Dear KennyG
I follow your experiment to use single tone mode, the spurs. Level is the same as in quadrature mode.
In my experiment about lower clock harmonic spurs., I found the harmonic of the VCXO input signal affect the spur. a lot. When I lower the clock Vpp and filter the input clock to become a sine wave, the relative RF output spur. will be lower.
Thank you for the your experiment and suggestions, you give me an important reference.
Best Regards,
Yung-nien Chiu