EAGLE CAD Design files for the VLF Remote Unit
The board is based around a NXP LPC1114 ARM Cortex-M0 microcontroller. A Wolfson WM8737 ADC is used to record the Very Low Frequency (VLF) signals. Although this ADC is intended for audio applications it is perfectly adequate for very low frequency RF signals due to its high gain preamplifiers. It features low power operation and easily available, probably due to it being used in the Microsoft Kinect.
The board has three pads for serial flash and a AT86RF212 868MHz radio. The range is in the order of 200m in free space, but much lower in practice.
The average current draw is approximately 3mA.