An amplitude modulated wave is represented by $c_m(t)= 10[1+0.6 \sin (1250 t)] \sin (10^8 t)$. Then the modulation index is

Which frequency range is suitable for sky wave propagation?

Frequencies in the $UHF$ range normally propagate by means of:

If a number of sine waves with modulation indices $n_1, n_2, n_3, \dots$ modulate a carrier wave, then the total modulation index $(n)$ of the wave is:

For an $FM$ carrier with a carrier frequency of $200 \text{ kHz}$ and a modulating frequency of $10 \text{ kHz}$,the modulation index is...

$A$ transmitting antenna has a height of $20 \,m$. What will be the height of the receiving antenna if the maximum distance between them for satisfactory communication in line-of-sight $(LOS)$ mode is $40 \,km$ (in $\,m$)? (The radius of the Earth is $6400 \,km$.)