Overview of Low Frequency Communications. (Reannouncement with New AvailabilityInformation)

摘要

Use of Very Low Frequency and Low Frequency (VLF/LF, 3-300 kilohertz)electromagnetic signals for long range underwater communications predates World War H. VLF/LF communications is unique in that transmitted signals are transmitted over extremely long ranges and transmitting antennas are very large. Land-based antennas are typically designed to be supported by towers over 180 meters tall or to span mountain valleys. Airborne antennas typically measure seven kilometers long. Input powers of up to two megawatts provide detectable signals for megameters. The development of this communications system has created and exploited numerous technical advances. Propagation research, material technology, numerical analysis and scale modeling, communications performance evaluation, and modulation advances will be discussed in the context of an overview of this worldwide communications system.... Pseudo Atmospheric Noise Generator(PANG), Real Time Channel Simulator(RTCS), Coverage Prediction Workstation(CPWS).