100 W

\(\sim \) 400 m

A is transmitted via ground wave, B via sky wave and C via space wave.

space waves

10 MHz

Delta modulation involves simple pulse coding and decoding methods. A simple delta modulation uses just one bit per sample i.e. a ‘non-zero’ sample or one per sample. Thus, this method is convenient to use.

Velocity factor (VF) of a cable is the ratio of reduction speed of light in the dielectric of the cable. Velocity of light in vacuum is 3 x10⁸ m/sec. It reduces when light passes through a medium. Velocity of light in a medium is given
by v=c / \(\surd \) k & where, c-velocity of light in vacuum and
k- is the dielectric constant of the medium Vf. =v/c=l/\(\surd \)k
For a line velocity factor is generally of the order of 0.6 to 0.9

A diode detector should have the following characteristic for proper detection a) high rectification efficiency. b) negligible loading effect on previous stage c) low distortion

The television signals have frequencies in 100-200 MHz range. As ionosphere cannot reflect radio waves of frequency greater than 40 M back to earth, the sky waves cannot be used in the transmission of TV signals.

In a radar, a beam signal is needed in particular direction which is possible if wavelength of signal waves is very small. Since the wavelength of microwave is a few millimeter, hence they are used in radar.

In frequency modulation,the frequency of carrier wave is varied in accordance with the instantaneous value of the modulating voltage. 

\(\mu _{ A }=\sqrt { { \mu }_{ 1 }^{ 2 }+{ \mu }_{ 2 }^{ 2 }+{ \mu }_{ 3 }^{ 2 }+..... } \)

Modulation index of an AM wave lies between 0 and 1

The audio frequency signals are the modulating signals.

The audio frequency signals range from 20 Hz to 20 kHZ.