A Frequency Stepping Scheme for Overcoming the Disastrous Effects of Multipath Distortion on High-Frequency FSK Communication Circuits

By changing frequency a small amount after transmission of each signaling element in FSK transmission, it is possible to avoid the mutual interference of the main and multipath propagated signal in a high-frequency communications system. Thus, it is practical to employ four-channel time division multiplex systems under multipath conditions that would otherwise render them useless. This paper describes an experimental system that was produced by modifying conventional FS keyers and employing standard communications receivers in conjunction with appropriate frequency stepping means and selective filters. Operational performance data on experimental circuits will be discussed.