Mendes, Leonor André Nunes Diogo2026-01-202026-01-202025http://hdl.handle.net/10400.5/116734Tese de Mestrado, Engenharia Física, 2025, Universidade de Lisboa, Faculdade de CiênciasThis dissertation presents the development of a ground-based prototype for monitoring Very Low Frequency (VLF) and Low Frequency (LF) radio signals (specifically in the range of 10 kHz e 100 kHz) to detect ionospheric disturbances associated with solar flares. The system integrates a magnetic loop antenna, a low-noise pre-amplifier with band-pass filtering, a 24-bit analog-to-digital converter (ADC), and a Raspberry Pi processing unit (PU). The circular loop antenna, with a diameter of 0.5 m and 63 turns of copper wire with a diameter of 1.784 mm, was optimized for sensitivity and size. Simulations estimated an inductance of approximately La ≈ 2.39 mH, parasitic capacitance of approximately La ≈ 57.7 pF, and Direct Current (DC) resistance of approximately La ≈ 0.67 Ω. Given that induced signals range from nanovolts to microvolts, a preamplifier with a passband filter cutoff frequencies 8.3 kHz and 190.5 kHz and a gain of 59.2 dB was implemented to reject interference. The PCM1863 audio codec was selected for its 192 kHz sampling rate and 24-bit resolution, allowing up to 96 kHz bandwidth coverage (Nyquist). Integration with the Raspberry Pi required custom I2S and I 2C configuration adjustments. A test with the system fully integrated did not show any peak resembling one from a VLF/LF station. Partial system tests showed peaks near frequencies of known VLF/LF stations, but it was not confirmed if these were transmissions from those sources. For future work, it is suggested to: develop the acquisition software (enabling it to perform datalogging tasks) for fully autonomous operation using the Raspberry Pi - either by creating dedicated software from scratch or adapting existing open-source solutions; adapt the antenna by tuning or improving its sensitivity; create a single PCB solution including the pre-amplifier, ADC and PU and design a power supply solution that allows the system to operate autonomously.application/pdfengSpace WeatherSolar FlareDataloggerVLFMonitoring Systemmaster thesis204176522