What happens when the deviation of an FM transmitter is increased?

When the deviation of an FM (Frequency Modulation) transmitter is increased, the frequency variations from the carrier frequency become greater. This leads to a broader range of signals being transmitted. Consequently, the spectrum of the frequency-modulated signal occupies more bandwidth.

This phenomenon is rooted in the nature of frequency modulation, where the modulation index, which is the ratio of the frequency deviation to the modulating frequency, directly influences the bandwidth of the signal. According to Carson's Rule, the total bandwidth required for an FM signal is approximately twice the sum of the maximum frequency of the modulating signal and the frequency deviation. Therefore, increasing the deviation results in a wider signal bandwidth, allowing for better audio and signal quality but potentially causing interference with adjacent channels if not managed properly.

While increasing deviation does not directly cause an increase in output power or lead to asymmetric modulation, it is important to understand how deviations relate specifically to the bandwidth required for the transmission.