Radio Principles Flashcards
What is the name given to the process which reduces the strength of radio waves?
Attenuation
Why does a radio wave reduce in strength (attenuate) with range or time from the point of transmission?
The ever-expanding wave front
The medium resists the wave passage
What happens to a signal that is attenuated?
Its amplitude decreases, but the wavelength and frequency remain unchanged
If the frequency is higher, is there a greater or lesser attenuation and range?
Higher frequency, greater attenuation, shorter range
Which part of the electromagnetic spectrum are radio waves contained in?
Between electrical energy and Infrared Energy
What are the characteristics and uses for the VLF waveband?
Uses
Long range communications
Very long range navigation aids
Characteristics
Requires immense aerials and high transmitter power
Very prone to static interference
What are the characteristics and uses for the LF and MF waveband?
Uses
Reliable, long range communications
NDBs
Some Radio
Characteristics
Requires large aerials and high transmitter power
Prone to static interference and night effect
Very congested waveband
What are the characteristics and uses for the HF waveband?
Uses
Long range communications
RTF Comms
Long distance wireless telegraphy
Characteristics
Smaller aerials and transmitter power
Suffers from static interference and fading
Optimum frequency varies diurnally
What are the characteristics and uses for the VHF and UHF waveband?
Uses
Line of sight communication
RTF, ILS, VOR, VDF, Surveillance Radar
Characteristics
Maximum range dependent upon aircraft and aerial height
Small aerial and transmission power
Free from static
Prone to Ducting
Congested Wavebands
What are the characteristics and uses for the SHF and EHF waveband?
Uses
Short Range Communications
Precision and Surveillance Radar
Airborne weather Radar
Radio Altimeter
Characteristics
Severe attenuation
On what kind of paths do VHF and higher propagate?
On straight paths
What is an issue with VHF and higher straight path propagation
At long ranges, the curvature of the earth could mean the aircraft suffers from antenna shadowing
Describe a Ducted Wave
Where a wave bounces between the top and bottom of a ‘duct’ created by a temperature inversion and humidity reduction and it can travel unusally long distances.
