[time-nuts] OCXO and Aging

Bob Camp lists at rtty.us
Wed Sep 14 16:25:22 UTC 2011


Hi

OCXO's are heated gizmos when in use. If you keep them on power constantly,
you are more likely to get a reasonable aging trend. When they are power
off, some (but not all) of the things that "age" will "un-age". I have seen
some that take as long as 60 days to come back to "normal" after being power
off for quite a while. 

----------------------------

Dewar flask OCXO's have always been high cost items. Piece wise they
represent << 0.01% of the OCXO's sold over the last 15 years. They were more
common in the 1960's, but high cost even then.

The scrap stuff you are seeing out of China is mostly from 5 to 10 year old
mass produced gear. You kind of have a 1 in 10,000 chance of seeing an eBay
ad for one, just based on initial volume.

Next factor would be the higher value of the gear they went into. Fancy high
cost stuff is more likely to be sold as a unit rather than scrapped out.
Weather that adds another 10:1 or some other factor, I have no idea. 

Working in your favor is that they are a cool high cost item and are less
likely to be just tossed out. Again, how that factors in - no idea. 

Bob

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of Paul A. Cianciolo
Sent: Wednesday, September 14, 2011 11:15 AM
To: xformer at citynet.net; 'Discussion of precise time and frequency
measurement'
Subject: Re: [time-nuts] OCXO and Aging

Will,

Yes.. I see the point you are making.  So aging is a function of all the
components in the oscillator, not just the crystal.
I am just now trying to get a "feel" for what to expect from different OCXO
that I have running.
Also how long to have them running before any type of meaningful comparisons
can be made. 

Thank you Will,


Paul A. Cianciolo
W1VLF
http://www.rescueelectronics.com/

"Time is relative"  Abert Einstien circa 1950
"Relatives use up all my time"  Lisa Cianciolo circa 1983




-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of Will Matney
Sent: Wednesday, September 14, 2011 9:23 AM
To: 'Discussion of precise time and frequency measurement'
Subject: Re: [time-nuts] OCXO and Aging

Paul,

The info they show is generally from the manual or paperwork that comes with
the OCXO when new.

If they are used OCXO's, then they will be more stable over time than a new
one, off the shelf, as far as drift, or they should be. The OCXO acts
similar to any heated device, and resistors function similar to this also.
When first used, they will drift from spec more than they do after they have
ran for so long in time. The factory generally does a burn in to stabilize
them, but it still takes some time after that to completely settle down to
where calibration isn't needed as often. There's generally a curve for each
model that will show the drift over time.

The main thing in using these, even though they're supposed to be insulated,
is to mount them where temperature fluctuations are minimal. Also, some are
better insulated than others, like the HP units, which are encased in foam
inside a can.

A case in point is the action of artifact resistance standards. These are
the oil filled, and similar to the Leeds & Northrup type. After use for a
long time, the need for calibration, which is really just re-measuring the
value, can be as high as 5 to 10 years, but when new, they should be checked
every one to two years for drift.

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com]On
Behalf Of Paul A. Cianciolo
Sent: Wednesday, September 14, 2011 9:01 AM
To: 'Discussion of precise time and frequency measurement'
Subject: [time-nuts] OCXO and Aging


I have been looking at all of these OCXO's for sale on EBAY.  Most seem to
be coming out of China.
It as if they are scrapping lots of equipment and pulling out the
oscillators.

There are lots of data attached to these auctions.  It seems that for an
OCXO the rate of aging changes with the period of time it has been running.
Typically I see  aging given in "after  continuous operation"  intervals of
30, 60, 90 days with a rate decreases as the period of time increases.

So the questions:

Is this a onetime 30,60,90 day burn in ? Or does this same information apply
to an oscillator that's been on the shelf(or in China waiting to  be sold)
for say 6 months ?

Does aging ever stop?   Does it decrease at a slower rate?

A lot of the oscillators on EBAY you can see the date codes. If there was a
certain model of high quality, all else being equalize would you buy the
oldest unit that might have the most hours on it?

I have a Rakon Double Oven OCXO right now but there seems to be a few made
by Oscilloquartz that look pretty good.

However I don't see any OCXO's that use a Dewar like the FTS unit I had...
Do they show up from time to time?

Thank you


Paul A. Cianciolo
W1VLF
http://www.rescueelectronics.com/

"Time is relative"  Abert Einstien circa 1950 "Relatives use up all my time"
Lisa Cianciolo circa 1983





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