They operate in the frequency range from 118.0 MHz to 136.975MHz. VHF communication radios are the primary communication radios used in aviation. This includes VHF (30-300MHz), UHF (300MHz-3GHz), and super high frequency (SHF) (3Ghz-30Ghz) radio waves. Most aviation communication and navigational aids operate with space waves. They are only capable of line-of-sight transmission and do not refract off of the ionosphere. Ībove HF transmissions, radio waves are known as space waves. These kinds of radio waves are known as sky waves. The frequency range is between 2 to 25 MHz. As a result, transoceanic aircraft often use HF radios for voice communication. This refraction extends the range of HF signals beyond line-of-sight. HF radio waves bounce off of the ionosphere layer of the atmosphere. This would limit transmissions from the broadcast antenna to receiving antennas only in the line-of-sight of the broadcast antenna except for a unique characteristic. High frequency (HF) radio waves travel in a straight line and do not curve to follow the earth’s surface. Thus, steady radio waves of a frequency determined by the input AC frequency propagate out into space. The process is continuous as long as AC is applied to the antenna. Each new current flow creates new fields around the antenna that force the nottotally-collapsed fields from the previous AC cycle out into space. At any one point along the antenna, voltage and current vary inversely to each other.īecause of the speed of the AC, the electromagnetic fields and electric fields created around the antenna do not have time to completely collapse as the AC cycles. The antenna is half the wavelength of the AC signal received from the generator. Both fields, the magnetic and the electric, fluctuate around the antenna at the same time. An electric field also builds and subsides as the voltage shifts from one end of the antenna to the other. As AC current builds and collapses in the antenna, a magnetic field also builds and collapses around it.
#AIRBUS COCKPIT RADIO COMUNNITCAION GENERATOR#
To transmit radio waves, an AC generator is placed at the midpoint of an antenna.
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