This PCB provides an external, thermally separate, TCXO Frequency Reference to the LimeSDR-mini board.
I built this as even though the onboard TCXO is well-specced, being next to the high-power FPGA & RF components was causing noticeable thermal drift, especially in amplitude-modulated (eg. SSB) outdoor use.
This board uses a 40MHz TCXO to be a plug-in replacement with no reconfiguration. A 12-turn potentiometer allows easy manual calibration.