Comm 02: Comm theory radio propagation

Question 1

Radio waves

Answer 1

Radio waves are EM waves

Differentiated from other EM energy by frequency

Question 2

Characteristics of Radio waves

Answer 2

They require no supporting medium

They can penetrate gases, liquids and solids

Question 3

Radio waves propagation

Answer 3

Surface wave
Sky wave
Space wave

Surface wave
     30kHz to 300kHz
     Diffraction
Sky wave
     300kHz to 30MHz
     Refraction
Space wave
     Above 30MHz
     Attenuation

Question 4

Propagation Paths

Answer 4

Ground wave
     Portion of radiated energy which is directly affected by the presence of the earth and its surface features
     2 Components
	 - Surface wave
         - Space wave

Tropospheric Wave Ducting
Part of the radiation that undergoes refraction and reflection in the lower levels of the atmosphere. Caused by abrupt changes in temperature or moisture (or other abrupt discontinuities) that occur in the lower atmosphere.
More pronounced as the frequency of the signal increases and most noticeable in the VHF and lower UHF bands.

Sky wave
Gives reliable comms over very long distances and occurs in the MF and HF frequency bands