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Ground controllers heavily rely on four different types of frequency bands to maintain contact with aircraft. These include: high frequency, very high frequency, ultra high frequency, and satellite communications. Each frequency is special in their own way in that they are different in regards to frequency bandwidth and transmission range.
High Frequency (HF)
HF radios are primarily used for short range ground-to-ground radio communications. Although this form of communication is rare, it has still proven to be helpful. While an aircraft is awaiting take off on the runway, it can be used to gather last minute information from another ground unit, or as a back up form of communication.
The HF radio frequencies are approximately 3-30 MHz.
The HF radio frequencies are approximately 3-30 MHz.
Very High Frequency (VHF)
VHF radios are the primary form of communication for Air Traffic Controllers within a short rang. You may be more familiar with this form of communication if you've ever been to an airport. The controllers in the towers utilize VHF to take off and land aircraft from the runway within a specific distance of the airfield. A known issue with VHF radios is the line-of-sight propagation. Weather and mountainous terrain are known to interrupt the line-of-sight, thus inhibiting aircraft to receive radio transmissions.
The VHF radio frequencies are approximately 30-300 MHz.
The VHF radio frequencies are approximately 30-300 MHz.
Ultra High Frequency (UHF)
UHF radios are prevalent in today's military operations in order to maintain two way communication with aircraft. Usually these aircraft are at higher altitudes, hundreds of miles away from the nearest airfield, and are too far away to utilize VHF radios. Much like VHF, UHF radios also have line-of-sight propagation and cannot reach past the horizon which limits the range of the radio.
The UHF radio frequencies are approximately 300 MHz - 3 GHz.
The UHF radio frequencies are approximately 300 MHz - 3 GHz.
Satellite Communications (SATCOM)
SATCOM radios can be a blessing, or a curse when it comes to aircraft communications. Because the frequency is traveling from the ground to the satellite and back to the aircraft, it is no surprise that problems arise. The main issues include problems with satellite outages, inconsistent data link relay from the ground to the satellite, and the overall global positioning of the satellite for clear communication. Aircraft are also required to to have SATCOM radios in order to establish two-way communication. When everything falls into place, SATCOM is the best form of communication.