[time-nuts] Cross-Correlation Results

Azelio Boriani azelio.boriani at screen.it
Sat Aug 4 19:31:40 EDT 2012


In your opinion, how the Wenzel company got the data for the ULN
specifications?

On Sat, Aug 4, 2012 at 11:02 PM, Bruce Griffiths <bruce.griffiths at xtra.co.nz
> wrote:

> John Ackermann N8UR wrote:
>
>> Magnus inspired me to try my own cross-correlation experiment with the
>> TimePod today.  I used two fairly normal OCXO frequency standards as the
>> reference, and a Wenzel 5 MHz ULN as the device under test.
>>
>> By doing single-reference measurements of each OCXO versus the ULN, I was
>> able to plot their noise.  Since the ULN has performance near the noise
>> floor of the TimePod, I could then test how well the correlation works to
>> allow measurements below the noise of either reference.
>>
>> Conclusion: it works *really* well.  Plots and a little write-up are at:
>> http://www.febo.com/pages/cross-correlation/index.html
>>
>> John
>>
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>>  Even a pair of Trimble 34310T ocxos appear to work well as the dual
> reference oscillators.
>
> If one could use a pair of ocxos to drive the other pair of ADCs it should
> be possible to evaluate the contribution of the Timepod itself to the noise
> floor.
>
> Using an interferometric technique with a Timepod allows a PN noise floor
> of -200dBc/Hz or less to be achieved (with a test source noise floor of
> around -175dBc/Hz or worse) when measuring the additive PN of components
> such as amplifiers.
>
> Bruce
>
>
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