Amplitude Modulation (AM) and Frequency Modulation (FM) are two popular techniques used to transmit signals over long distances.
In AM, the amplitude of the carrier wave is varied according to the amplitude of the modulating signal, whereas in FM, the frequency of the carrier wave is varied according to the amplitude of the modulating signal.
Despite their similarities, there are several differences between AM and FM. One of the most significant differences is in the fidelity of the transmitted signal. Since AM has a narrow bandwidth, it has poor fidelity, whereas FM has a wider bandwidth, resulting in better fidelity.
Another significant difference is in the efficiency of power usage. In AM, most of the power is in the carrier wave, making it less efficient, while in FM, all the transmitted power is useful. This also results in less noise interference in FM as compared to AM.
In addition, AM broadcasts operate in the medium-frequency (MF) and high-frequency (HF) ranges, while FM broadcasts operate in the high-frequency (HF) and ultra-high-frequency (UHF) ranges.
Furthermore, in AM, adjacent channel interference is a common problem due to the narrow bandwidth, whereas FM avoids adjacent channel interference due to its wide bandwidth.
Overall, while both AM and FM have their own advantages and disadvantages, FM is generally considered to be a better option for high-fidelity transmission and minimal noise interference.