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Communication is a fundamentalaspect in all societies. Nowadays, there are several types of communicationsystems, among them the radio communication system through Radio station.This system transmits information from one place toanother through the radio waves. As in any other communication system, in thisthere are also three fundamental entities, a transmitter, a receiver and atransmission channel.


 The basic operating principle of an FM transmitter can be demonstrated by the following block diagram:


It is an electromechanical element, which when subjected to differences in pressure caused by the human voice, converts them into electromagnetic waves with a possible frequency of being heard by the human being (audio frequency signal).

Audio frequency (AF) amplifier:

A device whose function is to increase the amplitude of the audio frequency signal of the electromagnetic waves produced in the microphone in order to Broadcast radio.


Device where the modulation process is carried out in order for the Radio stationto work.


Transmitter element, responsible for the generation of a sinusoidal wave (carrier) at a chosen frequency, necessary to carry out the modulation.

Radio Frequency (RF) Amplifier:

This device has the function of increasing the amplitude of the radio frequency signal produced by the modulation, conserving the frequency, in order to be able to be sent through the communication channel through the antenna.


It is the conducting device that emits into space the electromagnetic waves generated in the emitter or that receives from the space these waves destined to the receiver. The geometric shape that an antenna can present depends essentially on the wavelength of the waves it emits or receives.

More information about antennas

  • Modulation

A process used to allow Radio station waves to carry the audio frequency information (voice and music). This process can be seen as being a system that receives two input signals and produces an output signal. One of these inputs is the information signal that is generated for example by the microphone (audio frequency signal), this input is called the modulating signal, the other input is an appropriate signal to transmit through the channel. (air), which input has the function of transporting the information to be transmitted, and is therefore known as the carrier signal. The output signal is called the modulated signal (radio frequency signal).

  • There areseveral techniques for modulating a radio frequency carrier wave

Modulation in Amplitude (AM): The amplitude of the carrier signal directly accompanies the amplitude variations of the audio frequency wave.

Frequency Modulation (FM): The frequency of the carrier wave is directly proportional to the amplitude variations of the audio frequency waves.

The great advantage of FM modulation over AM modulation is that the noise level at reception is reduced. As to the choice, which modulation technique to use, it must take into account the characteristics of the signal to be transmitted and the characteristics of the communication channel. 

  • Reception

 The basic operating principle of an FM receiver can be demonstrated by the following block diagram:

  • Demodulator

It is the element that performs the inverse process of modulation, that is, it eliminates the carrier wave of the modulated signal, in order to extract the modulating signal, which is the signal that contains the information to be transmitted.

  • Loudspeaker 

It is a device that transformsthe electromagnetic waves into vibrations that cause different pressures in theair that is around them, reproducing the original signal containing theinformation. These differences in pressure are interpreted by our ears as the soundwe hear on the Broadcast radio.