The ultrashort wave communication system is composed of terminal stations and relay stations. The terminal station is equipped with a transmitter, receiver, carrier terminal and antenna. Relay stations only have transmitters and receivers in two directions and corresponding antennas.

1. Transmitter. The indirect frequency modulation method is generally used, that is, the method of obtaining frequency modulation by using phase modulation. In this way, a crystal oscillator with a high frequency stability can be used as the main oscillator without having to use a complicated frequency control system. However, in order to reduce the parasitic amplitude modulation and nonlinear distortion, the modulation coefficient should not be too large and generally less than radians. Therefore, a multi-stage frequency doubler is used in this transmitter to obtain the required frequency offset, thereby increasing the sideband power of the transmission frequency. The last stage of the transmitter uses a Class C power amplifier, which has high efficiency. In the ultra-short wave frequency band, concentrated parameter components can be used to form a tuning loop, and the high-frequency side can be used with microstrip components.

2. Receiver. It is generally a typical FM superheterodyne receiver. It is mainly composed of high frequency amplification, local oscillation, frequency conversion one or two times, intermediate frequency amplification, limiting, frequency discrimination and baseband amplification. There are many extraneous interferences in the ultra-short wave band. It is necessary to add a spiral filter at the input end of the receiver and an input band-pass filter at the intermediate amplifier stage to suppress the interference. The frequency-modulated signal after the mid-amplifier, through the limiter, can cut off the mixed pulse interference or parasitic amplitude-modulated wave to improve the signal-to-noise ratio, and then use the discriminator to recover the original baseband signal, amplify it, and then use the carrier The terminal is shunted out to the user.

3. Carrier terminal. The old line baseband signal of the ultra-short wave transmitter and the ultra-short wave receiver is split and merged into a multi-channel second-line voice signal, which is connected to the user or the equipment connected to the local exchange. The carrier terminal is only installed in the ultra-short wave terminal station.

4. Antenna. Due to the short wavelength of ultrashort waves, three-unit or five-unit Yagi antennas with simple structure, high gain and good direction are generally used. At the high frequency end close to the microwave section, angular reflector antennas are also used.