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What is the radio equipment channel spacing requirement for aircraft operating above FL195 in the ICAO European Region?

  • A
    8.33 kHz
  • B
    8.33 MHz
  • C
    25 MHz
  • D
    25 kHz

The band normally used for Aeronautical Mobile Service (AMS) voice communication is defined between 118.000 and 136.975 MHz, which covers its use for commercial and general aviation, air traffic control and other uses.

The AMS refers to VHF and HF voice communication. The VHF propagation is practically straight-line propagation (similar to light waves). Therefore, the VHF propagation characteristics are ideal for short-distance terrestrial communication. When, due to shadowing (e.g. by a hill), VHF communication is not possible, it is still possible to communicate using the upper part of the HF band where the surface wave is of little use.

Channel spacing in the airband has been 25 kHz. However, increasing congestion has led to further subdivision into 8.33 kHz channels in the ICAO European region - this separation has become mandatory above FL195.

Frequency bandFrequenciesWave bandWave length
VLFVery Low Frequency3-30 kHzVery long100-10 km
LFLow Frequency30-300 kHzLong10-1 km
MFMedium Frequency300-3000 kHzMedium1 km-100 m
HFHigh Frequency3-30 MHzShort100-10 m
VHFVery High Frequency30-300 MHzShort10-1 m
UHFUltra High Frequency300-3000 MHzUltra short1 m-10 cm
SHFSuper High Frequency3-30 GHz (3000-30 000 MHz)Super short10-1 cm
EHFExtremely High Frequency30-300 GHzExtremely short1 cm-1 mm


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