The main objective of the current work is to develop a Very Low Frequency (VLF) monitoring system for characterizing low layer ionosphere. Low layer ionosphere is important for communication, and some researchers stressed that lower layer ionosphere can be a precursor to earthquake event. The VLF monitoring system composed of a 1-m antenna, a preamplifier to amplify the signal, an ADC converter and a data acquisition system. The optimization of 1-m antenna received dual frequencies 19.2 kHz and 19.8 kHz from South Vijayanarayanam, India and North West Cape, Australia, respectively. Subsequently, a low pass filter was designed in the preamplifier to pass VLF signals from 0-30 kHz. The results revealed that the system was able to characterize diurnal variation: sunrise and sunset and detect changes in the lower layer ionosphere region due to Solar activity.
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