A FM Broadcast transmitter, using modulating signal of frequency 20 kHz has a deviation ratio of 10. The Bandwidth required for transmission is:

We are given an FM broadcast transmitter with a modulating signal frequency of $$f_m = 20$$ kHz and a deviation ratio of 10.

The deviation ratio (also called modulation index) is defined as $$m_f = \frac{\Delta f}{f_m}$$, where $$\Delta f$$ is the maximum frequency deviation. So $$\Delta f = m_f \times f_m = 10 \times 20 = 200$$ kHz.

By Carson's rule, the bandwidth required for FM transmission is $$BW = 2(\Delta f + f_m) = 2(200 + 20) = 2 \times 220 = 440$$ kHz.

Hence, the correct answer is Option D.