[time-nuts] Holding Phase constant

[WarrenS]

Two part question:

I'd like to test the effect of small signal level changes on the phase output of a high resolution linear phase detector at ADEV values below 1e-16 and tau >1000 sec.
I'm looking for suggestions on how I can manually vary the signal amplitude of one of it's 10 MHz sine wave inputs by up to say 3 db with ~0.1 db step size,  while keeping the signal's phase constant in the sub 0.1 picosecond range.

Is there any data available on how much the signal amplitude of a LPRO Rubidium Oscillator or a HP10811 class Oscillator changes over temperature and time when driving an exact constant resistive load?

ws