When the receiving antenna is on the ground,the range of a transmitting antenna of height $980 \ m$ is (Radius of the earth $= 6400 \ km$) (in $km$)

For commercial telephonic communication,the frequency range adequate for speech signals is

$A$ carrier wave of amplitude $15\,V$ is modulated by a sinusoidal baseband signal of amplitude $3\,V$. The ratio of maximum amplitude to minimum amplitude in an amplitude modulated wave is:

$A$ message signal is super-imposed with a carrier signal. The resulting modulating signal $C_m(t)$ is given by $C_m(t)=A_1 \sin \left(\omega_1 t\right)+A_2 \sin \left(\omega_2 t\right)-A_2 \sin \left(\omega_3 t\right)$,where $\omega_2 < \omega_1 < \omega_3$. The modulation index and the angular frequency of the message signal respectively,are

$A$ carrier wave $v_{c}(t) = 160 \sin(2 \pi \times 10^{6} t) \text{ V}$ is made to vary between $V_{\max} = 200 \text{ V}$ and $V_{\min} = 120 \text{ V}$ by a message signal $v_{m}(t) = A_{m} \sin(2 \pi \times 10^{3} t) \text{ V}$. The peak voltage $A_{m}$ of the modulating signal is ..... .

During modulation,a transmitter supplies $9 \ kW$ to the antenna. Calculate the total power radiated during $40\%$ modulation in $kW$.