[time-nuts] Ovenaire OCXOs

[WB6BNQ]

Hi Joe,

You should have left the frequency adjustment alone for at least 30 days and more
like 90 days.  On a high quality oscillator it takes at least 30 days minimum for
the package to stabilize.  Otherwise you will just be chasing all the mechanical
stresses, including the crystal itself, that take that long to settle out.
Changing the adjustment causes additional stresses that need time to settle.  It
does not have to be "spot on" frequency to determine the drift and the Adev.
Unless the thing is so far off as to be outside the range of your measurement
process, it would have been better to leave it alone.

Bill....WB6BNQ


Joseph Gray wrote:

> After running overnight, the current draw has stabileized at 160 mA. I
> tweaked the trim pot to set the frequency to 10,000,000.00 Hz, which
> is the resolution of my counter. The counter is synced to the Z3801A.
> The Ovenaire is exposed to ambient air, so I expect things to change
> as the day warms up.
>
> Using an IR thermometer, the OCXO metal can temperature varies a bit,
> but has a hot spot at 37.6 C. I'll have to dig out a contact
> temperature probe for more accurate readings.
>
> Later on, I'll put this thing in an enclosure, which should minimize
> temperature effects. Then I can see where the temperature stabilizes
> from the oven heat. The T.I. comparison will have to wait a few days,
> as I need my laptop for something else tomorrow night.
>
> Joe Gray
> W5JG
>
> On Tue, Apr 12, 2011 at 7:27 AM, John Green <wpxs472 at gmail.com> wrote:
> > Interesting. I have several Ovenaire OCXOs of differing models. I used to
> > think they were pretty stable until I compared them to my Z3801. Compared to
> > a '3801, they stink. But then, a rubidium stinks compared to a 3801. Most
> > have a voltage input for frequency adjustment but one has a trimmer cap for
> > coarse and a pot for fine. Over a period of several days, I would think it
> > had settled down only to come back and find it had suddenly shifted. As they
> > say, stable is a relative term. About all I can say after testing maybe a
> > half dozen from different manufacturers it that the specifications should be
> > taken with a liberal dose of salt. I have seen TCXOs do better than a lot of
> > OCXOs over the limited temperature range of my lab. I have a chamber and
> > keep saying I am going to do some temperature testing but work is always
> > getting in the way.
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