Frequencies in the UHF range normally propagate by means of:

A basic communication system consists of
(a) transmitter
(b) information source
(c) user of information
(d) channel
(e) receiver
Choose the correct sequence in which these are arranged in a basic communication system:

Out of the following, which is not an essential element of a communication system?

A device that connects one computer to another across ordinary telephone lines is called

The fraction of world's human population using the services of internet is

Which factor decides the quality of reproduced document sent by a FAX?

What is meant by skip distance?

Attenuation refers to -------------- during propagation.

Two waves A and B of frequencies 2 MHz to 3 MHz, respectively are beamed in the same direction for communication via sky wave. Which one of these is likely to travel longer distance in the ionosphere before suffering total internal reflection?

What is the meaning of the term 'attenuation' used in communication system?

A TV transmission tower antenna is at a height of 20 m. How much service area can it cover if the receiving antenna is
(i) at ground level,
(ii) at a height of 25 m?
Calculate the percentage increase in area covered in case (i) relative to case.

Distinguish between 'Analog and Digital signals'.

(i) Define modulation index.
(ii) Why is the amplitude of modulating signal kept less than the amplitude of carrier wave?

Draw a block diagram showing the important component in a communication system. What is the function of a transducer?

Rita was studying in 10th class, one day she asked her father to explain the working of remote control of TV. Her father was not knowing the answer, but he made up his mind to understand the working of remote control. He found one shop where remote controls were repaired. The shopkeeper showed to Rita's father the inside of the remote control and explained her the working. Rita's father explained her the working of remote control, Rita was happy and satisfied.
(a) What are the values Rita's father displayed in his act?
(b) Name the diode used in remote control.

Explain why T.V. transmission towers are usually made high.

Estimate the fastest bit rate capable of being carried by light of wavelength 1.3 \(\mu m\). How many phone calls could be carried at this bit rate? Bandwidth of optical fibre = 2 GHz.

Define modulation index.Why is its value kept, in practice, less than one? A carrier wave of frequency 1,5 MHz and amplitude 50 V is modulated by a sinusoidal wave of frequency 10 kHz producing 50% amplitude modulation.Calculate the amplitude of the AM wave and frequencies of side bands produced.

Distinguish between 'sky waves' and 'space waves' modes of propagation in communication system.
(a) Why is sky wave mode propagation restricted to frequencies upto 40 MHz?
(b) Give two examples where space wave mode of propagation is used.

In the famous conversation, Rakesh Sharma, the first Indian Astronaut in space, was asked by the Prime Minister Indira Gandhi as to how India looked from space.To which he replied,'Sare Jahan Se Achcha' (better than the whole world).
Read the above passage and answer the following questions:
(i)   Which scientific mode of communication enabled the Prime Minister to speak to the Astronaut?
(ii)   Name the scientific values displayed in this anecdote.
(iii) Which values are being reflected in the reply given by the astronaut?
(iv) Give one more example of this scientific mode of communication in everyday life situations.

A TV transmitting antenna is tall. How much service area this transmitting antenna cover, if the receiving antenna is at the ground level? Radius of earth = 6400 km.