[time-nuts] Spectrum Analyzer Specifications

Charles Steinmetz csteinmetz at yandex.com
Wed Mar 23 11:54:29 EDT 2016


Mike wrote:

>Being new to this, I don't actually know what I need to see with it. 
>However, I see charts that show the "spurs" on the output of an 
>oscillator. I assume that I will want to do similar tasks.

>I can measure frequency to a point (7 digits, uncalibrated - 8 once 
>I have a frequency standard).

>I understand that the quality of the OCXOs can vary widely. What 
>tools do I need to determine the quality of output?  I assumed that 
>a spectrum analyzer would be a first step

No, a spectrum analyzer (with much support from ancillary equipment, 
as I said in my last message) is the last step.  Actually, it is 
beyond the last step for all but a very few time-nuts -- mostly ones 
who design precision oscillators.  You are trying to step from 
nowhere near time-nuts capability (7 or 8 digit counter) to 
post-doctoral time-nuts capability.  I believe you would be much 
better served by doing it in steps (and probably leaving out that last step).

First, you need a time interval counter (reciprocal counter) with 12+ 
digits.  With that (and some creativity), you can take series 
(plural) of time-stamped "phase" (time interval) data, which you can 
then analyze (post-process) for phase noise (short-term instability) 
and xDEV (long-term instability).  The list archives are full of 
discussions of exactly these procedures.  The phase noise analyses 
will give you a good picture of how the oscillator will 
multiply.  The TI analyzer will also give you the frequency of your 
oscillator to time-nuts levels of precision.

The usual suspects are the HP 5370A or B, the Stanford Research 
SR620, and the HP 5345A.  There are others, but those three are the 
likely value leaders.

Best regards,

Charles





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