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

[Ron Youvan]

   Hi  Ray, W4BYG:

> 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.

   If you have one of these and two RF test generators that cover it's
frequency, I would feed the two oscillators into channels A and B of a
good scope and set it up for Lissajous display expanding out the
display, set the two for a stationary pattern, then substitute the
"fairly cheap Chinese TXCO" and see if you can see a difference in the
phase of the newly added signal.  If it looks worse than the test
generator you have learned something. If part of the ellipsoid gets
thicker that can be phase noise, and not good under circumstance.
-- 
   Ron  KA4INM - Youvan's corollary:
                 Every action results in unwanted side effects.