| 1. In AM modulation, amplitude of the signal is varied, and frequency and phase are kept constant. |
1. In FM modulation, frequency of the signal is varied, and amplitude and phase are kept constant. |
| 2. AM has two sidebands |
2. FM has infinite number of sidebands |
| 3. The carrier of AM comprises of most of the transmitted power, which contains no information. |
3. All transmitted power in FM is useful, and there is no wastage of power unlike AM. |
| 4. Modulation index in AM varies from 0 to 1. |
4. Modulation index in FM is always greater than one. |
| 5. AM is more noisy since the AM receivers do not have amplitude limiters. |
5. Noise in FM can be reduced by employing amplitude limiters to remove the amplitude variations caused by noise. |
| 6. AM has narrow channel bandwidth which is 2$f_m$. |
6. The bandwidth in FM is much higher, up to 10 times as that of AM. |
| 7. In AM if two or more signals received at same frequency, then both will be demodulated, this can lead to interference. |
7. In FM if two or more signal received at same frequency, the receiver will capture the stronger signal and eliminate the weaker signal. |
| 8. AM broadcast operates in the medium frequency (MF) and high frequency (HF). |
8. FM broadcast operates in the upper VHF and UHF range, where noise effects are minimal. |
| 9. The design of AM transmitter and receiver is not complex for the modulation and demodulation purpose. |
9. The design of FM transmitter and receiver is relatively complex for the modulation and demodulation purpose. |
| 10. AM transmission and reception equipments are not that expensive since the circuitry is relatively simple. |
10. FM transmission and reception equipment is expensive as the circuitry is complex. |
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