Explain the "green house effect" of earth's atmosphere.

2

(a)

On what factors does the maximum range of ground wave propagation depend? How can the maximum range on ground wave propagation be increased?

2

(a)

Distinguish between 'Analog and Digital signals'.

2

(a)

a) Identify the boxes, 'P' and 'Q' in the block diagram of a receiver shown in the figure:

(b) Write the functions of the blocks 'P' and 'Q'.

2

(a)

(i) What is the line of sight communication?
(ii) Why is it not possible to use sky waves for transmission of TV signals?
Upto what distance can a signal be transmitted using an antenna of height h?

2

(a)

Write the function of the following in communication systems.
(i) Transmitter
(ii) Modulator

2

(a)

Distinguish between analog and digital signals.

2

(a)

Name any two types of transmission media that are commonly used for transmission of signals. Write the range of frequencies of signals for which these transmission media are used.

2

(a)

Distinguish between a transducer and a repeater.

2

(a)

Write two factors justifying the need of modulation for transmission of a signal.

2

(a)

A carrier wave of peak voltage 12 V is used to transmit a message signal. Calculate the peak voltage of the modulating signal in order to have a modulation index of 75%. Why is modulation index generally kept less than one.

2

(a)

An audio signal of 1 kHz is used to modulate a carrier of 500 kHz. Determine.
(i) Sideband frequency.
(ii) Bandwidth required

2

(a)

The antenna current of an AM transmitter is 8A when only carrier is sent but it increases to 8.93A when the carrier is sinusoidally modulated. Find the percent-age modulation index

2

(a)

A 100 MHz carrier is modulated by a 12 kHz sine wave so as to cause a frequency swing of +50kHz. Find the modulation index

2

(a)