[Test-Equipment] "No spectrum analyzer" phase noise test setup of a 15.6 MHz TCXO?

[Brooke Clarke]

Hi Ray:

The frequency domain measurement of phase noise is fundamentally the same as measuring Allan Deviation.
https://en.wikipedia.org/wiki/Allan_variance
This can be done by dividing down to a 1 Pulse Per Second signal and comparing it to a 1 PPS from a stable oscillator.
The comparison can be made using a counter, or more cost effective one of the microcontroller based time interval counters.
The archives of the Time Nuts mailing list or a Google search should provide a lot of info.
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts

-- 
Have Fun,

Brooke Clarke, N6GCE
http://www.PRC68.com
http://www.end2partygovernment.com/2012Issues.html
http://www.prc68.com/I/DietNutrition.html

Ray, W4BYG wrote:
> The Kenwood TS-590 S (G) list server on yahoo has an interesting discussion going on about the fairly cheap Chinese 
> TXCO's that are being sold as an optional replacement for the factory supplied 15.6 MHz oscillator in the TS-590S(G) 
> series transceivers.  It seems there has been reports of phase noise issues on some Chinese replacements.  This can 
> result in unnecessary and unwanted noise being transmitted or received +/- 10 to 15 KHz from the operating frequency.
>
> I am aware that today's modern procedures would use a fairly expensive spectrum analyzer to measure the phase noise of 
> such an oscillator.  However, most hams today do not have access to a SA, Therefore in true ham fashion (meaning 
> cheap), surely someone knows of an inexpensive way to bench check the phase noise of an oscillator.
>
> Has anyone any experience in doing so?  I surmise building a good 15.6 MHz notch filter would be required.  In 
> addition, a way would be needed to measure 80 to 90+ db down at 10 KHz to 5 KHz away from the fundamental.  Some of us 
> have good HP power meters that have dynamic range of that or a little more.  That would require the notch filter to be 
> very good (not sure one could be made that good even in a good ham lab).
>
> Anyone care to share their insight on what it would take to make such measurements without a SA?
> Your attention is appreciated.
> Ray, W4BYG
>