’re AM or FM? The answer to this is that both AM and FM operate at different frequencies. While the AM waves are longer, FM radio waves have higher frequencies. The AM receiver picks these waves through different antennas and by employing different methods to convert the radio waves into comprehensible information, i.e. voice or music. Amplitude modulation uses continuous sine wave signals, which pass through “detectors” (diode) in the radios. The job of these circuits is to change or modulate the AM signals to sounds. 


AM radios are one of the thousand wireless technologies that use radio waves for communication. Invisible and undetectable to the human eye, these waves travel several miles to transmit conversations, data, and even music. The incredibly simple technology uses a couple of components, such as the transceiver, antenna, tuner, amplifier, and detector. Its efficiency and usefulness can be seen in several applications.

Amplitude Modulation radios are a vital part of the modern aviation industry for communication and navigation. Hopefully, you have now understood the radio’s technology and how the AM radio waves propagate to make communication and transmission possible.