Vic,
I assume you are matching the hetrodyne of the uBitx BFO plus the WWV carrier
against the audio tone from an AM radio also tuned to WWV.
The tones from WWV flip between 500hz and 600hz each minute, let's go with 500hz.
So you might set the uBitx frequency display to 10.000500 mhz, then adjust?
the calibration variable?si5351bx_vcoa (reloading all three Si5351 oscillators
with each adjustment) until the hetrodyne is exactly the 500hz you hear on the
AM radio.? I'm assuming the uBitx is in LSB mode for this example, with the BFO
500hz above the carrier and not below it.
This need not be stuck with WWV, could use any shortwave carrier of known frequency.
Just set the CW sidetone from the NANO to 500hz for your audio reference,
must be attenuated sufficiently.? Or a 500hz tone from your laptop or smartphone.
Another method would detect the sub-audible beat note out of the demodulator,
perhaps with a DVM.??
Jerry, KE7ER
On Wed, Oct 28, 2020 at 04:54 AM, Vic WA4THR wrote:
Regarding trying to calibrate with WWV, it actually is easier if you have a second AM receiver when WWV is sending tones. You can then match the tone frequency between the uBitX and the AM receiver much easier than when zero beating as you can do that within a few cycles as opposed to losing the low frequency notes perhaps 100's of cycles before zero beat. Note, to be accurate the 2nd receiver needs to be AM, which eliminates that receiver's error which could be added to the perceived tone frequency if using SSB. That is the technique I used on mine and it is dead on frequency.
=Vic=
