Radar Principles

Question 1

What is Attenuation?

Answer 1

A radio wave reduces in strength with range or time from the point of transmission

Question 2

What frequency experiences greater attenuation?

Answer 2

The Higher frequency the greater attenuation and
shorter range

Question 3

What is Ducting?

Answer 3

Temperature Inversion
The waves “bounce” between the surface and the top of the duct due to the ratio of wavelength to duct height.

Question 4

What is Attenuation?

Answer 4

Higher frequency, greater attenuation,
shorter range
Attenuation - strength diminishes with increasing distance but wavelength and frequency remain unchanged.

Question 5

VLF

Answer 5

Very Low Frequency
3-30Khz
100km - 10km

Question 6

LF

Answer 6

Low Frequency
30-300KHZ
10km-1km

Question 7

MF

Answer 7

Medium Frequency
300Khz - 3Mhz
1km - 100m

Question 8

HF

Answer 8

High Frequency
3 - 30Mhz
100m - 10m

Question 9

VHF

Answer 9

Very High Frequency
30 - 30 MHz
10m - 1m

Question 10

UHF

Answer 10

Ultra High Frequency
300Mhz - 3Ghz
1m - 10cm

Question 11

SHF

Answer 11

Super High Frequency
3 - 30 GHz
10cm - 1cm

Question 12

EHF

Answer 12

Extremely High Frequency
30 - 300 GHz
1cm - 1mm

Question 13

What is VLF used for?

Answer 13

Long range communications.
Requires immense aerials and high transmitter power.
Very prone to static interference.
Very long range navigation aids.

Question 14

What is LF and MF used for?

Answer 14

Reliable, long range communications.
Requires large aerials and high transmitter power.
Prone to static interference and night effect.
Very congested waveband.
NDB.
Some radio broadcasts

Question 15

What is HF used for?

Answer 15

Long range communications by day and night limited
by diurnal and seasonal variation of the ionosphere.
Requires smaller aerials and transmitter power.
Suffers from static interference and fading.
Optimum operating frequency varies diurnally.
Long distance wireless telegraphy.
RTF communications.

Question 16

What is VHF and UHF used for?

Answer 16

Line of sight communications.
Maximum range dependent upon aircraft height
and aerial height.
Small aerial and transmission power.
Free from static interference and easy to suppress
on aircraft.
Prone to ducting.
Wavebands become congested.
RTF, ILS, VOR, VDF, Surveillance Rada

Question 17

What is SHF and EHF used for?

Answer 17

Short range communications.
Severe attenuation.
Precision, Surveillance and Airborne weather Radar.
Radio altimeter. (ASGMCS)

Question 18

What is an indirect wave?

Answer 18

Low frequency propagation characteristics
Similar to ducting, the low frequencies will bend
around objects and be heard a great distance from the source.
The low frequency means less attenuation .

Question 19

What is a Direct Wave?

Answer 19

Each waveband has different propagation
characteristics.
VHF and higher frequencies propagate on straight paths.
Communication distances limited by the curvature of
the Earth and aircraft height above sea level.
Antenna shadow