[time-nuts] Quartz crystal aging -- unlocked Z3801A

[Louis Taber]

Hi All,  My first note to the mailing list.

I never thought I would be able to do see a quartz crystal age.  All
earlier attempts were buried in the noise & temperature effects.  This data
set results in a very straight line.

This study tracks the 10MHz output of a Z3801A GPS with a Agilent 53310A
Modulation Domain Analyzer with its reference input connected to an
FEI-Zyfer Nano Sync II GPSDO.
The Z3801A GPS receiver has no antenna attached.  It is NOT locked to the
GPS satellites.  My suspicion is the the receiver's physical location is
locked.

I believe the  Z3801A GPS receiver has one of the best SC double oven
quartz crystal based oscillator ever manufactured.  Perhaps some day it
will also receive!

For the majority of my data set I have been recording frequency averages
once a day.  Each data point represents over 40,000 frequency
measurements.  The total number of frequency measurements exceeds 2 million
after February 22, 2020.  February 22 is when I started daily
measurements.  There is almost a month of additional points not shown in
the graphs.

>From February 20 to April 6, 2020 the frequency of the unlocked Z3801A has
aged from 10,000,000.006,069,6 to 10,000,000.008,649,7 or 2.5801mHz over
46.7 days or 56.4nHz/Day.  If my calculations are correct that is a
Δf/f/day of 4.5e-12/day.  Which extrapolates to 20 mHz/year.

A section of my spreadsheet that might not make it to the mailing list.
The spreadsheet is attached exported from Google Docs to Microsoft .xlxs
format.

Days μHz/Day mHz/year years/Hz Δf/f/day ppm/year n
Averages 1.02 58.16 21.24 39.79 5.8 0.0021 45736
x 10e-12
Total 32.67 1463560
My biggest conclusion is the HP did a GREAT job designing the double oven
crystal oscillator!

Also attached is a picture of the display of the Agilent 53310A Modulation
Domain Analyzer after a day of creating a histogram.

John R. Vig has published several different versions of *QUARTZ CRYSTAL
RESONATORS AND OSCILLATORS *over the years.  This is the latest one I am
aware of:  http://beckelec.com/john-vig-crystal-tutorial.pdf  They are
different.  Another one is at:
https://www.am1.us/wp-content/uploads/Documents/U11625_VIG-TUTORIAL.pdf He
poits out in one that SC crystals are "on the order of 1 million atomic
layers thick".  Loose an atomic layer of quartz and there goes 1 ppm?
There is often gold layers for the electrical connection, right where I
believe the maximum acceleration is.  About 1 million Gs.  Another totally
rhetorical question, "How many gold molecules need to be dislodged to shift
the frequency 1 per part in 10e-12? <grin>".

Some more serious questions.

How many significant digits am I getting after measuring/averaging
40,000-60,000  sample?
Why do my histograms have a long thin tail to the higher frequencies (in a
4 mHz window)?
What i causing the double peak in the histograms?

An LSB in the FEI-Zyfer Nano Sync II DAC driving the VC XO?

An instability in the 53310A Modulation Analyzer's PLL?

Also attached is the graph of the oscillators drift with an offset of
10,000,000 Hz removed.  The vertical axis is in mHz.  You really need to
watch the case of the "M"s!

Louis Taber, AF7XZ

PS: Another use of the Agilent 53310A can be seen on the Wikipedia WSPR
page at
https://en.wikipedia.org/wiki/WSPR_(amateur_radio_software)#/media/File:4-FSK_used_for_WSPR.jpg
-------------- next part --------------
A non-text attachment was scrubbed...
Name: Counter%20 Agilent 53310A.xlsx
Type: application/vnd.openxmlformats-officedocument.spreadsheetml.sheet
Size: 47302 bytes
Desc: not available
URL: <http://febo.com/pipermail/time-nuts_lists.febo.com/attachments/20200406/71732080/attachment.xlsx>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: IMG_2723a.JPG
Type: image/jpeg
Size: 170189 bytes
Desc: not available
URL: <http://febo.com/pipermail/time-nuts_lists.febo.com/attachments/20200406/71732080/attachment.jpe>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: freq.jpg
Type: image/jpeg
Size: 34664 bytes
Desc: not available
URL: <http://febo.com/pipermail/time-nuts_lists.febo.com/attachments/20200406/71732080/attachment.jpg>