Introduction to high frequency signal system
The high frequency signal system (HF: High Frequency) is a long-distance communication system. It uses electromagnetic waves of the same frequency range as short-wave broadcasts, which utilize the reflection of the ionosphere so that the communication distance can reach thousands of kilometers and is used to maintain contact with the base and remote terminals during flight. The frequency range used is 2 ~ 30MHZ, one channel per 1KHZ. Large aircraft are generally equipped with two sets of high-frequency communication systems that use single-sideband communication, which greatly compresses the occupied frequency band and saves transmission power. The high-frequency communication system is composed of a transceiver unit, an antenna coupler, a control box and an antenna. Its output power is large, and a ventilation and heat dissipation device is required. The high-frequency communication antenna used in modern civil aircraft is generally embedded in the aircraft skin and installed at the tail of the aircraft, but the system is currently rarely used.