Question

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

• A. 220 kHz
• B. 180 kHz
• C. 360 kHz
• D. 440 kHz

Answer 1

The Correct Option is D

To determine the bandwidth required for frequency modulation (FM) transmission, we can use Carson's Rule. According to Carson's Rule, the bandwidth BW required for FM is given by:

BW = 2(\Delta f + f_m)

where:

• \Delta f is the frequency deviation.
• f_m is the maximum modulating signal frequency (here, 20 kHz).

This question provides the deviation ratio (which is the ratio of deviation to modulating frequency) as 10. Thus, the frequency deviation \Delta f can be calculated as:

\Delta f = \text{Deviation Ratio} \times f_m = 10 \times 20 \text{kHz} = 200 \text{kHz}

Substituting the values into Carson's Rule:

BW = 2(200 \text{kHz} + 20 \text{kHz})

= 2 \times 220 \text{kHz} = 440 \text{kHz}

Therefore, the bandwidth required for transmission is 440 kHz.

The correct answer is, therefore, 440 kHz.