I received a tinyPFA from R&L and am struggling to figure out how to use it. The documentation has a long way to go.
I currently have a Bodnar 2 output GPSDO feeding the A input of my 5386A running on its internal OXCO and feeding the A port on the tinyPFA. The difference frequency shown on the tinyPFA is bouncing around at a few mHz, roughly +/- 0.005 ppb which is a long way from my goal. The 5386A shows the same jitter in the last digit.
I stuck my DSO on the power supplying both the GPSDO and the CTI OXCO and took the attached screen dumps. One running and one singleshot.
The lab PSU is an Instek GPE 4323 linear supply. For general use it is excellent and I've been quite happy with it. However, the noise on the supply shows the difficulty I am facing. It is much too dirty to feed the OXCO in either oscillator even though both have internal voltage regulation. I am getting a roughly factor of 200 noise reduction, but I need to make that noise unmeasurable at 1 mV/div. I suspect that the 15 MHz ripple is actually noise pickup from the absolute crap SMPS in the Instek MSO2204EA. I have a Tek 2465B in transit which I shall be using as my primary bench scope in the future until I have the time and inclination to shield the Instek and other DSO SMPSes.
For the benefit of those who have not examined the PS problem I should like to suggest considering the following:
USA 120 mains are +/- 5% (114-126 Vrms, nominal 118 Vrms). Then consider the +/- 5% variation of an LM317 to supply variation. Followed by a 2nd LM317 feeding an LM399 supplying both the 5V CTI power and the Vctl pin divider. For simplicity assume that both LM317s are using an AD584JH voltage reference instead of the output of the LM317 for their reference voltages with a several Farad cap to stabilize the AD584JH feed to the voltage dividers.
Once I have had time to complete a <1 uVrms mean noise level PSU I'll write up a detailed error analysis with full documentation.
Have Fun!
Reg
