Ch. 1 - Radio Principles Flashcards Preview

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Flashcards in Ch. 1 - Radio Principles Deck (86)
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1
Q

Do sound waves require a medium to be effective

A

Yes

2
Q

Do radio waves require a medium to be effective

A

No

3
Q

What speed do sound waves travel at

A

Speed of sound

4
Q

relationship between speed of sound and altitude

A

Speed of sound decreases with altitude

5
Q

Speed of sound at sea level

A

660kt (340m/s)

6
Q

Speed of sound at 20,000ft

A

610kt

7
Q

Speed of sound at 40,000ft

A

570kt

8
Q

Why does the speed of sound decrease with altitude

A

The speed of sound is dependent on air temperature and temperature decreases as altitude increases

9
Q

What frequencies can the human ear respond to

A

20-20,000Hz

10
Q

What are audio frequencies

A

All frequencies that the human ear can respond to

11
Q

How many cps in 1,000,000Hz

A

1,000,000cps

12
Q

How many Hz in 1MHz

A

1,000,000Hz

13
Q

What happens to air when sound waves pass through it

A

Compression and expansion of air pressure in a regular and symmetrical manner, because waves move through the air, the air doesn’t move

14
Q

What type of waves are radio waves

A

Electromagnetic waves

15
Q

Do radio waves require a medium

A

No

16
Q

What happens to radio waves when the pass-through dense mediums such as brick

A

They attenuate at rate dependent on the density of the medium and the frequency of the wave

17
Q

Do sound or radio waves travel further

A

Radio

18
Q

Which is slower radio or sound waves

A

Sound

19
Q

What speed to radio waves travel at

A

Speed of light

20
Q

What is the speed of light

A

300,000km/s

21
Q

What property of radio waves is key to radiotelephony

A

The ability to select one particular frequency, because if a message was to be sent using sound waves the recipient would receive all the frequencies associated with the transmitted pressure pattern but being able to use radio waves on a selected frequency means that all other frequencies are filtered out and a clear signal is a result, an added advantage of this is that specific frequencies can be selected for specific purposes.

22
Q

What is the purpose of the microphone

A

Transfer your spoken words into electromagnetic radio waves, which can be sent to a receiver

23
Q

Wavelength

A

The length of a single wave (or of one complete cycle). It is also the distance travelled by the wave during transmission of one cycle

24
Q

Frequency

A

The number of completed waves passing a point in one second

25
Q

Frequency increase = wavelength ______

A

Decreases

26
Q

Amplitude

A

The distance from the top or bottom of the wave to the mean value line of a wave

27
Q

Greater amplitude = Greater ______

A

Volume/strength of a signal

28
Q

Types of frequency bands

A

HF (high frequency), VHF (very high frequency)

29
Q

VHF range

A

30MHz - 300Mhz

30
Q

HF range

A

3MHz - 30MHz

31
Q

Advantages of VHF

A

Lots of frequencies can support the high number of services required and the reception is better than those at lower frequencies which are prone to interference

32
Q

Disadvantage of VHF

A

Inability of signals to ‘bend’ around obstacles such as mountains.

33
Q

Relay equipment in NZ

A

The mountainous terrain in New Zealand reduces VHF range considerably in some areas and for that reason automatic relay equipment has been installed on high ground, which continues to provide access to high quality communications on VHF (line-of-sight) frequencies over most of the country.

34
Q

Why does VHF range increase with alt

A

The higher you fly, the further you see

35
Q

Why is care exercised in the allocation of VHF frequencies to stations within reception range of each other

A

If stations are on the same VHF frequency, loss of signal would result if a number of aircraft transmit at the same time

36
Q

What is a transceiver

A

A radio set is both a transmitter and a receiver

37
Q

What is a NAV/COM set

A

VHF navigation receiver and the communication transceiver in one radio set

38
Q

What is an audio selector panel

A

Connects the various NAV and COM radio sets to the speaker or headphones, and the COM sets (if more than one) to the microphone.

39
Q

Types of microphones

A

hand-held microphone and the boom-mike

40
Q

Advantages of the boom mike

A

It allows you to operate your radio without having to take your hands off the control column

41
Q

How does the microphone work

A

Converting pressure waves produced by your voice into electromagnetic signals through the use of vibrating carbon particles or a diaphragm in the microphone

42
Q

What is intelligence

A

Your spoken words

43
Q

is it possible to transmit your messages directly as radio waves

A

No

44
Q

What is the carrier wave

A

The radio frequency signal sent out when you press the microphone button (without speaking into it)

45
Q

Modulation

A

The superimposing of intelligence on a radio carrier wave

46
Q

Two types of modulation

A

Amplitude Modulation (AM) and Frequency Modulation (FM)

47
Q

What is AM

A

Involves the superimposing of intelligence upon the carrier wave by varying the amplitude of the waves while the frequency (and thus wavelength) remains constant.

48
Q

What is FM

A

Involves the superimposing of intelligence upon the carrier wave by varying the frequency of the waves while the amplitude remains constant.

49
Q

Why is FM better then AM

A

Production of clearer signals and a greater availability of channels within a given range of frequencies

50
Q

What happens if the microphone is positioned too far away from your mouth

A

The pressure waves on the diaphragm will be weaker and the electromagnetic signals will be weaker

51
Q

What happens if you speak too loudly into the microphone

A

The strong pressure waves will cause the diaphragm to vibrate to their full travel and distorted signals are the likely result

52
Q

What must you do before speaking into the microphone

A

Hold down control column button

53
Q

is it possible to receive messages whilst you are transmitting

A

No

54
Q

When transmitting your message on a given frequency is it possible for other transmissions on that frequency within range

A

No

55
Q

Why is it important to release the microphone button

A

You are blocking the frequency and no other stations can use it with clarity

56
Q

What is a squelch

A

Eliminates unwanted signals such as static

57
Q

What do you do when the volume control is set to a desired level and static is being experienced

A

Turn squelch down until unwanted noise ceases

58
Q

What happens if you turn the squelch fully down

A

Cut out the signal as well as the static

59
Q

What must you do before transmitting through the mic

A
  • Listen out on the frequency to be used. Only commence transmitting when the frequency is clear and your transmission is not likely to block or interfere with users already on the frequency.
  • Decide on what you want to say
60
Q

Fault finding procedure for radio not working

A
  • Master, avionics, radio ON
  • Correct settings on the audio selector panel
  • Check circuit breaker
  • Mic leads
  • Correct frequency
  • Volume + Squelch level
61
Q

What radio equipment can not be used for transmissions

A

ELT and Transponder

62
Q

Transponder purpose

A

Enables a ground-based radar controller to determine the location (and altitude in most cases) of an aircraft. The information can also be obtained by the pilot of an aircraft equipped with an ACAS in order to ascertain the position of other transponder equipped aircraft in its vicinity

63
Q

ACAS

A

Airborne Collision Avoidance System

64
Q

How does a transponder work

A

A signal sent from a ground-based radar unit is received by the aircraft transponder. The signal triggers the aircraft transponder to send a coded signal back to the radar unit. Bearing and distance information from the ground radar unit (or ACAS equipped aircraft) can thereby be determined.

65
Q

Request to operate without a transponder transmission

A

The pilot must append the words “NEGATIVE TRANSPONDER” to the request.

66
Q

How is transponder mandatory airspace indentified

A

The letters TM on visual aeronautical charts

67
Q

What airspace in NZ is TM

A

Controlled

68
Q

Transponder mode a info

A

Four figure code

69
Q

Transponder mode c info

A

Altitude

70
Q

Transponder functions

A
  • OFF
  • SBY
  • ON
  • ALT
  • TST
71
Q

Transponder OFF

A

Transponder is off

72
Q

Transponder SBY

A

The transponder is switched on but will not reply to (radar) interrogation

73
Q

Transponder ON

A

Send mode a info only

74
Q

Transponder ALT

A

Send mode a and c info

75
Q

Transponder TST

A

Transponder test function

76
Q

Transponder code 1200

A

Fixed wing aircraft flying VFR

77
Q

Transponder code 1500

A

Helicopter flying VFR

78
Q

Transponder code 2200

A

Aircraft operating in the circuit of a controlled aerodrome

79
Q

Transponder 7500

A

Unlawful interference (hijacking)

80
Q

Transponder code 7600

A

Communications failure

81
Q

Transponder code 7700

A

Emergency

82
Q

Squawk indent

A

Press transponder INDENT button once. This causes your aircraft symbol on the radar screen to flash so that the controller can readily identify your aircraft. You must not push the IDENT button unless instructed.

83
Q

HF radios

A

Transmissions are reflected back to earth by the ionosphere (a layer of charged ions in the stratosphere). These reflected signals (sky waves) are able to reach much further than VHF transmissions and in the case of mountainous terrain shielding VHF signals the HF reflected transmissions can reach aircraft flying in the lee of mountains

84
Q

Disadvantages of HF

A

Static interference and signal fading

85
Q

Radio aerial length

A

The length of an aerial is related to the wavelength (and therefore frequency) of the signals. As a rule, an aerial should be equal in length to the wavelength of the signal or half the wavelength or quarter wavelength

86
Q

HF and VHF aerial length

A

VHF, being of very high frequency and short wavelength, requires a shorter aerial than HF which has a longer wavelength