An optical fibre communication system works on a wavelength of $1.3 \mu m$. The number of subscribers it can feed if a channel requires $20 \ kHz$ is:

$A$ signal emitted by an antenna from a certain point can be received at another point on the Earth's surface in the form of:

$A$ modulating signal $2 \sin (6.28 \times 10^{6} t)$ is added to the carrier signal $4 \sin (12.56 \times 10^{9} t)$ for amplitude modulation. The combined signal is passed through a non-linear square law device. The output is then passed through a band pass filter. The bandwidth of the output signal of the band pass filter will be $MHz$.

In amplitude modulation,determine the total maximum transmitted power in $kW$,if the carrier output is $1 \, kW$.

$A$ message signal of $3 \text{ kHz}$ is used to modulate a carrier signal of frequency $1 \text{ MHz}$ using amplitude modulation. The upper sideband frequency and bandwidth respectively are:

$A$ message signal of frequency $50 / \pi \text{ kHz}$ and peak voltage of $5 \text{ V}$ is used to modulate a carrier of frequency $1 \text{ MHz}$ and peak voltage $20 \text{ V}$. The modulation index is