EQT 2 Elementart Principles Of Radio Flashcards
What is attenuation
Radio waves reduce in strength over time and distance.
Amplitude decreases. The wavelength and frequency remain unchanged.
How do you overcome attenuation
Use very high frequencies
What are the wave bands between?
Electrical energy (lower end)
Infa red energy (upper end)
What are the frequency bands?
VLF LF MF HF VHF UHF SHF EHF
What is the wavelength spectrum and size for VLF
Spectrum 3-30khz
Wavelength 100km to 10km
What are the frequency spectrum and wavelength size for VHF
30-300mhz
10m to 1m
What are the frequency spectrum and wavelength size for UHF
300mhz - 3ghz
1m to 10cm
What are the characteristics of VLF
Long range
Big aerial and high power
Prone to static
What are the characteristics of LF/MF
Reliable long range
Congested
Static interference/night effect
Used for NDBs
What are the characteristics of HF?
Long distance
Long range comms by day
Static interference
Used for RTF comms
What are the characteristics of VHF/UHF
Line of sight
Free of static interference
Prone to ducting
Used for RTF/ILS/VOR/VDF/PSR/SSR
What are the characteristics of SHF/EHF
Short range
Severe attenuation
Used for RAD/ATC/PAR/Wx RAD
What is a ducted wave?
A marked temperature decrease plus rapid decrease in humidity causes wave to bounce between the surface and top of the duct. This means VHF UHF SHF can travel unusually long distances.
What is an indirect wave
Similar to ducting
Low frequency waves will bend around objects and be herd great distances from the source.
Low frequency means less attenuation
What frequencies use direct wave
VHF and higher
