The $T.V.$ transmission tower in Delhi has a height of $245 \ m$. The distance up to which the broadcast can be received (taking the radius of the earth to be $6.4 \times 10^6 \ m$) is .......... $km$.

In a communication system,the range for line-of-sight propagation on Earth is $d$ for an antenna height of $h$. If $h$ is doubled,then the new range is:

Which types of communication modes are used for the propagation of radio waves from one place to another?

Only $2 \%$ of the optical source frequency is the available channel bandwidth for an optical communication system operating at $1000 \,nm$. If an audio signal requires a bandwidth of $8 \,kHz$,how many channels can be accommodated for transmission?

The bandwidth of an optical fiber is approximately ........

An amplitude modulated wave is represented by the expression $v_{m}=5(1+0.6 \cos 6280 t) \sin (211 \times 10^{4} t) \; V$. The minimum and maximum amplitudes of the amplitude modulated wave are,respectively: