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What is the frequency band, and the spacing between allocated frequencies, used for voice communications by the Aeronautical Mobile Service?
  • A
    VHF, 8.33 MHz spacing.
  • B
    HF, 25 kHz spacing.
  • C
    HF, 8.33 kHz spacing.
  • D
    VHF, 8.33 kHz spacing.

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

8.33 kHz Frequency and Channel Display Table

Operating Frequency (MHz)Channel SpacingDisplayed and Transmitted
118.00008.33118.005
118.00838.33118.010
118.01678.33118.015
118.02508.33118.030
118.03338.33118.035
118.04178.33118.040
118.05008.33118.055
118.05838.33118.060
118.06678.33118.065
118.07508.33118.080
118.08338.33118.085
118.09178.33118.090
118.10008.33118.105

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