The Use of Raspberry Pi and High Resolution Sound Card for Very Low Frequency Signal Detection

Space weather research is an important aspect in studying and monitoring the effects of extraterrestrial forces outside the earth on human activities. Stanford University under International Space Weather Initiative (ISWI) program has developed first generation of sudden ionospheric detection named as SuperSID. To enable the usage of this system for community outreach space science education program, a portable and low cost system need to be developed. Raspberry Pi can be used as the main processor for the SID system. It can be easily operated without the need of a personal computer. However, the available sound card are limited and sampling rate is on 48 kHz. This limit the detection of the VLF frequency detection to approximately 22 kHz. Thus it become a limiting factor to view the VLF spectrum in a full range (3-30 kHz). To overcome this problem, a VLF receiver system with a better sound card (Audio Injector) was proposed to detect the signal in a full VLF spectrum with the objective for a better data analysis. The hardware aspects including an antenna, a pre-amplifier, a sound card (Audio Injector) and a microprocessor (Raspberry Pi) with LCD Touchscreen as its monitor display. The VLF acquisition software part consists of an acquisition software executable by Python programming language with additional modules that runs in Raspberry Pi. Finally a portable VLF receiver system with maximum sampling rate of 96 kHz has been developed to capture VLF signal between 3-30 kHz.