It has been a while since I did the calibration of my v5, so please check and record changes as they are made.
1 - You will need a dummy load for the calibration of the stock v5 as it transmits a 10MHz signal in the calibration process.
2 - You need a calibrated receiving device capable of receiving the 10 MHz signal. This can be another receiver that you know to be accurate, or a frequency counter. I used my Icom IC-7300 to calibrate mine. It also worked with an inexpensive frequency counter connected to a short piece of wire.
3 - The process is then to put the uBITX in the calibration mode using the encoder, and adjusting until you have a zero beat on the receiver, or the correct frequency on the frequency counter.
4 - Press the encoder when the frequency is correct, and then power cycle the uBITX to use the new value.
5 - I used a free PC audio spectrum analyzer software with a mic to adjust the BFO. Tune to a clear, static only frequency on the uBITX, and then adjust the BFO until the spectrum is sentered between 500 and 2500 Hz.
I would suggest waiting for one of the experts in this group for more, or better, explanation of the process.