Basics Transmission Flashcards

1
Q

What are transmissions

A

Electromagnetic waves propagating from a source

Can be caused by ac voltage / current through a wire

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2
Q

What happens if you put 2 wires next to each other

A

When wires are next to each other

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3
Q

What is the carrier wave

A

The number you dial into e.g. 119.875

Transport audio from
Transmitter to receiver

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4
Q

When does a transmission follow the curve of the earth

A

If it’s very long wavelength (VLF/ LF)

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5
Q

What is a Sky wave

A

MF / HF

Wave hits ionosphere which speeds up the top of the wave refracting it back down to earth

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6
Q

When is the ionosphere lowest

A

During the day the ionosphere is lower

Meaning the bounce is closer = can’t transmit a sky wave as far

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7
Q

Formula for line of sight range

A

Line of sight range = 1.23 x squareroot (height of transmitter in feet) + squareroot (height of airplane in feet)

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8
Q

What wavelength is skywave

A

MF / HF

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9
Q

What is VLF

A

3-30 KHZ

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10
Q

What is LF

A

30-300 KHZ

1000-9999m

Kilometric

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11
Q

What is MF

A

300-3000 KHZ

100-999m

Hectometric

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12
Q

What is HF

A

3-30 MHZ

10-99m

Decametric

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13
Q

What is VHF

A

30-300MHZ

1-9m

Metric

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14
Q

What is UHF

A

300-3000 MHZ

0.1 - 0.9m

Decimetric

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15
Q

What is SHF

A

3-30 GHZ

0.01-0.09m

Centimetric

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16
Q

What is modulation

A

Imposing audio onto carrier wave

17
Q

What is AM

A

Amplitude modulation

18
Q

What is FM

A

Frequency modulation

19
Q

Does aviation use AM or FM

A

AM because it uses less frequency channels as FM requires +/- HZ either side of frequency

20
Q

What are pulse waves used for

A

Digital

21
Q

What is phase signal used for

A

GPS

22
Q

What is omnidirectional antenna

A

Disturbs electromagnetic waves in every direction

23
Q

What is a helical antenna used for

A

GPS

Sits near cg of aircraft so it doesn’t move much

Circular polarisation

24
Q

What is the ideal length of an antenna

A

Wavelength

Can be 1/2 or 1/4

25
Q

How much more power do you need to get a signal to go twice the range

A

4 x as much power

26
Q

What is VDF

A

VHF direction finding

27
Q

What frequency does VHF use

A

118-136.975 MHZ

28
Q

What does VDF require

A

Transmitter + receiver in aircraft

29
Q

What is QDM

A

Magnetic bearing to station

30
Q

What is QOR

A

Magnetic bearing from station

31
Q

What is QUJ

A

True bearing to station

32
Q

What is QTE

A

True bearing from station

33
Q

What is class A accuracy for VDF

A

+/- 2°

34
Q

What is class B accuracy for VDF

A

+/- 5°

35
Q

What is class C accuracy for VDF

A

+/- 10°

36
Q

What is class D accuracy for VDF

A

.