A new system for measurement of low frequency radio transmitting antenna parameters in near real time

A system that can be used to measure several important antenna and tuning system parameters on fixed-site very-low-frequency and low-frequency transmit antennas while the antennas are in normal operation is introduced. The measurements are made by sampling and processing the antenna voltage and current signals to calculate the antenna system resistance, capacitance, inductance, voltage, current, and power, which can be displayed and stored on a personal computer. All of the measurements are made while the antenna is being driven by FSK (frequency shift keying) or MSK (minimum shift keying) signals. A model of a typical low-frequency transmit antenna as well as the associated equations are presented. The response of the antenna system to FSK signals is presented. The algorithms, hardware, and software used by the measurement system, called the VLF/LF antenna monitor system (AMOS), are discussed along with a summary of results obtained during initial testing of the AMOS system.<>