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Radio broadcasting is transmission of audio (sound), sometimes with related metadata, by radio waves intended to reach a wide audience. Stations are often affiliated with a radio network which provides content in a common radio format, either in broadcast syndication or simulcast or both. The broadcasting arrangement can be split into three part these includes; Transmitter, Transmission of radio waves and radio receiver.

Radio broadcasting : Transmitter

  1. Transmitter: Transmitter’s purpose is to produce radio waves for transmission into space. The important components of a transmitter are Microphone, audio amplifiers, oscillator, and modulator.Radio broadcasting : general principle
  • Microphone: A microphone is a device which converts sound waves into electrical waves. When the speaker speaks or a musical instrument is played, the varying pressure on the microphone generates an audio electrical signal which corresponds in frequency to the original signal. The output of microphone is fed to a multistage audio amplifier for raising the strength of weak signal
  • Audio amplifier: Its job is to amplify the weak audio signals coming from the micro phone.
  • Oscillator: The function of oscillator is to produce high frequency signal, called a carrier. Usually a crystal oscillator is used for the purpose. The power level of the carrier wave is raised to a sufficient level by radio frequency amplifier stages. Most broadcasting stations have carrier wave power of several kilowatts. Such high power is necessary for transmitting the signal to the required distances.
  • Modulator: The amplified audio signal and carrier wave are fed to the modulator. Here, the audio signal is superimposed on the carrier wave in a suitable manner. The resultant waves are called modulated waves or radio waves and the process is called modulation. The process of modulation permits the transmission of audio signals at the carrier frequency. As the carrier frequency is very high therefore, the audio signal can be transmitted to large distances. The radio waves from the transmitter are fed to the transmitting antenna or aerial from where these are radiated into space.
  1. Transmission of radio waves: The transmitting antenna radiates the radio waves in space in all directions. These radio waves travel with the velocity of light (3 x 10⁸) m/sec. The radio waves are electromagnetic waves and possess the same general properties. These are similar to light and heat waves except that they have longer wavelengths. It may be emphasized here that radio waves are sent without employing any wire. It can be easily shown that at high frequency, electrical energy can be radiated into space.
  1. Radio receiver: On reaching the receiving antenna, the radio waves induce tiny e.m.f in it. This small voltage is fed to the radio receiver. Here, the radio waves are first amplified and then signal is extracted from them by the process of The signal is amplified by audio amplifiers and then fed to the speaker for reproduction into sound waves.


Radio Broadcasting :Modulation

The process of changing some characteristics (e.g. amplitude, frequency, or phrase) of a carrier wave in accordance with the intensity of the signal is known modulation. Modulation means “change”.

The need for Modulation:

  1. Practical antenna length
  2. Operating range
  3. Wireless communication

Types of Modulation

  1. Amplitude modulation
  2. Frequency modulation
  3. Amplitude modulation (AM)

When the amplitude of high frequency carrier wave is changed in accordance with the intensity of the signal, it is called amplitude modulation.

The following point should be noted about amplitude modulation:

  1. The amplitude of the carrier wave change according to the intensity of the signal
  2. The amplitude variation of the carrier wave is at the signal frequency.
  3. The frequency of the amplitude modulated wave remains the same.

Limitations of Amplitude Modulation

  1. Noisy reception
  2. Low efficiency
  3. Small operating
  4. Lack of audio quality
  1. Frequency Modulation (FM)

When the frequency of carrier waves is changed in accordance with the intensity of the signal, It is called Frequency Modulation (FM).

In frequency modulation, only the frequency of the carrier wave is changed in accordance with the signal. However, the amplitude of the modulated wave remains the same i.e. carrier wave amplitude.

The following point should be noted about amplitude modulation:

  1. The frequency deviation of FM signal depends on the amplitude of the modulating signal.
  2. The centre frequency is the frequency without modulation or when the modulating voltage is zero
  3. The audio frequency does not determine frequency deviation

Advantages of FM over AM

  1. It gives noiseless reception
  2. The operating range is quite large
  3. It gives high-fidelity reception
  4. The efficiency of transmission

Radio broadcasting :Comparison of FM and AM


1 The amplitude of carrier remains constant with modulation The amplitude of carrier changes with modulation
2 The carrier frequency changes with modulation The carrier frequency remains constant with modulation
3 The carrier frequency changes according to the strength of the modulating signal The carrier amplitude changes according to the strength of the modulating signal
4 The value of modulation index can be more than 1 The value of modulating factor(m) cannot be more than 1 for distortion less AM signal


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