Communication System

Question 1

distance covered by a antenna of highet ‘h’

Answer 1

Question 2

distance covered between two antenna at the line of sight

Answer 2

Question 2

popoulation covered by the antenna if population density is given

Answer 2

Question 3

Answer 3

B

Question 4

skywave frequceny range

Answer 4

2-30 MHz

Question 5

space wave propagation frequency range

Answer 5

30-300 MHz

Question 6

carrier waves has high/low frequency

Answer 6

high frequcny

Question 7

carrier wave has large or small wavelength

Answer 7

small

Question 8

size of antenna is directly proportional to?

Answer 8

wavelength

Question 9

how to make a antenna size small

Answer 9

increase the frequency

Question 10

effective power radiated is related to?

Answer 10

Question 11

number of channels formula

Answer 11

max frequency available divided by bandwidth frequency(2f)

Question 12

what changed in AM?

Answer 12

amplitdue changes as the nam e suggests amplitude modulation

Question 13

max and mimimum amplitude of AM!?

Answer 13

Question 14

modulation index formula

Answer 14

Question 15

modulation index is less or more than 1

Answer 15

less than one

Question 16

final wave frequency depends on which freuency?!

Answer 16

carrier frequency

Question 17

final wave equation

Answer 17

Question 18

final wave equation in terms of side carriers and side bands

and what does side bands and main carrier denoted by

Answer 18

Question 19

upper side band frequency formula

Answer 19

Question 20

lower side band frequency formula

Answer 20

Question 21

bandwidth formula

Answer 21

Question 22

Answer 22

Question 22

power of wave in main carrier wave

Answer 22

Question 23

power of side bands

Answer 23

Question 24

which of the following quantities will be filtered out from the band pass filter?

Answer 24

Question 25

wavelength ranges of the different type of light waves

Answer 25

Question 26

The two basic modes of communication are

Answer 26

point-to-point and broadcast.

Question 26

bandwidth required by speech signals music Video signals TV signal

Answer 26

speech signals:- 2800 Hz (3100 Hz– 300 Hz) music:- 20 kHz Video signals:- 4.2 MHz TV signal:- 6 MHz

Question 27

frequency range for speech signals

Answer 27

300 Hz to 3100 Hz

Question 28

audible range of frequencies extends from

Answer 28

audible range of frequencies extends from 20 Hz to 20 kHz.

Question 29

bandwidth required by Coaxial cable Optical communication optical fiber

Answer 29

Coaxial cable:- 750 MHz. Optical communication:- 1 THz to 1000 THz optical fiber:- 100 GHz.

Question 30

just keep this table in mind

Answer 30

Question 31

The ionosphere is so-called because and it extends from a height of

Answer 31

The ionosphere is so-called because of the presence of a large number of ions or charged articles. It extends from a height of 65 Km to about 400 km above the earth’s surface.

Question 32

The density of the atmosphere increases/decreases with height.

Answer 32

The density of atmosphere decreases with height.

Question 33

The ionospheric layer acts as a reflector for a certain range of frequencies:

Answer 33

3 to 30 MHz

Question 34

Electromagnetic waves of frequencies higher than _____ penetrate the ionosphere and escape.

Answer 34

Electromagnetic waves of frequencies higher than 30 MHz penetrate the ionosphere and escape.

Question 35

sky wave propagation is used by

Answer 35

short wave broadcast services.

Question 36

Ionisation occurs due to the

Answer 36

absorption of the ultraviolet and other high-energy radiation coming from the sun by air molecules.

Question 37

write something abt the ionization of ions due to solar radiation

Answer 37

The degree of ionization varies with the height. The density of the atmosphere decreases with height. At great heights the solar radiation is intense but there are few molecules to be ionized. Close to the earth, even though the molecular concentration is very high, the radiation intensity is low so the ionization is again low. However, at some intermediate heights, there occurs a peak of ionization density.

Question 38

Space waves are used for

Answer 38

line-of-sight (LOS) communication as well as satellite communication.

Question 39

At frequencies above 40 MHz communication is essentially limited

Answer 39

At frequencies above 40 MHz, communication is essentially limited to line-of-sight paths.

Question 40

power radiated from an antenna is proportional to

Answer 40

power radiated is proportional to (l/λ)^2

Question 41

why do we need high frequency transmission

Answer 41

For a good transmission, we need high powers and hence this also points out the need of using the high-frequency transmission.

Question 42

define detection of signals

Answer 42

Detection is the process of recovering the modulating signal from the modulated carrier wave.

Question 43

the process of detection of signals

Answer 43

Question 44

whats Facsimile

Answer 44

Facsimile (FAX) It scans the contents of a document (as an image, not text) to create electronic signals. These signals are then sent to the destination (another FAX machine) in an orderly manner using telephone lines. At the destination, the signals are reconverted into a replica of the original document. Note that FAX provides an image of a static document unlike the image provided by television of objects that might be dynamic.

Question 45

Mobile telephones operate typically in the ____ range of frequencies

Answer 45

about 800-950 MHz (UHF)