After yesterday's slightly discouraging frequency stability results using on-board 13.5 MHz reference and a SRS DS345 function generator as REFCLK sources, I decided to try it with one of my eBay OCXOs.
OCXO connected to dual power supply. Left voltage is connected to OCXO's Vtune pin.
ADRF6850 evaluation board is connected to HP E4433B signal generator (148 MHz RF source) and one DC-coupled end of the baseband output is connected to the 54624A oscilloscope via a low pass filter (DC coupled).
I first 'tuned' the OCXO by beating it against a 10 MHz frequency generated by the HP E4433B using a MCL ZAD-6 mixer. The OCXO and signal generator were turned on for one hour and then the OCXO was set by carefully adjusting Vtune until no perceptible frequency difference was detected over ten seconds.
The ADRF was set to:
LO = 148 MHz Frequency doubler = on Frequency division = off
The signal generator was then set to 148 MHz and the OCXO connected to the ADRF6850's REFIN reference clock input. Due to rounding errors, 148 MHz can't be set precisely, so the signal generator was adjusted and a stable baseband output was observed for ten seconds at 147.99999996 MHz:
Note that the trace is horizontal. This is very encouraging!