4-port, 9kHz to 6GHz eCal module for VNAs
All of the following steps are only required if you plan to use the LibreCAL-GUI. If you plan to control the LibreCAL manually with the buttons, through a script or the LibreVNA-GUI, there is no need to download the LibreCAL-GUI (but you should still install the udev rule on Linux systems).
sudo apt install libqt6widgets6 libqt6charts6 libqt6svg6
wget https://raw.githubusercontent.com/jankae/LibreCAL/main/Software/52-LibreCAL.rules
sudo cp 52-LibreCAL.rules /etc/udev/rules.d
sudo udevadm control --reload-rules
sudo udevadm trigger
cd $UNPACKED_ZIP_FOLDER$
./LibreCAL-GUI
The LibreCAL is just a switch-matrix with additional options to terminate each port into an open, short or 50 Ohm connection:
While the blockdiagram is small and simple, the tricky part of any eCal module is repeatability. The LibreCAL contains an integrated heater and temperature sensor to keep the critical parts at a constant temperature during operation. Furthermore, high quality SMA connectors are used to ensure good return loss.
The coefficients of the calibration standards are stored in standard touchstone format on the device. They must be measured and written once after assembling the PCB and housing.