Question

An audio signal of 15000 Hz modulates a carrier generated by a tank circuit containing 1 nf capacitor and 10 microhenry inductor. Calculate the frequencies of first pair of side bands.

Answer 1

Here,$f_m$=15000Hz = 15kHz
$C=1nF={10}^{-9}{F}_1,f_{SB}=?$
$L=10\mu H=10\times {10}^{-6}H={10}^{-5}H$

$f_c=\frac{1}{2\pi \sqrt{LC}}=\frac{1}{2\times \frac{22}{7}\sqrt{{10}^{-5}\times {10}^{-9}}}=\frac{{10}^7\times 7}{44}Hz=1592kHz$

$f_{SB}=f_c\pm f_m$
$=1592\pm 15=1607kHzor1577kHz$