Coaxial cable,a widely used wire medium,offers an approximate frequency bandwidth of:

If the highest frequency modulating a carrier is $5\, kHz$,then the number of $AM$ broadcast stations accommodated in a $90\, kHz$ bandwidth are ....... .

The height of the transmitting antenna is $180\,m$ and the height of the receiving antenna is $245\,m$. The maximum distance between them for satisfactory communication in line of sight will be .......... $km$ (given $R = 6400\,km$).

If the amplitude of an audio signal is half the amplitude of the carrier wave,what is the modulation index?

Given below are two statements:
Statement-$I$: $A$ speech signal of $2 \, kHz$ is used to modulate a carrier signal of $1 \, MHz$. The bandwidth requirement for the signal is $4 \, kHz$.
Statement-$II$: The sideband frequencies are $1002 \, kHz$ and $998 \, kHz$.
In the light of the above statements,choose the correct answer from the options given below:

To double the covering range of a $TV$ transmission tower,its height should be multiplied by