A method of passive real time frequency selection based on HF interference centroid frequency

A method of HF passive RTFS (real time frequency selection) is presented which needs no transmitter. It can work independently at a receiving terminal. The equipment required consists of just a receiver controlled by a microcomputer and an antenna shared with the communication system. It can evaluate the MUF of the HF link and then select the unoccupied frequencies around 0.85 MUF as working frequencies