[time-nuts] Z380XA The saga of the aging 10811

[Bob Benward]

In a few weeks I will be posting another plot.  After the EFC slope drift
reversal from positive to negative, it is now starting to flatten again and
it looks like it will be again reversing and going positive again.  Starting
to look sinusoidal.

Bob


>>> -----Original Message-----
>>> From: time-nuts [mailto:time-nuts-bounces at febo.com] On Behalf Of James
>>> Flynn
>>> Sent: Friday, September 25, 2015 10:40 AM
>>> To: time-nuts at febo.com
>>> Subject: Re: [time-nuts] Z380XA The saga of the aging 10811
>>> 
>>> Bob Benward <rbenward at ...> writes:
>>> 
>>> >
>>> > Continuing this discussion, I have included a PDF showing the past
>>> 30days of
>>> > EFC.  Amazingly, the drift has reversed direction!  Anyone have any
>>> insights
>>> > into this behavior?  Each data point represents 10 seconds.
>>> >
>>> 
>>> I have found that three things can cause this behavior over a short term
>>> (days) which do not involve failure of the standard itself ( in no
particular
>>> order ):
>>> 
>>> 1) Power supply. Most standards are immune to this but, if your EFC
circuit or
>>> phase detector involves active circuits, it can show up.
>>> 
>>> 2) Grounds. Bad grounds or ground loops, especially those that share
current
>>> with the oven heater can cause unexplained drift. However, these usually
>>> have a diurnal temperature signature unless your set up is very climate
>>> controlled. Screw terminal grounds or connections can "age" and change
>>> things. Best to ahve everything soldered.
>>> 
>>> 3) Cheap components, especially resistors. I recently had this driving
me nuts.
>>> Carbon comp. and the 2 cent metal film resistors have large temperature
>>> coefficients and are even sensitive to humidity. Go for the <10ppm / deg
C
>>> metal film or SMD resistors. Some caps also can be tricky if the circuit
>>> involves large caps.  Leakage is a problem in high impedance circuits
and can
>>> be unpredictable and non-constant.
>>> 
>>> Finally, there is literature that supports resonators can reverse their
ageing
>>> slope. However, this is rare.
>>> 
>>> I hope this helps.  I have been there, scratching my head while the
system
>>> seems to have a mind of its own.
>>> 
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