[time-nuts] Re: Fixing PN degradation via ADEV measurement

[Karen Tadevosyan]

Hi 

 

Thank you for the clarification and rf-tools link.

 

Agree with your calculation. That’s why I raised this question regarding a fixing PN degradation by Pendulum CNT-91.

 

Could you please explain where is the error in my reasoning of the experiment :

 

*	There is one 10 MHz OCXO with ADEV = 5 mHz
*	There are two boards (DUT1 and DUT2) which multiply 10 MHz OCXO signal by 2.5 using the PLL method
*	DUT1 has 25 MHz output signal with high PN  (checking by air and by measurement of S/N)
*	DUT2 has 25 MHz  output signal with low PN  (checking by air and by measurement of S/N)
Experiment’s steps:
*	Step 1: DUT1 ADEV measuring gives me a value of 60 - 70 mHz instead of the expected 12.5 mHz  (5 mHz x 2.5)
*	Step 2: DUT2 ADEV measuring gives me a value of 10 - 12 mHz which matches the expected 12.5 mHz  (5 mHz x 2.5)
*	Step 3: based on ADEV values which in the first case (DUT1) are much greater than expected and in the second case (DUT2) coincide with the expected I conclude that PN of the output signal from DUT2 will be lower than from DUT1.
I can see this PN degradation using Pendulum CNT-91 only as R&S FSQ8 does not fixate any PN degradation between DUT1 and DUT2

Karen, ra3apw