Why is 400 Hz used on aircraft?
One of the reasons why so many airplanes use 400 Hz power is because it allows for a lower weight. Weight is a critical factor in the design of an airplane. If an airplane is too heavy, it may not be able to take off. At the very least, it will require a more powerful engine or engines. In civil and military aviation, however, a frequency of 400Hz is used in aircraft electrical systems. The reason for this is that transformers and motors that are operated at 400Hz can be built much smaller and lighter than those with a mains frequency of 50 or 60 Hz.The main advantage of 400Hz is the more compact design and lower weight of the electrical equipment, which is particularly important in aviation to minimise weight and maximise range per unit of fuel.The FCC allocates frequencies for use by civilians in 47 CFR 87. This table states that both 123. MHz are allocated to station class FAT, which is flight test stations. VHF (Very High Frequency) Radios: Commonly used for short-distance communication with air traffic control (ATC) and other aircraft. These radios typically operate between 118 MHz and 137 MHz.It’s like asking, what is there? MHz is where most dual band and tri-band Ham radios begin their range. MHz would be considered VHF, Very High Frequency, and would include 2-meter ham, MURS, Maritime, as well as some old-school Public Safety and a few commercial bands.On an global level, the ATC allocated frequencies in the VHF band range from 117. MHz to 137. MHz.MHz is the frequency to use when landing at an aerodrome with no published frequency, such as a private strip, or when landing a float plane on a lake. Some aerodromes use 123.