The amplitude of upper and lower side bands of A.M. wave where a carrier signal with frequency 11.21 MHz, peak voltage 15 V is amplitude modulated by a 7.7 kHz sine wave of 5V amplitude are $${a \over {10}}V$$ and $${b \over {10}}V$$ respectively. Then the value of $${a \over b}$$ is ____________.

A message signal of frequency 20 kHz and peak voltage of 20 volt is used to modulate a carrier wave of frequency 1 MHz and peak voltage of 20 volt. The modulation index will be :

A carrier wave V_c(t) = 160 sin(2$$\pi$$ $$\times$$ 10⁶t) volts is made to vary between V_max = 200 V and V_min = 120 V by a message
signal V_m(t) = A_m sin(2$$\pi$$ $$\times$$ 10³t) volts. The peak voltage A_m of the modulating signal is ___________.

A TV transmission tower antenna is at a height of 20 m. Suppose that the receiving antenna is at.

(i) ground level

(ii) a height of 5 m.

The increase in antenna range in case (ii) relative to case (i) is n%.

The value of n, to the nearest integer, is ___________.