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 maximum distance between the transmitting and receiving antennas for satisfactory communication in line of sight mode is $57.6 \ km$. If the height of the receiving antenna is $80 \ m$,the height of the transmitting antenna is (Radius of earth $= 6.4 \times 10^6 \ m$) (in $m$)

Sound waves cannot be transmitted directly after conversion into electrical waves because...

While tuning in a certain broadcast station with a receiver,we are actually

The maximum usable frequency $(MUF)$ in the $F$-region layer is $x$,when the critical frequency is $60 \, MHz$ and the angle of incidence is $70^\circ$. Then $x$ is ....... $MHz$.

For the propagation of $10 \ MHz$ signals as sky waves,what should be the minimum electron density in the ionosphere?