FM Full Form

The FM radio full form, Frequency Modulation, was invented by American engineer Edwin Armstrong in 1933. It is used worldwide to provide high-quality sound over broadcast radio. FM radio is capable of producing higher fidelity i.e. more effective reproduction of the original sound in comparison to the other broadcast technologies such as AM broadcasting (Amplitude Modulation). FM radio stations use a very high-frequency range of radio frequencies. 

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What Is the Full Form of FM?

FM stands for  “Frequency Modulation” is a method of transferring radio waves that can be used to broadcast radio stations. The frequency used by FM ranges from 87.5 MHz to 108MHz. 

AM FM Full Form 

The full form of AM and FM is Amplitude Modulation and Frequency Modulation respectively. 

AM or Amplitude Modulation is a technique used in electronic communication, most commonly used for transmitting messages with a radio carrier wave. In AM, the amplitude of the carrier wave is varied in proportion to that of message signals such as audio signals. AM was the earliest method of modulation used for transmitting audio in radio broadcasting. It was introduced during the first quarter of the 20th century. AM is used in many forms of communication including AM broadcasting: Very High-Frequency, shortwave radio, two-way radios, amateur radio, aircraft radio, citizens band radio, and in computer modem in the form of Quadrature Amplitude Modulation. 

FM full form, frequency modulation is a type of modulation that conveys information by changing the frequency of a carrier signal whereas the older amplitude modulation or AM changes the amplitude of the carrier signal, with its frequency remaining constant.  

With FM long-form, frequency modulation, the frequency deviation from the assigned carrier wave at any instant is directly proportional to the amplitude of the (audio) input signal, determining the instant frequency of the transmitted signals. As transmitted FM signals use more bandwidth than AM, this form of modulation is commonly used with a higher VHF (Very High frequency) or UHF (Ultra High Frequency), and by the TV, FM broadcast band, land mobile radio system, etc,

Benefits of Frequency Modulation Over Amplitude Modulation 

• The amplitude of FM remains constant throughout the period. This enables the encoders and decoders to remove the noise from the received signals. This is carried out with the help of a filter that removes signals of wavelength greater than that of transmitted signals hence removing the noise. Frequency modular systems are noise immune systems. As the AM signals transfer information using the amplitude, the envelope of the waveform cannot be changed.

• It is possible to reduce the voice in FM by further increasing the frequency deviation. This is a feature that AM does not have as it is not possible to exceed 100% modulation without causing severe distortions.

• The power consumption for signal transmission in AM is higher than FM. In AM, then power depends on the modulation index, also known as MA. When MA reaches unity, the power consumption is 100%. In FM, the power of transmission signals is proportional to the amplitude of unmodulated carrier signals and it is constant. Hence, FM is more power-efficient than AM. 

• FM broadcast systems operate in VHF (Very High frequency) or UHF (Ultra High Frequency) ranges at which there happens to be less noise than the MF (Medium Frequency) and HF (High Frequency) ranges occupied by AM broadcasts.

• There is no guard between two adjacent channels in the AM system. This increases the occurrence of interference of AM radio stations unless one system is sufficiently strong to overpower the other. Where in the case of FM, the adjacent signals are separated by guard bands which result in very little interference between FM adjacent channels. 

Disadvantages of Frequency Modulation Over Amplitude Modulation 

• The equipment required for both FM and AM is quite different. The equipment required in FM is costlier than AM as they are much more complex and involve complicated circulatory systems. Therefore, FM systems are more expensive than AM.

• The FM transmitter and receiver design are relatively complex for modulation and demodulation in comparison to the design of AM transmitter and receiver.

• FM has less coverage in comparison to the AM.

• There is an infinite number of sidebands in an FM system resulting in a theoretical bandwidth of an FM signal being infinite. The bandwidth is limited by Carson’s rule but it is still larger than that of the AM system. The bandwidth of the AM system is only twice the modulation frequency. This is another reason why FM is costlier than AM.

• A considerably greater typically 200 kHz is required in FM broadcast in comparison with the AM broadcast which requires only 10 kHz. This is one of the serious limitations of FM.

Difference Between AM and FM