Adaptive signal processing in the coastal harbor radio-telephone system

This paper describes a method by which land-based receivers in the Coastal Harbor radiotelephone system can reliably detect and process A3A signals in the two-to-three megahertz frequency range. It has been shown [1] that the noise and signal characteristics in the system are nonstationary. The land receivers must reliably detect an A3A carrier in a noise environment that varies from a low of 40 dB above thermal for quiet locations, like Boston at midday in winter, to a high of 90 dB above thermal like New Orleans at midnight in summer. An FM noise quieting approach is employed for detection of the A3A carrier. The approach is adaptive in that the receiver will only be activated if sufficient carrier is present to overcome the noise at the time of detection.