AM
Also called: amplitude modulation or medium wave
AM is an abbreviation for amplitude modulation and is the designation for a frequency band and a means of transmitting radio signals.
How does an AM signal work?
The sound of a radio station is converted by a transmitter mast into signals that can be picked up anywhere within range of the mast. Electromagnetic waves are used in this process. These waves or vibrations are expressed in the unit Hertz (Hz). These signals are not visible or audible to us but can be converted back into the original sound using a radio (or other device with a radio antenna).
In amplitude modulation (AM), tones are converted into radio waves of varying amplitude (amplitude). A carrier wave is transmitted at a fixed frequency, whose strength varies (modulates) based on the height of the tones being transmitted. This is in contrast to frequency modulation(FM) where the very frequency is the carrier of sound.
Because of the way AM works, an AM transmitter requires a relatively large bandwidth and a lot of transmission power. Nevertheless, the quality of AM sound is relatively low. Also, the signals are quite sensitive to interference from, for example, thunderstorms. On the other hand, the technology is simpler and AM signals can cover a greater distance than FM signals, for example.
What are AM frequencies?
The airwaves (the space available for radio traffic) are allocated for different purposes. Most AM signals use the band between 526.5 and 1605.5 kHz. This AM band is also referred to as medium wave.
In addition to medium wave, short wave and long wave also exist. Even the frequency band for 27MC, for more popular with truck drivers talking to each other with their "bakkie," works with amplitude modulation.
Well-known sea stations such as Radio Veronica and Radio Noordzee could be received via medium wave in the past. The ban on commercial radio stations was circumvented by broadcasting from international waters. Due to the long range of AM signals, the sea stations were easy to receive on the mainland despite the distance. Public stations, including Radio 1, could also be received via medium wave for many years.
Radio Nederland Wereldomroep broadcast on shortwave for many years. Because the frequencies of shortwave transmitters are reflected in the atmosphere, World Broadcasting could be received over very long distances. In 2007, the Dutch broadcaster stopped these broadcasts.
To broadcast on an AM frequency, a transmitter must have a license. In the Netherlands, licenses for AM frequencies are administered by the Netherlands Radiocommunications Agency (AT). Due to the emergence of alternative technologies such as FM and DAB+ and the dismantling of large AM stations in our country, no large national stations are active on the AM band today. However, a large number of local, regional and international stations can still be received via the band.