Question

A $1000kHz$ carrier is simultaneously modulated with $300Hz$, $800Hz$ and $2kHz$ audio waves. The frequencies present in the output are

• A. $999.7kHz,1000.3kHz,999.2kHz$
• B. $1000.8kHz,998kHz,1002kHz$
• C. $1002.8kHz,996kHz,1106kHz$
• D. Both $\left(A\right)$ and $\left(B\right)$

Answer 1

The correct option is D Both $\left(A\right)$ and $\left(B\right)$

$f_c=1000kHz$
$f_{m1}=300Hz$
$f_{m2}=800Hz$
$f_{m3}=2kHz$
$f_{USB1}=f_c+f_{m1}=1000\times {10}^3+300$
$=1000.3kHz$
$f_{LSB1}=f_c-f_{m1}=1000\times {10}^3-300$
$=999.7kHz$
$f_{USB2}=f_c+f_{m2}=1000\times {10}^3+800$
$=1000.8kHz$
$f_{LSB2}=f_c-f_{m2}=1000\times {10}^3-800$
$=999.2kHz$
$f_{USB3}=f_c+f_{m3}=1000\times {10}^3+2000$
$=1002kHz$
$f_{LSB3}=f_c-f_{m3}=1000\times {10}^3-2000$
$=998kHz$