Question

An audio signal of $V_m=5sin6\pi \times {10}^{3}t$ is to be modulated on a carrier wave given by $V_c=5sin2\pi \times {10}^{5}t$. The frequencies of the side bands and bandwidth are

• A. 103 KHz; 97 KHz; 6KHz
• B. 130KHz; 70KHz; 6KHz
• C. 130KHz; 97KHz; 3KHz
• D. 103KHz; 97KHz; 3KHz

Answer 1

The correct option is A 103 KHz; 97 KHz; 6KHz

$f_1=3\times {10}^3$
$f_2={10}^5$
Sidebands are defined as $f_2-f_1$ and $f_1+f_2$
Hence, sidebands are $97000Hz,103000Hz$
i.e. $97KHz,103KHz$
Bandwidth = Gap between sidebands $=103-97=6KHz$