Theory -71 :-Comparison Of FM & AM Signal

Comparison Of FM & AM Signal

Both AM and FM System are used in commercial and non-commercial applications. Such as radio broadcasting and television transmission. Each system has its own merits and demerits. In a particular application, an AM system can be more suitable than  an FM system. Thus the two are equally important from the application point of view.

Amplitude Modulation: 

It is a modulation in which the amplitude of the carrier wave is changes according to the instantaneous amplitude of the modulating signal keeping phase and frequency as constant. The amplitude of the carrier wave is modified in order to send the data or information. It can transmit over long distances, have a large range. Its modulation index varies from 0 to 1. In amplitude modulation, the frequency and phase remain the same.

Frequency  Modulation:

It is a modulation in which the frequency of the carrier wave is changes according to the instantaneous amplitude of the modulating signal keeping phase and amplitude as constant. The frequency of the carrier wave is modified in order to send the data or information. It cannot transmit over long distances, have a smaller range. Its modulation index is always greater than one. In frequency modulation amplitude and phase remain the same.

Amplitude Modulation	Frequency Modulation
In amplitude modulation, the frequency and phase remain the same.	In frequency modulation amplitude and phase remain the same.
Its modulation index varies from 0 to 1.	Its modulation index is always greater than one.
It has only two sidebands.	It has an infinite number of sidebands.
It has simple circuit.	It has complex circuit.
The amplitude of the carrier wave is modified in order to send the data or information.	The frequency of the carrier wave is modified in order to send the data or information.
It requires low bandwidth in the range of 10 kHz.	It requires high bandwidth in the range of 200 kHz.
In AM received signal is of low quality.	In FM received signal is of high quality.
It works in a frequency range of 535 to 1705 Kilohertz (KHz).	It works in a frequency range of 88 to 108 Megahertz (MHz).
It operates in the medium frequency (MF) and high frequency (HF).	It operates in the very high frequency.
It has poor sound quality.	It has better sound quality.