Radio Theory

Question 1

What is electricity

Answer 1

A form of energy produced by the movement of electrons in atoms

Question 2

What is Ampere’s law?

Answer 2

An electric current produces a magnetic field perpendicular to the flow direction

Question 3

Radio waves are a form of electromagnetic energy that are similar in behaviour to light. True or False?

Answer 3

True.

Question 4

How fast do radio waves travel?

Answer 4

300 million metres per second

Question 5

Can radio waves travel through a vacuum?

Answer 5

Yes

Question 6

How do radio waves travel?

Answer 6

Generally in a straight line

Question 7

Can you hear radio waves?

Answer 7

No they’re inaudible without specialist equipment

Question 8

What is a cycle?

Answer 8

The wave travelling from 0, up, down and back to 0

Question 9

What is amplitude?

Answer 9

The maximum displacement or value attained by the wave from its mean value from the cycle.

(The further away it moves from 0 along the x-axis)

Question 10

What is a wavelength?

Answer 10

Distance in metres or part of a metre between corresponding points in consecutive waves

Question 11

What symbol represents wavelength?

Answer 11

Lambda symbol

Question 12

Define Frequency

Answer 12

The rate of repetition of the cycle in one second.

One cycle per second is known as one hertz.

Question 13

Frequency is represented by which symbol?

Answer 13

F

Question 14

A kilohertz (1KHz) is equal to how many hertz?

Answer 14

1,000Hz

Question 15

One megahertz (1MHz) is equal to how many hertz?

Answer 15

1,000,000 Hz

Question 16

One Gigahertz (1GHz) is equal to how many hertz?

Answer 16

1,000,000,000 Hz

Question 17

Longer wave length is lower frequency.

True or False?

Answer 17

True.

Question 18

Shorter wavelength is a higher Frequency.

True or False?

Answer 18

True or False?

Question 19

What is the equation for Velocity (C)?

Answer 19

C=F x lambda

Velocity=Frequency x Wavelength

Question 20

What device modulates carrier waves?

Answer 20

The local oscillator

Question 21

What can be modulated?

Answer 21

Amplitude or Frequency

Question 22

What does AM and FM stand for?

Answer 22

Amplitude Modulation

Frequency Modulation

Question 23

How does a Modulator (local oscillator) work?

Answer 23

The audio signal is fed into the modulator which combines the carrier wave and audio wave.

Question 24

What are the advantages of Frequency Modulation (FM)?

Answer 24

1) Resilience to Noise
2) Easy to apply Modulation at low power
3) Use of efficient radio frequency amplifiers

Question 25

What are the advantages to Amplitude Modulation (AM)?

Answer 25

1) Stronger stations can override weaker stations | 2) A heterodyne (sequel) heard if both stations are transmitting simultaneously.

Question 26

Which Modulation is used to broadcast ATC RTF?

Answer 26

AM as it doesn’t require excellent audio clarity

Question 27

Reducing the size of an aerial can be made possible by transmitting a portion of the wavelength. True or False?

Answer 27

True.

Question 28

Using what part of the cycle is known as Half-wave aerial?

Answer 28

The top of the positive wave.

Question 29

Using what part of the cycle is known as quarter wave aerial?

Answer 29

90 degrees of the cycle

Question 30

If you only use half the wave what must you do to the power to get the same range?

Answer 30

Double the power

Question 31

The electromagnetic field radiates___________ to the antenna

Answer 31

Perpendicular

Question 32

Signals received will be very weak and will need to be_______

Answer 32

Amplified

Question 33

What does the amplifier do?

Answer 33

Makes the signal stronger | Down side amplifies any noise, has no “noise gate”

Question 34

What does the demodulator do?

Answer 34

It earths the carrier wave out and feeds audio wave into Audio speaker

Question 35

How does the speaker relay the audio wave?

Answer 35

Signal fed into coil wire around the speaker magnet. In turn, moving the diaphragm of the speaker.