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

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