TELECOM Radio And Television

Question 0

What does the aerial do?

Answer 0

Picks up radio waves of different frequencies and converts them to electrical signals ( by vibrating when receiving radio waves which cause electrical charges) (picks up all of the radio signals)

Question 1

What are the main parts of a radio receiver?

Answer 1

Aerial, tuner, decoder, amplifier, loudspeaker

                             power supply

Question 2

What does the tuner do?

Answer 2

Selects one particular frequency from the received waves.

Question 3

What does the decoder do?

Answer 3

Extracts the lower frequency audio signal from the transmitted higher frequency radio (carrier) signal

Question 4

What does the amplifier do?

Answer 4

Increases the strength of the electrical signal

Question 5

What does the loudspeaker do?

Answer 5

Converts the electrical energy to sound

Question 6

What part of a radio receiver uses a power supply? Why?

Answer 6

Amplifier, i order to have energy to increase the wave siz

Question 7

What is the difference between television parts and radio parts

Answer 7

There are two decoders and amplifiers; one of each for the audio waves and visual waves

Question 8

What does a loudspeaker do in a television?

Answer 8

Converts electrical energy to sound

Question 9

What does a picture tube do in a television?

Answer 9

Converts electrical signal to light

Question 10

How is light formed on a television screen?

Answer 10

An electron gun fires a beam of electrons at the phosphor paint on the screen where the kinetic energy is then turned into a spot of light.

Question 11

How are images built up on a television screen?

Answer 11

The electron gun fires electron beams across the screening a series of lines.

Question 12

How many lines are on a television screen?

Answer 12

625

Question 13

How are colours made on television screens?

Answer 13

Mixing light from red, green and blue electron guns.

Question 14

What is amplitude modulation?

Answer 14

Varying the amplitude of a high frequency carrier wave so as to carry a low frequency audio wave

Question 15

Carrier wave + audio signal —–>

Answer 15

amplitude modulated

Question 16

Why would a wave be frequency modulated?

Answer 16

Better sound quality and method can be heard with no interference

Question 17

How are television signals transmitted?

Answer 17

Same as radio except thecRrier wave is modulated to carry two signals (audio and visual)

Question 18

How is brightness varied on a television screen?

Answer 18

By varying the number of electrons hitting the screen

Question 19

How often is a new picture produced?

Answer 19

25 times each second

Question 20

Why do television pictures move?

Answer 20

Due to image retention each image merges into the next. since each picture is only slightly different from the one before the images appear to move.

Question 21

How are colours other than the primary colours produced on a screen?

Answer 21

By mixing them

Question 22

Red + green

Answer 22

Yellow

Question 23

Red + blue

Answer 23

Magenta

Question 24

Blue + green

Answer 24

Cyan

Question 25

Red + green + blue

Answer 25

White

Question 26

How colours than primary and secondary colours made?

Answer 26

Varying the intensities (eg giving slightly more red to produce orange rather than yellow)

Question 27

Why are waves amplitude modulated?

Answer 27

So as to travel longer distances.

Question 29

The ____ frequency audio waves and ____ frequency audio signals are electrical signals,

Answer 29

High frequency radio (carrier), low frequency audio

Question 30

What are the parts of a radio transmitter?

Answer 30

Modulator, amplifier, aerial

Question 31

What does the modulator do in a radio transmitter ?

Answer 31

Combines the radio and audio signal

Question 32

What does the amplifier do in a radio transmitter

Answer 32

Makes the electrical signal arronger

Question 33

What does the aerial do in a radio transmitter

Answer 33

Changes electrical signals into radio waves and sends them out in all directions

Question 34

How to radio stations keep signals separated?

Answer 34

Transmitting in different wave lengths

Question 35

How would a diaphragm of a loudspeaker react for high pitch sounds?

Answer 35

Increased vibrates rapidly

Question 36

How is a louder sound produced in a loudspeaker?

Answer 36

Increasing the current rough the coil and vibrations of diaphragm are much larger

Question 37

What are used to direct and electron gun?

Answer 37

Magnetic coils

Question 38

Are electrons coloured to produce coloured images?

Answer 38

No, it is the material of the dots

Question 39

Why are waves amplitude modulated?

Answer 39

So they can travel longer distances

Question 40

Simply, how is a moving picture seen (3)

Answer 40

Line build up, image retention and brightness variation

Question 52

Why are more transmitters need for FM waves?

Answer 52

The do not travel as far as amplitude modulated waves