The analysis and optimization of a solar powered VLF receiver system, located within a noisy environment, is presented. The improved system is built on a previous design which makes use of a single loop magnetic field antenna to sample VLF signals in the frequency range of 100 Hz to 100 kHz. The original device suffered from noise pollution and malfunctioning circuitry. Unwanted noise and aliasing were reduced by increasing the filter roll-off and by using a narrower passband of 500 Hz to 47 kHz. A variable gain control mechanism is included to eliminate frequency harmonics caused by protective clipping of higher input voltages. Experimental results into the antenna types, indicate that the existing larger loop antenna may have a slight advantage over a whip antenna and smaller loop antennas in terms of gain. The system still suffers from noise pollution due to the urban environment, but produces spectrograms and audio files with less unwanted noise. A power monitoring device was designed and constructed to measure the power consumption of the receiver system. The receiver consumes minimal power at 9.5 W and the power supply should not be a limiting factor for long term usage of the device off the power grid.
Student names:
Zaid Khan and Sello Molele
Supervisor name:
Prof Ken Nixon
Post time: Feb-18-2017