A&P

Question 0

Properties of an antenna

Answer 0

Input impedence  
Polarisation
Radiation pattern
Gain
Reletive efficiency

Question 1

What are the frequency bands?

Answer 1

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

Question 2

Types of wave

Answer 2

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

Question 3

Surface wave

Answer 3

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

Question 4

Space wave

Answer 4

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

Question 5

Skywave

Answer 5

Higher the freq the longer the range

Lower the angle longer the range

Question 6

Nvis

Answer 6

Near vertices incidence Skywave

Question 7

Properties of an antenna

Answer 7

Input impedence
Polarisation
Radiation 
Gain
Relative efficiency

Question 8

Range for surface wave

Answer 8

100km

Question 9

Range of sky wave

Answer 9

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

Question 10

Antenna height for Skywave vs range

Answer 10

Lower the antenna the shorter the range

Higher and broad side on will increase the range

Question 11

Ionosphere

Answer 11

D
E
F1
F2

Question 12

What happens to ionosphere at night

Answer 12

D+E disappear

F1+2 combine

Question 13

Predictable ionosphere variations

Answer 13

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

Question 14

Unpredictable variations

Answer 14

Solar flares
Magnetic storms
Sporadic E

Question 15

Factors affecting all 3 types of propagation

Answer 15

Antenna
Noise
Power output of transmitter
Reliever

Question 16

Characteristics of a radio wave

Answer 16

Frequency
Velocity
Wavelength

Question 17

What is speed of light

Answer 17

300000000mps

Question 18

What is frequency

Answer 18

Number of complete cycles in 1 second

Question 19

What is wavelength

Answer 19

Distance wave has traveled In one second

Lambda

Question 20

Relationship between freq and wavelength

Answer 20

Higher the freq the shorter the wavelength

Question 21

Triangle

Answer 21

V

FXwavelength

Question 22

Antenna material

Answer 22

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

Question 23

Radio station

Answer 23

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

Question 24

In a radio station what does a transceiver do

Answer 24

RF transmitter converts speech to RF | RF receiver converts RF to speech

Question 25

What does an oscillator do

Answer 25

Turn power into current

Question 26

What is resistance measured in

Answer 26

Ohms

Question 27

Coax must be

Answer 27

Robust Flexible Easily matched to dipole

Question 28

What makes impedence

Answer 28

Loss resistance | Radiation resistance

Question 29

What is LR and RR

Answer 29

LR is physical resistance in antenna | RR is electrical resistance that Carrie across the antenna

Question 30

Antenna matching

Answer 30

Right antenna for job

Question 31

Dipole | Unipole

Answer 31

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

Question 32

Input impedence

Answer 32

Larger the antenna more resistance | Matched by the ATU (antenna tuning unit)

Question 33

Polarisation

Answer 33

Vertically/polarised/directional

Question 34

Radiation pattern

Answer 34

``` 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 ```

Question 35

Antenna gain

Answer 35

Directional | Measured in decibels

Question 36

Antenna efficiency

Answer 36

Bad connection ATU Good earth

Question 37

Relationship between frequency and range

Answer 37

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

Question 38

D layer

Answer 38

50km Absorbs power during the day Reduces noise

Question 39

E layer F1 F2

Answer 39

Refraction occurs | Noise created