The rubidium should be the most accurate of the bunch, except for the GPSDO. The method I have used is similar to the X-Y lissajous, but I use A, B ch, with B ch trig on a 100+MHz o-scope. Show both traces then adjust A freq source to stop the trace walking, decrease the sweep time down to the nsec. range, adjusting the A freq source for minimum trace walk. The faster sweep time gives you more resolution and allows you to adjust 10 MHz to within .001 Hz. Wait 10-30min. and recheck for A trace movement from the B triggered trace. I have achieved <1E-13 MHz separation from the 10 MHz reference source, using this method.
Don Bitters
