Which one of the following is not classified as pulse modulation?

The $TV$ transmission tower at a particular station has a height of $125\, m$. For doubling the coverage range,the height of the tower should be increased by .............$m$.

Range of frequencies allotted for commercial $FM$ radio broadcast is

An audio signal $v_{m} = 20 \sin(2 \pi \times 1500 t)$ amplitude modulates a carrier $v_{c} = 80 \sin(2 \pi \times 100,000 t)$. The value of percent modulation is..........

The attenuation in optical fibre is mainly due to

Each television channel is allocated a bandwidth of approximately ........?