[time-nuts] Generation of very stable 10.001MHz for heterodyne freq measurement

[Anders Time]

What is the best way to generate a very stable 10.001MHz(low E-13 or
-110dBc/1Hz) to be to do high resolution heterodyne(Allan deviation)
measurements?
Using DDS?
Using PTS 500 or 250 synth and divide? Using HP 8662A and divide?
Some smart pll circuit by locking the 1000Hz to the reference in some way?
Thanks
Anders