Andy V. Borisenko
Richard, good afternoon!
note, there are many people here who consider themselves radio engineers. but no one gives you advice on calibration.
I'll try with my bad English to tell you how to properly calibrate.
for this, it is tedious to measure and record the true value of the BFO frequency in the file.
for this you need: a commercial transceiver (I have FT-2000), an Android smartphone and an installed program Audio Frequency Counter ( or any similar), piece of wire.
the transceivers warm up for 30 minutes.
in the commercial transceiver we set 25.000.00 and usb.
Instead of the antenna, we connect a piece of wire and bring it close to the raduino. a commercial transceiver we find a raduino tone. for example: i have 25.003 50. next the smartphone will measure the frequency of AUDIO speaker.
for example: freq in transceiver 25.003.500, audio freq 902 Hz. 25.003.500+902=25.004.402 this is the true frequency BFO you uBitx!!!
this frequency must be written in the firmware file name ubitx_si5351.ino
for example: here are my changes #define SI5351BX_XTAL 25004402 // Crystal freq in Hz
this should be done with the help of the program arduino ide.
how to do it (and it's very simple) let him tell someone from the engineers who speak English better than me.
After that, the tuning and calibration of the transceiver will take several minutes.