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RSTO's > A&P > Flashcards

A&P Flashcards

0
Q

Properties of an antenna

A 
Input impedence  
Polarisation
Radiation pattern
Gain
Reletive efficiency
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1
Q

What are the frequency bands?

A

HF 3-30mhz
VHF 30-300mhz
UHF 300MHz-3ghz
SHF 3-30ghz

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2
Q

Types of wave

A

Sky wave (hf comms)
Surface wave
Space wave direct wave/ground reflected

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3
Q

Surface wave

A

Polarisation: ventricle and close to ground
Freq: lower the freq the greater the range
Ground: better conducter (water)

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4
Q

Space wave

A

Heightened the antenna greater direct wave, lower the antenna greater the ground reflective wave

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5
Q

Skywave

A

Higher the freq the longer the range

Lower the angle longer the range

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6
Q

Nvis

A

Near vertices incidence Skywave

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7
Q

Properties of an antenna

A 
Input impedence
Polarisation
Radiation 
Gain
Relative efficiency
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8
Q

Range for surface wave

A

100km

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9
Q

Range of sky wave

A

NVIS (short range) - 300km
Medium range - 300km - 1500km
Long range - 1500 - 3000km

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10
Q

Antenna height for Skywave vs range

A

Lower the antenna the shorter the range

Higher and broad side on will increase the range

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11
Q

Ionosphere

A

D
E
F1
F2

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12
Q

What happens to ionosphere at night

A

D+E disappear

F1+2 combine

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13
Q

Predictable ionosphere variations

A

Geographical closer to equator more ionosphere
Seasonal summer
Day/night
Sunspot cycle

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14
Q

Unpredictable variations

A

Solar flares
Magnetic storms
Sporadic E

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15
Q

Factors affecting all 3 types of propagation

A

Antenna
Noise
Power output of transmitter
Reliever

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16
Q

Characteristics of a radio wave

A

Frequency
Velocity
Wavelength

17
Q

What is speed of light

A

300000000mps

18
Q

What is frequency

A

Number of complete cycles in 1 second

19
Q

What is wavelength

A

Distance wave has traveled In one second

Lambda

20
Q

Relationship between freq and wavelength

A

Higher the freq the shorter the wavelength

21
Q

Triangle

A

V

FXwavelength

22
Q

Antenna material

A

R4 copper wire = 71.3 for quatre wavelength
Braid = 68.5
All other D10 = 68

23
Q

Radio station

A 
Power supply
Intelligence input/output
Transceiver RF transmitter/RF receiver
Transmission line/coax
Antenna
24
Q

In a radio station what does a transceiver do

A

RF transmitter converts speech to RF

RF receiver converts RF to speech

25
Q

What does an oscillator do

A

Turn power into current

26
Q

What is resistance measured in

A

Ohms

27
Q

Coax must be

A

Robust
Flexible
Easily matched to dipole

28
Q

What makes impedence

A

Loss resistance

Radiation resistance

29
Q

What is LR and RR

A

LR is physical resistance in antenna

RR is electrical resistance that Carrie across the antenna

30
Q

Antenna matching

A

Right antenna for job

31
Q

Dipole

Unipole

A

Unipole is 1/4 wavelength
It’s also earthed to make 1/2 wavelength
Dipole is 1/2 wavelength

32
Q

Input impedence

A

Larger the antenna more resistance

Matched by the ATU (antenna tuning unit)

33
Q

Polarisation

A

Vertically/polarised/directional

34
Q

Radiation pattern

A 
Eg broad side on
Some antennas radiate more in one direction 
Position in correct direction 
Uni/monopole 360•
Dipole need to be broad side on
35
Q

Antenna gain

A

Directional

Measured in decibels

36
Q

Antenna efficiency

A

Bad connection
ATU
Good earth

37
Q

Relationship between frequency and range

A

Higher frequency the shorter the range because every wavelength that hits the ground reduces power

38
Q

D layer

A

50km
Absorbs power during the day
Reduces noise

39
Q

E layer
F1
F2

A

Refraction occurs

Noise created

RSTO's (25 decks)

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