Question

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

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

Answer 1

Answer: (D)

Given
FM broadcast
Modulating frequency $=20kHz=f$
Deviation ratio $=\frac{\text{ frequency deviation }}{\text{ modulating frequency }}=\frac{\Delta f}{f}$
$\Rightarrow$ frequency deviation $-\Delta f=f\times 10$
$=20kHz\times 10=200kHz$
$\Rightarrow$ Bandwidth $=2(f+\Delta f)$
$=2(20+200)kHz$
$=440kHz$