[time-nuts] second step : I need a clarification

[Bob Camp]

Hi

With the spectrum analyzer you are measuring phase noise. The 10811 is much more quiet than the LPRO for phase noise at 1 Hz. 

Phase noise and short term stability do relate to each other, but the relationship is complex. A range of frequency components all contribute to the short term stability at a specific time interval. 

The simple answer is:

1) The 10811 will give you a much cleaner signal at 10 GHz than the LPRO. 
2) If both are exactly on frequency today, the LPRO will be closer to the correct frequency a month from now than the 10811.
3) Neither one will be exactly on frequency without being set there. 
4) Both will get you close enough to the correct frequency to hear and  tune in a SSB signal and keep you on frequency long enough for a very long QSO with no further tuning. 

Hope that helps.

Bob

On Jan 8, 2010, at 8:44 PM, Dott. Alfredo Rosati wrote:

> this is very clear explanation     /      2E-11 * 10E9 = (2*10)E(-11 + 9) = 20E-2 = 2E-1  = 0.2 Hz_
> 
> thanks very much .
> now the first step is clear .
> 
> assuming a timebase at 10MHz with a short term stability of  2E-11 the 10MHz should be near 10.000.000.000. +/- 2 . ( or better floating  inside +/- 2)
> 
> if this is correct I do not understand why driving my specrum analyzer the result at 10GHz is a residual FM near 2 Hz .
> driving the same analyzer with 10MHz OCXO I do not see residual FM ( or is very little ) The spectrum analyzer is hp 8566b .
> Is there a well know explanation or I I make some mistakes ?
> 
> ( I have plotting result in gif format)
> 
> the ocxo is 10811 , the time base creating residual FM is LPRO-101 .
> 
> regards alfredo i5uxj
> 
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