Radio Theory

Question 1

Describe Attenuation

Answer 1

Radio waves reduce in strength with range or time from point of transmission

Question 2

What factors effect attenuation?

Answer 2

1) Expanding Wave Front

2) Medium through which a wave passes resists the passage of energy

Question 3

As a signal is attenuated what is effect, amplitude/wavelength or frequency?

Answer 3

Amplitude decreases but wave length and Frequency remain unchanged

Question 4

The higher the frequency the greater the attenuation and shorter range. True or False?

Answer 4

True.

Question 5

What are radio waves divided into according to the frequency of transmission?

Answer 5

Internationally recognised wave bands

Question 6

Very low Frequency (VLF) operates on what spectrum and wave length size?

Answer 6

3-30KHz

100-10km

Question 7

Low Frequency (LF) operates on what spectrum and wave length size?

Answer 7

30-300KHz

10-1KM

Question 8

Medium Frequency (MF) operates on what spectrum and wave length size?

Answer 8

300KHz-3MHz

1KM- 100m

Question 9

High Frequency (HF) operates on what spectrum and wave length size?

Answer 9

3-30MHz

100m-10m

Question 10

Very High Frequency (VHF) operates on what spectrum and wave length size?

Answer 10

30-300MHz

10-1m

Question 11

Ultra High Frequency (UHF) operates on what spectrum and wave length size?

Answer 11

300MHz-3GHz

1m-10cm

Question 12

Super High Frequency (SHF) operates on what spectrum and wave length size?

Answer 12

3-30GHz

10cm-1cm

Question 13

Extremely High Frequency (EHF) operates on what spectrum and wave length size?

Answer 13

30-300GHz

1cm-1mm

Question 14

Characteristics of VLF

List all 3

Answer 14

1) Long range communication
2) Large aerials High transmission power
3) Prone static

Question 15

Characteristics of LF n MF

List all 5

Answer 15

1) long range communication
2) large aerials High transmission power
3) very congested wave band
4) NDB uses wave band
5) some radio broadcast

Question 16

Characteristics of HF

List all 5

Answer 16

1) Smaller Aerials And transmitter power
2) Optimum operating frequency varies diurnally
3) Long distance wireless telegraphy
4) RTF communication
5) Long range communication by day and night limited by diurnal and seasonal variation of the ionosphere

Question 17

Characteristics of VHF or UHF

List all 7

Answer 17

1) Line of sight communications
2) Maximum range dependant upon a/c height and aerial height
3) Small aerial and transmission power
4) Free from static interference; easy to suppress on a/c
5) Prone to ducting
6) Wave bands become congested
7) RTF/ILS/VOR/VDF/ Surveillance Radar

Question 18

Characteristics of SHF/EHF

List all 4

Answer 18

1) Short range communications
2) severe attenuation
3) Precision Surveillance and airborne weather radar
4) Radio Altimeter

Question 19

Define Ducting

Answer 19

A marked temperature inversion plus a rapid decrease in humidity may form a duct within which VHF UHF and SHF wave bands can usually travel long distances

Question 20

Explain low frequency propagation characteristics

Answer 20

Similar to ducting.

Low frequencies will bend around objects and be heard a great distance from the source

Question 21

Low frequencies mean less attenuation.

True or False?

Answer 21

True

Question 22

Higher frequency means greater attenuation, therefore a shorter range.
True or False?

Answer 22

True

Question 23

Where are Radio waves between?

Answer 23

Electric energy and Infrared energy

Question 24

How does antenna shadowing happen?

Answer 24

Due to Earth’s curvature

Question 25

VHF n UHF are kind of sight. Therefore, curvature of the earth and aircraft height limit distances which these can be received.
True or False?

Answer 25

True.